Tag Archives for Mammalia

Friday mystery object #383 answer

Last week I gave you this slightly mean mystery object from the Dead Zoo to have a go at identifying:

wp-1590685198270.jpg

I say it’s mean because it’s just a small fragment from the tip of the lower jaw. It does have some pretty distinctive teeth in it, so it’s probably not the most difficult mystery object I’ve shared, but it’s also from a species in a group of animals that are quite poorly known.

That said, Chris Jarvis was the first to comment and got it right immediately. However, there was a lot of subsequent discussion about how to be sure, given the poor representation of comparative specimens available and the similarities between this species and others in the family. That family is the Ziphiidae, which are the the Beaked Whales.

These cetaceans are rarely seen due to their deep water habits, sometimes diving to depths of nearly 3km (although more usually around 1km) to feed mainly on deepwater squid that they detect using echolocation. Most of what’s known about them comes from strandings – which is where this mystery specimen comes from.

The males tend to be smaller than the females, but the males of most of the 21 Beaked Whale species have tusk-like teeth that they probably use to fight over females, although the behaviour hasn’t been recorded, only deduced from scars and the behaviour of other animals with similar sexually dimorphic characters (there’s an interesting paper on the evolution of the tusks by Dalebout et al. 2008 is you’re interested [pdf]).

The teeth occur in different parts of the jaw and have a different shape depending on the species, so the fact these are located at the tip of the lower jaw means quite a lot of the species can be discounted. If you want to be able to do the narrowing down easily I recommend an old and somewhat unwieldy to navigate, but still very useful online resource – the Marine Species Identification Portal. If you can work out the navigation you can find small line drawings of the skulls of all species in lateral view.

Once you get that far it becomes easier to search for more detailed images of the couple of species it might be, which can yield some great 3D scans to help you work it out. Both Chris Jervis and katedmonson found examples and shared the links in the comments. Here’s a nice one from the NHM, London:

This species (the Cuvier’s Beaked Whale) clearly has bigger tusks than the mystery specimen, which you can see as a scan on the excellent Phenome10K resource*. The mystery object is the distal portion of the mandible of a male True’s Beaked Whale Mesoplodon mirus True, 1913. So well done to Chris Jervis for being the first to get in with the correct identification.

It may seem a bit odd to have just this small portion in the Museum, but as far as records go they represented a managable identifiable voucher for the stranding of the species in Killadoon, Co. Mayo, Ireland back in February 1983. These days we ask for even less material to keep track of strandings – just a small skin sample will do as long as it’s collected and recorded following the guidance of the Irish Whale and Dolphin Group’s (IWDG) Strandings Network.

These samples are stored in alcohol and form the Irish Cetacean Genetic Tissue Bank which is managed in partnership between IWDG and the Dead Zoo to provide genetic data for research into whales. It’s a fantastic resource, but I doubt that anyone could identify the species represented in the samples without access to a genetics lab. And that’s why I like bones best.

*A. Goswami. 2015. Phenome10K: a free online repository for 3-D scans of biological and palaeontological specimens. http://www.phenome10k.org.

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!

Friday mystery object #378

This week I’ve gone for a slightly more artsy image for the mystery object than usual:

You can click on the pictures to get a large version, which you might find useful.

I foolishly forgot to measure the specimen or include a scale bar, so I’ll update with a length as soon as I get back to the specimen. Sometimes it’s nice to rely just on morphology, so let’s see if anyone can work out what this is before I provide more information. [UPDATE: it’s 84mm long]

Have fun!

Friday mystery object #377 answer

Last week I gave you this unidentified skull from Dublin’s Dead Zoo to have a go at identifying:

wp-1583432771749.jpg

It didn’t prove too difficult to narrow it down, with everyone recognising it as a mustelid and Rémi immediately recognising it as being one of the Martens. But salliereynolds and Chris managed to get it down to the species, which is a bit of work.

There are around seven living species in the Genus Martes, although the total number varies depending on the sources you read. They have very similar skull shapes, the same dental formula and very similar tooth shape. In my experience the main feature to differentiate them lies in the auditory bullae.

wp-1583432771784.jpg

There are some decent online resources with images of Marten skulls, so it is possible to get a handle on some options. Each bulla is a 3 dimensional structure that is inflated in subtly different ways that are really hard to describe.

