Pythons in the Eocene of Europe reveal a much older divergence of the group in sympatry with boas

Extant large constrictors, pythons and boas, have a wholly allopatric distribution that has been interpreted largely in terms of vicariance in Gondwana. Here we describe a stem pythonid based on complete skeletons from the early-middle Eocene of Messel, Germany. The new species is close in age to the divergence of Pythonidae from North American Loxocemus and corroborates a Laurasian origin and dispersal of pythons. Remarkably, it existed in sympatry with the stem boid Eoconstrictor. These occurrences demonstrate that neither dispersal limitation nor strong competitive interactions were decisive in structuring biogeographic patterns early in the history of large, hyper-macrostomatan constrictors and exemplify the synergy between phylogenomic and paleontological approaches in reconstructing past distributions.

现生大型绞杀类蛇类（蟒蛇科Pythonidae与蚺科Boidae）整体呈现完全异域分布格局，该分布模式长期以来被认为主要由冈瓦纳大陆（Gondwana）的隔离分化事件所塑造。本文基于德国梅塞尔（Messel）坑始新世早-中期地层中产出的完整骨骼化石，记述了一个蟒科（Pythonidae）的基干类群。该新种的生存时代与蟒科从北美林蚺属（Loxocemus）类群分化的时间极为接近，证实了蟒科起源于劳亚古陆（Laurasia）并通过扩散占据现有分布区的演化假说。值得注意的是，该新种与蚺科（Boidae）基干类群始新蚺属（Eoconstrictor）存在同域共存关系。这些化石发现表明，在大型超大口器绞杀类蛇类（hyper-macrostomatan constrictors）的演化早期，扩散限制与强烈的种间竞争均未成为塑造其生物地理格局的决定性因素；同时该研究也例证了系统基因组学与古生物学研究方法相结合，在重建古生物分布历史中的协同作用。