Mantiraptor

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A reptilian brushes through the thicket. Small and lithe, standing on three-toed legs, the little herbivore seems like a mix between a lizard and a naked bird. This eubolosaur mindlessly nibbles on some ferns when, suddenly, two large, slimy arms materialize out of the forest, clamp down and pick it up. The prey’s futile attempts to flee this deadly grasp only dig the huge keratinous spikes and hooks lining the arms deeper into its flesh, as two-clawed paws curl around its belly. Well-placed bites to the back and neck soon end the bleating cries.

The ambusher is Mantiraptor olsoni. Though it also appears like a two-legged lizard, it shares little else in common with its prey. Its skin is smooth and clammy and it has no claws on its feet. Instead of an earhole there sits a large tympanum behind the skull, like a frog’s. This man-sized forest monster, like many others on Ryl Madol, is an anamniote, not quite a reptile, but also not quite an amphibian.

The retention of metamorphosis in these once-archaic tetrapods has allowed for some quite impressive plasticity in the development of the limbs, both through phylogeny and ontogeny. Unlike any reptile or mammal, this predator has been able to modify its forelimbs through the fusion and extension of the metacarpals to such a degree that they now resemble the raptorial arms of a mantid insect. A perfect weapon for lying in wait and surprising the small reptiles of the forest floor.

These arms and the ambush-tactics they facilitate are also all that the mantiraptor has in its favour. Despite its superficially dinosaur-like appearance, it is neither fast nor agile. Its metabolism is slow and it can spend hours, maybe even days, standing or sitting completely still, hidden behind bushes and ferns thanks to camouflage, its breaths so shallow that they do not even create visible movements in the chest. Only when some sensory stimulus occurs do the arms, fueled by a short burst of anaerobic energy, lunge forward and primal instincts kick into gear, mindlessly holding onto whatever has been caught and methodically disassembling it with the crocodilian maw. Once its belly is filled, it seeks shelter and goes to sleep for long periods until hunger strikes again. Its name may evoke associations with the smarter dromaeosaurs of the Cretaceous, but the mantiraptor’s brain is about as complex as a frog’s, if not dumber. While such a robotic being may seem easier to handle, it is exactly this mechanical mind which makes it so dangerous. Whereas smarter predators may hesitate to attack a new animal they do not know, for they may rightfully sense that something unknown may be dangerous, the mantiraptor will disassemble a human just as much as anything else that walks in front of its cold eyes.

Compared to other mantiraptor species, Olson’s mantiraptor is unique for still having a more “classic” style of reproduction. The larvae develop from waterborne eggs and go through an aquatic phase where the raptorial arms develop first in order to feed on small fish and the tadpoles of other anamniotes. Mantiraptors do not go through multiple distinct sub-adult morphs like other anamniotes on Ryl Madol. After the hindlegs evolve and the gills are reabsorbed, the young quickly leave the water and come to resemble miniature adults. More derived species, like Thylacosaurus, have shortened this life cycle even further by carrying around their eggs and larvae in a brood pouch on the back until they can walk by themselves, a method which resembles the marsupial frogs of Australia.

Moschoposeidon

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Though not big enough to stop the flow of rivers, when this beast wades through the murky waters of Ryl Madol, the other animals are sure to feel its presence. With the shoulder-height of an elephant, it is among the largest herbivores of the island.

Moschoposeidon pachyostosteus (pronounced “mos-kho-poseidon”) is a tapinocephalian therapsid that feels at home both on land and in water. In some ways it reminds one of a hippopotamus, with its bulky body and smooth skin. Also like a hippo, its feet and toes are large and broad, allowing for good grip on muddy ground. However, its long neck allows for a far greater range in diet. In water it can easily lean down and pick up various algae and aquatic plants, while on land it can reach for tall tree canopies. Its teeth are simple, mainly made for raking off vegetation and less so for chewing. Instead, the food is masticated with the use of stomach stones (gastroliths). If swallowed in great numbers, these may also help with buoyancy.

The idea that the long neck primarily evolved as a snorkel to breathe when the animal is fully submerged in deep water has proven to be incorrect. Even with the robustly built ribcage, the water-pressure at such depths would be too much for the lungs to be able to greatly expand. It is probably for this reason why these animals prefer to wade only through shallow water, with their bodies being only half-submerged.

Moschoposeidon appear to be surprisingly calm when approached by humans, but that does not mean they cannot act aggressively. Giving live birth, the females can be angered very easily if they feel any source of potential danger coming near their child. During mating season, males can also be observed fighting over access to females with necking-duels, which are simple pushing matches similar to those of elephant seals. The closely related Ceratocephalus exhibit a similar behaviour, but use ossicones growing from their heads to hit each other like giraffes.

The beasts defend themselves by using their great bulk to trample foes to death. If a predator proves to be too formidable or too large to be defeated or intimidated, Moschoposeidon will try to flee into water. Unfortunately, many of the larger carnivores descend from amphibians and so can follow them there.

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.

