Rauisuchidae in the context of Batrachotomus

Chirotherium, also known as Cheirotherium (‘hand-beast’), is a Triassic trace fossil consisting of five-fingered (pentadactyle) footprints and whole tracks. These look, by coincidence, remarkably like the hands of apes and bears, with the outermost toe having evolved to extend out to the side like a thumb, although probably only functioning to provide a firmer grip in mud. Chirotherium tracks were first found in 1834 in Lower Triassic sandstone (Buntsandstein) in Thuringia, Germany, dating from about 243 million years ago (mya).

The creatures who made the footprints and tracks were probably pseudosuchian archosaurs related to the ancestors of the crocodiles. They likely belonged to either prestosuchidae or rauisuchidae groups, which were both large carnivores with semi-erect gaits.

Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians (the other main group of archosaurs is Avemetatarsalia, the lineage that includes all archosaurs more closely related to birds than to crocodilians). Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found.

It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time (such as Coelophysis). It was a hunter that probably preyed on large, bulky herbivores such as dicynodonts and many other creatures smaller than itself (such as early dinosaurs). The skeleton of Postosuchus is large and robust, with a deep skull and a long tail. It was a large animal, up to 5–6 m (16–20 ft) long or even more. The extreme shortness of the fore limbs relative to the hind limbs, the very small fore paws, and measurements of the vertebrae suggest that Postosuchus may have been committed to bipedal locomotion.

Prestosuchidae (in its widest usage) is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres (8.2 to 23.0 ft) in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.

In 2011, Prestosuchidae in its broadest definition was determined to be a poorly-diagnosed and obsolete polyphyletic group of pseudosuchians (crocodilian-lineage archosaurs) leading to the more "advanced" rauisuchids and crocodylomorphs. Some studies since then have reintroduced the term Prestosuchidae in a more limited setting. In these studies it refers to a clade containing Prestosuchus, Saurosuchus, and Luperosuchus. Even so, the validity of this clade is unclear, and it is often not supported over a paraphyletic arrangement of its constituents.