''Arenysuchus'' (meaning "Arén crocodile") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of allodaposuchid

eusuchia Eusuchia is a clade of neosuchian Crocodylomorpha, crocodylomorphs that first appeared in the Early Cretaceous, which includes modern Crocodilia, crocodilians. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survi ...

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably mor ...

from Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

(late

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

stage) deposits of north

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. It is known from the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

MPZ ELI-1, a partial

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

from Elías site, and from the referred material MPZ2010/948, MPZ2010/949, MPZ2010/950 and MPZ2010/951, four teeth from Blasi 2 site. It was found by the researchers José Manuel Gasca and Ainara Badiola from the

Tremp Formation The Tremp Formation (, ), alternatively described as Tremp Group (), is a geological Formation (geology), formation in the comarca Pallars Jussà, Lleida Province, Lleida, Spain. The formation is restricted to the Tremp-Graus Basin, Tremp or T ...

, in

Arén Arén (), in Catalan: ''Areny de Noguera''As shown in thLegislative Decree 2/2006 of 27 December, of the Government of Aragon, by the revised text of the Law on Comarcal Demarcation of Aragon is approved. (), or in Aragonese: ''Arén de Noguera ...

Huesca Huesca (; ) is a city in north-eastern Spain, within the Autonomous communities of Spain, autonomous community of Aragon. It was the capital of the Kingdom of Aragon between 1096 and 1118. It is also the capital of the Spanish Huesca (province), ...

, Spain. It was first named by

Eduardo Puértolas Eduardo is the Spanish and Portuguese form of the male name Edward. Another version is Duarte. It may refer to: Association football * Dudu (footballer, born 1992) (Eduardo Pereira Rodrigues), Brazilian footballer * Eduardo (footballer, born 1 ...

José I. Canudo José is a predominantly Spanish and Portuguese form of the given name Joseph. While spelled alike, this name is pronounced very differently in each of the two languages: Spanish ; Portuguese (or ). In French, the name ''José'', pronounced , ...

and Penélope Cruzado-Caballero in

2011 The year marked the start of a Arab Spring, series of protests and revolutions throughout the Arab world advocating for democracy, reform, and economic recovery, later leading to the depositions of world leaders in Tunisia, Egypt, and Yemen ...

and the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''Arenysuchus gascabadiolorum''.

Etymology

''Arenysuchus'' was named and described in

and his colleagues for a partial skull and teeth. For the generic name, Areny is named after

, spelt as Areny in the Catalan language, the locality where the skull was found, and ''souchus'', the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word for crocodile, leading to

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, ''suchus''. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

of "gascabadiolorum" is dedicated to the researchers José Manuel Gasca and Ainara Badiola, who discovered the holotype.

Description

''Arenysuchus'' is known a partial skull and four teeth. One feature linking it to early

crocodilians Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchi ...

is the contact of the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

s with the margin of the

supratemporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

e, two holes in the top of the skull. The frontal bone is also unusual in that its front end is extremely long. A sharp projection of the frontal divides the

nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

s, making up most of the midline length of the snout. Usually, the nasal bones would occupy the midline and the frontal would be restricted near the eye sockets. Near the frontal, the

lacrimal bone The lacrimal bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...

s are unusually wide in comparison to their length. Below the supratemporal fenestrae are the

Infratemporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

, long openings along the side of the skull behind the eyes. The infratemporal bar (a projection of the

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

bone below the infratemporal fenestra) is very thin and vertically expanded. In most other crocodilians, it is thicker and laterally, not vertically, expanded. The edges of the

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

, or eye sockets, are raised. The orbit edges of more advanced crocodyloids like modern

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term "crocodile" is sometimes used more loosely to include ...

s are also raised, but those of the closest relatives of ''Arenysuchus'' are not. Another feature of ''Arenysuchus'' that distinguishes it from other basal crocodyloids is its small

palatine process In human anatomy of the mouth, the palatine process of maxilla (palatal process), is a thick, horizontal process of the maxilla. It forms the anterior three quarters of the hard palate, the horizontal plate of the palatine bone making up the rest ...

