Genesis: Paleozoica - The Origins Museum Institute

The Origins Museum Institute
presents
Paleozoica
From The Genesis Exhibit
Drawn from the world’s foremost fossil collections, the
unprecedented treasury of fossil casts known as THE
GENESIS EXHIBIT brings together into one exhibition some
of the most exciting finds in the history of paleontology from
over a century of worldwide excavations, exhibited as
sculptural works of art.
Spanning
4.6 billion years in scope, from the earliest
invertebrate marine life, through the Triassic, Jurassic, and
Cretaceous
dinosaurs
to
sabre-toothed
cats,
this
comprehensive collection from the Texas Museum of Natural
History’s internationally acclaimed THE GENESIS EXHIBIT
dramatically illustrates the awesome story of prehistoric life on
Earth.
Displaying
casts of rare fossils from the Americas,
Europe, Asia, Africa, and Australia, this prestigious collection
includes skeletons, skulls, claws, and eggs gathered from such
revered museums as the Smithsonian Institution, The
American Museum of Natural History, The Royal Ontario
Museum, and the Carnegie Museum, as well as many others.
This famed traveling exhibition is now available direct
from its celebrated showings at the World Trade Centers in
Boston, San Juan, and Taichung, the Fernbank Museum of
Natural History in Atlanta, the Dinosaur Discovery Center at
Colorado National Monument, The Texas Museum of Natural
History in Austin, and the Natural History Museum of El Paso,
where it was admired by millions of people. These compelling
natural artifacts, rarely seen outside of their respective
museums, are on view together exclusively in THE GENESIS
EXHIBIT and its touring collections.
As
art sometimes reflects nature, so, in turn, does nature
occasionally reflect art. These bones, and teeth, and talons tell
a story. A story of living molecules beginning to reproduce
themselves in an ancient sea and gradually crawling out onto
dry land. A story of dynasties of giant, complex creatures
dominating land and sea and sky, descended from the tiniest
and simplest of ancestors in an incredible chain of
reproduction and diversification. A story of strength and
ferocity and gentleness in titanic proportions. In other words,
the story of the ingenious adaptability of life in the face of
death. For in this struggle we see dramatic evidence of
nature’s unrelentingly exploratory forces at work. Viewed as a
progression of sculptures, one could say that a distinct style
emerges early and gradually refines itself over millions of years,
sometimes simple, sometimes quite baroque, and usually
astonishingly practical. A story without words, cleft by
humankind from stone.
Eskimo Nebula (NGC 2392) NASA Hubble photograph
THE PRECAMBRIAN ERA
from 4.6 billion to 570 million years ago
During the first 3 billion years of the planet’s existence there was
no ozone layer in the atmosphere to shield the land from the sun’s
ultraviolet rays. Life on Earth began in the dark ocean depths
where these rays, destructive to the delicate DNA molecules that
are exclusive to living organisms, could not penetrate. The early
self-reproducing one-celled organisms, known as procaryotes,
were so primitive that they did not possess a distinct cell nucleus.
About a billion years ago, these simple asexual cells gave rise to
the more complex eucaryotes which possess a cell nucleus along
with the capacity for sexual reproduction, which allowed for the
exchange of genetic material and, as a result, evolutionary
variability between organisms.
As some of these early microorganisms began producing oxygen,
the oceans and the atmosphere gradually became abundant with it.
A reaction between lightning and the oxygen in the atmosphere
slowly produced a layer of ozone gas which, in turn, gradually
began to filter out enough of the harmful ultraviolet rays to permit
habitation of the shallower waters and, subsequently, the land.
In Western Australia the fossilized remains of simple
microorganisms (such as bacteria) have been found in rocks that
are close to 3.5 billion years old. This was the Archean Era, also
known as the Precambrian period, which lasted until about 570
million years ago. The earliest organisms visible to the naked eye
did not appear until about 700 million years ago. During the Late
Precambrian, the formation of Gondwanaland united the modern
continents of the Southern Hemisphere, providing warm, shallow,
offshore environments where complex living organisms first arose.
1. Kingdom Procaryotae Incertae Sedis
Archaeoscillatoriopsis grandis
Archaeotrichion septatum
Primaevifilum amoenum
Early Precambrian, Australia
The most ancient direct evidence of life on earth was found in
Western Australia, where outcroppings of dense, sedimentary chert
contain the oldest undoubted microfossils known. Paleobotanist J.
William Schopf and his colleagues discovered several species of
benthic, primordial microbes including the probable cyanobacteria
(blue-green
algae)
Archaeoscillatoriopsis
grandis
and
Primaevifilum amoenum. Flimsily organized in mucilage, this
microbial assemblage attests to the extreme antiquity of oxygenproducing, photosynthetic physiology. Interpreted as probable
bacteria, Archaeotrichion septatum closely resembles modern
forms, confirming that anoxic bacteria were already abundant at
this early phase of biotic history.
Heralding the appearance of one-celled organisms, these sinuous
relics of once living procaryotic cells are dated at 3.465 billion
years, astounding evidence of an evolving, biotic continuum
spanning from the Early Archean Rocks from the nearby planet
Mars, bearing controversial geological anomalies of similar age
and form to confirmed terrestrial fossil bacteria, have been found
lying on top of the ice in Antarctica as cosmic debris.
Microfossiliferous rock sample and photomicrographs of cellularly
preserved specimens from the Early Archean Apex Basalt courtesy
of J. William Schopf. British Museum of Natural History.
2. Kingdom Monera
Phylum Cyanophyta
Collenia versiformis
Early Precambrian, Minnesota
The oldest known visible structures produced by living organisms,
stromatolites (“Cushion Stones”) are the fossilized remains of
slimy mounds or mats formed by the cementing (in distinctive
layers) of calcium carbonate sediments to the filmy, gelatinous
secretions of cyanobacteria, also known as blue-green algae.
Appearing in the fossil record 2.5 billion years ago, these
primordial colonies of photosynthetic microorganisms formed
great reefs in the warmer lakes and shallow seas of the
Precambrian. This sliced cross-section of the 2-billion-year-old
stromatolite Collenia reveals an algae formation twisted by floods
or volcanic activity. Private collection.
3. Kingdom Monera,
Phylum Cyanophyta
Collenia tubiformis
Late Precambrian, Montana
Containing chlorophyll, the catalyst which employs sunlight for
the conversion of water and carbon dioxide into food, the
enormous bacterial communities that built the stromatolites were
responsible for the abundance of oxygen both in the oceans and the
atmosphere, releasing it as metabolic waste. The algae that
flourished in the ancient seas also gave rise to the first plants.
Because the growth of these mounds of algae are an indication of
the water depths at high tide, such fossils provide evidence of a
time when the moon was much closer to the Earth. This Collenia
tubiformis specimen is over a billion years old. Private collection.
THE EDIACARA FAUNA
Scattered throughout the world, the first isolated communities of
multicellular animal life in the oldest inhabited seas appear to have
developed around the oxygen enriched oases of algal colonies from
700 to 600 million years ago. Discovered in the Ediacara Hills of
South Australia by Sir Reginald Sprigg in 1947 and known as the
Ediacara fauna, these rare Precambrian life forms are the most
primitive known. With cells organized into actual tissue and
equipped with rudimentary vascular systems, they probably
absorbed oxygen through their skin, tending to prevent their
becoming too thickly-tissued, unlike any animals that have
succeeded them.
