His suspicion was right. Analysis of the scans after the project got going last summer showed the fossil belonged to a previously unknown species of lizard-like reptile, representing the earliest evolving member of a lineage that today includes all lizards, snakes, and their closest relatives. That’s nearly 11,000 species altogether.
Unearthed in the moonlike desert landscape of Ischigualasto Provincial Park in northwest Argentina, the fossil is of a lepidosaur, one of the major evolutionary branches of reptiles. It is the first three-dimensionally intact skull of a primitive member of this lineage ever found, and its discovery can help researchers better understand the early evolutionary history of this vast group.
“We have very few fossils from 240 or 250 million years ago, when this entire group is expected to have originated, and the very few fossils that we have are extremely fragmented. You have only pieces of jaws and teeth here and there,” said Simões, who is a fellow at Harvard and funded by the National Sciences and Engineering Research Council of Canada. “The first thing that this provides is this missing piece of the puzzle, which is an amazingly well-preserved skull of a primitive member of this lineage that lived in Argentina.”
Results of his analysis were published Wednesday in the journal Nature. The study was a collaboration between Simões and scientists from Argentina and Germany.
Understanding the significance of this find requires a little background. There are two main branches of reptile: archosaurs and lepidosaurs. Archosaurs include all crocodile and dinosaur lineages, while lepidosaurs include squamates (lizards, snakes) and sphenodontians, which have only one living species today, the tuatara of New Zealand.