Triassurella goederti, Kiel & Campbell & Gaillard, 2010

Kiel, Steffen, Campbell, Kathleen A. & Gaillard, Christian, 2010, New and little known mollusks from ancient chemosynthetic environments, Zootaxa 2390 (1), pp. 26-48 : 28

Triassurella goederti sp. nov.

( Fig 1 )

Diagnosis: Strongly asymmetrical limpet-shaped shell with mainly spiral sculpture; slit positioned at whorl shoulder, slit margins not raised, and fused or nearly fused at aperture.

Holotype: USNM 538733 , 2.6 mm maximum diameter.

Paratypes: USNM 538734 , 3.5 mm maximum diameter ; USNM 538735 , 1.6 mm maximum diameter .

Type locality: The Bear Creek seep site, California, USA, 39°03'14"N, 122°24'40" W; Crack Canyon formation of the Great Valley Group; Early Cretaceous, Valanginian (Kiel et al. 2008) .

Description: Shell of strongly asymmetrical limpet shape, little more than half a rapidly expanding whorl, sculpturemainly spiral; upper side of whorl slightly convex, spiral ornament stronger near coiling axis and shoulder than in central part of whorl; at aperture eight spirals near coiling axis, at least seven near shoulder; slit situated at whorl’s shoulder, starting after approximately a quarter whorl, reaching greatest width about 1/ 8 whorl before aperture in mature specimens, slit closed (fused) or nearly closed at aperture; outer and lower part of whorl convex, sculptured by at least 11 spirals of subequal strength and spacing.

Remarks: The type species Triassurella carnica has the same general shape and also has spiral sculpture as Triassurella goederti , but the spirals are broader than in Triassurella goederti and the slit does not close at the aperture ( Nützel and Geiger 2006). Triassurella goederti resembles Sutilizona theca in its shell shape and slit morphology, but differs from it by having mainly spiral sculpture; Sutilizona theca has mainly radial sculpture ( McLean 1989). Also similar regarding shell shape and sculpture is Temnocinclis euripes McLean, 1989 from the Juan de Fuca Ridge vent fields but that species and genus has raised slit margins, which are lacking in Triassurella goederti , and T. euripes has a more elongate shell ( McLean 1989).

Distribution: Type locality only.

Etymology: For James L. Goedert, Wauna, Washington, who collected and provided the specimens.

Figures

FIGURE 1. Triassurella goederti n. sp. from Early Cretaceous seep carbonates in California, USA. A-C. Holotype (USNM 538733) with preserved shell material; note detail of sculpture on whorl’s flank (C). D, E. Paratype (USNM 538735), internal mold of juvenile specimen showing onset of slit. F. Paratype (USNM 538734), steinkern showing the slit as it widens abruptly and then tapers towards the aperture.