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An impression of Aparimella apteryx (LPC6_91) from Highfield Farm
The genus Halobia is relatively abundant in the Triassic in New Zealand, and represented by as many as eight species all found in either the Oretian or Otamitan stages. They share the same family (Pteriidae) as the Kaihikuan bivalve Aparimella apteryx, with which they have some similarities. Several of the species have been widely reported in the Nelson area: the Fossil Record Electronic Database, maintained by GNS, includes records from at least 25 localities for the species H. lilliei, and more than 20 for H. hochstetteri.
Given that, it's surprising that I have very few specimens in the collection. While it's possible that they've been overlooked during fieldwork, the more likely explanation is that that are locally almost absent from Highfield Farm. The few I have found have been recovered from Oretian or Oramitan deposits, and seem to belong to the species Halobia (Z) hochstetteri (the 'Z' referring to the alternate species, Zittelihalobia, to which it seems to be related). Apart from the age, a defining of the species is the wavy shape of the radials in the mid-area of the shell, which helps to distinguish it from Aparimella apteryx. A detailed description of the species, by Trechmann (1917) is given to the right. |
Halobia (Z) hochstetteri
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Further Reading:
Marwick, J. 1953 Divisions and faunas of the Hokonui System (Triassic and Jurassic). Paleontological Bulletin 21, Wellington: New Zealand Geological Survey.
Trechmann, C.T. 1917 The Trias of New Zealand. Quarterly Journal of the Geological Society 291, 165-246 (+ 10 plates).
Marwick, J. 1953 Divisions and faunas of the Hokonui System (Triassic and Jurassic). Paleontological Bulletin 21, Wellington: New Zealand Geological Survey.
Trechmann, C.T. 1917 The Trias of New Zealand. Quarterly Journal of the Geological Society 291, 165-246 (+ 10 plates).