A New Family of Arcestaceae from East Timor, Indonesia




Allen, Jena J.

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A collection of 15 Ammonoidea specimens were recovered from eastern Timor, Indonesia. The strata for which the specimens collected were dated as the mid-Triassic, and the samples were originally classified as Joannites of the Triassic. However, upon further examination it became apparent that the specimens more closely resembled Cyclolobidea of the Permian. The Cyclolobidea were thought to have gone extinct well before the Permian Mass Extinction event, so for these specimens to be discovered in Triassic-aged rock has some interesting implications.

The specimens in question are described and categorized, with sutures being drawn for each specimen where possible. Once fully analyzed, the data is compared to various hypotheses to derive the most likely explanation for these unusual specimens. The original hypothesis was that Timor acted as a refugia during the Permian-Triassic boundary, creating a safe-haven where Cyclolobidea and their resulting descendants could continue to live into the Mesozoic. However, further research has led to more likely possibilities: they could be a new taxon entirely, unrelated to Cyclolobidea; or perhaps a currently undescribed taxon that demonstrates homologous structures to cyclolobids.


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Allen, Ammonoids, Arcestaceae, Indonesia, New Family, Timor