New fossils of Australopithecus anamensis from Kanapoi, West

Transcription

Journal of Human Evolution 65 (2013) 501e524
Contents lists available at SciVerse ScienceDirect
Journal of Human Evolution
journal homepage: www.elsevier.com/locate/jhevol
New fossils of Australopithecus anamensis from Kanapoi, West
Turkana, Kenya (2003e2008)
C.V. Ward a, *, F.K. Manthi b, J.M. Plavcan c
a
Department of Pathology and Anatomical Sciences, M263 Medical Sciences Building, University of Missouri, Columbia, MO 65212, USA
Department of Earth Sciences, National Museums of Kenya, P.O. Box 40658, Nairobi, Kenya
c
Department of Anthropology, 330 Old Main, University of Arkansas, Fayetteville, AR 72701, USA
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 January 2013
Accepted 7 May 2013
Available online 30 August 2013
Renewed fieldwork from 2003 through 2008 at the Australopithecus anamensis type-site of Kanapoi,
Kenya, yielded nine new fossils attributable to this species. These fossils all date to between 4.195 and
4.108 million years ago. Most were recovered from the lower fluvial sequence at the site, with one from
the lacustrine sequence deltaic sands that overlie the lower fluvial deposits but are still below the
Kanapoi Tuff. The new specimens include a partial edentulous mandible, partial maxillary dentition, two
partial mandibular dentitions, and five isolated teeth. The new Kanapoi hominin fossils increase the
sample known from the earliest Australopithecus, and provide new insights into morphology within this
taxon. They support the distinctiveness of the early A. anamensis fossils relative to earlier hominins and
to the later Australopithecus afarensis. The new fossils do not appreciably extend the range of observed
variation in A. anamensis from Kanapoi, with the exception of some slightly larger molars, and a canine
tooth root that is the largest in the hominin fossil record. All of the Kanapoi hominins share a distinctive
morphology of the canineepremolar complex, typical early hominin low canine crowns but with
mesiodistally longer honing teeth than seen in A. afarensis, and large, probably dimorphic, canine tooth
roots. The new Kanapoi specimens support the observation that canine crown height, morphology, root
size and dimorphism were not altered from a primitive ape-like condition as part of a single event in
human evolution, and that there may have been an adaptive difference in canine function between
A. anamensis and A. afarensis.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Australopithecus anamensis
Kanapoi
New fossils
Dentition
Introduction
From 2003 to 2008, a field team from the National Museums of
Kenya led by one of us (FKM) recovered several new hominin
fossils from Kanapoi, Kenya. These specimens are attributed to
Australopithecus anamensis, because not only is this the only
hominin known from Kanapoi, but their morphology matches
previously described Kanapoi A. anamensis fossils (Leakey et al.,
1998; Ward et al., 1999a, 2001). The new fossils presented here
include three associated partial dentitions and several isolated
teeth. They expand the hypodigm of A. anamensis and provide an
opportunity to evaluate the variation and dental morphology and
proportions within this taxon. The new fossils include the largest
canine tooth root currently known in the hominin fossil record.
* Corresponding author.
E-mail address: [email protected] (C.V. Ward).
0047-2484/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jhevol.2013.05.006
Australopithecus anamensis was originally announced in 1995 by
Leakey et al. based on fossils from Kanapoi, and additional specimens were described subsequently (Leakey et al., 1998; Ward et al.,
1999a, 2001). Kanapoi is the type-site for A. anamensis, and has
yielded the majority of the fossils attributed to this species (n ¼ 69
including the new specimens presented here). The published
Kanapoi A. anamensis sample includes three mandibles, a partial
temporal bone, a maxilla, at least eight associated partial juvenile
and adult dentitions, more than 20 isolated teeth, a partial humerus, manual phalanx, capitate and tibia (Ward et al., 2001). In
addition, Kanapoi has yielded more than 3800 other micro- and
macrofaunal specimens (Harris et al., 2003; Winkler, 2003; Manthi,
2006, 2008).
The A. anamensis hypodigm as originally described also includes
slightly younger specimens from Allia Bay, Kenya (3.9 Ma [millions
of years ago]), including a nearly complete radius, as well as some
maxillary fragments and isolated teeth (Heinrich, 1993; Coffing
et al., 1994; Ward et al., 1999a, 2001). Thirty additional
A. anamensis fossils were announced more recently from the
502
C.V. Ward et al. / Journal of Human Evolution 65 (2013) 501e524
Ethiopian site of Asa Issie (4.12 Ma, White et al., 2006), including a
partial maxilla, two associated dentitions, mandible fragment,
isolated teeth, plus a partial metatarsal, eroded distal pedal phalanx, manual phalanx, four vertebral fossils and partial femur. Most
of these postcranial fossils have not yet been figured or described. A
partial heavily worn dentition and isolated lower fourth premolar
from Fejej, Ethiopia (Fleagle et al., 1991) is dated from about 4.1
(4.2e3.7) Ma and in preserved morphology more closely resembles
those of A. anamensis than any other species (see Ward et al., 2010;
Manthi et al., 2012, also discussions in; Delson et al., 2000; White,
2002; MacLatchy et al., 2010; Wood and Leakey, 2012). Hominins
from the 3.76e3.72 Ma site of Woranso-Mille, Ethiopia (Deino et al.,
2010) have also provisionally been attributed to A. anamensis
(Haile-Selassie, 2010; Haile-Selassie et al., 2010).
Kanapoi is the earliest occurrence of A. anamensis, making the
Kanapoi hominins the earliest Australopithecus. The sediments at
Kanapoi were initially dated radiometrically to between 4.17 and
4.07 Ma (Leakey et al., 1995; Feibel, 2003; Leakey and Walker, 2003)
but were revised to between 4.195 and 4.108 Ma (McDougall and
Brown, 2008). With only one exception (mandible KNM-KP
29287) (Leakey et al., 1998; Ward et al., 2001), most published
Kanapoi hominin fossils date to the earliest part of this sequence
(McDougall and Brown, 2008).
Australopithecus anamensis predates Australopithecus afarensis
by 600,000 years. Australopithecus afarensis is known from fossils
dated to as early as 3.6 Ma, but is well known only starting at 3.4 Ma
(for comprehensive review see Kimbel and Delezene, 2009). It
appears likely that A. anamensis represents the ancestor to
A. afarensis, and that these species represent portions of an anagenic lineage (Kimbel et al., 2006); see also (Haile-Selassie, 2010;
Haile-Selassie et al., 2010). Australopithecus anamensis site samples are morphologically continuous with those of A. afarensis from
Laetoli (3.6 Ma), Maka (3.4 Ma) (White et al., 1993), and Hadar (3.4e
3.0 Ma) (Leakey et al., 1995; Wolpoff, 1999; Ward et al., 1999a, 2001;
White, 2002; Kimbel et al., 2006; White et al., 2006, 2009; HaileSelassie, 2010; Haile-Selassie et al., 2010). Because these samples
are most parsimoniously interpreted as a single evolving lineage, it
could be argued that A. anamensis be subsumed into the A. afarensis
hypodigm (see discussions in Kimbel et al., 2006; Haile-Selassie
et al., 2010). However, for pragmatic reasons we retain both species names to simplify discussion and provide a basis for comparison of fossils from different sites, and because A. anamensis is
morphologically and perhaps adaptively distinct, especially in the
earliest time periods (see also Leakey et al., 1995; Ward et al., 1999a,
2001; Grine et al., 2006; Kimbel et al., 2006; White et al., 2006;
Haile-Selassie, 2010; Ward et al., 2010; Manthi et al., 2012).
In fact, although A. anamensis shares with A. afarensis the overall
bauplan of Australopithecus, these species differ in many characters
for which both species are known. Despite being known from
several sites in two countries, A. anamensis remains “woefully underrepresented” (White et al., 2009: 84) in the fossil record, so that
the extent of the similarities and differences between these species
remain poorly understood. Thus, the new fossils are of particular
significance in understanding the origins and early evolution of
Australopithecus.
Little is known about the postcranial morphology of
A. anamensis, although it appears to have been fully bipedal. The
Asa Issie femur is described as equivalent to those attributed to
A. afarensis (White et al., 2006), as is the Kanapoi tibia that bears the
orthogonal shank characteristic of all hominins (Latimer et al.,
1987; Ward et al., 1999a; DeSilva, 2009), differing from the somewhat verus shank of Ardipithecus ramidus (Lovejoy et al., 2009a)
and that of apes. There may be some differences in upper limb
morphology, however, that may hint at differences in locomotor
and/or manipulatory function. While the Allia Bay radius and
Kanapoi humerus and phalanx are long and curved like those of
A. afarensis (Heinrich, 1993; Lague and Jungers, 1996; Ward et al.,
2001; Patel, 2005), a middle phalanx from Asa Issie is described
as being longer than those from Hadar (White et al., 2006), and the
Kanapoi capitate has laterally-facing facets for MC2 as in extant
African apes, unlike in Proconsul, Ardipithecus and all other hominins (Leakey et al., 1998; Lovejoy et al., 2009b; Macho et al., 2010,
and see; McHenry, 1983; Beard et al., 1986; Ward et al., 1999b).
Available data about forelimb morphology in A. anamensis are
minimal, and at present, it appears that upright bipedal locomotion
was indeed associated with the origins of Australopithecus, even
pending the potential differences between A. anamensis and
A. afarensis in the upper limb.
Unlike the postcrania, the jaws and teeth of A. anamensis and
A. afarensis are well enough known to enable significant comparisons. Like A. afarensis, Australopithecus anamensis had larger,
thicker-enameled, low-crowned molars than those of African apes
or Ardipithecus (Suwa et al., 2009a,b; Ward et al., 2001; see also
Ungar, 2004 for discussion of molar morphology and masticatory
abilities), likely signaling the ability to process harder foods than
these earlier hominins (Grine et al., 2012). This may have opened up
wider ecological niches for australopiths, possibly related to
exploiting more open habitats, which may in turn be related to the
origins of the genus (White et al., 2000). Australopithecus afarensis
appears to have been further specialized for increased masticatory
strength with taller molar crowns and a more robust mandibular
symphysis (Leakey et al., 1995; Ward et al., 1999a, 2001; Teaford
and Ungar, 2000; Macho et al., 2005). Australopithecus afarensis
also tends to have more posteriorly divergent toothrows than does
A. anamensis, extant apes and Ardipithecus (Puech, 1986; Puech
et al., 1986; Ward et al., 2001; Suwa et al., 2009a,b) that could
potentially decrease symphyseal stresses during mastication
(Hylander, 1984, 1985; Ravosa, 2000). It is notable then, that symphyseal robusticity is greater in A. afarensis than A. anamensis,
despite its more divergent toothrows. Overall, dentognathic
morphology would suggest that heavier mastication compared
with earlier apes did characterize the origin of Australopithecus (see
also Macho et al., 2005) but that this adaptation continued to be
developed throughout the evolution of A. afarensis.
Despite the apparent morphological adaptations to heavier
mastication in A. anamensis compared with earlier hominins, molar
microwear taken from the occlusal surfaces of the teeth shows no
evidence of the consumption of hard, brittle foods, so if the
morphological adaptations to heavier mastication are indeed adaptations to consuming such items, the hominins may have done so
as fallback foods only (Grine et al., 2012). Australopithecus anamensis
has been reported to have a higher striation density on the buccal
surfaces of its molar teeth than did A. afarensis, which was interpreted to indicate a greater proportion of hard and/or brittle foods
in its diet than in A. afarensis (Estebaranz et al., 2012). However, as
the nonocclusal surfaces of the teeth are not involved in food processing, the links between diet and buccal microwear are less well
established than those involving occlusal microwear (review in
Grine et al., 2012). Australopithecus anamensis and A. afarensis have
been reported to display similar patterns of molar microwear,
suggesting that the material properties of the foods commonly
masticated were not very different; an observation that does not
support the hypothesis that there was increasing adaptation to
consuming hard foot items (Grine et al., 2006, 2012; Ungar et al.,
2010). If microwear instead tracked the amount of grit in the diet,
rather than the properties of foods themselves, however, it could be
that similarities in microwear between these species tracked similarities in environment and terrestrial habitus (Lucas et al., 2013).
Despite the similarities in molar microwear, the isotopic signatures
in the tooth enamel differ between these species, with A. anamensis
503
reflecting an almost exclusively C3 diet, but A. afarensis having
incorporated a mix of C3 and C4 resources (Cerling et al., 2013).
Further work is needed to better understand the links and apparent
discrepancies between masticatory morphology and evidence of
the foods consumed by these early hominins.
