''Decuriasuchus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of

loricatan Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as ''Postosuchus'' and ''Prestosuchus''. More specifically, Loricata includes Crocodylomorpha (the persistent archosaur subset which ...

from the Middle Triassic period ( Ladinian stage). It is a

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

that lived in what is now southern Brazil, in Paleorrota. It was first named by Marco Aurélio G. França, Jorge Ferigolo and Max C. Langer in

2011 File:2011 Events Collage.png, From top left, clockwise: a protester partaking in Occupy Wall Street heralds the beginning of the Occupy movement; protests against Libyan dictator Muammar Gaddafi, who was killed that October; a young man celebrate ...

and the type species is ''Decuriasuchus quartacolonia''. The generic name means "unit of ten crocodiles" in Latin and Greek in reference to the ten known specimens and the animal's possible group behavior. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

refers to the Quarta Colonia region where the fossils were collected.

Description

''Decuriasuchus'' is known from ten specimens, including nine articulated and associated

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

s, three of which have nearly complete

skulls The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. The holotype MCN PV10105a consists of an articulated partial skeleton, lacking scapular girdle and limbs. Eight specimens associated with the holotype, MCN PV10105b-i, and the tenth specimen (MCN PV10004), consists of

cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

remains from a different spot in the same locality. The specimens were found in the Alemoa Member of the Santa Maria Formation, Rosário do Sul Group. The discovery locality is

Rio Grande do Sul Rio Grande do Sul (, , ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative_units_of_Brazil#List, fifth-most-populous state and the List of Brazilian st ...

, Brazil. Like other rauisuchids, ''Decuriasuchus'' was a quadrupedal carnivore that was one of the

top predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

s of its environment. It grew to a length of around .

Classification

''Decuriasuchus'' is closely related to the genera '' Prestosuchus'' and ''

Batrachotomus ''Batrachotomus'' is a genus of prehistoric archosaur. Fossils of this animal have been found in southern Germany and dated from the Ladinian stage of the Middle Triassic period, around 242 to 237 million years ago. ''Batrachotomus'' was descri ...

''. An initial phylogenetic study of the genus placed it in the family

Prestosuchidae 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 in length. They succeeded the Erythrosuchidae as the ...

, but found the group " Rauisuchia" to be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

. The study was based on an earlier 2010 analysis of archosaurs. A later study involved adding ''Decuriasuchus'' to a 2011 analysis of archosaur relationships; ''D. quartacolonia'' was recovered as the basalmost member of the clade Loricata (the most inclusive clade containing '' Crocodylus niloticus'' but not ''

Poposaurus gracilis ''Poposaurus'' (" Popo Agie reptile") is an extinct genus of pseudosuchian archosaur from the Late Triassic of the southwestern United States. It belongs to the clade Poposauroidea, an unusual group of Triassic pseudosuchians that includes sail-b ...

'', ''

Ornithosuchus longidens ''Ornithosuchus'' (meaning "bird crocodile") is an extinct genus of pseudosuchians from the Late Triassic ( Carnian) Lossiemouth Sandstone of Scotland. It was originally thought to be the ancestor to the carnosaurian dinosaurs (such as '' ...

'' or ''

Aetosaurus ferratus ''Aetosaurus'' is an extinct genus of pseudosuchian reptile belonging to the order Aetosauria. It is generally considered to be the most primitive aetosaur. Three species are currently recognized: ''A. ferratus'', the type species from Germany ...

''), with ''

Ticinosuchus ''Ticinosuchus'' is an extinct genus of suchian archosaur from the Middle Triassic (Anisian - Ladinian) of Switzerland and Italy. Description One of only a handful of fossil reptiles that have been found in Switzerland, ''Ticinosuchus'' (mea ...

'' as the next most primitive taxon. As a rauisuchian, ''Decuriasuchus'' is a distant relative of modern

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

Paleobiology

Nine specimens of ''Decuriasuchus'' were found in close proximity to each other. A study of the taphonomy of the site (the conditions under which the skeletons became fossilized) indicates that the assemblage represents the single burial of multiple individuals rather than the collection of unrelated remains in one spot over a longer period of time. The congregation of nine individuals in one area suggests that they may have been traveling in a group. If this were the case, ''Decuriasuchus'' would be the earliest known archosaur to exhibit group behavior.

References

{{Portal bar, Paleontology Paracrocodylomorphs Prehistoric pseudosuchian genera Triassic archosaurs Ladinian genera Middle Triassic reptiles of South America Triassic Brazil Fossils of Brazil Santa Maria Formation Fossil taxa described in 2011