Mennerotodus glueckmani Zhelezko, 1994

Cicimurri, David J., Ebersole, Jun A. & Martin, George, 2020, Two new species of Mennerotodus Zhelezko, 1994 (Chondrichthyes: Lamniformes: Odontaspididae), from the Paleogene of the southeastern United States, Fossil Record 23 (2), pp. 117-140 : 121

Mennerotodus glueckmani Zhelezko, 1994 , middle Eocene (Bartonian), Shorym Formation, Mangyshlak, Kazakhstan.

Emended generic diagnosis

Mennerotodus teeth can be divided into anterior, intermediate, lateral, and posterior tooth groups. The upper dentition consists of three anterior tooth files, whereas the lower dentition includes four anterior files, and in general the anterior teeth have a tall and narrow triangular main cusp, with a highly convex lingual face and a virtually flat labial face. The enameloid on the main cusp is generally smooth, but faint longitudinal ridges have been observed on the lower half of the crown on a small number of teeth. The main cusp is sinuous in profile view, and the teeth have a single pair of small and conical lateral cusplets. The cutting edges on the main cusp are incomplete and do not extend to the base of the crown. On some teeth one or more denticles are present between the cutting edge and the lateral cusplets, and at times this denticle is expressed as a small ridge that is separate from the main cutting edge. The root lobes are thin with rounded extremities, and a conspicuous nutritive groove is located on a robust lingual root protuberance. The interlobe area on the anterior teeth is generally U-shaped. The first lower anterior tooth is conspicuously smaller in size than the other anterior teeth, and it has an extremely narrow main cusp and elongated distal root lobe. The main cusp on the third upper anterior tooth has a slight mesial bend and an extended mesial root lobe.

The intermediate teeth have a much lower main cusp than the anterior teeth and are smaller in overall size. The height of the root is greater than the height of the crown, and the teeth are labiolingually compressed. The main cusp has a slight distal bend, and a single pair of lateral cusplets are extremely tall in comparison to the overall height of the main cusp.

The lateral teeth are similar to the anterior teeth but have a shorter and more broadly triangular main cusp. The main cusp has a profile that is flat to only slightly sinuous, and this sinuosity is not to the degree seen on anterior teeth. The lateral teeth have one pair or very rarely two pairs of lateral cusplets, and these cusplets are larger and more triangular than those on the anterior teeth. When a second pair of cusplets occurs, they are generally diminutive and united to the outer edge of the larger, more medial cusplet. Denticles occur at the base of the main-cusp cutting edge (medial to the lateral cusplets) on about 30 % of the teeth. These denticles are larger than those observed on the anterior teeth and can occur in greater numbers. Although the crown faces are generally smooth, fine vertical ridges are developed on some teeth. The root lobes are short and divergent and have rounded extremities, and the interlobe area can be U-shaped or V-shaped. A conspicuous nutritive groove occurs on a robust lingual root boss. The main cusp is distally inclined on the upper lateral teeth but more erect in the lower lateral files.

The posterior teeth are similar to the lateral teeth but can be differentiated by their having a labiolingual width that is nearly equal to the overall height of the tooth. The main cusp is extremely low and triangular (6B, 12A), and the teeth have a single pair of wide and triangular lateral cusplets. The teeth have a shallow and V-shaped interlobe area, and the upper posterior teeth have a more distally inclined main cusp than those in the lower posterior positions.