The Earliest Colubroid-Dominated Snake Fauna from Africa: Perspectives from the Late Oligocene Nsungwe Formation of Southwestern Tanzania

Abstract

The extant snake fauna has its roots in faunal upheaval occurring across the Paleogene - Neogene transition. On northern continents, this turnover is well established by the late early Miocene. However, this transition is poorly documented on southern landmasses, particularly on continental Africa, where no late Paleogene terrestrial snake assemblages are documented south of the equator. Here we describe a newly discovered snake fauna from the Late Oligocene Nsungwe Formation in the Rukwa Rift Basin of Tanzania. The fauna is small but diverse with eight identifiable morphotypes, comprised of three booids and five colubroids. This fauna includes Rukwanyoka holmani gen. et sp. nov., the oldest boid known from mainland Africa. It also provides the oldest fossil evidence for the African colubroid clade Elapidae. Colubroids dominate the fauna, comprising more than 75% of the recovered material. This is likely tied to local aridification and/or seasonality and mirrors the pattern of overturn in later snake faunas inhabiting the emerging grassland environments of Europe and North America. The early emergence of colubroid dominance in the Rukwa Rift Basin relative to northern continents suggests that the pattern of overturn that resulted in extant faunas happened in a more complex fashion on continental Africa than was previously realized, with African colubroids becoming at least locally important in the late Paleogene, either ahead of or as a consequence of the invasion of colubrids. The early occurrence of elapid snakes in the latest Oligocene of Africa suggests the clade rapidly spread from Asia to Africa, or arose in Africa, before invading Europe.

The microvertebrates of Qesem Cave: A comparison of the two concentrations

“…The following combination of characters (not all apomorphic) supports the identification of an elapid in the assemblage (Szyndlar, 1991;Scanlon et al, 2003;McCartney et al, 2014): relatively short centrum (CL/NAW < 1.2), long, low, flat neural spine with expanded dorsal edge, small parapophyseal processes, and strong subcentral ridges (Fig. 7D) (Pallas, 1766) A few remains (2 incisors, 7 M fragments, 1 mandibula fragment) were found in both concentration areas.…”

Fossil amphibians and reptiles from the Neogene locality of Maramena (Greece), the most diverse European herpetofauna at the Miocene/Pliocene transition boundary

“…However, it is known that partial or even total absence of hypapophyses in the mid-trunk and posterior trunk vertebrae is in fact a more widespread feature within snakes. Besides "colubrines", it also occurs in various elapoids (e.g., psammophiids) and dipsadids (Pyron et al, 2013;Head et al, 2016), whereas at least one natricine taxon without hypapophyses on the posterior trunk vertebrae has been documented (Malnate, 1972;Ikeda, 2007;McCartney et al, 2014). Therefore, caution should be taken into consideration when dealing with such taxonomic assignements and the name "Colubrinae" should be more safely placed in quotation marks (e.g., Szyndlar, 2012).…”

Small vertebrates from Khasm El-Raqaba, late Middle Miocene, Eastern Desert, Egypt

“…The oldest unambiguous colubroids are from the early to middle Eocene of South Asia (Rage et al 1992(Rage et al , 2005, and the oldest unambiguous African record is from the late Oligocene of Tanzania (McCartney et al 2014), suggesting entry into Africa no later than the middle Paleogene. By the early Miocene, colubroids, including colubrines, had dispersed from northwestern to southern Africa (e.g., Rage 1976Rage , 2003.…”