Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Jason Meinhardt
In 1996, geologist Stephen Hasiotis discovered 62 fossilized nests, which were
dug into the earth and turned to stone over time. These nests were probably dug
out by phytosaur, now extinct, or aëtosaur (spiked, well-armored land-dwelling
creatures who appeared similar to crocodiles).
Phytosaur, which means “plant lizard”, are extinct aquatic reptiles that resemble crocodiles, but had nostrils near the eyes. They had short legs, a long tail, and many sharp teeth in a long snout. A different name that has been applied which some feel is more accurate is “Parasuchia” which means ‘alongside crocodiles’ because of the resemblance, but it is seldom used.
Phytosaur are divided into two subfamilies, Mystriosuchinae and Angistorhininae.
Angistorhininae include phytosaurs like nicrosaurus and rutiodon. A heavier
build and deeper, wider jaws characterize them. They had serrated fangs as well
as crushing teeth further back in the jaw, conically shaped. We can determine
that this creature fed on large animals, including other reptiles.
(Late Triassic found in Arizona)
Labels show external nostrils.
Triassic found in Texas)
The second group, the Mystriosuchinae, are the more primitive phytosaurs and include mystriosuchus and parasuchus. Based on their skull designs, it is believed that they dined predominantly on fish. Their skulls were very long and slender like today’s gavials, and their snout was tipped with large, hook-shaped fangs with the rest of the jaws filled with conical teeth well adapted for catching fish.
Phytosaur are not actually dinosaurs, but early thecodonts, which are
various extinct primitive
archosaurs of the late Permian and Triassic periods, having teeth in sockets and
probably ancestral to the dinosaurs. Phytosaur specifically late Triassic, 222
– 215 million years ago.
They grew up
to five meters long and may have built nests and protected their eggs.