Tag Archives for Marsupial

Friday mystery object #417 answer

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

Pretty much everyone recognised it as a marsupial, thanks to the palatal vacuities and inflected angular of the mandible (as Allen Hazen alluded to).

The size, general shape of the skull and tooth shape narrows down possible species very quickly, as it’s quite large (at around 17cm) and quite kangeroo-shaped. That leaves the likely options as Eastern-grey, Western-grey or Red kangaroos.

Red Kangaroo skulls tend to average around 205mm long, Greys tend to average in the region of 145mm, so this falls between the two – either a small Red or a large Grey.

The sutures of the skull seem well-fused and there are quite robust muscle scars, suggesting a well-developed adult animal. For me this hints that it would probably be in the large end of the size range of its species, rather than at the small end of the size range – hinting at it being a Grey.

Another feature that hints at Grey Kangaroo is the crown of the third upper incisor, which in Red Kangaroos tends to be slightly broader than it is long, whereas in Greys it tends to be longer than wide.

Unfortunately, I’ve so far failed to find good enough verified images or specimens of Western Grey Kangaroo skulls to differentiate from the Eastern Grey.

I do know that this mystery specimen is identified as an Eastern Grey Macropus giganteus Shaw, 1790, but I am also aware that the taxonomy of these animals has been complex and confusing, especially since their ranges overlap so I don’t fully trust that identification. Sometimes a dose of scepticism is important when dealing with historic collections, so I think I’ll just leave it there after the tough week I’ve had.

Friday mystery object #412 answer

Last week I gave you this rather nice skull to identify:

I was hoping that it would catch some of you out, since at first glance it looks like the skull of some kind of canid. I thought I had caught out Joe Vans, but then he noticed one of the features that sets this skull apart from dog skulls – the pinched-in section in the mid-muzzle area. Then everyone started piling in with their observations and my hopes of being tricksy were fully dashed.

This is of course the skull of that paragon of convergent evolution, the Thylacine (AKA the Tasmanian Wolf or Tiger) Thylacinus cynocephalus (Harris, 1808).

I’ve written fairly extensively about convergent evolution between Thylacines and canids before, when I worked at the Grant Museum of Zoology, so I won’t go into huge detail here, but I will give you an annotated image showing some of the features to look for that help distinguish these marsupial carnivores from their placental dopplegangers:

A= 8 incisors vs 6 in canids
B= Lacrimal duct on outside of orbit
C= Inwardly deflected angular process
D= “Pinched” midsection of rostrum
E= Palatal vacuities

These physical differences between the Thylacine and the Eutherian canids are features common to many marsupials and they act as reminders that evolution is limited by what it has to work with. At the most fundamental level that means DNA.

In recent years the methods for successfully extracting and sequencing DNA from museum specimens has moved on in leaps and bounds. In 2018 these advances allowed the Thylacine’s genome to be assembled, allowing comparison with their morphologically similar, but taxonomically distant counterparts.

The team that did this went looking for similarities between protein coding genes in the different lineages at first, to understand what was driving the morphological convergence – but it seems that they were looking in the wrong place.

When they looked more closely, it was actually in the cis-regulatory elements (the non-coding DNA that used to be considered “junk”, but which is now recognised as playing a vital role in regulating development) that genetic convergence was seen. It turns out that these elements were also driving convergence in brain development between Thylacines and canids.

It seems that protein coding genes are quite stable – if they mutate they usually stop working properly, so the mutation often doesn’t persist. But mutations in cis-regulatory elements can change gene expression with less risk of catastrophic consequences. Unsurprisingly that means they are increasingly being seen as the main drivers in evolutionary adaptation. If you’re interested in finding out more about this fascinating research, a pdf of the 2019 paper on Thylacine/canid genetic convergence by Feigin, Newton & Pask can be accessed here.

I hope you enjoyed this short trip down the road of convergent evolution, with a hat-tip to the genetic drivers involved.

Friday mystery object #313 answer

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

20170828_122111-01

There was some lovely wordplay in the answers, with Chris getting in early with this great one:

I thought I had a shrewed idea until I saw the Bilby in the background which could show this isn’t the elephant in the room. Coot is legs be too Bandi?

