mammals

Mesozoic Earth History II
Triassic, Jurassic and Cretaceous evolution
Synapsids (mammals)
Diapsids (birds and dinosaurs)
Angiosperms (flowering plants)
Modern Global Vertebrate Diversity
Taxa
Species
Chondrichthys
Elasmobranchii
Taxa
Species
Amphibians
810
Osteichthys
frogs/toads
4,300
salamanders
425
Teleostei
25,000
“Reptiles”
Other
50
turtles
260
Total:
25,860
snakes
2,700
lizards
3,900
crocodiles
21
Birds
9,100
Mammals
4,700
Total:
25,406
All major modern
vertebrate groups
appeared first in the
Mesozoic
The Triassic Earth
Mesozoic Era
Cretaceous Period
Jurassic Period
Triassic Period
The aftermath of the endPermian Extinction knocked
the world’s ecosystems for a
5-10 million year long loop.
When the dust settled in the
later Triassic, the Paleozoic
world was gone, replaced by
new orders of animals and
plants.
The first recognizable
members of a large number
of modern taxa appeared
during the Triassic.
Cretaceous Period
Mesozoic Era
Osteichthys
1st Teleost (modern fish)
Jurassic Period
Anapsida
1st Turtle
Synapsids
1st mammal (Morganucodon)
Diapsida
Triassic Period
1st Crocodile
1st Sphenodont reptile
Cretaceous Period
Mesozoic Era
Amphibia
1st Frog
Jurassic Period
1st Salamander
Diapsida
1st Bird
1st Lizard
Triassic Period
Synapsids
Cretaceous Period
1st Monotremes
Mesozoic Era
1st Marsupial
1st Placental mammal
Diapsida
Jurassic Period
1st Snakes
1st Unambiguous Flowering Plant
Triassic Period
Flowering Plants
Angiosperms are a
fantastically successful and
diverse plant group.
While arguable fossils and
angiosperm-type pollen exist
in earlier strata, the only
undoubted body fossils of
angiosperms are Cretaceous.
http://www.mobot.org/MOBOT/Research/APweb/
First Bird
The oldest known member of
the avian clade, Archaeopteryx
was built on the same body
design as a small dinosaur. It
had both teeth and a tail, as well
as other dinosaur features.
Archaeopteryx
Deinonychus (dinosaur)
http://www.ldeo.columbia.edu/dees/courses/v1001
Solnhofen Limestone
Jurassic lagerstatten in Germany. The rock is a very fine grained light-colored
limestone deposited in an anoxic lagoon close to shore. Marine and (rare)
terrestrial fossils are preserved in exquisite detail.
http://www.wf.carleton.ca/
Solnhofen Limestone
Archaeopteryx
The Solnhofen limestone
has produced several fossil
skeletons of Archaeopteryx,
the first bird.
Several bits and pieces
(e.g., individual feathers)
have also been found.
http://rainbow.ldgo.columbia.edu/courses/v1001/15.html
The front limbs are far larger
in relationship to the body
than its dinosaur cousins.
http://www.dinoeggs.com/
Both the front limbs and tail
supported feathers.
The breastbone was also
keeled, just like a modern
bird’s.
http://www.dinoeggs.com/
Synapsids
The last time we checked in
on the synapsids, they had
re-diversified after the P/Tr
extinction.
The late Triassic saw the
evolution of the most
mammal-like of the
mammal-like reptiles.
By the latest Triassic, the
first true mammal appear.
http://www.palaeos.com/Vertebrates/Units/Unit390/000.html
“Advanced”
Mammal-like
Reptiles
Cynognathus, an advanced
non-mammalian therapsid.
© J. Conrad, 2000
Cynognathidids and tritylodonts
(superficially resembling dogs and
rodents) lacked the rib structure of
true mammals.
