Lamnidae Müller and Henle, 1838

Kriwet, Jürgen, Mewis, Heike & Hampe, Oliver, 2015, A partial skeleton of a new lamniform mackerel shark from the Miocene of Europe, Acta Palaeontologica Polonica 60 (4), pp. 857-875 : 860-861

Lamnidae Müller and Henle, 1838 Genus Carcharomodus nov.

Etymology: From Greek όμοιος (omoios), similar, and δόντι (donti), tooth; in combination with the name Carcharodon , in reference to the dental similarities with the living Great White Shark, Carcharodon carcharias .

Type species: Carcharodon escheri Agassiz, 1843 from the Mio-Pliocene of Europe ; monotypic .

Diagnosis.—Extinct lamnid shark characterised by the following combination of dental and vertebral characters: (i) dignathic and monognathic heterodonty patterns with upper teeth superficially resembling those of Cosmopolitodus , whereas lowers resemble those of Isurus to some extend; (ii) main cusp with crenulated cutting edges in all tooth positions; (iii) upper anterior teeth large and not compressed labio-lingually with distally inclined triangular main cusp; (iv) root of upper anteriors massive with sub-vertical to obliquely oriented edges in labial and lingual views and salient lingual protuberance; (v) intermediate tooth small, massive and hook-like; (vi) upper lateral teeth more or less labio-lingually compressed with sub-triangular distally directed cusps with straight cutting edges; (vii) tips of cusps curved labially in upper lateral teeth of juveniles and additionally curved distally in adults; (viii) labial face of crown more or less overhanging labial face of root; (ix) anterior lower teeth with weakly mesially flexed main cusp; (x) main cusp of third lower anterior (= lower intermediate) tooth upright with slightly longer mesial than distal cutting edge and with lingual curvature; (xi) main cusp height more than its width in lower anterolateral files; (xii) main cusp height is more than its width in lower posterolateral files; (xiii) lateral cusplets accompanying the main cusp present in all ontogenetic stages; (xiv) more than one pair of lateral cusplets might be developed in lateral teeth with second one being very incipient; (xv) lateral cusplets usually minute, broad, without crenulations and not distinctively separated from principal cusp; (xvi) lateral cusplets differently shaped in upper and lower teeth.

Differential diagnosis.—Teeth of Carcharomodus gen. nov. resemble teeth of Isurus , Cosmopolitodus , and Carcharodon to some extent. The combination of (i) a marked dignathic heterodonty pattern comprising upper teeth similar to those of Cosmopolitodus , but with more slender and generally more distally inclined or curved main cusps and lower teeth resembling those of Isurus ; (ii) marked monognathic heterodonty; (iii) massive and hook-like upper intermediate tooth; (iv) main cusps with crenulated (not serrated) cutting edges in all teeth; (v) presence of lateral cusplets in teeth of all ontogenetic stages; and (vi) presence of an additional pair of incipient cusplets in lateral positions readily distinguishes the new taxon from all other lamniform sharks.

More specifically, teeth of Carcharomodus gen. nov. distinctly differ from teeth of Carcharodon by the following characters: (i) main cusp of anterior teeth distally inclined with mesial cutting edge being longer than distal one; (ii) less dorso-ventrally flattened tooth crown; (iii) lateral edges of root lobes in lateral tooth positions rounded rather than being subvertical as in Carcharodon ; (iv) presence of lateral cusplets in all tooth positions throughout ontogeny; (v) intermediate upper tooth hook-like and not reversed; (vi) larger crown height/basal crown width ratio in lateral teeth; (vii) cusp tips of lateral teeth less curved distally; and (viii) basal crown margin in labial view less regularly arched being almost horizontal with only shallow medial concavity.

Teeth of the new genus most significantly differ from teeth of Cosmopolitodus in (i) having lateral cusplets; (ii) crenulated rather than smooth cutting edges; (iii) more slen- der main cusps in upper lateral teeth; (iv) more rounded lateral root edges in upper and lower lateral teeth; and (v) less pronounced and concavity of the basal root face in upper lateral teeth. The most significant differences to teeth of Isurus are (i) the serrated cutting edges and (ii) the presence of lateral cusplets also in adults. These differences unambiguously support the separation of the northern European from all other extinct and extant lamniform sharks.

Stratigraphic and geographic range.—Late early Miocene– Pliocene, Western and Central Europe.