Dinosaur Origins Flashcards
What are fenestrae?
Additional openings in the skull that don’t house additional sensory organs
What are the three lineages of amniotes based off their skulls?
anapsids, synapsids, and diapsids
What types of animals are synapsids?
Mammals and mammalian ancestors
What is the well known synapsid from the permian period?
Dimetrodon
What type of amniote are dinosaurs?
Diapsids
What are the subgroups of Diapsids?
Lepidosauromorphs (no more additional fenestrae) and Archosauromorphs (Diapsids with an antorbital fenestra and the mandibular fenestra)
Which animals are archosaurs?
Crocodilians, birds, dinosaurs and pterosaurs
What group within archeosaurs do dinosaurs and pterosaurs belong to?
Avemetatarsalians
What is the evolution that distinguishes avemetatarsalians?
Ankles that flex like a hinge rather than like a ball and socket, better suited for upright locomotion
What is the group aside from avemetatarsalians?
pseudosuchians
Which group of aminotes dominated the ecosystem during the permian period?
Synapsids, dimetrodon
What were the major synapsid predators during the permian?
Gorgonopsids
What were the major herbivores during the permian?
Dicynodonts
What synapsid from the permian is the ancestor of current-day mammals?
Cynodonts
What was the most devasting extinction event in history?
The end-permian extinction
Is the cause of the end-permian extinction fully known?
No, we cant be certain
Which lineage of amniotes took over the major parts of the ecosystem in the Triassic after the mass extinction?
Diapsids (Archosaurs)
Which lineage of the archosaurs was most dominant during the Triassic?
pseudosuchians (crocodilians)
What did the earliest dinosaurs-like archosaurs look like?
Small and Bipedal, no perforated acetabulum
How old are the oldest dinosaur fossil bones?
228 million years old
What allowed dinosaurs to dominate over pseudosuchians in the Jurassic?
end-triassic mass extinction that hit pseudosuchians hard
What were the early carnivorous dinosaur?
Eorapter, Eodromaeus, Herrerasaurus, and Panphagia
What was the early herbivorous dinosaur?
Pisanosaurus
What was the largest early dinosaurs specimen?
Herrerasaurus
What distinguishes dinosaurs from dinosaur-like archosaurs?
The perforated Actabelum
What were the early dinosaur-like archosaurs called?
Dinosauromorphs
