Mickwitzia
Encyclopedia
Mickwitzia is a genus
of stem group brachiopods with punctate shells from the Cambrian
period. Mickwitziid shells are composed of apatite (calcium phosphate). Punctae or tubes penetrate through multiple shell wall layers, and individual punctae often develop a single, axial phosphatic tube. Members of the genus appear to share characteristic shell microstructure in common with halkieriids such as Micrina, and like the halkieriids, mickwitziids may not have been able to enclose their entire body within a bivalved shell. As such, mickwitziids represent a potentially critical intermediate fossil taxon linking Phylum Brachiopoda to another animal phylum, with both higher taxa appearing rather suddenly near the beginning of the Cambrian. The origins and functions of the tubes that penetrate mickwitziid shells are controversial. One hypothesis considers the tubes to represent marginal setae that became surrounded by phosphatic shell material. Another hypothesis suggests that the tubes represent conduits for the delivery of anti-predation or anti-fouling toxins to the shell surface. The two hypotheses are not necessarily mutually exclusive.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of stem group brachiopods with punctate shells from the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
period. Mickwitziid shells are composed of apatite (calcium phosphate). Punctae or tubes penetrate through multiple shell wall layers, and individual punctae often develop a single, axial phosphatic tube. Members of the genus appear to share characteristic shell microstructure in common with halkieriids such as Micrina, and like the halkieriids, mickwitziids may not have been able to enclose their entire body within a bivalved shell. As such, mickwitziids represent a potentially critical intermediate fossil taxon linking Phylum Brachiopoda to another animal phylum, with both higher taxa appearing rather suddenly near the beginning of the Cambrian. The origins and functions of the tubes that penetrate mickwitziid shells are controversial. One hypothesis considers the tubes to represent marginal setae that became surrounded by phosphatic shell material. Another hypothesis suggests that the tubes represent conduits for the delivery of anti-predation or anti-fouling toxins to the shell surface. The two hypotheses are not necessarily mutually exclusive.