Descendants (?) of I KNOW WHAT TRILOBITES ATE BY TERRANCE M. ALLEN, S.C.E. Usually oblong and attened, trilobites were shaped General Characteristics of Trilobites and Their more like today’s cockroaches, which too have fossil records dating back over 300 million years B.P. (Before Geological Time on Earth Present). But unlike their extinct relatives the trilobites, In the Kingdom trilobites are identi ed today cockroaches successfully continue living on Earth and placed into the Phylum: Arthropoda (Greek: in almost every environment. Scientists have discovered arthro=joint, pod=foot). Trilobites (Greek: tri=3, fossilized remains of dating back to 392 to 420 lobos=lobe; Latin: ites=fossil), known only from fossil million years B.P. Hence, insects, crustaceans, and other remains, existed hundreds of millions of years before may have evolved from early forms of the archaic arachnids and insects, ammonites (extinct trilobites. Insects, including cockroaches, would have marine mollusks) and nautiluses, and the ancient sh, lived concurrently during the trilobites’ prevalence for amphibians, reptiles, dinosaurs, birds, mammals, and Flexicalymene meeki feeding on two 170 million years. humans. Like today’s insects, the trilobites’ chitinous Brachiopods (only one visible) Like pieces of a puzzle, fossils and their associations exoskeleton, which was molted or shed at intervals for are valuable scienti c specimens and are indicators and growth and possibly regeneration, formed a jointed have developed from a single crystalline lense made of direct evidence as to the history and evolution of life body and limbs. They usually possessed multifaceted calcite over light receptive cells such as those found in on Earth. compound eyes and antennae, and many had external at worms, earth worms, and sea stars (aka: star sh). spines and/or projections. The segments of the trilobite Resembling a “honeycomb” pattern, these calcite Paleoentomologically yours, body were divided by longitudinal furrows on the crystalline lenses formed into a set of eyes. Through Terrance M. Allen, S.C.E. dorsal (top) surface into three lobes. Their size ranged adaptation and genetic modi cations and the from less than one-mm (1/32-inch) to one-meter (39- reproduction of the dominate keen-sighted survivors, inches) or more in length. the opposing eyes situated on opposite sides of the Trilobites made their grand entrance into the median lobe of the trilobite body evolved over time on Cambrian seas during the “Cambrian Explosion” of the cephalon (head) of the early trilobites. Although life on Earth; no life existed on the terrestrial lands as the eyes became characteristically dierent for yet. These primitive arthropods dominated the oceans individual species, the trilobites set the standard for the during the Paleozoic Era living from the Early Cambrian compound eyes found on almost all arthropods. Period to the Late Permian Period (544 to 250 million The ancient trilobite Xandarella sp. had bilateral years ago). They disappeared from the planet Earth symmetric prominent eyes probably brought on at the time of the great “Permian-Extinction.” To date, through visually-guided predation and/or foreseeable fossils of nearly 15,000 dierent species of trilobites evasion from other predators. The eyes of the trilobite have been identi ed. Trilobites too, like all life on Earth, Phacops were of the same design as today’s extant evolved from more primitive ancestors which insects, especially those of the Strepsipteran, Xenos also are preserved in the fossil record. peckii, a small beetle-like known as a twisted- Trilobites were marine or sea-living invertebrate winged parasite. The “bug-eyed” trilobites were now . They are more closely related to insects, also able to scuttle over the sea oor looking for crustaceans (pill bugs, sow bugs, and land crabs), something to eat. Today, the majority of all arthropods, and horseshoe crabs. Some could roll up into a like the trilobites, possess bilateral compound eyes, ball like a pill bug or an armadillo concealing their including all insects, except for the primitive proturans soft underbody and appendages. Their hardened along with a small number of species of other primitive Terrance M. Allen, Sacramento, California exoskeleton, sometimes armored with sharp defensive groups and some cave dwelling insects. Entomologist, Arachnologist, Practicing spines, provided protection against predators such as Paleoentomologist, and Factotum Naturalist; Anomalocaris canadensis and Eurypterids (aka: sea What Trilobites Ate In his home laboratory with 50k insects, spiders, and related arthropods, and over 2k fossils. scorpions), or even each other. Large, now extinct, Foraging or scavenging in the sand or silt of the sea Photo by Don Meuchel, May 21, 2014 Nautiloids up to 30-meters (90-feet) in length, related oor, trilobites probably fed on smaller organisms and to today’s surviving cephalopod mollusk Nautilus, also plankton and other sea plants. New evidence suggests History Summary for Terrance M. Allen includes: would have fed on trilobites. In the latter period of their they even fed on brachiopods (*), aka: “lamp shells.” earthly reign, the sometimes outlandish spines that Northwestern School of Taxidermy: Certificate & [New fossil evidence: two brachiopods being eaten by evolved over time also provided them protection from Diploma in completion of the Study of Taxidermy. a trilobite, Flexicalymene meeki (Foerste), discovered the huge predatory sh that ourished in the Devonian Long Beach City College and California State and extracted by T.M. Allen (February 2008); from University Long Beach: Associate in Science and seas. rock collected in Cincinnati, Ohio, U.S., from the Upper Bachelor of Arts Degrees with a Major in Entomology. Ordovician, 443-441 MYO (Million Years Old).] Or, like State of California Dept. of Health: Certified Trilobites Were the First Organisms to modern day insects, spiders, and other arthropods, Develop Eyes trilobites sometimes probably preyed upon and ate Technician in Mosquito Control. Although the earliest trilobites were blind as they others of their own kind. California State Dept. of Food and Agriculture: swam in the darkness on the sea oor, via evolutionary (*)Note: from the Cambrian Period to Recent times, Certified as Economic Entomologist and Pest law, mutations and/or adaptation, these aquatic brachiopods were, and are, marine invertebrates Management Specialist. bilateral animals were the earliest life forms or with bivalve shells. Although barely surviving the Inventor: Insect Collecting Allen Aspirator, Fruit Fly organisms on Earth to develop eyes and possess vision “Permian-Extinction,” today, living or extant species of (Medfly) Fruit Collection/Detection Stacking Bucket, for detecting movement. These visionary miracles may brachiopods are rare. Intense-Biased-Survey Medfly Detection Program. ✦

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