Microvertebrate Remains From South East England

[quagga]

Hi

I've been sampling some Wadhurst clay (from East Sussex) for microvertebrate remains, and have made some interesting finds, particularly from sharks, bony fishes, and crocodylians.

Here is a nice Lonchidion crenulatum tooth, as an example:

(scale bar 1mm)

I have recently started to break down some Purbeck group limestone rock (also from East Sussex) that has obvious vertebrate remains, and as well as some nice pycnodont teeth, have found this:

(scale bar 5mm)

It looks a little like a fragment of tooth plate, but I have never seen teeth of that shape. Does anyone have any ideas?

[Auspex]

Early Cretaceous; how interesting!

I can offer nothing more on the second bit, other than it seems you are on the right track.

[Al Dente]

Those are nice clear photographs. I think you second fossil is a dermal plate or denticle from a fish or shark. I have similar from Cretaceous and Eocene sediment.

[Al Dente]

Here are a couple from the Eocene of North Carolina that I think are similar to your find. They come in all different shapes and sizes.

[Mike from North Queensland]

I find similar here in Australia from the cretaceous except they are smooth both sides. I always assumed fish scales.

Mike

[quagga]

Thanks for your interest and replies, I have been reliably informed that it is a water worn fragment of pycnodont tooth plate.

[jpc]

Do you have gar scales in oyour sample? I think the second one is one of the odd scales fprm a gar, or a piece of fascial bone from said predatory fish.

[quagga]

There are semionotiforme ganoid scales present in the sample. These most probably belong to Scheenstia sp. (formerly known as Lepidotes).

[Coco]

Ah ? Lepidotes has changed of name ?

Coco

[Al Dente]

Here is a drawing of Cretaceous fish scales from an old paper that look similar to yours (#2 in the illustration). I'm certain your fossil is not a pycnodont tooth plate.

The paper is titled "On some Fossil Fishes discovered by Prof. Ennes de Souza in the Cretaceous Formation at Ilheos Brazil"

Edited December 16, 2014 by Al Dente

[squali]

Nice material your finding, hope to see more.

I agree it's not a pycnodont tooth plate. Your observation on the odd 'teeth' shape is accurate because they aren't 'teeth'

[quagga]

Ah ? Lepidotes has changed of name ?

Coco

Yes Coco, Cretaceous Lepidotes (eg. Lepidotes mantelli) is now Scheenstia. See Lopez-Arabello Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterigii)

[quagga]

Squali & Al Dente, you both seem certain that it is not a tooth plate, yet since posting this image here, I have been reliably informed by someone that studies this kind of material that it is a water worn fragment of pycnodont toothplate. I trust their judgment as they research early Cretaceous vertebrate microfossils.

I see what you mean about the rugosity of the surface of some scales, particularly around the eye, however, those scales are completely covered with ganoid, not broken into discrete blobs. The frontal bones of Sheenstia mantelli also have a knobbly surface, but these are entirely bone with no ganoid (The fossil fishes of the English Wealden and Purbeck formations). I have collected many scales, and none have the texture or thickness of this specimen.

I have seen some images of water worn pycnodont tooth plates (English wealden fossils - The Palaeontological Society) which start to show some similarity in tooth shape to this.

Although I am not averse to other suggestions, I am rather surprised at your certainty.

[Al Dente]

The pychnodont tooth plates that I'm familiar with all have teeth in rows, the teeth are somewhat round or long ovals when viewed from above, and they are raised above the bony plate. I don't see these features in your fossil. Here is an example to show what I mean.

[squali]

quagga, I'm far from an expert on these things but I have had several pycnodonte mouth plates in hand

and I don't recognize the 'tooth' shapes I've outlined in your excellent photo.

Also, the round objects seem hollow in the middle like a doughnut.

The teeth I am familiar with are domed and not cupped.

The 'tooth' spacing seems too erratic for a mouth plate intended to crush food.

The plate itself does not appear like 'bone', even if it is worn there should be some pores visible.

All of that being said, I won't swear to anything.

[quagga]

Squali, the domed objects are not hollow, that is an artifact of the lighting. That said, I have seen plenty of Pycnodontiforme teeth with an indentation in the top and a crenulated rim. These are not the usual bean shaped teeth, but smaller tear drop shaped teeth. (see attached. Scale bar 1mm).

I hope to get someone at NHM London to take a look at this specimen. I'll post their response when I get one.

Edited December 23, 2014 by quagga

[MarcoSr]

I look forward to hearing what the NHM London has to say. I don't think it is a tooth plate either but believe it is a fish dermal plate (skull fragment) or denticle/scute/scale.

Marco Sr.

[squali]

It's good to get an in hand opinion when you still have doubts.

For my money, if Al dente and Marco Sr. share the same opinion

you have your answer.

[MarcoSr]

It's good to get an in hand opinion when you still have doubts.

For my money, if Al dente and Marco Sr. share the same opinion

you have your answer.

Thank you for your vote of confidence. I spend time on TFF to help but also to learn. So I am very open minded to what the NHM London has to say.

Marco Sr.