Friday mystery object #420 answer

Last week I gave you this deep sea mystery to have a go at identifying:

It was picked up on the Porcupine Bank, which is a raised area of the Irish shelf around 200km off the west coast of Ireland, just before the drop off into the abyssal depths of the Atlantic.

Although it’s a little hard to tell from the photo, the object is around 1m long. It has a conical cavity at the base, but it’s fairly shallow, extending only about 20cm before fully closing up.

The fact this isn’t a tube allows us to rule out the possibility that this is from some unholy giant scaphopod:

Or indeed a particularly well-formed giant ship-worm, like one I’ve featured before:

You can’t tell from the photo, but it’s very dense and heavy. What you can see is that it has some quite well defined longitudinal ridges:

This isn’t something you normally find in horns, but you do find in tusks. So the question has to be, what kind of tusk is this?

I’ve talked about tusks before on this blog, and I’ve spent a lot of time identifying ivories over the years, after learning key diagnostic features from the wonderfully knowledgable Dr Sonia O’Connor, both in her training courses and working alongside her when I was at the Horniman Museum and she was visiting to do some research. This tusk reminds me of one of the more tricky ones we looked at.

The marine location suggests it could be from a Walrus. The overall shape isn’t bad, but Walrus tusks tend to be no more that about 75cm long at their longest. They also have a more squared-off section at the base and often a deeper groove on the sides partway along the length from the base, so it seems unlikely.

Really that just leaves something proboscidian – but here we hit the difficult bit. Mammoth tusks have been dredged from the sea many times, from fossils in sediments that became covered by sea level rises after the melting of glaciers around 11,500 years ago. However, Elephant tusks were transported in huge nubers to Europe by ship to supply the demands of the ivory trade between the late 18th and early 20th Century, so it is entirely possible that this is a relic of that trade (as suggested by Chris Jarvis).

In my experience, submerged Mammoth tusks are seldom in such good condition as this. While there is some degration and flaking towards the tip, there is much less of the deep staining or separation of dentine fibrils that I would normally expect from Mammoth tusk submerged for several thousand years.

However, if it was more deeply buried until recently it may have avoided the worst of that degradation, so that expectation isn’t good enough.

There is a method for distinguishing between Mammoth and Elephant ivory, that relies on an artefact of the tooth development process. This involves measuring the intersection angle of Schreger lines (an optical feature resulting from light interacting with dentine tubules) in a polished section of the tusk:

In Elephants the angle of intersection tends to be obtuse (>90^o), whereas in Mammoths they are more acute (<90^o). Of course, to see this would require cutting a section of tusk, so it may have to remain a mystery until the desalination treatment has been completed and I can see if there is an opportunity to check any broken surfaces or prepare a small sample.

The question in this case has to be, how important is it to know the identity, compared to the importance of keeping the specimen as intact as possible? That is a bigger conversation that will need to be had with my colleagues.

Thanks for your thoughts everyone!

Friday mystery object #371 answer(ish)

Last week I gave you these two genuine mystery specimens from Katharine Edmonson to get your thoughts on:

Tooth-1_9464

It was most definitely NOT an easy challenge, and I’m still not sure I know the answer to either, even after looking at every species I can think of that might have similar structures.

These are both clearly teeth, considering the internal details:

One image shows the root area of a full tooth, and one shows a section through a tooth – both of which provide really useful information. For example, the full tooth has a central dentine growth that you often find in animals that deal with a lot of strain on the tooth or where infection has got in (I’ve shown this before in elephant ivory).

The sectioned tooth shows a zone of dentine in the middle that suggests some hard use. Notably, that zone matches the shape of the cross section, so those grooves in the sides of the tooth aren’t from wear – they must be intrinsic to the tooth shape.

Generally, tusk cross sectional shape reflects the shape of the socket (until it gets worn down) – so that gives a pretty good way of narrowing down possible options. For example, I’d discount walrus, since they have an almost rectangular section. Warthog tusks have a section somewhere between the number 8 and a mushroom in shape, and Hippopotamuses have a triangular section to their canines, but their incisors are quite circular in section.

Warthog tusk socket

Then there are wear facets, that can give teeth and tusks a characteristic shape. Hippo canines grow in a corkscrew if unworn, but by rubbing against each other they remain sharp and fresh (like rodent teeth).

This means that teeth and tusks can look weird if the normal wear is disrupted, either by not happening or by happening too much.

There are also unexpected tusks that need to be considered, like the Indian Rhinoceros or dugongs that have hidden tusks.

Rhino tusks

Dugong tusk

Of course, some animals have really weird tusks, especially when they’re young or if they’ve experience something that leaves the tusks deformed or altered – which can make identification really hard.

There were a lot of suggestions of Sperm Whale tooth, which is a possibility, but I’ve not seen any that really come close. It may be that both of these are tusks from something more unusual, like beaked whales, but I have looked at a lot of examples of beaked whale teeth and I can’t find any examples that match either of these.

On balance, I think that the first of the tusks may be a Hippopotamus incisor that’s been misaligned with another tooth, causing excessive wear and horizontal stress lines to appear during tooth growth – this is rampant speculation I hasten to add. The second looks a lot more like a Warthog tusk in section than anything else, although the end is more spade-like than I’d expect.

So, after a lot of consideration I’m still uncertain of the identification of either of these, and I would be delighted to hear if you have any more thoughts!

Friday mystery object #371

This week I have a couple of guest mystery objects for you to have a go at identifying. Here’s the first:

Tooth-1_9464 Tooth-3_9467 Tooth-4_9467

And this is the second mystery object:

These photos are from Katharine Edmonson and they’re real mysteries, so no need for cryptic clues or hints – let’s see if we can work out what these are using our collective knowledge. Should be fun!

Friday mystery object #226 answer

Last week I gave you this rough and ready mystery object to identify:

I thought it might be a bit of a challenge as it had originally been misidentified as a piece of elephant tusk by someone in the museum, many years ago, so it was obviously not a straight-forward identification.

One of the key identifying characteristics of ivory are the Schreger lines, as pointed out by Carlos and rachel. These lines are an optical effect caused by light interacting with the dentinal tubules that provide the structure of the tusk:

Tusk section showing Schreger lines

However, these lines aren’t always visible and it will depend on the angle of the cut of the tusk and the angle and intensity of the light.

Another factor to keep in mind is the nature of the material. If you look at a cut section of elephant tusk you note that you get clean edges, because the tusk is quite hard and keeps its structure when cut. It can also show faint growth rings, radiating from the pulp cavity (nearer the tip the cavity is filled in):

Section of elephant tusk showing clean edges

Instead, the mystery object has a very rounded edge and no clear structure. This suggests to me that it’s horn that has been treated with heat to mould it into shape (keratin that makes horn and hair has thermoplastic properties, which is why hair straighteners work).

So what this mystery object appears to be is a piece of bovine horn – probably cow – that has been melted and shaped at one end to form a cup. The superficial similarity to elephant tusk may or may not have been accidental, after all, elephant ivory is a much sought after material.