Mesotylos

I remember still one of the very first expeditions I undertook on Ryl Madol. I was still a young researcher, given rather mundane tasks. There was an area close to the coast that was designated as relatively “safe”, where I routinely documented the local population and diversity of carnivorous cycads (yes, the plant, not the insect). Technically it was a task I could have done by myself, I knew my way with a gun in case any dangerous animal might have appeared, but, of course, the research base did not fully trust me, so they signed up one of the hired mercenaries to escort me each time I went. It was pretty simple. We donned our gasmasks, took a small motorboat out from the base islet and drove it upriver to the research area. Most days were quite peaceful. Most of the big, scary things live further inland and most of the aquatic life gets scared by the sound of the boat. The guy, Johnson, was sadly not that talkative. He seemed rather annoyed to be my “babysitter”. He often just sat there on the boat, gun in hand, and quietly watched me as I walked around on shore and studied the plants. The plants, you ask? Oh, they’re only dangerous if you are a bug. Ryl Madol may be full of biological wonders but even it doesn’t have man-eating plants straight out of Hollywood. At least as far as we have observed.

So, there I was one day, counting cycads (or were they benettitaleans?), when, absentmindedly, I moved a little outside the research area and, out of the view of Johnson, deeper into the forest. I just roamed around a little when, suddenly, three men walked out of the underbrush and circled me. Their faces, like mine, were obscured by gasmasks to protect against the toxic spores. They looked rugged and they carried high-calibre weapons. One of them, visibly unwell, had an insanity fish still stuck to his neck. I’m not even sure he noticed the death sentence, perhaps he was this numb from all the pain he had already endured. They clearly were not my guys. They were stalkers, come here to raid the island for artefacts. Sometimes they kidnap or take hostage unsuspecting scientists, thinking that we have more secret knowledge on where to find the good stuff. Today it seems it was my turn. I tried to cry out for Johnson, but one of them put a gun to my head before I could even raise my voice. I knew I’d be dead if I screamed. They asked me if I knew where the “Dream Pool” was. I did not know what that meant and to this day I still do not. But of course they thought I was lying and began to beat me up. My mask nearly broke. In that moment, out of the corner of my eye, I saw something moving between the trees. It was some sort of translucent shadow, either camouflaged perfectly or nearly invisible. But I could sense some kind of movement between the tall cycad trees. Out of raw nature itself, it seemed, two hooked arms materialized and pierced through one of the stalkers, lifting him into the air like a praying mantis would a fly. My first thought was some kind of mantiraptor, but we have never seen those being able to change their colour. Though maybe that is exactly the point. The poor guy, claws pierced straight through his shoulder and belly, screamed like hell. He tried to lift his gun and shoot wildly around. I don’t know what his plan was, he was probably not thinking at all in the moment. By a mere miracle he missed me and instead it was now one of his stalker buddies that ended up screaming and bleeding out on the forest floor. The third guy lifted his gun and tried to shoot at the invisible arms puppeteering his friend, but before he could even pull the trigger, something else grabbed him and dragged him silently into the jungle.

The next moments are blurry to me. For unknown reasons I was spared by the ambush and was able to run back to the river. Johnson was sitting there, waiting for me. It was as if nothing had happened. He sat there, upright, with his wannabe military-uniform, oar of the boat’s motor in one hand, the other hand on the pistol holster, ready to pull on any unsuspecting foe. But there was just one problem. His head was gone. Ripped clean off, no trace of it in sight. I don’t think I even saw any blood splatter on his clothes, at least not in the heat of the moment. I did not really have the time to think about how morbidly bizarre that was, I just pushed the boat back in the water, pushed his body out of the way and started the motor. Downriver I think I took a few wrong turns and suddenly ended up in some quite bad, rocky rapids. I crashed the boat and flew overboard. All I can remember next was floating out at sea, not too far from the coast. The current must have swept my unconscious body out. I took my mask off to get enough air.

As I was contemplating my options, perhaps trying to swim back on shore, that wass when I saw it approach me. The huge shadow of a Mesotylos, a nearly 10 metres long carnivorous marine reptile, slowly drawing near me from beneath the waves. I could see it undulate up and down through the water, swinging its large, wing-like fins up and down, like a humpback whale. The long, crocodile-like maw turned towards me and I just knew I was done for. There was no way for me to survive this encounter. I just leaned back in the water and pretended to be a corpse, in the faint hope that it might lose interest. 