One of the earliest derived features of the hominin clade is canine
tooth size reduction, with a decrease in sexual dimorphism in canine
crown height, and the loss of maxillary canine tooth ‘honing’ against
the lower third premolar that occurs in most anthropoid primate
species. As a consequence, canine tooth size and shape have figured
prominently in discussions of Australopithecus origins and early
evolution (Kimbel et al., 2006; White et al., 2006; Plavcan et al.,
2009; Ward et al., 2010; Manthi et al., 2012). Canine tooth crown
reduction was originally thought to have first appeared in Australopithecus (Dart, 1925), but now is known to have characterized even
earlier taxa, Sahelanthropus tchadensis (Brunet et al., 2002), Orrorin
tugenensis (Senut et al., 2001), Ardipithecus kadabba (Haile-Selassie,
2001; Haile-Selassie et al., 2004; Haile-Selassie and WoldeGabriel,
2009) and Ar. ramidus (White et al., 1994, 2006, 2009; Suwa et al.,
2009b). Even though canine tooth crown heights appear to have
been reduced in all of these taxa compared with that of most extant
and fossil apes, the Australopithecus canineepremolar complex is
derived relative to these earlier hominins. Furthermore, canine
tooth form appears to have changed throughout the evolution of
early hominins and Australopithecus (White, 2002; Haile-Selassie
et al., 2004; Kimbel et al., 2006; White et al., 2006). The pattern
and timing of canine evolution are significant for understanding
early hominin evolution, because alterations in canine tooth size and
dimorphism would constitute evidence of social and/or dietary adaptations (Greenfield, 1992; Plavcan, 2000). Furthermore, understanding which changes co-occurred with evidence for masticatory,
locomotor and manipulatory adaptations is important for interpreting the selection shaping the origin and early evolution of
Australopithecus.
In this paper, we describe the new fossils and consider their
implications for understanding the biology of A. anamensis, origins
and early evolution within the A. anamensiseafarensis lineage,
particularly in the canineepremolar complex, one of the key features differentiating hominins from apes.
pedotype that are 80 and 50 cm thick, respectively, but the fossiliferous horizon in each case is only a few tens of cm thick (Wynn,
2000). The unusually good preservation of mammalian fossils in
these soils results from their burial by volcanic ash, now altered to
bentonite (Craig Feibel, Personal observation). Dite paleosols
develop over a period of only tens to hundreds of years (Wynn,
2000) and because it is unlikely that too much time elapsed between initial deposition and paleosol formation, the occurrence of
the hominins within these paleosols suggests that they represent
an almost geologically instantaneous sample. Thus, variation
observed among the Kanapoi hominin individuals probably reflects
minimal time averaging, and thus is a reasonable reflection of
actual population variation.
KNM-KP 47957 comes from the lacustrine sequence deltaic
sands that overlie the lower fluvial deposits, and is marginally
younger than the rest of the specimens, although still below the
Kanapoi Tuff (Leakey et al., 1995; McDougall and Brown, 2008).
Several of the specimens described here (KNM-KP 47952, 47954,
47955, 49388, 52120) were recovered during sieving of the same
area near the type-site (Nzube’s Mandible Site), and share the same
field number (WT10460), but cannot definitively be assigned to the
same individual. KNM-KP 47954 is barely worn, and so is unlikely to
be from the same individual as the heavily worn KNNM-KP 47952.
KNM-KP 47954 could belong with KNM-KP 47955 based on wear,
but this is uncertain because there are no associated upper and
lower dentitions attributed to A. anamensis with which to compare
maxillary premolar with mandibular molar wear. KNM-KP 52120
may not be associated with KNM-KP 47952 with which it was
provisionally associated, as it shows substantially less wear than
this other specimen. KNM-KP 47955 M1 and KNM-KP 49388 P4 are
likewise unlikely to belong to the same individual. Given these
uncertainties, these teeth are accessioned as separate individuals.
During the 2003e2008 seasons (Manthi, 2006, 2008), more
than 250 additional macrofaunal mammalian fossils representing
over 15 genera were recovered during surface prospecting, and
over 3000 microfaunal specimens were recovered in excavations.
Some of these fossils have already been described (Werdelin and
Manthi, 2012; Geraads et al., 2013) while the others will be
described in subsequent publications.
Recovery and context of the new hominin fossils
Descriptions
Nine new specimens attributed to A. anamensis are described
here: one partial edentulous mandible, three associated dentitions,
and five isolated teeth (Tables 1 and 2). All but one of these fossils
(an M3 germ, KNM-KP 47957) were recovered from the lower
fluvial sequence at the site, as were the majority of previously
described Kanapoi specimens including the type specimen KNMKP 29281 (Leakey et al., 1995, 1998; Ward et al., 2001). The fossils
in the lower fluvial sequence derive from two paleosols of the Dite
Each fossil is described first without specific comparative references to provide an inventory of the preservation and
morphology of each. Specimens are described in numeric order.
Possible associations are discussed with the description of each.
Standard metric data are listed in Tables 2 and 3, and other data
are included in the text. Dental measurements were taken following
White (1977) to correspond with those presented by Ward et al.
(2001). Anatomical terminology follows Johanson et al. (1982).
Table 1
Hominin fossils recovered at Kanapoi from 2003 to 2008.
Accession number
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
47951
47952
47953
47954
47955
47956
KNM-KP 47957
KNM-KP 49388
KNM-KP 52120
Element
Discoverer
Discovery date
LCx-P3, RP3e4, two tooth fragments
LI1-Cx, fragment RI1
RCx-M1, RM3, LCx, LM3
RP3
LM1
L edentulous partial mandible,
roots M2e3 & part of M1
LM3 germ
LP4
LM2
Robert Moru
John Mbithi and Robert Moru
Robert Moru
Crew
Crew
Fredrick Kyalo Manthi
2003
2008
2008
2007
2007
2008
Robert Moru
Fredrick Kyalo Manthi
John Mbithi and Robert Moru
2007
2007
2008
504
Table 2
Dental metrics from hominin fossils recovered at Kanapoi from 2003 to 2008.
Maxillary permanent dentition
Specimen
Side
KNM-KP
KNM-KP
KNM-KP
KNM-KP
L
L
L
L
47952
47954
49388
52120
I1
I2
P3
C
MD
LaL
MD
LaL
MD
LaL
9.1
8.5
6.3a
7.5
9.9
10.2
P4
MD
BL
8.2
13.0
M2
MD
BL
8.3a (8.6)
12.6
MD
BLant
BLpost
12.4
13.5
12.9
Mandibular permanent dentition
Specimen
Side
C
MD
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
47951
47951
47953
47953
47955
47957
R
L
R
L
L
L
13.9
12.0
P4
P3
M1
LaL
MAX
MIN
MD
BL
10.1
(9.8)
9.4
(9.3)
(13.2)
10.7
10.1
(13.1)
(13.7)
12.8
(9.4)
(12.8)
M3
MD
BL
13.8
12.0
((13))
12.9
MD
BL
16.8
(16.7)
15.1
15.2
((16.5))
13.7
Tooth root dimensions
Incisors & canines
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
47951
47952
47952
47952
47953
C
I1
I2*
C
C**
MD
LaL
L
13.8
10.3
7.4
9.1
(10.0)
5.1
8.1
(7.5)
31.7
17.1
16.0
23.3
Maxillary premolars
KNM-KP 47954
P
3
MD
BL
12.8
6.7
L-Lingual
L-Buccal
13.9
Maxillary molars
KNM-KP 49388
KNM-KP 52120
M1
M2
MD
BL
L-Lingual
L-Mesiobuccal
L-Distobuccal
8.5
10.6
12.2
13.7
15.2L
13.3
12.5 MB
13.2
15.3 DB
12.5
Mandibular Premolars
KNM-KP
KNM-KP
KNM-KP
KNM-KP
KNM-KP
47951
47951
47951
47953
47953
MD
BL
L-Lingual
L-Buccal
P3R
P3L
P4
P3
P4
12.5
12.9
12.5
11.9
10.3
7.9
8.0
8.4
6.2
6.9
14.7
15.7
15.7
15.8
16.5
MD
BL
L-Mesial
M1
M3
M1
11.9
15.0
11.6
11.8
14.1
11.3
12.2
Mandibular Molars
KNM-KP 47953
KNM-KP 47953
KNM-KP 47955
L-Distal
(9)
Measurements mainly follow White (1977), and BL dimensions for maxillary M1 and M2 given across mesial and distal cusps independently. All measurements given in mm. ()
¼ value estimated due to damage, (()) ¼ less reliable estimate. a ¼ tooth measured as preserved despite interstitial wear. L ¼ length. BL and MD dimensions of mandibular
canine and P3 taken as max/min. * Incisor MD and LaL dimensions at widest point, not cervix. ** Dimension taken on right side.
KNM-KP 47951 e LC1-P3, RP3e4, two tooth fragments (Fig. 1; Table 2)
This associated dentition consists of complete teeth, although
enamel is missing from much of the crowns. Preservation of each
will be described by tooth.
C: This mandibular left canine consists of a complete root, but most
of the crown has been worn off. In mesial or distal view, the apical
contour of the tooth has a sharp mesiodistally oriented ridge of
dentine. The distal portion of the crown is worn along the distal ridge
down to the distal tubercle, and a small amount of enamel remains
just buccal to where it would have been. The crown is preserved from
the cervical margin to a height of 6.4 mm labially, 6.3 mm mesially,
7.9 mm mesiolingually but only 3.6 mm distolingually at what would
have been the distal tubercle. Enamel adjacent to the tubercle is
missing along the side of the tooth in a section about 4.5 mm wide
transversely. A band of enamel 5 mm wide is missing from the
mesiolingual surface. Still, original basal dimensions of the tooth can
be measured. A crack that traverses the entire crown labially and
continues along almost the entire length of the root has a piece of
missing enamel and dentine about 8 mm long and 3 mm wide
extending from the occlusal margin along the mesiolingual corner of
the tooth. This and the other cracks cause no distortion. In places, the
surface of the root is flaked off, but this also does not cause significant
interruptions in the morphology of the tooth.
Although the enamel is chipped in this area, the remains of a
worn distal tubercle is apparent. Distally, the cervicoenamel
505
Table 3
Mandibular corpus depth and breadth at M1 of Australopithecus anamensis and
A. afarensis.
A. anamensis
A. afarensisa
Depth
Breadth
Depth
Breadth
.
34.0
41.0
29.0
17.0
17.5
22.0
.
A.L. 128-23
A.L. 145-35
A.L. 198-1
A.L. 198-22
A.L. 207-13
A.L. 225-8
A.L. 228-2
A.L. 266-1
A.L. 277-1
A.L. 288-1i
A.L. 315-22
A.L. 330-5
A.L. 333w-1a,b
A.L. 333w-12
A.L. 333w-32þ60
A.L. 400-1a
A.L. 417-1a
A.L. 433-1a,b
A.L. 437-1
A.L. 437-2
A.L. 438-1g
A.L. 444-2
A.L. 582-1
A.L. 620-1
MAK 1/2
MAK 1/12
LH 4
.
27.8
31.1
.
28.4
31.1
31.8
31.5
37.0
30.0
29.7
31.1
35.3
30.6
38.4
35.4
36.0
35.0
40.0
38.5
41.3
41.2
.
36.2
.
30.5
31.4
18.0
21.1
15.8
21.7
18.1
.
16.3
21.7
17.9
17.1
19.2
20.9
19.4
17.4
23.6
18.7
18.0
20.2
20.0
22.2
24.7
23.0
21.4
20.5
19.6
18.7
19.4
N
3
3
N
23
26
Mean
SD
Min
Max
34.7
6.03
34.0
41.0
18.8
2.75
17.0
22.0
Mean
SD
Min
Max
33.9
4.12
27.8
41.3
19.8
2.24
15.8
24.7
KNM-KP
KNM-KP
KNM-KP
KNM-KP
a
47956
29281
29287
31713
Data from Kimbel et al. (2004).
junction is fairly straight, but is arched along the mesial margin.
Little else can be said about crown morphology.
The root is complete. There is a broad, shallow, concave groove
up the mesial side along its entire length, but the distal side is
transversely convex. Its tip is angled gently distally. In distal view,
the labial contour is gently convex throughout its length, but more
sharply so toward the root apex. The lingual contour is more
strongly convex, with a bow-shape.
P3: These teeth preserve complete roots, but most of the enamel
is missing on both. On the right side, enamel remains on the metaconid and into the foveas. An irregular strip of enamel about 2 mm
wide along the cervical margin extends all around the tooth except
for almost 5 mm on the distobuccal corner, and 4 mm from the
mesiobuccal corner. Enamel is continuous from this strip to the
lingual side of the distal marginal ridge in a band 3.5 mm tall. There
is also an extension of enamel up the buccal face at the location of
the mesiobuccal groove. On the left side, even less enamel remains,
preserving only the floor of the distal fovea, a piece about 6 mm
wide on the distal margin extending a ways up the distal crest of
the metaconid about to its tip, and another piece about 7 mm wide
and 3 mm high along the mesial margin.
