Lower molars of the large morganucodontan Storchodon cingulatus from the Late Jurassic (Kimmeridgian) of Germany

Abstract

AbstractThree new lower molars of Storchodon cingulatus and a fragmentary upper molar confirm its morganucodontan affinities. Cusps b and c are relatively higher than in Morganucodon, and cusp c is larger than cusp b. Cusp a is asymmetric, with slightly distally recurved tip. All known lower Storchodon molars have a pronounced furcation between the roots on the labial and lingual sides. The wear pattern of Storchodon corresponds to that observed in Morganucodon. Cusp A of the upper molar occludes into the valley between cusps a and c of the lower antagonist, causing large confluent wear facets. The smaller wear facets present on the mesiolabial flank of cusp b and the distolabial flank of cusp c were caused by cusp C of the upper antagonist that occluded into the embrasure between two lower molars. So far, the Morganucodon-like occlusal mode is restricted to the morganucodontans Morganucodon, Dinnetherium nezorum, Cifellilestes ciscoensis, and Storchodon cingulatus, whereas Megazostrodon and Erythrotherium exhibit embrasure occlusion. Although Storchodon belongs to the larger morganucodontans, it is questionable if it represents a case of island gigantism as suggested earlier.