Leionucula gabbi ( 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 : 424-425

Leionucula gabbi ( Stanton, 1895)

( Fig. 12 )

1895 Nucula gabbi Stanton , p. 51–52, pl. 6, figs. 11, 12. 1961 Nucula gabbi Stanton, Chandler & Axelrod , p. 442.

Material and occurrence. Two specimens from Paskenta (Tithonian, Late Jurassic). Stanton’s (1895) type material ( USNM 23047) is also from Paskenta and consists of two specimens: one has been illustrated and the other has been cut along the hinge area and shows taxodont dentition.

Remarks. One of the specimens illustrated here ( Fig. 12 ) shows two slightly oval adductor muscle scars and a well-developed, uninterrupted pallial line, features not illustrated by Stanton. ‘ Nucula ’ gabbi is characterized by a smooth surface except for blunt irregular growth lines and a non-crenulated inner margin, and is therefore transferred to Leionucula . The species has been mentioned by Chandler & Axelrod (1961) from Hauterivian strata of the Ono area, in the vicinity of the Eagle Creek seep locality.

As mentioned by Stanton, N. solitaria Gabb 1869 differs by having widely spaced strong commarginal ribs with fine striae in between, but he also noted that the figure of N. solitaria given by Whiteaves (1884, p. 232, pl. 31, fig. 3) from Queen Charlotte Island, Canada, is quite similar to Leionucula gabbi , which, judging from Whiteaves figure, is indeed the case. The Cenomanian species Nucula maedinga Stilwell & Henderson, 2002 from northern Australia differs by having a fine, beaded, undulating sculpture ( Stilwell & Henderson 2002).

Figures

FIGURE 12. Leionucula gabbi (Stanton, 1895) from Tithonian seep carbonates of Paskenta. A, B. Specimen showing external sculpture and escutcheon (GZG. INV. 84998). C. Internal mold showing pallial line and adductor muscle scars (GZG. INV. 84999).