Trilobites: In Life and Death

                       Ubiquitous 300 Million Years Ago: Don't Tell the Creationists

When Charles Darwin was asked by someone with a religious inclination what wonders, of the world, cast light on the working of God's mind, he replied: "An inordinate fondness for ferrets beetles".  Sadly, this is not something Darwin was wont to say- but he should have. Regardless, this answer would have been more appropriate, in my opinion, if it had been applied to the phenomenon that was trilobites.

This post is dedicated and inspired by this innovative, in the evolutionary sense, class of animals, collectively known as trilobites. Sadly, they are now extinct but in their heyday, they were the most dominant and prolific animal in the primordial sea some 500 million years ago. Over the weekend I attended the local 'fair'. Twas an eclectic mix of food outlets, stalls, entertainment and rides for the kids. One stall, in particular, caught my eye. The owner returned my errant ocular appendage and therefore I was able to espy a delectable collection of fossils, various. One, in particular, had caught my eye. Luckily it had landed atop this ancient artefact thus facilitating its recovery. The object in focus was none other than a species of trilobite called, Elrathia kingii. These represent the most common species of fossil trilobite found in shale sediments throughout the world. Hundreds of million years ago this animal was 'swimming' in the shallow seas of the Paleozoic period. And now it was about to be purchased by a slightly mad, but very pert, exiled Englishman.

Trilobites were the first arthropods to evolve upon the Earth and eventually would give rise to crustacea, spiders and insects. They evolved a series of features that were hitherto unique in nature and were incredibly successful, giving rise to over 20,000 species that dominated the oceans for 270 million years. Distribution was ubiquitous throughout the world and it would take four sequential mass extinction events before their demise 250 million years ago in the late Permian. 

Until the evolution of trilobites, the seas were dominated by a plethora of soft-bodied sponge-like creatures. Five hundred million years ago, trilobites burst upon the scene and rapidly filled a whole variety of ecological niches. As previously noted, they were responsible for the evolution of a number of novel features, including the first compound eye, made of calcite, and the presence of a hard chitinous outer shell. The transition and the introduction of a hard exoskeleton were likely to have reflected the evolutionary pressure afforded by predatory sea creatures. Obviously, under such circumstances, the presence of a protective outer shell would have been highly advantageous and likely to be responsible for trilobites' successful radiation throughout the world. The first fossils appear in the Lower Cambrian and are a testament to the ease of fossilisation afforded by a hard outer shell. In fact, the Cambrian epoch was a very fruitful time for the evolution of large numbers of separate species; a period recognised as 'The Cambrian Explosion'. 

Trilobites are known/renowned for their adaptation to a succession of marine environments and could be found swimming freely or crawling on, or within, fertile ocean sediments. Morphology was also varied although they maintained the tripartite structure of their ancestors. Some trilobites were just a few millimetres in extent while others were over 20 centimetres. The varied forms produced exotic looking animals with extended eyestalks, spikes and extra ridges. Also, they evolved the ability to roll up into a 'ball' another adaptive response to the presence of predators. Judging by the presence of trilobite fossils found clustered together it has been surmised that these creatures enjoyed a rich and complex social existence. Their mode of living was as varied as their morphology. And thus, predatory, plankton-eating and sediment grazing species existed together and flourished in warm and cold waters with equal aplomb.  

Even this remarkable, diverse and adaptive creature eventually succumbed to the vicissitudes and vagaries of 'Mother Nature'. However, it took at least four distinct mass extinction events over many million years and epochs before this most resilient of organisms became truly extinct. Surely, this is a lesson for mankind. We may pride ourselves on being the top species inhabiting this fragile planet but Homo sapiens has existed as a distinct species for probably less than 500,000 years. This is a mere blip in the time scale of life's presence upon this Earth. Nature cares nought for our hubris and overweening sense of superiority. Forces that we can scarcely comprehend and control are always queuing to wreak havoc and therefore change the course of evolutionary history, in ways unfathomable to man. It takes but one large asteroid (not haemorrhoid- although their impact on an individual's life can be devastating) to crash upon our fragile Earth, or a perverse extra stellar event or the eruption of a terrestrial hyper-volcano, to set off a disastrous train of events resulting in man's termination of tenure on this planet. An insouciant Earth will give not a jot or a scintilla of pity for our passing. No doubt the Earth will recover, be it in a million or a billion years and the inexorable march of natural selection and evolution will continue in its course, anew. Mayhap, a new 'dominant' species shall emerge. And remember, it doesn't have to be smart, or even sentient, it just needs to be successful in the great game of survival. Imagine far off in the future the Earth 'ruled' by an overbearing squishy mat of gelatinous goo, called Bertram (steady Flaxen). Uncomprehending, but ultimately, triumphant, for a time, at least.