Ptychotrygon striata, 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 : 336-338

PTYCHOTRYGON STRIATA SP. NOV. ( FIG. 11A–P )

Derivation of name: From the Latin word ‘striatus’, ‘striated’, in allusion to the ridges above the lingual interlocking depression.

Holotype: An anterior tooth, MPZ 200-31 ( Fig. 11A– D ).

Paratypes: Nine generally well-preserved teeth; MPZ 2005-32 .

Horizon and locality: Sample 4 from floodplain environments with channel deposits (facies 2) of the lower Mosqueruela Formation (lower Cenomanian), Aliaga subbasin.

Diagnosis: A species of Ptychotrygon characterized by the following dental features: high and well-cuspidate tooth crown; short and convex labial crown face in profile view; several labial ridges originating from a vertical labial crest; additional irregular and short ridges present; transversal labial and lingual crests on the same; lingual depression well marked; short and flexuous ridges above lingual depression present.

Description: The teeth are small and broader than long, with a high cuspidate and pyramidal crown. The central cusp is well developed, and is upright and lingually placed, with a well-marked transverse occlusal crest running through the apex. This crest is bent lingually towards the crown edge in one specimen. In occlusal view the teeth are heavily ornamented, with ridges radiating from the apex. The labial face has a longitudinal centro-labial ridge, which converges at the apex, and divides into several v-shapes towards the apron. There are several short sub-vertical folds originating at the crown base, and extending perpendicularly towards the lingual face in profile view. The apron is rather long and prominent, with a rounded anterior extremity that is bent slightly basally, and is well detached from the labial contour. The uvula is short and broad with a rounded extremity and pronounced central depression. The top of the central depression is bounded by strong vertical ridges converging towards the apex. In profile view the lingual face is much more abrupt than the labial one. The root is low, slightly displaced lingually, and does not extend laterally beyond the crown. There are two sub-triangular root lobes, separated by a broad and deep groove with a central foramen. The margino-lingual faces have one pair of well-marked margino-lingual foramina.

Remarks: This species is similar to Ptychotrygon slaughteri , from the Cretaceous of Texas ( Cappetta & Case, 1999), especially in terms of its occlusal ornamentation. However, P. slaughteri has a marked step-like appearance in occlusal view as a result of a rounded, convex crest that borders the lingual depression. This step-like aspect is not seen in this species due to the absence of the lingual crest. Instead, the central depression of this species is bordered by strong lingual ridges that converge towards the apex. It differs from all other species of Ptychotrygon in the combination of a well-cuspidate crown, a short and convex labial crown face in profile view, several labial ridges originating from a vertical labial fold, and additional irregular and short ridges, a transversal lingual crest on the same level as the labial one and additional vertical ridges above the lingual interlocking depression.

ORDER SCLERORHYNCHIFORMES, FAM. INDET.

Figures

Figure 11. A–P, Ptychotrygon striata sp. nov. 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, antero-lateral tooth. I, labial view. J, lateral view. K, lingual view. L, occlusal view. M–P, lateral tooth. M, labial view. N, lateral view. O, lingual view. P, occlusal view. Q–X, Iberotrygon plagiolophus gen. et sp. nov. Q–T, antero-lateral tooth. Q, labial view. R, lateral view. S, lingual view. T, occlusal view. U–X, anterior juvenile(?) tooth. U, labial view. V, lateral view. W, lingual view. X, occlusal view. All scale bars equal 0.5 mm.