Conversations with Cothurnocystis

Fossil of Cothurnocystis elizae. Photo from Ayrshire History.

I first encountered the Cothurnocystis whilst wandering through the Ordovician of the mid-1910s. I had been feeling rather peckish, as it was then Tuesday, so I was collecting brachiopods from the sea floor. I had been assured by an assistant of mine that a collection of these roasted over an open fire made a most filling and nutritious snack, though I must regret the use of the bullwhip that the results of this assertion later required of me. While picking up a large specimen of (as it turned out) more than usual toughness and toxicity, I espied a diminutive object like an elfin boot attached to the shell of my accursed brachiopod by a slender filament from the sole of the boot. I immediately recognised it as a specimen of the Cothurnocystis recently described by Mr Bather, and considered my luck at finding this rare individual. The specimen was much too small to be worthy of consideration for the pot, so instead I lost no time in enquiring after its nature. Together we soon established that the Coturnocystis was intimately familiar with the same works of Bather and Jaekel as I was, as shown by its firm attachment with its delicate stalk, so like the stem of its fellow pelmatozoans. Nevertheless, at that point in time the Cothurnocystis was little willing to speak with me - I do not think I had yet gained its trust, and I suspect my zeal in baking its brachiopod home may have further inclined it against me. I therefore took my leave, promising to return anon.

As luck would have it, commitments elsewhere prevented me from returning to the Ordovician until the 1960s. It was then Thursday, and a satisfying repast of jellyfish and cycads before I left had put me in a far more affable mood than before (though the cycads were to give me a rough time later that evening). I immediately sought out my prior acquaintance, scrupulously checking every brachiopod shell I could find. I was beginning to despair of finding the Cothurnocystis again, when I heard its voice politely enquiring as to what, exactly, I thought I was doing? I sought out the source of this speech and discovered the Cothurnocystis no longer affixed to any brachiopod but lying freely on the muddy floor. Indeed, I could barely recognise my former friend - in place of the stem it bore a long feeding arm with a fine ambulacrum, which it was projecting into the water column in search of tasty micro-organisms. I asked what had brought about this change, and it informed me that it had become inspired by the works of a Mr Ubaghs, who had wholeheartedly convinced it that this was a much better way to live for a stylophoran. I asked how its fellow pelmatozoans had taken this change, and it solemnly informed me that there had been a parting of the ways - most of the other pelmatozoans were crinozoans now, while the Cothurnocytis and its closest associates now regarded themselves as homalozoans. It also invited me to regard the fine hydropores and anal pyramid that Mr Ubaghs had given it, but the mention of the latter reminded me of the cycads, and I had to make for home with great haste.


The mitrate Rhenocystis latipedunculata. Photo from The Virtual Fossil Museum.

When next I travelled to the Ordovician, it was the 1980s. As it was then Friday, all I had been able to find in the cupboard for dinner was some tinned scorpions and a small bag of sequoias, but I had made the most of my frugal meal and was feeling quite refreshed and invigorated. It turned out that I was not the only one so invigorated, for when I found the Cothurnocystis it seemed surprisingly active and to have thrown off the sedentary habits of its past. The feeding arm had been drawn down from the water column, the ambulacrum had vanished, and the Cothyrnocystis was putting it to great use in drawing itself around the sea floor. I apologised for my hasty leave of two decades earlier, and indicated that I was now more able to examine the hydropores and anal pyramid it had mentioned earlier. To my astonishment, however, the creature only regarded me with a look of bafflement. Was I not, it asked me, familiar with the work of Mr Jefferies? It was quite obvious that I was not, for otherwise I would have been aware that it had no such structures. What I had taken for hydropores and anal pyramid was nothing less than its gills and mouth, and it was astonished at how I could confuse such dissimilar structures. Naturally, I protested that it had been the Cothurnocystis itself that had informed me of their natures, at which it relented and admitted that that had been before Mr Jefferies had improved its understanding, and that its ire had arisen from being reminded of past mistakes. At least it had not been so mired in error as its relatives the mitrates, who had been astonished to discover that what they had believed their dorsal surface was, in fact, their ventral, and that they had spent all this time lying on their backs! I enquired after the loss of the ambulacrum, and the Cothurnocystis showed me that it had a mobile tail instead, complete with notochord. I remarked that a notochord and gills were unusual features for an echinoderm to have. Unfortunately, this merely raised the creature's ire once more, and it snootily pointed out that it was no longer a mere echinoderm, but a proud chordate - indeed, a respectable ancestral form whose primal position was far more elevated than my own debased and degraded lineage! Unable to withstand the slurs of the Cothurnocystis' temper any longer, I made my way back home in a state of much vexation.

I have recently returned to the Ordovician once more, on a Sunday after a suitable meal of ecumenical sponges and St. John's wort. Despite the unpleasantness of our last parting, enough time had passed that I once again felt inclined to seek out the Cothurnocystis and see if it had made any further changes. When I did find it, I asked if much had happened in the last twenty years. "Has it ever!" the creature replied. "No sooner had I accepted the word of Mr Jefferies than a Mr Parsley came along to try and change my mind again. He insisted that I did have an anal pyramid after all, and that it was foolish of me to forsake my fine echinoderm brethren for those glitzy chordates. Mr Parsley even turned the mitrates back over. But every time he did so, Mr Jefferies and his associates came back to invert them once more, and now they don't have a clue which way is up! There's a Mr David and Mr Mooi who not only think I should go back to the echinoderms, but think they can get me close to the crinoids once more, even though we hadn't been talking for years!" The Cothurnocystis stretched out its feeding arm and opened its plates to expose its ambulacrum, but then brought it back in and started crawling around with tightly fused plates over its tail. Anal pyramid became mouth, then back to anal pyramid again, at a rate that left me feeling decidedly dizzy. The Cothurnocystis, meanwhile, was continuing its tirade. "There's a Mr Shu who's introduced us stylophorans to a creature by the name of Vetulocystis, and want us to get close to it, but to be honest we don't yet know what to make of it. Mr Hotchkiss could probably handle the idea, but it really doesn't fit with Mr Sumrall's plans for us." At this point I took my leave once more, but the Cothurnocystis left me with one final rejoinder, "I've really come to dread each coming issue of Journal of Paleontology, because I hate to think what they're going to say about us next!"

REFERENCES

Gregory, W. K. 1935. Reduplication in evolution. Quarterly Review of Biology 10 (3): 272-290.

Lefebvre, B. 2003. Functional morphology of stylophoran echinoderms. Palaeontology 46 (3): 511-555.

Ruta, M. 1999. Brief review of the stylophoran debate. Evolution and Development 1 (2): 123-135.