EARTH 7 Lecture Notes - Lecture 11: Plateosauria, Sauropoda, Plateosaurus
11/7/17
● Sauropodomorphs
○ Saurishchians??
○ Sauropodomorphs: prosauropods and sauropods
○ Scaling problems in sauropods
○ Sauropod behavior
● Saurischian
○ Lizard hipped
○ Forward-facing pubis
○ Ancestral condition
● Ornithischian
○ Bird hipped
○ Rear facing hips
○ Derived condition
● Sauropodomorphs have a forward facing pubis
○ The forward facing pubis is an ancestral condition, so it cant define saurischis.
This highlights why we depend on derived characters to establish evolutionary
relationships
● Herrerasaurus
○ Among the oldest dinosaurs known from fairly complete material
■ Small
■ Bipedal
● Sauropodomorphs
○ First known from mid-triassic
○ Dominant in jurassic, with worldwide distribution
○ Decline in cretaceous
○ Last groups to go extinct at the end of cretaceous
● Evolutionary novelties of sauropodomorphs:
1. Necks with at least 10 vertebrates
2. Small heads relative to body size
● “Prosauropods”
○ =before sauropods
○ Mid triassic - early jurassic
○ Relatively small
○ Earliest were bipedal, later were capable of both bipedal & quadrupedal
locomotion
■Prosauropod embryos and hatchlings
● These suggest “awkward limb” proportions at birth, extremely
rapid growth, and even evidence of “kicking” within egg.
○ Extremely rapid growth
●Plateosaurus, late triassic
○ Among the best known dinosaurs with over 100 skeletons discovered, including
many nearly complete
○ Even though this dinosaur has been known for a long time, our interpretation of it
has still changed in recent years
● Sauropods
○ Large and quadrupedal
○ Denser limb bones
○ Nasal opening on top of skull
○ Necks with at least 12 vertebrae
○ Even smaller heads
●Sauropod novelties
1. Denser limb bones -> to support lots of weight
2. Nasal openings on top of skull
a. Some recent studies suggest that even though sauropods had nasal
opening on the skull, their external nostrils may have still been near front
of head
3. Necks with at least 12 vertebrae
4. Even smaller heads (relative to body)
a. Small heads with relatively simple teeth and no molards (not much
chewing)
● Sauropod adaptations for long neck
1. Hollow spaces in neck vertebrae
a. This made the neck lighter, and likely had other functions, as well.
i. This is only for some sauropods (not diplodocids)
1. Note that even in diplodocids, which lack hollow spaces,
the vertebrae are still relatively low density
2. ‘Cable’ of ligaments held up head and neck
a. The cartilage, ligaments, and muscle within sauropod necks suggest that
they were not as flexible as commonly depicted. But this would have
facilitated more efficient grazing with tension buildup and release.
3. Sophisticated mechanisms for pumping blood to head
a. 400 kg heart? (900 lbs)
Document Summary
The forward facing pubis is an ancestral condition, so it cant define saurischis. This highlights why we depend on derived characters to establish evolutionary relationships. Among the oldest dinosaurs known from fairly complete material. Last groups to go extinct at the end of cretaceous. Evolutionary novelties of sauropodomorphs: necks with at least 10 vertebrates, small heads relative to body size. Earliest were bipedal, later were capable of both bipedal & quadrupedal locomotion. These suggest awkward limb proportions at birth, extremely rapid growth, and even evidence of kicking within egg. Among the best known dinosaurs with over 100 skeletons discovered, including many nearly complete. Even though this dinosaur has been known for a long time, our interpretation of it has still changed in recent years. Sauropod adaptations for long neck: hollow spaces in neck vertebrae, this made the neck lighter, and likely had other functions, as well. i.
