Ptychotrygon, JAEKEL, 1894

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 : 333-335

GENUS PTYCHOTRYGON JAEKEL, 1894

Type species: Ptychotrygon triangularis Reuss, 1845 from the Turonian of Bohemia, Czechoslovakia .

Remarks: Up to now, 20 species of Ptychotrygon have been described ranging from the Albian to the Maastrichtian. All species reported from the Palaeogene are either reworked specimens or misidentifications (Kriwet, J, pers. observ.).

PTYCHOTRYGON GEYERI KRIWET, 1999B

( FIGS 9Q–X , 10A–H )

Material: Six specimens, MPZ 2005–26. The specimens tend not to be complete, and often have large sections of the root missing.

Occurrence: Samples 2 and 4 from floodplain environments with channel deposits (facies 1 and 2) of the Utrillas to Mosqueruela Formations, (upper Albian and lower Cenomanian), Aliaga subbasin.

Description: The tooth crown is cuspidate, and broader than it is long. In occlusal view the crown is sub-triangular, and often has a fairly abrupt lingual face, with the main cusp lingually placed. The crown has a transverse occlusal crest and short vertical folds on the labial crown base. The apron is short and broad, and is well detached from the labial contour. The lingual face has a short uvula, with a rounded extremity, above which there is a weak central depression for tooth interlocking. The upper margin of the central depression is bounded by a weak ridge. The root is low, and appears not to extend below the crown. There are two root lobes separated by a well-developed median groove, with a large central foramen.

A single specimen ( Fig. 10Q–X ), which may represent a juvenile, displays a cuspidate crown, with a clear transverse crest and a longitudinal centrolabial ridge, which divides into several v-shaped ridges away from the apex. The apron is fairly broad with a rounded extremity. It is clearly detached from the labial contour and bent significantly basally.

Remarks: This species was described by Kriwet (1999b) from the Albian Utrillas Formation of the Aliaga subbasin. The teeth from the Cenomanian Mosqueruela Formation of the Aliaga subbasin display the characteristics of the species, e.g. short transversal ridges on the labial face on the crown shoulders, a short vertical ridge on the labial protuberance and a smooth lingual crown face except for some very delicate folds related to the lingual interlocking depression. The labial short transverse ridges below the transversal cutting edge are very faint and subtle in most specimens recovered from the Cenomanian. The occurrence of Ptychotrygon geyeri in the lower Cenomanian extends its range from the latest Early Cretaceous into the earliest Late Cretaceous.

The small, supposedly juvenile tooth resembles teeth of Libanopristis and Micropristis from the Cenomanian of Lebanon ( Cappetta, 1980b). However, it differs from both in several major characteristics such as a root not extending below the crown, a comparably higher root, absent lingual ridge above the interlocking depression as in Libanopristis and a more pronounced labial ornamentation than in Micropristis . The absence of well-marked but faint or even absent labial and lingual transversal crests and the presence of short labial ridges below the lateral heels attribute this specimen to P. geyeri .

Figures

Figure 9. A–P, Celtipristis herreroi (Kriwet, 1999b). A–D, anterior tooth. A, labial view. B, lateral view. C, lingual view. D, occlusal view. E–H, antero–lateral (?) tooth. E, labial view. F, lateral view. G, lingual view. H, occlusal view. I–L, lateral tooth. I, labial view. J, lateral view. K, lingual view. L, occlusal view. M–P, anterior tooth. M, labial view. N, lateral view. O, lingual view. P, occlusal view. Q–X, Ptychotrygon geyeri (Kriwet, 1999a). Q–T, lateral tooth. Q, labial view. R, lateral view. S, lingual view. T, occlusal view. U–X, latero-posterior tooth. U, labial view. V, lateral view. W, lingual view. X, occlusal view. All scale bars equal 0.5 mm.

Figure 10. A–H, Ptychotrygon geyeri (Kriwet, 1999a). A–D, anterior tooth. A, labial view. B, lateral view. C, lingual view. D, occlusal view. E–H, lateral (juvenile?) tooth. E, labial view. F, lateral view. G, lingual view. H, occlusal view. I–L, Ptychotrygon sp., lateral tooth. I, labial view. J, lateral view. K, lingual view. L, occlusal view. M–X, Ptychotrygon pustulata sp. nov. M–P, antero-lateral tooth. M, labial view. N, lateral view. O, lingual view. P, occlusal view. Q–T, anterior tooth. Q, labial view. R, lateral view. S, lingual view. T, occlusal view. U–X, lateral tooth. U, labial view. V, lateral view. W, lingual view. X, occlusal view. All scale bars equal 0.5 mm.