This rules out elephant shrews and correctly identifies it as some kind of bandicoot, thanks to its marsupial case companion. Then palfreyman1414 dropped an anagram into the mix with:

Mere ale plus Satan?

which is so nice I wish it was correct, but alas this isn’t a Long-nosed bandicoot Perameles nasuta, although it is in the same genus.

Allen Hazen wondered “How badly does fur fade in preserved specimens?” and that turned out to be the key question, since everyone shied away from the correct identification, because one of the characteristics of this species’ pelage (that’s mammal-fan speak for ‘fur’) is that it’s supposed to have two stripes on its hindquarters or, more accurately, bars. As it turns out, fur fades quite badly in preserved specimens.

This is in fact a Marl or Western barred bandicoot Perameles bougainville Quoy & Gaimard, 1824 (NMINH:1906.301.1).

Marl

These diminutive Australian marsupial insectivores are vulnerable to introduced predators like cats and foxes, so their wild population only remains on some islands after once being widespread across Western Australia.

Even on the islands where they have some protection from placental predators, they face issues with disease, since their population has shrunk by so much it has impacted on their genetic diversity – reducing resistance to disease at the population level. In particular, a virus that causes tumour growth is affecting the animals on some islands, leaving the species increasingly under pressure.

pv8bk_f-maxage-0

One island does remain free of the virus, so hopefully with proper management the Marls will be able to hang on in there.

Friday mystery object #310 answer

Last week I thought it was time for some more bones, so I gave you this specimen from the Dead Zoo to have a go at identifying:

mystery310

There was no scale, the photo is far from ideal and the specimen isn’t in the best condition, but the animal is pretty distinctive, so I thought it wouldn’t prove too much of a challenge – and it turns out that I was right.

Palfreyman1414 was the first to identify it to genus level, correctly recognising that it was one of the two Notoryctes species of Marsupial Mole from Australia.

The weird limbs are a pretty good indicator this being a digger, with large muscle attachments and robust forelimbs, but it has couple of large claws rather than the ridiculous giant hands of the Old World Moles and it has a shorter skull.

Double prep mole from the Horniman Museum

Double prep of an Old World Mole Talpa europaea from the Horniman Museum & Gardens

The skull is more similar to that of the golden moles of southern Africa, although their rostrum (nosey bits) tends to be more concave while the marsupial moles have a more convex rostrum (and in some cases, weirdly flaring zygomatic arches).

mystery268

Lateral view of the skull of a Giant Golden Mole Chrysospalax trevelyani from the Grant Museum of Zoology

Now distinguishing between the two species of Marsupial Mole is a bit more tricky, not least because they are quite poorly known animals and there aren’t many specimens available for comparison – this is particularly true of the Northern species, which was first described as recently as 1920.

This is actually quite useful to know, since the mystery specimen came into the collection in 1897 – from Southern Australia – so it’s safe to say it’s the Southern Marsupial Mole Notoryctes typhlops (Stirling, 1889), but that’s not very helpful from a morphological perspective.

So far I’ve not found any useful skeletal features that help differentiate the two species, but apparently their fur colour is a little different, with the Northern species having pinkish or cinnamon fur and the Southern species having yellowish-white to a deep gold. To see what they look like with their fur, here’s the taxidermy partner to the mystery skeleton:

Southern_marsupial_mole

Taxidermy Southern Marsupial Mole Notoryctes typhlops in the National Museum of Ireland – Natural History

As with most moles these subterranean critters have adapted to spending much of their time underground by losing their eyes, investing in some serious digging equipment and tuning in to smells and low frequency sounds.

I hope you enjoyed this little tour around the main moles of the world! More mysteries next week.

Friday mystery object #299 answer

Last week I gave you this cute critter to try your hand at identifying:

mystery299

I thought the presence of fur would make it easier than usual, but of course, hair hides a lot of rather useful diagnostic features that you can find more easily in the bare bones.

