Friday mystery object #382 answer

Last week I gave you this skull to have a go at identifying:

mystery382

I thought it might be an interesting one, as it’s not from a species that often pops into my mind and I’m not sure I’ve ever seen one alive.

The depressions in the bone above the orbits tell us it’s a sea bird of some sort, as those are where the salt glands used to sit when it was alive. If you’re not familiar with salt glands in seabirds, I talked about them on the blog about 10 years ago (where does the time go?)

It has a very narrow and fine bill with a distinct hook at the end, which rules out the gulls and terns. Mergansers have a similar bill shape, but the rest of the skull is very different in shape and size. Cormorants and shags also have a similar bill shape, but unlike the mystery bird, their salt glands are located in their nasal region, so they don’t have the scars above the orbits.

Some of you were thrown by that cormoranty look, but a lot of you recognised this as being a small member of the petrel family. It’s a Manx Shearwater Puffinus puffinus (Brünnich, 1764) as spotted first by Hilary.

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Manx Shearwater by Matt Witt, 2010

These seabirds, with an English name taken from their breeding colonies on the Isle on Man (although they do breed elsewhere), are part of the same Order as the albatrosses. Despite being much smaller, they are also entirely marine, using their excellent sense of smell to find food over large distances over the water. This explains why you’re unlikely to see one unless you get to visit a breeding colony or happen to spend a lot of time at sea. When on land they aren’t that easy to spot either, since they nest in burrows – rather like Puffins.

Well done to everyone who worked it out, and if you got caught out by the cormorants, just remember that tip about the salt gland positon.

Friday mystery object #381 answer

Last week I gave you this specimen from the Dead Zoo’s “Unidentified” drawer:

mystery381

It’s a big and robust skull, albeit slightly battered, with no teeth and several missing pieces. However, the missing elements didn’t stop Wouter van Gestel and several others from recognising it as being from a sea lion.

That’s a really good start, but there are six living species in the sea lion subfamily (the Otariinae), which is where things get a bit more tricky, especially since they all show a large degree of sexual dimorphism to confuse things. There are also nine species of fur seals, which are close relatives and are also sexually dimorphic and hard to differentiate from sea lions.

However, there was a bit of a clue written on the specimen, for those who looked closely:

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So we know that this specimen was collected in 1855 by Dr Kinahan (an Irish geologist) from “Chinchas Is”. This group of three small islands off the coast of Peru is only really known for starting a war between Spain and several South American countries in 1864. It wasn’t actually the Islands that the fighting started over, but the large piles of guano that covered them. But I digress.

The location of the Chincha Islands immediately allows the likely species that this could be from to be narrowed down to two. Of course this is where it gets more complicated – differentiating between the South American Sea Lion and the South American Fur Seal.

However, there is a feature on this specimen which makes it really easy to distinguish from all other sea lions and fur seals, if you know to look for it. First of all, take a look at this very useful paper (pdf) by Sylvia Brunner which gives some great information on the identification of the various species.

Then, take a look at the palate of the specimen. Notice that the palate ends in a line with the point where the rear portion of the zygomatic arch meets the skull (see the red line in the image below if that doesn’t make sense):

SealionPalate

In every other species of fur seal and sea lion the palate ends at around the midway point of the zygomatic arch (where the writing ends on this specimen). There is just one species with such a long palate, the South American Sea Lion Otaria flavescens (Shaw, 1800) which is also referred to as O. bryonia.

It’s rare to find such a clear-cut indicative feature on a skull, so it’s always satisfying when you find one. I should note that this skull is from a female. The males are much more massive, but still share that feature of the palate.

So particular congratulations to Rémi and katedmonson who got the genus Otaria. Next time you have a sea lion skull to identify (as I’m sure you will) make sure you keep in mind that handy feature as the first thing to check and if that doesn’t help the be sure to check our Brunner’s paper.

Friday mystery object #380 answer

Last week I gave you this specimen from the “Unidentified” drawer in the collections of the Dead Zoo to try identifying:

mystery380

I don’t think anyone had much difficulty in identifying it, since it is quite a familiar and characteristic skull, but well done to everyone who worked out that this is a European Badger Meles meles (Linnaeus, 1758).

There are two other species in the same genus – the Asian Badger M. leucurus and Japanese Badger M. anakuma, so they also need consideration (skulls of all three species can be seen in this paper by Andrey Puzachenko). However, the Japanese Badger is a smaller and more delicately skulled animal and the Asian Badger can be distinguised by differences in the shape of the region around the bony bulbs that hold the ear bones (called the auditory bullae – in Asian Badgers they’re more obtuse and have a straighter lateral margin).

So apart from the distinction between two members of the same genus, this is a fairly straighforward specimen to identify, it makes me wonder why it wasn’t recognised in the collection? I think there are a couple of factors, which I’ll outline here.

The first is that the lower jaw (mandible) is missing. This is totally normal for almost any kind of animal skull you find, except these badgers, which have a well-developed bony process that locks the mandible into the long jaw articulation (known as the glenoid fossa).

Badger

Badger skull with mandible locked in place.

Glenoid

Detail of jaw articulation showing the main features. Red = mandibular articulation, Blue = inside of glenoid fossa, Green = glenoid process that helps lock the lower jaw in place.

This captive mandible is a dead give-away when you see it, but it does mean that when it’s missing it can be confusing.

A mature adult European Badger like this (as indicated by the well-developed sagittal crest) would also normally have extremely extensive wear on their molar teeth, due to the abrasive grit in the gut of their main diet of Earthworms.

Molars

Extensively worn upper molars of an adult European Badger

But the mystery specimen has remarkably little wear on those massive molars. This suggests that it probably had a different diet than is usual for a Badger from northern Europe – and no, not mashed potatoes. The same species in southern Europe has a different diet to their northern counterparts, dominated by insects and fruit, so I wonder if the specimen was collected during someone’s holiday to somewhere in the Mediterranean?

[UPDATE 28th April 2020. Several people have kindly shared images of their badger specimens and it seems that the level of wear in my specimen is not as common as I thought. In one discussion the issue of soil type was raised and I think that may play a big factor. This specimen came from Devon, in an area with sandy soil. Other specimens from areas with muddy or silty soils showed much less wear. This may be coincidence, but it would make sense that Earthworms with coarser soil in their gut would be more abrasive to eat and therefore cause more dental wear. That would be fairly straightforward to test using museum collections. If this hypothesis about wear is correct, then the mystery specimen could be from anywhere with soils that aren’t too sandy.]

I hope you found that useful, or at least a bit of a distraction from lockdown. Stay safe!