Carrion Trilobites

Elsewhere in the world, fossil traces of trilobites living in freshwater, let alone venturing onto land, are scarce at best. On Ryl Madol, land trilobites are curiously quite common. In some respects, their evolution here was likely easy, in other ways hard. Like their cheliceratan uncles they were able to evolve simple book-lungs by invagination of their gill-arms into their body. However, what must have been a great challenge is their lack of true mouth-parts, compared to the wide range of mandibles and cheliceres of their cousins. The closest thing they have is a hypostome, which acts more like a backwards-pointed spade or shovel rather than a jaw. This is not a big problem when living on the ocean floor, where microscopic detritus constantly rains from above, but land-life does not grant such luxuries. As the myriapods prove, even feeding off leaf-litter requires mandibles. Facing jawed competition from not only centipedes and arachnids but also the great barage of insects, it is perhaps for this restraint why elsewhere on Earth trilobites were never able to make the big leap onto land, dooming them to an oceanic existence where they would eventually meet their end once marine environments became near-uninhabitable in the Permian. On Ryl Madol the trilobites were able to carve out a few terrestrial niches for themselves, sometimes literally. The reasons for this are unknown but it has been speculated that it may be potentially due to the island’s distinctive lack of derived Neoptera insects, which may have given archaic arthropods more room to expand and adapt.

While some of the rylmadolian trilobites have adapted to feed on soft-bodied worms and nematodes, the majority of terrestrial trilobites are still detritus-feeders, living off the soft excrements and droppings of various larger animals through simple sucking- and shoveling-motions. These basically fill out the same ecological niches as dung beetles and scarabs would. While this may seem like a pitiful existence from a human perspective, it is actually quite a respectable job, as many a great pathogen and toxin meets their end in the robust glabella-stomachs of these critters, keeping the ecosystem healthy and safe from serious disease outbreaks. Still, at least one group has taken up a more savoury diet. The carrion trilobites are a special clean-up-crew that appears anywhere where a large vertebrate carcass lies, usually deep in the thermal chasms. The little critters possess a strongly reinforced hypostome shaped like a wood-carver. They use this to scrape off meat into easily digestible chunks and they are especially good at removing the last bits of flesh from bones. A large swarm of these can turn an ungainly corpse into a beautifully stripped and clean skeleton in under two hours. Rumours of them allegedly doing the same to still-living stalkers are almost assuredly a myth.

Orthrocaris

Ryl Madol is not just a nightmare for its brave explorers but also for the average taxonomists, whether they study the animals live on the island or preserved in formaldehyde from the safety of their comfy university offices. Evolution has taken its very own unique path here, often with entire groups which are elsewhere only known from fossils. The end result are thus forms and combinations which defy all of our anatomical borders.

One of the most enigmatic of these is little Orthrocaris antebabylonensis, or Insanity Fish, curiously often found swimming within the pools and swamps which form at the center of the ancient, ruined plazas and their flooded sewers. There can be no other way than to simply describe it as a chimaera. At the front, a soft, bivalved, gill-bearing carapace, very much like in a phyllocarid crustacean, gives rise to two segmented arms and a head with two compound-eyes. So far, so arthropod. But then the mouth is ringed by four or more unsegmented little tentacles, very much like in a cephalopod. The hidden mouth itself is a single claw-shaped mandible similar to that of a velvet worm. Behind the carapace then emerges an elongated, eel-like body, with a dorsal and ventral fin running down its length. Though this body is soft, on the inside it contains a stabilizing organ which unmistakably resembles the chorda dorsalis of our own phylum. What can be said of such a creature which wildly mixes traits or arthropods, cephalopods and chordates? It is the invertebrate(?) equivalent of a platypus.

