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.

Carnoconodon

“Whoever digs a pit may fall into it, whoever breaks through a wall may be bitten by a snake.”

- Ecclestiastes 10:8

The deepest parts of the tectonic chasms will of course accumulate water in them. Nourished by the decay of leaf litter, rotting carcasses, gnawed bones and scavenger excrements, these ponds have turned into the most fetid of swamps. In the murky waters swim horrific creatures, often the descendants of marooned gut parasites and the most lowly and dreadful of scavengers.

Among the latter, species of Carnoconodon tend to be the most pugnacious. As the name suggests, these are living members of the conodonts, a group of jawless fish, vaguely reminiscent of the lamprey, with a bizarrely intricate tooth-apparatus. Having populated the seas from the Cambrian until the end of the Triassic they have proven themselves to be tenacious, but Ryl Madol is now the only place on Earth where they survive.

Carnoconodon has in some ways evolved a simpler mouth than its ancestors, it just being a yawning gape that opens up like a zipper. It is adorned by multiple rasping teeth on the inside with eight-to-ten large slicing teeth ringing its edge. Where it surpasses its ancestors is of course its size, growing up to a metre or two in length.

Carnoconodon is often characterised as a scavenger, scraping flesh off the carcasses of animals that have fallen down the deep chasms and died from the impact. This is not entirely accurate. If a poor victim survives its fall, these eels from hell have no qualms about finishing the job themselves, often attacking in swarms and slicing deep wounds into the flesh until it bleeds to death. Our dinocephalian here is finding this out the hard way.