A graduate student browsing the specimen drawers at Yale's Peabody Museum of Natural History has found a skull of a small lizard - leading to the discovery of a new species.
Simon Scarpetta from the University of Texas at Austin found the skull of a small lizard - still in a generally good condition, its jaw still lined with sharp teeth. Some of the teeth were found to have a distinct curve.
The small lizard skull, surprisingly, was not yet studied. Dated at 52 million years old, the specimen had been left in the drawers since it was discovered on a fossil recovery expedition in Wyoming in 1971.
The saga of the "perplexing" lizard skull sounds like a Halloween ghost story. But this new species, which was named and described by JSG grad student @SimonScarpetta , has some very real lessons for paleontologists: https://t.co/EdzpvKw76q pic.twitter.com/7u1YpTyz0J — UT Jackson School of Geosciences (@txgeosciences) October 31, 2020
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Named After an Ancient Sword
Scarpetta brought the unusual sample back to the Jackson School of Geosciences at UT-Austin for further study. He later published his findings in the journal Scientific Reports, describing a new species designated as "Kopidosaurus perplexus."
The first part of the name is in reference to the lizard's distinctly curved teeth, resembling a "kopis" or a curved blade used in ancient Greece. "Perplexus" was chosen because of the perplexing issue of its location in the evolutionary timeline. His study claims that the evidence from the fossil maintains an "unclear phylogenetic position" of this new species.
"Lizards are small and prone to breaking apart, so you mostly get these individual, isolated fragmented bones," explained Scarpetta. He added that anytime a discovery is made, "it's always an exciting find."
The Phylogenetic Tree Problem
The possible positions of the new species can be traced into two distinct groups of lizards that correspond to the general hypothesis as to the position of the newly-discovered species. What makes placing this new lizard species in the evolutionary tree more perplexing is that these two potential groups closely relate to each other depending on which specific evolutionary tree researchers are examining.
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Scarpetta, in his study, analyzed three different phylogenetic trees generated from previous studies that covered evolutionary connections between different reptile groups related together through their respective genome sequences - ending up with a number of possibilities for the Kopidosaurus perplexus to fit in.
According to an article from UT-Austin, this case highlights a lesson for paleontologists - that just because a species could fit in one part of the tree does not mean it would not fit another point.
"The hypothesis that you have about how different lizards are related to each other is going to influence what you think this one is," Scarpetta added.
In understanding the evolutionary relationship of one animal to another, paleontologists like Scarpetta look for clues hidden in the preserved bones. For the Kopidosaurus perplexus, Scarpetta subjected its skull to a High Resolution X-Ray Computerized Tomography (CT) scanner to generate a digital scan and allow him to view it closer and observe its minute detail. While it provided clues for the study, some details appeared murky - overlapping with known features from different evolutionary groups - all groups belonging to a larger infraorder called Iguania.
In the same article from the University, Paleontologist Joshua Lively, also serving as the curator at the Utah State University Eastern Prehistoric Museum, agrees with Scarpetta recognition of the uncertainties in this discovery.
"Simon's [Scarpetta] approach is the high bar, taking the high road. It's acknowledging what we don't know and really embracing that," Lively said.
