Did You Know?
Most animals during the prehistoric age, unfortunately, did not leave any fossils. Instead, they decayed completely, and were lost to the ravages of time. Researchers believe that the fossil records that are available today comprise only about 5-10% of the creatures that ever lived on our planet.
The word trilobite means 'three lobes'. This name refers to the description of the animal's body. All trilobites have three vertical lobes: the left pleural lobe, the right pleural lobe, and an axial lobe. The name is sometimes mistakenly attributed to the three horizontal sections of the head, thorax and tail.
All trilobites are arthropods, and because they look like hard-shelled insects, fossil collectors often call them 'bugs'. However, in actuality, these creatures are not related to insects, but they are distant relatives of crabs, lobsters, and spiders. There are no extant living beings that are similar to the trilobites. Fossils are found commonly across the globe, and since they are primarily associated to the period of the Pre Cambrian to Permian Age, they make very interesting studies for the Paleozoic era.
Physical Characteristics of Trilobites
The size range of trilobites was very extensive and they came in numerous shapes. While the smallest known specimen was just around 1mm, the largest specimen has been found to be over 2 feet in size. All trilobites had a thick exoskeleton for defense and a few even had intricately patterned spines, and long tails. Trilobites are also believed to have been one of the first creatures to develop compound eyes. Studies suggest that these creatures had numerous lenses in each eye, which were oddly made from crystal.
Like the modern pill worm, trilobites would roll themselves into a ball, to protect their vulnerable undersides, from predatory attacks. These creatures also molted their exoskeleton regularly as they grew, during which time they would be soft and vulnerable. In fact, most trilobite fossils found today are actually molted exoskeletons. The diet of these creatures depended on their species. While some were scavengers, others were filter feeders or predators, eating anything that was smaller than them, including smaller trilobites. The unique bodies helped these creatures to be the most successful animals to live on Earth. This can be seen by the fossils which date to before the Cambrian Period, through several mass extinctions, right until the end of the Permian extinction event. That's a total of nearly 300 million years!
Trilobite Fossil Information
Most trilobite fossils are over a million years old, so they have been commonly found and used as toys and decorative pieces by humans for thousands of years. However, the first proper scientific description was made only in 1689, by Wan Shizen of China. The first scientific diagram of a trilobite then came in 1698, by Rev. Edward Lhwyd in a book called 'The Philosophical Transactions of the Royal Society'. In the book, the trilobite was mistakenly called a flatfish. Over time, with an increase of interest in paleontology, fossils of around 20,000 species were documented.
Trilobite Evolution Timeline
While most fossils consist of just the hard exoskeleton, in rare cases, even the softer body parts, including the legs, gills, antennas, etc., have been found. Fossil records indicate that the first trilobites were soft-bodied creatures that slowly evolved shells as they transitioned from the Precambrian to the Cambrian Period. The Cambrian Period saw them multiply rapidly and dominate the seas of the Paleozoic era, diversifying into innumerable species as they evolved further―their body adapting to the environment of shallow reefs to abyssal depths of the ocean. The Ordovician, Devonian, and the Great Permian extinction events, eventually took their toll on these wondrous creatures, making them extinct. Fortunately for us, their exoskeletons survived as fossils, and we are able to enjoy and learn about the Earth that existed millions of years ago.
How a Trilobite Fossil Forms
A trilobite fossil is normally formed only if certain conditions are fulfilled. This includes sudden and permanent entombment of the creatures, with continuous addition of sediment without significant erosion, and a lack of oxygen, heat, and compression, which severely limits the decay. Due to the fact that trilobites existed across all the seas of the world, and also because fossils have a higher chance of forming underwater, millions of trilobite fossils are available today.
Trilobite fossils are some of the most well-preserved and beautiful collectibles in the world, and are sought by enthusiasts all over the world due to the fossil's unusual and interesting appearance. The innumerable species make a vast variety in their shape and color. Due to their abundance, paleontology enthusiasts can get them for affordable prices. So, keep your eyes peeled the next time you are on an excursion in the wild, you might just find yourself a beautiful piece of history.