Major groups of dinosaurs and the hip mini-assignment
For details on the hip, read pages 51-55 and 343 of your textbook (Dinosaurs by Lucas).
1.
One important dinosaurian synapomorphy is the perforate (pierced or open) acetabulum
, simply
a "hip bone" (actually three connected bones, together called the pelvis) with a hole in the center where the head of the femur ("thigh bone") fits. What are the three bones that comprise the pelvic girdle (
e.g., “hip bone”)? (2 pts)
i.
Ilium
ii.
Ischium
iii.
Pubis
iv.
What do we call the opening between these three bones?
Acetabulum
2.
Dinosauria contains two major groups of dinosaurs: the Ornithischia
, or "bird-hipped,” and the Saurischia
, or "lizard-hipped," dinosaurs. The most prominent difference between the two types of hip is the orientation of the pubis. For each group, indicate whether the direction (anterior or posterior) the pubis generally projects from the pelvic girdle. (1 pt)
i. Ornithischian: The pubis projects posterior to the pelvic girdle.
ii. Saurischian: The pubis projects anterior to the pelvic girdle.
3.
Click the hyperlinks and observe the orientation of the pubis within the pelvic girdle on the following dinosaur skeletons and indicate if the dinosaur most closely resembles a general saurischian or an ornithischian
pelvic girdle. (5 pts)
i.
Tyrannosaurus
: Saurischian
ii.
Stegosaurus
: Ornithischian
iii.
Brachiosaurus
: Saurischian
iv.
Mussaurus
: Saurischian
v.
Triceratops
: Ornithischian
4. Modern birds are “bird-hipped;” however, their ancestors (i.e.
,
the theropods) were “lizard-hipped.”
How does the pelvic girdle of the Greylag Goose (
Anser anser)
differ from that of a basal theropod, such as Herrerasaurus
? (2 pts)
The pelvic girdle of the Greylag Goose would resemble those of a bird-hipped dinosaur.
In contrast, the a basal theropod like Herrerasaurus would have a lizard-hipped pelvic girdle.
