Modern day VS Cretaceous sand dollar

[mr fossil]

Left sand dollar is modern day 

I found in the Red Sea 

on the right is a fossil sand dollar I found embedded in limestone on dry land

this is all in Saudi Arabia 

when I checked the last time it was underwater was in the Cretaceous 

I want to know as much as possible about this 

both sand dollars are very different in size and shape 

for it to adapt this much it must be millions of years old

[Rockwood]

21 minutes ago, mr fossil said:

the last time it was underwater was in the Cretaceous 

I want to know as much as possible about this 

both sand dollars are very different in size and shape 

for it to adapt this much it must be millions of years old

Cretaceous would be 65+ million years old. They have been around that long for sure. It's plenty of time for evolution to wander in many directions.

[Rockwood]

34 minutes ago, mr fossil said:

I want to know as much as possible about this

Turn the clock back far enough and, being deuterostomes, these guys are some kind of cousin some number of times removed from us. 

[Al Dente]

The echinoid on the right looks like Laganum. Laganum depressum have been found in the Pliocene/Pleistocene of Saudi Arabia.

[Bob Saunders]

Here is a link to some fine images. 

 

http://bibliodyssey.blogspot.com/2009_01_25_archive.html

 

 

[mr fossil]

15 minutes ago, Al Dente said:

The echinoid on the right looks like Laganum. Laganum depressum have been found in the Pliocene/Pleistocene of Saudi Arabia.

hmm interesting i will check it out thank you

[Al Dente]

Here's a reference of a paper by Porter Kier. He calls the deposits Miocene and the species Laganum tumidum.

 

 

[Coco]

Recent one is Clypeaster.

 

Coco