Kalolophus chipolanus ( Dall, 1903 )

Devries, Thomas J., 2016, Fossil Cenozoic crassatelline bivalves from Peru: New species and generic insights, Acta Palaeontologica Polonica 61 (3), pp. 661-688 : 681

Kalolophus chipolanus ( Dall, 1903)

Fig. 4E− H .

1903 Crassatellites (Scambula) chipolanus sp. nov.? [sic!]; Dall 1903: 1472, pl. 49: 12.

1926 Crassatellites (Scambula) chipolanus Dall ; Gardner 1926: 86, pl. 16: 10.

Type material: Holotype, complete adult right valve with hinge exposed: USNM 114713 a, L 43.8, H 33.3, T 11.3 . Paralectotypes, designated herein, from the same type locality as the holotype: USNM 114713 b, L 38.8, H (25.7), T 8.4; 114713c, L 24.5, H 19.8, T 5.2; 114713d, L 24.3, H 19.2, T 5.7; 114713e, L 18.4, H 14.3, T 4.6.

Type locality: No. 2212, Tenmile Creek, 1 mile west of Bailey’s Ferry , Calhoun County, Florida ( Gardner 1926: 86) .

Type horizon: Chipola Formation , lower Miocene .

Material.— UF 85322a, L (40.0), H 30.7, T 10.6; UF 85322b, L 26.2, H 20.7, T 7.9; UF 85322c, L 40.6, H 28.0, T 9.1; UF 85322d, L 39.3, H 30.6, T 10.1; UF 85322e, L 45.5, H 31.8, T 10.6; UF 85322f, 48.2, H 30.7, T 10.3; UF 85322g, L 46.2, H 36.1, T 13.8; UF 85322h, L 41.7, H 27.9, T 8.9; UF 85322i, L 23.9, H 19.5, T 5.9; UF 85322j, L 26.3, H 18.7, T 5.8; UF 85322k, L (26.0); UF 85322l, L 39.4, H 30.7, T 10.3. All from Farley Creek 04 ( CA 012), Calhoun County, Florida; Tulane University locality TU821.

Emended diagnosis.—Umbo with widely spaced commarginal ribs. Exterior with closely spaced commarginal ribs, sometimes absent medially and posteriorly.

Description.—Shell length to 45 mm, trapezoidal, beak located two-fifths distance from anterior, L: H ratio 1.2−1.5, T: H ratio 0.2−0.25, maximum inflation ventral to beak, nearly as inflated posteriorly as medially. Anteriodorsal and posteriodorsal margins straight to slightly concave. Anterior margin sharply rounded, posterior margin variably produced, broadly truncate, ventral margin evenly rounded, slightly pinched posteriorly. Angular posterior ridge with sulcus on both sides, diverging 20−25°, weak secondary posterior ridge 5° from posteriodorsal margin. Lunule and escutcheon elongate, equally wide, about half the length of respective margins. Beak prosogyrate. Umbo flattened, slightly opisthogyrate to orthogyrate, with widely spaced commarginal ribs. Anterior with closely spaced commarginal ribs; shell medially and posteriorly ribbed or smooth with fine irregularly spaced growth lines. No commarginal ribs posterior to primary posterior ridge. Resilifer extending to or nearly to vmHP. Left anterior cardinal tooth narrow, wedge-shaped, inclined anteriorly 40°, extending from vmHP to beak. Left posterior cardinal tooth lamellar, inclined anteriorly 15−20°. Right anterior pseudocardinal tooth coalesced with lunule. Right cardinal tooth thick, wedge-shaped, inclined anteriorly 20−25°. Right posterior pseudocardinal tooth lamellar, diverging 10−15° from midpoint of cardinal tooth, orthocline. Inner ventral margin smooth.

Remarks.—Specimens of early Miocene Floridian Kalolophus chipolanus differ from the lower Oligocene Floridian Crassatella portelli precisely in the characters that distinguish the two genera: the presence of a non-truncate left anterior cardinal tooth and full-length resilifer in the former and crenulated inner ventral margin in the latter. Consistent differences between K. chipolanus and other circum-Caribbean species of Kalolophus , excepting K. antillarum , are not readily apparent.

Stratigraphic and geographic range.— Chipola Formation, lower Miocene , Florida .

Figures

Fig. 4. Crassatelline bivalves from Florida. A−D. Crassatella portelli sp. nov., early Oligocene, Suwannee limestone. A. UF 26990a, holotype, exterior A1) and interior (A2), and dorsal margin (A3) of left valve. B. UF 32046b, paratype, dorsal margin of right valve.C. UF 27019, paratype, exterior (C1) and interior (C2) of right valve. D. UF 26990b, paratype, interior of left valve. E−H. Kalolophus chipolanus (Dall, 1903), early Miocene, Chipola Formation. E. USNM 114713c, exterior of left valve (E1), interior (E2). F. UF 85322l, interior of left valve. G. USNM 114713a, holotype, exterior (G1), interior (G2), and dorsal margin (G3) of right valve. H. UF 85322f, exterior of left valve. Scale bars 10 mm.