The Scleritome of 'Eccentrotheca' from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny

Title
The Scleritome of 'Eccentrotheca' from the Lower Cambrian of South Australia: Lophophorate affinities and implications for tommotiid phylogeny
Publication Date
2008
Author(s)
Skovsted, CB
Brock, GA
Paterson, John Richard
( author )
OrcID: https://orcid.org/0000-0003-2947-3912
Email: jpater20@une.edu.au
UNE Id une-id:jpater20
Holmer, LE
Budd, G
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Geological Society of America
Place of publication
United States of America
DOI
10.1130/G24385A.1
UNE publication id
une:1648
Abstract
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 'Eccentrotheca' 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.
Link
Citation
Geology, 36(2), p. 171-174
ISSN
1943-2682
0091-7613
Start page
171
End page
174

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