Although these teeth are damaged, estimates of their original
basal crown dimensions can be made (Table 2). The buccal face of
the crown is strongly sloping, so that the protoconid occupies the
center of a buccolingually elongate crown. The metaconid does not
appear to have been prominent, just a bump along the marginal
ridges. The anterior fovea was considerably smaller than the posterior one. It appears to open lingually, rather than occlusally,
although damage somewhat obscures its anatomy. Little else can be
said about crown morphology.
Figure 1. KNM-KP 47951, associated mandibular teeth. The two tooth fragments are
not figured. Top row, mandibular left canine in occlusal, buccal and distal views.
Premolars figured in occlusal (left) and distobuccal (right) views to show maximum
preserved morphology given the areas of missing enamel. From top to bottom: left P3,
right P3, right P4. Two associated tooth fragments not figured.
The roots are almost perfectly preserved. There is a single buccal
root, and the distal and lingual roots are fused into a bifid one. The
buccal root flares out buccally from the crown, whereas the mesial
double root extends almost straight inferiorly from the crown. On
the left side, the root is slightly deflected buccally and then hooks
lingually toward it tip. The maximum buccolingual breadth across
the roots is 16.3 mm on the right tooth and 16.5 mm on the left one;
this occurs at a point along the roots about two-thirds of the way
inferiorly from the crown.
506
P4: This tooth is also missing most of its enamel, except for a
strip along the lingual margin about 6.0 mm wide that extends from
the cervix up to protoconid, and another strip 4.5 mm by 2.0 mm
along the lingual ridge. Most of the lingual portion of the crown is
entirely broken away.
The tooth is worn to expose a dentine lake that extends from the
protoconid tip into the posterior fovea. Foveal morphology is
obscured by damage, as is most cusp morphology. The buccal face
of the tooth is fairly vertical, with a slight bulge along the cervix.
The bifid distolingual root is broken away, preserved for up to
about 11 mm of its length. The grooved but single mesiobuccal root
is complete. It curves smoothly distally toward its apex.
A small fragment of the left P4 is also associated with
this specimen that preserves little morphology, although a roughly
coronal section through the root is visible. There is also an associated fragment of premolar or molar root.
KNM-KP 47952 e LI12, LC1, RI1 fragment (Fig. 2; Table 2)
This specimen consists of complete left maxillary incisors and
canine.
I1: This is a complete left central incisor. There is a small chip of
enamel missing from the mesiolabial corner. It is heavily worn,
with only 5.8 mm of enamel remaining labially, 5.5 mm lingually,
Figure 2. KNM-KP 47952, associated maxillary teeth. Teeth figured in occlusal view
(above) and labial view (below), from right to left I1, I2 and maxillary canine. Associated
tooth fragments not figured.
1.5 mm mesially and 2.0 mm distally. This would have been probably about half of the original tooth height based on comparisons
with complete A. anamensis specimens. The plane of wear angles
distally about 5 and lingually about 10 . At the current occlusal
plane, the crown measures 9 mm mesiodistally by 6 mm labiolingually. There is a mild basal swelling, but no other crown
morphology is preserved except for some strong hypoplastic lines
along the labial surface. The tooth is triangular in cross-section. Its
tip angles very slightly lingually. In mesial view, the labial side is
more convex than the lingual one toward the apex.
I2: The lateral incisor is heavily worn with an oblique wear
gradient running mesially to distally. There is only 0.5 mm of the
enamel left along the distal and mesial margins. The cementoenamel junction arcs higher mesially than distally. The linear
distance from the occlusal margin to the apex of the root is
17.5 mm on the distal side and 19.1 mm on the mesial side. Along
the labial surface of the crown, the linear distance from the
cervix to the preserved edge of the occlusal margin is about
2.5 mm on the distal side and 5.0 mm mesially, thus angling the
labial edge of the crown about 15 superolaterally relative to the
long axis of the root. The wear plane also angles about 30
lingually.
Because it is so heavily worn, no features of the crown remain,
except for a few hypoplastic lines on the remaining labial surface.
The lingual swelling near the cervix is barely preserved. The
remaining mesial side of the crown flares out from the root to about
0.6 mm at its preserved margin. Too little of the distal side remains
to assess contours here.
The widest part of the root is about halfway down the length of
the root. The root is mildly grooved on both mesial and distal sides.
It extends straight superiorly from the crown for about half its
length, then is inclined slightly mesially toward its tip. In mesial or
distal view, the root is curved lingually, strongly convex labially and
mildly concave lingually.
C: This tooth is also very heavily worn. The enamel is preserved
in a continuous band around the base of the tooth, extending in
height from the cervix only 1 mm distally, 3 mm lingually and
mesially, and 7 mm labially. The pulp cavity is evident in the
center of the occlusal surface. The crown is roughly oval in occlusal
view, with its long axis running mesiolabially to distolingually. The
distal slope of the wear surface makes an angle of about 40 with
the long axis of the root in lingual view, and the same in mesial
view. Most of the plane of wear is uniform except at the mesial
margin, where it becomes more horizontal just over the mesial
basal tubercle, and at the distobuccal corner of the tooth, where it
arcs to a flattened area just at the distolingual fossa. The basal
bulge of the crown is preserved lingually. There is also a greater
basal crown flare mesially than distally. Hypoplastic lines are
visible on the lingual surface. An interstitial wear facet for the
third premolar is preserved, and has worn through most of the
distal enamel. It measures about 3.1 mm labiolingually and 1.0 mm
high, reaching to the occlusal margin. No interstitial wear facet is
present mesially.
The cervix arches acutely on the mesial side of the tooth, but is
otherwise nearly horizontal with the exception of a small arch
immediately superior to the interstitial wear facet. The root is
complete. Mild abrasion at the tip does not substantially affect its
contours. The root arcs lingually toward its tip, so that in mesial or
distal view the labial surface is uniformly convex and the lingual
one uniformly concave, but in lingual view arcs only gently
distally.
I fragment: This is a fragmentary right central incisor preserved
from near the tip of the root to a point just less than 5.0 mm along
the crown, but it is only about 3.2 mm wide and preserves no useful
morphology. In parts preserved, it matches the left side.
507
Figure 3. KNM-KP 47953, associated mandibular teeth. Teeth figured in occlusal (above), lingual (middle) and mesial (below) views. From right to left, right canine P3, P4, M1, M3,
left M3, left canine.
KNM-KP 47953 e RC1-M1, RM3, LC1, LM3 (Fig. 3; Table 2)
This associated dentition preserves the crowns and partial roots
of seven teeth. Most teeth are traversed by cracks, some of which
are wide and have caused some expansion. These are discussed
with the description of each tooth.
C: The right canine consists of the crown and almost 19 mm of
the root. The crown is complete. It is traversed by small cracks, the
most substantial of which runs vertically up the labial face to the
tip, but even this is only 0.2 mm wide. There is a chip of enamel
missing from the lingual surface near the crown tip about 1.5 mm
tall and 1.5 mm wide, but this does not disturb the major contours
of the tooth. The root is broken and missing the apical portion.
Although the root is beginning to narrow near the break, it still
measures a maximum of 10.0 mm and probably a minimum of
about 7.5 mm accounting for the expansion cracks at the break. The
root is traversed by cracks, but with the exception of one crack near
the break, about 0.5 mm wide, none of these appear to significantly
alter the root from its original shape or dimensions. It also shows
slight surface weathering along its distal side.
The left canine is more poorly preserved, missing the mesial
third of its crown and root and most of the distal enamel. The root is
irregularly broken off, preserving the distal half for a length of
approximately 9 mm from the cervical margin. In parts preserved,
its morphology matches that of the right side, so morphology will
be described only from the right tooth.
The right canine crown is 15.7 mm high labially as preserved,
but is lightly worn at the tip and probably would have been over
16.0 mm high before wear. Any possible wear along its distal
margin is obscured by weathering, but if present would have been
slight. The tooth is markedly asymmetrical, with the typical
A. anamensis bend of 30 of the mesial contour at the mesial
marginal ridge. The mesiolingual fossa is shallow and broad. The
distal margin of the crown is straight for most of its length but
becomes concave toward the distal basal tubercle, which is
prominent and visible in both lingual and labial views, and situated
at a level about 5 mm inferior to the mesial marginal ridge. The
distolingual fossa is tall and narrow. The lingual ridge extends
smoothly from the floor of the mesiolingual fossa, but is sharp
along its distal edge. In mesial view, the lingual ridge is mildly
convex for its apical half, but is gently concave toward the gentle
basal swelling that traverses the entire lingual side of the crown,
but almost fades away toward the mesial margin. The labial face
has a mild but distinct mesiolingual groove, but is otherwise
featureless. Several hypoplastic lines are visible throughout its
cervical third, but not further apically.
508
P3: This crown is complete. It is traversed by three cracks that
meet at the apex. The largest crack is 0.1 mm wide and traverses the
distal fovea. Another crack traverses the mesiobuccal surface, and a
third smaller crack traverses the anterior fovea. At the apex where
the cracks meet, there is a 0.5 mm fragment of enamel missing,
obscuring details of apical wear. There is a single root that is broken
11.0 mm from the cervix buccally and 5.1 mm lingually.
The tooth is very lightly worn, with some polishing visible on
the preserved portion of the apex, and along the distal marginal
ridge, but none anywhere else. The large protoconid is almost
centrally placed on the crown, which is oval in occlusal view. The
metaconid exists only as a faint bump on the mesial end of the
distal marginal ridge. The anterior fovea opens lingually, and the
mesial marginal ridge almost meets the cervical line. The ridge
continues onto the buccal face, demarcating a tall, narrow mesial
fovea, the distal portion of which is marked by a series of small
vertical ridges near its cervical edge. The distal marginal ridge is
pronounced, with a distinct distal tubercle, but extending for a
short way onto the buccal face. The distal fovea is large, deep and
smooth, and opens superiorly. Buccally, the lingual ridges merge
with a barely distinct basal swelling. No hypoplastic lines are
apparent.
The root has a deep longitudinal groove mesially, and one
distally, so it has the appearance of three smaller roots fused
together. The mesiobuccal portion of the root curves markedly inward at its tip, suggesting that the root is fused until its apex.
P4: This crown is complete, but traversed by two expansion
cracks orthogonal to each other. The largest divides the entire tooth
into lingual and buccal halves, running from the mesiobuccal
corner through the distal face, just lingual to the protoconid and
along the buccal margin of the posterior fovea. It expands from
about 0.5 mm wide mesially to almost 1.0 mm wide distally. The
buccal side of the tooth appears to be slightly offset mesially along
this crack approximately 0.2 mm relative to the lingual half. The
other crack is about 0.3 mm wide and runs from the lingual face to
meet the larger crack along the mesial margin of the posterior
fovea.
The crown is broadly oval in occlusal outline. It is very lightly
worn. The large protoconid is placed almost centrally along the
buccolingual axis of the crown, but is slightly closer to the mesial
edge than the distal one. The metaconid is smaller but almost as
high. The anterior fovea is less than half the size of the distal fovea,
and both are smooth. Both marginal ridges are sharp. The buccal
face is marked by a wide, mild basal bulge. There is a sharp distal
fovea that delineates a distinct cuspule on the distal occlusal
margin and continues into the distal fovea. The mesial groove is a
much fainter vertical groove. Mesially there is an interstitial facet
that is about 2 mm in diameter as preserved, set along the lingual
half of the crown, but its buccal extent is obscured by some surface
weathering in this area. Distally, a faint interproximal facet that
would have measured about 2.5 mm wide by 1.0 mm high is situated along the lingual half of this surface.
There is a single deeply grooved root preserved for just more
than 10 mm of its original length. The broken edge is irregular.
M1: This tooth is mildly weathered, especially in the area of the
anterior fovea, but no major features or contours are lost. Several
cracks traverse the crown, but the only one wider than 0.1 mm
passes just lingual to the hypoconulid continuing to the central
fovea. The roots are broken so that the mesial one is preserved for
up to 11.0 mm of its length and the distal one for up to 12.2 mm.
The tooth is rectangular in outline, only barely broader mesially
than distally, and lightly worn, with polishing of the buccal cusps
into the floor of the central fovea. Enamel crenulations are still
preserved along the lingual cusps. Potential dentine exposure on
protoconid and metaconid cusp tips is obscured by a transverse
crack through both, but a tiny dentine pit seems to have been
present on the metaconid. The mesial cusps are larger than the
distal ones. The lingual cusps are higher than the buccal ones, but
the latter are partly worn down. The metaconid is the largest cusp,
followed by the protoconid, hypoconid, entoconid and then
hypoconulid. No C6 (tuberculum sextum) is present, although the
groove between the hypoconid and hypoconulid turns sharply at
the buccal margin of the crown, so that there is a slight ridge
extending mesially from the buccal side of the hypoconulid where
a C6 would be. The mesiobuccal groove is continuous with the
lingual groove across the central fovea. The anterior fovea is about
2 mm wide, bounded by a wide mesial marginal ridge that wraps
partway around the metaconid, and set lingual to the midline of
the tooth. The posterior fovea exists as a pit between the entoconid and hypoconulid, bounded by a rounded distal marginal
ridge.
