Bite Back

Here’s some labelled images for further instruction:

Side view of an Allosaurus skull. From Savali, Udo M. (2017, 22 December). BIO 370 — Vertebrate Zoology — Dinosaur Skeletons. 

Views of an alligator skull. From Savalli, Udo M. (2009, 22 December). BIO 370 — Vertebrate Zoology — Alligator Skeleton.

You should consider that in general, relationships between bones and soft tissue structures are maintained over the course of evolution. The eardrum in diapsids is closely associated with the quadrate. The quadrate along with the quadratojugal and the squamosal form the bony bar behind the infratemporal fenestra. You can see that the quadrate has a position closer to the midline of the animal than the quadratojugal for the crocodilian: on the dinosaur the quadrate is hidden by the quadratojugal from side view for the most part. You’ll also note, as alluded before, that the aforementioned bony bar at the back of the skull on the alligator has a much greater width front to back than on the Allosaurus. It expanded forward, forming a wall over part of the infratemporal fenestra, but also backward to enclose the eardrum completely.

Here’s an interpretation I drew up: 

Modified from figure 2.B of Montefeltro, F. C., Andrade, D. V., & Larsson, H. C. (2016). “The evolution of the meatal chamber in crocodyliforms”. Journal of Anatomy, 228(5), 838-863, showing the back of the skull of a dwarf crocodile.

As to the why, it seems hearing was fairly important to crocodile ancestors in their daily lives to justify the investment up and to including evolving ear lids to protect the now large eardrums as reported on the above-cited Montefeltro et al. (2016) paper. You can also find there an ample discussion of the background for the above summary.

~Mossy Moose Molars~

British Columbia, Canada

Here’s a really interesting skull someone showed me today.

Its from Lauren Hull’s Skull Cleaning

Here’s a really interesting skull someone showed me today.

Its from Lauren Hull’s Skull Cleaning

I’ve had this little guy for a while, but, this may sound weird, but it took me a while to figure out how I felt about having a mummy. not for any moral reasons, but because something about mummified tissue has bothered me in the past. I’m always paranoid it’s going to rot, or attract bugs, and I never want to touch it. but this one seems to be preserved chemically rather than simply dried, and both that and how cute he is have convinced me to keep him.

From the University of the South’s 1993 yearbook.

Here are some of the best vintage photos I’ve collected.