Jurassic Period

Other Life in the Jurassic

Besides dinosaurs, what other land animals were present during the Jurassic period?

Although the dinosaurs were the dominant animals, there were other animals that existed during the Jurassic period. Because of the relative stability of the climate and the lush vegetation, many land animals diversified and increased in numbers. But not all creatures survived through the Jurassic period; many became extinct, probably because competition for food increased. Below are short descriptions of the types of animals that existed at the time:


Frogs and salamanders: First modern frogs and salamanders appeared.


Turtles: First modern turtles appeared in the Early Jurassic period; they were able to retract their heads into their upper shell.

Lizards: First true lizards appeared in the Middle Jurassic period.

Crocodylians: First true crocodylians appear, and were small, three-foot-(one-meter-) long reptiles that walked on all fours; they had longer hind legs, indicating that their ancestors were bipedal.

Therapsids: Few families of therapsids, or mammal-like reptiles, lived into the Middle Jurassic period; the anomodonts and therocephalians no longer existed, but the cynodonts did survive into the Middle Jurassic.


Small mammals: Small mammals became more profuse and diverse during the Jurassic period; they were still very small animals, about the size of a mouse or rat, with the largest the size of a cat; they were mostly nocturnal.

Triconodonts: Late Triassic to Late Cretaceous mammals; one of the oldest fossil mammals; three cusps of teeth in a straight row give them their name.

Haramyoids: Late Triassic to Middle Jurassic mammals; one of the oldest fossil mammals; their teeth had many cusps in at least two parallel rows.

Symmetrodonts: Late Jurassic to Early Cretaceous mammals; they had upper and lower cheek teeth with many cusps in a triangular pattern.

Docodonts: Middle to Late Jurassic period mammals; they had elaborate cheek teeth, with most of the cusps in a T-shape.

A reef shark swims near the Bahamas. As far back as the Jurassic period, sharks swam in Earth’s oceans and were some of the deadlist predators of the deep (iStock).

Multituberculates: The multituberculates were the largest group of mammals in the Mesozoic, first appearing in the Late Jurassic period.


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