First Report of Fuxianospira from Cambrian North America

Reexamination of Yuknessia from the Cambrian of China and first report of Fuxianospira from North America

Authors:

LoDuca et al

Abstract:

Yuknessia Walcott, 1919 recently was transferred from the green algae to the Phylum Hemichordata on the basis of new details observed for the type species, Y. simplex, from the Burgess Shale Formation (Cambrian Stage 5) of British Columbia. This has prompted reexamination of material attributed to Yuknessia from various Cambrian localities in South China. Findings preclude both a Yuknessia and a hemichordate affinity for all of the Chinese study material, and most of this material is formally transferred to Fuxianospira Chen and Zhou, 1997, a taxon common in the Chengjiang biota. Comparable material from the Cambrian Marjum, Wheeler, and Burgess Shale formations of North America is also assigned to Fuxianospira, and this reassignment expands both the paleogeographic and stratigraphic range of this taxon. All aspects of the study specimens, including details obtained from scanning electron microscopy, are consistent with an algal affinity, as proposed in the original descriptions of the Chinese material.

Origin and Evolution of Hemichordata

Hemichordata (Pterobranchia, Enteropneusta) and the fossil record

Author:

1. Jörg Maletz (a)

Affiliation:

a. FU Berlin, Institut für Geologische Wissenschaften, Malteser Str. 74–100, Haus B 322, D- 12247 Berlin, Germany

Abstract:

The Hemichordata are generally interpreted as early deuterostomes, closely related to the chordates, a notion important for modern analyses of the origin of the deuterostomes. Because their fossil record is quite scanty, modern phylogenetic interpretations largely rely on analysis of DNA of the available extant taxa. The tripartite body plan of the group of worm-like hemichordates, the Enteropneusta, may be traced back in deep time to a few poorly known Middle Cambrian (Series 3, Stage 5) taxa from the Burgess Shale biota. The derived small, colonial or pseudocolonial Pterobranchia (Cephalodiscida and Graptolithina) have a more complete fossil record due to their preservable housing construction, the tubarium. The relationships of fossil taxa, putatively identified as early deuterostomes and possible hemichordates or even as pterobranchs of Lower to Middle Cambrian age (e.g. Galeaplumosus, Herpetogaster), cannot be substantiated. The Pterobranchia and their housing construction is first seen in the Middle Cambrian Series 3, Stage 5 but a clonal, colonial organization of the tubaria can only be recognized in the basal Drumian. The fossil enteropneust Mazoglossus ramsdelli Bardack, 1997 from the Carboniferous Mazon Creek Biota is re-described, its lectotype designated and illustrated for the first time.