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Spiriferina novoseelandica (LPC20_276) from apparent Oretian rocks at Highfield Farm.
SpirifIda are common fossils in the Triassic of the Nelson area, and also elsewhere in New Zealand. They are distinguished by their deep sulcus, long straight hingeline, strong ribbing and markedly plicated (wavy) commisure (i.e. the lip where the shells meet). The order comprises several widely found Triassic genera, including Alipunctifera, Mentzelia, Mentzeliopsis, Psioidiella, Rastelligera and Spirefina, each containing several species.
The genus Spiriferina includes at least five species (plus others yet to be firmly classified), of which two are represented in the collection. The more abundant of the two species is Spiriferina novoseelandica, which has yielded twenty specimens to date (see gallery of specimens below). This species has previously been classified under a range of different names, including Retzia novo-seelandica and Spiriferina nelsonensis. There has also been some confusion in the past with what is now referred to as Psioidea australis. A description of the species by Trechmann (1917), as S. nelsonensis, is shown to the right. All the specimens attributed to S. novoseelanidica derive from Highfield Farm and were found in a narow zone of rocks believed from their distribution and fossil assemblage to be Oretian in age. As such, this identification poses a problem. In the national Biodiversity Inventory, S. novoseelandica is described as being restricted to the Otamitan stage. The finds thus raise the question of whether the identification is at fault (which is possible) or whether the species appeared earlier in the Triassic than previously inferred. If the identification is wrong, the most likely candidate for a name might be S. abichi, which is reported as occurring in the Oretian. More intriguing, though, is the possibility that the species crosses the Oretian-Otamitan boundary in New Zealand. More work is needed to investigate these possibilities. One additional specimen has been found in Highfield Farm, close to the faulted border between Oretian/Otamitan and Kaihikuan strata (image right). This has very tentatively been attributed to S. carolinae, a species reported from the Kaihikuan stage in the past. Until more, and better, speciemns are found, however, this identification must remain uncertain. |
Spiriferina sp.
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Further Reading:
Trechmann, C.T. 1917 The Trias of New Zealand. Quarterly Journal of the Geological Society 291, 165-246 (+ 10 plates).
Trechmann, C.T. 1917 The Trias of New Zealand. Quarterly Journal of the Geological Society 291, 165-246 (+ 10 plates).