|Class||Chordata, Reptilia, Crocodylomorpha, Dyrosauridae|
|Name Translation||Acheron Crocodile|
|Size||Estimated to be 4-6 meters long|
Acherontisuchus is an extinct genus of dyrosaurid neosuchian from Middle to Late Paleocene deposits of Colombia. The only known species is A. guajiraensis, whose name means "Acheron crocodile of the Guajira Peninsula".
Acherontisuchus is known from six specimens UF/IGM 34 through 39 (Hastings et al. 2011 noted these six specimens may represent only a single animal), including three partial lower jawbones, four fragments of the upper jaw, fragments of 21 teeth, two ribs, one upper backbone segment, one sacral vertebra (a bone that connects the hips to the rest of the spine), ribs that attach to the sacral vertebrae, a partial hip including the ilium and ischium bones, an upper leg bone, and one metatarsal foot bone. All Acherontisuchus specimens were collected from the Cerrejón Formation within the Cerrejón coal mine of northeastern Colombia and described in 2011 in Palaeontology journal by Alexander K. Hastings, Jonathan Bloch and Carlos A. Jaramillo. It is named after the river Acheron, which in Greek mythology was a branch of the river Styx meaning "river of woe" (Acherontisuchus is thought to have lived in a large river that emptied out into the Caribbean Sea during the Paleocene). The type species A. guajiraensis is named after Guajira Peninsula where Cerrejón is located.
Acherontisuchus is found in multiple layers between coal seams, giving it a wide time distribution throughout the formation. Another dyrosaurid called Cerrejonisuchus was named from Cerrejón in 2010, but is only found in one layer of the formation. Aside from the consistently fractured fossils, no evidence exists of an altered fossil size.
Acherontisuchus is considered a long-snouted, or longirostrine, dyrosaurid. Its snout is shorter than those of Dyrosaurus, Atlantosuchus, Rhabdognathus, and Congosaurus. Some of its teeth have pronounced grooves on both sides. The upper jaw is wide rather than high. Its head is estimated to have been 72–86 centimetres (28–34 in) long, about midsize for a dyrosaurid. It grew to a relatively large size compared to most dyrosaurids, between 4.66 and 6.46 metres (15.3 and 21.2 ft).