1. What Makes a Dinosaur?
Ralph E. Chapman
Eryops Consulting
LAVA Technologies

2. What is a Dinosaur?
dinosaur = member of a very specific group of animals
• lived during a restricted period of time
• had diagnostic anatomical features
dinosaur ≠ fossil
dinosaur ≠ extinct animal

3. Geologic
Time

4. What is a Dinosaur?

5. Tetrapod Phylogeny

7. ichthyosaurs
plesiosaurs
lizards &
snakes
crocodylians
diapsids pterosaurs
archosaurs
The Origin of Dinosaurs
dinosaurs &
birds

9. The Origin of Dinosaurs
“protodinosaurs”
crocodylians
dinosaurs &
pterosaurs
other
birds
archosaurs
other
archosaurs
other
archosaurs
archosaurs

10. The Origin of Dinosaurs
“protodinosaurs”
Middle
Triassic
Marasuchus
small
carnivorous
facultative bipeds

11. What Makes a Dinosaur?
Definition of the Dinosauria: most
recent common ancestor of
Triceratops and neornitheans
(modern birds) and all of its
Diagnosis of the Dinosauria:
• 3 or more sacral vertebrae
• glenoid faces caudally
• acetabulum completely open medially
• femur with ball-shaped head on proximal end

12. What Makes a Dinosaur?
• 3 or more sacral vertebrae
Plateosaurus
lateral view
dorsal view

13. What Makes a Dinosaur?
• glenoid faces caudally Acrocanthosaurus
dorsal
cranial
ventral
Allosaurus

14. What Makes a Dinosaur?
• acetabulum completely open medially dorsal
cranial
dorsal
ventral
cranial
ventral
Euparkeria
Allosaurus

15. What Makes a Dinosaur?
• femur with ball-shaped head on proximal end
Postosuchus Apatosaurus
Tyrannosaurus

16. The Earliest Dinosaurs
Herrerasaurus
Eoraptor

17. Box 08-05

18. Oviraptorosaurs

19. What is a Dinosaur?
BIRDS ARE DINOSAURS!
– i.e., birds are
descended from
dinosaurs

20. Dromaeosaurs

21. Aves
• oldest bird = Archaeopteryx
- Greek arkhaios = ancient; pteryx = wing
- 8 specimens known, all from Late Jurassic, Germany

22. What Makes a Dinosaur?
Ralph E. Chapman
Eryops Consulting
LAVA Technologies