Scolecophidians or blind snakes are among the most primitive and smaller snakes in the world with an average of size of 10 cm. They are worm-like, fossorial, lucifugous and often colourless, eating ants, termites, and their larvae. Based on the revision of Vidal et al (2010) they are represented by 5 families mainly living in tropical areas and have had a long history on Gondwana. The only European representative of this group is Typhlops vermicularis that lives around the Mediterranean Basin. Here we describe two isolated procoelous trunk vertebrae from the early Paleocene of Hainin (MP1-5, Belgium), a locality already known for the oldest amphisbaenian lizards (Folie et al 2013) and the earliest European scincoid lizards (Folie et al 2005). These vertebrae are clearly attributed to a scolecophian by the following characters (List, 1966): they are 1.5 mm long and 1 mm high and wide; the centrum is narrow and the hemal keel is absent; the orientation of the prezygapophyses processes that serve for muscle attachment strongly differs from the one of the prezygapophyseal facets; the neural arch is depressed and does not present a posterior medial notch nor a neural spine. Fossil scolecophidians are identified based on their vertebrae but they are generally considered as not diagnostic at a familial, generic or specific level. However, some characters have recently been proposed to differentiate the family level on the basis of the shape and placement of the synapophyses, shape of the cotyle, size of the zygosphene, and shape of the prezygopophyseal facets (Gelnaw & Mead, 2010). Based on these features, the Hainin vertebrae differ from those of Anomalepidae and Leptotyphlopidae, and resemble those of Typhlopidae by similar neural arch morphology and height, development and orientation of the paradiapophysis, and morphology of the neural canal, cotyle and condyle. Record of fossil scolecophidians indicates their presence in North America, Europe, Africa and Australia. Before this study, the oldest representatives of this group were known from the late Paleocene of Adrar Mgorn (Ouarzazate Basin) in Morrocco and from the earliest Eocene of Dormaal (Tienen Formation, MP7) in Belgium. The scolecophidian from Hainin resembles more the one from Dormaal than that from Adrar Mgorn by narrower centrum and neural arch. The width of the neural arch in Typhlops is similar to both Belgian scolecophidians, however, the centrum is even narrower. By these characters, the scolecophidian from Hainin could represent a basal Typhlopidae.
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The mammal fauna of Hainin is particularly interesting as the oldest in the Cenozoic of Europe, and the earliest reference level (MP1–5) of the mammalian biochronological scale for the European Palaeogene. This paper summarizes the mammal taxa discovered in the fauna, presents an analysis of the fauna as a whole (relative abundance and species richness), and describes four new eutherians: Belgoryctes thaleri gen. et sp. nov., Eurolestes dupuisi gen. et sp. nov., Quadratodon sigei gen. et sp. nov. and Cingulodon magioncaldai gen. et sp. nov. The assemblage is relatively small (about 400 dental specimens), characterized by a high diversity and abundance of small insectivorous species and very low abundance of ‘plesiadapiforms’ and ‘condylarths’. By comparison with younger European Paleocene faunas, ‘condylarths’ and ‘plesiadapiforms’ became more and more abundant and diverse through the Paleocene but collapsed at the Paleocene–Eocene Boundary. ‘Proteutherians’ declined steadily, while multituberculates remained diverse, although the early Paleocene was populated mainly by Kogaionidae whereas the late Paleocene was dominated by Neoplagiaulacidae. The palaeoecology of Hainin is deduced from the mammal assemblage: the local environment was likely a forested area. Stratigraphically, the Hainin deposits are most likely of late Danian age, and biochronologically its fauna represents a partial equivalent of the North American Torrejonian Land Mammal Age. When compared to younger Paleocene faunas of Europe, the composition of the Hainin fauna reveals that a relatively important intercontinental dispersal of mammals occurred around the Danian–Selandian boundary, roughly corresponding to the Torrejonian–Tiffanian boundary. This dispersal is marked by the arrival in Europe of typically North American taxa such as arctocyonids, plesiadapids and neoplagiaulacid multituberculates. Additional exchanges of lesser magnitude probably also occurred around the Selandian–Thanetian boundary (i.e. during the Tiffanian), although the evidence is less compelling and mainly concerns the plesiadapids Chiromyoides and Plesiadapis.
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RBINS Staff Publications 2016