The strangest thing then happened. I could feel it poke me with its snout, me doing my best to remain stiff and not panic. I could feel it nudging my body. But it did not attack. It placed its head underneath me and then gently lifted me above the waves. I could feel it breathing through its retracted nose and I sure as hell know that it felt me breathing too. But that is all it did. Lifting my body out of the water and just gently float there with me, for what felt like an eternity.

Eventually I heard a boat approach and, thankfully, it was one of our own research vessels. As the sound drew closer, the reptile sank into the depths again and left me alone. The crew had seen me and were able to pick me up right after. To this day I still think about what happened. Why am I not dead, a pile of half-digested bones at the bottom of the ocean? Was the animal just not hungry? Did it not recognize me as food? Was it just curious? I cannot help but be reminded of those old stories of sailors being saved from drowning by dolphins.

As the name implies, Mesotylos is a mesosaur, as far as could be gathered from stranded specimens. Yes, a mesosaur. Not a mosasaur. Mosasaurs were true marine lizards of the Cretaceous, whereas mesosaurs were much more archaic beings of the Permian period, the very first marine reptiles (though in some phylogenies they even end up on the synapsid side of the amniote family tree). In a world as stuck in the Palaeozoic as Ryl Madol, it is perhaps no wonder that such animals survived here and continued to evolve. Very obviously, Mesotylos and kin have managed to make the full shift into fully marine life, as have many amniotes that came after them. Unable to move anymore on land, they have completely reduced their hindlegs and their forelimbs have become elongate flippers perfect for “underwater-flying” as is also seen in penguins and the extinct plesiosaurs. Uniquely for any amniote, this style of underwater-flying is combined with a vertically undulating, horizontally flattened tailfluke, very much like that of a manatee. Also very strange is that each flipper still retains two prominent claws, something not seen in any other fully marine reptile or mammal. Perhaps these do serve a function in mating, or maybe they have some hydrodynamic effect. Speaking of mating, their reproduction remains unknown, though it is generally assumed that they give live birth, unlike their egg-laying ancestors. Based on the shape of the very crocodile-like snouts, it is also generally assumed that they feed on fish and various other aquatic vertebrates, which makes my survival all the more miraculous.

Apart from this, nothing more can be said about these mysterious animals, as they are rarely encountered in life. Cryptozoologists like Bernard Heuvelmans have suggested that Mesotylos may be the origin behind various sea serpent sightings all around the Indian Ocean and Southeast Asia. While that idea may at first seem compelling, there is so far no solid evidence that the unique fauna around Ryl Madol’s coast has ever ventured to other areas of the globe, unless by human means. It is as if some strange force binds the animals to the island.

Regarding the little “reef friends” I depicted the fellow with: On the very right we can see one of the many strange brachiopods that inhabit the island’s waters. Its long stalk makes it resemble early Cambrian stem-forms, like Yuganotheca, however this appears to be a case of convergent evolution, as it is found to be a true rhynchonellid.

Emerging below it from a small tunnel is a Dermichthys, nicknamed “Dunkeelosteus”, a small antiarch placoderm with an elongated body that lives much like a moray eel, hiding in reef burrows and ambushing prey. Swimming below it is one of the many marine centipedes that swarm the island’s waters, as well as an ophiuroid brittle star.

More interesting is the Arboreaites and her offspring on the lower left. All research indicates that this seems to be a bona fide arboreomorph, a type of Petalonamae from the Ediacaran or Late Precambrian. This makes this unassuming frond actually one of the most interesting organisms in this picture, as it is the most ancient organism on show here. Tests done on these organisms have validated many hypotheses that had already been suspected about the fossil relatives: 1) They are indeed true, diploblastic animals, however outside crown-Eumetazoa. In other words, more derived than a sponge, but still more archaic than a jellyfish (though some genetic tests intriguingly recover it as somewhere near the base of Ctenophora). 2) It is in fact a colonial organism composed of multiple zooids, which together constitute a holdfast, a backing sheet and the many lobed filter-feeding “pods”. The central stem itself that is keeping everything together it in fact a bundle or fascicle of stolons protruding from all the pods. Very intriguingly, the individual zooids of Arboreaites, stuck on the inside of each pod, resemble miniature versions of the solitary rangeomorph Charnia. As can be seen Arboreaites can reproduce asexually using stolons along the ground, very similarly to bryozoans anc cnidarians. However, sexual spawnings have also been observed, where the organisms release eggs and sperms into the water. Even though the organisms lack true gonads, they appear to be able to produce these gametes from undifferentiated body cells, much in the manner of sea sponges.

