Kasimlara kosuni, Kiel, 2018

Kiel, Steffen, 2018, Three new bivalve genera from Triassic hydrocarbon seep deposits in southern Turkey, Acta Palaeontologica Polonica 63 (2), pp. 221-234 : 226

Kasimlara kosuni sp. nov.

Figs. 4 , 5 .

2017 new genus of bivalve clade Modiomorphida ; Kiel et al. 2017:

fig. 4D.

Etymology: For Erdal Koşun (Antalya, Turkey).

Type material: Holotype: Mo184061, an internal mold of a large left valve. Paratypes: Mo184062–184064) from the type locality.

Type locality: The Terziler III seep deposit (southern Turkey) .

Type horizon: Late Carnian, Late Triassic seep deposits of the Kasımlar shales.

Material.—The type material and three further specimens from the type locality; see Table 2 for measurements.

Diagnosis.—As for genus.

Description.—Strongly inflated, modioliform shell that is laterally curved to some degree, with the direction of curving differing between specimens; umbo subterminal, strong ridge running from umbo to posteroventral margin; anterior adductor muscle scar small but deep, cone-shaped pointing toward the anterior; onset of pallial line posterior to anterior adductor muscle scar, distant from ventral margin and running subparallel to it; secondary pallial attachment scars occur as pits at the anterior side of the shell, along the ventral margin they are fine but numerous and strongly inclined anteriorly; very small pallial sinus, posterior adductor muscle scar indistinct, round; inner shell surface with fine radial striations close to the dorsal and ventral margins, and pustules in the area between. The largest specimen reaches 57 mm in length, 26 mm in height, and the single valve is 11 mm thick.

Remarks.—The lateral curvature of the shell is either to the left, as in the holotype (meaning that the commissure of the right valve is concave, that of the left valve is convex), whereas the two paratypes illustrated in Fig. 5 are curved to the right. I have not seen any specimen without lateral curvature.

Figures

Fig. 4. The kalenterid bivalve Kasimlara kosuni gen. et sp. nov. from the late Carnian, Late Triassic Terziler III seep deposit in southern Turkey. A. Mo184061, holotype, large internal mold of right valve; lateral (A1), lateral-ventral (A2), ventral (A3), lateral-dorsal (A4), and anterior (A5) views. B. Mo184062, internal mold of anterior part of left valve; showing tubercles (as pits in the mold) on the lateral side of the shell’s interior (B1), fine radial striation on the dorsal inner side of the shell (B2), ventral view on the dorsal inner side of the shell (B3), anterior side, note the strong inflation of the shell (B4).

Fig. 5. The kalenterid bivalve Kasimlara kosuni gen. et sp. nov. from the late Carnian, Late Triassic Terziler III seep deposit in southern Turkey. A. Mo184063, internal mold of an articulated specimen; left (A1) and right (A2) valves, dorsal (A3) and ventral (A4) sides, showing the curvature of the shell. B. Mo184064, internal mold of articulated specimen; left (B1) and right (B2) valves, dorsal (B3) and ventral (B4) sides, showing the curvature of the shell; note the strong, healed predation scars on the posterior side of the left valve (B1) and on the posteroventral side of the right valve (B4).