I found these fossils in the lower Fillmore Formation (Stairsian Stage, Ibexian Series, Ordovician System...about 490mya). This would be about the time of the first great expansion of the Nautiloids. I believe they are the fossilized siphuncular deposits of endocerids called endocones. I havent been able to see any trace of septa or camera so I am not completely sure.

Another Endocone photo, and some trilobite parts from the Mississippian part of the Pilot Shale.

And finally, some photos of the Great Western Desert.

fascinating pictures. I'm a nobody when it comes to the science, but it's really interesting to see that trilobyte head. It doesnt look like it's been dead that long
Can you tell whether it's a molt or the actual creature?

Stunning images and fossils, Kevin. :notworth:

Is that trilobite Phillipsia? I'd imagine it was a Proetid trilobite but I'm really not sure....

:shock: Awesome pictures! :D

Thom,
The trilobites are molts, they are covered with a fossilized algae that grew in concentric rings around things on the sea floor, resulting in a rock called an Oncolite. To find fossils at this locality, you sit and crack about 50 oncolites to find one or two fossil trilobites, and about 10000 to find an ammonoid (I have only found one).

Phil,
I thought they were either Phillipsia or Griffithides, I posted pictures on a trilobite group, and got a good reference to an updated ID, they are Pudoproetus. :trilobit:

Here is another orthocone I found the other day. It looks like the siphuncle has been silicified but the rest has not, you can make out the faint outline of the chambers on either side.