Looking at a promate skul, in general, how could you tell if it were/had quadrapedal?

Question

Looking at a promate skul, in general, how could you tell if it were/had quadrapedal?

Answer 1

Robin is right.  However, it's a little more tricky in primates.  If you look at a non-primate mammal (an opposum, for example), the foramen magnum (Latin for "Big Hole") really IS located at the back of the skull.

All primates have a somewhat anteriorly-placed foramen magnum; it's one of their characteristics.  In bipedal primates, the hole is extremely anterior and would place the head directly on top of the neck.

In quadrupedal primates, the foramen magnum is less anterior and would place the head at more of an angle.

This is often a difficult trait for my students to see at first; you really need to hold both a human and a chimp skull side by side to understand the difference.

Answer 2

The foramen magnum (the hole where the spine is attached to the skull) is directly under the back of the head in bipeds.  

In quadrupeds, the hole is in the back of the head.

Answer 3

Everyone who said the foramen mangnum is dead on. It's why scientists are thinking that the first bipedal primate was sahelanthropus tchadensis even though the only part of the skeleton they have is the skull. But the placement of the foramen mangum shows it's a biped.

Answer 4

A couple of answers here have re-invented how to define the location of the foramen magnum without saying "foramen magnum" itself... Just give Robin W her points already she said the magic words first and described the morphological distinction!

Answer 5

Well, ig you consider the size of a brain, in general the humanoid apes have it bigger, so thats the clue that could tell you wheather you are dealing with your greatgreatgrandma, or some alien speicy.

Answer 6

The orientation of the skull foramen magnum hole. Its orientation, will tell us which body position the primate was walking the most, and its pretty easy to know if he was walking upright just by looking at the hole orientation on the skull.

Answer 7

In a bipedal animal the spine enters the skull from the bottom as opposed to the back of the skull in a quadruped.  The eyes would look up if a bipedal had a quadrupedal skull.

Answer 8

By the angle of insertion by C1 into the base of the skull.