Cuspidaria

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 : 431-432

Cuspidaria ? persulcata ( Stanton, 1895)

( Fig. 18 )

Corbula ? persulcata Stanton, 1895, p. 61–62, pl. 11, fig. 3.

Material and occurrence. One specimen from the Tithonian, Late Jurassic of Paskenta (type locality).

Remarks. Stanton’s holotype (USNM 23061) is posteriorly more elongate than our specimen but has the same distant concentric furrows which end at the posterior truncation ( Fig. 18 ). Only the external surface of a right valve is available to us, thus a generic placement is difficult. Cuspidariidae produce very similar shells, including certain species of Cuspidaria Nardo 1840 and Myonera Dall 1886 (i.e., Poutiers & Bernard 1995).

Starting from the careful examination of the Jurassic ‘ Cuspidaria ’ ibbetsoni, Harper et al. (2003) suggested that many alleged pre-Cretaceous cuspidariids may in fact be corbulids, especially those occurring in brackish environments. Regarding Cuspidaria ? persulcata from the Paskenta seep locality we suggest the reverse: the species was initially assigned to Corbula (although hesitantly) and is, in our view, more likely a cuspidariid. Although this classification is based on external shell morphology only, the specimen is from a deep-water environment as are most extant species, and its Tithonian age is just slightly older than that of its sister taxa, the Verticordiidae and Poromyidae ( Harper et al. 2003) .

Figures

FIGURE 18. Cuspidaria? persulcata (Stanton, 1895) from Tithonian seep carbonates of Paskenta, California. A. Right valve (GZG. INV. 85010). B. Holotype, left valve (USNM 23061).