Evidence of glaciation and a meteorite impact correspond to the
disappearance of this fauna from the fossil record, separating the
Precambrian Era from that of the Paleozoic. Although these early
animal prototypes did not survive into the Paleozoic, they appear
to have produced a variety of survivors including segmented
annelid worms (the presumed ancestors of the arthropods), as well
as cnidarians (jellyfish), and echinoderms (the presumed ancestors
of the chordates). The red coloration of the rocks containing the
imprints of these dawn animals is attributed to the oxidation of iron
in the sand of the ancient tidal flats as a result of the growing
abundance of the corrosive gas in the atmosphere. From the Late
Precambrian Ediacaran deposits of Flinders Range, South Australia.
University of Adelaide.
4. Kingdom Animalia,
Phylum Cnidaria
Rugoconites tenuirugosus
Late Precambrian, South Australia
Among the first metazoans to arise from protozoan ancestry were
the coelenterates (“Hollow Entrails”), or cnidarians. From sea
anemones and corals to jellyfish, these marine organisms are
known for their great beauty and diversity. As with modern forms,
many primitive varieties possessed poisonous stinging cells
capable of paralyzing prey on contact. Among the oldest and most
primitive of such creatures are the primordial medusae (or jellyfish)
of the Precambrian, whose colorful modern descendants are
virtually unchanged. Although their soft structures consisted
mainly of water, some ancient jellyfish such as Rugoconites (the
oldest known true medusoid jellyfish) were durable enough to
fossilize after washing onto the beach and drying in the sun.
Remarkably preserved, this ancient impression is more than half a
billion years old.
5. Phylum Cnidaria, Class Cubozoa
Kimberella quadrata
Late Precambrian, South Australia
6. Phylum Cnidaria, Class Scyphozoa
Ediacaria flindersi
Late Precambrian, South Australia
Beginning life as a tiny polyp attached to the underside of a rock,
followed by metamorphosis into a medusa, this archetypic
cubozoan (preserved in side view) possessed an elongate, squareedged umbrella. Commonly known as sea-wasps, this extant form
of deadly, long-tentacled jellyfish is the most venomous predator
on Earth, capable of inflicting instantaneous death.
Long regarded as one of the earliest jellyfishes, the welldocumented Ediacaria may have lived a sedentary existence on the
sea floor with its short tentacles extended upwards, an assumption
resulting from the discovery of an anemone-like orifice on some
Ediacaria specimens.
7. Kingdom Animalia,
Phylum Annelida
Dickinsonia costata
Late Precambrian, South Australia
A bizarrely flattened and discoidal segmented marine worm
indigenous to the primordial tidal flats of southern Australia,
Dickinsonia was usually quite small, although on occasion some
grew to extraordinary lengths. Already a diverse group by the end
of the Precambrian, the annelid worms presumably gave rise to the
segmented arthropods.
8. Phylum Annelida,
Class Polychaeta
Spriggina floundersi
Late Precambrian, South Australia
Well-documented in the fossil record, Spriggina attests to the
diversity of the early annelids, whose descendants (including
earthworms and leeches) are still alive today. A flattened,
segmented marine worm, the extraordinary preservation of most
Spriggina specimens reveals a small, muscular creature with
relatively simple nervous and excretory systems. Owing to the
enlargement of its head and other physical similarities, it has been
suggested that this annelid may have been ancestral to the trilobites.
9. Kingdom Animalia,
Phylum Echinodermata
Tribrachidium heraldicum
Late Precambrian, South Australia
Representing the echinoderms in the Precambrian community is
the tiny, coin-shaped fossil known as Tribrachidium, though it is
such a primitive form that it exhibits only 3 of the 5 symmetrical
body sections that distinguish true echinoderms such as starfish,
sea urchins, and crinoids. Within this group the origin of the
chordates, the soft-spined ancestors of the vertebrates, is theorized
to have occurred. If Tribrachidium is an echinoderm, then it may
be evidence of the presence of the ancestors of the vertebrates in
the oldest known seas.
10. Phylum Cnidaria, Class Anthozoa
Charniodiscus opositus
Late Precambrian, South Australia
Rising like delicate seaweed plumes from the bulbous holdfasts
anchoring them to the substrate and swaying with the gentle
currents, Pennatulaceans resembling Charniodiscus were
widespread throughout the world, from Newfoundland to England
and Australia. This group exhibits distinguishing characteristics
that still persist in living pennatulaceans.
11. Phylum Cnidaria,
Order Pennatulacea
Charniodiscus arboreus
Late Precambrian, South Australia
Sea pens, or Pennatulaceans, are soft corals that live a benthic
existence attached to the sea floor. Those of the earliest inhabited
seas were large, frondose structures that lived by filtering tiny
particles of food from the warm waters of the shallow tidal flats.
12. Phylum Cnidaria,
Order Pennatulacea
Glaessnerina grandis
Late Precambrian, South Australia
The last of such featherlike creatures to be found in the Late
Ediacaran deposits, Glaessnerina was the nearest to modern forms of
sea pens. Because conditions favorable to fossilization persisted past
the point of Glaessnerina’s disappearance from the Precambrian
deposits, it is assumed that they declined to the point of extinction.
THE EARLY TO MIDDLE
PALEOZOIC ERA
from 570 million to 345 million years ago
Known as the Cambrian explosion, about 570 million years ago
dense populations of complex sea creatures suddenly appeared,
marking the beginning of the Cambrian period and of the Paleozoic
Era. First discovered in northern Wales (once known as Cambria),
fossils of this period document the early establishment of all
modern animal phyla, followed by the emergence of primitive
jawless fishes in the Ordovician (500 million years ago), named for
an ancient Celtic tribe of western Wales, the Ordovices, whose
farms were built on rocks rich in fossils.
13. Phylum Cnidaria,
Order Pennatulacea
Cyclomedusa davidi
Late Precambrian, South Australia
Long regarded as ancestral jellyfish, the discoidal Cyclomedusae
are now considered by the Australian scientists who have studied
them for years to have been the holdfasts of other animals that
lived attached to the substrate, the sea pens.
Following the Ordovician, rock formations found along the border
of Wales and England derive their name from the savage tribe of
Silures that inhabited the region during the Roman occupation.
Throughout the Silurian (435 million years ago), plants and
insects invaded the land. In the Devonian (395 million years ago),
characterized by fossils first discovered in Devon, England,
advanced lobe-finned fishes and tetrapod amphibians appeared in
the freshwater streams of the newly formed Old Red Sandstone
Continent which united Greenland with Europe and North America.
At the close of both the Ordovician and Devonian periods,
Gondwanaland drifted over the south pole, triggering the onset of
glacial episodes accompanied by mass extinctions of marine life.
