On Friday I gave you this specimen and left you to work out what it was by yourselves (for which I humbly apologise):

There were some great observations from the outset – Jake immediately spotted that it had strong jaws and looks like a carnivore and Manabu Sakamoto went on to explain the biomechanical reason for the strong jaws and recognised that it’s a marine mammal. Jake came close when he said that it’s something similar to a Leopard Seal and jonpaulkaiser came even closer with the suggestion of California Sea Lion. Neil subtly hinted that it might be a Stellar’s Sea Lion, but Zigg managed to work out that it is in fact the skull of a South American Sea Lion Otaria flavescens (Shaw, 1800).

The Marine Species Identification Portal proved very useful for me whilst identifying this specimen [1] – they have diagrams of the skulls in the “multimedia” tab for each species you click on. Diagrams tend to be very helpful for this sort of thing, since the key features are picked out and the less important features are less emphasised – something that’s hard to do with a photo. Of course, Photoshop can lend a hand, so here’s a more stylised diagram of this specimen I made to help make the identification a bit easier for myself:

Compare this to the diagram of the Stellar’s Sea Lion and South American Sea Lion and you’ll notice that the muzzle region and processes above and behind the eye and at to the sides of the back part of the skull are much more similar to the South American Sea Lion than the Stellar’s.

To give you an idea of what one of these impressive beasties looks like with the flesh on, here’s a nice photo of a male with his harem of females by Nestor Galina:

It’s this harem that has led to the massive skull seen in the males, since it takes a lot of fighting with other males to hold a patch of beach that will bring in the ladies. This mating strategy (where one male has lots of females) is called polygyny and it is usually associated with a high degree of sexual dimorphism (where one gender is a different size and/or shape to the other). This dimorphism is very clear in the photo above.

So well done to everyone – in particular Zigg, who got it spot-on. This week I may try something cultural to give the non-biologists a chance.

[1] Having gone through the process of identifying this skull I realised that it had already been identified by an expert in marine mammals who volunteered with me last year. I’m pleased to say that our identifications correspond.