''Chenanisuchus'' ("Chenane crocodile") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

dyrosaurid Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Late Cretaceous (Maastrichtian) to the Eocene. Dyrosaurid fossils are globally distributed, having been found in Africa, Asia, Europe, North America and South Amer ...

crocodyliform Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only pseudo ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

Mali Mali (; ), officially the Republic of Mali,, , ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, italics=no, ar, جمهورية مالي, Jumhūriyyāt Mālī is a landlocked country in West Africa. Mali ...

and the Late

Palaeocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''palai� ...

of Sidi Chenane in

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

. It was described in 2005, after expeditions uncovered it in 2000. The type species is ''C. lateroculi'' ("lateralis", lateral; "oculi", eyes), in reference to the laterally facing eyes. Currently, ''Chenanisuchus'' is the most basal known dyrosaurid.

Material

Two specimens of ''C. lateroculi'' – OCP DEK-GE 262 (

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, nearly complete skull with mandibular fragments) and OCP DEK-GE 61 (nearly complete skull) – come from the Sidi Chenane area in Morocco, which is Late Palaeocene (

Thanetian The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

) in age.Jouve ''et al.'', 2005. Fossils of ''Chenanisuchus'' were also found in

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

age strata in

, showing that ''Chenanisuchus'' survived the

Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...

Systematics

''Chenanisuchus lateroculi'' is referred to Dyrosauridae by Jouve ''et al.'' (2005), based on three morphological characters: * Presence of occipital tuberosities * Presence of an anterolateral postorbital process * Large participation of the quadratojugal and surangular to the jaw joint

Palaeobiology

''Chenanisuchus lateroculi'' has an estimated adult length between 4 and 4.5 meters, based on the 60 centimeter long skull. It has the shortest snout relative to the dorsal skull length among all dyrosaurids, but its snout is thicker and its skull less slender than in dyrosaurids such as ''

Sokotosuchus ''Sokotosuchus'' is an extinct genus of dyrosaurid crocodyliform which existed during the Maastrichtian in western Africa. Fossils of the genus were found in the Dukamaje Formation of Nigeria, and some cranial material has possibly been found in ...

.'' There appear to be 4 teeth on each

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

, with an estimated 13 on each

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

. The teeth on the maxillae and

dentaries In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

are short and robust, but sharp. Studies of the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

morphology of Malian dyrosaurids suggest that they were adapted for walking on the sea floor as opposed to swimming, a hypothesis supported by the apparent lack of adaptations for swimming seen in other

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

crocodyliforms Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only pseudo ...

(e.g.

Metriorhynchidae Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhync ...

) such as paddlelike fins. This mode of subaqueous locomotion is suggested to have contributed to the survival of dyrosaurids such as ''Chenanisuchus'' across the K-Pg boundary.

References

Bibliography

* Jouve, S., Bouya, B. & Amaghzaz, M., (2005). A short-snouted dyrosaurid (Crocodyliformes, Mesoeucrocodylia) from the Palaeocene of Marocco. ''Palaeontology'' 48 (2): 359–369. Dyrosaurids Prehistoric pseudosuchian genera Prehistoric marine crocodylomorphs Late Cretaceous crocodylomorphs of Africa Paleocene reptiles of Africa Paleocene crocodylomorphs Fossil taxa described in 2005 {{paleo-archosaur-stub Fossils of Mali