Chapter 8: Hips & Pelves Part 2

Saurischia

1. What defines Saurischians?

• Pubis points forward (ancestral trait).

• Elongated thumb.

• Divided into Theropoda (carnivores) and Sauropodomorpha (herbivores).

2. What are key characteristics of Sauropodomorphs?

• Small skulls, long necks, peg-like teeth.

• Two groups:

  • "Prosauropods" – Smaller, bipedal/quadruple stance, earlier forms.

  • Sauropods – Gigantic, fully quadrupedal.

3. What made sauropods successful?

• Pneumatic (air-filled) bones to reduce weight.

• Columnar legs for weight support.

• Continuous tooth replacement.

4. What is allometry, and why is it important in large dinosaurs?

• Allometry is how shape changes with size.

• Larger animals need proportionally thicker bones to support weight.

5. What are Graviportal adaptations?

• Adaptations for supporting large body mass, including:

  • Thick, column-like legs.

  • Even length of thigh and calf bones.

6. What are the major theropod groups?

• Ceratosaurs ("horned lizards") – Cranial ornamentation, reduced fourth finger.

• Spinosaurs – Fish-eating, crocodile-like skulls, possibly semi-aquatic.

• Coelurosaurs – Feathers, stiffened tails, includes birds.

7. What is the significance of Yutyrannus?

• A large, feathered tyrannosaur, showing that insulation was present in some big theropods.

8. What is the maxillary fenestra, and why is it important?

• A skull opening unique to tetanuran theropods (e.g., Allosaurus).

• Helps lighten the skull and strengthen biting power.

9. What evidence suggests theropods were ancestors of birds?

• Feathers (Sinosauropteryx, Archaeopteryx).

• Hollow bones for lightweight structure.

• Fused clavicles ("wishbones").

10. What was Yi qi, and why was it unusual?

• A theropod with bat-like wings, suggesting that some dinosaurs experimented with gliding.