Crab Preparation

[snolly50]

Which way is up? Is there any convention for guessing which way a crab is oriented within a nodule? It would be desirable to prep "down" to reveal the carapace, leaving the ventral aspect encased in the matrix. But which surface is the correct one? Of course, the "right" choice is a 50/50 shot, but is there any way to improve those odds?

[steelhead9]

Usually the concretion is somewhat oval, so I usually open them by using the widest point of the oval as a start. I then use a thin diamond blade to score all the way around the oval, then crack it open with a chisel. Once open, you will see the orientation of the crab. Use whatever marking system you like, mark the outside, and glue the concretion back together. Now you know where to start working down to the crab. Works for me!

[DLB]

Well there's a couple of ways,break it ,orient and glue go off the shape and take a50/50 chance it u have one I would do the 50/50 if u have lots go with breaking it cuz it takes a long time to scride them out if there a big nodule.

[jpc]

My friend Bruce whom we haven't seen here for a while, digs a deep yet narrow diameter hole into the center of one side or the other until he finds the crab. (Air scribe) Once there it doesn't take much to tell if you are looking at the top or the bottom. If it is the top, keep going. If it is the bottom, turn it over; the hole you have already made is small enough that it will not show in the final project.

[snolly50]

Thanks to all for sharing their experience. I've prepped many different types of fossils, but never a crab in a nodule. Now I will be a little more confidant. I think this forum is great.

[Boneman007]

Your question has a different answer depending on the crab species, and depositional environment.

With Notopocorhystes dicrous crabs from the Britton formation of the Eagleford group, turonian, crabs can be in the nodules in a number of configurations, depending on whether it is a molt, and whether the lower carapace sepearates completely from the upper carapace.

Edited January 28, 2013 by Boneman007

[bone digger]

Hey Snolly, here is a website that was put together by micropterus101. He shows how crabs are usually orientated within concretions. Sometimes however the concretion is just to round to hazard a guess. Good luck on your prep! www.fossilcrabs.com\information.htm

[snolly50]

bone digger, thanks for the helpful site tip.

[CH4ShotCaller]

Hey Snolly, here is a website that was put together by micropterus101. He shows how crabs are usually orientated within concretions. Sometimes however the concretion is just to round to hazard a guess. Good luck on your prep! www.fossilcrabs.com\information.htm

I met Micropterus and DLB on a couple hunts, the web site is a good tool for orientation, etc. Plus, they demonstrated the orientation and a few other methods that have worked great for me. Just a few hours with them has increased my prep skills 10 fold. The web site is a very useful tool.