Lecture 9 Flashcards
theropod phylogeny
(classification showing ancestor-descendant
relationships)
(Theropod Characteristics cont’d) Hollow bones-
honeycombed, air-filled (pneumatic)
bones make theropods substantially lighter.
- Within the bone interior, crisscrossing struts provide the
necessary support while keeping weight to a minimum
Theropod Characteristics
-compact & narrow
-bipedal (almost all)
-pes has 3 functional
digits and 1 offset
digit (hallux/‘big toe’) [almost all]
-grasping hands with
elongated digits
terminating in
curved claws
- furcula [all except most basal]
-large, curved &
laterally compressed
teeth with serrated
edges [most]
Phylogenetic
Classification
is rank
-less.
Each new grouping simply
denotes a new (novel)
evolutionary novelty (see slide 4)
Neotheropoda
includes almost all theropods with
the exception of the very earliest / most basal.
Evolutionary novelty = furcula
Tetanurans
include the vast majority of theropod dinosaurs.
Evolutionary novelty = a complicated air sac ventilated lung
system similar to what we see in modern birds
Tetanurans
Include the vast majority of theropod dinosaurs.
Evolutionary novelty = a complicated air sac ventilated lung
system similar to what we see in modern birds.
digit 4 is lost
Avetheropoda
evolutionary novelties include a larger, more complicated
air sac system and the development of a broad pubic boot.
The evolutionary novelties of
coelurosaurs:
-a bowed ulna
-tibia longer than the femur
-longer sacrum
-tail stiffened towards the tip (with ossified tendons)
-larger brains relative to body size
-a feathered integument (body covering)
Maniraptorans
The maniraptorans “grasping
hands” share these
evolutionary novelties:
-long arms and hands
-a semi-lunate bone in the
wrist (advanced maneuverability)
-a bony sternum (ossified
sternal chest plate)
-even larger brains relative to
size
Dilophosaurus
(“two-crested lizard”)
lived in North America 193 Ma. (early Jurassic
¡ This first large (7 m) theropod takes on
an apex predator role and thus begins
the ‘Age of Dinosaurs’.
Cryolophosaurus
Cryolophosaurus (“frozen crest lizard”) is an Early
Jurassic theropod (~190 Ma) known from the
Transantarctic Mountains of Antarctica.
Fanned crest on top of the skull
Carnotaurus
(“meat-eating bull”) is an abelisaur, a lineage of the
clade Ceratosauria. Abelisaurs have very robust, tall skulls and are
most characterized by their vestigial forelimbs.
-It is known from just a single, well-preserved skeleton
from Late Cretaceous strata in Argentina (~72 Ma).
Abelisaur Forelimbs
The abelisaurs forelimbs are so
reduced in size and function that
they are effectively vestigial.
Abelisaur Abundance
As Pangea rifted apart during the
Jurassic and Cretaceous, separated
landmasses led to a different suite
of dinosaurs in the southern
hemisphere to that of the northern
hemisphere.
- Throughout the southern
continents abelisaurs were
abundant during the Cretaceous
alongside the biggest of the
sauropods – the titanosaurs.
