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.

5 thoughts on “Friday mystery object #417 answer

  1. Both my specimens illustrate and that referred to in the book on Australian skulls I have say that the palatal vacuities on Eastern Grey Kangaroos are small or absent, on Red Kangaroos they closely match your specimen. I don’t have access to a Western Grey Kangaroo skull either but there are some good pictures in the Museums Victoria online collection that show vacuities in their Western Grey (shame they only seem to have imaged one so far) but not that match your image. The third Incisor on Eastern Greys is also about as long or longer (measured proximal to distal) than the other two combined whereas in Reds it is much shorter. It appears to be somewhere in between in Western Greys. It seems to be shorter in your image, I would therefore suggest this is a small Red rather than a large Grey of either type.

  2. My Sister has a Western Grey skull and the palatal vacuities are the same as the ones in the Vic Museum specimen I referred to earlier, that is, different to your specimen. The incisors have fallen out of hers so no comparison can be made there. She measured hers at 192mm long (but has never measured a skull before). I suspect there is greater variation in skull length in kangaroos than the information you have found. So I’m still going to suggest yours is a Red.

  3. I don’t want to be a pest if you’ve had a tough week, but is there any chance you could post a photo with the lower jaw removed so we can get a good view of what’s there and what’s not there on the palate?

    • It was a tough week because I was in the UK burying my father. Only just back and the skull is from a mounted skeleton and it’s firmly wired together, so no chance of getting photos of the palate I’m afraid!

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