In the deep sea, no carcass goes to waste. Platoons of crabs, fish, and other scavengers make short work of most of the bodies which come to rest on the sea bottom, but every now and then the carrion-eaters are presented with a rotting bonanza; a whale fall. Muscle, viscera, blubber, and bone; it all gets broken down, but it takes so long that the whale carcass actually provides a temporary home for a variety of organisms which utilize the whale body in different ways. One, a worm called Osedax, actually makes it home within whale bones, and a new study published in the journal Palaios reveals that worms have been doing so for millions of years.
The evidence of the habits of the bone-boring worms comes from a 5.3-3.6 million year old partial whale skull found in southeastern Spain. Based upon the small, fossilized invertebrates found in the same layer, it seems the whale settled in water “several tens of meters” deep. Hordes of scavengers would have made the most of the flesh on the whales body soon after it settled, but as its bones became exposed worms began to make their homes in the skeletal architecture.
A series of bore-holes in the back of the whale’s skull tell of their presence. Sunk down beneath the surface of the bone were a series of burrows; long scrapes through the bone that look like they could have been made with a hammer and an awl. Anchored into the bone, the worms would then subsist on the lipid content of the skeleton, waving their feathery plumes above the surface of the bone to extract the oxygen they needed to survive.
This hypothesis (restored on the left) is based upon what is seen in the living species Osedax, and though the authors did not find the bodies of the worms they named the peculiar traces they left behind Trypanites ionasi. This is an important distinction. While the holes in the bones are most consistent with the habits of an Osedax-like worm, they may turn out to have been made by a different kind of worm. In this case the identification of the trace fossil, Trypanites ionasi, would remain, but the identity of the trace-maker would be different.
Now that paleontologists have identified these traces, however, they can start looking for them in other whales. Prehistoric whale falls have been identified on the basis of collections of snails, clams, and other organisms around fossil whale bones before, so perhaps the bodies of some of these whales were also home to bone-boring worms. Through such intricate traces, it is possible to envision the life of an age long-past.
FERNANDO MUN˜IZ, JORDI M. DE GIBERT, and RAUL ESPERANTE (2010). FIRST TRACE-FOSSIL EVIDENCE OF BONE-EATING WORMS IN WHALE CARCASSES Palaios, 25, 269-273 : 10.2110/palo.2009.p09-112r