What on Earth is this?

February 17, 2011 5:35 PM

What is this? I've had it hanging on my wall for a year or two. It was found on the sand below the water line at the Fire Island National Seashore/Wilderness. It's lightweight and friable, like a sea creature. It's 24 cm (9.4 inches) long by 11 cm (4.3 inches) wide. 24 cm is 1.7 monkey skulls, if that helps.
posted by jcrcarter to science & nature (11 answers total)

It looks like a sacrum. I don't know of what, though.
posted by phunniemee at 5:46 PM on February 17, 2011

I don't think that's a skull - it looks like a pelvis to me, based on the second photo.
posted by gingerest at 5:47 PM on February 17, 2011 [1 favorite]

Like gingerest, I'd guess hip bone, possibly cetacean.
posted by lekvar at 5:48 PM on February 17, 2011

Ah. Based on size and structure, I'm thinking sea lion or seal of some sort.
posted by gingerest at 5:50 PM on February 17, 2011

Google book link to Encyclopedia of Marine Mammals pictures
posted by gingerest at 5:51 PM on February 17, 2011

Like gingerest, I'd guess hip bone, possibly cetacean.

Cetaceans don't have hip bones, really. Just tiny little vestigial nubs of what used to be a pelvis.

But I agree that looks like a pelvis, or a piece of one.
posted by mr_roboto at 6:02 PM on February 17, 2011

Yes, what you probably took to be eye sockets are the articulation points for the ball joints of the hips. So, something with lower extremities. Having trouble nailing down a match but some variety of pinniped seems most likely.
posted by itstheclamsname at 6:06 PM on February 17, 2011

the fact that it is lightweight and friable makes me think that it is a bird bone. marine mammals don't need to have lightweight bones but birds do.

in your specimen, the spinal vertebrae (down the center) are fused to the surrounding bones. that's also a characteristic of bird skeletons, and in particular, the tailbone/pelvis area of a bird skeleton.

since you found it on a beach, i just googled a few different large water birds:
here's a picture of a swan pelvis

here's a (small) heron pelvis -there are also larger species
posted by scrambles at 6:11 PM on February 17, 2011 [2 favorites]

Completely agree - it looks like a pelvis and most likely that of a bird.
posted by Miko at 7:13 AM on February 18, 2011

to continue, i couldn't find a picture of a pelican's pelvis, but that's a good candidate, given the size and the fact that you found it on an ocean beach.
posted by scrambles at 7:36 AM on February 18, 2011

Chris commented (on the Picasa page) "It is the synsacrum and pelvic bones of a bird." Here's a drawing.

"The synsacrum consists of the three pelvic bones (ilium, ischium, and pubis) together with the sacral and lumbar vertebrae and some thoracic vertebrae, all fused together into a single rigid unit."
- Colin J. Pennycuick, Modelling the flying bird. He goes on to describe the synsacrum's role in respiration.

I think "pelican pelvis" is the answer I'll go with for now. Thanks all!
posted by jcrcarter at 9:57 AM on February 18, 2011