Mesially, a centrally placed interstitial facet is 5.0 mm wide and
2.5 mm high, but does not quite meet the occlusal margin. Distally,
weathering obscures this area. The lingual side is featureless, with
the lingual groove sharply incising the occlusal margin but terminating midcrown. The mesio- and distobuccal grooves are less
distinct, but the adjacent cusps are slightly worn. They extend onto
the buccal face and disappear into the cingular remnants. A protostylid exists as a small tubercle along the distal portion of the
protoconid, and cingular remnants are apparent along the lingual
surface of the tooth, mostly manifest as mild vertical enamel
crenulations.
Both roots are straight in buccal view and inclined distally. The
mesial root has a broad, deep groove, the distal one less so.
M3: Both M3s are present, and are morphologically similar to
one another. Crowns are complete on both, but the left has an
expansion crack up to 0.4 mm wide distobuccally that traverses the
mesiodistal axis of the tooth. A second expansion crack of similar
width passes from the distal buccal cervical margin across the
hypoconid to intersect the first on the lingual surface of the
hypoconid. The roots are more extensively preserved on the right
molar. Description is based on the right tooth with any differences
noted by feature. On the right, the mesial root is preserved up to
13.0 mm and the distal to 11.5 mm of its length, but on the left the
roots are preserved only up to 6.0 mm mesially and 10.0 mm
distally.
The occlusal outline of this tooth is almost rectangular, but
with a rounded and reduced distolingual margin. There are five
cusps. The tooth is lightly worn on all cusps, but some enamel
crenulations are preserved in the anterior and lingual portions of
the central fovea. The buccal cusps are larger in area than the
lingual ones. Cusp size from largest to smallest is: metaconid,
protoconid, entoconid, hypoconid and hypoconulid. The mesiobuccal groove is directly continuous with the lingual groove
across the tooth. The anterior fovea is a large slit positioned
centrally along the buccolingual axis of the tooth, extending
almost to the tip of the metaconid and partway up the protoconid. The distal fovea is slightly smaller, and the distal marginal
ridge wraps partway along the hypoconulid on the right. Mesially, an interstitial facet 5.0 mm by 2.5 mm is present, but it does
not extend to the occlusal margin. The lingual groove sharply
incises the lingual face, and disappears about halfway down the
crown face. Buccally, cingular remnants are present mostly in the
form of faint vertical crenulations, but there is also a protosylid
present on both sides as small tubercles, and another small ridge
along the buccal side of the hypoconulid. It forms a slit-like fovea
in occlusal view that on the left side reaches almost to the
hypoconulid tip, but is barely present on the right. The mesiobuccal and distobuccal grooves disappear into the cingular remnants partway down the crown face, respectively.
509
The roots are inclined distally and buccally. The distal root is
thicker and more substantial than the mesial one. The mesial root is
mesiodistally thinner than the distal one and has a broad shallow
groove, whereas the buccal root is not grooved.
KNM-KP 47954 e RP3 (Fig. 4; Table 2)
This specimen is complete except for the superior half of the
buccal root. Fine vertical cracks traverse the crown, but cause no
apparent distortion. The largest crack also extends through the
length of the lingual root, and in the crown is about 0.1 mm wide. It
cannot belong to the same individual as KNM-KP 47952 because it
is much more worn. KNM-KP 47954 shows dentine exposure on
both the paracone and protocone.
The tooth is fairly symmetrical in lingual view, with the basal
contour of the paracone slightly more extensive mesially. The
cusps are subequal in size, with the larger paracone occupying the
buccal 5.5 mm of the occlusal surface and the protocone only the
lingual 4.5 mm. Their apices lie closer to the mesial margin of the
crown than the distal one. The surface is polished. The paracone
shows a small, ovoid dentine lake just over 1 mm long, and the
protocone shows a slightly smaller spot of dentine exposed at the
apex of the cusp. The anterior fovea is a small, narrow groove
sitting just inside a thick mesial marginal ridge, and mesial to the
cusp centers. The posterior fovea is indistinct and the distal marginal ridge very strong. Mesial and distal buccal ridges are indistinct as well.
In occlusal view, the mesial and distal faces of the tooth are
parallel, each with a substantial interstitial wear facet visible. The
mesial interstitial facet is 3.8 mm buccolingually by 2.0 mm high,
and meets the occlusal margin throughout its length where it forms
a very slight concavity in the occlusal profile. The distal interstitial
facet is 5 mm wide, and also meets the occlusal margin but is flat. It
is centered very slightly buccal to the midline of the tooth, and has a
slightly irregular surface near its center along the occlusal margin.
The buccal and lingual faces are featureless except for a mild basal
swelling, and the lingual one is more sloping.
This tooth had two roots. The preserved lingual root slopes
gently lingually and distally. The buccal root is broken 6.8 mm from
the cervix.
KNM-KP 47955 e LM1 (Fig. 5; Table 2)
This specimen is missing enamel from most of the mesial side
of the crown through the sides, including the mesial marginal
ridge, extending to what would have been the tip of the metaconid. Enamel remains along the cervical margin up to a thickness of about 2.3 mm along the buccal margin of the interstitial
facet, and only just over 1.0 mm thick buccal and lingual to that
point. Enamel is also missing from the distal margin of the tooth,
so that only the mesiobuccal corner of the occlusal surface of the
hypoconulid remains. Almost all of the hypoconid remains intact.
A 5 mm long flake of enamel along the cervical portion of the
lingual face is very slightly displaced above the rest of the surface.
Crown shape and cusp sizes are obscured by the missing
enamel and wear, but the tooth would have been roughly square in
occlusal view. The lingual face is more vertical than the buccal one,
and the lingual cusps are higher. The surface of the tooth is worn
and polished. There is a deeply excavated dentine lake on the
protoconid and anterior fovea that is about 3.2 mm buccolingually
and extends from the mesial margin of the tooth for about 4.3 mm
distally. There is small dentine pit just over 1 mm in diameter in
the center of the hypoconid, and although the tooth is broken
another smaller area of dentine exposure was present on the
hypoconulid. No dentine is exposed on the lingual cusps, but they
Figure 4. Isolated teeth. All shown in occlusal, buccal and mesial views except for
KNM-KP 47957, which is a broken germ and only shown in occlusal view.
510
Figure 5. KNM-KP 47956, partial left mandible, in occlusal and lingual views (top row), basal and buccal views (bottom row), and anterior view showing cross-sectional shape at the
anterior edge of the fragment.
are worn so that their surfaces are smooth. Faint grooves from
what would have been some crenulations are barely visible, but
are mostly worn off. The metaconid is higher than the entoconid.
These cusps are separated by a groove that incises the lingual
margin and continues halfway down the lingual surface of the
crown, terminating just before reaching the disconformity in surface enamel. The buccal surface of the tooth is fairly smooth, with
only a faint vertical groove near its center along the occlusal
margin that may reflect a cingular remnant, but this is unclear due
to wear and damage.
The roots incline gently distally from the crown. Both are mildly
grooved. The mesial root is complete. The distal root is broken at
the tip but would not have been longer than about 9 mm.
KNM-KP 47956 e L partial mandible (Fig. 5; Table 3)
This is the body of an edentulous mandible preserved from the
distal root of M1 posteriorly through the angle and anterior margin
of the ascending ramus. Although a small specimen, it is adult,
because the roots of M3 are clearly present. In addition, although
the specimen is too dense to permit crisp radiographic images,
radiographs reveal no crypts developing within the bone. It is
52 mm long as preserved. Small cracks traverse the specimen, the
surface bone is mildly weathered with occasional thin flakes of
lamellar bone missing, but this does not disturb the contours of the
bone.
Laterally, the extramolar sulcus begins adjacent to M2 where the
bone is swollen. The sulcus is up to 7.5 mm wide adjacent to M3. The
lateral torus is smoothly rounded and blended with the base. The
bone along the preserved portion of the ascending ramus is mildly
concave along the posterior break where the surface of the bone
flares laterally at a point just posterior to M3.
The lingual part of the alveolar margin is preserved as a
distinct ridge flanking the teeth, although surface bone is missing
along the entire occlusal surface around the tooth roots. There is
a well-excavated subalveolar fossa just over 10 mm from the base
of the mandible, but no obvious mylohyoid line, only a rounded
ridge along the inferior margin of the bone. There is a faint
groove for the lingual nerve along the medial surface of the
preserved portion of the ramus. The base is rounded and not
everted.
The posterior break is through the anterior portion of the ramus,
and here the bone flattens to a fairly uniform thickness of just over
about 10 mm. Both the buccal and lingual surfaces of the bone are
concave just anterior to this break.
Where broken just below M1, the mandibular body measures
26.0 mm superoinferiorly by a minimum of 16.8 mm transversely.
From what can be seen of the roots, M2 was larger than M3,
especially mesiodistally. As preserved and exposed, the
tooth roots measure about 8.5 mm buccolingually for the distal
M1 root, 11.5 mm mesiodistally by 11.0 mm buccolingually for the
M2, and about 10.0 mm by 9.5 mm for the M3.
KNM-KP 47957 e LM3 germ (Fig. 4; Table 2)
This is the germ of an M3 that had just barely completed crown
formation. Occlusal enamel remains, but the only enamel remaining on the sides of the tooth are a strip about 5.4 mm wide along the
side of the hypoconid, and another about 5.6 mm wide along the
entoconid and small part of the hypoconulid.
The surface of the germ is highly crenulated. The mesial cusps
are larger than the distal ones. The area and height of the protoconid are hard to determine as enamel is missing up to its apex. The
anterior fovea barely exists as a small slit. The distinction between
hypoconulid and possible C6 is obscured by the crenulations, but it
appears that the hypoconulid was large and C6 narrow. What appears to be the remains of a cingulum on the lingual surface of the
entoconid appear as pits in the surface enamel. No other detail is
preserved on the sides of this tooth.
KNM-KP 49388 e LP4 (Fig. 4; Table 2)
This tooth is nearly complete, missing a strip of enamel on its
lingual face that is 5.5 mm wide at the occlusal margin but only
2.3 mm wide at the cervix. This enamel strip is continuous with a
1.5 mm strip missing along the junction of mesial and occlusal
surfaces across the tooth, and a 1.5 mm wide strip running along
distobuccal corner from occlusal surface to cervix. The roots are
completely formed. The mesiobuccal root has a transverse break
that disrupts the surface contour of the root, displacing the apical
portion so that it is offset by about 0.4 mm mesially from the
cervical portion at the break and angled slightly distally. The
surface is somewhat weathered and uneven, but the original
contours are preserved. There is some bone adhering to the
mesiobuccal root.
The tooth is moderately worn, exposing dentine on the paracone in a strip measuring about 1.5 mm buccolingually that continues distally to the broken regions of enamel. The protocone also
exposes dentine in a small pit about 0.2 mm in diameter. In spite
of apical wear, the protocone remains slightly taller than the
paracone.
In occlusal view, the crown is buccolingually elongate. It is
almost straight in profile along its mesial margin, and almost
smoothly convex across buccal, distal and lingual margins. The
paracone occupies about two-thirds of the surface, the protocone
the remaining third.
In mesial or distal view, the buccal face is more sloping than is
the lingual one, with a distinct basal bulge. A small piece of an
interstitial wear facet is visible mesially along the missing portion
of enamel, but its dimensions cannot be estimated. The facet sits
well buccal to the buccolingual midline of the tooth. A portion of an
interstitial wear facet is apparent distally at the buccolingual center
of the tooth that extends to the band of missing enamel. It sits
adjacent to the root bifurcation and is up to 4 mm wide as preserved, but would have been wider. Distally, the cervical margin
exhibits a distinct concavity adjacent to the mesiobuccal tooth root.
The basal crown bulge is more pronounced mesially. In buccal
view, the cervical margin of the crown angles superiorly toward the
mesial edge of the tooth.
The roots all curve distally at their tips.
KNM-KP 52120 e LM2 (Fig. 5; Table 2)
This molar is complete except for enamel missing from most of
the mesial side, from the lingual base of the paracone through the
mesiolingual corner of the protocone that extends vertically from
the cervix to almost the center of the protocone. The distolingual
corner of the crown is also missing, but the margins of the entocone
remain. The molar enamel is weathered and white, and slightly
pitted over much of its surface. Some cracks traverse the surface,
but have caused no apparent distortion. This tooth is most likely an
M2 because the remains of large interstitial facets are visible on its
mesial and distal surfaces.