15. Phylum Echinodermata,
Class Eocrinoidea
Gogia kitchnerensis
Middle Cambrian, Utah
14. Phylum Arthropoda,
Order Agnostida
Ptychagnostus
Middle Cambrian, Utah
Already well-established by the dawn of the Cambrian, this ancient
order of minuscule, ancestral trilobites must have evolved in the
primordial seas of the Precambrian. Although most agnostids
(“Unaware Ones”) were not equipped with eyes, these early
creatures, less than half an inch in size, persisted for some 135
million years. Ptychagnostus (“Folded Unaware One”),
characterized by their minute size, lack of eyes and greatly reduced
thoracic (mid-section) segments, lived a planktonic, drifting
lifestyle in dark, murky marine environments which apparently
were not conducive to vision. They became extinct around the
close of the Ordovician. Private collection.
Appearing in the Early Cambrian and exhibiting the pentameral
symmetry characteristic of echinoderms (the group which includes
starfish and sea-urchins), the eocrinoids (“Dawn Crinoids”) of the
shallow Cambrian seas were bottom-dwelling, bud-shaped
creatures on elongated, tapering stems. Lacking the specialized
respiratory structures of their more advanced descendants, these
primitive marine animals fed by transporting tiny, filtered food
particles along their simple brachioles (arms) to their mouths,
which were located on top of the bud, or theca. Although quite rare,
they persisted for over 200 million years, disappearing after the
Silurian.
The origin of the first chordates (ancestors of the vertebrates)
appears to have occurred within the early echinoderm group, some
of whose free-swimming larvae closely resemble the simplest
living invertebrate chordates, the acorn worms which live along the
geothermal vents at the bottom of the sea. Private collection.
THE BURGESS FAUNA
16. Kingdom Monera,
Phylum Cyanophta
Cryptozoon proliferum
Late Cambrian, New York
Providing a variety of habitats for the sudden explosion of
invertebrate life throughout the planet at the dawn of the Cambrian,
the stromatolite reefs all but vanished about 570 million years ago,
presumably as a result of widespread grazing on the algae that
formed them. Although fossilized algae is distributed throughout
the world, exceedingly rare, living stromatolites are found only in
such isolated places as the Bahamas and Australia where the
currents are too swift or the waters too hypersaline to permit
grazing. Exposed by glacial activity, this spectacular form of
Cryptozoon (“Secret Life”) grew along the barrier reefs of an
ancient island now known as the Adirondack Mountains. Monroe
Community College.
Discovered by Charles Doolittle Walcott in 1909, the Middle
Cambrian deposits of the Burgess Shale of British Columbia
represent the period of abundant genetic diffusion which followed
the initial explosion of rapidly diversifying animal forms at the
dawn of the Cambrian. These extraordinary “shadow fossils”,
known as the Burgess fauna, are the filmy remains of creatures that
were buried alive about 530 million years ago by a series of
mudslides at the base of a massive algal reef, leaving an
unparalleled record of the soft-bodied animal life indigenous to a
primordial sea that stretched from the Arctic Ocean to the Pacific
of Southern California. Miraculously preserved to the finest detail
as reflective imprints of carbonized film on black shale, these
primitive marine organisms are startling evidence of the presence
of all existing animal phyla in the Middle Cambrian seas,
alongside a number of extinct forms that defy classification in any
known groups. From the Middle Cambrian Burgess Shale of
British Columbia. U.S. National Museum.
17. Phylum Arthropoda,
Class Trilobita
Olenoides serratus
Middle Cambrian, British Columbia
Preserved in exceedingly rare condition, with its soft-tissued
antennae and limbs intact, including gills and chewing bases, this
small but widespread denizen of the ancient reef habitats is one of
the oldest and best-known of the early spined trilobites. Belonging
to the corynexochid order, Olenoides was characterized by eyes of
medium size with a pygidium (tail) of smaller size than its
cephalon (head). Although its soft parts were protected by a sturdy
exoskeleton (which it periodically shed as it grew), it was a passive
and defenseless scavenger that lived by filtering tiny particles of
food from the muddy sea floor.
Phylum Arthropoda,
Order Limulavida
Sidneyia inexpectans
Middle Cambrian, British Columbia
Swimming by means of a tail fan resembling those of crustaceans,
this predatory arthropod exhibits the combined characteristics of
distinct family groups which have subsequently diverged
(chelicerates and crustaceans). It fed by passing food from its rear
limbs to its mouth, as do most marine arthropods, whose legs are
outfitted with spiny teeth. The digested remains of tiny trilobites
have been found in the guts of some specimens
18. Kingdom Animalia,
Phylum Chordata
Pikaia gracilens
Middle Cambrian, British Columbia
The unlikely preservation of this tiny marine organism supplies
one of the most important clues to the enigmatic origin of the
vertebrates. Despite its long standing classification as an annelid
worm, its profound reinterpretation in 1979 by Simon Conway
Morris and Harry Whittington revealed the distinguishing bands of
muscles and dorsal notochord extending the length of its body
which identify this swimming filtrator-feeder of the shallow seas
as the oldest known chordate, a direct ancestor of the vertebrates.
Outnumbered by vast varieties of arthropods and coelenterates, the
first proto-fishes appear to have been represented exclusively by
this single species in the Cambrian seas of western Canada where
this rare and important creature (along with its myriad descendants)
once faced a very tenuous future in terms of survival.
Kingdom Animalia,
Phylum Arthropoda
Waptia fieldensis
Middle Cambrian, British Columbia
Although superficially shrimplike, this primordial marine creature
is ranked among the unplaceable early arthropods of unique
anatomical form. Among the most common of the Burgess
arthropods and dwelling almost exclusively on the shallow sea
floor where it extracted small particles of food from the muddy
sediment, it was probably a weak swimmer and did not actively
pursue prey.
TRILOBITES
The most commonly preserved creatures of the ancient Cambrian
seas were the ubiquitous trilobites (“Three Lobes”). Comprising
more than half of all known animal life at the time, they shared the
warmer waters with early jellyfish and sponges. Throughout the
Silurian and Devonian periods, as predatory eurypterid, early
jawed fish, and amphibians appeared and proliferated, the numbers
of trilobites dwindled, disappearing entirely at the close of the
Paleozoic Era some 245 million years ago.
19. Order Redlichiida,
Family Olenellidae
Bristolia bristolensis
Early Cambrian, California
An early member of the olenellid family, representative of the
redlichiid order, with large, crescent-shaped eyes. Among the
oldest and most primitive of trilobites, a spined, bottom-dwelling
scavenger capable of both swimming and crawling.
These vastly diversified primordial invertebrates, exhibited in
chronological progression, comprise 8 distinct orders (including
the Agnostida) and represent every period of the Paleozoic Era
from their sudden appearance in the Early Cambrian to their
extinction in the Permian. From private collections.
20. Class Trilobita,
Order Corynexochida
Olenoides superbus
Middle Cambrian, Utah
A common representative of the widespread corynexochid order,
characterized by its medium-sized eyes and enlarged pygidium
(tail).
21. Order Corynexochida,
Family Ogygopsidae
Hemirhodon amphipyge
Middle Cambrian, Utah
A member of the ogygopsid family, a variant form of
corynexochid, characterized by medium-sized eyes and a broad,
fused pygidium, well-developed for burrowing.
