Crassatella portelli, Devries, 2016

Devries, Thomas J., 2016, Fossil Cenozoic crassatelline bivalves from Peru: New species and generic insights, Acta Palaeontologica Polonica 61 (3), pp. 661-688 : 667-670

Crassatella portelli sp. nov.

Fig. 4A− D .

Etymology: Named in recognition of help provided by Roger W. Portell (Florida Museum of Natural History).

Type material: Holotype, complete adult left valve with hinge exposed: UF 26990 A, L 38.9, H 28.5, T 9.1 . Paratypes: UF 26990 B, H 30.7, T 10.2; UF 27019 , L 34.0, H 24.7, T 8.3; UF 32046 B, L 35.9, H 27.4, T 8.3; UF 198567 A, L 32.8, H 24.9, T 7.2; UF 241619 , L 29.6, T 7.4; UF 243868 A, L 36.3, H 27.3, T 8.3; from the type locality.

Type locality: Terramar pit 01, Socrum Quadrangle, Polk County, Florida, USA .

Type horizon: Suwannee Limestone , mining spoils, lower Oligocene .

Material.— UF 32046 , additional 4 specimens ; UF 198567 , additional 3 specimens ; UF 243868 , additional 2 specimens . All specimens are from the type locality.

Diagnosis.—Shell trapezoidal, not inflated. Resilifer extending half the distance or more to vmHP. Umbo flattened. Left anterior cardinal tooth extending to or nearly to beak. Exterior with commarginal ribs. Inner ventral margin crenulate.

Description.—Shell to 40 mm long, trapezoidal, not inflated, L:H ratio 1.3, T:H ratio 0.2, maximum inflation ventral to beak. Anteriodorsal and posteriodorsal margins slightly concave; anterior margin broadly rounded, posterior margin weakly produced, broadly truncate; ventral margin evenly rounded. Strongly angular posterior ridge diverging 20−25°, secondary posterior ridge 5° from posteriodorsal margin. Lunule and escutcheon elongate, equally wide, both about 40% length of respective dorsal margins. Beak prosogyrate. Umbo flattened, slightly prosogyrate to slightly opisthogyrate, with widely spaced and pronounced commarginal ribs; remainder of exterior with closely spaced commarginal ribs; ribs weak or absent posterior to primary posterior ridge. Resilifer extending about half to full distance from beak to vmHP. Left anterior cardinal tooth narrow, wedge-shaped, inclined anteriorly 30–40°, extending to beak or nearly so. Left posterior cardinal tooth wedge-shaped, orthocline, extending to beak or nearly so. Receptor pit obsolete. Right anterior pseudocardinal tooth coalescent with lunule margin. Right cardinal tooth thick, wedge-shaped, inclined anteriorly 15−20°. Right posterior pseudocardinal tooth lamellar, diverging 30−60° from midpoint of cardinal tooth, passing resilifer ventrally. Inner ventral margin crenulate.

Remarks.—Specimens of Crassatella portelli exhibit characters of Crassatella (widely diverging right posterior pseudocardinal ridge, resilifer in some specimens not extending close to the vmHP, crenulate inner ventral margin) and Kalolophus and Hybolophus (flattened umbo, resilifer in some specimens reaching nearly to vmHP, left anterior cardinal tooth extending nearly to beak).

Stratigraphic and geographic range.— Lower Oligocene , Suwannee limestone, Florida .

Crassatella neorhynchus ( Olsson, 1931)

Fig. 6A− F, H .

1931 Crassatellites neorhynchus sp. nov.; Olsson 1931: 44, pl. 7: 8, 10. Type material: Holotype, articulated paired adult valves: PRI 1997 . Paratype: PRI 1995 from upper Eocene , Chira, Peru .

Type locality: Mancora , Peru .

Type horizon: Mancora Formation , lower Oligocene .

