Whale Falls In the Fossil Record

Whales are fascinating creatures. We have a good fossil record for them ranging from their land living ancestors to early baleen species. One species of Delphinidae (cousins to the whales) are even considered to be culture bearing (I am referring, of course, to killer whales). They are equally interesting for what happens when they die and fall to the ocean floor. Whale falls are known for the unique range of biota that congregate to feed on the remains (See this post, for example).

Science Daily reports on the discovery of a whale fall in the fossil record. The whale was excavated about 20 years ago and was dated to about 15 million years old. After being excavated the whale – which was about eleven feet long – was put on display at the Long Marine Laboratory in Santa Cruz. After that, it was donated to Museum of Paleontology at UC Berkeley. This is where the story gets interesting (from Science Daily):

As Pyenson prepared it for the museum’s collection, however, he noticed small clams in the nooks and crannies of the skull. He found 21 clams in all, each less than a centimeter in length, or two-fifths of an inch, plus one snail. Most of these organisms were on the skull, but some were nestled in the vertebrae. Haasl, a mollusk expert, thought the clams might be similar to those that cluster around whale falls today and that are able to extract energy from chemicals in bones with the help of specialized symbiotic bacteria. At whale fall depths of more than 1,000 meters, there is no light for photosynthesis.
Based on the shape of the fossil clam shells attached to the whale skeleton, Pyenson and Haasl determined that they belong to the same group of mollusks whose living relatives are chemosynthetic, confirming their initial hypothesis that this was a whale fall.

Science Daily goes on to say that:

In contrast, the Año Nuevo skeleton was unusually complete and hosted multiple mollusks. It also was small, which suggested to Pyenson that these specialized deep-sea communities didn’t need large whale carcasses to evolve. Previous researchers had hypothesized that whale-fall communities evolved with the origin of large baleen whales, such as blue whales, and oil-rich bones. Pyenson and Haasl proposed instead that the oil content of the whale’s bones was the more crucial factor.
“What we have are relatives of modern chemosynthetic clams associated directly with the skeleton of a tiny, tiny whale, smaller than any other known from modern whale falls,” Pyenson said. “That tells us that you don’t need very large whales to sustain a whale fall, but what you probably need is a really oily skeleton.”

The research is published here – it requires a subscription (if anybody has access I would love a copy). I have a copy of the paper now.