Hoffmann, J.; Lüter, C. (2010). Shell development in the thecidellinine brachiopods with description of a new recent genus. Special Papers in Palaeontology. 84: 137-160.

156504

Hoffmann, J.; Lüter, C.

2010

84: 137-160

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A description of a new thecidellinine genus, Minutella gen. nov., with two new species, M. tristani sp. nov. and M. bruntoni sp. nov., from the Caribbean region is provided. Representatives of the new genus are characterized by a very small body size and were previously thought to be juveniles of Thecidellina. Reinvestigations of specimens from the Indian Ocean described as Thecidellina minuta resulted in their redescription as Minutella minuta. One of the main differences between Minutella and Thecidellina is the presence of a well-defined pseudodeltidium in Minutella similar to that of the Lacazellinae, whereas in Thecidellina a pseudodeltidium has never been observed either in adults or in juvenile stages. Furthermore, the ontogenetic series of five different species of Thecidellina from the Atlantic and Pacific Ocean revealed interspecific differences in shell development, which do not correspond with biogeography. We could identify different clades of shell ontogeny, i.e. the ‘congregata’-clade, represented by the species T. congregata (Pacific), T. bahamiensis (Caribbean) and T. williamsi (Atlantic), the ‘japonica’-clade, represented by T. japonica (Pacific) and the ‘meyeri’-clade, represented by T. meyeri (Caribbean). All three clades differ significantly in important details of their shell development, the visceral gap complex and the cardinal region. In some cases, similar adult morphologies may be caused by convergence, but usually they suggest common ancestry within a single clade. Thus, taxonomical studies of thecideide brachiopods should include investigations of ontogenetic series or juvenile stages.

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