Despite the missing marginal enamel, it is apparent that the
occlusal outline of this tooth was almost rectangular but with a
rounded distobuccal corner. The crown is worn so that the buccal
cusps are only slightly higher than the lingual ones, and there is
only a tiny area of dentine exposure on the protocone. No other
cusps have dentine exposure. Most occlusal detail is missing,
although a broad crista obliqua seems to have been present. A small
distal fovea is bounded by a thick marginal ridge. There is a double
lingual groove extending from the occlusal surface to about halfway
up the crown. There is a buccal groove that terminates halfway
down the crown on a small Carabelli’s feature.
Mesially, there is about 1 mm of an interstitial wear facet present starting roughly even with the buccolingual center of the
buccal roots, and reaching to the occlusal margin. Distally, about
3 mm of the distal interstitial facet is present and situated at the
center of the surface, but it does not extend to the occlusal surface.
511
These facets enable measurement of mesiodistal crown length, and
despite the damage, the facets do not appear to have substantially
reduced the length of this tooth.
There are two buccal roots and one lingual root that are almost
perfectly preserved. The mesiobuccal root projects directly superiorly from the tooth. The distobuccal root is inclined buccally and
mesially, and gentle arches mesially toward its tip. The lingual root
is inclined lingually.
Materials and methods
The partial mandible KNM-KP 47956 was compared with the
other three Kanapoi mandibles (KNM-KP 29281 [the type specimen], KNM-KP 29287 and KNM-KP 31713), and its dimensions to
published values from mandibles attributed to A. afarensis from
Hadar, Maka and Laetoli (n ¼ 26, Kimbel et al., 2004). The teeth
were compared with those of extant great apes (Gorilla gorilla
n ¼ 50, Pongo pygmaeus n ¼ 18, Pan troglodytes n ¼ 30, Pan paniscus
n ¼ 31, and Homo sapiens n ¼ 50), as well as A. afarensis, previously
described A. anamensis and Ar. ramidus.
Linear metric data from fossils were taken on original Kenyan
A. anamensis specimens by one of us (CVW) following methods
described by White (1977), also used by Ward et al. (2001).
Australopithecus afarensis data were kindly provided by William
Kimbel, and checked against measurements from casts taken by
CVW to ensure consistency between datasets. Data for the Fejej
fossils were taken by CVW. Ardipithecus ramidus data were taken
from Suwa et al. (2009a, b) with supplementary data on crown
heights kindly provided by Gen Suwa, Tim White and Berhane
Asfaw, with the stipulation that the unpublished numbers are not
for reproduction. Data for the Asa Issie A. anamensis specimens
were taken from White et al. (2006) and checked against the
originals by CVW.
There are some minor variations the terminology used to
describe tooth size measurements in humans and non-human
primates, particularly for canine teeth. Typically, most nonhuman primate mandibular and maxillary canine teeth are ovoid
in cross-section at the base, and their size is easy captured as a
greatest length, and greatest breadth perpendicular to the greatest
length. This axis of the tooth usually embraces or nearly embraces
the base of the mesial and distal crests of the tooth. For most nonhuman primates, the greatest dimension of the maxillary canine is
oriented approximately along the mesiodistal axis of the postcanine toothrow, though the long axis of the tooth is often rotated
so that the anterior border swings laterally away from the dental
arcade. In contrast, the base of the mesial and distal crests of the
human maxillary canine are aligned along the mesiodistal axis of
the dental arcade. Notably, the human tooth is ‘mesiodistally
compressed’ in that this axis, which morphologically is homologous to the greatest length of a non-human primate maxillary
canine, is narrower than the orthogonal axis.
For the mandibular canine of non-human primates, the axis
defined by the base of the mesial and distal crests is usually not
oriented along the maximum diameter of the tooth. In humans,
the axis defined by the base of the crests is, like the maxillary
canine, aligned along the mesiodistal axis of the dental arcade.
Because of variation in the position of the crests relative to the
long axis of the mandibular canine in non-human primates,
occlusal dimensions are often measured as the greatest diameter
(the long axis of the tooth) and the diameter perpendicular to this.
Human mandibular canines may be measured along the mesiodistal axis (with the buccolingual axis defined as orthogonal to
this), or as for non-human primates, along the greatest diameter
and the axis perpendicular to this. Because of variation in
mandibular canine morphology, we simply use the greatest
512
diameter and diameter orthogonal to this as the measurement of
mandibular canine tooth size.
The same definitions apply to the mandibular canine measurements for non-human primates. Similarly, because the P3 is normally oriented obliquely relative to the toothrow, basal dimensions
of the P3 are also measured as maximum and minimum in all human and non-human primates.
Crown height for all specimens was measured from the
cervicoenamel junction on the mesiobuccal face of the canine to the
apex. For many primates, wear is a normal and necessary part of
canine function, and in some species the apex of the tooth is worn
before it is finished erupting. Canine crown height data from
Plavcan (1990) for 89 extant primates demonstrate that ‘moderately worn’ (teeth showing some blunting of the apex) and unworn
canines do not significantly differ in crown height (Plavcan et al.,
2009). Given that the criteria used for excluding worn canines for
this study were more stringent than for the Plavcan (1990) data set,
apical wear had no significant impact on our results as far as nonhominin primates are concerned.
Measurements of hominin crown height were not corrected for
apical wear, even though several teeth clearly show apical blunting
(Manthi et al., 2012). While including worn specimens slightly
depresses the mean canine height for the hominin sample, and
increases the variance, the overall change in variation and the range
of crown height is small by comparison to interspecific differences
in canine size. Adding several millimeters to canine dimensions for
worn teeth does not affect the results of this study.
Canine data for Ar. ramidus were, as reported to us, ‘corrected’
for wear and damage. Having not studied the original specimens,
we cannot quantify whether the measurements are exactly comparable with ours or not. Nevertheless, restricting crown height
comparisons to only unworn teeth does not alter any of our results
and conclusions (see Manthi et al., 2012). Therefore, conclusions
drawn from comparisons between the Ardipithecus and Australopithecus canine crown heights appear to be robust.
Canine root measurements were gathered by one of us (CVW)
for all extant non-human primates and the hominins. Root
‘buccolingual’ and ‘mesiodistal’ dimensions for all specimens were
collected just below the cementoenamel junction along the same
axis as the corresponding crown size measurements. Where
possible, root length was measured from the cementoenamel
junction to the apex of the root. For many extant specimens, loose
teeth were not available. Tooth roots in this case were measured
from radiographs. A small wire marker was placed at the cementoenamel junction, and the specimen was oriented so that the long
axis of the root was parallel to the film. Measurements taken from
radiographs closely matched those taken directly from loose teeth
(Plavcan et al., 2009).
Standard parametric and non-parametric statistical tests were
used for most comparisons, as noted where appropriate. To
compare the range of variation in root length between hominins
and extant apes and Homo, a bootstrap analysis was carried out
using a program written in Matlab version 5.3. For each fossil taxon
comparison, 1000 random samples from each extant taxon were
selected with replacement, and without regard to sex, selecting the
same number of specimens as available for the fossil sample. The
number of samples with a range equal to or exceeding that of the
fossil sample were tabulated. Ordinary statistics were carried out
with Systat (v. 11). Bivariate comparisons of group elevations and
slopes were carried out using SMATR (Wharton et al., 2006) software. This program allows ordinary ANCOVA, as well as comparison
of group elevations using reduced major axis lines and in cases
where interactions violate the assumptions of ordinary ANCOVA.
Comparative anatomy
Mandible
KNM-KP 47956 is the smallest mandible discovered at Kanapoi to
date, although is only marginally smaller than KNM-KP 31713 (Ward
et al., 2001) (Fig. 6, Table 3). KNM-KP 31713 measures a maximum of
29 mm superoinferiorly from base to lateral alveolar margin at M1
and 18 mm in minimal transverse breadth. Even accounting for the
eroded alveolar bone, KNM-KP 47956 is smaller than KNM-KP 31713.
Figure 6. Lateral view of KNM-KP 47956 (reversed for comparison) compared with the previously published mandibles from Kanapoi and attributed to Australopithecus anamensis,
KNM-KP 31713, KNM-KP 29281 (A. anamensis holotype), and KNM-KP 29287. All shown in lateral view.
It was not as tall as 29 mm originally, and is only 17 mm thick. This is
similar in size to some of the smallest A. afarensis mandibles, with A.L.
145-35 and A.L. 288-1 being about 30 mm tall at the same point. In
contrast, the A. anamensis type specimen KNM-KP 29281 is slightly
damaged inferiorly, but measures about 34.0 mm by 17.5 mm here,
and the large male KNM-KP 29287 is also damaged but would have
been at least 41.0 mm by about 22.0 mm. The A. anamensis mandible
from Allia Bay, KNM-ER 20423, is not preserved at this point, but was
only slightly smaller in parts preserved than KNM-KP 29287. This
latter specimen has a fairly large canine root, suggesting that KNM-KP
29287 and KNM-ER 20432 are most likely males, whereas the smaller
canine roots of KNM-KP 29281, 31713 and 47956 suggest that these
specimens are likely to be females.
The range of variation in the small sample of mandibles from
Kanapoi does not exceed that of A. afarensis, and is slightly smaller
(Table 3). This suggests a range of size variation within the Kanapoi
sample not dissimilar to that known for A. afarensis. Though
A. afarensis is commonly viewed as strongly sexually size dimorphic
(Johanson et al., 1982; McHenry, 1992; Plavcan et al., 2005; Harmon,
2006; Green et al., 2007; Gordon et al., 2008; Kimbel and Delezene,
2009), it has also been claimed that this species showed ‘humanlike’ skeletal dimorphism, with an implication of lower degrees of
body mass dimorphism (Reno et al., 2003, 2005, 2010). These later
analyses dismiss higher estimates of size dimorphism as an artifact
of possible temporal variation. The A. anamensis mandibles
described here all derive from a narrow temporal margin (Wynn,
2000; Feibel, 2003; McDougall and Brown, 2008) and thus reflect
minimal temporal variation. If the sex attribution above, based on
canine roots, is correct, the ratio of male to female mandibular
depth for these specimens would be 1.35, and mandibular breadth
1.26. Assuming an isometric relationship between mandibular
dimorphism and body mass dimorphism, this would imply body
size dimorphism of 2.46 and 2.00, respectively (cubing the ratios
for the linear dimensions to make them compatible with those
derived from body mass), which is comparable with that of extant
Gorilla. Using regressions of mandibular breadth and depth
dimorphism versus body mass dimorphism for 129 extant anthropoid taxa (from RMA lines fit using independent contrasts,
Plavcan, 2003) yields almost identical size dimorphism estimates of
2.24 and 2.03, respectively. Using other methods for estimating
dimorphism where sex is unknown yields similar results.
Dentition
Incisors The only new incisors from Kanapoi are those of KNM-KP
47952. These specimens are highly worn, with only small ribbons of
dentine remaining along their lingual margins (Fig. 2). The wear
facets are angled lingually and distally. Little other comparative
or anatomical observations can be made about them. Overall, the
sizes of the teeth as preserved are comparable with those
previously described for A. anamensis (Table 4).
The wear, however, is extreme, and is only slightly less than that
seen in the teeth from the KNM-KP 29283 maxilla. Both of these
specimens are more heavily worn than any described so far for
A. afarensis (Ward et al., 2010) and are matched only by the
mandibular teeth from Fejej, Ethiopia (Fleagle et al., 1991). KNM-KP
30498 also seems to have relatively heavy anterior wear compared
with its molars, as does KNM-KP 29283 (Ward et al., 2001, 2010). In
fact, no unworn incisors from A. anamensis have been published
except those of young individuals whose teeth are either not yet or
barely in occlusion, and/or who exhibit little or no molar wear
(Ward et al., 2001, 2010). The only relatively unworn maxilla with
canine is ASI-VP-2/344 from Aramis, which has no dentine exposure on M2 but still exhibits apical wear on its canine (White et al.,
2006). In contrast to what we see in A. anamensis, no anterior teeth
513
attributed to A. afarensis have the entire crown worn away.
Whether this represents a real difference or is a spurious consequence of small sample sizes remains to be tested with the recovery
of more A. anamensis fossils.
Canines The canine crown of the new mandibular dentition, KNMKP 47953, has a crown that is slightly taller than for all other
A. anamensis canines (Figs. 7 and 8; Table 5), and very slightly
larger in basal dimensions compared with all but KNM-KP 28291
(Tables 2 and 4). Its overall crown shape is reminiscent of KNMKP 29284 and KNM-KP 29286, with strong basal tubercles, a high
lingual shoulder and narrow-blade-like profile in lingual view
(Fig. 8). KNM-KP 47953 has shallower mesial fovea than these
other specimens, but the variation seen does not appear to be
any greater than would be suspected within a single species.
Unfortunately the crown of KNM-KP 47951 is both worn and
broken, so its original crown height and form cannot be
determined. Almost no morphology remains on the highly worn
canine crown of KNM-KP 47952, either.
