REVISITING THE AGE OF GREENLAND’S CRETACEOUS CONTINENTAL MOLLUSKS

Continental fossil mollusks discussed here are from West Greenland’s northern Nûgssuaq Peninsula. T.W. Stanton (USGS; in White and Schuchert, 1898) identified "one or possibly two species of Unio, an Anodonta(?), a Sphaerium, and two species of gasteropods [sic]." He stated the "few fossils from Ujarartorsuak ... appear to be all fresh-water forms ... [that] might occur in the Upper Cretaceous, [but] more probable ... from Tertiary beds. Nebraska Territory fossils were similarly first reported by Rogers et al. (1845), from the 1843 Harris and Audubon expedition to the Yellowstone-Missouri River confluence. A few aquatic pulmonates and Anodonta? were interpreted as representing a "widely diffused freshwater formation" of Tertiary age.

A loan to J.T-C Yen (Villanova University; formerly USGS) from GEUS, Copenhagen, included specimens collected by J.P.J Ravn (in 1909), A.E. Bretting (in 1920), and 1938-1939 Danske Nûgssuaq Ekspeditioner. Yen's study did not include the specimens reported by Stanton. Yen’s paper received remarkably little notice. Yen excluded a review of specimens from available localities that he believed too ambiguously known. Seven discrete localities are delimited here from the Nûgssuaq Peninsula and Disko Island.

Yen (1958) named new species of Sphaerium, Corbula, Mesoneritina, and Lioplacodes, and noted unnamed "Unio, Anodonta, Lioplacodes, and Goniobasis(?)" taxa. All were presumed to be from location “shale bed I” after Sorgenfrei and Troelsen (unpublished), and “identical with the Unit C of White and Schuchert." Yen concluded that the fossils are younger than the "Atane series and most probably...Post-Cenomanian." Yen stated they "may be close to the age of the Judith River formation” [Campanian].

As Yen's new taxa are currently of little value in determining faunal age, other criteria are necessary. Yen's "shale bed I" is interpreted here as from the fluvial Ravn Kløft Member of the Atane Formation, considered lower Cenomanian (Henriksen et al., 2009; Pedersen et al. (2006), Dam et al. (2009), and Grimsson & Grimm, 2016). Other specimens (not reviewed by Yen) may be ascribed to overlying delta plain sediments of the Kinittoq Member.

Arden Roy Bashforth and Laura Jane Cotton, Invertebrate Palaeontology (Types), Natural History Museum of Denmark, University of Copenhagen, graciously permitted a loan of Greenland continental molluscan fossils.