Boas and pythons lived side-by-side in the ancient world

The oldest known python fossils, recently discovered in Germany, challenge current theories about early snake evolution.

The fossils were discovered in the Messel Pit in Germany, where ancient boa fossils were previously found. Boas are an anatomically similar but genetically distinct constrictor snake species.

The importance of the find is that it shows for the first time that pythons and boas lived together in the same environment. Current snake evolutionary theory holds that pythons and boas are distantly related and found in completely different geographical locations because the breakup of the supercontinent Gondwana. This event would have separated the population accounting for genetic divergence and appearance of these species in separate parts of the world. However, this new find unravels that model.

The Messel pit is a UNESCO World Heritage Site that dates from the Eocene epoch, 56 to 34 million years ago.

The new species is named Messelophython freyi after its discovery at the Messel pit and in honor of fossil reptile expert Dr. Eberhard Frey of the State Museum of Natural History in Karlsruhe, Germany.

The finding and its importance are described in the Royal Society journal Biological Letters, Dec. 16, 2020, by Hussam Zaher and Krister T. Smith.

“The geographic origin of pythons is still not clear. The discovery of a new python species in the Messel Pit is therefore a major leap forward in understanding these snakes’ evolutionary history,” co-author Smith said in a news release on the discovery by the Senckenberg Research Institute and Natural History Museum in Frankfurt.

Today pythons and boas live in completely separate locations (allopatry). But Zaher and Smith conclude: "Remarkably our results suggest that boids and pythonids coexisted in Europe during the early-middle Eocene...implying that their modern allopatry cannot be attributed solely" to separation by physical barriers. 

This barrier explanation refers to the breakup of the supercontinent Gondwana approximately 180 million years ago, which is thought to be the reason that pythons and boas are not currently found together.

The authors suggest that the python family probably originated in the more northern supercontinent of Laurasia, not Gondwana, as is commonly thought. From the European part of Laurasia, pythons dispersed to Africa, Southeast Asia and Oceana.

The authors note that their discovery was "wholly unexpected," and they suggest that future fossil discoveries in the Arctic and North American region may test the strength of their conclusion about snake evolution. 

The open question is why boas and pythons lived together in the past as unique species but are found in complete allopatry today.