An creative interpretation of a newly found extinct species of lizard-like reptile belonging to the identical historic lineage as New Zealand’s residing tuatara. The newly found Opisthiamimus gregori preys on a now-extinct water bug (Morrisonnepa jurassica), whereas within the background the predatory dinosaur Allosaurus jimmadseni guards its nest. The scene is the floodplain of a river in Late Jurassic Wyoming, roughly 150 million years in the past. A group of scientists describes the brand new species, which as soon as inhabited Jurassic North America about 150 million years in the past alongside dinosaurs like Stegosaurus and Allosaurus, in a paper printed in the present day within the Journal of Systematic Palaeontology. In life, this prehistoric reptile would have been about 16 centimeters (about 6 inches) from nostril to tail and would match curled up within the palm of an grownup human hand. The discovery comes from a handful of specimens together with an awfully full and well-preserved fossil skeleton excavated from a website centered round an Allosaurus nest in northern Wyoming’s Morrison Formation. Credit: Julius Csotonyi for the Smithsonian Institution
Discovery sheds mild on the tuatara, the final residing member of a once-diverse group of reptiles that has nearly completely been supplanted by lizards.
A brand new extinct species of lizard-like reptile that belongs to the identical historic lineage as New Zealand’s residing tuatara has been found by Smithsonian researchers. The new species Opisthiamimus gregori, which as soon as inhabited Jurassic North America about 150 million years ago alongside dinosaurs like Stegosaurus and Allosaurus, is described in a paper published on September 15, 2022, in the Journal of Systematic Palaeontology. In life, this prehistoric reptile would have been about 16 centimeters (about 6 inches) from nose to tail—and would fit curled up in the palm of an adult human hand. It likely survived on a diet of insects and other invertebrates.
A team of scientists, including the National Museum of Natural History’s curator of Dinosauria Matthew Carrano and research associate David DeMar Jr. as well as University College London and Natural History Museum, London scientific associate Marc Jones, contributed to the research.
“What’s important about the tuatara is that it represents this enormous evolutionary story that we are lucky enough to catch in what is likely its closing act,” Carrano said. “Even though it looks like a relatively simple lizard, it embodies an entire evolutionary epic going back more than 200 million years.”
Fossil skeleton of the new lizard-like reptile Opisthiamimus gregori. The fossil was discovered in the Morrison Formation of the Bighorn Basin, north-central Wyoming, and dates to the Late Jurassic Period, approximately 150 million years ago. Researchers named the new species after Smithsonian’s National Museum of Natural History volunteer Joseph Gregor who spent hundreds of hours meticulously scraping and chiseling the bones from a block of stone that first caught museum fossil preparator Pete Kroehler’s eye back in 2010. The fossil has been added to the museum’s collections where it will remain available for future study. A team of scientists describes the new species, which once lived alongside dinosaurs like Stegosaurus and Allosaurus, in a paper published today in the Journal of Systematic Palaeontology. In life, this prehistoric reptile would have been about 16 centimeters (about 6 inches) from nose to tail—and would fit curled up in the palm of an adult human hand—and likely survived on a diet of insects and other invertebrates. Credit: David DeMar for the Smithsonian Institution
The discovery comes from a handful of specimens, one of which was an incredibly complete and well-preserved fossil skeleton excavated from a site centered around an Allosaurus nest in northern Wyoming’s Morrison Formation. Further investigation of the find could help reveal why this animal’s ancient order of reptiles was winnowed down from being diverse and numerous in the Jurassic to only New Zealand’s tuatara surviving today.
Although the tuatara looks a bit like a particularly stout iguana, the tuatara and its newly discovered relative are in fact not lizards at all. They are actually rhynchocephalians, an order that diverged from lizards at least 230 million years ago, Carrano said.
The analysis group set about scanning the fossil with high-resolution computed tomography (CT), a technique that makes use of a number of X-ray pictures from completely different angles to create a 3D illustration of the specimen. The group used three separate CT scanning services, together with one housed on the Smithsonian’s National Museum of Natural History, to seize the whole lot they probably may in regards to the fossil. Once the fossil’s bones had been digitally rendered, the group set about reassembling the digitized bones of the cranium, a few of which have been crushed, misplaced, or lacking on one aspect, utilizing software program to finally create a virtually full lifelike 3D reconstruction. A group of scientists describes the brand new species Opisthiamimus gregori, which as soon as lived alongside dinosaurs like Stegosaurus and Allosaurus, in a paper printed in the present day within the Journal of Systematic Palaeontology. In life, this prehistoric reptile would have been about 16 centimeters (about 6 inches) from nostril to tail—and would match curled up within the palm of an grownup human hand—and sure survived on a weight loss program of bugs and different invertebrates. Credit: D. DeMar
In their heyday in the course of the Jurassic interval, rhynchocephalians have been discovered practically worldwide and got here in sizes giant and small. They crammed ecological roles starting from aquatic fish hunters to cumbersome plant munchers. But for causes which can be nonetheless not totally understood, rhynchocephalians all however disappeared as lizards and snakes grew to be the extra frequent and extra numerous reptiles throughout the globe.