However, you managed to pick up on a couple of the key features that gave this specimen its name: it looks like a lagomorph (one of the hares, rabbits or pikas) or maybe a larger rodent and it looks like a macropod (one of the kangaroos, wallaroos or wallabies). Several people wondered about it being a Kangaroo-rat, but that distinctive back foot, with its big central toe and then the skinny little side toes (you have to look carefully), tells us that it’s the other way round and this is a marsupial that looks like one of the placental glires (that’s the group containing the rodents and the lagomorphs).

The marsupial identification was initially spotted by palfreyman1414 and tenaciously defended by Rebecca, who was on the right track when she veered toward it being something in the Potoroidae (the rat-kangaroos, potoroos and bettongs), a suggestion that was put forward in a more cryptic way by jennifermacaire.

This is in fact a Rufous Hare-wallaby or Mala Lagorchestes hirsutus Gould, 1844, which marsupial wrangler Jack Ashby spotted with ease:

I should say that it is indeed VERY faded, after spending over 100 years in a glass ceilinged gallery.

These small macropods live on a few islands in Western Australia, but their original wider range has been dramatically reduced by changing land use patterns resulting from the breakdown of the relationship between the Aboriginal people and the land, caused by encroachment and systematic persecution by European settlers. It’s not onlyhumans who suffer when people treat each other badly.

Friday mystery object #269 answer

Last week I gave you this mystery object from the Grant Museum of Zoology to have a go at identifying:

mystery269

If you’ve been checking the mystery object recently you’ll notice that this specimen has a feature of the palate that I made reference to in the answer to mystery object #267 – the Tasmanian Devil. It’s incompletely ossified, which is a characteristic of marsupials.

The large curved canines and pointed premolars suggest some predatory activity, while the flattened molars suggest some grinding of vegetation, making this one of the marsupial omnivores, in the Order Peramelemorphia.

The large size of the skull and the long curved canines make this specimen rather distinctive – as first spotted by Richard Lawrence, this is indeed a Continue reading →

Friday mystery object #267 answer

Last Friday I gave you this specimen to identify:

mystery267

It was a pretty distinctive one, but a great specimen – and a nice robust example of this particular species.

The partially ossified palate and nasolacrimal (or tear) duct on the external border of the orbit shows that this is a marsupial, and the pointy, robust teeth suggest that it’s highly carnivorous with a penchant for carion, which narrows down the options pretty effectively.

As many of you recognised, this is a Tasmanian Devil Sarcophilus harrisii (Boitard, 1841) – so well done to Tone Hitchcock, Chris, Cindy Nelson-Viljoen, Ric Morris, henstridgesj, palfreyman1414, Lauren McCafferty, joe vans, Daniel Jones and Daniel Calleri, Allen Hazen and Michelle for getting this one right. The key was definitely in those marsupial characters, which immediately ruled out any of the highly diverse placental carnivores.

Tasmanian Devil (Sarcophilus harrisii), Tasmanian Devil Conservation Park, Taranna, Tasmania, Australia by JJ Harrison 2010.

As several of you alluded to, the Tasmanian Devil is undergoing a major decline in population at the moment, mainly due to a particulary nasty transmissible disease that causes tumours to develop on the face, preventing feeding. The tumours are spread between individuals when they bite each other, especially when feeding, which is pretty common Devilish behaviour.

In fact, Devils are pretty rough and tumble creatures in many of their behaviours. When breeding they have a large litter of up to 30 young, which have to compete for just 4 nipples in the pouch. Unsurprisingly, few of the litter survive and presumably those that do are pretty pushy.

Hopefully the Devils will survive their current population crash. There are some individuals who show some resistance to the facial tumour disease, which reflects the importance of genetic diversity within populations. It would be a great shame if the Devils went the same way as the other large marsupial carnivore, the Thylacine.

Friday mystery object #116 answer

On Friday I gave you this skull to identify:

Jake spotted that this was a marsupial’s skull straight away and many of you suggested Kangaroo using a variety of crafty clues. There was also a well reasoned suggestion of Koala that fell just a little short.

Obenedo missed the correct answer by a hair(y nose) but got the right type of animal, as did jonpaulkaiser, Matt King, Jake and Cromercrox.

Neil managed to go that little bit further and get the right species –  Continue reading →