Unusual dagger, billfish or bone “blade”?

[Ian]

Hi David,

The baculum bone is an interesting structure that shows a high degree of variation in length and shape among the various mammal groups that have one. In several species, the baculum is actually a Y-shaped structure with two separate arms that unite into a singe longer bone. In others, the two arms may still be present but they appear fused together, as a widening at the proximal end of the bone. Basically the two arms fuse into a single bone. The two arms each have a medullary cavity (for bone marrow) and fuse to form a single such cavity more distally. Thus, the proximal end in cross section shows two central cavities. This is what drew me initially to think of a baculum for the example in the original post. Because the tissue in the canals is missing in the cavities shown in the OP, we don't know what may have been there, There is the suggestion of a membrane that may have lined the cavity, but not enough evidence to distinguish a "nerve cavity" from a "medullary cavity" in a long bone (at least as I look at it).

As far as straightness, some species (including the walrus) can have straight baculum. Attached is a picture of a walrus baculum that resides in the Medical Museum of the University of Melbourne not far from where I live now.

As I noted in my original comment, if this is a baculum, it is an uncommonly large and straight one, and would have had some carving done to produce an acute point. Then again it could be the bill of a swordfish.

Whether a walrus baculum or the rostrum of a swordfish, there is a nautical flavor to the item and I would opt for maritime SE Asia as its origin.
.

[Athanase]

For me it's clearly swordfish
I cut several thin sections from swordfish rostrum (Gladius) and the internal structure is really similar. There are 5 other species of swordfish and the Blue Marlin have a rostrum more round in section with tow canals in the rostrum.
On the rod the sharp edges of the rostrum have been trimmed to obtain a round section.
As for the baculum in the museum picture, I really have doubts about the identification. I've never seen any baculum that looks like that (and I work in a natural history museum, so I've seen those of many species).

I had some image of cut section of various fossil rostrums of Marlins (from Miocene and Pliocene of Panama).

[Ian]

Athanase, thanks so much for your reply here!!! I can't comment on the attribution of the item in the museum at the University of Melbourne. I can say that Melbourne University's School of Medicine ranks in the top two or three medical schools in the country. But anyone can make a mistake I suppose.

As a natural historian and scientist, can you tell us what the main tissue is that comprises the rostrum? I'm not seeing on your cross sectional diagrams where blood vessels are located and would be necessary to maintain a viable structure.

[Athanase]

The images show fossils; the diagrams only show the bone area without detailing the bone's porosity.
But in reality, bone is very porous, crisscrossed with very fine blood vessels, cartilage, and adipose tissue.
Here's a post that illustrates it well.

https://www.researchgate.net/figure/...fig1_271389341

[Ian]

Athanase, thank you for posting that interesting information. The rostrum is actually a complex organ and it is interesting to read about its possible function in feeding. The bone structure of fish is clearly different from mammalian species. As a retired physician, I'm much more familiar with mammalian physiology and anatomy.

I am surprised by how little "bone" is actually present in these rostra. Cartilage seems to be a common component, perhaps more so than the rigid bony areas. This seems to be borne out by the stress data cited by the authors indicating that the flexibility of these organs can be quite substantial (important in some species to their feeding hypothesis).

However, this discussion seems to have departed some way from the original question of where this item may have been made. Whether a rostrum of a bill fish or a baculum from a walrus, the item would seem to have a nautical connection. By which ethnographic group or in what region of the world it may have been assembled is an interesting question. My vote is for maritime SE Asia.

[thomas hauschild]

Some pictures to compare and for future investigations.

A complete Oosik/walrus-baculum with 55 cm.

A piece of oosik ( roughly grinded for a knifegrip ) and its cross-sections. The bigger end of an oosik will show more porosity than the thinner end. This piece was cutted out right in the middle.

A Oryx skull without the horn. This is just the inner bone. But this is very light with many porosity. It looks more like the last picture from the museum than an oosik.

Penis-bones are common, but much smaller, in fox, coyote, wolf, dog and bears with a big differences in length and form. I used a fossil one from an ice-age cave-bear as a knife grip. This specimen was about 20 cm and nearly straight.

[wildwolberine]

Thanks for the comments, everyone! I agree this is likely a billfish bill, and probably SE Asian in origin. Surprised it’s apparently not a common item. The construction is so simple I assumed it would be a common trinket or curio item.