Cretaceous Guitarfish anatomy has interesting pigmentation

[Biotalker]

I acquired this cretaceous guitarfish, Rhinobatos whitfieldi from Hgula, Lebanon. Although incomplete, it has exceptional preservation. Below is a picture of the fossil and a second image with angled light, showing the texture of the fossil surface.

[Biotalker]

The nice preservation is illustrated by the placoid scales and cartilage in the rostrum and ray edge.

[Biotalker]

Since rays are so flat, the fossil presents certain aspects of its anatomy more clearly than other vertebrates. In these images below, you see the viscera divided by the pectoral girdle into anterior and posterior compartments. In general, the anterior region has respiratory, circulatory and central nervous system organs (blue circle) whereas the posterior cavity has digestive, excretory and reproductive organs (red circle).

[Biotalker]

In the area where the large (and oily) liver would be, just caudal to the pectoral girdle, I see a pink color within the fossil. I have looked at many rhinobatos pictures online and I do see darker coloring very often when that compartment is well preserved.

 

Examination of the pink color reveals red particles within the fossil matrix. Under 95X which is the limit of my scope, these particles can be clearly seen compared with a part of the gut without pigment.

[Biotalker]

Removing some fossil matrix from the pigmented and non-pigmented area of the gut area and spreading on a slide suggests the pigment is not just on the surface but also deep.

I’m not sure what this observation may mean but given the remarkable preservation of soft tissues in these Lebanese layers, there may be an interesting story here.

[rocket]

Sometimes the lebanese fossils do really have an incredible preservation..., thanks for showing your specimen

Hard to get better or similar ray or sharks from other sites in the world... When I compare it with Solnhofen-sharks or rays the lebanese mostly have the better preservation

[ynot]

Nice fossil

The coloration where the liver was may be caused by a higher concentration of iron in the organ during life. - Just a offhand thought.

[NickG]

Get a UV lamp!

[Biotalker]

On 7/13/2024 at 8:08 PM, ynot said:

higher concentration of iron in the organ during life.

I agree, without further tests, iron is probably the most likely cause for the color.

[Biotalker]

On 7/15/2024 at 8:46 PM, NickG said:

Get a UV lamp!

OK, done!

[NickG]

Nice! Do any more details pop out if you change your lighting angle?