Fossil of Brazilian burrowing snake reveals evolutionary pathways among reptiles
The Tametara mirim fossil, found in São Paulo, Brazil, indicates that primitive ground- and surface-dwelling snakes coexisted over 75 million years ago
Reconstruction of the Tametara mirim snake as it appeared in life, alongside dinosaurs and the bird Navaornis, from the Adamantina Formation in present-day state of São Paulo – Image: Gabriel Ugueto
Tametara mirim lived during the Late Cretaceous period, between 85 and 75 million years ago, in what is now the state of São Paulo. It was found in the Adamantina Formation of the Bauru Group in the heart of Presidente Prudente at the José Martin Suárez Paleontological Site, where some of Brazil’s best-preserved birds have been unearthed. “This is one of the oldest and best-preserved snakes known. It is also the first articulated snake fossil found in Brazil”, said Annie Hsiou, a biology professor at the Faculty of Philosophy, Sciences and Languages at Ribeirão Preto (FFCLRP) to Jornal da USP. “The specimen preserves part of the skull and more than 100 articulated vertebrae, allowing for an extremely detailed reconstruction of its anatomy. This reconstruction was carried out using computed microtomography at the School of Engineering (Poli) of USP.”
The newly described species was named Tametara mirim, meaning “small ornament”, in reference to the sagittal crest, a prominence along the midline of the skull. “This species has characteristics that help us understand the origin and evolution of snakes. It is considered a primitive snake from the Brazilian Cretaceous period”, the researcher emphasized.
Annie Hsiou noted that the species’ main characteristics include being small, with a preserved body length of about 42 centimeters and an estimated skull length of 3.3 cm. “The skull is highly specialized with primitive and unique characteristics such as a well-developed sagittal crest, strongly overlapping bones, and distinctive features in the occipital and mandibular regions”, she reported. “The absence of forelimbs is also notable, indicating that limb reduction had already occurred at this stage of snake evolution. The hind limbs could not be assessed, as the cloacal region was not preserved.”
“The brain was preserved indirectly, allowing us to reconstruct its shape and that of the inner ears, something unprecedented for such an ancient snake. Its lifestyle was fossorial; that is, it was a burrower. This conclusion is supported by various lines of evidence, such as brain shape, inner ear structure, and microstructure of the skull bones. These are combined with statistical analyses comparing its anatomy to that of modern snakes”, explained the paleontologist from USP’s Laboratory of Integrated Paleobiodiversity (LAPI).
In the video Tametara – The Queen of Snakes, the researchers describe the main characteristics of the newly identified species and feature images of the fossil and three-dimensional reconstructions of the skull and brain – Video: Simone Macri
Snake diversity
According to Annie Hsiou, Tametara mirim, despite being a primitive snake, shares several characteristics with modern snakes. “These include an elongated body composed of numerous vertebrae; an absence of forelimbs; vertebral joints typical of snakes, such as zygosphen and zyganth, which increase spinal stability; and a general brain organization similar to modern snakes”, she explained. “It also has adaptations for burrowing similar to those of modern burrowing snakes, such as Caecilians and snakes with cylindrical bodies, like the Amazon false coral snake (Anilius scytale).”
“Although Tametara mirim possesses characteristics typical of snakes, it also exhibits several differences compared to modern species. The skull bones (occipital bones) remain separate in Tametara mirim, whereas in modern snakes they are typically fused. It also has a highly developed sagittal crest, which is uncommon among living snakes”, she noted. “The brain exhibits a unique combination of regions, differing from both known fossil snakes and modern species. The inner ear is highly specialized for burrowing, with simplified semicircular canals and an enlarged vestibular region. Its anatomy indicates a specialization for burrowing that is even more extreme than that observed in many modern burrowing snakes.”
The study demonstrates that Tametara mirim is one of the earliest snakes in evolutionary history. It also reveals that there was great ecological diversity among primitive snakes as early as the Cretaceous period. “While Tametara was highly adapted to subterranean life, other fossil snakes from the same period, such as Dinilysia, had terrestrial, surface-dwelling habits. Still others were marine”, noted the researcher. “Thus, the early evolution of snakes did not follow a single ecological path but involved multiple adaptations to different environments very early in their evolutionary history.”
“We have revitalized the long-standing debate about the ecological factors that led to the emergence of snakes. We have demonstrated that it is possible to infer ancestral ecologies from the morphology preserved in fossils. Our findings show that snakes had already achieved remarkable ecological and neuroanatomical diversity by the Late Cretaceous period, approximately 80 million years ago”, said Tiago Simões, the study’s lead author and a professor in the Department of Ecology and Evolutionary Biology at Princeton University in the United States. “The ancestral condition of all snakes was not one of strong adaptation to a single habitat. Rather, it was a transitional condition situated at the interface between burrowing and surface environments.”
“A large research team in Brazil and abroad participated in all stages of the study”, said Annie Hsiou, a biology professor at FFCLRP and paleontologist at USP’s Laboratory of Integrated Paleobiodiversity (LAPI). She was part of the team responsible for studying the material. The group was led by paleontologist Tiago Simões of Princeton University in the United States and included Gabriela Sobral of the University of Brasília (UnB) and the Staatliches Museum für Naturkunde in Stuttgart, Germany; Thiago Schneider Fachini of USP’s Paleontology Laboratory of Ribeirão Preto (LPRP); William Nava, a staff member at the Marília Paleontology Museum who collected the specimen; and Giovanna Paixão, a doctoral student at the Federal University of Pampa (Unipampa) who assisted with collecting and preparing the fossil. The microCT scan was performed at the Technological Characterization Laboratory (LCT) of the Department of Mining and Petroleum Engineering at Poli.
This international collaboration also included the following evolutionary biologists: Simone Macrì and Nicolas Di-Poï from the University of Helsinki in Finland, Roy Ebel from the Australian National University and Museums Victoria in Australia, and the Argentine paleontologists Agustín Martinelli from the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” and Luis Chiappe from the Natural History Museum of Los Angeles County in the United States. These biologists contributed to the collection, analysis, and study of the new snake fossil from Brazil. The article Exceptional brain and ecological diversity in the earliest snakes, published in Nature, can be accessed at this link.
For more information: e-mail anniehsiou@usp.br, with Annie Hsiou
English version: Nexus Traduções, edited by Denis Pacheco
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