What Are Conodonts?
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You've seen Tyrannosaurus Rex and (admit it!) the part you liked best was -- the teeth. Maybe you saw "," in the Chicago Field Museum, purchased for 8.3 million US dollars at auction. Does discovering the toothy fossil of an ancient hunter seem like an impossible dream? Guess again. You might be surprised to find that rocks in your own backyard could contain tiny, ancient objects that are as vicious-looking as any Tyrannosaur jawbone -- and are ten times older.
These remarkable teeth belong to extinct marine creatures called conodonts. Tiny, jewel-like structures the size of a sand grain, these"cone-teeth" included the first cellular bone ever to be deposited in ocean sediments. Conodonts lived during the Paleozoic era about 250 to 500 million years ago, first appeared long before land animals, fish or other creatures with backbones. (Dinosaurs became extinct about 65 million years ago.) Conodonts may have been ancestral to modern vertebrates, and their teeth were complex structures that were clearly specialized for many different lifestyles, with durable chemical composition that allowed them to pass this tremendous span of time almost unchanged. Although complete fossils of the complete animal are quite rare, poorly preserved imprints suggest an eel-like creature with up to 7 different kinds of tooth element clustered together in the head to form a bizarre feeding apparatus unrelated to modern jaws. Conodonts may have been minnow-sized, with two large eyes, with chevron-shaped markings along the body suggesting muscle blocks found only in chordates. Although some researchers think conodonts may have been related to the hagfish or "slime eel," these creatures were quite different from anything alive today, and conodonts are still a major mystery to paleontologists.
One thing is certain -- conodonts lived on a very different kind of world. During the Ordovician era 450 million years ago when most of Nashville's sediments were deposited, the Earth's rotation was faster. The air had a different pressure and composition. The continents were arranged differently, with vast shallow oceans filled with a bewildering variety of strange organisms - thousands of species of filter-feeding, clam-like brachiopods amid crumbling islands of sponges and coral-like bryzoans. In other areas dense "flower gardens" of armored crinoids swayed gracefully in the currents. Bottom sediment was inhabited by burrowing worms, snail-like cephalopods and early segmented animals such as the extinct trilobites. The land would have been a barren, almost lifeless environment with very primitive mosses inhabiting low swampy regions. The wide variety in conodont teeth suggest that even at this early stage in the evolution of life, they were part of a complex ecosystem of predator and prey, although most of the creatures that made up their diet probably had soft bodies that left no fossils. Whatever their origins, these small, beautiful objects offer tantalizing clues about a world that seems as remote as an alien planet, yet is as close to us as the sand below our feet.
Some Interesting Questions About Conodonts:
How to Study ConodontsFind an outcropping of well-weathered rock that contains paleozoic fossils. Such rocks are abundant in many areas of the central United States. Many professionals use acetic acid to dissolve conodonts out of limestone. (Don't use hydrochloric acid -- it will etch and destroy the conodonts). You can buy inexpensive industrial grade glacial acetic acid and cut it to 10% strength, or just use vinegar, which is 5% acetic acid. (Use an area with good ventilation, and always use gloves and eye protection!) Break the rock into centimeter-sized chunks, and put the fragments into a small bucket with holes in the bottom and soak it in a larger bucket of acid for a few days. Then lift the bucket out to drain, pour off the liquid, and repeat the process. After a few weeks, you will find enough residue to sieve, clean and inspect.
Rock that has large fossils will probably find microfossils in it too. Productive residue should also contain other microfossils, such as tiny gastropods or shell fragments. Several small samples are best -- if you find just barren rock, go on to another sample. Keep notes to locate productive areas and then return for larger samples later.
I have had success simply scooping up samples of crumbling soil and limestone from old road cuts -- materials that are often rich in heavy conodonts that remain when lightweight clays have been washed away. Once you have obtained enough residue or sediment, it is time to pan for conodonts. You will need two screens - a wide 20 mesh and fine 80 mesh filters to sieve out the conodonts. You can buy suitable sieves (telephone the Carolina Biological Supply Company at 1800 334-5551 and ask for BA-GEO9310 for $28.00) but true-blue do-it-yourselfers can try using a fine mosquito screen as your coarse screen, and fabric from an old pair of women's nylon stockings as your fine screen. Stretch the fabrics over a couple of crochet loops, stack them together with the fine filter underneath and wash the sediment through the two filters using a gentle stream of water. (Be sure to do this outside so that you won't destroy your plumbing.) The evenly graded sandy material trapped between the two filters may contain conodonts. Collect about 50 grams of this material, dump it into a flask and and carefully flush off any organic material by repeatedly swirling and pouring. Clean and sterilize your sediment by boiling the residue for a few minutes in a flask with a few grams of dishwashing soap. Wash the material again by pouring the sediment over your fine filter and rinsing off the soap and clay. Then allow the remaining sandy material to dry.
Serious researchers can further concentrate their conodonts several fold by using heavy non-toxic liquids such as Sodium Metatungstate (About $230/kilogram from SOMETU-US at telephone number 1818 786-7838) to float off the lighter parts of the sediment inside a funnel. When you are ready to look for conodonts, sprinkle the dried material into a thin layer on a card, and scan it under the microscope. You will get best results with a binocular dissecting microscope that allows you to inspect large areas of sediment, brightly lit from above. Improve your efficiency by sticking a piece of graph paper to the card so you can scan systematically. If you have picked productive rock, you should find a tantalizing assortment of tiny snails, bits of bryzoan, silica micro fossils and small bits of inorganic sand. If conodonts are present, you should begin finding them within 15 to 20 minutes. A spoonful of material can contain hundreds of conodont elements -- but similar looking rock only inches away can be barren of specimens. A good way to file your collection is by using paleontological micro-slides, which are available from the address below:
Use a fine, slightly moistened paintbrush to pick up the conodonts, and touch the brush to small cardboard slides lightly coated with diluted white glue. Like snowflakes, each conodont is a unique and fascinating sight. You are looking at the teeth of an animal that roamed the warm seas a half billion years ago!
About this WebsiteAlthough museum-quality fossils are out of reach of most of us, conodonts are often easy to find and fascinating to study. After discovering them in the soil of my own yard here in Nashville, Tennessee, I have decided to make their study a hobby, use this website to organize and display my collection. The images prior to 1995 were were taken through a Wolf dissecting microscope, using a Sony High-8 videocamera. The specimen was illuminated by two 100 watt spotlights. The video image was then converted to digital format using a Snappy by Play Inc. The images were cut out and reprocessed using Aldus Photostyler. Stereo images were made by rocking the specimen by about 12 degrees and making a separate picture. Later pictures use a JVC DVL-9000 digital videocamera and a Bauch & Lomb Stereo-7 zoom dissecting microscope using a fiberoptic ring, and taking specimens under oil immersion. Most recently, I have started using a Sony DSC-S70 digital camera. Over the years I have gotten many visitors who have looked for conodonts -- some are disappointed that they seem small and hard to find. However, the quest for conodonts is a great and inexpensive project for anyone with an interest in the past, and makes a good high-school project for classrooms. Your comments and contributions are welcome.
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