Dacrycarpoides, a new genus of extinct Podocarpaceae (Coniferales) from the early Miocene of New Caledonia

Premise

The archipelago of New Caledonia contains one of the world's most distinctive biotas. The presence of notable paleoendemics in this biota suggests that Gondwanan vicariance may have played an important role in its formation, but geological evidence indicates that New Caledonia was submerged until the Oligocene and that its flora formed from more recent long-distance dispersal events. The lack of a fossil record contributes to uncertainties inherent in both interpretations, but newly discovered fossil plant assemblages may help clarify the origins of the New Caledonian flora.

Methods

We used standard paleobotanical techniques to prepare and describe leafy conifer shoots from an early Miocene deposit (age ~19 Ma) on the Pindaï Peninsula of western New Caledonia. To determine affinities of the fossil material, we compared it to herbarium collections of extant New Caledonian conifers and the broader macrofossil record.

Results

Fossil leaves contain cellular-level details of leaf morphology and epidermis anatomy consistent with the conifer family Podocarpaceae, in particular the extant genus Dacrycarpus. However, stomata in the fossils are arranged in crowded complexes unlike those of any described Podocarpaceae taxon, and therefore we assign this material to a new extinct genus: Dacrycarpoides.

Conclusions

New Caledonia is a hotspot of modern conifer biodiversity and was home to now extinct lineages as well. The presence of extinct conifers on Miocene New Caledonia is consistent with floras from neighboring landmasses and highlights the role of extinction in shaping the modern flora of New Caledonia and other Australasian landmasses.