Meet "Taytalura alcoberi," a creature that lived 200 million years ago.
Above: Artist's depiction of the Triassic scaly dragon "Taytalura alcoberi".
Twenty years ago, paleontologists found a 231.4 million-year-old fossil of Lepidoptera in Argentina and described it in detail. The animal's characteristics suggest that it existed before the differentiation of lizards, snakes, and wedge-toothed lizards (a branch of reptiles that now include only the strange large lizard). The fossil skull recently underwent a CT scan, and an interdisciplinary team of researchers published their analytical findings on the specimen this week in the journal Nature.
This animal is called "Taytalura alcoberi". To the average person, it looks a lot like a lizard (I think it's more like a rusty gecko). But the animal's anatomy is much older, something the team discovered while studying the fossils in detail. The team said the animal's body has not been preserved, but the skull (about 1 and a half inches long) is the most complete evolutionary fossil of Lepidoptera known. By looking at three-dimensional skulls, scientists provide new insights into how the skulls of modern snakes, chameleons, geckos, lizards and other animals are derived.
Ricardo Martínez, a paleontologist at the National University of San Juan in Argentina, who presided over the study, explains: "This almost well-preserved 'Taytalura alcoberi' skull perfectly shows the details of the origins of a very successful group of animals, which includes nearly 11,000 animals such as snakes, lizards and large lizards. ”
The skull of "Taytalura alcoberi" demonstrates functions that some scientists thought only cuneiform lizards had. The original "Taytalura alcoberi" looked more like a wedge-toothed lizard than a scaly animal (reptile). Thus, scaly animals represent a significant deviation from ancestral patterns. The scaly order is a reptile group consisting of snakes , lizards , and worm lizards.
"Taytalura alcoberi" was discovered in Argentina in 2001. Researchers call it a "stem species," a term that refers to animals that branched out of an evolutionary tree before a lineage that continues to this day. In other words, they are early evolutionary species and have no offspring that live to this day. "Taytalura alcoberi" is an evolutionary branch that indicates the state of life before lepidosaurs split into two groups: lepidates and cuneiformes. Although the animal is younger than some lizards — the earliest scaly and wedge fossils date back 242 million and 238 million years, respectively — its form is much older. The animal dates back to the Triassic, even 150 million years before T. rex.
Above: From left to right: skull fossils, CT scan reconstruction, and restoration of "Taytalura alcoberi".
Some of the features of "Taytalura alcoberi" are special. It lacks the opening and nose common to progenitosaurs, an evolutionary lineage that includes crocodiles and dinosaurs. Its square bone, which connects the skull and jaw, has a special shape. But CT scans do illustrate the problem: The animal's bones are incompatible with the bones of scaly and wedge-toothed orders.
The Great Lizard is a reptile endemic to New Zealand, and for about 60 million years it was the only cuneiformer on Earth to survive. Because of their always relatively unchanging anatomy, lizards are often referred to as "living fossils.". This fossil animal is closer to the large lizard than chameleons, footless lizards, and snakes, thus confirming this claim.
Scientists applied Bayesian analysis to place fossils of "Taytalura alcoberi" in an evolutionary tree. The model means that the research team can estimate when Lepidoptera develop specific adaptations and how quickly they change. The Bayesian method confirmed to the team that "Taytalura alcoberi" is the most primitive known member of the reptile lineage, from which all lizards and snakes are derived.
"In science, we never seek correct answers or proofs, because the basic premise of science prohibits the existence of correct answers," the scientists said. In principle, these evolutionary trees are never correct, and they often change over time. But if, after future analyses, and perhaps new data, the position of "Taytalura alcoberi" remains unchanged, which could cement our point in this paper as a new theory of the origin of lepidoptera. ”
Above: Phylogenetic tree of the lower order Lepidoptera.
This fossil is a big step toward understanding today's reptiles; in other words, the reptiles that didn't go extinct with the dinosaurs. In addition to crocodiles, many of these animals are smaller animals that have lived in the shadows of giants for millions of years.
Finally, scientists tell us: "We are accustomed to accepting that the Mesozoic era was the age of giant reptiles, huge primitive mammals, and huge trees. Therefore, we usually look for fossils that are highly visible in humans. However, as today, the largest component of ancient ecosystems tended to be small groups. In fact, there is a large group of animals sneaking among larger, clawed or hoofed animals. ”
It's always cool to see some newly discovered branches on the Tree of Life, but it's probably even cooler to see how the whole branch sprouts in the first place. "Taytalura alcoberi" is one such thing, a small remnant of a huge rift between reptiles.
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