Basilosaurid neural spine?

[Mahnmut]

Hello together,

I just got a package in the mail, that is less fun than fossil hunting outside, but still I like what I see.

I got no information on locality or age, but I can assume north africa.

It was sold as Basilosaurus neural spine.

What I don´t understand is the proximal surface of the left one, it doesn´t  look fractured, rather like a complete bone/articulation surface. Also I am not sure if the size is right for Basilosaurus itself.

Although I spent some time tinkering with whale anatomy, I have never seen a basilosaurid bone up close, so I am out of my expertise her.

Who can help?

Scale is in cm/mm

Thanks

J

 

[Mahnmut]

Hello again.

I took another picture of the surface in question, it appears somewhat similar to the natural breaking point in antler, with a central bulge and surrounding depression.

The smaller one seems to be shaped similarly, although I cannot tell because there is matrix(?) sticking to its proximal end.

I do not understand that shape if they where  part of  vertebrae. Maybe it is just eroded that way.Or it is not a spinal process at all?

@Boessecan you please enlighten me? Or anyone else who might have an idea?

 

Thanks in Advance

J

[Boesse]

Basilosaurid neural spines are flattened from side to side. These are likely to be phalanges or metacarpals of...something.

[Mahnmut]

Thank you for taking the time!

 

I scanned it via photogrammetry, maybe that can help to solve the puzzle.

So now this is a mystery bone, one side looking like a  phalanx, the other like something else. 

I begin to  think it is a composite , although the texture fits really well on both sides of the one visible fracture, which you can see better in the fotos than in the 3d-scan.

 

 

I tried my best, but couldn´t get good lighting, so there are some bright bumpy artifacts.

There is also the wire I used to suspend the fossil,  stupidly covering the fracture, the apparent kink one third from the thick end of the bone is mostly artifact of the 3d-scan, the wire didn´t get resolved well.

Still, the overall shape is recognizable.

here is the link to sketchfab.

Who can tell me what this is? Or what it is made of?

https://skfb.ly/6PZC9

 

Puzzled regards,

J

[Mahnmut]

The more I look at them, the more I think I know what they are (see picture).

I´d still appreciate any hint at what the components may be.

Thanks,

J

[Mahnmut]

Hello together,

I assumed these must be composites because one end looks relatively phalanx-like to me while the other does not. I just hear that the fracture looks good, which I took as a sign of craftmanship after the aforementioned thoughts.

Could it be that they are end or near end phalanges, thus showing only one clear articulation surface? Mosasaur maybe?

 

[Mahnmut]

@pachy-pleuro-whatnot-odon, you know your marine reptiles, what do you think of this bone?

I do not know if I can change the thread title after learning that this is definitely not a basilosaurid bone.

 

Cheers,

J

[Mahnmut]

Ahoi!

I think I solved it:

I just read the second edition of "Oceans of Kansas" and on page 197 there they are: Plesiosaurid caudal ribs! (Could be cervical ribs as well).

This teaches me again to keep open minded. I was quite sure the fracture was not fabricated, but when I could not make sense of the anatomy I discarded it as composite. There are astonishingly well made composites, but of course there is always anatomy I do not know yet!

 

If changing the thread title is possible, I do not know how. Should be "Basilosaurid neural spine?  Solved Plesiosaurid caudal/cervical rib"

 

Thanks,

J

[Mahnmut]

On 1/28/2020 at 12:32 PM, Mahnmut said:

I just realize that I guessed quite right concerning the location without knowing it.

 

 

[pachy-pleuro-whatnot-odon]

Hi Jan,

 

Sorry for responding so late. I wanted to do some reading-up before responding, as I'm not particularly familiar with the fossils or sediments of the Western Sahara, where I think these finds were made. I mean, the pieces were probably not classed as Basilosaurus entirely without reason, right, if only for it being the more likely identity based on the find locality. And, unfortunately, it took me some time to get the time for this.

 

In the end, I think you did indeed figure it out. For, the pieces are indeed not evenly thin enough to be dorsal vertebral processes (nor is the smaller straight enough, with its bump). They are also way to big to be phalangi, nor would there be such a difference in thickness between opposite ends of a phalanx. That is, while phalangi do get thinner towards the end of the hand, this is an even thickness and coincides with the other proportions also getting smaller. I don't see this being a podial bone either, as carpalia/tarsalia in plesiosaurs are disk-shaped and would be much smaller in mosasaurs.