The triylodonts co-existed with
true mammals through 50 Ma of
the Mesozoic.
http://www.geocities.com/CapeCanaveral/Hall/1636/synapsida/therapsida.html
Morganucodon
http://biociencias.com/preguntas/respuestas
Late Triassic
The first mammal
Small, shrew-like animal
http://www.abdn.ac.uk/mammal/first.htm
Morganudocon had no ribs on the
lumbar vertebrae - indicating the
presence of a diaphragm just like all
mammals.
http://www.museums.org.za/
Sinodelphys
Early Cretaceous
Liaoning Province of China
Oldest known
marsupial
http://www.carnegiemnh.org/news/03-oct-dec/sinodelphys/
Eomaia
Early Cretaceous, ~ 125 Ma
Reconstruction based on a recent (2002) fossil find from
China. The teeth indicate that this little mouse-sized creature
was an early relative of the first placental mammal.
Qiang, J. Z-X Luo, C-X Yuan, J.R. Wible, Z-P Zhang, J.A. Georgi. 2002. The earliest eutherian mammal. Nature 416: 816-822.
http://www.carnegiemuseums.org/cmnh/research/eomaia/
Eomaia
http://www.carnegiemnh.org/news/02-mar-apr/eomaia/eomaiascansoria.htm
http://dinosauricon.com/
image © 2001 Todd Marshall
All of those groups became important later in the history of life on Earth,
but the Mesozoic is the Age of the Dinosaurs!
http://www.dinooption.com/din03/di006-001-04.htm
http://www2.worldbook.com/
http://yahooligans.yahoo.com/
http://faculty.plattsburgh.edu/thomas.wolosz/sauropod.htm
crocodiles
birds
snakes
lizards
sphenodonts
Living Diapsid
Clades
Modified from: M.J. Benton 2005.
Vertebrate paleontology. Blackwell.
Ornithischia versus Saurischia
The easiest way to distinguish one dinosaur group from the other
is to examine the pelvic structure.
Saurischia (lizard-hipped) - pubis points forward, except for in
the bird clade (birds are bird-hipped, but not ornithischians)
Ornithischia (bird-hipped) - pubis bone points backwards, resting
against the ischium, and increasing the space for intestines
head
tail
Saurischia
Ornithischia
http://www.sdnhm.org/exhibits/lostworld/
Ankylosaurs and Stegosaurs
Sauropods
Ornithopods
Ceratopsians and
Pachycephalasaurs
Theropods
birds
http://dinosaur.uchicago.edu/SmallClade.html
Ornithopods
Ankylosaurs
Sauropods
Ceratopsians
Stegosaurs
Sereno, P. 199. The evolution of dinosaurs. Science 284: 2137-2147.
Theropods
The theropod clade contains
all dinosaur predators, from
tiny to enormous.
The sauropod clade contains
the first large dinosaur
herbivores, and even midsized species were among the
largest land animals that ever
lived.
The ornithiscian clades
diversified in the Cretaceous
into a dizzying array of forms.
Dinosaur Family Tree
http://www.austmus.gov.au/
Coelophysis
Triassic Theropods
Coelophysidae - small dinosaurs
appearing in the late Triassic
http://dinosauricon.com/
There is abundant fossil evidence
of small, fast carnivores, including
at least one huge deposit of
bones.
Fossilized footprints like those on
the top row to left are also
common (bottom row contains
turkey tracks for comparison)
Gatesy, S.M., K. M. Middleton*, F. A. Jenkins, Jr., and N. H. Shubin. 1999. Three-dimensional preservation
of foot movements in Triassic theropod dinosaurs Nature 399: 141 – 144.
Unlike some later large
theropods, Allosauridae had
large, functional arms.
Cretaceous “Raptors”
Bambiraptor
Small carnivorous theropod
of the Cretaceous.
http://www.bowdoin.edu/~dbensen/Dinosaurs/Bambiraptorfeinbergi.html
http://www.bambiraptor.com/
Cretaceous “Raptors”
Deinonychus was a much
larger raptor, with a very large,
deadly claw on the back legs.
