Hyoliths and small shelly fossils from the Lower of North−East Greenland

JOHN M. MALINKY and CHRISTIAN B. SKOVSTED

Malinky, J.M. and Skovsted, C.B. 2004. Hyoliths and small shelly fossils from the Lower Cambrian of North−East Green− land. Acta Palaeontologica Polonica 49 (4): 551–578.

The hyolith assemblage from the Lower Cambrian Bastion Formation of North−East Greenland is significant in that it contains several hyolith taxa that possess traits of both orders and Orthothecida. They possess morphological traits that seem to be characteristic of the ancestral forms of both groups. In addition, many hyolith taxa from this interval are globally distributed, supporting the notion that these fossils have potential as stratigraphic indicators. This assemblage contains genera and/or species seen in Australia, North America, the Siberian Platform, and South China. Hyoliths identi− fied include the hyolithids Parkula bounites, Hyptiotheca karraculum, Microcornus eximius, M. petilus, Paracornus poulseni gen. et sp. nov., as well as Similotheca similis?, S. bastionensis sp. nov., and S. groenlandica sp. nov.; two opercula remain in open nomenclature. Orthothecids from this assemblage are one unnamed species each of Contitheca and Gracilitheca. Large, macro−sized hyoliths from the same formation described by Poulsen (1932) are mostly unidenti− fiable, although an operculum formerly identified as Hyolithes () communis is reassigned to Hyptiotheca. Problematic organisms of uncertain affinity include Cupitheca holocyclata, australiensis, an unnamed spe− cies of Coleolus, and the cap−shaped Cassitella baculata gen. et sp. nov. that may be an operculum of some as yet un− known organism. Missarzhevsky (1969) used Hyolithes (Orthotheca) bayonet var. groelandicus and H.(O.) bayonet var. longus as the basis for Lenatheca, but the specimens on which that genus is based are too poorly known for a proper diagnosis of Lenatheca.

Key words: , Hyolithida, Orthothecida, Botomian, Lower Cambrian, Bastion Formation, Greenland.

John M. Malinky [[email protected]], Geologisch−Paläontologishes Institut, Ruprecht−Karls Universität, Im Neuenheimer Feld, 234, D−69120, Heidelberg, Germany; Christian B. Skovsted [[email protected]], Uppsala University, Department of Earth Science, Program for Palaeobiology, Norbyvägen 22, SE−752 36 Uppsala, Sweden.

Introduction dards. In contrast, the majority of the newly discovered speci− mens from Greenland are much better preserved. The purpose Hyoliths have long been recognized as a component of faunal of this work is to evaluate all hyolith specimens from the Bas− assemblages from the Lower Cambrian of North−East Green− tion Formation of Greenland for taxonomic purposes and then land. Poulsen (1932) described six species represented by integrate them into current taxonomic, geographic, and strati− twelve specimens from the Bastion Formation, and recent dis− graphic frameworks. coveries of micro−sized individuals from acid resistant resi− The hyolith fauna of the Bastion Formation is unique in dues from the same unit have substantially increased the num− several respects. Certain taxa, such as Hyptiotheca Bengtson, ber of specimens known. Poulsen’s (1932) specimens have 1990a and opercula A and B, possess traits characteristic of not been revised until now, nor were they integrated into the both the orders Hyolithida and Orthothecida. In the case of newly emerging taxonomic system in Russia in the late 1950s Hyptiotheca, clavicles on the interior of the operculum are and early 1960s (Syssoiev 1958, 1962). Most specimens are absent, making this the only hyolithid species known to lack incompletely preserved, and the taxa they represent cannot be this feature. Opercu