They represented the dominant group of crocodilians in the region during most of the Cenozoic, first appearing in the fossil record in the Eocene of Australia, and surviving until the arrival of humans: the Late Pleistocene on the Australian continent and during the Holocene in the Pacific islands of Fiji, New Caledonia and Vanuatu.

[1] De Vis himself only coined the name "out of convenience", admitting that he was too unfamiliar with the Cenozoic crocodilian fossil record to be certain that his find represented an animal distinct from any other taxa known at the time.

This period would come to an end in 1977 with the publications of Max Hecht, Michael Archer and Ralph Molnar, all of which reported on fossil material collected from cave deposits in northern Queensland.

Following the description of Baru, scientists began to recognize shared traits among the fossil crocodiles of Australia, with Willis and colleagues proposing the presence of what they dubbed the Australian Tertiary crocodylian radiation.

At their simplest mekosuchines greatly resemble modern crocodiles, with taxa such as Kambara,[12][17] Ultrastenos,[30] and Australosuchus having triangular platyrostral skulls, meaning that they are flattened, with both the nostrils and eyes mostly facing upwards.

[28] This is contrasted by a 2023 publication by Yates, Ristevski & Salisbury, who found Kambara and Australosuchus to form their own small clade at the base of the group with Kalthifrons diverging at a slightly later time.

The more traditional of these clades includes various medium- to large-sized taxa from continental Australia, namely Kalthifrons, Quinkana, Baru and Paludirex, not dissimilar to the other trees recovered by Ristevski et al..

By 1993, when Mekosuchinae was coined to include all other Australian Cenozoic crocodilians known at the time, the clade was placed in the family Crocodylidae and regarded as a mere subfamily, a view that remained prominent in literature in subsequent years.

Salisbury and colleagues have previously suggested that Mekosuchus might have been more salt tolerant due to the lack of permanent freshwater sources on New Caledonia, however, assuming that the genus was more terrestrial as frequently speculated, the absence of fresh water might have been less crucial.

An alternative hypothesis suggests that mekosuchines arrived on Fiji, Vanuatu and New Caledonia through the act of rafting (being carried there by clinging to drift wood and similar structures) or island hopping.

[18][22][41][50] Although most mekosuchines exhibit hallmark traits of being semi-aquatic animals, possessing flattened skulls with nares and eyes directed more upward, there are some genera which might suggest that a more land-based lifestyle arose in some branches of the family.

Despite being widely recognized as semi-aquatic with a classically crocodilian head suited for such life, Kambara also featured certain peculiar adaptations to its limbs that could have facilitated much easier travel across land relative to modern crocodiles.

[53] In the case of Kambara specifically, the hips represent the plesiomorphic condition and greatly resemble those of gharials and alligators, with later mekosuchines seemingly either diverging into more terrestrial forms or converging with modern crocodiles.

[51] Lucas A. Buchanan, who described Kambara taraina, notes in his PhD thesis that the animal does not show any other notable adaptations for terrestrial life and sticks close to the anatomy of modern salt- and freshwater crocodiles in many aspects.

[54] A final clue against overly terrestrial habits in Kambara is the fact that most individuals are known from a mass death site that preserves the results of a lake drying out, killing the crocodilians that previously inhabited it.

[28] Much like with Mekosuchus, the idea that Quinkana was terrestrial is primarily based on the outward appearance of the skull, which is deep and houses rows of ziphodont teeth (meaning they were blade-lake compressed with prominent serrations along the cutting edge).

In this work, Wroe first argues against a prior argument by Molnar and Willis that reptiles were the top predators of Australia, highlighting the relative rarity of Megalania and Quinkana remains to those of marsupials.

Lucas A. Buchanan suggests that among the four Kambara species, those with interlocking teeth (K. implexidens and K. taraina) might be better adapted to grasp and restrain large struggling prey whereas the overbite seen in K. murgonensis could be employed to cut and slice.

The patterns left on the turtle's carapace suggest that Kambara engaged in behavior known as juggling, the act of repeatedly biting prey in a fashion that would align it with the teeth in the back of the jaw, allowing the animal to break through the robust shell.

These robust jaws, slicing teeth and the pronounced festooning might have aided Baru in tackling large prey items and dispatching it quickly by inflicting massive amounts of trauma.

[7] Busbey and Willis both draw comparison to modern komodo dragons[14][28] while Stein and colleagues suggest that ziphodont dentition might be tied to cursorial hunting habits, chasing after prey rather than ambushing it.

[13] Similarly, Mekosuchus whitehunterensis' musculature has been in interpreted as an adaptation to rip flesh from carcasses, either through the same sideways movements as inferred for Trilophosuchus or by using the traditional crocodilian death roll, although it would have been notably less effective due to the small size of the animal.

This is further supported by specific adaptations to the muscle attachments in M. whitehunterensis and the simple fact that the inferred terrestrial habits of the animal would render a death roll much more dangerous if performed on land relative to in the water.

[41] The posterior dentition of Volia from Fiji might have also been suited to cracking small molluscs and insect cuticles, tho its just as possible that it was a terrestrial hunter, employing its slender, compressed teeth to dispatch of the local giant iguanas and flightless birds.

In the original description of Ultrastenos, it is highlighted how despite the abundance of freshwater biomes, the Riversleigh WHA is poor in fossil fish, with the authors proposing that a narrow rostrum could have been used to catch frogs and other small vertebrates.

[60][61] It has been suggested that Late Oligocene and Early Miocene localities (like Low Lion and Whitehunter, home of taxa like Ultrastenos, Mekosuchus whitehunterensis, Baru wickeni and Quinkana meboldi) would fall into a dry period, and were thus dominated by open forests and woodlands,[25][60] possibly also featuring sclerophyllous vegetation and deciduous vine thickets.

[62] It is thought that the climate grew wetter during Faunal Zones B and C, leading to a more prominent lowland rainforest environment being present during the deposition of the Ringtail Site (home to Trilophosuchus, Baru darrowi and Mekosuchus sanderi).

Still, the locality is thought to have been lacustrine in nature, featuring permanent bodies of water fed by springs that in times of increased rainfall may have expanded to form an enormous but very shallow lake.

Bluff Downs has been interpreted as preserving an environment similar to today's Kakadu National Park, with Thomson and Mackness proposing suggesting the presence of riparian rainforests or vine thickets.

[68][69][70] Further south, the Lake Eyre Basin also continued to support mekosuchine populations, sharing Quinkana with Bluff Downs and also preserving the bones of Kalthifrons as the regions semi-aquatic crocodilian.