Troll_Man
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WWD: Pliosaurid indet.
🕑 Added 2023-07-15 09:01:09 +0000 UTCThis might be the most controversial change, but it's a major issue with anachronism. The original episode was set 106 MYA, but of the animals depicted, only the Muttaburrasaurus was actually known from that time, every other animal is only recorded from the Barremian to the Early Albian. Koolasuchus and "Allosaurus robustus" are the upper extreme here, being only known from the Wonthaggi Formation, which dates to the Late Barremian (120 MYA) at latest, making them roughly twenty million years too early. Even moving the date up to 110 MYA makes Koolasuchus about 10 million years too late. It was a bit of a missed opportunity that the Chinle Formation had no temnospondyls since it could've set up this plot thread to begin with and a temnospondyl species is in fact the most common tetrapod of the fossil site.
The episode uses the interpretation that giant temnospondyls only survived in southern Australia because its cooler climate prohibited colonization from aquatic crocodilians, which had driven them extinct elsewhere. It can't be said for sure if this is true, but following this hypothesis, Koolasuchus could not exist by then, because crocodilians are known from the Eumeralla Formation by 110 MYA, possibly due to a marginally warmer climate. Following the interpretation of Koolasuchus extinction by competition, or an alternate idea it was only adapted for a very cold climate, it unfortunately could not be present by that point.
So here we introduce its replacement, a freshwater pliosaur! Having it be a crocodilian would be pretty boring, so I opted for a more interesting freshwater carnivore (although this does make three episodes in a row with pliosaurs). As you might expect from this episode, it's another garbage taxon; in this case, it's known only from one partial tooth. Comparison of this tooth with another pliosaur species suggests that it was, at minimum, around four metres in length. This is pretty puny compared to the gigantic marine forms that would have existed at the time, but pretty huge considering it was a freshwater species. Technically speaking, this tooth is known from earlier strata of the Eumeralla Formation than the episode's revised setting (Early-Mid Aptian rather than Early Albian), but their presence later is much more likely than Koolasuchus, considering the continued survival and success of plesiosaurs much later into the Cretaceous is inarguable. That said, it's also been argued the tooth may belong to a spinosaur, although the supposedly Australian spinosaur vertebrae from the that was used to help support this possibility has been reinterpreted as a megaraptoran, while the presence of freshwater plesiosaurs in the area is known from multiple fossils and pliosaurs are unambiguously known from the bordering Eromanga Sea.
Interesting, there were at least two different species of plesiosaur present in the region, indicative of the area's massive and highly productive tributary system. During this period in Australia's history, the region of the Eumeralla Formation was located within a vast, heavily-forested, rift valley that connected it to Antarctica, and huge rivers ran through it, some at least one-hundred feet deep and stretching for many kilometres. It is tantalizing to speculate that plesiosaurs may have had an advantage owing to their warm-blooded metabolism, but it does raise the question how an obligate aquatic animal survived months of darkness. Perhaps they migrated to the coast during the winter? Or perhaps these were juveniles that sheltered in freshwater from larger marine predators and the polar winter sea?
