The genus Atractosuchus is widespread across Dome 4, being represented by at least five species that come in varying sizes and forms. These animals I named Kriechhechte, as they greatly resemble gars in the general shape of their heads, but this is just a case of convergent evolution. As their limbs show, these fish are actually lobe-finned and finer anatomical details suggest they might descend tetrapodomorphs, most likely Rhizodontida. While rhizodonts were fairly primitive members of our family tree, the Kriechhechte seem to have convergently evolved some characteristics of true tetrapods. Most conspicuously, the pectoral fins have adapted into a sort of proto-arms capable of raising the fish out of water, though instead of true hands with fingers they still have lepidotrichs. More subtle is the fact that the shoulder-girdle is separated from the skull, giving the animal a true neck. The rest of the body is very conservative by comparison, preserving the general shape of the Paleozoic sarcopterygians.
The most well-known member is the Riesenkriechhecht (Atractosuchus gigas), whose size can vary between 3 and 6 meters, comparable to a saltwater crocodile. Riesenkriechhechte are found in almost all wetland areas of Dome 4, where they act as large riparian predators. While a lot of their prey consists of smaller fish, a common hunting tactic for them is also to ambush terrestrial prey from the water. It is interesting that amphibious fish occupy a niche in Dome 4 that on Earth was usually occupied by large amphibians or reptiles. The dominance of terrestrial placoderms and the lack of tetrapods may have precluded the evolution of crocodile-shaped predators out of terrestrial creatures for a long time, thereby opening this niche to be exploited by these creatures. The fossil record might be telling a different story, however. The strata show that kriechhechte of essentially modern form have existed in Dome 4 for at least 300 million years, but for the majority of that time they were rather small and rare. The role of large, semi-aquatic ambush predators was instead occupied by haruspicamorph placoderms. About 80 million years ago, however, large, sometimes very large, atractosuchids start appearing, while haruspicamorphs gradually decline. This competition may have been what initially forced haruspicamorphs to adapt to land again in the form of munchers. 70 million years ago a mass extinction swept away all aquatic haruspicamorphs, while atractosuchids went relatively unharmed. For the following millions of years they would rule the waterways unchallenged. Today riesenkriechhechte do however face a perhaps relatively new competitor in the form of the crocomire, which, as big and bulky as it looks, seems to be another placoderm-answer to this riparian lifestyle. As a fully grown crocomire is too big and armoured to be harmed by an Atractosuchus, the two usually leave each other alone, but during mating season crocomires become excessively moody and aggressive and will often let out their anger at kriechhechte that were just minding their own business. In turn the kriechhechte will prey on juvenile crocomires and injured adults. Some kriechhechte have been observed deliberately killing baby crocomires, even when they were close to their mothers or easier prey was available, suggesting that they instinctually sabotage the reproduction of their competition. Crocomires cannot really do the same in turn. Kriechhechte are ectotherms who can lay thousands of eggs upon spawning, while crocomires are mesotherms who give live birth to only a handful of young, so crocomires cannot even dent the population sizes of kriechhechte. The fiercest competition a riesenkriechhecht faces is in reality from its own kind. Fights over carcasses can become very brutal and cannibalism is indeed quite common. On occassion some kriechhechte have nonetheless been observed working together to drown a larger animal, a behaviour reminiscent of Nile crocodiles.
Riesenkriechhechte spend a surprising amount of time out of the water basking on the shore, shifting around with their strong pectoral fins and breathing with their well-developed lungs. They mostly do this with their mouth open so that their teeth and jaws may be cleaned by celaenosaurs and their hide picked clean off parasites by stoutbills (a type of chimaera fly). Despite its terrestrial capabilities, A. gigas never ventures too far from the water and unlike its smaller relatives it is difficult for it to relocate to a new body of water should its old one dry out. Unlike crocomires, who can just walk from place to place, the range of riesenkriechhechte is therefore limited to stretches of water that stay wet all-year-round. In contrast, they do seem to be able to cross saltwater, as they are found on nearly all landmasses in Dome 4.