Material.— UWBM 101822, B8318, L (39.0), H 40.0, T 13.4; UWBM 101823, B8318, L (29.8), H 33.9, T 11.0; UWBM 101824, B8318, L 50.9, H 43.6, T 13.1; UWBM 101825, B8318, L (48.1), H (41.4), T 16.8; UWBM 101826, B8318, L 59.6, H 43.6; UWBM 101827, B8318, L 20.4, H 18.0, T 5.1; UWBM 101828, B8340, L 39.4, H 30.8, T 9.8; UWBM 101829, B8322, L 32.8, H 24.6, T 8.3; UWBM 101830, B8348, L (40.5); UWBM 101831, B8336, L 13.5, H 11.6, T 2.2; UWBM 101832, B8336, L 22.6, H 17.4, T 5.4; MUSM INV 203, B8318, L (38.0); MUSM INV 204, B8318, L (43.0), H (36.7), T 15.5; MUSM INV 205, B8318, L (48.6), H 40.0, T 13.2; MUSM INV 206, B8340, L 35.9, H 29.0, T 9.6; MUSM INV 207, B8348, L 44.9, H 35.0, T 13.2; MUSM INV 208, B8348, L 29.7, H 24.3, T 7.2; MUSM INV 209, B8336, L 13.8, H 10.8, T 2.2. Other specimens from B8327, B8331, B8339, B8346, B8347. All specimens from the East Pisco Basin, Peru.

Emended diagnosis.—Shell trapezoidal, inflated. Umbo rounded, with pronounced and well spaced commarginal ribs.

Description.—Shell to 60 mm long, trapezoidal, inflated, L:H ratio 1.3, T:H ratio 0.3−0.4, maximum inflation posterior to beak. Anteriodorsal and posteriodorsal profiles nearly straight, anterior margin sharply rounded, posterior margin broadly truncate, slightly produced in largest specimens; ventral margin evenly rounded or slightly angular. Weakly angular primary posterior ridge diverging 20−25° from posteriodorsal margin. Secondary posterior ridge obsolete. Lunule cordate, twice as wide as escutcheon; both longer than half the length of respective margins. Beak prosogyrate. Umbo rounded, prosogyrate, with pronounced commarginal ribs; ribs absent posterior to primary posterior ridge. Remainder of exterior with irregular commarginal growth lines. Resilifer extending about half way to vmHP. Left anterior cardinal tooth thick, wedge-shaped, inclined anteriorly 30°, separated from beak by lunule. Left posterior cardinal tooth wedge-shaped, inclined posteriorly 10°, extending from vmHP to beak. Receptor pit absent. Right anterior pseudocardinal tooth nearly coincident with margin of lunule. Right cardinal tooth thick, wedge-shaped, orthocline. Right posterior pseudocardinal tooth lamellar, diverging 35° from cardinal tooth, passing resilifer ventrally. Inner ventral margin crenulate on largest specimens.

Remarks.—External characters of East Pisco Basin specimens match those of the Talara Basin specimens; internal features of the latter are not visible. Large specimens are more elongate than inferred by Olsson (1931) ( Fig. 6A ).

The stratigraphic placement of Crassatella neorhynchus in Chira valley is unambiguous, although the accepted age of the Chira shales has changed from early Oligocene ( Olsson 1931) to late Eocene ( Higley 2004). The stratigraphic placement of C. neorhynchus near Mancora is less certain. The lower Oligocene Mancora Formation, cited by Olsson (1931) as the type horizon for C. neorhynchus , is not mapped near Mancora, despite being described from that stratotypic locality ( Palacios 1994). Olsson’s (1931) description of the area from which specimens of C. neorhynchus were collected corresponds to outcrop mapped as the upper Eocene Mirador Formation ( Palacios 1994).

Stratigraphic and geographic range.—Lutetian, basal Paracas depositional sequence, East Pisco Basin, south-central Peru. Upper Eocene, Chira and Mirador Formations, Talara Basin, northern Peru.

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.

Fig. 6. Crassatellid bivalves from the late Eocene of south-central Peru. A−F, H. Crassatella neorhynchus (Olsson, 1931), Paracas depositional sequence. A. UWBM 101826, exterior of left valve. B. MUSM INV 203, left hinge plate. C. MUSM INV 208, dorsal margin, anterior at right. D. MUSM INV 206, dorsal margin, anterior at right. E. UWBM 101828, exterior of left valve. F. UWBM 101823, interior of right valve. H. MUSM INV 212, exterior of left valve, juvenile. G. Crassatella pedroi sp. nov., UWBM 101833, holotype, Otuma depositional sequence; exterior of left (G1) and right (G2) valves, dorsal view of paired valves (G3), anterior at right. Scale bars 10 mm.