Saturday, 5 November 2016

Tetrapodophis amplectus: Four-Legged Snake Was a Marine Lizard, New Research Suggests

Image courtesy of Dave Jones, Creative commons (CC BY-NC 4.0).

Joel Kontinen

Interpreting and dating fossils is an intriguing game. In 1990 J. Shreeve wrote in Discover magazine: ”Everybody knows fossils are fickle; bones will sing any song you want to hear.

This, of course, pertains to hominins, i.e. us and our assumed more or less ape-like ancestors, as well as to all fossils.

In 2015, David Martill at the University of Portsmouth, UK, and colleagues published a paper in Science on an assumed transitional form.

The four-footed snake Tetrapodophis amplectus was found by a private collector in Brazil and brought to Germany. It was tiny: its skull measured a centimetre and its overall length was 20 centimetres (8 inches).

Assumed to be 108 million years old, it had four little legs and looked liked the transitional form evolutionists were hoping to find.

Last week, at a meeting of the Society of Vertebrate Paleontology (SVP) another research team came up with a very different kind of interpretation of the fossil. They proposed that it was a marine lizard.

An article in Science states:

Vertebrate paleontologist Michael Caldwell of the University of Alberta in Edmonton, Canada, and colleagues presented their own observations of the specimen, rebutting Martill’s paper point by point to a standing-room-only crowd.

It seems that the 2015 paper had overlooked some very pertinent details:

The new analysis hinges on the ‘counterpart’ to the original fossil, which was also housed in the Bürgermeister-Müller Museum in Solnhofen, Germany. When the slab of rock containing the fossil was cracked open, the body of the organism stayed mostly in one half of the slab, whereas the skull was mostly in the other half, paired with a mold or impression of the body. This counterpart slab, Caldwell says, preserved clearer details of the skull in particular. In his group’s analysis of the counterpart, he says, ‘every single character that was identified in the original manuscript as being diagnostic of a snake was either not the case or not observable.’ ”

Caldwell and colleagues made a convincing case that Tetrapodophis was not a snake at all:

For example, in snake skulls, a bone called the quadrate is elongated, which allows snakes to open their jaws very wide. This fossil’s quadrate bone is more C-shaped, and it surrounds the animal’s hearing apparatus—a ‘characteristic feature’ of a group of lizards called squamates, says co-author Robert Reisz, a vertebrate paleontologist at the University of Toronto in Mississauga, Canada. He and Caldwell add that although the fossil has more vertebrae in its body than in its tail, the tail isn’t short, but longer than that of many living lizards. They are working on a paper arguing that the fossil is probably a dolichosaur, an extinct genus of marine lizard.”

This is not the first time a supposed transitional form turns out to not conform to Darwinian expectations.

Recent years have witnessed increasing doubts about Ardi or Ardipithecus ramidus, Australopithecus sediba, H. naledi and Nutcracker Man or Paranthropus boisei.

And we also had an infamous episode featuring Ida or Darwinius massillae.


Gramling, Carolyn. 2016. Controversial ‘four-legged snake’ may be ancient lizard instead. Science (1 November).