Ororhynchus and Lapidoscelis

The hills and ranges of Ryl Madol are often pockmarked with holes and burrows, created by the various fossorial reptiles and amphibians. Many of them are inhbaited by Ororhnychus marmotaoides, which in some ways is an oddity on this island, despite its very conservative anatomy. Like Iniasaurus and Nothocadborus, Ororhnychus and its relatives are creatures that are decidedly Triassic in character, as opposed to most of the other fauna on the island, which traces its origins back to the Paleozoic. It is a rhynchosaur, a group of bizarre archosauromorph reptiles, which once used to thrive in the arid wastes of Pangaea before their dinosaur-cousins began to ecologically dominate Earth. However, most phylogenetic studies indicate that rhynchosaurs have an early origin somewhen during the Latest Permian, so their presence here is not as anomalous as, say, Cynocetus.

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Rhynchosaurs as a whole are abundant on Ryl Madol, though usually in a form no longer reminiscent of the Triassic taxa, such as the arboreal Sciururhnychia and the flying Celaenosauria. These are usually grouped together into the Neorhynchosauria (though some workers consider this clade to be polyphyletic). Even among these rylian rhynchosaurs, Ororhnychus stands out due to how archaic it appears, being the only extant species that does not seem to be part of Neorhynchosauria. Instead, it phylogenetically groups closely with classic Triassic forms like Hyperodapedon and Fodonyx. It still walks on all fours, in a semi-erect stance, and has strong digging feet. Its head is a powerful piece of primeval engineering, with huge jaw-closing muscles and rows of interlocking teeth, as well as tooth plates on the floor and roof of the jaw, which all slide into each other like a pen-knife. In essence an extreme version of the jaws of a tuatara. The upper jaw terminates into a sharp, downward-pointing beak, which fits into a bifurcated beak on the tip of the lower jaw. With this arrangement it efficiently clips, chews and grinds the abundant seed ferns which green the edges of the island, such as Kainodicroidium. A living fossil on an island of living fossils.

Ororhynchus live largely solitary lives, browsing for leaves or digging for tubers for most of the day and sleeping during the night in large burrows they dug out themselves with their strong claws and beaks. If an Ororhnychus dies or abandons their burrow, it usually becomes a shelter or home for various other animals that cannot dig themselves, making these rhynchosaurs important cornerstones of the upland ecosystems, mirroring in some ways the Castorosaurus of the lowlands.

Only during mating season do two Ororhnychus form a mating pair in order to care for and protect their eggs. But after the hatchlings are grown up enough to leave the burrow and live on their own, the pairs break up again to live on their own. That said, long-term observation has revealed that former pairs are more likely to hook up again in subsequent seasons than complete strangers. This is intriguing and suggests that these animals, despite their primitive demeanour, do have some degree of personal long-term memory and can maybe even have favourite partners. This is further supported by the fact that Ororhynchus have been observed leaving their dung in very specific spots where others have defecated too, so-called communal latrines, which are usually located in a central area between multiple burrows. In many other animals which exhibit this behaviour, communal latrines are used as a sort of message board, the pheromones and other smells in the dung allowing the animals to communicate through time, informing each other about their presence, territory, health and mood. Despite being outwardly loners, these animals still seem to value keeping in touch with each other and so have amusingly been described as “long-distance social”.

Unlike the aptly named Armatosaurus it shares its habitat with, Ororhnychus lacks dermal armour and may therefore appear as an easy prey for predators. Though again, appearances may be deceiving, as the reptile has strong natural weapons instead of defenses. Its jaw, adapted for crushing and grinding hard plant matter, could easily break a human’s arms if given the chance. The tusk-like beak itself is also sharp like that of a huge snapping turtle and can also be used as a stabbing weapon. The approaching Lapidoscelis triceros, who seems to have wandered off from its usual lowland habitat, is about to find this out the hard way, if it does not back off.

This is another ancient relic, this time from the primordial coal swamps of the Carboniferous. Its differentiated teeth, especially the long incisors and dog-like skull shape are vaguely reminiscent of the synapsid predators which roam this island, but it is actually something even more primeval. What gives it away is the slit-ear, high on the skull placed inside an otic notch, a trait not found in amniotes. Like many other creatures on the island, it is an “anthracosaur” or anamniote, an “amphibian” close to the origin of reptiles and synapsids without yet being one itself. In many ways Lapidoscelis is remarkably similar to the ancient fossil Limnoscelis, to whom it is most likely closely related. The main differences are ornamental, such as the three bone crests atop the skull, giving it its species name, as well as the basilisk-like sail on its tail. Both of these are likely used for social display, especially the red-coloured nose-crest.

Despite being mainly a quadruped, the animal is intriguingly capable of rearing onto its hindlegs and even clumsily walking that way over short distances. Facultative bipedalism is a trait that is strangely shared by many anamniotes across the island, apparently having evolved separately on multiple occasions. The same convergent tendency towards increased bipedalism is also seen in many of the reptiles and synapsids, creating a whole array of creatures that look like pseudo-dinosaurs.

What evolutionary pressures drove all of these creatures to evolve varying degrees of bipedalism remains a mystery. One tentative hypothesis is that the original driver may have been the extensive wetlands of the island, forcing many animals to evolve strong tails and longer hindlegs than forelegs for paddling and swimming first. This then served as a pre-adaptation for bipedal wading through shallow, cluttered water (something indeed observed in incipient bipeds like Lapidoscelis), which in turn served as a pre-adaptation for bipedal walking on dry land. Outside of Ryl Madol, the same hypothesis has also been used to explain the convergent evolution of bipedalism in many Triassic archosaurs, including the dinosaurs. While this idea makes a lot of sense in the amphibious anamniotes, the hypothesis cannot explain each case. The lycaenoraptors for example seem to have never had an aquatic phase in their evolution, while the bolosaurs were already bipedal all the way back in the Paleozoic, presumably before arriving on Ryl Madol.