Trilobites

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Above is an image showing the "typical" environment (constructed by me in Lightwave 3d) that trilobites once inhabited, sharing their waters with predatory cephalopods (the squid-like creature), crinoids (the flower-like creature to the right/foreground - relative of the starfish), and rugose corals (the anemone-like creature to the left/background). The particular trilobite species shown here is a Flexicalymene meeki.

Trilobites were an extinct group of Paleozoic arthropods, somewhat like a crustacean (i.e. crabs, lobsters, sowbugs, etc.), but more similar to modern-day horseshoe crabs. They are found in rocks ranging from the Cambrian to the Permian, with them being most common in the Cambrian and Ordovician, fairly common in the Silurian and Devonian, less common in the Mississippian, and rare in the Pennsylvanian and Permian periods. Their bodies are divided into three lobes lengthwise, hence the name tri-lob-ite. The central "spine-like" lobe is termed the axial lobe and the two side lobes the pleural lobes. The parts of the trilobite are termed the cephalon (head), a segmented thorax (middle), and pygidium (tail). In addition, the "nose" is termed the glabella, the "cheeks" are termed the librigenae if they are shed while molting and fixigenae if they remain affixed to the cephalon. The segments of the thorax are termed pleurae. Entire trilobites are relatively uncommon, due to the fact that exoskeletons when molted tend to break apart. Most often, an entire specimen found records the death of that individual (although there are species of trilobites where we have a significant number of preserved molted exoskeletons).

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Ceraurus milleranus. I collected this trilobite from the Ordovician Liberty Formation at Caesar's Creek, OH. The Liberty Formation is one of many formations collectively termed the "Cincinattian formations" owing to their proximity to Cincinatti, OH. Clicking the thumbnail on the right will yield a digital reconstruction of it. This particular trilobite is apparently quite rare in the area, so this represents a good find. The most common trilobite to the area is Flexicalymene meeki, but I did not find a single one of these relatively common fossils at CC. Note the forked pygidium, one spine of which is present in the original fossil.

Flexicalymene meeki. Flexicalymene meeki is probably the most common trilobite in the Cincinattian formations. Note how the two smaller ones are enrolled, in a posture believed to be used as a defense against predators, much like the modern, yet unrelated, pillbug or sowbug (Southerners call them "rolly pollys"). The smaller specimens were collected by Mike Perona at Caesar's Creek, and while I am not the actual collector, the days that I spent trying to collect these make me consider them to be my "just desserts" for all the time and effort spent trying to find them. The larger specimen measures about 1 1/4 inches long and has a rather interesting story behind it. On the way back from our trip to Ohio, my wife needed to nurse the baby, so we stopped at a nice roadcut about 12 miles from the KY border. I got out and collected for a few minutes while the baby ate her fill. While clambering up the side of the roadcut, I noticed to my left the back half of a nice Flexi, but without a front half to be seen anywhere, which was extremely disappointing, as Flexis were what I had hoped to find during our trip to OH. Well, as I clambered another 5 or 10 feet up, I noticed to my right the front half of a nice Flexi, which I judged to be from a different specimen. Back in the car, I wrapped the two halves up in a paper towel, and headed onward back to Tallahassee, FL (our fair city). At the next convenience store stop, I took them out and examined them more closely. Upon examination, I noticed too many similarities on the two halves to be coincidence and realized that I had both halves of the same specimen. Apparently, when it weathered out and went tumbling down the side of the roadcut, it had broken in half, with the two halves scattering in wildly different directions...or perhaps further weathering pushed them apart down separate avenues. In any case, the break was clean enough that they could be glued back into the one nice specimen that you see displayed here.

Elrathia antiquata. I collected this trilobite in March '96 from the Middle Cambrian Conosauga formation west of Rome, GA. This particular specimen measures about 8 mm from head to tail (or more correctly, from cephalon to pygidium). Note that this specimen is missing the free cheeks, giving the head a "sheep's head" shape. Evidently, this was a shed exoskeleton rather than the actual individual (although by now, the actual creature is dead, too). I penciled in (digitally--don't worry guys, I didn't destroy the fossil) the approximate position of the missing free cheeks. In addition to this one, I collected a larger specimen (about 1.5 cm long) of a heretofore unnamed species of Solenopleurella (this will appear on this page once I photograph and scan it), as well as five or six small assorted individuals under 2 mm long.

Another E. antiquata. Note how long and slender this specimen is compared to the "squatness" of the specimen above, leading me to believe that this was a different species than E. antiquata. Upon inspection by a professional (again, Dr. David Schwimmer), it was identified as an E. antiquata. This specimen was shown on a former version of this page as a Solenopleurella. Well, since then, I've found what appears to be the "real" Soleno...it will appear soon on this web page after more positive identification.

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