, a bony plate of the

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

that forms the front portion of the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

. The palatine process of basal crocodyloids usually extends to the suborbital fenestrae, a pair of holes on the underside of the skull beneath the orbits. In ''Arenysuchus'', the process is much shorter. ''Arenysuchus'' also has a pit between the seventh and eighth maxillary teeth that is otherwise only seen in '' "Crocodylus" affinis''. This pit would hold a

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

tooth if the lower jaw were present. All other teeth of the lower jaw are set inward from those of the upper jaw, so they are covered by the upper teeth when the jaws are closed.

Distinguishing anatomical features

''Arenysuchus'' can be distinguished by the following features: an infratemporal bar that is tabular and vertically oriented, with little dorsoventral thickness and an extreme lateromedial compression; the dorsal portion of the anterior process of the

has a very elongated and lanceolate morphology; the anterior process of the frontal projects strongly beyond the main body of the frontal and extends between the nasals, ending in a sharp point beyond the

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

margin of the orbits and the

prefrontal bone The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and ...

, at the height of the anterior end of the

Phylogeny

In Puértolas, Canudo & Cruzado-Caballero's original 2011

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis, ''Arenysuchus'' was found to be one of the most basal members of

Crocodyloidea Crocodyloidea is one of three superfamilies of crocodilians, the other two being Alligatoroidea and Gavialoidea, and it includes the crocodiles. Crocodyloidea may also include the extinct Mekosuchinae, native to Australasia from the Eocene to ...

, the

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...

ns that includes

s and their extinct relatives, which can be shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below: Alternatively, subsequent phylogenetic studies have found ''Arenysuchus'' to be the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of ''

Allodaposuchus ''Allodaposuchus'' is an extinct genus of crocodyliforms that lived in what is now southern Europe during the Campanian and Maastrichtian stages, and possibly the Santonian stage, of the Late Cretaceous. Although generally classified as a non-cro ...

'' and a member of

Allodaposuchidae Allodaposuchidae is an extinct clade of eusuchians that lived in Europe during the Late Cretaceous (Santonian-Maastrichtian). Systematics The type genus, ''Allodaposuchus'', was originally scientifically described, described in 1928 by Franz Nop ...

, as shown in the cladogram below:

Paleobiology

''Arenysuchus'' was part of an initial

evolutionary radiation An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. A significantly large and diverse radiation within ...

crocodylia Crocodilia () is an Order (biology), order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorp ...

ns in the Northern Hemisphere during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

. During the late

, Europe was an island

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...

surrounded by shallow seas. In this archipelago, crocodilians made up the majority of the

fauna. In the southern hemisphere, however, crocodilians were not yet common, with other crocodylomorphs like

metasuchia Metasuchia is a major clade within the superorder Crocodylomorpha. It is split into two main groups, Notosuchia and Neosuchia. Notosuchia is an extinct group that contains primarily small-bodied Cretaceous taxa with heterodont dentition. Neosuchi ...

ns comprising the dominant fauna. Crocodilians were entirely absent from Europe before this time.

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s were abundant, with a diversity of

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

s, and

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

s. With the formation of the archipelago, a faunal turnover took place in the late Maastrichtian. Dinosaurs became much rarer, primarily represented by

hadrosaur Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

s. Crocodylians radiated to become a much larger component of the island ecosystems.

Paleoecology

The Elias site, located west of

, is on the west end of the Tremp Syncline. Geographically, the site is located in Unit 2 of the

, and equivalent of the Conques Formation. In the same section of the Tremp Formation, but lower down, are the Blasi sites 1–3. The dinosaurs ''Arenysaurus'' and ''Blasisaurus'' are both from Blasi 1–3. The Tremp Formation is made up of of reddish rock in the South Pyrenean central Unit. Lower in the formation is a mix of platform aquatic animal, marine deposits, that are late Campanian to

in age. Blasi 1 is located in the upper Arén Formation, with Blasi 3 extending into the upper Tremp Formation. The Tremp Formation dates to the late

. It has been dated by means of planktonic foraminifers and magnetostratigraphy. The formation includes the planktonic ''Abathomphalus mayaroensis'' Biozone, which was dated in 2011 from 68.4 to 65.5 Ma. This gives the formation a late Campanian to early Danian age. The bottom of the Elias site is about 67 million years old, so the site dates from 67.6 to 65.5 Ma.

References

{{Taxonbar, from=Q1965717, from2=Q20717065 Allodaposuchidae Late Cretaceous crocodylomorphs of Europe Cretaceous Spain Fossils of Spain Tremp Formation Fossil taxa described in 2011 Prehistoric pseudosuchian genera