''Phosphatosaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

dyrosaurid Dyrosauridae is a family of extinct neosuchian crocodyliforms that lived from the Late Cretaceous (Maastrichtian) to the Eocene. Dyrosaurid fossils are globally distributed, having been found in Africa, Asia, Europe, North America and South A ...

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. During Mesozoic and early Cenozoic times, cro ...

. It existed during the early

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, with fossils having been found from

North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in t ...

Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa , image_map2 = , capital = Tunis , largest_city = capital , ...

and

Mali Mali (; ), officially the Republic of Mali,, , ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, italics=no, ar, جمهورية مالي, Jumhūriyyāt Mālī is a landlocked country in West Africa. Ma ...

. Named in 1955, ''Phosphatosaurus'' is a

monotypic genus 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 ...

; the

type species In 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 species that contains the biological type specimen( ...

is ''P. gavialoides''. A specimen has been discovered from

Niger ) , official_languages = , languages_type = National languagesCretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

genus ''

Sokotosuchus ''Sokotosuchus'' is an extinct genus of dyrosaurid crocodyliform which existed during the Maastrichtian in western Africa. Fossils of the genus were found in the Dukamaje Formation of Nigeria, and some cranial material has possibly been found ...

'', which is known from Niger and Mali. Because ''Phosphatosaurus'' is only known from

Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of ...

localities, the close relationship with ''Sokotosuchus'' implies that there is a long

ghost lineage A ghost lineage is a hypothesized ancestor in a species lineage that has left no fossil evidence yet can be inferred to exist because of gaps in the fossil record or genomic evidence. The process of determining a ghost lineage relies on fossilized ...

extending back into the

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

that is not known in the fossil record.

Description

''Phosphatosaurus'' is a large dyrosaurid estimated at in length, with blunt teeth. The tip of the snout is spoon-shaped from a lateral expansion of the rostral portion of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

. The dentition is nonhomodont. Alveolar "couplets" are present in the lower jaw of ''Phosphatosaurus'' in which paired tooth sockets, or alveoli, are closer to one another than to the alveoli next to them. This is not seen in any other dyrosaurid but is seen in some other longirostrine (long snouted) crocodylomorphs such as the gavialoid '' Eosuchus''. It is possible that the

diastemata A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two tooth, teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molar (tooth), molars. More colloq ...

between the couplets served to receive larger

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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 ...

ry teeth.

Classification

''Phosphatosaurus'' was assigned in 1979 to the newly named subfamily Phosphatosaurinae by

Eric Buffetaut The given name Eric, Erich, Erikk, Erik, Erick, or Eirik is derived from the Old Norse name ''Eiríkr'' (or ''Eríkr'' in Old East Norse due to monophthongization). The first element, ''ei-'' may be derived from the older Proto-Norse ''* ai ...

, who considered the subfamily to be the clade formed by ''Phosphatosaurus'' and the closely related ''Sokotosaurus''. However, other authors of more recent studies have been tentative in considering the taxon valid because there is currently little knowledge of the anatomy of either genus.

Phylogenetics

''Phosphatosaurus'' is considered to be a

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

dyrosaurid, and is often positioned near the base of

phylogenetic trees A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

of dyrosaurids. An early phylogenetic analysis by Buffetaut (1978), not based on a cladistic data matrix, puts ''Phosphatosaurus'' at the base of the tree due to the presence of many primitive characters in the genus. Later phylogenetic analyses, such as the one by Jouve (2005), have also shown ''Phosphatosaurus'' to be a basal member of the family. In most analyses, ''Phosphatosaurus'' and ''Sokotosuchus'' form a clade. These two genera are more closely related to one another than to any other genus of dyrosaurid. More recent phylogenetic studies have considered '' Chenanisuchus'', a short-snouted dyrosairid named in 2005, to be even more basal than the clade containing ''Phosphatosaurus'' and ''Sokotosuchus''.

References

External links

''Phosphatosaurus''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Paleo ...

{{Taxonbar, from=Q2778681 Eocene crocodylomorphs Prehistoric pseudosuchian genera Prehistoric marine crocodylomorphs Paleogene reptiles of Africa Dyrosaurids Fossils of Mali