Armatosaurus

Parareptiles, whatever they may be cladistically (A sister-group to all other reptiles? The ancestors of turtles? A deceptively derived group of diapsids? Not even a real clade?) are abundant on Ryl Madol, though they usually descend from little-known groups that were small and lizard-like during the Paleozoic, such as procolophonids, bolosaurids, millerettids and lanthanosuchids. Except for the hylobolosaurs, most of these descendants do not differ much from their unassuming ancestors. The more famous groups, chiefly the pareiasaurs, which in the Late Permian were the largest herbivores, are rare. This is perhaps not that surprising, as large-bodied and metabolically active creatures (which pareiasaurs possibly were), are more prone to extinction and environmental change. Some scant fossil evidence suggests that, not too long ago, the landmass that would become Ryl Madol used to have its own fauna of giant-sized pareiasaurs, which in many ways convergently resembled ankylosaurs. What has led to the extinction of this megafauna is not known. Possibly, rising humidity, shrinking of the island and growth of vast rainforests reduced the natural habitat that these dryland-reptiles were adapted to and they could no longer compete with the giant diadectosaurs.

The few remaining pareiasaurs are those which have found ways to evade this competition. Some have shrunk in size and evolved unique adaptations, such as the small Neoanthodon of the lowlands, which has evolved a retractable carapace that looks (indeed very suspiciously) like that of a tortoise. But most instead retreated into habitats that are hardly accessible to the ferocious anamniotes, becoming highland-specialists. At about the size of a sheep, Armatosaurus alpinus is the largest of these.

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At first glance, Armatosaurus appears fairly unchanged compared to its ancestors. Especially the horned head bears great resemblance to the extinct genus Elginia of the Scottish sandstones. The spiky dermal armour also appears like a natural evolution of the osteoderms that were already present in the skin of older pareiasaurs such as Scutosaurus and Anthodon. The strongest change is instead found in its limbs. While some ancient pareiasaurs like Bunostegos had already experimented with rectigrade postures, Armatosaurus has taken this development to its inevitable conclusion and has its legs completely tucked underneath its body, walking much like a mammal. With a slenderer build, hooves on its front-paws and tortoise-like hooking-claws on its toes, it is thus perfectly adapted towards traversing the treacherous cliffs of the island, which often threaten to crumble at every step.

Armed with grinding teeth and gastroliths, Armatosaurus is able to feed on the few hardy plants that the barren uplands have to offer. It itself is preyed on by opportunistic mountain predators, such as giant celaenosaurs and gorgopards, but the armour and horns make this difficult. Instead of direct attacks, most hunting strategies consist of luring the prey into a trap, where a simple slip can send someone over a lethal cliff edge.

While not exactly gregarious, armatosaurs can usually tolerate others of their species in their territory, though males, especially during breeding season, can pick fights with each other. These usually consist of pushing matches, where the flat skull-roof and horns are used to force the opponent into submission. These fights can sometimes result in accidents where the defeated opponent is pushed down a slope, often to his death.

Aistoconstrictor

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There are no snakes on Ryl Madol. In their stead slither other, more ancient creatures through the underbrush. Most numerous among these legless vertebrates are aistopods, an ancient lineage of stegocephalians. These were the very first tetrapods to completely lose all of their limbs and in these primeval jungles they have further converged on the serpents that replaced them elsewhere in the world.

Largest among them is Aistoconstrictor latagnathus, which, it has been reported, can grow up to nine or ten metres long, larger than any anaconda. Most individuals are smaller though, usually maxing out at around six or seven metres. Despite technically being an amphibian (in the classic paraphyletic sense), Aistoconstrictor shares many characteristics with actual constricting snakes, such as boas. It kills and captures small prey, such as lystrodos, by biting their head and then ensnaring them with its body, crushing the poor victim under its weight.

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Looking at the skull we can see a combination of both old and new. Overall, the cranium still bears great resemblance to ancient aistopods such as Phlegethontia, with large orbits, large fenestrae and a light construction at the back of the skull that gives the jaw-joints a larger range of movement. Differing from ancient aistopods, the “aistoboids” evolved an extra jaw-joint in their lower jaw, allowing the dentary to articulate with the surangular bone. Like in constricting snakes this allows the predator to “shove” prey down its gullet with its teeth by moving the lower jaw back and forth. Unlike in snakes, the mandibles are still connected at the tips, so they cannot open as widely.

Click to enlarge. Life stages are not drawn to scale.

Being a stegocephalian, likely of the reptiliomorph variety, Aistoconstrictor develops from an aquatic larval stage. It does not raise its young on land in burrows like a giant caecilian, as older textbooks have often wrongly stated. After internal fertilization, the eggs are instead laid into a breeding pond, which the mother often guards until hatching, as some toads are known to do. Upon hatching, the larvae emerge as little eel-like creatures with surprisingly long external gills. At this stage they bear a great resemblance to the larvae of caecilians, though this is surely a coincidence. These aistoboid larvae feed on aquatic insects and algal scum before they grow in size and enter the next life stage, the “spade eel”, named after the shape of its snout. Its gills have shrunk and become covered by a soft skin-flap, while its swim-bladder has expanded into a simple lung, allowing it to breathe both in and out of water. The spade eel lives much like a predatory fish, feeding on many smaller vertebrates by use of ambush attacks. They are also surprisingly gregarious, often swimming in small swarms for protection. Unlike the sub-adult stages of some other Rylian reptiliomorphs, spade eels cannot become reproductively active and are always destined to grow into fully adult “aistoboids” once they lose their gills and live on land.

As a human can in some ways resemble other bipedal animals on Ryl Madol like the lystrodos or eubolosaurs, it may not come as a surprise that stalkers and other explorers are frequently attacked by Aistoconstrictor and relatives, whose coloration conceals it behind the underbrush or lianas. While the creatures are capable of killing people through constriction, human shoulders are usually too wide to fit through the jaws, so the beasts tend to give up after the head and just leave behind a mangled corpse for the scavengers.

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.