In the previous post, TamanduaGirl, commented that it looked like the tear duct in the anteater skulls figured was outside the orbit, unlike other placental mamals.
Actually the tear duct is on the inner part of the orbit (where the orbit bone slopes towards the eye). It's difficult to see on a two-dimensional image, but I've enhanced the image below.
In each image, the tear duct is actually the smaller hole (ringed in the lower image) - the larger hole is a nerve opening. In each instance, the duct is positioned just slightly on the inner side of the orbit. The limit of the orbit is indicated with a dotted line in the lower image.
In the image linked to appears to be a cast, and, as such, only shows the larger nerve opening and not the tear duct. Small openings are often missing from casts.
More on monotreme-marsupial-placental evolution soon.
Thank you for the explaination. I don't know that much about skulls but found it interesting when I stumbled across you blog.ReplyDelete