New research published in the journal Nature Ecology & Evolution, reveals important clues about the evolutionary history of snakes. Led by an international team of researchers from the University of Alberta, Canada; Natural History Museum, UK; and Flinders University, Australia, the study focuses on two exquisitely preserved 95-million-year-old snake fossils from Myanmar, which provide important insights into the early stages of snake evolution.
The fossils — which belong to two new snake species named Xiaophis myanmarensis and Microraptor zhaoianus — showcase a mosaic of primitive and advanced features that shed light on the evolutionary transformation from lizards to snakes. One of the most striking features of the fossils is their relatively robust hind limbs and well-developed feet. This suggests that while the loss of limbs was underway in early snakes, these animals still possessed functional legs, hinting at a transitional phase when snakes were transitioning from lizard-like ancestors.
Additionally, the researchers were able to identify preserved muscle fibers within the hind limbs, providing direct evidence of the musculature associated with limb movement. This finding not only supports the presence of functional limbs in early snakes but also contributes to our understanding of how these ancient animals moved and interacted with their environment.
Another significant aspect of the fossils is the presence of small, but fully formed teeth on the roof of the mouth, known as maxillary teeth or soleno-glyphs. These teeth are a key characteristic of modern venomous snakes, although they are typically much longer and canalized, acting as venom delivery devices. The presence of maxillary teeth in these ancient snakes suggests that venom delivery systems were already present in early snakes, much earlier than previously thought, and provides evidence for an alternative, suction-based venom delivery system.
By integrating these findings with molecular dating techniques, the research team refined the timeline of early snake evolution, suggesting that snakes originated during the Cretaceous Period, around 150 million years ago.
Dr. Alex Pyron, Professor of Biology at the University of Alberta and one of the study's lead authors, highlights the significance of these findings:
"These new fossils provide a much clearer picture of the early evolution of snakes. They show that snakes were losing their legs but still had functional limbs, and they had teeth that were used to inject venom, just like modern snakes, but in a very different way. These findings challenge our understanding of how snakes evolved and diversified."
The remarkable preservation and completeness of the Xiaophis and Microraptor fossils contribute significantly to our understanding of the early history and diversification of snakes, providing key evidence for the transitional stages between lizards and modern snakes. This research expands our knowledge of the evolution of this fascinating group of vertebrates and adds to the growing body of evidence that sheds light on the diversity of life during Earth's distant past.
