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Barinasuchus
Barinasuchus (meaning "Barinas crocodile", in reference to where the type material was found) is an extinct genus of sebecid mesoeucrocodylian. The first specimen of Barinasuchus was recovered from the Miocene Ipururo Formation of Peru, and was described in 1977 by Éric Buffetaut and Robert Hoffstetter, though was originally assigned to Sebecus. Another specimen was recovered from the Eocene-age Divisadero Largo Formation of Argentina in 1984 by Zulma Brandoni de Gasparini. The type specimen was recovered from the Miocene-age Parángula Formation, and was described in 1982 by Alfredo Paolillo and Omar J. Linares. Barinasuchus' body length has been estimated, based on comparisons with other crocodyliforms, at between 6.3–10 m (21–33 ft), though smaller estimates of 3–4 m (9.8–13.1 ft) have been suggested. Its body mass may have ranged from 1,610–1,720 kg (3,550–3,790 lb), making it considerably larger than any terrestrial predatory mammal alive today. Barinasuchus was heterodont, meaning that it possessed two types of teeth. Those of the premaxilla and the front of the maxilla were longer and more conical than those further back, which were shorter and thinner. The fourth mandibular (lower jaw) tooth was very large, and slotted into a prominent notch between the premaxilla and maxilla when the jaws were closed. Discovery and namingIn 1977, Éric Buffetaut and Robert Hoffstetter published on a sebecid specimen recovered from the Ipururo Formation of eastern Peru,[1] dated to the middle Miocene.[2] The specimen was referred to as Sebecus cf. huilensis, though no specimen number was provided, and it has since fallen into the hands of a private collector.[2] In 1982, locals living near a tributary of the Rio Masparro river in Venezuela, near the eastern foothills of the Andes, discovered the anterior (front) half of a skull and mandible. The strata from which the specimen (MAAT-0260) was recovered have been dated to the middle Miocene, specifically the Friasian South American Land Mammal Age, and are part of the Parángula Formation.[2] In 2007, as part of a paper describing multiple genera of South American sebecids, Alfredo Paolillo and Omar J. Linares described the latter specimen, and assigned it to a taxon of its own, Barinasuchus arveloi. Buffetaut and Hoffstetter's specimen was assigned to the same taxon. The binomial name refers to Barinas, the Venezuelan state from which the holotype is known, and Alberto Arvelo Torrealba, a local educator and the namesake of the museum where it is housed.[2] Another Barinasuchus specimen, initially assigned to Sebecosuchia indet. by Zulma Brandoni de Gasparini in 1984,[3] is known from middle Eocene-age strata of Argentina's Divisadero Largo Formation.[2] Description A total body length of anywhere from 6.3–10 m (21–33 ft) has been estimated for Barinasuchus arveloi based on extrapolations from more complete sebecosuchians, like Stratiotosuchus.[4] However, a more conservative body size of 3–4 m (9.8–13.1 ft) has since been put forward, resulting in a similar body size to Dentaneosuchus.[5] The absence of postcranial remains makes estimating Barinasuchus' body mass extremely difficult, and efforts must by necessity rely on anatomical proxies.[6] Based on their initial body size estimates, and a method of estimating crocodilian body mass put forward by Paul Sereno et al. in 2001 (which uses the lengths of Striatosuchus and Crocodylus porosus as reference points),[7] Ralph Molnar and Felipe Mesquita de Vasconcellos provided a estimate mass of 1,610–1,720 kg (3,550–3,790 lb). Even taking a margin of error of 50% into account, this would make Barinasuchus larger than any (extant) terrestrial predatory mammal.[4]  Skull and dentitionThe holotype skull, as preserved and measured from the anterior tip of the rostrum to the posterior (rear) end of the damaged surangular, measures 70 cm (28 in) in length, and 41 cm (16 in) in height.[2][5] Based on these dimensions, Barinasuchus likely had a total skull length of about 1 m (39 in).[5] Its rostrum was tall and laterally compressed, a condition which, in crocodyliforms, is referred to as being oreinirostral. This condition is similar to that of most other sebecids, including such as Langstonia and Sebecus (with the exception of Sahitisuchus).[8] The nasals are curved, forming a narrow dome shape.[9] The premaxillae were short and high, and their junction with the maxilla bore a prominent notch, which accommodated the fourth mandibular tooth. The maxillae were fairly short, and were very high posteriorly. The pterygoid cavity was large and concave, and was broader posteriorly. The basisphenoids, two bones that lie between the basioccipital and presphenoid bones, were strongly compressed. Barinasuchus' mandible was very robust, and was widest and highest at the level of the fourth mandibular tooth.[2] Barinasuchus' dentition was heterodont, meaning that multiple tooth morphologies were present. The teeth of the premaxilla and the anterior portion of the maxilla are more conical than those of the posterior portion of the maxilla, which are shorter and more laterally compressed. All of the teeth were laterally compressed, particularly those of the posterior maxilla. The fourth mandibular tooth was the largest (out of both upper and lower jaws), and was curved. Due to how the holotype of Barinasuchus is preserved, the lower dentition, beyond the fourth mandibular tooth, is not known.[2] ClassificationIn 2014, Diego Pol and his colleagues made a phylogenetic analysis, integrating many of the new genera and species found in the early 2010s. Compiling various phylogenetic studies in order to make a matrix that included 109 genera of Crocodyliforms, of which 412 morphological characteristics were studied. Notosuchia according to Diego Pol et al. includes 45 genera and 54 species.[10] In their cladogram, Barinasuchus is classified as a Sebecosuchian belonging to the family Sebecidae, close to the Lorosuchus genus and forms a sister taxon to the genera of Ayllusuchus and Bretesuchus, indicating that Barinasuchus belonged to a distant, basal lineage within the family.[10] Cladogram based on the study done by Kellner et al. (2014), showing the position of Barinasuchus within Sebecosuchia.[11] References
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