Chinese Fish or Plesiosaur Teeth?

[Alston Gee]

Hi everyoen,
 

My friend excavated two tiny tooth fossils from the Baitianba Formation (spanning from the Hettangian to Toarcian), Guangyuan, Sichuan, China, a few years ago. I acquired these two teeth last month and had the opportunity to examine them closely. I found that the teeth were roughly 7-8mm in length and exhibited unique striation patterns on their enamel. The two teeth from the Baitianba Formation share some similarities with plesiosaur teeth discovered in Woodbine, so I am wondering whether these two teeth might belong to a fish, plesiosaur, or something else.

[Kikokuryu]

The tooth in the first picture looks like it has a distinct carinae which makes me think it's some kind of thalattosuchian / marine croc. But it could just be the lighting or angle.

[Alston Gee]

6 hours ago, Kikokuryu said:

The tooth in the first picture looks like it has a distinct carinae which makes me think it's some kind of thalattosuchian / marine croc. But it could just be the lighting or angle.

Agreed! The presence of carinae clearly marks it as a freshwater croc tooth. However, I am uncertain whether the ridge running vertically along the middle of the tooth is an apicobasal ridge or carinae. If the first tooth is from a croc, isn’t it too slim?

[Kikokuryu]

3 hours ago, Alston Gee said:

Agreed! The presence of carinae clearly marks it as a freshwater croc tooth. However, I am uncertain whether the ridge running vertically along the middle of the tooth is an apicobasal ridge or carinae. If the first tooth is from a croc, isn’t it too slim?

 

These weren't conventional crocs like we know them today, or deeper into the Mesozoic. Thalattosuchians do have quite slender teeth. And some morphologies originally considered to be pterosaur or marine reptile around this time period (Lower to Middle Jurassic) have been reclassified as thalattosuchian.