In a previous post I had a similar specimen (the same species as it happens) as a mystery object and I compared some bullae, but alas the image I referred to has since been removed. However, the important point is that there’s only one of the Martens that seems to have an outermost lobe that has a well-defined anterior sulcus (a fissure towards the front edge). This feature makes me think that this is a European Pine Marten Martes martes Linnaeus, 1758.

Thanks for your help in working it out!

Friday mystery object #370 answer

Last week I gave you this really nice skull from the Dead Zoo to have a go at identifying:

20191118_111405-01.jpeg

It proved a little more tricky than I thought it would, but I shouldn’t have been surprised given the poor quality of the photo and the fact that the cranium isn’t properly seated on the mandible (as pointed out by Allen Hazen).

Of course, that didn’t keep you all confused for too long. The large sinuses and relatively undifferentiated and widely-spaced teeth – except for those large canines – suggest that this is the skull of a some kind of seal.

Jeanie and salliereynolds noted the large, depressed opening over the nasal region, which is definitely one of the most distinctive features of this species. However, it also misled in the first place, with discussion of the possibility of it being from an Elephant Seal taking over for a while.

However, salliereynolds got back on the right track, while on Twitter Ray Chatterji was on the right track from the start with his suggestion:

The Hooded Seal Cystophora cristata (Erxleben, 1777) is really weird – well, the male is. He has an inflatable bladder on its head and one nostril contains a membrane that he can inflate to show off to other Hooded Seals.

I find it hard to think of this as anything other than nature’s attempt at making slightly disgusting balloon animals.

Well done to everyone who worked it out – I have a couple of fun guest mystery objects for you next week!

 

Friday mystery object #358

Another Friday, another mystery object. This week I’m going back to my favourite subject – skulls. This particular specimen has been brought in to the Dead Zoo for identification by customs and although I’ve narrowed it down, I’m still not 100% sure of the species just yet:

Adobe_20190613_200131.png20190613_200359.jpg

It’s a fairly straightforward genus for anybody who knows their ungulates, so cryptic clues are appreciated. However, the species is harder to work out, so bonus points for detail. Have fun!

Friday mystery object #343 answer

Last week I gave you this mystery skull from the Ulster Museum to have a go at identifying:

If you’re a regular follower of Zygoma then you may have seen some of my previous posts talking about the skulls of the various smallish carnivores like mongooses, mustelids and viverrids. Generally though, mongooses have a more domed region above the eyes, while mustelids have a shorter snout, so this is most likely one of the viverrids.

It’s a difficult one to get down to species, since it’s from a group of carnivores that have have a fairly uniform skull shape, so it takes some detailed investigation to work out exactly what we’re dealing with. However, as I have talked about before (and as palfreyman1414 remembered), there’s a very helpful identification guide developed by some French researchers which summarises some of the most useful characters to use in identification.

Most useful to my mind is the matrix of characters that allows you to narrow down the possibilities until you’re left with the most likely species (watch out, the security certificate has expired). Once you’re down to a few possibilities based on those specific characters it can help to check the specimen images on the Animal Diversity Web which lets you get a better idea of overall shape and things like tooth form.

As it turns out, my 270th mystery object also provided a useful image for comparison:

mystery270

The reduced upper second molar (or M2) and the shape of the M1 in this specimen from the Grant Museum of Zoology is remarkably similar to the Ulster Museum specimen and it turns out it’s also from a species that made it to my shortlist using the matrix. So I’m fairly sure that this is an Abyssinian Genet Genetta abyssinica (Rüppell, 1836).

To give you an idea of what they look like, here’s a Common Genet in Wrocław Zoo by Guérin Nicolas, 2008

Well done to everyone who worked out we were dealing with a genet, but particular props to palfreyman1414 who was spot on when he said:

I’m wondering if, … this is related to the Abyssinian thingy you spent hours checking on from a complicated table of characteristics across 27 species…

Well remembered palfreyman1414, well remembered…