150 million years ago, a prehistoric reptile unlike modern lizards slithered around what is now Wyoming. The discovery of this ancient rhynchocephalian insectivorous animal could shed light on the persistence of its living relative, the tuatara.
Call me creeper Opisthiamimus gregori. It looks like a lizard, but it is not the same as the tuatara in New Zealand. Lizards are scales, an order of reptiles that includes snakes and wormlike lizards. Rhynchocephalians are a distinct group that diverged from lizards in the Triassic period.
excavations Opisthiamimus They come from Wyoming, where they sat atop what was once an Allosaurus nest. Paleontologists found four specimens at the site, including a nearly complete articulated skeleton of a reptile. The newly discovered species is described in a study published Today in the Journal of Systematic Paleontology.
“what or what [the fossil] “Does this check the fact that rhynchocephalians have been a very diverse group in much of their evolutionary history,” study co-author Matthew Carano, curator of dinosaurs at the Smithsonian’s National Museum of Natural History, said in an email to Gizmodo. “There is likely more ‘hidden diversity’ out there, as many of the fossils are small, fragmented, and difficult to identify.”
Last year, scientists described the name rhynchocephalian Taitalura Alkoberiwhich helps explain the evolutionary difference between the order of reptiles and insects. Taitalura It is known only from a well-preserved skull, but the youngest Opisthiamimus He has a nearly complete skeleton. Its discovery depends on Taitalura By showing that the order of reptiles was diverse relatively early in a deep time.
“I agree with the authors that this is an important finding from the Morrison Formation,” Harvard evolutionary biologist Thiago Simoes, who was not affiliated with the latest research paper, said in an email to Gizmodo. Simes was one of the researchers who worked on it Taitalura.
Opisthiamimus It is very old and pre-existing Tyrannosaurus Rex 60 million years. She lived in the late Jurassic period, side by side Archeopteryx And the stegosaurus (Although it is closer to the ground than the previous two, and much smaller, measuring just 6 inches from nose to tail.)
The only rhynchocephalian found is tuatara, which is part of a subgroup called sphenodonts, of which there are two types. A tuatara can live more than 100 years and has The fastest moving sperm from any reptiles. It has a parietal eye in the middle of its forehead and three rows of teeth: two in its upper jaw and one in its lower jaw. Unlike other reptiles, the rhynchocephalian teeth are part of its jaws, and not separate replaceable elements.
Because of its unique anatomy, tuatara is often referred to as a “living fossil”. He continued when all the other members of the system could not. But don’t call it primitive: I simply found a winning formula for survival and stuck with it.
“I would be cautious with the evolutionary interpretation that the authors gave for this species,” Simois added, noting that the features of Opisthiamimus They are more typical of sphenodontians that appear later in the fossil record.
Finding more ancient reptile fossils could help explain why scales continue to be abundant on Earth while rhynchocephalians do not.
“One theory is that one or more of the unique traits of the weeds allowed them to outcompete the descendants of the rhynchocephalians,” Carano said. “There is a broad pattern of gradual decline in rhynchocephalians along with a gradual increase in squamous diversity. But competition is taking place within environments, and at the moment we don’t have enough fossils to really research that idea, although we are getting close in a place like the Morrison Formation. “.
Now, the team is sifting through the leftover Allosaurus Nest is found below Opisthiamimus. More rhynchocephalian fossils await discovery, in the Morrison Formation and beyond. When they appear, they can help us decipher the reptile’s family tree.
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