22. Class Trilobita,
Order Corynexochida
Wanneria walcottana
Late Cambrian, Pennsylvania
A late representative of the dwindling corynexochids which died
out by the close of the Cambrian, characterized by its mediumsized eyes and spiny pleura (ribs). A scavenger adapted for
crawling on the muddy sea floor.
23. Class Trilobita,
Order Odontopleurida
Eoceraurus trapezoidalis
Ordovician, Oklahoma
24. Class Trilobita,
Family Raphiophoridae
Lonchodomas mcgeheei
Ordovician, Oklahoma
The spines of these peculiar trilobites were special adaptations for
the widest possible distribution of body weight on the soft sea floor,
where its life was spent crawling in the mud. From the Ordovician
of Oklahoma. Excellently preserved along with the partial remains
of a juvenile of the same species, this rare, early phacopid
belonged to a diverse new order distinguished by its highly
complex eyes.
This unusual and highly specialized member of the raphiophorid
family was a sightless, lightly built swimmer, protected from
predators by its long spines which also may have aided in surface
flotation and drifting with the current.
25. Class Trilobita,
Order ptychopariida
Amphyxina bellatula
Ordovician, Missouri
Tiny, gregarious examples of the ptychopariids, an extremely
diverse order which gave rise to most of the trilobites that appeared
after the Cambrian, descended from the older, extinct redlichiids,
which their earliest representatives resembled.
27. Order Phacopida,
Family Dalmanitidae
Kanoshia kanoshensis
Late Ordovician, Utah
A typical example of trilobite behavior, this early form of phacopid,
ancestral to the later dalmanitid family and distinguished by its
distinctively flared pygidium, commonly protected itself from
danger by rolling up when threatened.
26. Order ptychopariida,
Family Trinucleidae
Cryptolithus laelus
Ordovician, Pennsylvania
An elegant, pyritized example of the vast order of ptychopariids,
this tiny, sightless member of the widespread trinucleid family
possessed a broad, perforated brim along the cephalon (head) and
elongated genal spines, which supported its body on the soft,
muddy sea floor on which it lived.
28. Class Trilobita, Order Proetida
Fragiscutum glebalis
Silurian, Oklahoma
A tiny and uniquely specialized member of the longstanding
proetid order, capable of enrolling and distinguished by its unusual
eyes positioned at the ends of short stalks.
30. Order Phacopida,
Family Calymenidae
Diacalymene clavicula
Silurian, Oklahoma
A member of the abundant calymenid family, a variant form of
phacopid with smaller, simpler eyes than its more specialized
relatives, and typically found enrolled.
29. Class Trilobita, Order Lichida
Arctinurus boltoni
Silurian, New York
A large and splendid example of the diverse order of lichids, a
broad, flattened form well-suited to a life spent crawling on the sea
floor, filtering organic food particles from the mud.
32. Class Trilobita, Order Lichida
Dicranurus hamatus
Early Devonian, Oklahoma
This rare, exotic form of lichid was equipped with a pair of horns
and elongate, prickly spines extending from every part of its body,
an effective defense against the growing number of marine
predators.
31. Order Phacopida,
Family Dalmanitidae
Huntonia oklahomae
Early Devonian, California
An unusually specialized phacopid, this long-snouted member of
the widespread dalmanitid family was well-adapted for plowing in
the sand and burrowing, lying with only its head exposed,
watching with its compound eyes and waiting for tiny prey to
crawl or drift by.
33. Class Trilobita,
Order Odontopleurida
Leonaspis williamsii
Early Devonian, Oklahoma
With tiny eyes positioned on the tips of short, stiff stalks, this small,
bizarrely barbed trilobite was among the last representatives of the
rather spiny order of odontopleurids, which had persisted from the
Late Cambrian.
35. Class Trilobita, Order Proetida
Ditomopyge parvulus
Pennsylvanian, Oklahoma
This cluster of tiny, pyritized proetids may represent moltings
rather than the actual remains of the animals themselves, which
periodically shed their exoskeletons as they grew.
34. Order Proetida,
Family Phillipsidae
Breviphillipsia sampsonii
Mississippian, Missouri
A member of the diverse phillipsid family, representative of the
far-ranging proetid order which flourished from the Ordovician to
the end of the Paleozoic.
36. Class Trilobita, Order Proetida
Delaria antiqua
Permian, Texas
Descended from the primitive ptychopariids of the Early Cambrian
and characterized by its large eyes and pygidium and the ability to
enroll, this late proetid was among the very last of the trilobites.
37. Class Trilobita,
Order Ptychopariida
Isotelus maximus
Late Ordovician, Ohio
198. Class Trilobita,
Order Redlichiida
Acadoparadoxides
Early Cambrian, New York
The paradoxid trilobites were the first animal group on earth to
produce a variety so dramatically larger than its relatives that it
qualifies as a giant. Preserved together, these magnificent
specimens are over half a billion years old. Private collection.
Among the largest of the early giant forms of trilobites was the
well-documented Isotelus which ranged up to 30 inches in length.
As a group the Ptychopariids were probably ancestral to most of
the trilobite groups that appeared after the Cambrian. Capable of
crawling along the sea floor, this perfectly preserved individual
was also equipped with a broad pygidium (tail section) for plowing
burrows in the mud. Although animal coloration does not fossilize,
patterns indicating the former presence of color are sometimes
preserved. Exceedingly rare clues to the coloring of trilobites are
evidenced by the preservation of stripes on some Isotelus maximus
specimens. Private collection.
39. Class Trilobita, Order Phacopida
Dalmanites
Early Silurian, Tennessee
Though some trilobites were sightless, most were equipped with
either single-lens or compound eyes. With an almost hemispherical
field of vision to aid them in their hunt for food on the muddy
ocean bottoms, trilobites were the first creatures on Earth to
develop complex eyes, some of which were composed of over
10,000 individual lenses.
38. Phylum Arthropoda,
Class Trilobita
Homotelus bromidensis
Ordovician, Oklahoma
Presumably evolved from segmented Precambrian annelid worms,
these primitive arthropods, distinguished by their simple eyes and
enlarged cephalons and pygidia, were simple scavengers, dwelling
on the muddy sea bottoms and grubbing for food, periodically
shedding their sturdy exoskeletons as their softer internal parts
outgrew them. A gentle and gregarious creature, Homotelus
(“Same End”) derives its name from the similarity between its
anterior and posterior sections. This spectacular cluster of 30
ptychopariid trilobites perished together 500 million years ago in
the ancient sea of Oklahoma, preserved in a mass burial along with
cast-off moltings, in beautiful mosaic detail. Private collection.
Although compound eyes were not uncommon among the
diminished groups of trilobites that survived the Ordovician
extinction, this progressive order of early phacopids had eyes
equipped with an advanced type of lens structure that enabled them
to see better in the deeper, darker waters and at night. Inhabiting
the offshore marine environments of the Silurian, this rare and
giant form of Dalmanites may have been nocturnal. Burrowing
with its diminutive telson (tail spike) into the soft sand until only
their heads were exposed, they would lie in wait for tiny drifting
prey. Private collection.
