Lecture 17 Flashcards
The largest known dromaeosaur is the heavily built (robust)
Utahraptor.
It lived in North America around 130 Ma. (early cretaceous)
Its robust rear limbs suggest it was more of an ambush predator (like the T-rex) than a pursuit predator like Velociraptor.
Deinonychus (dy-non-i-kes)
The Early Cretaceous dromaeosaur
Deinonychus (“terrible claw”) was discovered in the 1960s on an expedition to Montana by
Yale paleontologist John Ostrom.
Ostrom’s discovered the disarticulated partial remains of a number of theropods and their much larger prey (an iguanodontid called Tenontosaurus).
He speculated that a large pack attacked the
iguanodontid, and during the attack some members
of the pack were killed while the remaining members
eventually took down their prey.
A Dinosaur Renaissance sparked by John Ostrom and his PhD student Robert (Bob) Bakker’s discovery of the fast and agile Deinonychus led to their proposal that theropods were
Endotherms, like modern birds.
“It must have been a fleet-footed, highly
predaceous, extremely agile, and very active animal, sensitive to many
stimuli and quick in its responses.” - John Ostrom. He imagined the claw was used to cut down and disembowel their prey”
Endotherms “warm-blooded” - generate their
heat through their metabolic activities
Ectotherms “cold-blooded” – rely on
heat from external sources (the Sun)
eg. reptiles
Rapid Coelurosaur Diversification
By the Middle Jurassic, all coelurosaur
clades were established. In the
northern hemisphere, coelurosaurs
outcompeted and quickly diversified
and dominated.
Encephalization Quotient
Amongst all dinosaurs, members of the coelurosaurs have the
largest brains relative to body size.
Amongst dinosaurs, theropods and ornithopods have the highest EQ.
- Measurements of the brain cavity can provide us with an estimate of
EQ (encephalization quotient).
Need:
brain mass
body mass
EQ= E(actual)/E(average)
Troodontidae
Our final look at the non-avian
theropods brings us to the most
closely related group to avialae –
the sister clade called
troodontidae
Troodontids share all the
evolutionary novelties of paraves
and are characterized as having
large numbers of closely
spaced teeth in the lower jaw.
Mei long
Mei long (“soundly sleeping dragon”) is a basal troodontid from
the Early Cretaceous Liaoning Yixian Formation beds (125 Ma).
It is known from 2 specimens,
both preserved in a roosting
position (tucking head into forelimb) hence where the name comes from
Troodon (Troh-uh-don)
Troodon (“wounding tooth”) is a
more derived and larger troodontid
that lived during the Late Cretaceous
in North America (75 Ma).
- Fossils are mainly teeth with very few
skeletal elements, found in Alaska,
Alberta, and to the south.
Quill knobs preserved on Dakota raptor suggest that
all dromaeosaurs regardless of size were feathered
