Découverte de vertébrés continentaux de l'Eocène moyen et supérieur dans le bassin des Matelles (Hérault, Sud de la France) et redécouverte du "Lophiodon des Matelles"

Abstract

The Matelles Basin, lying 20 km north of Montpellier and stretching between Saint-Gély-du-Fesc and Saint-Mathieu-de-Tréviers, has long ago been known for its mammal remains, including the famous "Lophiodon des Matelles" discovered by Dr Pittore in 1832. New data obtained from the Middle and Late Eocene when carrying out major works has made enabled a better palae-ontological characterization of certain local geological formations and their correlation with the palaeomammal scale (MP scale) levels. This note summarizes the obtained results. - Canlong locality: in beds with large oncoliths attributed to the base of the late Eocene (geological map of Montpellier, 1:50,000 scale). These de-trital beds, locally unconformable on the Planorbis pseudo-ammonius limestone and in places with algal bases, have yielded a relatively diverse fauna. Nine mammal species are recognized: primates - an Adapidae of indeterminate genus and species; rodents - a Theridomyidae assigned to Elfomys sp.; artiodactyls - an Haplobunodontidae assigned to an indeterminate Haplobunodon and a Dichobunidae represented by Hyper-dichobune sp.? (cf. H. nobilis); perisso-dactyls - the Palaeotheriidae Palaeo-therium nov. sp., Plagiolophus (? Paloplotherium sp.), Pachynolophus sp., Propalaeotherium cf. helveticum, and the Lophiodontidae Lophiodon tapiroides. This association enables the Canlong locality to be correlated with localities assigned to mammal level MP14 (i.e. Laprade, Egerkingen, Fontliasmes) and thus determines the age of the classical "Lophiodon des Matelles" which comes from the same geological formation. - In the same area, the Planorbis pseudo-ammonius limestone immediately underlying the oncolitic beds have previously yielded L. tapiroides and two artiodactyles - Tapirulus cf. majori at Grabels and Cebochoerus cf. dawsoni at Mas de Gentil. The two last species are known at Bouxwiller and enable the limestone to be correlated with level MP13. - Le Pont locality: a clay bed interstratified in the basal part of the Planorbis pseudo-ammonius limestone has yielded charophytes, reptile remains (indeterminate crocodilians and chelonians), the marsupial Amphiperatherium bastbergense Crochet, 1979, and the primate Buxella Godinot, 1988. The known range of the Buxella line enables this locality also to be assigned to level MP13. - Travers locality: a clay bed underlying the Planorbis pseudo-ammonius limestone has yielded charophytes, reptile remnants (indeterminate crocodilians and chelonians) as well as the primate Pseudoloris (Piveteaunia) isabenae. The stratigraphical position of this fossiliferous bed is similar to that of the clay bed at the locality and enables it also to be assigned to level MP13. The identified primate is the oldest of its line, P. isabenae having previously only been found at Aumelas (top of MP13) and at Capella and Lissieu (MP14). - Poteau 276 locality: this site marks the first point in the Matelles Basin where fossil remains have been recorded in the late Eocene fluviatile beds ('g1' on the geological map). The locality has yielded charophytes, pulmonates and a rodent incisor. Unfortunately these fragmentary data are not sufficient to determine the age of this formation, traditionally correlated with the Célas Sandstone (Gard, MP19). Most of the cited localities are contained in the Planorbis pseudo-ammonius limestone of reputed Lutetian age. The identified mammals place the localities fairly high up in the Lutetian (MP13, or top of MP13), however Languedoc contains no palaeonto-logically defined basal Lutetian that can be compared with the lower levels at Geiseltal which is the reference for this stage. The Canlong site, which can be added to the short list of European localities documenting the level MP 14, is an important regional marker due both to the number of taxa that it contains and to the value of these taxa in understanding the evolution and extinction of the ungulates during the middle Eocene.