Mystery Fossil

[Monty Grover <grover@xxxxxxxxxxxxx>]

Just to change the topic completely, we have found an imprint of a fossil
dating from between Devonian to Cretaceous in age (I know, that is a
massive amount of time) and most likely Cretaceous in age which we have not
been able to identify. 

The attached image is at a scale of 1:1 and it occurred in a fine siliceous
sandstone from the North of Northern Territory, Australia, in a kimberlite
region.

Any suggestions as to order, genus and/or species would be gratefully
accepted. Answers can be posted here, or sent to me personally if you don't
like airing your "guesses" out in the open

Thanks in advance

Monty