The scleritome of Eccentrotheca from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny
2008 (English)In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 36, no 2, 171-174 p.Article in journal (Refereed) Published
The first partially articulated scleritome of a tommotiid, Eccentrotheca sp., is described from the Lower Cambrian of South Australia. The Eccentrotheca scleritome consists of individual sclerites; fused in a spiral arrangement, forming a tapering tube-shaped skeleton with an inclined apical aperture and a circular to subcircular cross section. Traditionally, tommotiid sclerites have been assumed to form a dorsal armor of imbricating phosphatic plates in slug-like bilaterians, analogous to the calcareous sclerites of halkieriids. The structure of the Eceentrotheca scleritome is here reinterpreted as a tube composed of independent, irregularly shaped sclerites growing by basal-marginal accretion that were successively fused to form a rigid, protective tubular structure. The asymmetrical shape and sometimes acute inclination of the apical aperture suggests that the apical part of the scleritome was cemented to a hard surface via a basal disc, from which it projected vertically. Rather than being a vagrant member of the benthos, Eccentrotheca most likely represented a sessile, vermiform filter feeder. The new data suggest that the affinities of Eccentrotheca, and possibly some other problematic tommotiids, lie with the lophophorates (i.e., the phoronids and brachiopods), a clade that also possesses a phosphatic shell chemistry and a sessile life habit.
Place, publisher, year, edition, pages
2008. Vol. 36, no 2, 171-174 p.
tommotiida, phylogeny, Brachiopoda, Phoronida, Lower Cambrian
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:uu:diva-17769DOI: 10.1130/G24385A.1ISI: 000252829600019OAI: oai:DiVA.org:uu-17769DiVA: diva2:45540