It seems safe to surmise that the life of a trilobite was filled with daunting challenges. From their first days in the Lower Cambrian to their last stand during the Permian, some 270 million years later, there were constant, ever-more-advanced threats facing these primitive arthropods. Their initial evolutionary response to such peril was perhaps the most important… growing a hard, calcite shell, which throughout their long history provided a degree of protection from attacks by sharp-jawed Cambrian sea monsters, five-foot long Silurian aquatic scorpions and razor-toothed Devonian fish.
However, it is what happened next to the trilobite body design that proved to be more revolutionary than evolutionary -- the appearance of a complex, and apparently highly effective, system of spines which eventually emanated from virtually every part of some trilobites' anatomy. Exactly when trilobites started to generate defensive spines is a question still open to scientific speculation and debate. It appears that a few early members of the Olenellid and Redlichid lines, such as Esmeraldina rowei, did possess a rudimentary form of this adaptation. But by the Middle Cambrian, such species as Kootenia randolphi and Olenoides superbus featured an imposing series of spines projecting along their axial lobe.
A number of scientists believe that these initial spines may have been somewhat flexible, and perhaps were used by trilobites as swimming rudders as much as for protection. Some have speculated that spines may have served as nerve-filled sensory organs, increasing a trilobite's ability to “feel” disturbances in the water around them. Others postulate, however, that these primitive projections represented nothing more than the start of an undersea “arms race”, which saw creatures around the globe gearing up for daily battles for survival.
In all honesty, it's not as if the paleontological community had long assumed that trilobites possessed rows of sharp defensive spines. The reason for this is simple; during the first few centuries of trilobite research, dating back as far as the early years of the 1800s, such significant yet fragile morphological features were virtually unknown and usually unseen. Indeed, it wasn't until modern preparation techniques began to flourish in the 1980s that these frequently outrageous arrays of quills, barbs and nodes began to be uncovered in all of their spinose glory.
Perhaps it was the worldwide commercialization of both the diverse Devonian trilobite fauna of Morocco and the beautifully preserved Ordovician specimens hailing from Russia that helped launch a serious reconsideration of the role that spines may have played in the lifestyles of these Paleozoic creatures. We imagine that virtually everyone viewing this site has previously encountered some of the freakishly spiked exoskeltons adorning the trilobites that started to emerge from these locales during the last decades of the 20th Century. Such species as Quadrops flexuosa, Comura bultyncki andHoplolichas tricuspidatus dramatically showcase the varied styles and shapes of defensive spines exhibited by certain trilobites.
This proliferation of larger and more imposing spines apparently reached its apex in the Devonian. At that time, such trilobites as Drotops armatus resembled nothing more than a heavily armored battle tank. And judging by the impressive length of time that many of these species survived, it would certainly appear that such a defensive mechanism served its purpose quite well. Indeed, the evolutionary development of spines played a significant role in allowing trilobites to rank among the most successful creatures to ever grace the face of Planet Earth.
Here's a look at some of the spiniest members of the trilobite world:
Esmeraldina rowei from Nevada may have been among the first trilobites in the fossil record to show evidence of spines.
By the Middle Cambrian, trilobites such as Kootenia randolphi had pronounced spines running down its axial lobe.
Olenoides superbus may have been a predatory trilobite, with numerous imposing spines covering its carapace.
The Ordovician trilobite Hoplolichas tricuspidatus showed that trilobite spines became even more numerous with the passing of time.
Closely related to the trilobite above, the Russian trilobite Hoplolichoides furcifer featured horn-like growths on the top of its head.
The Devonian trilobite Comura bultyncki from Morocco ranks among the most spinose trilobites.
Quadrops flexuosa from the Devonian of Morocco resembled a living pin cushion.
Few trilobites were ever as imposing as the six-inch long Drotops armatus from the Devonian of Morocco.