Arenysuchus

Arenysuchus (meaning "Arén crocodile") 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 site, and "suchus", from Greek meaning crocodile. The specific name honours the researchers who discovered the holotype.

Arenysuchus
Temporal range: Late Cretaceous, 67.6–66 Ma
Arenysuchus
Skull (ELI-1) and diagram
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Eusuchia
Family: Allodaposuchidae
Genus: Arenysuchus
Puértolas, Canudo & Cruzado-Caballero, 2011
Type species
Arenysuchus gascabadiolorum
Puértolas, Canudo & Cruzado-Caballero, 2011

Etymology

Arenysuchus was named and described in 2011 by Eduardo Puértolas and his colleagues for a partial skull and teeth. For the generic name, Areny is named after Arén, spelt as Areny in the Catalan language, the locality where the skull was found, and souchus, the Greek word for crocodile, leading to Latin, suchus. The specific epithet of "gascabadiolorum" is dedicated to the researchers José Manuel Gasca and Ainara Badiola, who discovered the holotype.[1]

Description

Arenysuchus gascabadiolorum
Holotype skull ELI-1 in two other views

Arenysuchus is known a partial skull and four teeth. One feature linking it to early crocodilians is the contact of the frontal bones 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 bones, 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 bones are unusually wide in comparison to their length. Below the supratemporal fenestrae are the Infratemporal fenestra, 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 crocodiles 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.[1]

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 frontal bone 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 margin of the orbits and the prefrontal bone, at the height of the anterior end of the lacrimal bone.[1]

Phylogeny

Crocodyloidea
Cladogram with skull diagrams

In Puértolas, Canudo & Cruzado-Caballero's phylogenetic analysis, Arenysuchus was found to be one of the most basal members of Crocodyloidea, the superfamily of crocodilians that includes crocodiles 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:[1]

Crocodylia

Borealosuchus

Gavialoidea

Allodaposuchus

Pristichampsus

Brevirostres

Alligatoroidea

Crocodyloidea

Prodiplocynodon

Asiatosuchus

Arenysuchus

"Crocodylus" affinis

Brachyuranochampsa

"Crocodylus" acer

Tomistominae

Australosuchus

"Crocodylus" megarhinus

Crocodylus

Voay

Osteolaemus

Paleobiology

Arenysuchus was part of an initial evolutionary radiation 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 metasuchians comprising the dominant fauna. Crocodilians were entirely absent from Europe before this time. Dinosaurs were abundant, with a diversity of sauropods, theropods, and ornithopods. With the formation of the archipelago, 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.[1]

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.[1]

Paleoecology

Arenysuchus site
Excavation site

The Elias site, located west of Arén, is on the west end of the Tremp Syncline. Geographically, the site is located in Unit 2 of the Tremp Formation, 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 900 m (3,000 ft) of reddish rock in the South Pyrenean central Unit. Lower in the formation is a mix of platform marine deposits, that are late Campanian to Maastrichtian in age. Blasi 1 is located in the upper Arén Formation, with Blasi 3 extending into the upper Tremp Formation.[1]

The Tremp Formation dates to the late Cretaceous. 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.[1]

References

  1. ^ a b c d e f g h Puértolas, E.; Canudo, J.I.; Cruzado-Caballero, P. (2011). Farke, Andrew A. (ed.). "A New Crocodylian from the Late Maastrichtian of Spain: Implications for the Initial Radiation of Crocodyloids". PLoS ONE. 6 (6): e20011. doi:10.1371/journal.pone.0020011. PMC 3110596. PMID 21687705.
Aegyptosuchidae

Aegyptosuchidae is an extinct family of eusuchian crocodyliforms from the Cretaceous period of Africa. They are characterized by their large size and flat heads. The family includes two genera, Aegyptosuchus and Aegisuchus.

Albertosuchus

Albertosuchus is an extinct genus of crocodyloid crocodylian from the Late Cretaceous of Canada. The type species Albertosuchus knudsenii was named in 2015 from the Scollard Formation in Alberta. Albertosuchus is the northernmost-known Late Cretaceous crocodylian in North America. Albertosuchus lacks the notch in the upper jaw between the maxilla and premaxilla bones that is characteristic of most crocodyloids, and it also has a very short mandibular symphysis (the connection between the two halves of the lower jaw). Phylogenetic analysis indicates that it is one of the most basal members of Crocodyloidea and a close relative of Arenysuchus from the Late Cretaceous of Spain, although the incomplete nature of known material makes these findings uncertain.

Alligatorium

Alligatorium is an extinct genus of atoposaurid crocodylomorph from Late Jurassic marine deposits in France.

Allodaposuchidae

Allodaposuchidae is an extinct clade of basal eusuchians that lived in southern Europe during the Late Cretaceous (Santonian-Maastrichtian).

Allodaposuchus

Allodaposuchus is an extinct genus of crocodyliforms that includes four species that lived in what is now southern Europe during the Campanian and Maastrichtian stages of the Late Cretaceous. Although generally classified as a non-crocodylian crocodylomorph, it is sometimes placed as one of the earliest true crocodylians. Allodaposuchus is one of the most common Late Cretaceous crocodylomorphs from Europe, with fossils known from Spain, Romania, and France.

