One for the (marine) crocodile specialist...

[pachy-pleuro-whatnot-odon]

Hi everyone,

 

Recently, while researching the morphology of machimosaurid crocodile teeth, I bumped into the below specimen, identified as Machimosaurus hugii (presumably based on its size). And although I can't confirm the specific name, I'm confident the referral to Machimosaurus is correct.

 

 

When taking a closer look at the tooth's striations, however, I noticed not all of them actually run the whole apicobasal length of the tooth as I expected. And although some striations have undoubtedly been terminated and/or interrupted by wear, I was more genetically wondering if striations not running the full apicobasal length of the tooth is a know characteristic of crocodile teeth.

 

For I'm only familiar with teeth that are either entirely smooth, or that have fine striations on one or both sides of the tooth, where only those striations that run into one of the tooth's carinae may be truncated before reaching the full apicobasal length of the tooth. That having been said, though, I can imagine crocodilian dental ornamentation being more varied, with different patterns of organisation in their striations, as Madzia (2016, A reappraisal of Polyptychodon (Plesiosauria) from the Cretaceous of England), in an annotation with his figure 8 illustrating pliosaurid tooth crown morphologies following Tarlo (1960) (reproduced below), observes that the teeth with the most striae, previously referred to Simolestes nowackianus, are now considered Machimosaurus nowackianus. And with the great variation of expression in striations on pliosaurian teeth, I don't think it would be such a leap to assume the same for this species of teleosaur...

 

 

So, my question is: are striations on crocodilian teeth as variable as they are amongst pliosaurs? Can individual striae end prior to stretching the full apicobasal length of the tooth, and, if so, in which clades or under what conditions? Do crocodilian teeth exhibit patterns of striations of interchanging lengths (e.g., short-long-short)?

 

Thanks for your help!

[pachy-pleuro-whatnot-odon]

Could I ask your opinions, @Jesuslover340, as the author of the excellent guide on alligator vs. crocodile tooth identification, and @caterpillar, for your general knowledge on crocodilians?

[caterpillar]

As I know, yes, crocodilian teeth have variable striations.

You can read this paper. Maybe you will find some informations

http://www.dinosauria.org/documents/2015/buchy_oryctos9.pdf

Sorry it's in french

[pachy-pleuro-whatnot-odon]

Thanks! And no need to apologize! I might not get through it as fast as in another language, but it seems like a very interesting article to read.

 

I'll see if I can report my findings back here afterwards. Though that might take a while, as I've got quite a bit of literature still lined up

[caterpillar]

Ok, good reading

[Jesuslover340]

Hmmm....good question. Variable striations,  absolutely, but variable striations with some terminating prematurely I myself have not come across  I checked my collection and even modern C. porosus skulls and those with striations all run the full apicobasal length, but of course, take that with a grain of sand as my collection is by no means comprehensive. 

[pachy-pleuro-whatnot-odon]

Thanks for sharing your insights! I guess I'll just have to check the above article to find out whether that answers my question

 

Thing is, I received four marine reptile teeth before Christmas that were supposed to be plesiosaurian teeth. But when I received them, it turned out they've got carinae, and look much more like teleosaurid crocodilian teeth. However, certain characteristics don't match up with that hypothesis either - not to mention one of them comes from Lavernock (the others are Oxford Clay from the Peterborough area), from the Terminal Triassic to Earliest Jurassic, and thus from a time that knows a paucity (if not total lack) of thalattosuchians. I took some photographs and still intend to post them on the Fossil ID board, but wanted to educate myself a bit mor beforehand (will refer to it here when I do, if needed).

 

One of the teeth seemed to lack carinae, and has a distinct pattern of striations that seems to match that of Peloneustes philarchus, so that I initially identified it as such - or possibly an ancestral species, as it dates to the Callovian Jurassic, a time from which P. philarchus is not known. However, even recently re-examining the tooth, I spotted something that looks a lot like a carina (though it's hard to say for sure with the tip missing), and have now started doubting again, especially as the tooth looks nothing like the other tooth in my collection I've currently got marked down as P. philarchus from Peterborough. Below is a photograph:

 

 

And, for comparison, a schematic drawing of pliosaur tooth morphotypes following Tarlo's 1960 A review of Upper Jurassic pliosaurs, with the type attributed to Peloneustes to the right (F).

 

 

And just for good measures, the two others from the same batch (the fourth, as said, comes from a different site) - though the last image, unfortunately, isn't sharp enough to show the striations on that tooth...

 

[pachy-pleuro-whatnot-odon]

On 1/16/2021 at 6:34 PM, pachy-pleuro-whatnot-odon said:

Hi @paulgdls,

I think the above tooth might be either Peloneustes philarchus. Can I ask you for your opinion? What do you think? Does this look like a small pliosaurian tooth to you - and does it match Peloneustes' ornamental morphology? It seems very close to what Tarlo (1960) describes...