The new canine teeth from Kanapoi are especially interesting, as
they provide important information on the pattern of canine evolution in hominins (Ward et al., 2010; Manthi et al., 2012). While
canine tooth size reduction has long been seen as a critical feature
of hominin evolution, there is no consensus explanation for the
mechanism underlying canine reduction, and the selective factors
underlying the transition from an ape-like canine to that of modern
humans are not clearly understood (review in Greenfield, 1992). It
is universally accepted that large canine teeth are maintained by
selection associated with their use as weapons, primarily in intrasexual competition (Plavcan et al., 1995; Plavcan, 2001; Leigh et al.,
2008). A reduction in canine tooth crown height is commonly
assumed to reflect an absence of selection to maintain large canines, either because male competition is reduced in intensity, or
absent, or because hand-held weapons replaced the canines as
weapons in determining the outcome of intrasexual contests
(Brace, 1972; Greenfield, 1992; Plavcan and van Schaik, 1997).
Regardless, this fails to specify a selective pressure to actually
reduce the canines. Various hypotheses have been put forward,
including crowding of the roots, selection to incorporate the canines into an incisal functional field, the probable mutation effect,
selection against threatening features, and selection against large
canines that might interfere with chewing or gape (reviewed in
Greenfield, 1992). None of these hypotheses has received unambiguous support. Most recently, Hylander (2013) presented evidence that large canine teeth in male anthropoid primates are
maintained at a cost of mechanical efficiency in the masticatory
apparatus through a necessary increase in gape. In the absence of
selection to maintain large canines, selection should favor canine
reduction in order to allow a decrease in gape and greater mechanical efficiency in chewing. This model is consistent with
changes in the hominin masticatory complex indicating an
emphasis on heavier forces during chewing (Hylander, 2013).
At the same time, modern human canines are commonly seen as
functioning in concert with the incisor teeth for food acquisition.
This leads to the natural hypothesis that canine crown height
reduction throughout human evolution is linked to canine function.
Canine crown height reduction had already occurred in the earliest
hominins (White et al., 2009). A progressive change in canine
shape, involving a loss of honing and the elevation of the canine
shoulders, transitioning the tooth from an asymmetrical to symmetrical, diamond shape is seen originating with the earliest
known hominins, Ardipithecus, Sahelanthropus and Orrorin, and
progressing through A. anamensis to the condition seen in
A. afarensis (Haile-Selassie et al., 2004). Although is not known
whether their canines were used in similar ways to those of
514
Table 4
Comparative permanent tooth metrics. These numbers include values estimated for damaged or worn specimens, but are presented here with complete data for comparative
purposes.
Mesiodistal
Labio/Buccolingual
N
Mean
SD
Min
Max
N
Mean
SD
Min
Max
Maxillary dentition
I1
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
2
0
0
1
0
1
0
5
9.1
11.7
...
...
10.5
...
11.8
...
10.4
...
1.06
...
...
...
...
...
...
0.78
...
10.9
...
...
...
...
...
...
9.0
...
12.4
...
...
...
...
...
...
10.9
1
2
1
0
1
0
1
0
7
8.5
8.6
8.7
...
9.3
...
8.4
...
8.4
...
0.49
...
...
...
...
...
...
0.77
...
8.2
...
...
...
...
...
...
7.1
...
8.9
...
...
...
...
...
...
9.7
I2
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
0
1
0
0
0
2
0
6
6.3
...
5.8
...
...
...
7.8
...
7.4
...
...
...
...
...
...
...
...
0.68
...
...
...
...
...
...
7.8
...
6.6
...
...
...
...
...
...
7.8
...
8.2
1
0
2
0
0
0
2
0
7
7.5
...
6.5
...
...
...
7.8
...
7.1
...
...
0.71
...
...
...
0.49
...
0.56
...
...
6.0
...
...
...
7.4
...
6.2
...
...
7.0
...
...
...
8.1
...
7.9
C
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
2
4
0
0
0
3
0
10
9.9
11.2
11.6
...
...
...
10.4
...
9.8
...
0.78
0.80
...
...
...
1.04
...
0.53
...
10.6
10.5
...
...
...
9.6
...
8.9
...
11.7
12.4
...
...
...
11.6
...
10.4
1
2
3
0
1
0
3
0
10
10.2
10.7
9.9
...
11.0
...
10.8
...
10.9
...
0.71
1.01
...
...
...
1.50
...
0.94
...
10.2
8.8
...
...
...
9.8
...
9.3
...
11.2
10.8
...
...
...
12.5
...
12.4
P3
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
2
1
0
1
1
3
0
6
8.6
9.0
10.2
...
9.9
8.0
9.0
...
8.6
...
0.42
...
...
...
...
0.26
...
0.60
...
8.7
...
...
...
...
8.8
...
7.5
...
9.3
...
...
...
...
9.3
...
9.1
1
3
1
0
1
1
3
0
6
12.6
12.4
14.3
...
13.0
11.1
12.9
...
12.1
...
0.74
...
...
...
...
0.50
...
0.49
...
11.8
...
...
...
...
12.4
...
11.3
...
13.2
...
...
...
...
13.4
...
12.6
P4
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
3
1
0
1
3
5
0
12
8.2
7.7
12.0
...
8.8
8.8
9.2
...
9.1
...
0.46
...
...
...
0.30
0.28
...
0.82
...
7.2
...
...
...
8.5
9.0
...
7.6
...
8.1
...
...
...
9.1
9.7
...
10.8
1
0
1
0
1
1
1
0
10
13.0
...
14.2
...
13.9
13.1
12.5
...
12.4
...
...
...
...
...
...
...
...
0.88
...
...
...
...
...
...
...
...
11.1
...
...
...
...
...
...
...
...
14.5
M1
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
0
3
3
0
6
2
5
1
8
...
11.7
12.5
...
11.4
11.3
12.6
10.9
11.9
...
0.17
1.65
...
1.12
0.21
1.13
...
1.00
...
11.6
11.1
...
10.0
11.1
11.0
...
10.5
...
11.9
14.3
...
12.9
11.4
13.8
...
13.5
0
3
2
0
6
2
5
0
7
...
13.3
14.7
...
12.7
12.8
13.6
...
13.3
...
0.56
2.83
...
0.82
1.63
0.69
...
1.09
...
12.8
12.7
...
11.7
11.6
12.8
...
12.0
...
13.9
16.7
...
14.1
13.9
14.6
...
15.0
M2
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
1
3
2
0
4
3
3
0
5
12.4
13.4
12.8
...
12.5
12.7
12.8
...
13.3
...
0.68
1.20
...
0.81
1.42
0.12
...
0.74
...
12.9
11.9
...
11.4
11.4
12.7
...
12.1
...
14.2
13.6
...
13.2
14.2
12.9
...
14.1
1
3
2
0
4
3
4
0
5
13.5
14.8
15.0
...
14.3
14.8
14.9
...
14.7
...
0.10
1.56
...
1.56
1.45
0.22
...
0.86
...
14.7
13.9
...
12.9
13.1
14.6
...
13.4
...
14.9
16.1
...
16.3
15.7
15.1
...
15.8
515
Table 4 (continued )
Mesiodistal
N
M3
Labio/Buccolingual
SD
Min
Max
0
4
0
0
3
2
3
0
8
...
12.2
...
...
11.8
14.1
11.1
...
13.0
...
0.76
...
...
0.79
1.27
0.40
...
1.22
...
11.5
...
...
11.2
13.2
10.9
...
11.4
...
13.0
...
...
12.7
15.0
11.6
...
14.8
0
3
0
0
3
2
3
0
8
...
14.9
...
...
13.7
15.1
13.5
...
14.6
...
0.72
...
...
0.75
1.70
0.50
...
1.17
...
14.3
...
...
13.0
13.9
13.0
...
13.1
...
15.7
...
...
14.5
16.3
14.0
...
16.3
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
0
4
0
0
0
0
1
0
5
...
6.9
...
...
...
...
8.0
...
6.2
...
0.29
...
...
...
...
...
6.6
...
...
...
...
...
7.3
...
...
...
...
...
7.3
...
...
...
...
...
8.5
...
...
...
...
...
5.6
...
7.1
...
7.8
...
...
...
...
7.7
...
7.3
...
0.64
...
...
...
...
...
0.64
0
3
0
0
0
0
1
0
5
...
0.27
...
6.9
...
7.6
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
0
6
0
0
0
0
1
1
5
...
7.9
...
...
...
...
5.7
7.2
6.3
...
0.78
...
...
...
...
...
...
0.85
...
6.6
...
...
...
...
...
...
5.0
...
8.7
...
...
...
...
...
...
7.2
0
5
0
0
0
0
1
1
5
...
8.3
...
...
...
...
7.6
8.0
8.0
...
0.37
...
...
...
...
...
...
0.86
...
7.8
...
...
...
...
...
...
6.7
...
8.6
...
...
...
...
...
...
8.8
1.34
0.94
...
...
0.99
...
0.87
...
1.37
12.0
9.4
...
10.6
9.2
...
10.1
...
8.8
13.9
11.4
...
10.6
10.6
...
11.7
...
12.4
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
Mean
SD
Min
Max
N
Mean
Mandibular dentition
I1
I2
min
C
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
2
6
0
1
2
0
2
0
9
10.4
9.7
...
7.6
7.5
...
9.9
...
8.6
max
0.42
0.75
...
...
1.20
...
0.78
...
0.78
10.1
8.7
...
...
6.6
...
9.3
...
7.5
10.7
10.4
...
...
8.3
...
10.4
...
9.5
2
5
0
1
2
0
3
0
10
min
13.0
10.5
...
10.6
9.9
...
10.7
...
10.6
max
P3
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
3
7
0
1
1
1
5
1
19
9.8
9.8
...
8.9
9.3
7.5
10.2
9.3
9.2
0.35
0.34
...
...
...
...
0.25
...
0.81
9.4
9.4
...
...
...
...
10.0
...
7.9
10.1
10.4
...
...
...
...
10.6
...
11.4
3
6
0
1
1
1
5
1
19
13.2
11.0
...
10.0
11.3
9.5
11.3
11.2
10.4
0.46
0.64
...
...
...
...
0.83
...
0.94
12.8
10.2
...
...
...
...
10.6
...
8.9
13.7
12.0
...
...
...
...
12.6
...
12.6
P4
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
2
5
0
1
4
4
3
1
19
9.4
9.1
...
8.1
8.5
9.7
10.7
9.3
9.7
0.07
0.73
...
...
1.10
0.29
0.35
...
1.05
9.3
8.2
...
...
7.4
9.5
10.3
...
7.7
9.4
9.8
...
...
9.7
10.1
10.9
...
11.4
2
7
0
1
4
3
3
1
16
13.0
10.7
...
10.7
10.2
10.4
11.4
10.4
10.9
0.28
0.76
...
...
1.26
0.87
0.61
...
0.80
12.8
9.8
...
...
9.0
9.7
10.7
...
9.8
13.2
11.7
...
...
11.9
11.4
11.9
...
12.8
M1
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
2
10
0
0
1
3
4
2
21
13.4
12.7
...
...
11.9
12.6
13.5
13.40
12.9
0.57
0.99
...
...
...
0.40
0.39
...
1.05
13.0
10.5
...
...
...
12.1
13.1
13.1
10.1
13.8
13.8
...
...
...
12.8
14.0
13.6
14.8
2
10
0
0
1
2
4
2
15
12.5
12.0
...
...
10.9
12.3
13.2
12.3
12.4
0.64
1.08
...
...
...
0.49
0.56
...
0.81
12.0
10.0
...
...
...
11.9
12.6
12.2
11.0
12.9
13.5
...
...
...
12.6
13.9
12.4
13.5
(continued on next page)
516
Table 4 (continued )
Mesiodistal
Labio/Buccolingual
N
Mean
SD
Min
Max
N
Mean
SD
Min
Max
M2
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
0
8
0
1
2
4
3
2
25
...
14.3
...
13.5
12.5
14.6
14.7
14.6
14.2
...
1.04
...
...
1.20
1.21
0.23
0.64
1.33
...
13.0
...
...
11.6
13.7
14.4
14.1
12.1
...
15.9
...
...
13.3
16.4
14.8
15.0
16.5
0
9
0
0
3
4
3
2
21
...
13.7
...
...
11.8
13.3
13.6
13.2
13.4
...
0.86
...
...
1.46
1.98
0.35
0.21
1.10
...
12.6
...
...
10.2
12.0
13.3
13.0
11.1
...
15.1
...
...
13.0
16.2
14.0
13.3
15.2
M3
New Kanapoi
Published Kanapoi
Asa Issie
Fejej
Allia Bay
Woranso-Mille
Laetoli
Maka
Hadar
3
7
2
0
1
2
2
3
17
16.7
14.1
14.9
...
