Paludirex: Life of the Swamp King
Having gotten the long taxonomic history of Pallimnarchus and Paludirex out of the way (see here), lets talk more about the animal itself.
As far as we know at this point in time, Paludirex was the last of the large semi-aquatic mekosuchines and the largest members of this group had ever gotten. Whereas the cleaver-headed Baru dominated the waterways of the Oligocene and Miocene, Paludirex lived from the Pliocene and Pleistocene. There is some division between the species tho as it appears. Given the ambiguity around the origin of some Paludirex vincenti specimens, this species is currently only known from the Pliocene, whereas Paludirex gracilis is currently only known from the Pleistocene. There may also be a third species from the same region as Paludirex vincenti.
Comparisson between Paludirex gracilis (left) and Paludirex vincenti (right)
Anatomically, Paludirex has a pretty easily recognizable animal. Unlike Baru, with its short, triangular skull, Paludirex had a head that was almost rectangular when viewed from above, about half as wide as long and comparably flat. Mind you the skull can still be pretty deep, especially in Paludirex vincenti, but the proportions still highlight how wide it is most of all. In both robustness and skull width, Paludirex far exceeds what is known in modern saltwater crocodiles, which likely fill a similar niche.
Left: Skull reconstruction of Paludirex vincenti.
Right: Life reconstruction of Paludirex (Nellie Pease)
As said before, Paludirex represents the biggest mekosuchine. At a minimum length of 4 meters, it already rivals many of today's crocodiles and Baru, and that's just the smaller ones. Large individuals of Paludirex vincenti probably got much larger, 5 meters and more further drawing parallels to todays salties.
A size comparisson between Steve Irwin and both species of Paludirex
Now while the description is pretty sound on account of recent work by Ristevski and co., the ecology is a different matter. A lot of work was published back when Pallimnarchus was still a thing, so trying to separate what and what isn't applicable these days is a bit of a challenge.
On the most simple level, Paludirex was a generalist semi-aquatic ambush hunter. It's skull, tho incredibly robust and wide, shows no peculiar adaptations like long slender jaws so its obviously not a specialist. It's semi-aquatic because the nostrils and eyes face up so that they would peer out from the water while the rest of the body remained submerged. And these last two together basically suggest ambush-hunting.
Willis and Molnar also made comparissons between Paludirex skulls (or rather skulls now recognized as such) and Mugger crocodiles. All in all this suggests that its diet could have ranged from turtles to aquatic birds to large mammals (so the typical croc range really). They also infer that it may have had similar habitat preferences, being found in marshes, swamps, rivers, lakes, anywhere theres freshwater really. One exception may be that some researchers have argued that Paludirex was avoiding saltwater and brackish water, which eventually could have factored into its extinction once inland waterways in Queensland dissappeared.
Top: Eastern Sahul megafauna, the foreground features Paludirex about to ambush a giant kangaroo (Ryan Bargiel, Vlad Konstantinov, Andrey Atuchin & Scott Hocknull)
Bottom left: Paludirex vincenti (Diego Ortega Anatol)
Bottom right: An unforunate Paludirex being attacked by a marsupial lion (Joschua Knüppe)
As with many crocs, its pretty likely that individuals were hostile towards each other at certain times, perhaps during territorial disputes or in the mating season. Now this one's a bit of a more ambiguous one regarding the assignment of the fossils. Fossils of leg material show clear bite marks, HOWEVER, the fossils were assigned to Pallimnarchus purely on the basis that they don't appear to have belonged to a terrestrial animal (as often inferred for Quinkana) nor to a modern croc. Based on this, the material was assumed to have been that of Pallimnarchus without much else to back it up. Now that Pallimnarchus is no more, it is reasonable to assume that it may be Paludirex but then again, it could also be an entirely different animal. Only way to tell would be to find Paludirex fossils with leg fossils attached.
This does bring up the interesting discussion, what crocs did coexist with Paludirex? Well there's a couple. As just mentioned, there's Quinkana, which I'll research more in depth later, but for now it's commonly assumed to be more terrestrial than other mekosuchines. There's the Darling Downs form, which lived around the same time as Paludirex vincenti in Queensland and may be a third species of this taxon. Gunggamarandu is another animal from this region, tho much as with Paludirex its not entirely clear if its Pliocene or Pleistocene. More certain is the fact that during the Pleiostocene, Paludirex gracilis coexisted with freshwater crocodiles in the Riversleigh WHA. Finally, there's indetermined species of crocodiles that date as far back as the Pliocene. Historically, they've been regarded as salties, but more recently it's though that they were a different species entirely and that salties only moved in recently, possibly after Paludirex went extinct and the niche of large semi-aquatic predator was free.
Top left: Quinkana faces off against Megalania (Hodari Nundu)
Top right: A freshwater crocodile running (Brandon Sideleau)
Bottom: Gunggamarandu, a relative of today's gharials (Eleanor Pease)
By this point I've basically already given away the reason why Paludirex is no more. With mekosuchines already taking a massive hit during the late Miocene, the group was not at its peak when Paludirex came around. And things were not getting any better as Australia grew more and more arid, river systems disappearing, freshwater drying up and the habitat of these animals shrinking bit by bit. Paludirex, presumably staying clear of coastal waters, was hit hard by these events and eventually it was just too much. And once it was out, saltwater crocodiles moved in, leading into the modern day.
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20/09/23 - Photo 1 - juvenile camouflaged against the bark
We've had lichen spiders on this tree for years. Recently I saw an adult guarding an egg sac, and I was excited for them to hatch. Sadly I was away when the hatch occurred. But! I still managed to find a juvenile on the tree.
24/08/23 - Photos 2-3 - adult guarding the egg sac by sitting on top of it
The adult lichen spiders are already well-hidden, but trying to find juveniles is almost impossible. I may have missed this hatching, but I have recorded a previous hatch:
(link)
24/08-20/09/23 - Pandercetes gracilis
QLD:WET
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#Archovember Day 14 - Leptoceratops gracilis
The Leptoceratopsids were a basal family of ceratopsians that, even though they looked quite primitive, lived in the Late Cretaceous. Their type species is Leptoceratops gracilis, who lived in Western North America. They had a powerful bite, used for shearing and crushing tough plant material. No doubt their sharp parrotlike beak could also be used for defense as well. Fossils from the Hell Creek Formation show that these small ceratopsians actually socially raised their young in burrows! A predator may have been less inclined to stick its nose in a burrow with an open staple remover sticking out of it! Leptoceratops could also rear up on its hind legs and even run like this when necessary.
Living in Western North America, Leptoceratops would have lived alongside many familiar dinosaurs. It would have lived alongside (or underneath) its ceratopsian cousins Triceratops and Torosaurus, ankylosaurians like Ankylosaurus and Denversaurus, pachycephalosaurs like Pachycephalosaurus and Platytholus, other ornithischians like Edmontosaurus and Thescelosaurus, ornithomimids like Struthiomimus and Ornithomimus, and oviraptorosaurs like Anzu. Being so small, Leptoceratops would have had a lot of predators to look out for, making its burrows and sharp beak very handy. It was the perfect size for not only large dromaeosaurs like Dakotaraptor, but also for the famous Tyrannosaurus rex.
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