Pointilisaurus

Ever since naturalists have first set foot on the island, they have made note of a variety of small, bipedal herbivorous reptiles running around. This being the early twentieth century with its limited understanding of paleontology, the reptiles in question were early on classified as genuine surviving relic dinosaurs, specifically of the small ornithischian types such as fabrosaurs or hypsilophodonts. But as their skeletons were more closely examined, and our understanding of fossil reptiles grew, it was recognized that the small runners on Ryl Madol were something else entire.

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One of the first clues was the structure of their feet. Ornithischian dinosaurs only had four toes, whereas the Rylian lizards have five. Moreover, ornithischians walked on digits II – IV, with the inner toe digit I being reduced to a dewclaw. The island reptiles, however, walk on digits III – V, with digits I and II being reduced. The same pattern is also seen in their hands. While the elongation of the outer digits is common in some reptiles, it would be highly aberrant in dinosaurs.  The skull of these animals finally negates any association with the Dinosauria, for it lacks the antorbital fenestra typical of archosaurs and the back of the skull is even in a partial anapsid condition.

The final clue came, surprisingly, from Germany, when in the Permian aged Tambach Formation was found the fossil of Eudibamus cursoris. This was a little bolosaurid, a type of parareptile related to the larger pareiasaurs. Its hindlegs were highly elongated compared to the arms, leading to many reconstructing it as possibly the earliest biped. The condition of the skull, as well as the arrangement of the toes, is mostly identical to the bipedal mystery reptiles on Ryl Madol. Today, there is consensus that these creatures are descendants of this often-overlooked little parareptile, having adapted to obligate bipedalism and a fast-running lifestyle convergently to dinosaurs. The names that have been given to this new group in the technical literature are both Eubolosauria and Hylobolosauria and there is dispute over which name has preference.

One of the most common and well-known of the eubolosaurs is Pointilisaurus sibbicki. It is a small, fleet-footed herbivore, about the size of a green iguana. Gregarious, it can often be seen in small herds browsing on the lowland meadows or the forest edges. The groups are loosely organized and they quickly scatter when a predator like Gorgoraptor strikes. Social interactions are minimal, though some researchers have noted that the reptiles vocalize when in groups through a strange, cat-like purring sound. How exactly they produce this sound remains debatable. Reproduction is quite simple. After mating, the female lays her eggs in a hidden nest in the ground and leaves the eggs to their fates. The hatchlings usually survive through strength in numbers alone, with many of the little lizards falling prey to the voracious jungle shortly after emerging out of the ground.

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While the most common eubolosaur on the island, it is also the most primitive, still sharing many traits with Permian Eudibamus, such as the iguana-like mouth with leaf-shaped teeth. Through anatomical and molecular studies, it has been revealed that many of the more enigmatic reptiles on the island can also be placed in the same group, however within a separate clade. These derived eubolosaurs have, in an even stronger parallel to some dinosaurs, evolved a predentary bone at the tip of their snout, giving them a sharp beak well-suited for chipping vegetation. These are the Aviopsia, which as of writing consist of three families. Saltopusauridae are small herbivores with parrot-like faces that move by saltation, similar to kangaroos or wallabies. The families Anatopsidae and Cheloniopsidae together form an even more derived clade, signified by the loss of the two inner digits of the foot, which for a long time obscured their relationship to the other eubolosaurs. Anatopsidae are huge, amphibious reptiles, with duck- or geese-like bills they use to feed on a wide variety of aquatic plants. Cheloniopsidae, such as the massive Acanthoracosaurus, are more terrestrial animals, which shield themselves against the island’s predators with strong, stegomorph armour and spikes.

While non-avian dinosaurs, as to our knowledge, still remain absent from Ryl Madol, these magnificent beasts are no less exotic nor less worthy of our awe.