PTYCHOTRYGONIDAE, Kriwet & Nunn & Klug, 2009

Kriwet, Jürgen, Nunn, Elizabeth V. & Klug, Stefanie, 2009, Neoselachians (Chondrichthyes, Elasmobranchii) from the Lower and lower Upper Cretaceous of north-eastern Spain, Zoological Journal of the Linnean Society 155 (2), pp. 316-347 : 333

FAMILY PTYCHOTRYGONIDAE FAM. NOV.

Type and only genus: Ptychotrygon Jaekel, 1894 .

Diagnosis: Sclerorhynchiforms characterized by the following dental features: teeth small; tooth crowns broader than long; crown with subtriangular outline in occlusal view and with more or less well-developed transversal crests on the labial face; number of transversal crests varying.

Remarks: The systematic position of Ptychotrygon within Sclerorhynchiformes has been the focus of much debate in recent years. For instance, Cappetta & Case (1999) consider Ptychotrygon as a member of either Sclerorhynchoidei or Rhinobatoidei . Despite all arguments, the tooth morphology identifies teeth of Ptychotrygon readily as belonging to Sclerorhynchiformes . Interestingly, although numerous species have been described from many localities of the northern hemisphere in recent decades, no associated rostral spines, which are characteristic for Sclerorhynchiformes , were recovered. Case (1987) and Kriwet (1999b) tentatively assigned enlarged placoid scales as possible rostral spines to Ptychotrygon . However, those enlarged placoid-scales also are found on the ligamentous band between rostrum and skull of sclerorhynchiforms ( Kriwet, 1999b) and the presence of rostral spines remains ambiguous.

Ptychotrygonidae fam. nov. can be differentiated from all other sclerorhynchiforms by the following combination of two diagnostic dental characters: transversal crest differentiating the labial crown face and very well-developed labial visor. The placement of Ptychotrygonidae within Batoidei and between Ptychotrygonidae fam. nov. and ‘true’ sclerorhynchiforms is, conversely, more dubious and can be validated only by the discovery of skeletal material to analyse the presence or absence of rostral spines. Underwood (2006) considers Celtipristis , Kiestus Cappetta & Case, 1999 and Ptychotrygon Jaekel, 1894 to represent additional, separately evolving, clades with no close relationships to Sclerorhynchiformes .

Landemaine (1991) erected the genus Ptychotrigonoïdes for isolated teeth of a taxon similar to Ptychotrygon and several other sclerorhynchiforms. The main distinguishing character is the very wellmarked depression of the lingual uvula and welldeveloped basal bulge of the root. However, these characters are also present in teeth of several species assigned to Ptychotrygon and we therefore consider Ptychotrigonoïdes to be synonymous with Ptychotrygon .