Thursday, April 27, 2006

Hearing ancient hyraxes

Male Thyrohyrax
Stranger Fruit already picked this up, but I want to add some art to the discussion of new discoveries about a 'banana-jawed' fossil mammal.

Paleontologists had always known that many fossil hyracoids (members of the clade which includes modern hyraxes – or is it hyrices? – and elephants) have a hole in their jaws. It is called an internal mandibular fenestra, highlighted in green in the image above.

Analysis of skulls suggested that the fenestra (Latin for "window") was only present in one sex, but it wasn't possible to tell which sex had the hole. With a larger sample size and better preserved teeth, the new research shows that only males possess the fenestra.

Comparisons with existing hyraxes and careful examination of the sides of the fenestra suggest that it is some sort of resonating chamber which the Thyrohyrax probably used in attracting mates or defending territory. The other leading hypothesis was that it held an enlarged salivary gland, but that isn't consistent with sexual dimorphism, nor does the surface of the bone in the fenestra match well with surfaces known to match up to salivary glands.
The researchers hope to build resonation chambers based on the skulls in order to hear what sort of sound these chambers would produce.

Incidentally, a little googling revealed that creationists think the hyrax could not have evolved. But don't tell that to Thyrohyrax, nor to the people in the field studying their evolution.