Echinoid - What are these fish-like details?

[jim_u]

Hello all! I recently moved into a fossil rich area and have found myself coming home from beach walks with arm-fulls of interesting rocks. I am still very new to this!

 

Most of my finds have been echinoids and sponges (sometimes both in the same rock!). However this guy, while obviously an urchin, is still somewhat of a puzzle.

 

The Details

• This was found on the beach near Saltdean, East Sussex, UK. That means it is likely late Cretaceous.
• The area is a couple of miles west of Peacehaven, home to several giant Parapuzosia ammonites, and a much richer seam of google hits / background information
• I found the fossil in a large chunk of chalk (photo #3). This is my first time extracting and cleaning a fossil. I mainly used a dental pic, tootbrush, water and a little distilled vinegar.
• The echinoid is about 5cm in diameter

 

There are two features I would appreciate your expertise in identifying:

1. The pale whorl of scales, which to my eye doesn't follow the natural shape / contours of the echinoid
2. The small fin-like feature most clearly seen in photo #2

 

Thanks in advance!

 

Photo #01

 

Photo #02

 

Photo #03

[Al Dente]

The first photo shows a bryozoan colony on the echinoid, the second looks like a brachiopod.

[Tidgy's Dad]

Yup. 

Very nice find. 

Hello, Jim, and a very warm welcome to TFF from Morocco.

[Bronzviking]

Welcome to the forum from sunny Florida! Nice job cleaning. I agree with bryozoan colony and a possible bivalve mold vs brachiopod. With only one valve showing it's hard to say for certain.

[jim_u]

Thanks guys! Fascinating stuff - I would never have made the google leap to bryozoan colony.

 

With regards to the second feature, the possible bivalve/brachiopod - are there any other details I should be looking our for?

 

[abyssunder]

I vote bryozoan and barnacle attachment scar for what is visible in the picture below.

 

comparative picture from here

[DPS Ammonite]

The attached shell could be a pecten relative, (Plicatula?)Some pecten type shells cemented themselves to a substrate. Bivalves were much more common that brachiopods during the Cretaceous.

[Ludwigia]

Welcome from Germany. I'm also tending towards pecten bivalve.

[jim_u]

RE the second feature, here are a couple of extra photos. Photo #04 shows a slightly different angle, allowing a view underneath the cracked test. Photo #05 shows a mark on the opposite side of the fossil. I hadn't posted this before, but abyssunder's post made me think that it might be relevant.

 

Photo #04

 

Photo #05