Neocrassina californica ( Stanton, 1895 )

Kaim, Andrzej, Jenkins, Robert G., Tanabe, Kazushige & Kiel, Steffen, 2014, Mollusks from late Mesozoic seep deposits, chiefly in California, Zootaxa 3861 (5), pp. 401-440 : 429

Neocrassina californica ( Stanton, 1895)

( Fig. 15 )

Astarte californica Stanton, 1895 , p. 57, pl. 6, figs. 19–21.

Supplementary description. Escutcheon symmetrical, broad lanceolate, bounded by sharp ridge, commarginal sculpture of shell surface continues only faintly inside the escutcheon; lunule deep, lenticular, bounded by ridge; anterior adductor muscle scar oval in outline and most deeply impressed posteriorly; two thick cardinal teeth that radiate inward in left valve, one thick cardinal in right valve; posterior tooth elongate and well developed.

Material and occurrence. 4 specimens from Bear Creek (Valanginian, Early Cretaceous); Stanton’s (1895) type material from Cold Fork of Cottonwood Creek (Albian, Early Cretaceous) was also seen ( USNM 23053).

Remarks. Our four specimens from the Bear Creek site reach only 17 mm in length and are thus smaller than Stanton’s (1895) type specimens from CFCC. No additional specimens were found at CFCC during a visit in 2011. The genus Neocrassina was widely distributed during the Jurassic when it preferred fine to medium grained sands and thus middle shelf settings ( Gardner & Campbell 2002). Most Cretaceous records appear to be restricted to the northern Hemisphere [Siberia ( Saks 1975) and northern Japan ( Hayami 1975)]; although Chavan (1969) reports a range into the Turonian.

Figures

FIGURE 15. Neocrassina californica (Stanton, 1895) from Cretaceous seep carbonates in California. A, B. Specimen showing sharply delineated escutcheon, from the Valanginian of Bear Creek (GZG. INV. 85004). C, D. Specimens showing lunule, from Bear Creek (GZG. INV. 85005). E. Interior of a left valve, from Bear Creek (GZG. INV. 85006). F. Type specimen from CFCC (USNM 23053), note stronger ribbing than on the specimens from Bear Creek.