Twenty years since it was found in Argentina, paleontologists have described in detail a fossil of a 231.4 million-year-old lepidosaur. This animal has characteristics that place it before the division between lizards, snakes and sphenodonts (a branch of reptiles that today only includes the strange tuatara). The fossilized skull has recently undergone computed tomography and an interdisciplinary team of researchers published his analysis of the specimen this week in Nature.
The animal is Taytalura alcoberi. To the untrained eye, it looks a lot like a lizard (a rusty gecko, for this writer). But the animal’s anatomy is much older, which the research team discovered when they were able to examine the fossil in detail. No body of the animal has been preserved, but the skull, which is about an inch and a half long, is the most complete fossil of the evolution of lepidosaurs known to date, said study co-author Gabriela Sobral, who supervised computed tomography at Harvard Press release. Seeing the skull in three dimensions provided new insights into how the skulls of today’s snakes, chameleons, geckos, tuatara, and more were derived.
“The almost perfectly preserved one Taytalura skull shows us details of how a very successful group of animals, which includes about 11,000 species originated, including snakes, lizards, and tuatars, “said Ricardo Martinez, lead author of the study and paleontologist at the National University of San Juan in Argentina.
“Taytalura shows some features that we believe were exclusive to the tuatara group, “Martinez wrote in an email to Gizmodo. Taytalura it shows that the first lepidosaurs resembled the tuataras more than the squamates and, therefore, that the squamates represent an important deviation from the ancestral pattern ”. Scales are the group of reptiles made up of snakes, lizards and worm lizards.
Discovered in Argentina in 2001 (“I just found it on the surface and picked it up,” Martinez said), T. alcoberi is what researchers call “stem species“A term for animals that branched from the evolutionary tree before the lineages that persist to this day. In other words, they are earlier evolving species that have no living offspring. T. alcoberi it is an evolutionary branch that indicates what life was like before lepidosaurs divided into two groups: the scaly and sphenodonts. But T. alcoberi it is younger than some lizards — the oldest scaling and sphenodont fossils date back 242 million and 238 million years, respectively — and its morphology is older. The reptile, which dates from the Triassic, precedes Tyrannosaurus Rex in more than 150 million years.
G / O Media may receive a commission
T. alcoberi it had some characteristics that indicated Tiago Simões, an evolutionary biologist at Harvard University and co-author of the work, who was special. It lacked a common snout opening in archosaurs, the evolutionary lineage that includes crocodilians and dinosaurs. Its square bone, which connects the skull to the lower jaw, had a peculiar shape. But the CT scan really brought things home: the animal had bones that were mutually exclusive to both scales and sphenodonts.
The tuatara, a reptile endemic to New Zealand, it has been the only living sphenodont on Earth for about 60 million years. Due to its relatively unaltered anatomy over the centuries, the tuatara is often called a “living fossil.” I T. alcoberi corroborates this label, with the fossil animal more like the tuatara than chameleons, legless lizards, and snakes.
Simões applied a Bayesian analysis to locate the fossil in the evolutionary tree. Modeling meant that the research team was able to estimate when specific adaptations were developed in lepidosaurs and how quickly they changed. The Bayesian method confirmed to the team that T. alcoberi it is the most primitive known member of the reptilian lineage from which all lizards and snakes arose.
“In science, we never look for true answers or evidence because the basic premises of science forbid the existence of true answers … in principle, these trees are never correct and often change over time. But if after future analysis, and perhaps new data, the location of Taytalura remains the same, you can consolidate our ideas in this article as a new theory about the origin of lepidosaurs, ”Simões said in an email to Gizmodo.
The fossil is a major step toward understanding modern reptiles; in other words, those who did not fall with the dinosaurs. With the exclusion of crocodiles, many of these animals were on the smaller side, living in the shadows of giants for millions of years.
“We are used to accepting that the Mesozoic era was an era of giant reptiles, huge protomammals and huge trees, and therefore we usually look for fossils that are visible at human height, just by walking. However, most of the components of the ancient ecosystem were small, as they are today. There was a universe of fauna that crept between the larger legs, with claws or stones, “said co-author Sebastián Apesteguía, a paleontologist at Maimónides University in Buenos Aires, in Press release.
It’s always cool to see some newly discovered twig in the tree of life, but maybe it’s even cooler to see clues about how whole branches sprouted to begin with. T. alcoberi is exactly that; a remnant the size of a pint of a large fracture between reptiles.
Correction: A phrase in this article erroneously referred to the tuatara as “lizard.” While tuatars certainly look like lizards, they are sphenodonts. We apologize to both readers and tuataras for this mistake.
More: This ancient reptile developed a strange, bird-like head 100 million years before birds did.