Amphicotylus

Amphicotylus is an extinct genus of goniopholidid mesoeucrocodylian from the Tithonian of Colorado and Oklahoma.

Anthracosuchus

Anthracosuchus (meaning "coal crocodile" in Greek) is an extinct genus of dyrosaurid crocodyliform from the Paleocene of Colombia. Remains of Anthracosuchus balrogus, the only known species, come from the Cerrejón Formation in the Cerrejón mine, and include four fossil specimens with partial skulls. Anthracosuchus differs from other dyrosaurids in having an extremely short (brevirostrine) snout, widely spaced eye sockets with bony protuberances around them, and osteoderms that are smooth and thick. It is one of the most basal dyrosaurids along with Chenanisuchus and Cerrejonisuchus. The species name is a reference to the Balrog, a creature in J. R. R. Tolkien's fantasy novel The Lord of the Rings that could, like the remains of Anthracosuchus, be found in a mine.

Atoposauridae

Atoposauridae is a family of crocodile-line archosaurs belonging to Neosuchia. The majority of the family are known from Late Jurassic to Early Cretaceous marine deposits in France, Portugal, and Bavaria in southern Germany. The discovery of the genus Aprosuchus, however, extends the duration of the lineage to the end of the Cretaceous in Romania.

Brillanceausuchus

Brillanceausuchus is an extinct genus of atoposaurid crocodylomorph. Fossils have been found in Early Cretaceous–age rocks of Cameroon. The genus is notable for the position of the secondary choana within its palate. Parts of the pterygoid bones make up the rostral margin of the choana and thus separate it from the palatines, a feature also seen in the more advanced neosuchian suborder Eusuchia. This characteristic was once thought to be characteristic of Eusuchia, but its presence in Brillanceausuchus suggests that the trait is homoplasic, thus making the evolution of the position of the choana within crocodilians more complex than previously thought.

Coelosuchus

Coelosuchus is an extinct genus of goniopholidid mesoeucrocodylian. Fossils have been found from the Graneros Shale of the Benton Group in Wyoming, and are of Cenomanian age. It was slightly over 1 meter in length.

Eusuchia

The Eusuchia ("true crocodiles") are a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades died out 35 and 11 million years ago, all living crocodilian species are eusuchians, as are many extinct forms.

Karatausuchus

Karatausuchus is an extinct genus of atoposaurid crocodylomorph. It is known from a single specimen discovered in the Late Jurassic (Oxfordian - Kimmeridgian) Karabastau Svita from the vicinity of Mikhailovka in the Karatau Mountains of southern Kazakhstan. The type specimen is PIN 25858/1, a complete but poorly preserved juvenile skeleton with some possible soft tissue preservation. It is notable for having over 90 teeth, but its other anatomical details are difficult to discern. The length of this individual is estimated at 160 millimetres (6.3 in). Karatausuchus was described in 1976 by Mikhail Efimov, and the type species is K. sharovi.

Khoratosuchus

Khoratosuchus is an extinct genus of neosuchian crocodylomorph which existed in northeast Thailand during the early Cretaceous period. Its type species is Khoratosuchus jintasakuli. Khoratosuchus is the youngest and most advanced Mesozoic crocodyliform yet known from Thailand. It possesses several distinctive features that help determine its phylogenetic position among crocodylomorphs, including secondary choanae relatively posterior and almost encircled by the pterygoid bones on the palate and a smooth dorsal surface of the skull.

Laganosuchus

Laganosuchus is an extinct genus of stomatosuchid crocodyliform. Fossils have been found from Niger and Morocco and date back to the Upper Cretaceous.

Nannosuchus

Nannosuchus (meaning "dwarf crocodile") is an extinct genus of goniopholidid mesoeucrocodylian from the Berriasian of England.

Sabresuchus

Sabresuchus is an extinct genus of neosuchian crocodyliform from the Cretaceous of Europe. The name is derived from 'Sabre' in reference to the enlarged and curved fifth maxillary tooth, and 'suchus' from the Ancient Greek for crocodile.

Symptosuchus

Symptosuchus is an extinct genus of goniopholidid mesoeucrocodylian. It is known from the Late Cretaceous of Argentina. Argentine paleontologist Florentino Ameghino named the genus in 1899, along with the type species S. contortidens. It was formally described by Carlos Rusconi in 1934.

Wahasuchus

Wahasuchus is a genus of extinct mesoeucrocodylian of the Middle Campanian age found in the Quseir Formation, Egypt. The generic name derives from the Arabic word واحة (waha), which means "oasis", and souchos from the Greek in honor of crocodile-headed god of ancient Egypt. The specific egyptensis (Lat.) means from Egypt.Fossils of skull and jaw fragments, dorsal vertebrae, and fragmentary appendicular remains have been recovered.

Extinct crocodilian species

Languages

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.