GEOL 105 Lecture Notes - Lecture 24: Diplodocus, Macronaria, Argentinosaurus
23 Apr 2020
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Lecture 24: Dinosaurs, Sauropods, and Ornithischians
●Sauropods
○ Late triassic to cretaceous
○ Largest of Land Animal
■ Food was low quality
■ Cycads, conifers
■ Low digestibility
■ Lower Nutrient content= Terrible Diet
○ Wide range in size
■ 4-40m in length
○ Quadrupedal
○ Herbivores
○ Two Clades of Sauropods
■ Diplodocimorpha
● Diplodocids
○ Diplodocids had:4 equal length legs, eyes to the back of the
skull, and peg teeth in the front.This suggests they grazed on
ground fern leaves which they pulled off the stems (grab base,
put strands between teeth and pull, leaves come off)—most
efficient and left eyes still facing outward to look for predators.
■ Macronaria
● Brachiosaurids
○ Brachiosaurs had: -peg teeth all around-longer front legs than
back-a skull that suggest their head was held high.Probably ate
leaves off of trees (fern trees? Conifers), can have teeth all
around because branches stick out sideways as well as in front
of them.
○ Front legs are considerably longer
■ 12 m (39 ft) tall and 23 m (74 m long)
○ Body Size and Food quality
■ Large size=lower metabolic rate =lower relative food needs
■ Large size=lower predation pressure
● = more time to feed
● = specialize on lower food quality
○ Sauropod anatomy
■ Two foot bones
■ Gizzard
● Pouch with stones in it to ground up leaves they ate before they passed
to the stomach
■ Open neck structure
○ Seismosaurus
■ Length: about 150 feet (45 meters)
■ Weight: 40-70 tons
■ Time: Late Jurassic
○ Argentinosaurus
■ Largest dinosaur
