lecture 13: Theropoda part 1 Flashcards
Theropods, general description
Have been present since the late triassic, they were obligate bipeds, often carnivorous, relatively large brained and only group of dinosaurs with living members
What was the first non bird theropod?
Megalosaurus
What was the first Theropod in North America?
Deinodon, Troodon
What was the first complete fossil found?
compsognathus
First feathered theropod?
Archaeopteryx
Theropoda named by O.C. marsh, at first only included one family, called?
Allosauridae
It is now the most inclusive clade
Proposed distinguishing features for theropoda
- Intramandibular joint in lower jaw
- Hollow bones
- hands with reduced or absent outer digits, long phalanges and hooked claw
- End of pubis narrow side to side
Theropod origins
Ischigulasto formation of Argentina
Diverse early dinosaurs: Herrerasaurus, eoraptor, eodromaeus
Neotheropoda
“new theropods”, oldest are about 220 mya, co existed with non-neotheropod carnivorous dinosaurs
Distinguishing features:
-Furcula (wishbone) present
-longer illium and sacrum present
-1st metatarsal short, does not articulate with ankle
What is the best known triassic theropod?
Coelophysis
Coelophysis at Ghost Ranch, NM
Lots of individuals of varying size, good articulation
Sexual dimorphism proposed for adults: gracile and robust morph
Stomach contents include small crocodylomorph archosaur
Predators of triassic theropods
Large terrestial archosaurs related to crocodiles (prestosuchus)
End- triassic extinctions
Complex faunal changes in terrestial realm, not a single and sudden mass extinction
Extinction of:
-non crocodylomorph croc relatives
-non neotheropod carnivorous dinosaurs
Early Jurassic
theropods dominate the land
Early jurassic tracks
Megatheropod tracks reported from Lesotho, southern Africa. Allosaurid like theropod
Early jurassic ichnolagerstatte
St. george utah, tracks of wading and swimming theropods inhabiting a lakeshore environment
The middle jurassic
Second major radiation of theropods
Major Faunal turnover
Early jurassic: “prosauropods” as the dominant terrestial herbivores; a few primitve sauropods and ornithischians
Middle jurassic: no more “prosauropods” earliest examples of Stegaurs, ankylosaurs, ornithopods,neosauropods
Averostra
“bird snout”
Completely replaced all earlier theropod lineages
Unites two theropod clades that would exist for the rest of the mesozoic: ceratosauria and tetanurae
Tetanurae
“stiff tail”- Elongation of interlocking projections called zygopophyses
Enlarged hand with modified wrist and only 3 digits, large claw on inner digit. Megalosaurus, early member of tetanurae
Proceratosaurus
Single specimen found in England
oldest known Coelurosaur
early member of tyrannosauroidea: about 100 mya older than tyrannosaurus rex
Megalosaurs common in ______ environments and Allosaurids more ______ inland
Nearshore; inland
the late jurassic
Great diversity of body size & types, first birds
Ceratosauria
Diverse averostrans with often bizarre skulls, small hands with 4 stubby digits
