Fossil evidence has been found for all of the following in Petrified Forest.
Drepanosaurs, tanystropheids, and Vancleavea
Drepanosaurs are bizarre reptiles are generally small and are known from exquisite specimens from the Triassic limestone quarries in Europe. They may have behaved much like modern chameleons or squirrels;they generally had large, hooked claws on their hands and prehensile, grasping tails. At the park, drepanosaurs are known from these claws and their vertebrae.
Tanystropheids are also small reptiles, but they tend to have extraordinarily long necks that are longer than the rest of the body. Vertebrae from these animals are very recognizable, and we have only recently been finding them in the field.
Vancleavea was named after Phillip Van Cleave, a former Chief Naturalist at Petrified Forest who collected the fragmentary postcranial remains of this small reptile in the early 1960s.
What we know about the origins of early lizards and snakes comes from Triassic microvertebrate fossils. Because many of these animals were so small and delicate, most of the lepidosaurs from Petrified Forest are recognized through their teeth, which are implanted on the insides or tops of the upper and lower jaws. Looking for lizard jaws is tedious work; paleontologists must wash bags of rock through sieves of various sizes before spending hours picking out fossils from under high magnification.
AllokotosaursMembers of this diverse reptile group include Trilophosaurus and Azendohsaurus. Trilophosaurus is incredibly abundant from the Triassic-age rocks in western Texas. It was a herbivore up to 8.2 feet (2.5 meters) long. It had a short, unusually heavily-built skull, equipped with massive, broad, flattened cheek teeth with sharp, shearing surfaces for cutting up tough plant material. The name "Trilophosaurus" means "three-ridge reptile" and refers to its strange teeth that have three tall crests. Azendohsaurus is known from what is now Madagascar, but a closely related animal once lived at Petrified Forest, as well.
Phytosaur fossils are some of the most abundant vertebrate fossils in the park. These long-snouted reptiles are closely related to archosaurs. They look very much like the modern crocodylians, but there are several things that differentiate phytosaurs from crocodylians. First, the nostrils of phytosaurs are located high up on the skull, almost between the eyes! Second, phytosaurs do not have a complete bony roof over the mouth. Third, phytosaurs have a paired row of armor scutes down their back, unlike crocodylians that have multiple rows. Two of the phytosaurs that you would encounter at Petrified Forest in the Triassic are named Smilosuchus and Machaeroprosopus.
Last updated: April 18, 2016