“Ever since we first landed on Eryobis, we noticed that dominant macrofauna on land consisted of two very different kinds of vertebrate. Unlike on Earth, where Tetrapods are the only dominant kind of terrestrial vertebrate, on Eryobis there are two: the sarcopterygian Anisospondyls and the actinopterygian Arachnopods.
Anisospondyls appear to have evolved from an aberrant lineage of Eryobean coelacanths colloquially known as Flattacanths while Arachnopods evolved from a group of Eryobean Holosteans known as octopodichthyian spiderfish.”
“For a long time, it remained a mystery how these two vastly different kinds of terrestrial vertebrates could’ve evolved in each other’s presence, considering they would often have to compete for resources.
Molecular data suggests that both of these clades arose around the same time in what is known as the early Phylloceous period, shortly after a sudden global warming event appears to have caused a major mass extinction, particularly in aquatic fauna.
But how this could’ve happened was still uncertain. That was, until we actually started discovering fossils from the early Phylloceous.
Unlike late Phylloceous fossil sites like the Gerritsen Formation, which show a plethora of both primitive Anisospondyls and basal Arachnopods, fossil sites from the early Phylloceous exhibit either exclusively Anisospondyls or Arachnopods as terrestrial vertebrates depending on the location.
This phenomenon brought forth the theory that Anisospondyls and Arachnopods evolved om different continents that were still separated in the early Phylloceous, but collided somewhere in the middle Phylloceous.”
“Over the years, as more fossils were discovered, the support for this theory grew ever more. The continents were given names for easier reference. The one where the Anisospondyls are thought to have come from was called Knoppira and the one where the Arachnopods originated was called Dallckia. Although has not yet been confirmed where exactly these ancient continents were (as tectonic movements over the eons appear to have completely broken them up and spread them across the modern continents), biodiversity in the fossil sites have confirmed that these continents collided in the late Trextian epoch of the early Phylloceous period. As all fossil sites younger than Trextian deposits feature both Anisospondyls and Arachnopods.”
“The collision of these paleocontinents caused an extinction event due to various flora and fauna suddenly competing with each other. But other than a drop in biodiversity in the early Schippelian, there was little evidence of direct interaction between early Anisospondyls and Arachnopods.
That was, until the discovery of a remarkable fossil found in a think layer of ash dated to the latest Trextian 205 million Eryobian years ago.
A nearly complete skeleton of the largest carnivore of ancient Dallckia, the Osteotariomorph Arachnopod Maxillolonchodon giganteus was discovered with broken bones, many bite marks and several teeth still embedded within its bones. But these teeth did not match the shape of Maxillolonchodon teeth. Instead, they matched other loose fossil teeth discovered in late Trextian deposits from ancient Knoppira. These teeth belonged to a great predator that had strangely left no fossils other than teeth. Until now.”
“Roughly 6 meters away from M. Giganteus laid another animal. It was an Anisospondyl, a big one too. It’s peculiarly shaped visendal spines indicated that it belonged to a group Dextrostelan Anisospondyls known as Aurispinidae.
These basal Anisospondyls had their lateral line organ on the visendal side zigzagging through the spines, thus making their entire sail a kind of ear. As an exquisitely well preserved fossil from the late Schippelian species Aurispinax jubatus shows, Aurispinids had a narrow mane of filaments running along their lateral line organ, presumably for amplifying sounds.
But unlike the other, later Aurispinids, the specimen found alongside M. Giganteus was not a herbivore it’s teeth were knife shaped and serrated, just like the teeth found stuck in the bones of M. Giganteus. This made it not only the oldest Aurispinid discovered so far, but also the only carnivorous species. For this reason it was called Protaurispinax carnifex, the absolute apex predator of late Trextian Knoppira.”
“But these fossils show what happened when the two largest terrestrial predators up until that point met each other. As P. Carnifex also had several teeth matching those of M. Giganteus embedded in its bones, it can be concluded that these two hyper-carnivores fought to the death upon running into each other.
As resources grew scarce after Dallckia and Knoppira collided, the large carnivores were forced to scavenge the coastline for washed up animals where they, unfortunately met each other at the foot of an ancient volcano.
It is presumed they both heavily wounded the other and though the evidence is circumstantial, the state of M. Giganteus suggest that P. Carnifex won the initial battle and later either bled out and died or was buried alive in ash from the nearby volcano.”
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