40. Phylum Arthropoda,
Class Eurypterida
Eurypterus remipes
Eurypterus lacustris
Pterygotus macrophthalmus
Late Silurian, New York
Widespread throughout the Paleozoic Era, these giant water
scorpions were particularly abundant during the Silurian Period
(465 to 415 million years ago) when they ranged marine
environments to brackish streams and
marine environments to brackish streams and estuaries. The sharp
telson, or tailspike of Eurypterus (“Wing Fin”), primarily useful
for correcting its position when stranded upside down on the seafloor, may have been armed with a venomous stinger. Two
individuals of one species and a smaller individual of another
species are dramatically preserved together with yet another
species of eurypterid prominent at the bottom of the slab. Armed
with pincers and a spiked fantail Pterygotus was a ferocious
predator. Numerous fossilized trilobites bear scars left by the
fearsome pincers of such creatures.
Descended from trilobites (whose enormous populations they
helped to decrease), these impressive invertebrates possessed an
elongated, segmented body and were equipped with a pair of
compound eyes as well as a pair of simple ones. Sometimes
growing to lengths of as much as 10 feet, these early arthropods
were the direct antecedents of the first creatures to leave the
aquatic environment to inhabit dry land: the scorpions. Private
collection.
47. Phylum Arthropoda,
Class Eurypterida
Mixopterus kiaeri
Silurian, Norway
Prowling the ancient seas and brackish estuaries of Norway, this
massive predatory arthropod, over 3 feet in length, preyed on fish
and trilobites grasped in its spiny appendages or pierced with the
spike at the tip of its tail. Other appendages, modified from its
mouth parts, served for swimming, crawling, and mating.
The discovery of fossil trails left in the mud near Oslo
suggest an amphibious lifestyle allowing for these ferocious
creatures to crawl out of the water onto dry land on their 2 sets of
legs for brief periods of time, its menacing tail curled over its back
while hunting. The most scorpion-like of all the diverse groups of
eurypterids, this fearsome variety appears to be their direct
ancestor. Discovered in 1909, they were widely spread throughout
northern Europe and North America. From the University of Oslo
Geological Museum.
of disabling their prey. Unlike the tiny, primitive Silurian
scorpions, the amphibious Devonian forms were adapted to
feeding out of water. External digestion, or liquid feeding, is not
possible in an aquatic environment, where ingestion of solid food
is necessary. The Devonian scorpions exhibit a definite landward
trend along the deltas and intertidal estuaries of central Europe
with the sole exception of Palaeoscorpius, a formidably large
example known exclusively from deep marine deposits. From the
University of Bonn.
41. Phylum Arthropoda,
Class Arachnida
Palaeoscorpius devonicus
Late Devonian, Germany
Among the very first creatures to abandon the aquatic environment
and invade the land, an event which took place during the Late
Silurian, were the scorpions. Derived from eurypterid, the earliest
true scorpions were marine creatures. Pressured by the rise of
predatory fishes and eurypterid, the appearance of amphibious
scorpions, capable of surviving In a terrestrial environment for
limited visits, presumably led to the establishment of completely
terrestrial, air breathing varieties.
Related to spiders, these ferocious predatory arachnids possess a
venomous stinger on the tip of the tail, with which they are capable
42. Superclass Agnatha,
Order Osteostraci
Cephalaspis lyelli
Early Devonian, Scotland
Ancestral to the first true fishes, the Agnatha (“Jawless Ones”) are
the oldest fossil vertebrates. Of this early group of marine and
freshwater creatures, Cephalaspis (“Shield Head”) was the most
successful and enduring. Ranging throughout the Late Silurian
rivers, lakes, and estuaries from Asia to Germany, it had spread as
far as eastern Canada by the end of the Devonian.
With its head encased in a bony, armored carapace (or shell),
Cephalaspis was vulnerable to very few predators other than
eurypterid. Presumably a bottom-dweller, it fed by filtering
particles of food from mud sucked into its small, jawless mouth.
Between its 2 upward-looking eyes lay the pineal body, or “third
eye,” a photosensitive organ which distinguished light from shade.
Networks of nerves, preserved in a number of fossil specimens,
extended from its simple brain to sensory dorsal plates. Once
considered to be electrical organs, these sensitive plates probably
served to monitor such things as temperature and water pressure as
well as vibrations. They became extinct some 365 million years
ago. From the Royal Scottish Museum.
43. Phylum Echinodermata,
Class Crinoidea
Acanthocrinus rex
Early Devonian, Germany
Although having the appearance of plants, crinoids (“Lily-Form”)
are actually primitive sea creatures related to starfish and sea
urchins. Belonging to the echinoderm group, they first appeared
during the Ordovician, feeding on tiny plants and animals filtered
from the gentle currents that washed along their feather-like
pinnules to their mouths. Attached by their delicate stems to
objects on the sea floor, these echinoderms spent most of their
lives anchored in one place, although they were capable of
relocating when necessary, either by drifting or by crawling slowly
along the sea floor. From the Humboldt Museum.
45. Superclass Gnathostomata,
Class Acanthodii
Cheiracanthus
Middle Devonian, Scotland
44. Superclass Agnatha
Class Pteraspidomorphi
Drepanaspis gemuendensis
Early Devonian, Germany
Specially adapted to a bottom-dwelling existence, this flattened,
jawless fish possessed a primitive, bony shield over its head and
the front of its body. First appearing in the freshwater rivers of
Europe and North America, the pteraspids gradually spread to the
oceans. Feeding on tiny organisms scooped out of the muddy river
bottoms with a series of small plates along its jawless mouth,
Drepanaspis lacked fins but was equipped with a “third eye.”
From the Humboldt Museum.
The earliest known jawed fishes, the acanthodians, with their
characteristically large eyes and streamlined bodies, ranged from
the Late Silurian to the Early Permian, inhabiting freshwater
lakes and streams throughout the world. Degeneration of gill
arches in these primitive fishes produced the first hinged jaws,
endowing them with a distinct advantage in hunting. Commonly
known as “spiny sharks”, each of their fins bore a prominent spine
along its edge. Unrelated to sharks, they are the progenitors of the
bony fishes, including both lobe-fins and ray fins. Private
collection.
46. Phylum Mollusca
Class Cephalopoda
Agoniatites vanuxemi
Middle Devonian, New York
Named for the ram’s horns of the Egyptian god Ammon, the
ammonoids (a subclass of the cephalopod group) were tentacled
marine creatures related to the squid. Possessing a chambered,
spirally coiled shell which both housed the creature and provided
buoyancy, as well as an ink sac for blinding its enemies during
escape, Agoniatites resembled the modern Nautilus. The
ammonoids appeared in the Devonian and survived until the end of
the Cretaceous, though the goniatites (which typified the early
forms) were extinct by the end of the Permian. Capable of
swimming very rapidly, this marine invertebrate propelled itself by
ejecting water. The fossilized shells of these large early mollusks
are commonly found worldwide. Private collection.
48. Class Trilobita, Order Phacopida
Phacops africanus
Devonian, Morocco
Although trilobites began to decline after the close of the Cambrian,
probably as a result of increased predation from the rapidly
growing numbers of fishes and other marine life, they enjoyed a
temporary resurgence of diversity in the Devonian, giving rise to
the largest and most grotesque forms known. In dwindling
numbers, these once common creatures survived into the Permian
before vanishing from the fossil record. This giant phacopid
trilobite, with its excellently preserved compound eyes, each
composed of over 100 individual lenses, is characterized by its
large eyes, a granularly decorated glabella (face), and the ability to
enroll. Private collection.
