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The highest species richness and ecological diversity of extant snakes are in the tropics, primarily in South Asia and Central and South America. Tropical Africa has relatively lower richness and less diversity, but the evolution of tropical herpetofaunas, and the factors governing diversification through time at continental scales are poorly understood due to an understudied fossil record. The ecologies and geographic distributions of aniliid and uropeltoid snakes are examples. Modern species constitute either a grade or clade of fossorial, primarily wet forest taxa from South America and South Asia. Their distributions have historically been interpreted as Gondwanan vicariance following the isolation of Africa in the Early Cretaceous, but a definitive fossil record for these snakes is depauperate. Field research in the early Miocene (approx. 19 Mya) Tinderet sequence of western Kenya has produced precloacal vertebrae of an aniliid snake from multiple localities. Specimens possess vertebral apomorphies shared with extant South American Anilius scytale, including the morphology of the neural spine and prezygapophyseal angle. Combined with additional fossils from the Eocene of North Africa and Middle Miocene of Kenya, the Tinderet records demonstrate an unambiguous past record of an extant neotropical snake lineage in Africa and falsify previous vicariance hypotheses. Recent stable isotopic and palynological studies of Neogene eastern African fossil localities have indicated heterogenous environments, including C4 grasses and wood- to scrubland, associated with vertebrate faunas. Comparing climate parameters of habitats for extant Anilius and uropeltoid snakes as ecological analogues to the Tinderet snake with modern ecosystems equivalent to those reconstructed for the eastern African early Miocene demonstrates only limited overlap in precipitation and temperature values. This discord indicates either greater environmental heterogeneity than reconstructed for the early Miocene of eastern Africa, or a greater range of habitat variability in aniliid snakes than observed in extant Anilius.
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This content will become publicly available on July 16, 2025
SQUAMATE REPTILES FROM THE EARLY MIOCENE OF EQUATORIAL AFRICA INDICATE COMPLEX DISPERSAL BIOGEOGRAPHIC HISTORIES AND WET-FOREST PALEOENVIRONMENTS
The highest species richness and ecological diversity of extant squamates are in the tropics. Both their taxic richness and functional traits are predictably correlated to environmental factors, and the utility of these measures in the squamate fossil record is an emergent tool for paleoenvironmental reconstruction. Ongoing field research in the early Miocene (approx. 20–19 Mya) Tinderet sequence of western Kenya has produced a diverse record of squamates which provides environmental data for hominoid-bearing localities. The record consists of chamaeleonid, agamid, varanid, and amphisbaenid lizards as well as snake lineages including pythonids, colubroids, elapoids, and a newly discovered taxon sharing unique vertebral apomorphies with extant tropical South American Anilius scytale. Combined with additional fossils from the Eocene of North Africa, the new Tinderet taxon demonstrates an unambiguous past record of an extant neotropical snake lineage in Africa and falsifies previous vicariance hypotheses to explain the biogeographic histories of basal divisions within snakes. Recent stable isotopic and phytolith studies of Early to Middle Miocene eastern African fossil localities have indicated heterogenous environments, including C4 grasses and wood- to scrubland, associated with vertebrate faunas. The composition of squamate faunas is generally consistent with these reconstructions, with the new taxon providing precise evidence for precipitation. Comparing climate parameters of habitats for Anilius and other extant ecological analogues equivalent to those reconstructed for the eastern African Early Miocene indicates annual precipitation between 1500–2500 mm/year, consistent with wet tropical seasonal forests and rain forests.
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- Award ID(s):
- 2123497
- PAR ID:
- 10557285
- Publisher / Repository:
- University of Michigan Papers on Paleontology
- Date Published:
- Format(s):
- Medium: X
- Location:
- Ann Arbor, Michigan, USA
- Sponsoring Org:
- National Science Foundation
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The highest species richness and ecological diversity of extant snakes are in the tropics, primarily in South Asia and Central and South America. Tropical Africa has relatively lower richness and less diversity, but the evolution of tropical herpetofaunas, and the factors governing diversification through time at continental scales are poorly understood due to an understudied fossil record. The ecologies and geographic distributions of aniliid and uropeltoid snakes are examples. Modern species constitute either a grade or clade of fossorial, primarily wet forest taxa from South America and South Asia. Their distributions have historically been interpreted as Gondwanan vicariance following the isolation of Africa in the Early Cretaceous, but a definitive fossil record for these snakes is depauperate. Field research in the early Miocene (approx. 19 Mya) Tinderet sequence of western Kenya has produced precloacal vertebrae of an aniliid snake from multiple localities. Specimens possess vertebral apomorphies shared with extant South American Anilius scytale, including the morphology of the neural spine and prezygapophyseal angle. Combined with additional fossils from the Eocene of North Africa, the Tinderet records demonstrate an unambiguous past record of an extant neotropical snake lineage in Africa and falsify previous vicariance hypotheses. Recent stable isotopic and palynological studies of Neogene eastern African fossil localities have indicated heterogenous environments, including C4 grasses and wood- to scrubland, associated with vertebrate faunas. Comparing climate parameters of habitats for extant Anilius and uropeltoid snakes as ecological analogues to the Tinderet snake with modern ecosystems equivalent to those reconstructed for the eastern African early Miocene demonstrates only limited overlap in precipitation and temperature values. This discord indicates either greater environmental heterogeneity than reconstructed for the early Miocene of eastern Africa, or a greater range of habitat variability in aniliid snakes than observed in extant Anilius.more » « less
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