早白垩世掘足类Dentalium属在我国首次发现

DISCOVERY OF DENTALIUM(DENTALIIDAE, SCAPHOPODA) FROM LOWER CRETACEOUS OF GUCUO VILLAGE,NYALAM, SOUTHERN XIZANG (TIBET)

本文记述的掘足类(Scaphopods)系我国首次报道,化石产自西藏南部聂拉木县古错村北山下白垩统古错Ⅱ组中。计1属2种Dentalium jeffereysi Gardner,D.gucuoensis(sp.nov.).

<ABSTRACT> The Cretaceous scaphopods described in the paper were found for the first time from the lower Cretaceous Gucuo II Formation near Gucuo village of Nyalam county, southern Xizang. They include Dentalium jeffereysi Gardner, D. gucuoensis ( sp.nov. ), occurred in greyish white calcareous silty mudstone. Dentalium gucuoensis( sp. nov.) Shell cylindrical, tapering, with greatest diameter at aperture; large and elongate, moderately curved, with a long slit on the ventral face; surface smooth, its anterior part marked in places by irregular growth lines; having a length of 33~88 mm and a width of 5~ 9 mm, at aperture. Comparison This species differs from D. decussatum J. Sowerby in lacking longitidinal ribs and from D. cylindricumJ. Sowerby by having a large and moderately tapering shell. Horizon and Locality Lower Cretaceous Gucuo II Formation; Gucuo village, Nyalam, southern Xizang.