Scientists have discovered the world’s first fossil evidence of live birth in snakes at the Messel Pit, a UNESCO World Heritage Site
In the study published in The Science of Nature, researchers identify the bones of snake embryos discovered in the mother’s body. The finding suggests that snakes giving live birth already existed at least 47 million years ago.
Most reptiles living today lay eggs; this is their most common form of reproduction. But there are exceptions: Numerous species of lizards and snakes are known to deviate from the norm and give live birth to their young.
Dr. Krister Smith of the Senckenberg Research Institute and the Frankfurt Museum of Natural History said, “Fossil preservation of reproductive events is generally very rare. In total, only two fossils of land reptiles giving live birth have been discovered to date. Now we have managed to identify the world’s first fossil evidence of a snake giving live birth.”
The Messelophis variatus fossil, from a family of boa-like snakes, is about 50 centimeters long, from the Eocene epoch, and is related to modern dwarf boas from Central America.
Dr. Mariana Chuliver, lead author of the study from the Fundación de Historia Natural in Buenos Aires, said, “The species is among the most common snakes known from Messel. However, we were surprised by this specimen, which is about 47 million years old: A pregnant female with at least two embryos in the posterior third of the trunk region.”
“When examining the fossil, we realized that some of the skull bones present belonged to small boas, no more than 20 centimeters in length. These bones were located well behind the stomach – if they were part of the snake’s prey, they would have been digested all the way to the intestine and would no longer be recognizable. Therefore, they must represent the embryos of the boa. The fact that the bones belong to very young snakes, but are more developed than an unhatched egg, supports the hypothesis that we are dealing with a pregnant, live-bearing female.”
In live births, the young remain in the female’s body until they are viable – eliminating the need for a protective eggshell. This is considered an advantageous evolutionary strategy for reptiles in cold climates, as the temperature inside the female’s body is more stable and therefore safer for her offspring. This is why most of today’s live-bearing lizards and snakes evolved in fairly cold climates.
“However, during the Eocene, the Earth was dominated by a persistent greenhouse climate with warm temperatures, a high carbon dioxide content in the atmosphere and ice-free poles,” Smith said. Around Lake Messel, average temperatures at the time were about 20 degrees Celsius, and winter temperatures did not drop below freezing. Despite this fact, it is still unknown why boas gave birth to live young 47 million years ago. Perhaps additional fossils from this unique site will help us solve this mystery.”
Senckenberg Research Institute and Natural History Museum. November 15, 2022.
Article: Chuliver, M., Scanferla, A. & Smith, K.T. (2022). Live birth in a 47-million-year-old snake. Sci Nat 109, 56.