University of Colorado at Boulder and Emory University researchers have discovered scores of ancient reptile nests in Arizona's Petrified Forest National Park, believed to be the oldest such nests ever found.
The fossil nests, dating to about 220 million years ago, are similar to modern day crocodile and turtle nests, said Stephen Hasiotis, the CU-Boulder research associate who discovered them. Hasiotis and colleague Anthony Martin of Emory University in Atlanta believe the nests extend the fossil record of reptile nests by roughly 110 million years.
The 62 bowl-like depressions found by the researchers in sandstone deposits appear to be trace fossils made by large, hole-nesting reptiles such as phytosaurs (primitive, crocodile-like animals), aetosaurs (armored reptiles from that period) or possibly ancient turtles, said Hasiotis. A paper by Hasiotis and Martin was presented at the annual meeting of the Geological Society of America held Oct. 25 to Oct. 29 in Toronto.
Located on the shoreline of an ancient river system, the nests -- which average about 12 inches wide and 18 inches deep -- are similar to modern day crocodile and turtle nests. All the nests were above the ancient water line of the river, the researchers said.
"The evidence now indicates this type of nesting behavior in reptiles has been continuous from at least the Triassic Period to the present," said Hasiotis, who received his doctorate from CU-Boulder in 1997. Hasiotis, who specializes in trace fossils, has previously been credited with discovering the world's oldest crayfish fossils as well as the oldest, bee, ant and termite nests.
Expansions below the narrow surface openings probably were used as egg
chambers, which in some cases are overlain by broad, shallow and elliptical
depressions that may represent "body pits" made by the egg-laying females, said
the researchers. Several of the fossil chambers contain what appe
Contact: Stephen Hasiotis
University of Colorado at Boulder