15.7
14.3
15.0
15.0
15.0
0.15
1.72
0.99
...
...
0.00
1.84
0.50
1.22
16.5
11.1
14.2
...
...
14.3
13.7
15.2
13.4
16.8
17.0
15.6
...
...
14.3
16.3
16.2
17.4
3
7
2
0
1
2
2
3
14
14.7
12.9
13.6
...
13.7
11.9
13.4
13.4
13.3
0.84
0.72
0.28
...
...
0.07
1.13
0.40
1.11
13.7
11.9
13.4
...
...
11.8
12.6
13.0
11.3
15.2
13.8
13.8
...
...
11.9
14.2
13.8
15.3
modern human canines, these changes in canine morphology and
occlusal relationships that were not accompanied by canine crown
height reduction should suggest change in canine function over
time (Ward et al., 2010; Manthi et al., 2012; see also; White et al.,
2006). Therefore, documenting the sequence of changes in canine
morphology over time may prove important, because if variation in
canine morphology reflects variation in canine function, it could
provide evidence for changes in diet or ingestive behaviors in early
hominins (Ward et al., 2010).
Furthermore, little attention has been paid to variation in canine
tooth root size. Early hominins clearly had large canine roots, while
canine root size in modern humans is relatively smaller (White
et al., 2006, 2009; Ward et al., 2010; Manthi et al., 2012). Large
roots might logically be expected for resisting large forces during
tooth function (Spencer, 2003). However, if canine root size is
dissociated from changes in crown size or morphology, then
changes in root size may be dictated by factors unrelated to canine
function (Ward et al., 2010; Manthi et al., 2012). Unfortunately, the
developmental and adaptive significance of canine root size is
currently unknown.
The new Kanapoi fossils support the hypothesis that canine
tooth roots in A. anamensis were large relative to those in
Figure 7. Maxillary and mandibular canine crown and root dimensions in Australopithecus anamensis compared with those of A. afarensis, Ardipithecus ramidus, Gorilla gorilla, Pongo
pygmaeus, Pan troglodytes and Homo sapiens. All data ln-transformed. Data in Tables 2 and 4e6. Position of newly described specimens noted on each figure. Maxillary and
mandibular canine crown heights are similar among all of the fossil hominins, but the canine roots of Australopithecus anamensis appear to be longer and more variable in length
than those of A. afarensis, especially in the mandibular dentition (see also Manthi et al., 2012).
517
Table 6
Comparative permanent canine tooth root dimensions.
MD
BL
Length
Cervical area, mm2
Volume, mm3
Maxillary canine root
Figure 8. The well-preserved and relatively unworn published mandibular canines
from Kanapoi shown in lingual view, (A) KNM-KP 47953, (B) KNM-KP 29284, (C) KNMKP 29286.
A. afarensis and later hominins (Ward et al., 2001, 2010; HaileSelassie, 2010; Haile-Selassie et al., 2010; Manthi et al., 2012)
(Fig. 7; Table 6). Robust canine roots have been noted in KNM-KP
29283 and from the alveolus of KNM-KP 29287 (Leakey et al.,
1995; Ward et al., 2001), as well as the Asa Issie specimen ARAVP-2/334 (White et al., 2006), the Fejej specimen FJ-4-SB-1
(Fleagle et al., 1991; Ward et al., 2010; Manthi et al., 2012) and
the deciduous specimen from Woranso Mille ARI-VP-1/190 (HaileSelassie, 2010; Haile-Selassie et al., 2010). Even so, the previously
described measurable A. anamensis specimens were only known to
vary in basal dimensions (mesiodistal and buccolingual) about as
Table 5
Canine crown heights and wear assessment.
Apical wear
Crown
height
(mm)
Maxillary canine
A. anamensis
KNM-KP 35839
A. afarensis
A.L. 199-1
A.L. 200-1a
A.L. 333-2
A.L. 333x-3
A.L. 400-1b
LH 3
LH 5
LH 6
Ar. ramidusa
ARA-VP 1/300
ARA-VP 1/1818
ARA-VP 6/1
ARA-VP 6/500
A. anamensis
KNM-KP 47953
KNM-KP 29284
KNM-KP 29286
KNM-ER 30731
A. afarensis
A.L. 198-1
A.L. 333-90
A.L. 333w-58
A.L. 400-1a
LH 3
BMNH 18773
A. ramidusa
ARA-VP 1/300
ARA-VP 6/500
a
15.2
Unworn
9.2
12.7
worn, strong blunting wear
Worn, moderate blunting wear, not as
strong as LH 5
Worn, strong blunting wear.
Slight blunting, tip sharp from convergent facets
Worn, moderate blunting, dentine exposed.
Unworn
Worn, moderate blunting wear.
Very slight apical wear.
10.2
15.4
12.5
14.2
10.6
14.0
14.5
14.9
14.6
13.5
Unworn
Corrected for wear
Unworn
Rough estimate
Mandibular canine
15.7
14.1
14.5
10.0
Slight apical wear
Unworn, crown nearly complete, no root.
Slight apical wear
Worn, strong blunting wear
10.9
11.5
17.0
12.0
13.3
14.0
Worn, moderate blunting, dentine exposed.
Worn, strong blunting wear.
Worn, strong blunting wear, crown fractured.
Worn, moderate blunting
Unworn
Worn, moderate wear, hard to assess because
of chipped enamel
16.6
14.4
Unworn
Corrected for wear
Data from Ar. ramidus kindly provided by TD White, B Asfaw and G Suwa.
A. anamensis
KNM-KP 29283
KNM-KP 30498
KNM-KP 35839
KNM-KP 47952
N
Mean
SD
Min
Max
8.8
7.9
10.0
8.1
4
8.7
0.95
7.9
10.0
10.8
9.0
10.9
9.1
4
10.0
1.04
9.0
10.9
28.4
.
.
23.3
3
25.6
2.6
23.3
28.4
95.0
71.1
109.0
73.7
4
87.2
18.05
71.1
109.0
2699
.
.
1717
2
2208
694
1717
2699
A. afarensisa
A.L. 199-1
A.L. 200-1
A.L. 333-2
A.L. 333x-3
A.L. 400-1b
A.L. 487-1c
A.L. 763-1
Garusi 1
LH 5
LH 6
LH 1
N
Mean
Min
Max
SD
8.1
10.4
10.5
10.9
9.9
.
.
.
7.2
10.0
.
7
9.6
7.2
10.9
1.38
6.2
6.8
7.3
8.2
6.8
.
.
.
7.2
7.5
.
7
7.1
6.2
8.2
0.63
.
.
.
27.5
19.1
28.1
22.3
22.0
18.8
.
21.5
7
22.8
18.8
28.1
3.71
50.2
70.7
76.7
89.4
67.3
.
.
.
51.8
75.0
.
7
68.7
50.2
89.4
13.92
.
.
.
2458
1286
.
.
.
975
.
.
3
1573
975
2458
782
78.8
48.4
60.9
87.3
88.9
Mandibular canine root
A. anamensis
KNM-ER 30731
KNM-ER 30750
KNM-KP 29281
KNM-KP 29286
KNM-KP 29284
KNM-KP 29287
KNM-KP 47951
KNM-KP 47953
FJ-4-SB-1
N
Mean
SD
Min
Max
7.8
5.9
7.0
7.7
7.8
8.9
10.3
9.8
7.6
9
8.1
1.37
5.9
10.3
10.1
8.2
8.7
11.4
11.4
.
13.8
10.0
10.6
8
10.5
1.75
8.2
13.8
.
.
.
.
.
20.2
31.8
.
28.6
3
26.9
5.99
20.2
31.8
142.1
98.0
80.6
8
85.6
27.86
48.4
142.1
.
.
.
.
.
.
4520
.
2304
2
3412
1567
2304
4520
A. afarensisa
A.L. 128-23
A.L. 198-1
A.L. 277-1
A.L. 333-103
A.L. 333-90
A.L. 333w-10
A.L. 333w-58
A.L. 400-1a
LH 14
BMNH 18773
N
Mean
SD
Min
Max
5.8
6.4
8.0
7.5
7.8
7.6
9.5
6.5
7.5
7.1
10
7.4
1.02
5.8
9.5
8.8
8.9
11.1
10.5
10.4
11.5
.
9.2
10.0
10.1
9
10.1
0.94
8.8
11.5
.
.
.
.
21.0
24.3
.
.
23.1
.
3
22.8
1.67
21.0
24.3
51.0
57.0
88.8
78.8
81.1
87.4
.
59.8
75.0
71.7
9
72.3
13.56
51.0
88.8
.
.
.
.
1704
2124
.
.
1733
.
3
1853
235
1704
2124
All data in mm. MD ¼ mesiodistal, BL ¼ buccolingual, area ¼ MD BL,
volume ¼ area length.
a
Data from A. afarensis kindly provided by W.H. Kimbel.
518
much as do those of A. afarensis and later hominins (Ward et al.,
1999a, 2001).
The most striking of the new Kanapoi specimens in this regard is
KNM-KP 47951, which has the largest canine tooth root known for
any early hominin, in length, cervical dimensions and volume, even
when compared with Ar. ramidus (Figs. 1 and 7; Table 6) (Manthi
et al., 2012). This specimen increases the observed range of variation in length and occlusal dimensions of A. anamensis mandibular
canine teeth, and also in overall size (Manthi et al., 2012). In
addition, the maxillary canine KNM-KP 47952 also has a long root,
supporting the hypothesis that both maxillary and mandibular
canine tooth roots were larger on average in A. anamensis than in
A. afarensis.
Long, large canine tooth roots also are seen in Ar. ramidus and
extant great apes (Fig. 7), strongly suggesting that this is a primitive
trait for the hominin clade. Australopithecus anamensis appears to
have retained this primitive root size. Only with the appearance of
A. afarensis does mandibular root size appear to have reduced from
the primitive condition for hominins (Ward et al., 2010; Manthi
et al., 2012) and this change may be related to changes in maxillary and mandibular profiles in the region of the canine juga (Ward
et al., 2010).
The new fossils support the observation that A. anamensis and
A. afarensis do not differ in crown height, despite their differences
in canine root volume (Manthi et al., 2012) (Fig. 7; Tables 5 and 6).
The canines of both species are equivalent in buccolingual breadth,
but A. anamensis maxillary canines are longer mesiodistally than
those of A. afarensis. This maxillary basal canine crown profile of
A. anamensis more closely resembles that of Ar. ramidus and extant
apes, whereas that of A. afarensis resembles humans (Fig. 9; Tables 4
and 6) (Manthi et al., 2012). This change in basal shape appears to
have accompanied a change in crown morphology with A. afarensis,
which has high crown shoulders in the maxillary canine and a
broader, more symmetrical lingual profile in the mandibular canine
that mirrors the pattern seen in later hominins (Ward et al., 2001,
2010; White et al., 2006; Manthi et al., 2012). No differences are
seen in basal dimensions of the mandibular canines among any of
the taxa included here.
Relative to the size of the other teeth, the new Kanapoi associated dentitions do support the hypothesis that the basal
dimensions of the A. anamensis canine teeth are larger relative to
sizes of the postcanine teeth (Fig. 10) (Ward et al., 1999a,b, 2001;
Manthi et al., 2012). These ratios may reflect not only reduction
in basal canine dimensions, but slight expansion of the postcanine
dentition. Without variables outside the dentition, the magnitude
of change in these cannot be assessed. Nonetheless, there does
seem to be a proportional difference in relatively canine-postcanine
tooth size between A. anamensis and A. afarensis.
Thus, it is now apparent that the canine crown height
reduction that occurred in hominin evolution did not result in
an accompanying change in crown morphology or in basal
crown profile. Instead, even though crown size had reduced, the
change in crown shape (in terms of the basal proportions of the
teeth) from an ape-like to human-like condition was only achieved with A. afarensis, along with a reduction in canine root
size (Manthi et al., 2012). This shape change in basal crown
proportions occurred independently of the loss of the canine
honing mechanism (which occurs early in hominin evolution),
and appears to reflect an independent change in canineeP3
occlusion, increasing transverse contact area between maxillary
and mandibular teeth, most logically due to increased use of the
canine in food acquisition or preparation. This suggests that an
associated change in function occurred between A. anamensis
and A. afarensis, and not with the origin of Australopithecus
(Ward et al., 2010; Manthi et al., 2012). It is also clear that shape
changes in the canine-premolar complex did not accompany
selection for reduced canine crown height, which was already
diminished in earlier hominins (Ardipithecus, Orrorin and
Sahelanthropus). It is also apparent that a reduction in canine
root size did not accompany a reduction in crown height, but
did accompany a change in crown morphology. If changes in
root size are linked to canine function, then this further supports the notion of a shift in canine function in the transition
from early A. anamensis through A. afarensis.
Premolars The new Kanapoi mandibular premolars are generally
larger than the previously published specimens, and represent
the largest known for A. anamensis or A. afarensis (Table 4).
