A female Postosuchus quenches her thirst in the Wet Season.
The Female Postosuchus appeared in the first episode of the original Walking with Dinosaurs series in 1999, titled New Blood.
Initially portrayed as the indomitable and unstoppable top predator of it's range, the large, female Postosuchus, is gradually shown to be more vulnerable to ecological pressures than she might first seem, being drawn into a confrontation with an aggressively invasive male Postosuchus, which successfully takes her territory away from her.
Hunger during the unforgiving Triassic Dry Season, and the weakness this had caused her physically, made it possible for the evidently more healthy interloper to drive her from a territory she is explained by the narration to have controlled for over a decade.
Things go from bad to worse for her, as in desperation, she makes an unsuccessful predation attempt on the local Placerias herd, and one of them wounds her in her thigh with it's sharp tusks. This slows her down even more, as the Dry Season continues to deplete the landscape, as well as her strength.
Ultimately reduced to collapsing from exhaustion, injury, starvation and dehydration, the very unwell female Postosuchus is then surrounded by a large flock of Coelophysis, which form a united front against her still lethally powerful jaws, and they collectively move in to prey on the unfortunate Postosuchus.
The female Postosuchus still tries to defend herself for a brief moment, before seemingly either passing away of natural causes or effectively becoming briefly unconscious to then be eaten alive (most likely being dead already, probably dying of heart failure and brain death, though this is not mentioned in the narration; it is simply pointed out that her strength fails her, with her essentially dying at that point), lowering her head to the dry, dusty ground.
Then, the Coelophysis waste no time in swiftly moving in, to begin feasting on her corpse. They use their long snouts and nipping, sharp teeth, to bite and pry under the thick armoured hide of the Postosuchus, 'eating her from the inside out'. They also target the softer scales on the underbelly and around the serious damage already inflicted on her thigh.
This tragic end for the Postosuchus, is used - largely erroneously, it should be pointed out - to symbolically represent the decline of the rival Archosaurian predators that shared the world of the Triassic Period with the Dinosaurs, and had dominated it before Dinosaurs truly began to come into their own hegemonic dominance in the Early Jurassic Period.
The old narrative still adhered to 'conveniently' for narrative more than scientific reasons, was that the Dinosaurs had supplanted the more 'primitive' (i.e. less-derived, more appropriately in palaeontological terms) Archosaurian relatives what we generally refer to now as the Pseudosuchia. Back in 1999, this would have been a bit more complicated to explain, with the older terminology for various animals still being used, though the 'Rauisuchia', would have been mentioned in some sources for the Postosuchus.
Postosuchus are a form of Pseudosuchian, and there are different families of Pseudosuchians which form very similar species to the Postosuchus. Some are Rauisuchians, and others are Prestosuchians. Others still go by different or as yet unclassified names. It is a broad array of largely quadrupedal yet also some bipedal, ancient Archosauromorphs and Pseudosuchians.
Postosuchus specifically, is a Rauisuchid Pseudosuchian Archosaurian. These are relatively closely related to the Dinosauromorpha (fellow Archosaurian kin) This also makes them more vaguely related to the Pterosauria, as again, fellow Archosaurian kin. However, it's a very complicated and not-fully-understood web of many similar forms and some newly emerging groups that lookalike. Dinosaurs were just one particularly successful lineage of terrestrial Archosaurs that arose from a complex array of different Archosaurians.
The old narrative (which the makers of Walking With Dinosaurs 1999 leaned into) was that the Dinosaurs simply outclassed these older kin, and inevitably took over the world - on land at least. In reality, the process was a lengthy and arduous one for the Dinosaurs to no longer be the prey items of very large Pseudosuchians. For instance, in South America (Argentina) there is a huge Pseudosuchian called Fasolasuchus tenax, a relative of Postosuchus, which was practically twice it's size. This lived around 215 Ma BP, 5 million years after the setting of Episode I - New Blood (220 Ma BP) That apex predator, over 10-11 metres long, was going about hunting early Sauropods. That was how lethal and capable such carnivores really were.
The Dinosaurs did not just overthrow these monstrously large Pseudosuchians (the largest land carnivores ever, until the Theropod Dinosaurs eventually produced much larger species, well into the Middle Jurassic, Late Jurassic and beyond into the Cretaceous) An extinction event at the end of the Triassic which wiped out the Rauisuchians, Prestosuchians and over 20-25% of reptile species at the time (including the once ubiquitous Rhynchosaurs, which were a staple of the Pseudosuchian diet in the Carnian and Norian Ages for example; as well as the Phytosaurs, crocodile-like, semi-aquatic predators which could also attain enormous sizes e.g. Smilosuchus and Colossosuchus)
Therefore, the old narrative where the Dinosaurs abruptly begin to take over the world in the Triassic, is incorrect. It made sense to symbolise the decline of the former Triassic overlords of terrestrial ecosystems, according to that narrative logic, during the production of Walking With Dinosaurs (1999), in between 1996 and 1999.
Yet the misconception this demonstrates most clearly with the 'Death of the Female Postosuchus', is more or less unfortunate, in hindsight. Inaccurate at best, dishonest at worst, through a modern lens (though it was known at least to some extent, at the time, about how evidently successful the Pseudosuchia really were) The limelight being shone on the Dinosaurs, in a series called, 'Walking With Dinosaurs', should not be too surprising however. It was a narrative means of demonstrating the alleged ecological dominance of the Dinosaurs, as a sign of their 'greatness'. Well, the truth is more complicated.
Even so, the series does specifically explain that even in the dreadful state the female Postosuchus was in just before her demise, that her powerful jaws were still more than capable of tearing a Dinosaur like the lithe little Coelophysis apart. The problem was, she was grossly outnumbered and stood no chance of escape, with her back-legs no longer functioning and being immobilised under the scorching and merciless Triassic Sun. She was already living on borrowed time in that regard - because if the Coelophysis didn't get her, then the dehydration and starvation would anyway. A sad end, to such an impressive animal.
It is possible that a skull prop of a Postosuchus, shown later on in the episode, is meant to allude to the female Postosuchus (she is the only Postosuchus we see perish in the episode, and we only see two Postosuchus in total during it's entire runtime) Therefore, it could well have been meant to show the remains of the female Postosuchus, as the Dry Season began to turn entire areas into red desert.
The area where the female Postosuchus perished, was semi-forested and still had a bit of greenery, so if that is the case, the 9 month long Dry Season (as depicted in the show) would really have pushed such wooded areas to their limits. However, it was clearly just filmed in a completely different location, so it could well have been meant as any Postosuchus and not specifically the female. It could not have been the male because he was in much better condition being uninjured and controlling the riverbed area. Even if the water ran dry there eventually, with the flow being reduced to the level of a parched and slowly evaporating stream, he'd likely be alive around the time the female Postosuchus passed away (therefore, the skull prop shown in the episode, could only be the female's, or some unknown other Postosuchus which had died off-screen)