Laboratory inquiry 1: Outgroup

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Your task in the first laboratory inquiry assignment is to develop a hypothesis about the anatomy of the common ancestor of two species of anthropoid primates. To accomplish this, you will need to consider the anatomy of an outgroup, in this case a species outside the anthropoids.

In the previous laboratory, you were able to examine a skull of a prosimian primate as an outgroup. That can work very well as a way to compare the anatomy and number of teeth and other features of the cranium. But to compare postcranial anatomy you will need to have a complete skeleton of a prosimian primate.

Unfortunately, we don’t have one in the laboratory. Instead, we’ll consider some features of the skeleton of the mongoose lemur here:

Lemur skeleton illustration

The mongoose lemur has a body between 30 and 45 centimeters long, with a long tail. Its natural habitat is in northern Madagascar, and it also can be found today in the Comoros Islands.

As you can see from the picture, the mongoose lemur’s skeleton has arms and legs nearly the same length, with its legs just a bit longer than the arms.

The skeleton has 12 thoracic vertebrae and 7 lumbar vertebrae. It also has a long tail.

The mongoose lemur’s scapula is relatively long and narrow. This is contrast to a human scapula, which is triangular in shape with a very broad superior border.

As you formulate a hypothesis about the anatomy of the common ancestor of your anthropoid species, this information will assist you.