This evolutionary chasm between lizards and rhynchocephalians helps clarify the tuatara’s unusual options. These embody a 100-year-plus lifespan, enamel fused to the jaw bone, a singular chewing movement that slides the decrease jaw forwards and backwards like a noticed blade, and a tolerance for colder climates.
3D reconstruction of the cranium of Opisthiamimus gregori, a brand new extinct species of lizard-like reptile from the Late Jurassic of Wyoming, U.S. Individual bones are color-coded. Credit: D. DeMar
Following O. gregori’s formal description, Carrano stated the fossil has been added to the museum’s collections the place it’s going to stay obtainable for future research. Perhaps sooner or later it’s going to assist scientists determine why the tuatara is all that is still of the rhynchocephalians, whereas lizards at the moment are discovered throughout the globe.
“These animals may have disappeared partly because of competition from lizards but perhaps also due to global shifts in climate and changing habitats,” Carrano stated. “It’s fascinating when you have the dominance of one group giving way to another group over evolutionary time, and we still need more evidence to explain exactly what happened, but fossils like this one are how we will put it together.”
The new species is called after Joseph Gregor, a museum volunteer who spent a whole lot of hours painstakingly scraping and chiseling the bones from a block of stone that drew the eye of Pete Kroehler, a museum fossil preparator, again in 2010.
“Pete is one of those people who has a kind of X-ray vision for this sort of thing,” Carrano stated. “He noticed two tiny specks of bone on the side of this block and marked it to be brought back with no real idea what was in it. As it turns out, he hit the jackpot.”
Photo (high) and interpretive drawing (backside) of the cranium and skeleton of Opisthiamimus gregori, a brand new extinct species of lizard-like reptile from the Late Jurassic of Wyoming, U.S. Credit: D. DeMar (picture, high), James Morrison (illustration, backside).
The fossil is nearly completely full, apart from the tail and elements of the hind legs. Such an entire skeleton is uncommon for small prehistoric creatures like this, Carrano stated, as a result of their frail bones have been typically destroyed both earlier than they fossilized or as they emerge from an eroding rock formation within the current day. As a end result, rhynchocephalians are largely recognized to paleontologists from small fragments of their jaws and enamel.
After Kroehler, Gregor and others had freed as a lot of the tiny fossil from the rock as was sensible given its fragility, the group, led by DeMar, set about scanning the fossil with high-resolution computerized tomography (CT). This is a technique that makes use of a number of X-ray pictures from completely different angles to create a 3D illustration of the specimen. The analysis group used three separate CT scanning services, together with one housed on the National Museum of Natural History, to seize the whole lot in regards to the fossil they probably may.
Once the fossil’s bones had been digitally rendered with an accuracy smaller than a millimeter, DeMar set about reassembling the digitized bones of the skull. Some of them were crushed, out of place, or missing on one side, so software was used to eventually create a nearly complete 3D reconstruction. This reconstructed 3D skull now provides scientists with an unprecedented look at this Jurassic-age reptile’s head.
Given Opisthiamimus’s diminutive size, tooth shape, and rigid skull, it likely ate insects, said DeMar, adding that prey with harder shells such as beetles or water bugs might have also been on the menu. Broadly speaking, the new species looks quite a bit like a miniaturized version of its only surviving relative (tuataras are about five times longer).
“Such a complete specimen has huge potential for making comparisons with fossils collected in the future and for identifying or reclassifying specimens already sitting in a museum drawer somewhere,” DeMar said. “With the 3D models we have, at some point, we could also do studies that use software to look at this critter’s jaw mechanics.”
Reference: “A nearly complete skeleton of a new eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the evolution and diversity of Rhynchocephalia (Reptilia: Lepidosauria)” 15 September 2022, Journal of Systematic Palaeontology.
DOI: 10.1080/14772019.2022.2093139
Funding and support for this research were provided by the Smithsonian and the Australian Research Council.
