Differentiating Rays?

[gdarone]

Hi.

Each time I visit Calvert Cliffs I manage to come home with several more "better" specimens of ray plates. It would be great if I could sort them a little better

I know identifying ray plates is difficult, so maybe this is a lost cause, but I thought someone on TFF might have some knowledge on this better than what I've found on the internet. Frankly, when I look at photos of ray plates in text books and internet resources, they often look the "same" to my eye.

Aetobatis sp. is easy to pick out - it is V shaped. No worries on those ID.

Does anyone know a way to differentiate the other genus? How to tell between Myliobatis sp. and Aetomylaeus sp. ?

The above fragments all look different, so are there any diagnostic features that could help in IDing them?

Thanks for any insights.

[Coco]

Hi,

For several years, Henri Cappetta (French specialist of the world selachians) says that we can't name a fossil ray tooth from the moment it isn't any more attached to the puck with the other teeth. Indeedi, when we compare jaws of current ray, several species have the same type of teeth, but rows are in different numbers, it explains why and individual tooth (of ray with teeth as yours) can't be named. But you are right for Aetobatis (perhaps A. arcuatus if Miocene).

Coco

[gdarone]

Thanks Coco. I figured that might be the reality.

[MarcoSr]

Aetobatis sp. is easy to pick out - it is V shaped. No worries on those ID.

cal 11.jpg

.

The individual teeth from an Aetobatus lower dental plate are V shaped. The individual teeth from an Aetobatus upper dental plate are not V shaped. See below for an example from the upper dental plate:

Marco Sr.

[gdarone]

The individual teeth from an Aetobatus lower dental plate are V shaped. The individual teeth from an Aetobatus upper dental plate are not V shaped. See below for an example from the upper dental plate:

Aetobatus sp.2 15mm.jpg

Marco Sr.

Hmm.. well, I guess if it is V shaped, I can say it's aetobatus lower plate. However, there are likely some of my "unsorted" non-V shaped fragments which are aetobatus upper plates.

[MarcoSr]

Hmm.. well, I guess if it is V shaped, I can say it's aetobatus lower plate. However, there are likely some of my "unsorted" non-V shaped fragments which are aetobatus upper plates.

It is difficult to identify individual teeth from a ray dental plate to a genus/species. There are some features of the teeth that do help. If you look at modern ray dental plates there is a lot of variation (in the number of rows of teeth) within a species and overlap between species with individual teeth that are very similar.

Marco Sr.