Cetother Bone

[Poser]

I found this bone in the sea cliff at Poplar Beach in Half Moon Bay, California. I found the bone partially sticking out of the cliff about 30 ft below the top of the cliff facing the ocean. A reputable marine biologist, Dr Bob Rubin, identified the bone as being the head of humerus from an extinct whale species known as Cetother. This whale species went extinct about 10,000 years ago and is related to the Grey Whale.

 

[Fossildude19]

@Boesse might be interested to see this.

[Boesse]

Howdy, I'm not so sure I see a bone here. This looks like a sandstone nodule or concretion - I don't see any obvious bone texture, and if it is bone, it's highly, highly waterworn beyond recognition or identification.

 

There's an added problem: there aren't any fossils or fossiliferous strata at Poplar Beach. It's all barren Pleistocene deposits which historically have not produced much. There are whale fossils that occur further north and south in the taller cliffs south of Miramontes Point and at Pillar Point, but they're encased in extremely hard rock and generally do not weather out like this except in small fragments.

[Poser]

It's too bad the classic spongy bone matrix isn't clear in these photos. I will take some better photos that will more clearly show it's characteristics. There is no question about whether this is bone or not. Dr. Bob Rubin, a college professor of human anatomy/physiology and marine biology at Santa Rosa Junior College in Santa Rosa, Ca, whom also is renowned by National Geographic for his expertise and work with manta rays has examined this bone and gave me his opinion as to what kind of bone he thinks it is. Also, having grown up on the coast of Half Moon Bay, Ca I can tell you that beginning with Poplar Beach and moving south down to Pescadero and further yet whale bones and mammoth bones are found on a regular basis. I found this bone in a cliff at Poplar Beach, plain and simple. I have no reason to make up a story like this. Thank you.

[Poser]

11 hours ago, Boesse said:

Howdy, I'm not so sure I see a bone here. This looks like a sandstone nodule or concretion - I don't see any obvious bone texture, and if it is bone, it's highly, highly waterworn beyond recognition or identification.

 

There's an added problem: there aren't any fossils or fossiliferous strata at Poplar Beach. It's all barren Pleistocene deposits which historically have not produced much. There are whale fossils that occur further north and south in the taller cliffs south of Miramontes Point and at Pillar Point, but they're encased in extremely hard rock and generally do not weather out like this except in small fragments.

I hope you get a chance to read my response to your post. I will keep you posted when I upload some better quality photos of this bone. Thank you, Boesse.

[Boesse]

Hi, sorry, I don't know who Bob Rubin is, but I'm more or less the local expert on fossil marine mammals from Halfmoon Bay (google 'Purisima Formation Boessenecker' and you'll find out). I'd like to see some photographic evidence of all these other discoveries from Poplar Beach you speak of, because that's news to me! More than happy to be wrong, but I'd be very surprised.

 

If you provide better photos that are zoomed in, I can maybe make out the spongiosa, but it's quite difficult in the present photos. Regardless, the shape is not a match for anything cetacean and if it is bone, all the external surfaces have been quite worn down, and would be a waterworn chunk of bone that eroded out of the Purisima Formation. I'm not trying to be rude or dismissive, I am literally both a paleocetologist and an expert on the fossil marine vertebrates from Half Moon Bay (pretty much the only paleontologist to ever pay serious attention to Purisima Fm. vertebrates) and I look at a LOT of whale bones as part of my job, and I do not recognize the shape of the specimen. For comparison, here's a couple photos of an extant minke whale forelimb - it's a juvenile so the proximal epiphysis is not fused, but the head of the humerus should be really spherical in virtually any cetacean humerus.

 

[Poser]

Hello, Boesse,

It's great to be able to communicate with a  marine fossil expert local to the San Mateo County coast. I thank you for your time. I guess I wouldn't expect you to know who Dr. Rubin is. He gave me an opinion as to what he thought the bone is. He may be right but may be wrong also. I have uploaded some better photos of the bone. I wish I could give you specific references about whale and mammoth finds along the coast. Over the years there have been publications in local newspapers such as the San Francisco Chronicle and the Half Moon Bay Review about these kinds of discoveries. There may not be many fossils or bones in the cliffs at Poplar Beach but that's where I found this bone. I am also including some pictures of a bone I found recently in the cliff at Redondo Beach which as you probably know is a little ways south of Poplar. This bone I found at Redondo is probably unidentifiable because it is not a full bone. It is just a portion of spongy bone with no particular identifying characteristics. Do you have any idea what either of these pieces might belong to? Thanks again for your time.

[Boesse]

WHOA! Now I'm seeing it! Spectacular! Not a marine mammal at all. This is an ankle bone - the astragalus - of a mammoth or mastodon! Excellent find. Was this found in the cliff itself, or loose on the beach? Thanks for taking better photos - something about the lack of detail made it difficult to see any bone texture, and what I did see looked waterworn. Now I can tell that the entire thing is in fact a very well preserved bone - it's just one that is kind of naturally potato-shaped and smoothly convex, aside from that groove on the 'plantar' side where it articulates with the calcaneum (heel bone).

[Poser]

Thanks Boesse! I am so excited to have a mammoth or mastodon bone and a  paleontologists explanation of what the bone is. The bone was not loose at all. I found the bone about 50 ft south of where the trail from the parking lot at Poplar Beach  hits the sand. I am 5' 11 and the bone was at about the height of my shoulders. It took a half hour of careful excavation to extract it from the cliff. Originally I was looking for shark teeth in the cliff. But I guess that's probably not the best place to look for shark teeth? 

Thanks again and sorry the first set of pictures being so grainy. I shouldn't have even posted those ones

Did you happen to get a chance to look at the other photos? Like I said it's probably difficult to make an identification on the other one because it doesn't seem to be much more than the chunk of spongy bone.

 

M

[Boesse]

Hey @Poser - I do not think the other piece is identifiable past 'bone fragment'. I've just checked some references, and I do not think that there are many published records of mammoths or mastodons from Half Moon bay or San Mateo County in general (there is one from an older unit, the Merced Fm., up near Pacifica, at one point considered the oldest mammoth in North America).

 

Is there any chance you'd consider donating the specimen to one of our museums in California and make it available for scientific study? Also, PLEASE keep an eye out for additional fossils in that cliff!