A bit more on the churn of stuff in the Triassic. It was just a few years ago that Sterling Nesbitt shocked the paleontological world by publishing the biggest and best cladogram of Triassic Archosauriformes, or whatever exactly his cut-off was, that recovered phytosaurs as outside of Archosauria and as a near sister-group of it. More recently that particular question has been reevaluated, and phytosaurs are now recovered by newer cladograms as the most basal group within Archosauria. This all has a bit of the feel of inside baseball after a while. Ultimately, if you’re looking back at your family tree and you find that you had some guy who was your ancestor a thousand years ago, do you care if some other guy was his uncle or his brother? No doubt it mattered to him, but in the grander scheme of things, it makes no difference at all. And it’s not like phytosaurs and erythrosuchids or whatever were writing each other to get their family trees. This is similar in many ways to what I posted about yesterday; at the end of the day, does it really matter very much if silesaurs are the closest sister group of Dinosauria or if they’re basal Ornithischians within Dinosauria? That’s the exact same situation. Ultimately, it only matters for determining minute details of cladograms, evolutionary family trees. I’m somewhat casual about that because I like classic phylogeny for many things, and because I’m aware of the mathematical and statistical challenges to the theory of evolution as it’s currently stated, which many biologists do not understand, because they’re not mathematically or statistically astute enough, or not aware of the study of genetic fixation and other genetic research that would falsify the theory. However, as Professor Frank Tipler of Tulane University states, specifically about this situation, “If you cannot understand the mathematics, assume the mathematicians do.” This is why I don’t think that phylogeny is necessarily as important as the specialists make it out to be; if the entire basis for evolutionary cladistics is based on an evolutionary model that fails mathematically, then how interesting the results of the model are will drop accordingly. And it doesn’t change anything material about the animal; regardless of where you place Phytosaurs or Silesaurs on the cladogram, and regardless of whether you call them Archosaurs or Dinosaurs, the animals are still the exact same either way, and their role in their ecosystem is still exactly the same either way, and their interactions with the rest of their faunal assemblages are still the same either way.
To me, that’s probably more interesting than what are relatively speaking kind of subtle shifts on the cladogram. It’s also why I prefer to use useful yet “outdated” classic phylogenetic labels. Silesaurs, for example, is a very useful label, and everyone knows what a silesaur is (well, if you’re familiar with Triassic paleontology. Maybe a label like prosauropod would be a better example.) If Silesaurs are not basal ornithischians, then they will no longer be monophyletic, but paraphyletic, and the label will become unusable by the pedantic nitpickers who run around saying “basal sauropodomorphs” instead of prosauropods.
Regardless, the reason that the Triassic is so interesting is that there were essentially three great biological “empires” competing for who would run the show. The therapsids were the outgoing empire that took a huge hit during the Permian-Triassic extinction event, but they were still putting forward strong contenders for large and small herbivores, at least, until the very end of the Triassic. Their predator lines were kaput, but they were also innovating and becoming the mammals in the meantime… again, although from any perspective other than the (somewhat) arbitrary distinction between the later mammaliformes and actual true mammals is kind of superfluous. The Triassic is the story of their long slow defeat, although as noted, dicynodonts were still going strong up until the very end, and their takeover of the small, often nocturnal roles was impressive enough during the next two phases of the Mesozoic and set them up nicely to come into play after the much later K-T extinction event. It’s also the story of the dinosaurs growing in size, prominence in the faunal assemblages, and expanse across the terrestrial ecosystems, positioning themselves to become heavily dominant after the Tr-J extinction event that ended the Triassic. But what is often forgotten is that while the therapsid lines were turning into mammals, their “empire” was failing and ended conclusively at the Tr-J line, and while the dinosaurs were also growing out of their proto-dinosaur lineages into dominance, the real, actually successful empire during the Triassic was the Pseudosuchian Empire, a third player that had barely started during the earliest Triassic, but who quickly claimed the position of Imperial success story throughout the entire period. They ended up passing through the Tr-J line as a variety of successful forms, but their diversity and their position as the Imperial apex megafauna of the assemblages were over, and their entire reign as the imperial juggernauts of the Triassic era was unrecognized for a long time; and even now only a few specialists and weird fans like Chinleana, CHimerasaurus, and to some degree even me, even recognize the existence of the Pseudosuchian Empire.
Or, based on my stated preference for some of the old Linnean labels, maybe I should call it the Thecodont Empire?
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