Monday, August 27, 2012

Field work in South Canterbury

Late last week I went with Ewan, fellow student C. H. Tsai, and fossil preparator Sophie White on a day trip to North Canterbury, to one of Ewan's most productive fossil localities in the Otekaike Limestone. We got up early and packed the department vehicle and trailer with all manner of equipment, including the masonry saw and the equipment Ewan Fordyce is famous for within paleontological circles - a chainsaw. The rock is so soft that it can be sawn through with a chainsaw fitted with a diamond-dust coated chain, which Ewan estimates has cut the amount of time needed for digging by 70% or so. Unfortuantely I don't have any photos of the fieldwork, as I left my camera at home. It turned out that we were so damn busy I wouldn't have had time to take many photos anyway.

There has been quite a bit of rain here on the South Island over the past few weeks, and Ewan had planned on making a trip up there anyway - just not so soon, as he wanted to wait for some even drier weather. Upon arriving at the quarry, we found a few bits of bone here and there, but at first, nothing too promising.

One fossil included both mandibles of a medium-sized baleen whale (est. 2 meter skull length?), and will require a large jacket, at least 1.5 m long. I found a probable odontocete mandible (probably not very complete), and a couple of bird bones. One specimen that I poked around at initially looked like an odontocete rib, but very quickly turned into a disarticulated penguin skeleton. This is probably not something like the recently described penguin Kairuku - which is well known from the older, underlying formation called the Kokoamu Greensand - but, according to Ewan, may turn out to be Platydyptes novaezealandiae, which is well known from the Otekaike Limestone.

The most exciting find of the day started out not very promising at all: a cluster of dolphin ribs and vertebrae. Sophie started cleaning it up and uncovered a nearly complete radius. I developed a pretty solid headache and as a result was working fairly slowly, but helped Sophie as best I could with the dolphin. After a while she uncovered a weird, large, conical element, and asked me what I thought it was; after a little more exposure, it was very clearly the rostrum of a medium-sized odontocete (something about the size of modern Tursiops). After a bit more cleaning, Sophie found the vomer and internal choanae, the squamosal, and a paroccipital process (exoccipital bone): they were in place, and indicated that the entire skull is present. This was very exciting; there is a large assemblage of odontocetes from the Otekaike, including a large squalodont, small tusked dalpiazinids, a squalodelphinid (labmate Yoshi Tanaka is working on these), Notocetus marplesi (considered by Fordyce (1994) to be a Waipatiid), the strange and beautifully preserved dolphin Waipatia, and a smattering of other very strange and incompletely known (but tantalizing...) taxa I won't talk about any further. The weirdest part about this dolphin was the rostrum: it was very short, and apparently toothless. The skeleton includes the skull, a mandible, radius, many vertebrae and ribs, and a scapula.

We finished the day off by excavating everything but the block with the dolphin and the baleen whale; we would have to return later to excavate those. We left with a half dozen small blocks and two plaster jackets (the penguin skeleton and another partial dolphin). At the moment, Ewan is getting ready to return to the field (tomorrow), with Tsai, Yoshi, and Sophie; over the weekend, I started getting some strange rashes caused by a chicken pox-like virus, and won't really be able to make it out into the field with them, unfortunately.

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