49. Class Placodermi,
Order Antiarchi
Bothriolepis canadensis
Late Devonian, Canada
Derived from the earlier Agnatha, the Devonian placoderms were
among the first ancestral fishes to develop jawbones and paired
fins. Growing to about 1 foot in length, these primitive vertebrates
were equipped with a bony armored carapace which covered the
front part of the body, the exposed trunk and tail presumably
covered with scales. Also found in Antarctica, the widespread
Bothriolepis (“Trench Scale”) reached North America near the end
of the Devonian, inhabiting freshwater lakes and streams.
The development of jaws in these fishes, though rudimentary,
increased their capacity for hunting and feeding. Their paired and
spiny pectoral appendages may have served as anchors against
currents as they gleaned for food on the muddy river bottoms. The
2 pockets stemming from the throat may have served as lungs,
temporarily allowing Bothriolepis to breathe air when stranded on
shoals by the tide. This exquisitely preserved school of placoderms
represents some of the earliest of true fishes. American Museum
of Natural History.
50. Class Placodermi,
Order Arthrodira
Dunkleosteus terrelli
Devonian, Ohio
The earliest known giant vertebrate, Dunkleosteus (“Dunkle’s
Bones”) grew to lengths of over 16 feet and weighed up to 5 tons.
Like all placoderms, its massive head was protected by an armor of
bony plates while its scaly trunk was exposed. Possessing no teeth,
its powerful jaws were equipped with razor-sharp blades of
bone which enabled it to slash and crush the armor of its prey. Also
known as Dinichthyes, this monstrous fish hunted everything from
sharks and other placoderms to large invertebrates throughout the
Devonian oceans of North America and Europe. Their extinction
coincides with evidence of widespread tidal waves which appear to
have devastated the majority of marine life along the seashores at
the end of the Devonian period about 365 million years ago.
Cleveland Museum of Natural History.
51. Order Crossopterygii,
Suborder Rhipidistia
Eusthenopteron foordi
Late Devonian, Canada
As the Late Devonian freshwater streams and ponds shrank or
dried up during periods of drought, the primordial, lobe-finned
lungfishes of the period developed rudimentary adaptations to the
hostile environment of land before spreading into the seas. Special
bone features that enabled them to crawl on their fins evolved not
for the purpose of escaping the aquatic environment, but as a
means of reaching fresher water when shrinking pools became
crowded and putrid or the streams became too muddy.
A formidable predator resembling the modern pike and perfectly
preserved with its fins and scales intact, this elongated freshwater
fish was highly adapted to the severe climatic fluctuations (often
daily) of the Devonian. With tear ducts to keep its eyes moist and
lungs derived from a simple air bladder originally employed to
keep the bodies of fishes right side up, Eusthenopteron (“Good
Strong Fin”) was able to breathe out of water during times of
drought and stagnation while other fish suffered asphyxiation.
Some of the descendants of this ruggedly adaptive crossopterygian
fish gave rise to tetrapod amphibians, the others, to saltwater
coelacanths. The apparent progenitor of all terrestrial vertebrates, it
was extinct by the dawn of the Permian. Royal Ontario Museum.
52. Class Amphibia,
Subclass Labyrinthodontia
Ichthyostega
Late Devonian, Greenland
The origin of terrestrial vertebrate life appears to have begun in
Greenland with the appearance of the first tetrapod amphibians.
Among the earliest of these creatures, Ichthyostega (“Fish Plate”)
inhabited freshwater lakes and streams during the Late Devonian
and Early Carboniferous. Derived from crossopterygian fishes, this
air-breathing predator still retained many of the primitive fishlike
structures of its ancestors. Although it possessed scales and a long
tail fin, it also had a sturdy backbone and 4 short limbs, each
equipped with 7 digits, enabling it to waddle about on dry land for
limited periods of time before having to return to water.
Unlike the amphibians that were to follow, Ichthyostega lacked
notches for ears, an indication that it had no auditory sense. Its
direct relation to crossopterygian fishes is evidenced by their
virtually Identical tooth patterns, a distinctive characteristic which
Ichthyostega passed on to the varied generations of labyrinthodont
amphibians which it produced. In fact, this important creature is
believed to have given rise to all of the diverse and prolific groups
of reptiles, birds, and mammals which followed. Although welldocumented in the fossil record, Ichthyostega is known only from
incomplete remains. Skull reconstruction courtesy of the Swedish
Museum of Natural History.
THE LATE PALEOZOIC ERA
from 345 to 250 million
years ago
Inundated by the inland invasion of the seas throughout the
Mississippian (345 million years ago), the first division of the
Carboniferous period, immense tropical forest regions were fossilized
into deep carbon bands in the Earth’s crust. During the Pennsylvanian
(310 million years ago), the remaining division of the period, reptiles
diverged from their amphibious ancestors and began to proliferate on
the land.
By the Permian (280 million years ago), named for the discovery
of fossils near the region of Perm in western Siberia, mammal-like
reptiles (synapsids) had appeared, characterized by developments that
would ultimately distinguish them from their reptile ancestors and lead
to a new class of animals.
All of the continental land masses of the Cambrian collided during the
Permian, forming the supercontinent of Pangaea. A series of
devastating ice ages were triggered by the encroachment of the
supercontinent on both poles. The resulting widespread extinction that
ended the Permian period and the Paleozoic Era was of such massive
proportions that it has never been equaled, over 90 percent of all
species vanishing. The decimation of the once dominant multitudes of
mammal-like reptiles provided an ecological niche that favored the
surviving reptile groups.
53. Paleozoic Sea Floor
Crinoids
Brachiopods
Coral
Trilobite
Mississippian, Indiana
Dominated by a fossilized crinoid and flecked with tiny
brachiopod shells, coral, and even a half-buried trilobite, this
exquisite slab has preserved a cross-section of a once thriving
marine ecosystem.
Trace fossils preserving the activities of trilobites are not
uncommon. Digging furrows into the sand with their jointed limbs
(or endopodites), many left tiny trails that dried and hardened
before they could be washed away. Fossilized burrows indicate
that trilobites apparently laid their eggs in pits carefully dug ill the
sea floor, afterwards leaving them to be covered by drifting sand to
protect them from predators. Private collection.
The Early Paleozoic crinoid gardens were sparse compared to the vast
varieties of the Mississippian period, known as the Age of Crinoids.
Most of the crinoids died out at the close of the Paleozoic, however a
few species still survive today. Preserved in beautiful detail, these 6
crinoid species were rendered in bouquet. Private collection.
55. Phylum Cnidaria,
Class Scyphozoa
Essexella asherae
Pennsylvanian, Illinois
Swimming by rhythmic contractions of their gelatinous bodies, these
medusoid jellyfish preyed on small creatures that became entangled in
their poisonous, dangling tentacles. Lacking a central nervous system,
these simple marine organisms are actually colonial animals composed
of hundreds of specialized individual creatures, each fulfilling a
separate function such as flotation, stinging, feeding, or digestion.
From the famous Mazon Creek deposits. Private collection.
