Iberotrygon, 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 : 338-339

GENUS IBEROTRYGON GEN. NOV.

Derivation of name: From the Latin word ‘Ibero’ meaning ‘native of Iberia’, and the suffix ‘trygon’ in allusion to its occurrence and superficial dental similarities to sting rays.

Diagnosis: A small sclerohynchiform shark characterized by the following dental features: teeth small; crown cuspidate; cusp bulky, lingually inclined and well detached from crown shoulders; median labial crest present; short vertical crests along labial crown edge present, sometimes amalgamating in teeth of juvenile individuals to form short horizontal crests; lingual depression present, dorsally bordered by short transversal crest.

Differential diagnosis: Iberotrygon gen. nov. can be differentiated from all other sclerorhynchiforms by the following combination of diagnostic dental characters: ‘cross-like crown’ in occlusal view; no transversal labial ridges; lingually inclined central cusp; crown shoulders short; short knob-like ridges along the labial edge; median vertical labial crest, which sometimes bifurcates basally; short transversal crest bordering the lingual depression dorsally.

Taxa included: Iberotrygon plagiolophus gen. et sp. nov.

IBEROTRYGON PLAGIOLOPHUS GEN. ET SP. NOV.

( FIG. 11Q–X )

Derivation of name: From the Greek words ‘plagios’ meaning ‘horizontal’, and ‘lophos’ meaning ‘crest’, in allusion to the short, horizontal crest bordering the lingual depression dorsally.

Holotype: An antero-lateral tooth, MPZ 2005-33 ( Fig. 11Q–T ).

Paratypes: Four well-preserved teeth, MPZ 2005-34 ; a single juvenile? tooth, MPZ 2005-35 .

Horizon and locality: Sample 4 from facies 2 (floodplain environment with channels) of lower Mosqueruela Formation (lower Cenomanian), Aliaga subbasin.

Diagnosis: Same as for genus, monotypic.

Description: The tooth crown of this small batoid is cuspidate, with a well-developed, high, pointed, main cusp that is inclined lingually in teeth of juveniles and adults. The lingual margin of the crown overhangs the root, especially towards the apex. The crown is bulky and well defined. The crown shoulders are short and low. The cutting edge is blunt but continuous between the central cusp and crown shoulders. In occlusal view the crown is devoid of distinct transversal crests. However, there is some ornamentation, most notably a longitudinal medio-labial ridge, which sometimes bifurcates basally delimiting the apron. There are conspicuous short vertical ridges at the labial crown base. These vertical ridges occasionally are amalgamated in smaller, probably juvenile teeth forming a short transversal crest similar to those found in Ptychotrygon ( Fig. 11U–X ). The apron is broad, with a rounded extremity that is bent basally and is detached from the labial contour. The lingual face is fairly steep, and has a well-developed vertical directed uvula, above which is a well-marked central depression. This depression is bordered dorsally by a short and slightly convex transversal crest, which is constrained to the central cusp. The root is low and narrow, with narrow lobes separated by a broad, but deep central groove. There is no basal bulge.

Remarks: The teeth of Iberotrygon gen. nov. display some sort of ontogenetic variation. According to the available material, teeth of juvenile individuals seemingly differ from adult ones in the presence of amalgamated vertical ridges into short transversal crests and the presence of a vertical labial crest that tends to bifurcate basally in teeth of adults.

Teeth of Iberotrygon gen. nov. resemble those of Ptychotrygon , Texatrygon and Archingeayia to some extent but can easily be distinguished from those by the character combination indicated in the diagnosis.

In particular, teeth of Ptychotrygon are characterized most conspicuously by transversal crests dividing the labial crown face. In having short vertical labial crests, the teeth of Iberotrygon gen. nov. resemble those of Texatrygon (e.g. T. hooveri from the Turonian–Coniacian of Texas, USA, see Cappetta & Case, 1999). Differences are, however, found in the more bulky central cusp, the shorter and higher crown shoulders, which are almost horizontal, and the lingual crest, which borders the lingual depression and is confined to the central cusp.

Teeth of Archingeayia from the Cenomanian of France differ in the more erect and more labiolingually compressed crown in profile view, the almost triangular crown in labial and lingual view without differentiated crown shoulders, the presence of a basal marginal ridge along the labial and lingual crown borders and the presence of vertical crests enframing the lingual depression.

The character combination indicated in the differential diagnosis (e.g. absence of transversal labial ridges, lingually inclined cusp, short crown shoulders, knob-like ridges along the labial edge, median vertical labial crest, and a short transversal crest bordering the lingual depression dorsally) easily distinguish teeth of Iberotrygon gen. nov. from teeth of all other sclerorhynchiforms and rhinobatoids. The new taxon is only known from the Aliaga subbasin and is considered to represent an endemic benthic taxon of shallow, near-coastal waters of the Tethys.

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.