Trilobites lived in our ancient seas in both shallow and in deep water. These Benthic (bottom dwelling) creatures are ancient ancestors to creatures living today such as the crab, horseshoe crab, spiders and lobsters. They existed from about 525 million years ago to about 250 million years ago. That is approximately 275 million years that Trilobites roamed the ancient seas. In relation to the geologic scale that would be from the Cambrian to the end of the Permian Periods. Trilobites are excellent for these time periods due to their far ranging existence, abundance and specific paleo-environment. There are approximately over 20,000 species of trilobites discovered so far that have been scientifically documented. The number can only rise as new excavations and discoveries are constantly being conducted around the world.
Most trilobites lived in the ancient shallow seas that covered most of North America as well as other parts of the world and were bottom dwellers (benthic). Typically bottom feeders, some scientists believe as does this writer that these creatures were the bottom cleanup crew for the ancient ocean floors. I can almost picture a dead fish or other creature laying on the ocean floor and a swarm of trilobites covering this creature and consuming its flesh to the bone. In my opinion this theory makes sense. To sustain the vast number of species that existed at any one point in a geologic period and the sheer number of trilobites found in specific dig sites must require an abundant and sustainable food source. Perhaps they feed on other creatures as hunter or perhaps each other? In short they could be classified as scavengers and/or predators. Due to their small size, perhaps they also ate small food particles that constantly rained down on the ocean floor as well as microscopic creatures. Good candidates for this likely food source were probably microscopic creatures like forams! (See our section on forams).
A typical characteristic and position of trilobite fossils are that they are balled up. This posture was probably a defense mechanism. Like the woodlouse of today or what some call “roly polys” or what we used to call “bally bugs”. They ball up when touched or attacked. There is also evidence that Trilobites burrowed themselves into the soft shallow mud on the ocean bottom as protection. Many trilobite fossils have been found with their pleural field or back sides missing. Indeed most fossil specimens are in that condition. The pleural field which may have been a soft or “edible” section of a typical trilobite was actively pursued by the formidable predator the Eurypterids (sea scorpions) (Our next section).
Facts about Trilobite Fossils
Trilobite fossils have been found on every continent on earth. They ranged in size from under 1 inch to over 2 feet in length. The number of trilobite species discovered and scientifically recorded is a staggering 20,000 known species. Although most species were salt water specimens some species may have existed in fresh water as well. They make excellent index fossils for geologic time periods. They were probably both scavengers and perhaps some species were aggressive predators or even cannibals. Their body was comprised of segments and consisted of a hard shell like substance called Chitin, very much like crabs, lobsters and scorpions of today. Like crabs, lobsters and scorpions they shed their exoskeletons and molted during their growing periods. Trilobites had in some species complex bulbous eyes like the beautiful Phacops rana. There is evidence that prehistoric man collected trilobite fossils as well. Trilobite fossils have been found in ancient burial grounds dating back to more than 50,000 years. The following fossil Trilobite photographs are just a few examples of their simplistic design, beauty and progressive evolutionary development and complexity from the Cambrian to the Devonian Periods. (to be posted) Notice the Cambrian fossils are simplistic in design then notice the development of their eyes, spiny appendages and an overall more complicated development. Evolutionary processes at a glimpse!
- Trilobites from the Cambrian
- Ordovician Trilobites
- Silurian Trilobites
- Devonian Trilobites
I have been fortunate to live in New York State where Trilobite bearing outcrops are present along some major highways, minor routes and roadways. Through field trips, camping and fossil hunts with just a short drive up the NYS thruway are outcrops of Trilobite bearing rock. What a personal thrill it is to park on the side of the road and spend a few minutes selecting a likely layer of shale and start probing. The moment you split open a slab of black layered shale, a product of an ancient muddy bottomed sea and uncover a perfectly preserved trilobite still amazes me. What is fun and amazing is that you would be the first and only human being to ever see this creature after millions and millions of years. Hope you enjoyed our brief glimpse into the world of Trilobite Fossils.
Our next interesting section is Eurypterids or sea scorpions. A formidable predator that that in some cases grew to over 8 feet long, lived with trilobites in ancient seas and hunted, attacked and feed upon our friends the Trilobites.