That nobody has been quite able to shoehorn this little monster into any taxonomical drawer is not surprising. Some claim the arthropodal characteristics outweigh the others, arguing that this may be some archaic member of that phylum that simply evolved the other traits through convergent evolution. Others argue that a chorda dorsalis classifies Orthrocaris automatically within the Chordata. The truth may literally lie somewhere in-between. Some have noted a resemblance to the Cambrian organism Nectocaris, which used to be similarly reconstructed as a chordate with the head of a bug. However, these reconstructions have long been deemed erroneous, as better-preserved fossils of the organism instead suggest that Nectocaris looked more like a flattened, two-tentacled squid. The resemblance to old reconstructions may thus only be a coincidence. Others have suggested a possible affinity of Orthrocaris to the Vetulicolia, who did greatly resemble an odd mix of arthropod and chordate. The cladistic placement of Vetulicolia is itself highly debated and no known vetulicolian fossil is known to have possessed limbs or tendrils as Orthrocaris has, so this affinity also remains entirely speculative. Said limbs most resemble the scourges of Cambrian legless arthropods like Leanchoilia. If recent genomic studies turn out to be true and Deuterostomia is indeed not a true group, then Orthrocaris may be the descendant of some unknown basal group of the alternative chordate-protostome clade Centroneuralia. In other words, it could, in a sense, literally be the ancestor of all groups discussed. Perhaps it could even be the result of some hybridisation accident, back in some dark Cambrian days when the genomes of all the phyla were still similar enough for such taxonomic bastards to come into existence.

Regardless of its classification, contact with Orthrocaris should be avoided at all costs unless one is properly protected. Although the organism is only as large as an index finger, the bite of some individuals is lethal. Not because it is venomous. For some unknown reason, the saliva of the organism carries a prion inside it. Prions are misfolded proteins, which can cause other proteins to misfold in the same way, allowing them to pathogenically reproduce almost like viruses. There is no known treatment method for prion diseases, so 100% of all infected end up either dead or severely disabled for life.

Like mad-cow-disease, the Orthrocaris-prion is neurodegenerative, meaning it attacks the human brain. It can lead to insanity, followed eventually by brain-death. Some infected have been reported to have escaped their containment and in a mad rave wandered out into the island, only to return days later, with almost no scratch on their body. The animals on the island (who seem to be immune to the prion) show no interest in attacking infected humans. Most shockingly, those patients who escaped without a protective mask on suffered no ill effects from the island’s toxic spores. It seems almost like a sadistic twist that only this disease grants humans the ability to survive on Ryl Madol, but at the price of a short life of insanity. The Headtakers, never too fond of outsiders, have by now discovered the disease’s cause and effect and weaponized it. Using the snake-like glottis in their lower jaw, Headtakers are capable of using blowpipes. When they are feeling especially sadistic, they will carry a leathern waterbag full with little, living Orthrocaris with them, remove the “fish’s” tiny arms and shoot them through the pipes at the necks of unsuspecting humans.

The most bizarre aspect of the prion is just how it cripples the brain. In most cases it mainly affects the areas responsible for language processing, making the infected eventually incapable of talking in coherent words or sentences. Instead, they all start spouting completely unintelligible gibberish. However, all those infected speak the same gibberish and seem to be able to understand each other to some degree, while suddenly incapable of understanding their healthy colleagues. In the early stages of the disease, before they lose the capability of speech completely, they can be heard in their quarantine cells seemingly conversing with each other in undecipherable but still distinctive words and phrases like “Oadriax!”, “Dilzmo!”, “Cordziz”, “Agtoltorn parach asimp!”, “Pappe hasatan, pappe hasatan aleppe” and “Rahel mai ameche zabi almi”. I imagine this must surely be of interest for neurolinguists, but they have not returned my calls.

Marine Centipedes

Myriapods have a long history, stretching all the way back into the Palaeozoic, though they would not become truly successful until the Age of Dinosaurs. That success seems to have been repeated on Ryl Madol, attested to by the island’s diverse fauna of millipedes and centipedes found nowhere else on Earth.

Among these are the marine centipedes, Platychilopodidae, which inhabit the waters surrounding the island. Living their whole lives at sea, their bodies have become streamlined, their legs became flattened flippers and their caudal legs form something that could be called a tail fluke. They even evolved so-called blood lungs inside their tracheae, a trait otherwise only known from aquatic insect larvae.

Chilocaris venefecus is one member of this family. Its preferred prey are other arthropods and small agnathan fish, such as neothelodonts, which it captures with its large jaws and injects with venom. It itself is preyed on by large fish and marine reptiles and amphibians. As many would-be explorers have painfully found out, if the “marinopede” cannot defend itself with its venom, it will use its “tail-fluke” as a pincer.

Among the Platychilopodidae, C. venefecus is one of the smaller species, growing about 20 centimetres long. It is far outdone by the horrifically large Con Rit, Cetioscolopendra aeliani.