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Schizotreta sp. from the Waitahu Valley, Reefton
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Lingulidiscina ranfti
Phylum: Brachiopoda
Superfamily: Linguloidea Genus: Lingulidiscina Species: Lingulidiscina ranfti Location found: Reefton |
Some of the most unusual and exciting finds from the Devonian of the Reefton area are these two specimens, one (above) from the Waitahu Valley and the other (right) from Stony Creek. Both appear to be members of the Linguloidea superfamily - lingulate brachiopods which represent some of the earliest brachiopods to evolve. In New Zealand,the Linguloidea were relatively abundant during the Cambrian, but then all but died out, so that in the Ordovician and Devonian they were scarce. They retained simple often cone-shaped forms, and some lived communally - as their modern relatives (which have been found in Fiordland, for example) still do today.
Identifying members of the superfamily is difficult for several reasons. Many genera show marked variations in form as they age, from larval to adult stage - so a number of specimens from different growth stages are needed to classify them with any certainty. The Linguloidea are also rather simple organisms, and differences between the various genera that have been identified are subtle - e.g. relating to small variations in the profile or the position of the apex of the shell. Again, without comparative material, this makes classification problematic. Partly for these reasons, previous classifications have often been uncertain and highly contested, and numerous names have been introduced, then discarded (and sometimes later revived), so choosing the correct and current name can be challenging. In nearby areas in New Zealand, specimens very much like this one (though from Ordovician deposits) have been assigned by Percival and colleagues to the genus Schizotreta. From the Devonian, however, the only report of similar occurrences is by Allan (1945), who gives the name Lingulidiscina ranfti, and this identification has been approved, albeit with a slight change in spelling to Lingulodiscina, by the National Biodiversity Inventory. Nevertheless, other authors, such as Girty (1928) have argued that Lingulodiscina and Schizotreta are the same, as is the genus Orbiculoidea. Guided by Paul Scofield, from Canterbury Museum, I have settled on the name (and spelling) originally given by Allan: i.e. Lingulidiscina ranfti. But given the uncertainties about both identification and naming, doubts remain. |
Schizotreta attached to a Reeftonella from Stony Creek, Reefton
Further Reading: Allan, R.S. 1945 Palaeozoic and Mesozoic brachiopod faunas in New Zealand: with an index to the genera and species. Transactions of the Royal Society of New Zealand 75 (1), 1-22. Girty, G.H. 1928 The generic name Orbiculoidea d'Orbigny and its application. Journal of the Washington Academy of Sciences 18 (5),128-142. Percival, I.G. et al. 2011 Middle Ordovician linguliformean brachiopods from the Maruia-Springs Junction area, New Zealand. Memoirs of the Association of Australasian Palaeontologists 42, 459-492. Williams, A. et al. 2000 Linguliformea, In: Treatise on invertebrate paleontology, Part H (Brachiopoda revised), vol. 2 (ed. R. L. Kaesler), Lawrence, KS: University of Kansas, pp 30-146. |