Wednesday, February 18, 2009

Cryptolithus Head Plates

Here are several Cryptolithus sp.trilobite remains found in Carroll County, Kentucky. One still has part of its side spine intact. I have wondered what purpose this spine serves being so close to the body and swept back along the side. Is it possible the trilobite propelled itself backwards with its tail like crayfish do today? As if sped backwards this two spines would protect it if it hit something like a rock or hostile creature?

I also wonder about all the holes along the creatures front rim. Are these some sort of sensory mechanism? I have read this creature is blind so it either navigated with antenna or maybe used this hole system as some sort of detection grid. Of course if it lived in a dark environment, eyes are not really that useful.

This creature lived in the Ordovician period and is in the company of remains from bryozoans and crinoid stems.


MJMartin said...

The cryptolithus genus of trilobites is a trinucleid, a blind family of trilobites. The long sweeping spines, called "genal spines",served many purposes. First and foremost they would have been used to stabalize the animal as it moved about. Also, mose specifically to cryptolithus, they may helped in preventing the animal from being flipped over.

Backward propulsion, although an interesting idea, wouldn't have been effecient. first cryptolithus has a very small thorax and pygidium(body and tail), not nearly large enough to contain the muscles necessary to move the animal backwards in any useful manner(the head or cephalon in Cryptolithus typically makes up more than half of the entire body mass). The other issue with backward movement is the spines themselves. Going against aquadynamic shape of the genal curve would create suffucient drag as the spines wouls bend and flex in the current.

Most species of Cryptolithus may well have been mud dwellers.

Fossil Detective said...

Thank you for helping with my further understanding of the Cryptolithus trilobite.

I did not consider the spines would be used for stability. It makes sense with the creatures weight concentrated in the front.

A paper entitled Mechanics Of Escape Reponses in Crayfish (Orconectes virilis) by P.W. Webb, University of Michigan, School of Natural Resources contains an analysis of the crayfish and its backward swimming capabilities. It highlights that the crayfish telson and uropod make swimming possible. These parts of anatomy are missing on the Cryptolithus. See this link:

A recent paper in the journal Lethaia by Jan Bergström of the Swedish Museum of Natural History and University of Lund entitled "Appendage morphology of the Trilobite Cryptolithus and its implications", might shed some more light on how these spines were used. I could not find a free place on the Internet to access this paper though.