Minycardita capitanensis, Vendrasco, Michael J., Hoare, Richard D. & Bell, Gorden L., 2010

Vendrasco, Michael J., Hoare, Richard D. & Bell, Gorden L., 2010, The youngest rostroconch mollusc from North America, Minycardita capitanensis n. sp., Zootaxa 2603, pp. 61-64 : 62-64

Minycardita capitanensis n. sp.

( Fig. 1 )

Type material. Holotype ( GUMO 15309: Fig. 1 ), 5.03 x 2.51 x 3.13 mm (L x W x H).

Type locality. USGS 7663, Reef Trail Member of the Bell Canyon Formation, Texas, USA, 31˚49ʹ45ʺN, 104˚52ʹ18ʺW (Late Guadalupian, Permian).

Etymology. Named for the ancient Capitan Reef where this animal had lived.

Description. Small (5.1 mm long, including rostrum); body chamber swollen but with small flat region in middle of each side, curving with strong concavity into narrow rostrum with gently converging sides ( Fig. 1 C–D); primary carina rounded ( Fig. 1 B); rostral face shallowly concave, smooth ( Fig. 1 G); rostrum long with subcircular opening ( Fig. 1 G, I), parallel to hinge line; rostrum bordered by prominent rostral clefts ( Fig. 1 G, J); anterior snout much wider than rostrum, parallel-sided in dorsal view ( Fig. 1 C); anterior edge of snout deflected ventrally ( Fig. 1 A); anterior gape smooth-edged, tear-shaped, ventrally extending as narrowing denticulate opening into body ( Fig. 1 D–F); eight costae on body, nine costae on snout; anterior portion of snout without costae; two major and numerous fine comarginal growth lines on body and snout; protoconch ( Fig. 1 B) with small bulbous apex, rounded dorsally.

Differential diagnosis. Minycardita capitanensis n. sp. differs from the Wolfcampian M. sectilis , the type species and only other species in this genus, by having a more flat-sided body, greater concavity of posterior face (the region where posterior rostrum meets main body chamber), more horizontal rostrum (instead of one angled slightly downward as in M. sectilis ), and greater lateral tapering of body chamber to anterior gape, seen in dorsal view.

Distribution. Only known from type locality.

J. Hearst and F. Margaritondo picked and sorted the acidized concentrate from the locality. D. L. Geiger took the photographs. H. Chaney allowed the use of the SEM at the SBMNH. M. K. Nestell verified the fusulinid identification. C. Z. Fernandez provided advice on taxonomy and comments on an early draft. J. Pojeta, Jr. and an anonymous reviewer made numerous comments that greatly improved the paper. RDH acknowledges the continuing support of the Department of Geology, Bowling Green State University.

Figures

FIGURE 1. Holotype of Minycardita capitanensis n. sp., GUMO 15309. Images A – F were taken through the dissecting microscope, G – J via SEM. A, left-lateral view. B, right-lateral view. C, dorsal view. D, ventral view. E, anterior view. F, oblique-ventral view. G, posterior view. H, anterior view. I, dorsal view. J, postero-dorsal view. Scale bars 1 mm; scale bar for A – D is the same, in the middle of these four images.