Adapisoriculus Lemoine 1885

Bast, Eric De, Sigé, Bernard & Smith, Thierry, 2012, Diversity of the adapisoriculid mammals from the early Palaeocene of Hainin, Belgium, Acta Palaeontologica Polonica 57 (1), pp. 35-52 : 46-47

Genus Adapisoriculus Lemoine 1885

Type species: Adapisoriculus minimus ( Lemoine, 1883) , Cernay−lès− Reims, late Palaeocene; by monotypy.

? Adapisoriculus sp.

Fig. 8 .

Material.— IRSNB M2009 (W2−02), right M3, early Palaeocene of Hainin, Hainaut province, Belgium..

Measurements.—M3: L = 1.30 mm; W = 1.97 mm.

Description.—The M3 is the only known complete molar of this taxon. The tooth is strongly dilambdodont and the wide stylar shelf has three cusps (parastyle, stylocone and mesostyle). The metastylar lobe is absent, whereas the parastylar lobe accounts for more than one third of the occlusal surface. The preparacrista is long and runs parallel to the labiolingual axis of the tooth, isolating a portion of the parastylar lobe lower than the stylar shelf. There is no postmetacrista. The paracone and metacone are well separated down to their bases, and linked by a strongly dilambdodont centrocrista. The metacone is greatly reduced and points posteriorly, with the paracone occupying a more lingual position than the latter. The paracingulum is very narrow and there is no metacingulum. The protofossa is wide and deep, and delimited by poorly marked crests. The paraconule and metaconule are clearly visible, but the internal crests are indistinct.

Discussion.—The M3 attributed to? Adapisoriculus sp. shares with A. minimus a high degree of dilambdodonty, a wide protofossa with no clearly marked internal crests, and a rounded lingual region of the protocone. The comparison with A. minimus is difficult, both because no M3 has been described for that species and because the tooth described here is damaged, making it difficult to observe the exact topology of the cusps and crests. However, the stylar cusps seem less developed than in A. minimus , possibly indicating the presence of another species. The metacone of M3 is markedly more reduced than in Afrodon and Bustylus , which is probably a derived character.

Figures

Fig. 8. SEM pictures of the adapisoriculid?Adapisoriculus sp. from the early Palaeocene of Hainin (Belgium). Right M3, IRSNB M2009 (W2−02), in labial (A) and occlusal (B) views.