54. Phylum Echinodermata,
Class Crinoidea
Ulrichicrinus coryphaeus
Actinocrinites gibsoni
Dorycrinus gouldi
Taxodrinus colletti
Sarocrinus nitidus
Agaricocrinites americanus
Late Mississippian, Indiana
early plants did not decay but instead turned to peat which in time
became coal. Private collection.
56. Kingdom Plantae,
Class Lyginopteriodopsida
Neuropteris rodgersi
Pennsylvanian, Pennsylvania
Presumably evolved from Precambrian one-celled algae, primitive
plants existed long before the appearance of the first animals.
Neuropteris, an ancient seed fern of the coal forests of 300 million
years ago (derived from early terrestrial plants of the primordial
Silurian Period) was able to circulate water and nutrients to the
cells of its highest leaves by means of its advanced root and
vascular systems. Unlike the more primitive true ferns which
reproduce from spores, these large, non-flowering, tree-like plants
were crowned with seed-bearing fronds.
Supported by rigid trunks that often reached heights of as much as
10 feet, this common seed fern proliferated in the dense swamps
and forests of the Late Paleozoic during a time when coastal areas
were often inundated by the intermittent rising of the seas. Deeply
buried under accumulated organic debris, the remains of these
57. Phylum Tracheophyta,
Class Sphenopsida
Annularia stellata
Pennsylvanian, Kansas
Appearing in the Devonian, the horsetails (or scouring rushes) were
typical in the primordial swamps. Apparently derived from early ferns,
ancient forms known as calamites once grew as large as trees, forming
vast jungles along the rivers and lakes of the Coal Age. Characterized
by the whorls of leaves growing from the joints of their branches,
these plants have survived to the present, occurring in both humid and
arid environments. This beautifully preserved Annularia impression is
among the most common of the Pennsylvanian calamites. Private
collection.
58. Phylum Tracheophyta,
Family Calamitaceae
Calamites
Pennsylvanian, Michigan
Armed with tissue laced with an abrasive silica grit to discourage
grazing, and growing to heights of as much as 40 feet, this tree was
widespread throughout the marshy jungles of Europe, Asia, and
North America during the Pennsylvanian and Early Permian. First
described as fossilized pith unassociated with any foliage,
Calamites are now recognized as the fossilized trunks of giant
rushes whose leaves were separately described as Annularia. From
Brigham Young University.
59. Phylum Tracheophyta,
Class Lycopsida
Lepidodendron aculeatum
Pennsylvanian, Utah
Appearing in the Early Devonian, this lycopod was among the tallest
and most abundant of trees in the humid Carboniferous swamps of
Europe and the Americas. Lepidodendrons (“Scale Tree”) ordinarily
grew to heights of 100 to 150 feet. First described on the basis of
fossilized bark bearing the scale-shaped scars of fallen leaves, the
roots and foliage of these primordial trees were described as separate
genera. Brigham Young University.
61. Class Lycopsida,
Order Lepidodendroles
Lepidophyllum
Pennsylvanian, Utah
This genus was established to describe the fossilized foliage of
Lepidodendrons not found in association with the rest of the plant.
Starting at a height of 115 feet and extending upwards for another
20 feet, Lepidodendron had dagger-like leaves which grew close to
the thick bark, leaving ranks of diamond-shaped scars when they
fell off the tree. Reproducing by means of spore-bearing cones
which grew on the tips of their branches, these early plants gave
rise to some 110 known species before becoming extinct during the
Permian, survived only by the club mosses. From Brigham Young
University.
60. Class Lycopsida, Order Lepidodendroles
Stigmaria
Pennsylvanian, Michigan
Prior to their recognition as the root systems of Lepidodendrons, these
isolated fossils were separately described as Stigmaria. Growing
horizontally and extending as much as 40 feet around the base of the
plant, these underground stems, or rhizomes, bear pitted scars marking
the points at which the roots emerged. From Brigham Young
University.
predominantly on the land. Giving rise to the massively-skulled
Eryops of the Permian and the flattened stereospondyls of the
Triassic, these tiny predators of the coal swamps were not on the
evolutionary path to reptiles, birds, and mammals. Private
collection.
65. Class Reptilia,
Order Cotylosauria
Cephalerpeton ventriarmatum
Pennsylvanian, Illinois
63. Subclass Labyrinthodontia,
Family Dissorophidae
Eoscophus lockardi
Pennsylvanian, Kansas
Among the earliest of terrestrial amphibians, this skeleton of a
primitive labyrinthodont was well-adapted to life outside the
aquatic environment and bore no trace of the archaic tail fin of its
Devonian ancestors once it reached adulthood. Laying their eggs in
water, they hatched into gilled larval forms which remained in the
water until reaching maturity, when they began a life of dwelling
One of the very oldest vertebrates to be recognized as a reptile,
Cephalerpeton belonged to the most primitive group, the anapsids,
which began with the suborder Captorhinomorpha. Descended
from labyrinthodont amphibians, the early “stem reptiles”, or
cotylosaurs, were the ancestral stock of all Reptilia, distinguished
by their revolutionary ability to deposit their eggs on dry land,
bypassing the gilled larval stage of their immediate ancestors. As
the first vertebrates to become entirely independent of water, their
ability to exploit the terrestrial habitat led to a rapid radiation of
diversely specialized reptile groups which included the ancestors
of birds and mammals. From the Mazon Creek deposits. Yale
Peabody Museum.
and the closest link to their amphibian ancestry. Because related
forms document the passage of a gilled larval stage, a
characteristic thoroughly eliminating them from the reptilian class,
Seymouria is now placed among the anthracosaurs (“Coal
Reptiles”) by most authorities, thus including this distinctly
terrestrial amphibian in the group of Permian labyrinthodont.
Although Seymouria (named for the town of Seymour, Texas
where it was discovered) differed very little from the
Pennsylvanian ancestors of the reptiles, it left no known
descendants. This exquisite skeleton is from the U.S. National
Museum.
66. Class Reptilia,
Order Cotylosauria
Eocaptorhinus laticeps
Early Permian, Oklahoma
Among the earliest and most primitive reptiles, these ancient,
superficially lizard-like creatures possessed no temporal openings in
their skulls. Their simple eardrums were located much closer to the
jaw articulation than the archaic notches of their amphibian forebears.
Oklahoma Museum of Natural History.
67. Subclass Labyrinthodontia,
Order Anthracosauria
Seymouria baylorensis
Early Permian, Texas
With a sturdy, terrestrial-type skeleton characteristic of reptiles and
a skull exhibiting prominent ear notches characteristic of
amphibians, Seymouria was long regarded as a primitive reptile
68. Class Amphibia,
Subclass Labyrinthodontia
Eryops megacephalus
Early Permian, Texas
Throughout the Carboniferous and Early Permian periods, the
evolving groups of primitive amphibians, collectively known as
labyrinthodont (due to the labyrinthine wrinkles in their tooth enamel,
derived from their crossopterygian antecedents) are exemplified by
Eryops (“Drawn Out Face”) which inhabited the lush deltas along
the edge of the ancient sea of Texas, Oklahoma, and New Mexico
260 million years ago. Eryops was largely an aquatic creature like
the modern alligator. Unlike the early fish, these amphibians were
able to listen for their prey due to their well-developed eardrums,
evolved from degenerate skull bones inherited from their fish
ancestors.
