Help with sanddollar ID, please

[trilospain]

Hi all

 

 I search the species of these urchins. Thank you for your help!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[abyssunder]

Maybe this link helps a little : http://echinologia.com/galeries/echinarachniidae/index.html

Also here is a basic work : Hall, C. A. 1962. Evolution of the echinoid genus Astrodapsis. University of California Publications in Geological Sciences 40, 47-180, 44 pls.

 

[DPS Ammonite]

Your second sand dollar looks like a Dendraster species because it has an off center apical system with shorter petals on the side closest to the test edge. It may also be from California. Do you have an locality information?

 

Here's a good paper with with many photos of both Astrodaspis and Dendraster echinoids. Look at plates 17 to 24 for Astrodaspis and 25-36 for Dendraster echinoids.

 

CRETACEOUS AND CENOZOIC ECHINOIDEA OF THE PACIFIC COAST OF NORTH AMERICA

BY WILLIAM S. W. KEW

 

 

UNIVERSITY OF CALIFORNIA PUBLICATIONS IN GEOLOGY

Vol. 12, No. 2, pp. 23-236, plates 3-42, 5 text figures September 28, 1920

 

 

https://catalog.hathitrust.org/Record/100443917

 

Here is a photo of  Dendraster (Calaster) interlineatus (Stimpson) that occurs just south of San Francisco, CA in the Merced Formation:

[trilospain]

Thank you very much for reply.

 

Second urchin is a problem, I dont have any information about it, it is huge and I think it is a Dendraster (maybe venturaensis).

 

I will look those papers.