Sunday, October 13, 2013

Reconstructing the skull of Neophoca palatina: a fossil relative of the Australian sea lion from the Pleistocene of New Zealand

When Morgan Churchill visited Dunedin for his EAPSI fellowship in July and August, we secured a loan of the holotype skull of Neophoca palatina for study and repair. Judith King published her study of the specimen and named it in 1983, and returned it to New Zealand by mail; unfortunately, it was damaged in transit. Part of this is likely due to uneven acid preparation of the specimen; a thin, horizontal zone of calcareous sediment was totally dissolved away, including through the turbinates - leaving the palate and braincase connected only by thin, vertical sheets of the maxilla - which fragmented into many small pieces.

Our first stab at putting humpty dumpty back together. The brown skull is a cast of the type specimen, with a modern Phocarctos skull for comparison.

After Morgan returned from Australia and the North Island, he hand carried the type skull back to Dunedin. At this stage, the holotype consisted of a fragmentary palate and a mostly complete braincase, and many fragments of the dorsal part of the rostrum and posterior palate.

The holotype braincase of Neophoca palatina (bottom), a cast of the holotype (left), and an Arctocephalus skull (right).

The remains of the Neophoca palatina holotype; the palatal fragment is dorsal up, and the braincase is ventral up.

Some matches already! Here's the palate in ventral view.

Within minutes of opening up all of the bags and unwrapping the fragments, we started to see some obvious joins - and started gluing right away. Within the first few days of Morgan returning, we had the majority of the bone fragments glued back in place.

Morgan sorts through skull fragments in the paleo lab.

Morgan sorting through more fragments...

So there were lots and lots of fragments...

All the king's horses and all the king's men couldn't put [Neophoca palatina] back together again.

At present, the majority of pieces have been glued back together, but remain in separate sections; Ewan suggested that we not proceed with gluing the final pieces back on until we get some good photographs of the skull pieces prior to reassembly, so that we can document the dorsal surface of the palate, and ventral surface of the broken intertemporal region - which will not be accessible once the skull is reassembled. Granted, prior to breakage, these surfaces were not visible - but, since we have the opportunity to document morphology that would otherwise be inaccessible - it is best to carefully document what we can. Similarly, recently the rostrum of the type cranium of the dolphin Waipatia was broken - so Ewan took the opportunity to photograph the broken cross section prior to gluing it back on. In another specimen - one of my eomysticetid specimens I'm studying for my dissertation - the mandible is fragmented into four pieces, and I'd like to photograph each broken surface before I reassemble it.

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