A true amphibian, Eryops laid its eggs in water, its young passing
through a larval stage, with gills for breathing, before reaching
maturity. Armed against predators with bony nodules in its skin and
growing to about 6 feet in length, this extremely common swamp
creature presumably preyed on fish and other amphibians. Hunted, in
turn, by the fierce Dimetrodon, Eryops was extinct by the close of
the Permian, although its survivors gave rise to the peculiar
stereospondyl amphibians of the Triassic. Collected by Kenneth W.
Craddock. Private collection.
69. Class Amphibia,
Subclass Lepospondyli
Diplocaulus magnicornis
Early Permian, Texas
Among the most bizarre of the Permian lepospondyl amphibians is
Diplocaulus (“Two- Tail”), a flattened, bottom-dwelling predator of
the Late Pennsylvanian to Early Permian streams and ponds.
Ranging from 1 to 3 feet in length and lying in wait on the murky
bottom, Diplocaulus fed by ambushing prey, its upward-looking
eyes positioned on top of its grotesquely boomerang-shaped head.
With tiny legs for its overall length and a body too flattened to bear
the musculature necessary for swift locomotion, Diplocaulus was
probably not a very strong swimmer despite speculations regarding
the hydrodynamic properties of its oversized head. Unable to see
each other except by touch due to the placement of their eyes, the
widely extended corners of these creatures’ skulls may have
provided advantages in intimidating displays of head-butting during
mating competition, gradually producing a genetic favoring of those
with the greatest range. Private collection.
70. Subclass Synapsida,
Order Pelycosauria
Dimetrodon limbatus
Early Permian, Texas
The aggressive, carnivorous Dimetrodon (“Dual Sized Tooth”),
distinguished by a prominent dorsal fin along its back, prowled the
upland regions of the swampy deltas of northern Texas along the
edge of a shallow, drifting sea. The dominant predator of this area,
Dimetrodon fed without competition on an abundant population of
large, defenseless amphibians. Belonging to the archaic order of
finback pelycosaurs, these early cold-blooded synapsids were
ancestral to the mammal-like reptiles of later Permian times.
Equipped with a ferocious arcade of palatine teeth (in addition to the
sharp teeth that lined their jaws). Incapable of sustaining an extended
chase, they probably hid in the lush vegetation, waiting for
unsuspecting prey to stray too close to escape a quick, surprise attack.
The creature’s impressive dorsal “sail” provided a large surface area
for warming the blood when exposed to sunlight and cooling it when
in the shade, although such spectacular features may evolve more
rapidly for the purpose of mating displays than for thermal functions.
By the Middle Permian, when the climate along the delta became too
dry to sustain them anymore, the Dimetrodons disappeared quite
suddenly from the fossil record. Brigham Young University.
Permian pelycosaurs and the later Permian freshwater mesosaurs,
the possible forerunners of the air-breathing, marine ichthyosaurs.
Collected by Charles Camp and Samuel Welles in 1928 and
identified by Wann Langston and Robert Reisz in 1981, this cluster
of Early Permian specimens also contains the dissociated bones of
various other reptiles and amphibians including an Eryops and an
Edaphosaurus. University of California at Berkeley.
71. Class Reptilia,
Subclass Synapsida
Aerosaurus wellesi
Early Permian, New Mexico
The most primitive of the early synapsid reptile groups, the
pelycosaurs may have led a somewhat amphibious existence, similar
to that of alligators. Catching and killing its prey in jaws lined with
an extraordinary number of sharp teeth, Aerosaurus (“Air Lizard”)
was apparently an aggressive predator. Equipped with an unusually
long and flat swimming tail, this young pelycosaur probably preyed
on fish as well as on smaller, slower reptiles and amphibians.
Although undoubtedly cold-blooded, because of their specialized
bone structure the archaic synapsid reptiles are considered to be the
ancestors of the therapsids, the later and more advanced reptile
group that subsequently gave rise to warm-blooded mammals.
Some scientists have also noted affinities between the Early
72. Class Reptilia,
Subclass Anapsida
Mesosaurus brasiliensis
Early Permian, Brazil
A small freshwater reptile of the lakes and estuaries of Permian
South Africa and South America (when the 2 continents were still
joined), the slender Mesosaurus (“Middle Reptile”) grew to a length
of 3 feet and had jaws lined with needle-shaped teeth for catching
fish. The earliest known aquatically adapted animal descended from
terrestrial ancestors, its broad limbs were adapted for swimming and
appear to have been web-footed. University of California, Los
Angeles.
73. Class Reptilia, Subclass Anapsida
Mesosaurus africanus
Early Permian, South Africa
Although mesosaurs are believed by some to be a transitional stage
between the later ichthyosaurs and their early land-dwelling
ancestors, due to their extremely primitive aquatic adaptation, there
are no actual affinities between the two animal groups to support this
supposition. Because the remains of this creature have been found
only in Brazil and South Africa, Mesosaurus is one of the very
strong links in the chain of evidence for shifting continents. From the
famous Karroo Formation. Private collection.
74. Class Reptilia,
Subclass Therapsida
Dicynodon grimbeeki
Middle to Late Permian, South Africa
For about 10 to 15 million years, great herds of these fat, little
mammal-like therapsids inhabited South Africa, Russia, Scotland,
Asia and the Americas, apparently reproducing at an extraordinarily
prolific rate. Found in the red beds of the South African Karroo
Formation, these 3 specimens are the remains of creatures that once
flourished throughout a region that was considerably closer to the
South Pole during Permian times than it is now. In order to survive
the severe Karroo winters, they may have evolved some kind of
furry insulation. Although they were probably the first successful
group of herbivores among the vertebrates, equipped with horny
beaks and tusk-like upper canines, by the end of the Permian Period
to the Middle Triassic, the herds of Dicynodons (“Double Dog
Tooth”) had dwindled to extinction, survived by a few relatives
which evolved into early mammals. From the famous Karroo
Formation. University of California, Berkeley.
75. Subclass Therapsida,
Infraorder Gorgonopsia
Broomisaurus laticeps
Middle to Late Permian, South Africa
The saber-toothed gorgonopsids were a formidable group of lionsized protomammals (mammal-like reptiles) which included
Broomisaurus (“Broom’s Reptile”). With powerfully muscular
bodies and an upright mammalian stance that differed radically from
the low sprawl typical of reptiles, they dominated the land ecosystem
of South Africa from the Middle to Late Permian Period (245 to 225
million years ago). During this time the southern tip of the continent
was connected to Antarctica and located in a much colder region,
subject to harsh winters. Because the gorgonopsids (named for the
terrible gorgons of ancient Greek mythology) apparently thrived in
this climate, they are believed by many paleontologists to have been
warm-blooded.
Descended from the primitive synapsids that diverged from the
reptile family during the Early Permian, these advanced therapsids,
possibly the earliest vertebrates to show signs of rapid growth, were
the dominant land animals of their time, prowling the forests and
floodplains in bloody competition for territorial sovereignty.
University of California, Berkeley.