EARTH 7 Lecture Notes - Lecture 14: Mosasaur, Plesiosauria, Mesozoic
11/21/17
● Dinosaur Contemporaries
○ Noteworthy vertebrates living alongside dinosaurs
■ Marine behemoths: ichtyosaurs, plesiosaurs, and mosasaurs
● diapsids
■Crocs and croc relatives
■ Pterosaurs
■ Mammals
● Mass extinction 250 MA
● Dominant groups in the triassic
○ Synapsids
■ Synapsids were hit hard in the end-permian mass extinction, but the few
surviving groups rebounded quite well. Mammals eventually evolve
from this group at the end of the triassic
○ Crocs + kin
● Archosaurs diversify at the beginning of the mesozoic
●Ichthyosaurs
○ Fish lizards
○ First known from early triassic become dominant in jurassic oceans
○ Go extinct in the mid cretaceous
■ Carthorhyncus lenticarpus
● New species in 2014
● Early triassic of China
● Lacks long snout
● Amphibious
○ Some species grew about 70 ft long
○ Highly convergent with dolphins
● Plesiosaurs
○ First known from late triassic
○ Become dominant in jurassic and cretaceous oceans
○ Go extinct at the end of cretaceous (mass extinction)
○ Necks up to 50 ft long
■ Many also had short necks
○ Sea turtles → modern analog in terms of swimming style
● Mosasaurs
○ Become dominant at the end of the cretaceous (short fossil record)
○ Ichthyosaurs had gone extinct, and plesiousaurs were declining. Mosasaurs fill
the ecological gap.
○ But go extinct at end of the cretaceous (mass extinction)
○ 60 ft long aquatic lizard
■ Possibly ancestors of snakes
● Archosaurs diversify at the beginning of the mesozoic.
Document Summary
Synapsids were hit hard in the end-permian mass extinction, but the few surviving groups rebounded quite well. mammals eventually evolve from this group at the end of the triassic. First known from early triassic become dominant in jurassic oceans. Become dominant at the end of the cretaceous (short fossil record) Ichthyosaurs had gone extinct, and plesiousaurs were declining. But go extinct at end of the cretaceous (mass extinction) Archosaurs diversify at the beginning of the mesozoic. Some species grew about 70 ft long. Become dominant in jurassic and cretaceous oceans. Go extinct at the end of cretaceous (mass extinction) Sea turtles modern analog in terms of swimming style. Many of these are croc relatives but not all. Crocs + kin were especially dominant in the triassic , but obviously there was still a diversity of jurassic and cretaceous species. Some groups become less abundant in the cretaceous (as birds began diversifying)
