In 2017, whereas shopping the fossil collections of Yale’s Peabody Museum of Pure Historical past, College of Texas at Austin graduate scholar Simon Scarpetta got here throughout a small lizard cranium, just below an inch lengthy.
|A CT picture of the Kopidosaurus perplexus cranium in left lateral view
[Credit: Simon Scarpetta]
The cranium was superbly preserved, with a mouth filled with sharp tooth – together with some with a particular curve. A lot to Scarpetta’s shock, nobody had studied it. Since being found in 1971 on a museum fossil searching journey to Wyoming, the 52 million-year-old cranium had sat within the specimen drawer.
“Lizards are small and susceptible to breaking up, so that you largely get these particular person, remoted fragmented bones,” stated Scarpetta, who’s learning paleontology on the UT Jackson College of Geosciences. “Anytime you discover a cranium, particularly whenever you’re making an attempt to determine how issues are associated to one another, it is all the time an thrilling discover.”
Scarpetta determined to deliver the cranium again to the Jackson College for a more in-depth look. And on September 2020, the journal Scientific Stories printed a research authored by Scarpetta describing the lizard as a brand new species, which he named Kopidosaurus perplexus.
The primary a part of the title references the lizard’s distinct tooth; a “kopis” is a curved blade utilized in historic Greece. However the second half is a nod to the “perplexing” matter of simply the place the extinct lizard ought to be positioned on the tree of life. In keeping with an evaluation carried out by Scarpetta, the proof factors to various believable spots.
|Kopidosaurus perplexus cranium in left lateral view
[Credit: Simon Scarpetta]
The spots may be divided into two teams of lizards, representing two normal hypotheses of the place the brand new species belongs. However including to the uncertainty is that how these two teams relate to at least one one other can shift relying on the actual evolutionary tree that is examined. Scarpetta examined three of those timber – every one constructed by different researchers learning the evolutionary connections of various reptile teams utilizing DNA – and means that there may very well be a forest of prospects the place the traditional lizard might match.
The case of the place precisely to place the perplexing lizard highlights an necessary lesson for paleontologists: simply because a specimen suits in a single place does not imply that it will not match equally nicely into one other.
“The speculation that you’ve got about how totally different lizards are associated to one another goes to affect what you suppose this one is,” Scarpetta stated.
Paleontologists use anatomical particulars current in bones to discern the evolutionary relationships of long-dead animals. To get an in depth have a look at the lizard cranium, Scarpetta created a digital scan of it within the Jackson College’s Excessive-Decision X-Ray CT Lab. Nevertheless, whereas sure particulars helped establish the lizard as a brand new species, different particulars overlapped with options from various totally different evolutionary teams.
|Molecular scaffolds used within the research with labelled primary sister relationship hypotheses
for Kopidosaurus [Credit: Simon Scarpetta]
All of those teams belonged to a bigger class often known as Iguania, which incorporates various numerous species, together with chameleons, anoles and iguanas. To get a greater concept of the place the brand new species may match into the bigger Iguania tree, Scarpetta in contrast the cranium knowledge to evolutionary timber for Iguania that have been compiled by different researchers based mostly on DNA proof from dwelling reptiles.
On every tree, the fossil match equally nicely into two normal spots. What’s extra, the lizard groupings in every spot diversified from tree to tree. If Scarpetta had simply stopped at one spot or one tree, he would have missed different explanations that seem simply as believable because the others.
Scarpetta stated that Kopidosaurus perplexus is way from the one fossil that would simply match onto a number of branches on the tree of life. Paleontologist Joshua Energetic, a curator on the Utah State College Japanese Prehistoric Museum, agrees and stated that this research epitomizes why embracing uncertainty can result in higher, extra correct science.
“One thing that I feel the broader scientific group ought to pull from that is that you must be sensible about your knowledge and acknowledge what we are able to really pull from our outcomes and conclude and the place there are nonetheless uncertainties,” Energetic stated. “Simon’s method is the excessive bar, taking the excessive highway. It is acknowledging what we do not know and actually embracing that.”
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