Artists can’t resist making this
animal look vicious.
image © 2001 Orlando Nelson Grillo
image © 2001 Todd Marshall
image © 2001 Richard D. Dobbs Jr.
http://dinosauricon.com/
Triassic Sauropods
The sauropods evolved in
the Triassic from bipedal
ancestrors like the
prosauropods.
image © 2001 Richard D. Dobbs Jr
Plateosaurus
Prosauropods (sister group to sauropods) from the late Triassic.
Probably walked on all fours, but capable of walking on hind legs.
Relatively large for the Triassic - 20-35 feet long, weighing a ton or
more
http://dinosauricon.com/
Jurassic Sauropods
The longest, heaviest, and tallest animals
of the Jurassic were all sauropods.
http://www.jpinstitute.com/
Cretaceous Sauropods
In the late Cretaceous the Titanosaur
family diversified. Contrary to the
name, most species were smaller
than their Jurassic cousins.
1m
Rapetosaurus, with body outline. ©
Mark Hallett; SUNY-Stony Brook.
Ornithiscian Taxa
These two groups had
unimpressive teeth, and
probably ate rather soft plant
material. They walked on all
fours.
Ankylosaurs – armored
herbivores with an impressive
weapon attached to the tail
Stegosaurs – distinguished by
having the smallest brain of
any dinosaur relative to its
body size, these herbivores
frequently sported both spines
and upright plates on their
backs and tails.
These three groups had some very
impressive dental equipment for
processing tough plant material
Ornithopods – mostly bipedal
herbivores ranging in size from
small to medium (for dinosaurs).
Pachycephalids – Very similar to
ornithopods, but with massively
reinforced skulls and necks,
probably for smashing into things
like rams.
Ceratopsians – “Frilled” dinosaurs,
with large, bony extensions to the
back of the skull. Primarily walked
on four feet.
Ankylosaurs
These armored dinosaurs usually
had a big club on the end of the tail.
How they used it without killing
themselves is somewhat of a
mystery (their brains were very small
and far away from the tail).
http://home.no.net/paleo/
Stegosaurs
Species in this family had upright plates
staggered along the spine, the function of
which is much theorized upon.
Many also have spikes on the back and
tail, which clearly served some kind of
defensive/offensive function.
Ornithopods
The Mesozoic equivalent of modern ungulates, the ornithopods were a
highly diverse and successful group. They are characterized by an
impressive dental battery and associated jaw structures.
http://home.fuse.net/paleopark/foss3.htm
Half of an ornithopod lower jaw showing large numbers of teeth.
A single animal could have hundreds of these constantly replaced
teeth. The lower and upper jaw worked together to turn even tough
plant stems into pulp.
Ornithopods
Because of a vague resemblance of the skull to a duck’s skull (at least
from the top), this group is frequently called “duck-billed” dinosaurs. There
is no real resemblance: ducks eat soft water plants, while these megaherbivores had the teeth to eat anything short of wood.
http://paleo.amnh.org/
Ornithopods
image © 2001 Andrey Atuchin
Ornithopods frequently sported
large head crests. The nasal
cavities extended into these
spaces.
http://www.dinooption.com/din03/di006-001-04.htm
image © 2001 Christopher Srnka
http://dinosauricon.com/
Based on trace fossil evidence,
many ornithopods lived in large
herds, and had communal
hatching grounds.
Ceratopsians
This very successful group evolved
from small ornithiscians (like these
two) that had small bony frills attached
to the back of their skulls.
The extensions allowed the
attachment of larger jaw muscles.
image © 2001 Todd Marshal
Microceratops
© Joe Tucciarone
http://dinosauricon.com/
Ceratopsians
Triceratops exemplifies the
ceratopsian body form – with a
head over ten feet long (the
longest head of any land
animal) and a solid, bulky
skeleton.
The strong beak and massively
powerful jaws and teeth could
have sheared through tough
wood, and would have made
short work of anything softer.
© Frank DeNota
http://members.aol.com/triceratopO1/ceratop.html