Arenysuchus
Encyclopedia
Arenysuchus is an extinct genus
of crocodyloid
from Late Cretaceous
(late Maastrichtian
stage) deposits of north Spain
. It is known from the holotype
MPZ ELI-1, a partial skull
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
, in Arén
of Huesca, Spain. It was first named by Eduardo Puértolas, José I. Canudo and Penélope Cruzado-Caballero in 2011
and the type species
is Arenysuchus gascabadiolorum. The generic name refers to the finding place, and "suchus", from Greek
meaning crocodile
. The specific name honours the researchers who discovered the holotype.
s with the margin of the supratemporal fenestrae, 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
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
s are unusually wide in comparison to their length. Below the supratemporal fenestrae are the infratemporal fenestrae, long openings along the side of the skull behind the eyes. The infratemporal bar (a projection of the jugal
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
, or eye sockets, are raised. The orbit edges of more advanced crocodyloids like modern crocodile
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
, a bony plate of the maxilla
that forms the front portion of the palate
. 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 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.
members of Crocodyloidea
, the superfamily of crocodilia
ns that includes crocodile
s and their extinct relatives. Other basal crocodyloids include Prodiplocynodon
and "Crocodylus" affinis from North America
and Asiatosuchus
from Europe
. Of these genera, only Arenysuchus and Prodiplocynodon are known from the Late Cretaceous
, making them the earliest known crocodyloids. Below is a cladogram
after Puértolas, Canudo & Cruzado-Caballero, 2011:
of crocodylians in the Northern Hemisphere during the Late Cretaceous. During the late Maastrichtian
, Europe was an island archipelago
surrounded by shallow seas. In this archipelago, crocodilians made up the majority of the crocodylomorph fauna. In the southern hemisphere, however, crocodilians were not yet common, with other crocodylomorphs like metasuchia
ns comprising the dominant fauna. Crocodilians were entirely absent from Europe before this time. Dinosaur
s were abundant, with a diversity of sauropods, theropods, and ornithopod
s. With the formation of the archepelago, a faunal turnover took place in the late Maastrichtian. Dinosaurs became much rarer, primarily represented by hadrosaurs. Crocodylians radiated to become a much larger component of the island ecosystems.
With the exception of Prodiplocynodon, Late Cretaceous North American crocodylians were mostly alligatoroids and gavialoids. In what is known as vicariance
, migration did not occur between Europe and North America, separating the two crocodilian faunas. It was not until the Paleocene
that crocodyloids diversified into the more derived
relatives of Arenysuchus.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of crocodyloid
Crocodyloidea
Crocodyloidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Crocodylus niloticus and all crocodylians more closely related to C. niloticus than to either Alligator mississippiensis or Gavialis gangeticus .- Phylogeny :Cladogram after...
from Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
(late Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage) deposits of north Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
. It is known from the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
MPZ ELI-1, a partial skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
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
Tremp Formation
The Tremp Formation is a geological formation in Huesca, Spain whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation....
, in Arén
Arén
Arén or Areny de Noguera is a municipality located in the province of Huesca, Aragon, Spain. According to the 2004 census , the municipality has a population of 364 inhabitants.-Villages:These include uninhabited villages:...
of Huesca, Spain. It was first named by Eduardo Puértolas, José I. Canudo and Penélope Cruzado-Caballero in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
and the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is Arenysuchus gascabadiolorum. The generic name refers to the finding place, and "suchus", from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
meaning crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
. The specific name honours the researchers who discovered the holotype.
Description
Arenysuchus is known a partial skull and four teeth. One feature linking it to early crocodilians is the contact of the frontal boneFrontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
s with the margin of the supratemporal fenestrae, 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
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 form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
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
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
s are unusually wide in comparison to their length. Below the supratemporal fenestrae are the infratemporal fenestrae, long openings along the side of the skull behind the eyes. The infratemporal bar (a projection of the jugal
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....
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
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
, or eye sockets, are raised. The orbit edges of more advanced crocodyloids like modern crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
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
Palatine process of maxilla
The palatine process of the maxilla , is a thick, horizontal process of the maxilla. It forms the anterior three-fourths of the hard palate, the horizontal plate of the palatine bone making up the rest....
, a bony plate of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
that forms the front portion of the palate
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 separate. The palate is divided into two parts, the anterior...
. 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 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.
Phylogeny
In Puértolas, Canudo & Cruzado-Caballero's phylogenetic analysis, Arenysuchus was found to be one of the most basalBasal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
members of Crocodyloidea
Crocodyloidea
Crocodyloidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Crocodylus niloticus and all crocodylians more closely related to C. niloticus than to either Alligator mississippiensis or Gavialis gangeticus .- Phylogeny :Cladogram after...
, the superfamily of crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns that includes crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s and their extinct relatives. Other basal crocodyloids include Prodiplocynodon
Prodiplocynodon
Prodiplocynodon is an extinct genus of basal crocodyloid crocodylian. It is the only crocodyloid known from the Cretaceous and existed during the Maastrichtian stage. The only species of Prodiplocynodon is the type species P...
and "Crocodylus" affinis from North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Asiatosuchus
Asiatosuchus
Asiatosuchus is an extinct genus of large crocodilian. It is believed to have been a basal crocodile. Specimens have been found from Russia, Belgium, France, Germany, Mongolia, and possibly Pakistan. It existed from the Danian stage of the early Paleocene epoch to the Lutetian stage of the Eocene...
from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Of these genera, only Arenysuchus and Prodiplocynodon are known from the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
, making them the earliest known crocodyloids. Below is a cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
after Puértolas, Canudo & Cruzado-Caballero, 2011:
Paleobiology
Arenysuchus was part of an initial evolutionary radiationEvolutionary radiation
An evolutionary radiation is an increase in taxonomic diversity or morphological disparity, due to adaptive change or the opening of ecospace. Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment,...
of crocodylians in the Northern Hemisphere during the Late Cretaceous. During the late Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
, Europe was an island archipelago
Archipelago
An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...
surrounded by shallow seas. In this archipelago, crocodilians made up the majority of the crocodylomorph fauna. In the southern hemisphere, however, crocodilians were not yet common, with other crocodylomorphs like metasuchia
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 dentitions. Neosuchia includes extant crocodylians and basal taxa such...
ns comprising the dominant fauna. Crocodilians were entirely absent from Europe before this time. Dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s were abundant, with a diversity of sauropods, theropods, and ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
s. With the formation of the archepelago, a faunal turnover took place in the late Maastrichtian. Dinosaurs became much rarer, primarily represented by hadrosaurs. Crocodylians radiated to become a much larger component of the island ecosystems.
With the exception of Prodiplocynodon, Late Cretaceous North American crocodylians were mostly alligatoroids and gavialoids. In what is known as vicariance
Vicariance
Vicariance is a process by which the geographical range of an individual taxon, or a whole biota, is split into discontinuous parts by the formation of a physical barrier to gene flow or dispersal. Vicariance of whole biotas occurs following large-scale geophysical events such as the uplift of a...
, migration did not occur between Europe and North America, separating the two crocodilian faunas. It was not until the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
that crocodyloids diversified into the more derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
relatives of Arenysuchus.