The whales of Chuckatuck, Part 2

As I mentioned last week, we’ve only recovered two whale bones from the incredibly rich Yorktown Formation shell beds found at Chuckatuck, Virginia. The second bone, a fairly large baleen whale radius (one of the fore arm bones) is shown above. But what’s that big blob near the distal end, on the lower left in the picture?

If we zoom in on that area, we can see some of the details of the blob:

The blob is a colony of encrusting bryozoans. Bryozoans are a group of filter-feeding invertebrates of rather mysterious origins and relationships. Most of them produce mineralized calcium carbonate skeletons, and they’re well known from Paleozoic rocks when there were numerous reef-building forms. In the Neogene most fossil bryozoans are encrusting forms like the one shown here. These are ridiculously common at Chuckatuck, with many of the snail shells found there completely encrusted (there are also a few small patches on last week’s vertebra). It appears, however, that this bone has no barnacles attached at all, unlike the whale vertebra from the same quarry.

As an aside, the bone itself is also rather interesting. In terms of shape, it’s actually pretty similar to the modern bowhead whale, Balaena mysticetus. However, it’s not an especially good match for the fossil bowhead whale that actually occurs in the Yorktown Formation, Balaena ricei. It seems to be too large to represent Balaenula or a cetotheriid, and seems to have the wrong proportions for a balaenopterid. So I guess it represents a large balaenid, but I’m not completely convinced that it comes from Balaena ricei.

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