Pontocypris, Sars, 1866

Forel, Marie-Béatrice, Kolar-Jurkovšek, Tea & Jurkovšek, Bogdan, 2020, Ostracods from the ‘ Raibl Beds’ (Carnian, Late Triassic) of Belca section in Karavanke Mountains, northwestern Slovenia, Geodiversitas 42 (21), pp. 377-407 : 388-390

Pontocypris ? karavankensis Forel, n. sp.

( Figs 6 R-U; 7A)

urn:lsid:zoobank.org:act:A5970888-0E6E-439B-84A0-40555CF417F0

TYPE MATERIAL. — Holotype: complete carapace ( Fig. 6S ), BE18 ( GeoZS6171 ). — Paratype: complete carapace ( Fig. 6R ), BE18 ( GeoZS6170 ).

EXAMINED MATERIAL. — Three right valves, three left valves and two complete carapaces.

DERIVATION OF NAME. — The specific epithet refers to the Karavanke Mountains in Slovenia, where is located the Belca section, type locality of the species.

OCCURRENCE. — Nicoraella ? budaensis conodont zone, late Julian-?earliest Tuvalian, Carnian, Late Triassic, samples BE18, 21 ( Fig. 3 ), Belca section, ‘Raibl Beds’, Karavanke Mountains, Slovenia (this work).

DIAGNOSIS. — A species with moderately elongate lateral outline, posterodorsal terminal concavity and concavity at the lower part of anteroventral border.

DIMENSIONS. — Fig. 5E.

DESCRIPTION

A thin-shelled species of medium size, subtriangular and moderately elongate in lateral view with greatest height at mid-length and greatest length in the lower 1/3rd of height; left valve larger than right valve, overlapping it all around with maximum at dorsal margin and ventral border; dorsal margin uniformly convex at both valves, without visible angulations, anterior slope straight and gentle (c. 20°), posterior slope steeper (c. 40°) with terminal concavity;anterior border largely rounded with maximum of curvature slightly below mid-length; posterior border tapered, narrow, pointed upward, with maximum of convexity in the lower 1/4th of height; ventral margin long, nearly straight at left valve, with tenuous median oral concavity; anteroventral border rounded with gentle concavity at the lower part, steeply raised upward; posteroventral border short and gently convex; surface smooth.

DISCUSSION

Pontocypris ? karavankensis Forel, n. sp. is restricted to the samples BE18 and 21 of the Belca section, with few specimens ( Fig. 3 ). We attribute this species with doubt to the genus Pontocypris Sars, 1866 because the material precludes the description of internal features. Pontocypris ? karavankensis Forel, n. sp. is close to several species from the Triassic period, which have been attributed to different genera. It is first close to Bairdia finalyi Méhes, 1911 from the Smithian-Ladinian interval of the Balatón Highland, Hungary ( Méhes 1911) but differs in being less elongate, with posterior border located more ventrally and anterior border less bairdiid. It is also close to Fabalicypris sp. 1 from the Rhaetian, Late Triassic, of Austria (only illustrated by a left valve;Mette & Mohtat-Aghai 1999), which differs by its more elongate and less pointed posterior extremity and more rounded anterior border. The Fabalicypris generic attribution is rejected for the Belca material as the typical abrupt anteroventral offset of the overlap of this genus is not observed. Pontocypris ? karavankensis Forel, n. sp. is finally close to P. richardsoni Anderson, 1964 from the Rhaetian, Late Triassic, of UK (Anderson 1964), from which it differs by its

more tapered and less elongate posterior end, terminal posterodorsal concavity and posterior border slightly pointed upward. The size dispersal shown in Fig. 5E indicates the presence of several ontogenetic stages. Owing to the size difference of the right and left valves of P.? karavankensis Forel, n. sp., at least three ontogenetic stages are recognized, A-2 to Adult. The ontogenetic development of this species is mainly characterized by the strengthening of the lateral asymmetry of the valves, the increase of the maximum of height, enlargement of anterior margin and posterior border becoming pointed upward.

Figures

FIG. 6. — Ostracods from the Belca section,Karavanke Mountains,northwestern Slovenia,Carnian,Late Triassic.All specimens are deposited in the micropalaeontology collections of the Geological Survey of Slovenia, under the numbers GeoZS6132 to GeoZS6239,preceded by sample number:A-C, Isobythocypris? sp. 1; A, lateral view of a right valve,BE2 (GeoZS6153);B, lateral view of a right valve,BE2 (GeoZS6154);C, lateral view of a right valve,BE2 (GeoZS6155);D, Isobythocypris sp. 2, lateral view of a right valve, BE18 (GeoZS6156); E-H, Mirabairdia longispinosa Kristan-Tollmann, 1978; E, lateral view of a right valve, BE21 (GeoZS6157); F, lateral view of a right valve, BE18 (GeoZS6158); G, lateral view of a right valve, BE18 (GeoZS6159); H, lateral view of a left valve, BE17 (GeoZS6160); I, Bythocypris? sp. 1, lateral view of a right valve, BE18 (GeoZS6161); J-L, Bythocypris? sp. 2; J, lateral view of a right valve, BE18 (GeoZS6162); K, lateral view of a left valve, BE18 (GeoZS6163); L, internal view of a right valve, BE18 (GeoZS6164); M-O, Bythocypris? sp. 3; M, right lateral view of a complete carapace, BE17 (GeoZS6165); N, lateral view of a left valve, BE18 (GeoZS6166); O, lateral view of a right valve, BE18 (GeoZS6167); P, Paracypris sp., lateral view of a left valve, BE18 (GeoZS6168); Q, Pontocyprella sp., lateral view of a left valve, BE18 (GeoZS6169); R-U, Pontocypris? karavankensis Forel, n. sp.; R, Paratype, right lateral view of a complete carapace,BE18 (GeoZS6170); S, Holotype, right lateral view of a complete carapace,BE18 (GeoZS6171); T, lateral view of a left valve, BE18 (GeoZS6172); U, lateral view of a left valve, BE18 (GeoZS6173). Scale bars: 100 μm.

FIG. 3. — Distribution of ostracod species through the Belca section, Karavanke Mountains, northwestern Slovenia.

FIG. 5. — Height/Length scatter plots of species recovered from the Belca section, Karavanke Mountains, northwestern Slovenia, Carnian, Late Triassic. In all diagrams, the dimensions of right and left valves of complete carapaces are linked. A, Bairdia balatonica Méhes, 1911; B, Bairdia cassiana (Reuss, 1869); C, Dicerobairdia buseri Forel, n. sp., all specimens are from the Belca section (this work); D, Mirabairdia longispinosa Kristan-Tollmann, 1978; E, Pontocypris? karavankensis Forel, n. sp. all specimens are from the Belca section (this work). Scale bars: 100 μm.