Maxim Russo: Disputes about the four -legged snake

Maxim Russo H. Tischinge

At the Paleontology of the vertebrates passing in the Salt Lake Conference, the debate of scientists broke out around the “four-legged snake” discovered in 2015. A special emotional intensity was given to them by the fact that the only well -known copy of this species is now unavailable for study.

Recall that last year in the journal Science published an article by scientists from Great Britain and Germany who described the copy of the snake of the early Cretaceous period, which had four legs , albeit small, but quite functional, with five fingers on each. Scientists have called the Tetrapodophis amplectus to the animal. It lived on Earth about 120 million years ago. Its length is 20 centimeters, it had 160 dorsal and 112 tail vertebrae.

The history of the sample is quite mysterious. The first author of the article David Martill (David Martill) noticed him by visiting the Museum of Burghermeister-Muller (BürgerMeister-Müller Museum) with his students in the German city of Zolnhofen, famous for numerous finds in local limestone. It is known that earlier the sample was in a private collection. The place of its initial detection is unknown. It was probably mined in the formation of Krato in the northeast of Brazil.

The authors of the article suggested that their find indicates the ground ancestors of the future snakes of Gondwana, as opposed to the existing hypothesis, that the ancestors of the snakes were sea species. Of all the representatives of the scaly detachment ( Squamata ), including both lizards and snakes, only snakes have more than 150 vertebrae, therefore, the number of vertebrae of the new species indicates its proximity to snakes. In favor of the kinship of Tetrapodophis amplectus with snakes, the presence of scales on the abdomen and the shape of the teeth also speak. The small and thin limbs of the animal, according to scientists, could play an auxiliary role in the seizure of prey, which TetraPodophis amplectus wrapped his flexible body. They could also be used during mating.

But immediately after the publication, David Martill and his colleagues had opponents. Nobody doubted the animal’s legs, since the limbs are clearly visible in the published pictures. However, many researchers considered that the animal did not belong to the snakes, but to one of the groups of lizards. For example, Michael Caldwell, a paleontology specialist from the Alberta University, pointed out a number of anatomical differences in Tetrapodophis Ampletus from snakes. In particular, the front surfaces of the vertebrae of snakes and lizards, with the exception of geckons, are concaved, and the rear convex. As far as you can judge from the published photographs, Tetrapodophis amplectus was not so. He also does not have an intercenter (intercentrum), one of the fused bones that form each vertebra.

Now Koldwell and his colleagues presented their analysis of Tetrapodophis amplectus . It was made according to the “cast” of the sample - a fragment of the rock, in which fossils were printed. The cast is also stored in the museum of the city of Zolnhofen. According to Koldwell, he allowed to make out the smaller details of the skull than the fossil itself. And these details again convinced the scientist that Tetrapodophis amplectus was not a snake. For example, the snakes have a square bone of the skull, which allows them to open their mouth very widely. In the found species, square bones have a S-shaped shape, enveloping the animal hearing apparatus. Koldwell and its co -author Robert Reisz from the Toront University are inclined to the opinion that the fossil belongs to the dolichosaurs - an extinct group of lizards. This is also indicated by a larger number of spinal vertebrae compared to the tails.

Many researchers who were present during the report share doubt about belonging to Tetrapodophis amplectus to snakes. However, they are in no hurry to join the codell and flight. Most believe that for conclusions it is necessary to wait for a detailed publication of a petrified find. David Martill and his colleague Nicholas Longrich (Nicholas Longrich (Nicholas Longrich) from the University of Bata have their original opinion and emphasize the signs that unite the animal with snakes.

As for a more detailed study of the sample, difficulties arose with this. David Martill again went to the museum of the burghermaster - Muller to study the petrified reptile, the Paleontologist from the University of Cambridge Jason Head turned there. But neither one nor the other saw Tetrapodophis Amplectu S. The sample did not belong to the museum, but was rented from a private collector, and the owner for some reason banned the access of researchers. Perhaps he is afraid that in the course of research the sample will be damaged.

“If something good can get out of the story with Tetrapodophi S , it is a recognition that we must support scientific standards when it comes to fossils-they should be available,” said Jason Head. Many paleontologists believe that Martill was supposed to postpone with the publication of his article, since the sample on which it was based was not officially deposited in the museum or other storage, and therefore the author could not guarantee access to it of other researchers. Their opinion is expressed by Jacques Gauthier, a paleontologist from Yale University: “I am not against the private collecting of fossils. But when the fossil is included in scientific literature, it should be available. Science requires reproducibility. If the fossil cannot be studied, it does not exist for me. I do not want to mention the name Tetrapodophi S ever. " Reproaches are also distributed to Science magazine, which adopted the article. In response, the Deputy Chief Editor Andrew Sugden says that the editors, based on the text of the article and correspondence with the authors, believed that the sample is in the museum and is available for research.

In connection with the ill -fated tetradopis, other problems arise. Since he was obtained, apparently, Brazil in the second half of the 20th century, it is subject to Brazilian laws adopted in the 1940s, according to which paleontological finds are the property of the state. Consequently, fossil was taken out of the country and sold to the collector illegally.

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