Premontreia (Premontreia) uralica, Malyshkina, 2006

Malyshkina, Tatiana, 2006, Late Eocene scyliorhinid sharks from the Trans-Urals, Russia, Acta Palaeontologica Polonica 51 (3), pp. 465-475 : 469-471

publication ID	https://doi.org/ 10.5281/zenodo.13651136
persistent identifier	https://treatment.plazi.org/id/444087E3-B95E-FF82-9E7E-0A30799CFA45
treatment provided by	Felipe
scientific name	Premontreia (Premontreia) uralica
status	sp. nov.

Treatment

Premontreia (Premontreia) uralica sp. nov.

Figs. 2 View Fig , 3 View Fig , Table 1.

Derivation of the name: From the Urals, Latinised.

Type locality: Kurgan. The clay pit of the Kurgan brick factory in the northern part of Kurgan city, South Trans−Urals , Russia .

Type horizon: Upper part of the gray−green clays of the Tavda Formation.

Age: Priabonian, Charlesdowinea clathrata angulosa Dinoflagellate Zone.

Holotype: PIN 5088 View Materials /01, lower anterior−lateral tooth ( Fig. 2A View Fig ).

Paratype: PIN 5088 View Materials /02, upper anterior−lateral tooth ( Fig. 2B View Fig ) .

Material. — Kurgan: 45 teeth, Derney: 8 teeth.

Diagnosis.— Premontreia species only known from isolated teeth. The teeth are up to 6.0 mm high. The principal cusps have rectilinear or almost rectilinear lateral edges, without a “waist”. The crowns, which bulge labio−lingually, are vertical in anterior teeth and slightly inclined in lateral teeth. The labial face of the crown is slightly convex, the lingual face is convex. The enameloid is smooth on the most of the teeth, sometimes with very short and barely distinct folds on the labial crown base. The cusplets are low, triangular in the labial view, closely set to the main cusp. The enameloid below the junction of cusp and cusplets is high, cutting edge is entire. The root is thick, protrudes over the crown, the basal face of the root is flat. The nutritive groove is wide and shallow. It divides the basal face of the root labio−lingually and appears lingually on the upper face of the root. There are number of small and some large foramina on the margino−lingual faces of the root. The central foramen is placed lingually in the nutritive groove.

Description

Holotype ( Fig. 2A View Fig ).—PIN 5088/01, a lower anterior−lateral tooth. The main cusp is triangular, slightly bent distally, with rectilinear mesial and distal edges and has a slight labio−lingual sigmoid twisting. The labial crown base has a series of short, centrally−placed, vertical folds. There is a pair of triangular cusplets, whose axis slightly laterally deviates from the main cusp; a second small cusplet is placed distally of the mesial cusplet. The root is thick, with a smooth contour, the branches are not well developed. The root protrudes behind the crown and forms the “pedestal” surrounding crown base. The nutritive groove is more wide than deep, slightly widened from the center of the basal face to the lingual side. There are some large nutritive foramina on the lingual face of the root and one large labially−situated central foramen in the nutritive groove.

Paratype ( Fig. 2B View Fig ).— PIN 5088 View Materials /02, upper anterior−lateral tooth. The main cusp is triangular, slightly bent distally, but upper third of the cusp is vertical. The main cusp has a weak labio−lingual sigmoid twisting. The mesial cusplet is less separated from the main cusp than that on the holotype, the tip is not sharp. The distal cusplet is reduced, there is just a smooth ledge. The root branches are more marked than in the holotype: there are pronounced bulges, separated by the depression under the central part of the crown base ( Fig. 2B View Fig 1 View Fig , B 4 View Fig ). The nutritive groove is widened in the central part and almost closed on the central protuberance. There are some large and small nutritive foramina on the lingual surface of the root. The central foramen is large, and lingually situated .

Anterior tooth ( Fig. 3A View Fig ).—IGG 8SP/Ku−87/21, shows the smooth enameloid on the both faces of the crown. There are one pair of the cusplets. The main cusp and distal cusplet are broken. The mesial cusplet is not high, acute−angled, slightly deviates laterally from the main cusp. The root is flat and thick, protrudes behind the crown and forms the “pedestal” round the crown. The basal face is flat. The root lobes are not developed, the root base in the labial view is straight. The nutritive groove is doubled ( Fig. 3A View Fig 5 View Fig ), which is obviously an anomaly: there is a wide and shallow main nutritive groove displaced to the distal side of the root and another one almost equal to the main groove, but only the main groove extends on the labial and lingual faces of the root. There is a central foramen displaced lingually in the main groove and some smaller foramina in both grooves as well as on the lingual and labial faces of the root.

The lateral tooth ( Fig. 3B View Fig ).—IGG 8SP/Ku−87/22, shows the smooth enameloid with the slight striation on the base of the labial face. The labial face of the crown is convex, the lingual face is very convex. The main cusp is bent distally and has a strong labial−lingual bend. There is one pair of the cusplets. The cusplets are small, not sharp, closely set to the main cusp. The root has a flat base. The contour of the root base in the labial view as well as the line of the root−crown connection is arched. The root lobes are not well developed. There is a well−developed nutritive groove, slightly widened in the central part of the basal face of the root. There are some foramina of the oval shape on the labial and lingual faces of the root.

Comparisons and remarks.—The differences between Premontreia uralica sp. nov. and P. subulidens ( Arambourg 1952: 121, pl. 23: 5–19; Noubhani and Cappetta 1997: 55, pl. 21) are that the teeth of P. uralica have: (1) labio−lingually and medio−distally thicker crowns, so that the contour of the main cusp is a triangle with a wider base; (2) rectilinear or subrectilinear mesial and distal edges of the cusp; (3) distinctive enameloid ornamentation on the labial crown base; (4) shorter and less acute−angled cusplets; their axes more deviate from the cusp; (5) the root is more massive and high. The same differences apply to P. degremonti ( Cappetta 1992: 640, pl. 1), except for the cusplet characters and that P. degremonti has a more intensive striation near the base of its labial crown face.

Premontreia (Oxyscyllium) gilberti (Casier, 1946) differs from the P. uralica sp. nov. by more intensive striation on the labial face of the crown and overhanging of the root crown labial face, as well as by narrower main cusp in the lower teeth.

Premontreia (Oxyscyllium) dachiardi (Lawley, 1876) has a smooth enameloid overhanging the root labially and a different root shape.

Distribution.—Priabonian of the West−Siberian Basin.