Morphologically, though, they display the classic features
associated with A. anamensis.
Figure 9. Scatterplot of ln-transformed buccolingual and mesiodistal dimensions of maxillary and mandibular canine tooth crowns. Data in Tables 2 and 4. Australopithecus
anamensis basal maxillary basal canine crown shape is most like that of Ardipithecus ramidus and extant apes, but those of Australopithecus afarensis are mesiodistally shorter like
those of humans. No differences in basal profile are evident among taxa for the mandibular canines.
Figure 10. Ratios of basal mandibular canine crown basal area quantified as
mesiodistal buccolingual breadths divided by crown basal areas of the postcanine
teeth to demonstrate relative size of the canine compared with each of the other teeth.
The new fossils support the observation that Australopithecus anamensis canines are
slightly larger relative to the sizes of the postcanine teeth than those of A. afarensis (see
also Ward et al., 1999a,b, 2001).
The P3 morphology of the new Kanapoi fossils closely resembles
the other Kanapoi specimens (Fig. 11). Australopithecus anamensis is
distinguished from A. afarensis and later hominins by the presence
of a single dominant protoconid on P3 that is located roughly in the
buccolingual center of the crown, with the metaconid existing only
as a small cuspule along the lingual ridge. The mesial fovea opens
lingually, rather than occlusally, due to the weakly developed and
notched marginal ridge, with no buccal grooves or ridges, similar to
KNM-KP 29284 (Ward et al., 2001). KNM-KP 47953 displays among
the most extreme examples of this morphology, with a centrally
placed protoconid with strongly sloping buccal face, and almost
nonexistent metaconid. It has a more ovoid, or buccolingually
elongate, shape in occlusal view than previously known specimens
due to the more sloping buccal face of its protoconid. KNM-KP
47951 appears to have been similar, although the extensive
missing enamel precludes detailed comparisons of its cusp
morphology. It probably had a slightly larger metaconid than KNMKP 47953, but no more than seen in KNM-KP 29281, KNM-KP 29284
or KNM-KP 29286 (Fig. 12).
These shape differences are reflected in the basal profile of the
tooth, in which the A. anamensis P3s tend to be more ovoid in
outline than those in A. afarensis (Fig. 11; Table 4). This is functionally linked to the mesiodistally longer maxillary canine in
A. anamensis compared with that of A. afarensis (see also Kimbel
519
Figure 11. The well-preserved published P3s from Kanapoi compared with the new
specimen presented here. (A) KNM-KP 47953, (B) KNM-KP 29281 (left side, shown in
reverse for comparison) (A. anamensis holotype), (C) KNM-KP 29286, (D) KNM-KP
29287, (E) KNM-KP 29284 (LP3 reversed), (F) KNM-KP 30500 (left side reversed).
KNM-KP 47951 not figured here because of significant missing enamel.
et al., 2006; White et al., 2006; Ward et al., 2010; Manthi et al.,
2012). There is no difference in basal profile of the mandibular
canine or maxillary P3 between these species, however (Fig. 13; see
also Fig. 9), suggesting that observed shape changes are localized to
the honing pair of teeth (maxillary canine and mandibular P3)
(Manthi et al., 2012). These fossils reflect a change in shape of the
honing teeth from A. anamensis to A. afarensis, suggesting perhaps
selection on the use or function of these teeth throughout this
lineage. The human-like basal profile of the A. afarensis honing pair
of teeth, therefore, was not a feature that characterized the earliest
Australopithecus, nor did this shape change accompany the reduction in canine crown height noted for all hominins (including
Ardipithecus, Orrorin and Sahelanthropus) (Manthi et al., 2012).
The KNM-KP 47953 P4 has a more mesially-situated metaconid
and transverse ridge than previously described specimens from
Kanapoi (KNM-KP 29284 and KNM-KP 29281), with a more distobuccally extended distal marginal ridge and basal bulge along the
distal fovea, giving this contour an especially ovoid curve in
occlusal view (Fig. 13). Overall, however, the morphology compares
well with the previously described specimens.
The new Kanapoi hominins display a range of premolar root
configurations, mirroring the polymorphism in roots seen in the
Hadar sample (Ward et al., 1982; Kimbel and Delezene, 2009).
KNM-KP 47951 has widely divergent roots on P3, and also on P4
(Fig. 1). There is a single flaring mesiobuccal root, and a thick and
grooved distolingual root that is bifurcated at its tip. It is most
similar to the three roots seen on the P3 of KNM-KP 29281 (Ward
520
Figure 12. Scatterplots of ln-transformed tooth diameters for the maxillary and mandibular canines and third premolars. Diameters quantified as mesiodistal and buccolingual for
all except the mandibular premolar, which was measured as maximum and minimum diameters to account for the slight differential rotation of this tooth in the jaw among taxa.
Both the maxillary canine and P3 are relatively longer in Australopithecus anamensis than those of A. afarensis, but no apparent differences are seen in the mandibular canine and P3.
et al., 2001). The P4 root configuration is similar in this individual. In
KNM-KP 47953, the premolar roots are more closely apposed
(Fig. 3). These essentially appear to be two plate-like roots fused
together, and have the external configuration of a Tome’s root
(Wood et al., 1988). This variation might appear excessive for a
species, but still does not exceed that seen within A. afarensis,
which ranges from three splayed roots in LH 24 to the Tome’s roots
of A.L. 145-35, A.L. 288-1 and A.L. 400-1a (Kimbel and Delezene,
2009). The Kanapoi sample demonstrates that the premolar root
polymorphism seen at Hadar extends back to A. anamensis.
The maxillary premolars are also similar in size and morphology
to other known Kenyan A. anamensis (Fig. 14). KNM-KP 47954 has
less strongly sloping lingual and buccal sides of the crown than
KNM-ER 30745. It is more symmetrical in occlusal profile than the
P3 from KNM-KP 30498. It is larger than KNM-KP 29283, KNM-KP
31726, and KNM-KP 49388. Overall, though, as with the other
postcanine teeth, the new specimens expand the range of observed
variation in tooth size and morphology only to a very minor extent,
as might be expected when adding to samples this small.
Molars The new fossils expand the known sample of A. anamensis
teeth. In most cases, the new specimens do not expand the size
range of dental dimensions previously represented in the
A. anamensis samples from Kenya or Ethiopia (Table 4). The
exceptions to this are the M3s, in which case all three new
specimens exceed the buccolingual breadths of previously known
M3s from Kanapoi (n ¼ 6), and of the eleven M3s known from all
A. anamensis site samples. Only one specimen from Asa Issie is as
broad buccolingually as one of the new Kanapoi fossils. In terms
of mesiodistal length, however, the new Kanapoi fossils fall
within the range of previously observed values.
The single new M2 (KNM-KP 52120) is buccolingually narrower
than any other from Kanapoi, although its mesiodistal length is
comparable with other specimens (Table 4). There is no reason to
suspect that these slight metric differences represent anything
other than individual variation in this small sample, but increasing
the number of specimens known will be necessary to explore this
possibility further. Given the small sample sizes involved, it is to be
expected that the addition of new specimens will increase metric
variation to some degree.
In overall tooth shape, the new molars resemble the previously
known A. anamensis fossils (Figs. 15e18). The buccal and lingual
sides of the molars slope strongly from cervical to occlusal margin,
and the crowns appear relatively low as compared with A. afarensis
teeth (see Ward et al., 2001). Protostylids and Caribelli’s features
are common in other A. anamensis teeth, and KNM-KP 47953 has
protostylids on its preserved molars. None is apparent on the M2 of
KNM-KP 47955. The M3 KNM-KP 47957 is missing too much
enamel to have preserved these features.
521
Figure 15. The well-preserved published M2s from Kanapoi compared with the new
specimen presented here. (A) KNM-KP 52120, (B) KNM-KP 34725G (right side, reversed
for comparison).
Figure 13. The well-preserved published P4s from Kanapoi compared with the new
specimen presented here. (A) KNM-KP 47953, (B) KNM-KP 29281 (left side, shown in
reverse for comparison) (A. anamensis holotype), (C) KNM-KP 29287 (left side
reversed), (D) KNM-KP 30500, (E) KNM-KP 29286 (left side reversed). KNM-KP 47951
not figured here because of significant missing enamel.
recovered for A. anamensis. Morphologically, the new fossils do not
appreciably extend the range of observed variation in A. anamensis
from Kanapoi, with the notable exception of the large canine tooth
root of KNM-KP 47951. This specimen represents the largest canine
tooth root in the fossil hominin record, even when Ardipithecus is
considered (Manthi et al., 2012).
These fossils support the morphological distinctiveness of the
early A. anamensis fossil samples relative to earlier hominins and
even to the later A. afarensis. All of the Kanapoi hominins share a
distinctive morphology of the canineepremolar complex, with
mesiodistally longer honing teeth and large canine tooth roots. It is
now becoming apparent that the classic hominin characteristic of
the loss of projecting canine teeth and canine dimorphism did not
Summary
The new Kanapoi hominin fossils increase the sample of teeth
known from this earliest Australopithecus, and provide new insights
into the morphology in this taxon. The rapid depositional context in
which most of these fossils occur suggests that the observed variation represents population variation with minimal time averaging.
The fossils do provide evidence of some larger individuals, or at
least larger teeth, but in no case does the observed size variation
exceed that of a single species. The mandible is the smallest yet
Figure 14. The well-preserved published maxillary premolars from Kanapoi compared
with the new specimen presented here. P3s: (A) KNM-KP 47954, (B) KNM-KP 30498C,
and P4s: (C) KNM-KP 49388, (D) KNM-KP 31726 (right side, reversed for comparison).
specimen presented here. (A) KNM-KP 47955, (B) KNM-KP 29281, (C) KNM-KP 29286,
(D) KNM-KP 30500, (E) KNM-KP 34725R (right side, reversed for comparison).
522
specimen presented here. (A) KNM-KP 47943, (B) KNM-KP 29281 (left side, reversed
for comparison), (C) KNM-KP 29286, (D) KNM-KP 29287, (E) KNM-KP 30500 (left side
reversed), (F) KNM-KP 34725T (left side reversed).
specimens presented here. (A) KNM-KP 47953 left side, (B) KNM-KP 47953 (right side,
reversed for comparison), (C) KNM-KP 47957, (D) KNM-KP 29281, (E) KNM-KP 29286
(right side reversed), (F) KNM-KP 30500 (right side reversed).
Acknowledgements
result from a single event, but instead occurred in several steps.
Canine crown heights reduced first, followed only later by a reduction in root size and mesiodistal tooth lengths of the canines and
lower third premolars, and a change in canine crown form (Ward
et al., 2001, 2010; White et al., 2006). This suggests a significant
adaptive change in canine function from A. anamensis to A. afarensis.
As more Kanapoi fossils are discovered, it is becoming increasingly apparent that earliest Australopithecus was not identical to
A. afarensis (see also Leakey et al., 1995, 1998; Ward et al., 1999a,
2001, 2010; Kimbel et al., 2006; White et al., 2006). Based on the
more recent, better-known A. afarensis, the origin of Australopithecus is thought to involve the appearance of committed
terrestrial bipedality, adaptations for masticating a tough diet,
substantial body size dimorphism with minimal canine dimorphism, slightly expanded brain, and use of more open habitats
compared with earlier hominins (Ardipithecus, Orrorin and Sahelanthropus). The few known A. anamensis fossils differ from
A. afarensis, however, suggesting that some of these traits were not
coupled (Kimbel et al., 2006; Haile-Selassie, 2010; Ward et al., 2010;
Manthi et al., 2012). Determining which traits characterized the
origins of the genus is key for understanding why and how Australopithecus evolved. Only the recovery of more fossils will allow
us to explore these possibilities further, and test the hypothesis
about possible morphological evolution within early Australopithecus and better understand the adaptations of the earliest
Australopithecus.
The authors thank the West Turkana Paleontology Project crew
for their hard work, skill and dedication. We thank the Government
of Kenya for permission to conduct research, and the curators and
staff of the National Museums of Kenya, Turkana Basin Institute,
Cleveland Museum of Natural History, National Museum of Natural
History and Royal Museum of Central Africa for access to collections
in their care and assistance. We would also like to thank Gen Suwa,
Tim White, Berhane Asfaw and William Kimbel for data, John
Fleagle and William Kimbel for casts, and William Kimbel, Meave
Leakey, Milford Wolpoff, Alan Walker, Bernard Wood, Luke Delazene, Yohannes Haile-Selassie, Scott Simpson, and John Fleagle for
helpful comments and discussion. This project was supported by
the LSB Leakey Foundation, Turkana Basin Institute, Paleontological
Scientific Trust (PAST) of South Africa, and Wenner Gren Foundation for Anthropological Research.
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New fossils of Australopithecus anamensis from Kanapoi, West

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