 

Why I wanted to do some research before replying was to figure out the age of the Cretaceous sediments between Dakhla and Boujdour, may be some data on the different types of conservation encountered there. To the best of what I was able to find out (which was actually not a whole lot), Cretaceous fossils from the area are dated to 100 mya, placing them right at the Albian-Cenomanian transition - which would make it too early for mosasaurs. In other words, we're dealing with either still an early whale/basilosaurid or with a plesiosaur.

 

I must admit I had some trouble figuring out the taper in the bone, but then realised, much like you, that it can only be a rib. The rounded proximal end of the larger specimen initially made me think of the depressions ventral to caudal vertebrae to which chevrons attach. But, obviously, this is not possible seeing as those bones bifurcate. This makes the otherwise straight caudal ribs the only logical choice.

 

Whales have these too, though, even if not all of them do. Being a basal species, however, it seems Basilosaurus did have caudal ribs (specimen from the Muséum national d'histoire naturelle; source):

 

 

Conservation of your fossils doesn't seem to match those of the Eocene specimens coming out of the region, though, so it's quite possible that your pieces are indeed Cretaceous in age. I haven't seen too much Cretaceous vertebral material from the Western Sahara, though, so don't know how it compares. But, probably, plesiosaur caudal ribs is just about right

[Mahnmut]

Thanks for taking the time!

I just stumbled across the matching picture by luck, and it is a small picture. But your analysis makes me really confident that we got this riddle solved.

And nothing to be sorry about, if you take your free time to help me, take as much as you want!

à bientôt!

 

[pachy-pleuro-whatnot-odon]

For what it's worth, here's a picture of the rear section of Peloneustes philarchus from the Naturmuseum Senckenberg in Frankfurt, showing some more caudal ribs:

 

[Boesse]

So, if these fossils are Eocene, metacarpals/phalanges of a basilosaurid are certainly a possible ID. Here are the manus elements of Cynthiacetus peruvianus (left) and Dorudon atrox (right), and note that we're missing most of the phalanges here:

[Mahnmut]

Thank you @Boesse

I see the similarity. Assuming the seller got at least the age and class/order of vertebrate right, a phalanx would surely be the best match.

The very flat cross-section, sharp rim around the thicker (proximal) surface and flat distal end make me think that it is indeed a plesiosaurid rib, either cervical or caudal.

The colour also matches well with other plesiosaur fossils from the region I have seen, for what its worth.

Best Regards,

J

[Boesse]

Indeed, basilosaurid phalanges are not quite that flattened, and typically slightly cylindrical.

[pachy-pleuro-whatnot-odon]

56 minutes ago, Mahnmut said:

The colour also matches well with other plesiosaur fossils from the region I have seen, for what its worth.

 

You've actually seen more Western Saharan plesiosaur material? I've only ever seen one teeth, and then these pieces - so to me WS plesiosaurian remains seem quite rare. Would love to learn more about them, though...

[Mahnmut]

Hi Alexander,

sorry for my imprecise words.

 Sadly It is not as if I had much experience with western saharan Plesiosaur bones. By region I  meant to say north Africa, which is all I think I know about the abovementioned bones' origin.

I once saw a north African "paddle bone" of the typical hourglass-shape that was to expensive for me at the point and I remember it as brownish. The eocene bones I have seen from north Africa are mostly white (as are many cretacious ones, now that I think about it). Actually the colour of my rib more or less matches the relatively common Zarafasaura teeth- that are not a good reference for bone though.

Salut

J

 

[pachy-pleuro-whatnot-odon]

Hi Jan,

 

Yeah, Zarafasaura-teeth would indeed not make good comparisons in terms of preservation, as bones from the Moroccan phosphates are typically white in colour and rather soft, with teeth being preserved in a yellow-brown to deep-brown tone. I'm guessing, from what I've seen from the Eocene phosphatic deposits, that younger/Eocene deposits in Morocco are not much different. However, further back into the Cretaceous, preservation is markedly different, with bones from Goulmima (whether plesiosaurid, mosasaurid or otherwise) being solid with a reddish-brown to dark-brown tone., which seems very similar to the one seen in the first photographs you showed. The deposits there, however, are Turonian, whereas those of the Western Sahara seem to be slightly older at their Cenomanian age. Still, I think this would make a better analogue than the Maastrichtian material coming out off Morocco. Then again, preservation in the area around Arzou and Bakrit is completely different from either of these again, even when one discounts the black colour one might expect from an oil "shale" - but that's probably exactly due to the different type of matrix and the way that came about.

 

Cheers,

Alexander.