It is extremely intriguing that Arboreaites survives and even thrives around the reef regions of Ryl Madol, despite plenty of competition with supposedly “better” Palaeozoic life. This brings into question many leading hypotheses about the extinction of these organisms elsewhere in the world during the Cambrian. One wonders what Earth’s oceans might look like if more of these had survived. Now that would be a fun scenario to think about for the enthusiasts of this new-fangled gene I heard of. I think they call it “speculative evolution.”

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.

Walky Tully

Ryl Madol is already home to a variety of animals which by all rights should not exist, at least not anymore, but even among them the walky tully (Micrormus holidayi) stands out, as it has evaded proper classification to this day.

What really can be said about an animal whose jaw sits at the end of an extendable proboscis, has eyes on stalks like a snail, a body like a tadpole and three clumsy legs? It has a backbone, so at the very least it can be considered some kind of vertebrate, but that is where consensus ends. Unlike any other vertebrate, there is no direct bone-connection between the jaws and the cranium, the “neck” is just a floppy tube made of cartilage and muscle, attached to what resembles the hyomandibular bone of sharks. Despite living in water, it has lungs but no gills. Its “fingers” have no resemblance to those of tetrapods, instead having evolved from fin-rays, the internal anatomy of the forelimbs somewhat resembling the alternating bone-structure of lungfish-fins. The single hindlimb is located behind the cloaca, meaning that it is possibly homologous with the anal fin found in most fish. However, in the vertebrae, the pleurocentrum dominates, which is a trait more typical of stegocephalian tetrapods than of fish.

With its proboscis and stalked eyes, many researchers have obviously tried linking this animal to the notorious fossil Tullimonstrum gregarium of Illinois, which is where its common name comes from. However, the classification of Tullimonstrum is itself controversial, as it is not even clear if this organism was a vertebrate or an invertebrate of some kind. If Tullimonstrum was a vertebrate, it would have been one of the most basal cyclostome kinds, a relative of lampreys and hagfish. It notably has no fins whatsoever, at least none that were ever able to be identified from the fossils. If Micrormus is indeed a descendant or close relative of the tully monster, then it must have evolved limbs, lungs, a loss of gills and various other characteristics that are not present in its Carboniferous ancestor independently of other vertebrates.

This suggests that the resemblance is merely due to convergent evolution and that Micrormus is some kind of highly aberrant bony fish, possibly sarcopterygian in origin. Due to its amphibious characteristics, the most radical proposal has been that it may descend from some type of tetrapodomorph that, like the coelacanth, still possessed a muscular anal fin but for whatever reason had lost its pelvic fins, which in true tetrapods evolved into our hindlegs. This hypothesis is not at all popular, but other suggestions have not been less crazy, such as the idea that Micrormus is a vertebrate-mimicking cephalopod or a relative of the dancing worms of Turkana. Genetic studies that could shed more light on the matter are unfortunately lacking.

In contrast, the actual life habits of the walky tully are surprisingly unspectacular. It is a small animal, able to fit comfortably inside a human hand. Like most fish on the island it has developed an amphibious lifestyle and spends a lot of time crawling around or even sleeping on lake shores. When “walking”, the single hindlimb is not used merely as support for the forelimbs but also helps the animal push forward, earning it the alternative name “mud-tripod”. In the water it hunts smaller fish and tadpoles, such as the mantiraptor larva seen here. Some researchers have proposed that it actually is a specialized tadpole-predator, but there is no conclusive data that it prefers this prey over any other small aquatic critters. Among its own enemies are various stegocephalians, predatory fish and the stork-like gruisaurs.

Tullys reproduce through external fertilization and lay their spawn inside protected alcoves along riverbanks. The young hatch as miniature adults without first going through a larval stage, which is why gleaning its evolutionary history from embryological data has also proven difficult.

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.

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.