''Anatosuchus'' ("duck crocodile", the name from the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''anas'' ("duck") and the

Greek Greek may refer to: Greece 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 ...

''souchos'' ("crocodile"), for the broad, duck-like snout) is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

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 nom ...

notosuchia Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group (see below); if Sebecosu ...

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 ...

discovered in Gadoufaoua,

Niger ) , official_languages = , languages_type = National languagespalaeontologists Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

led by the

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Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago and a National Geographic "explorer-in-residence" who has discovered several new dinosaur species on several continents, including at si ...

in 2003, in the ''

Journal of Vertebrate Paleontology The ''Journal of Vertebrate Paleontology'' is a bimonthly peer-reviewed scientific journal that was established in 1980 by Jiri Zidek (University of Oklahoma). It covers all aspects of vertebrate paleontology, including vertebrate origins, evolu ...

''. Its duck-like snout coincidentally makes it resemble a crocoduck, an imagined hybrid animal with the head of a crocodile and the body of a duck.

Discovery

The type species of ''Anatosuchus'' is ''A. minor'', in reference to its small body size. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

material (MNN GDF603), is a nearly complete skull with articulated lower jaws, belonging to a juvenile. It was discovered from the upper portion of the

Elrhaz Formation The Elrhaz Formation is a geological formation in Niger, central Africa. Its strata date back to the Early Cretaceous, about 125 to 112 million years ago. Dinosaur remains are among the fossils that have been recovered from the formation, alongsi ...

and lower portion of

Echkar Formation The Echkar Formation is a geological formation comprising sandstones and claystones in the Agadez Region of Niger, central Africa. Description Its strata date back to the Late Albian to Late Cretaceous ( Cenomanian stages, about 100-95 millio ...

, indicating an

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145& ...

(Late Aptian or Early Albian) age. Another specimen was found later (MNN GAD17) belonging to an adult, which had both the skull and much of the postcranial skeleton. Differences in the skull indicate that the unusual broad, flattened shape developed as the animal grew older.

Description

Skull and jaws

The

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

e are broad and flat, and form a line straight across the front of ''Anatosuchus'''s

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is ...

; each holds six recurved

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, ...

which point backwards into the mouth. The internarial processes of the premaxillae taper steeply up towards the projecting nasals; they begin as very wide, meaning that the external nares are dorsoventrally compressed. The premaxillae also form the floor of the narial passages, including a small flange which causes the nares to point up and out somewhat. This gives ''Anatosuchus'' a visible projecting nose on the front of its broad snout. The smooth narial fossae are located just behind these, and help to give the snout its broad flattened look. The

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. T ...

e are, by quite a long way, the largest and most expansive bones in the skull; each holds nineteen small recurved teeth. They have a narrow alveolar margin at the edge of their broad expanse, giving the head of ''Anatosuchus'' a rather rectangular appearance, and broad rami that extend above and below the antorbital opening. The upper of these rami form a long suture with the nasal, and then meet the prefrontal and lacrimal directly above the antorbital fenestra. The alveolar margin is vertically oriented, but runs anteroposteriorly rather than transversely as that of the premaxilla does. The maxilla is quite highly textured with pits and neurovascular canals, although far less than the nasal,

frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...

and

parietal bone The parietal bones () are two bones in the skull which, when joined at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is n ...

s in particular. The maxillae also form much 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 separ ...

, particularly at the anterior section of the palate; the

palatine bone In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ...

s form almost all the remainder. The median one-third (measured transversely from left to right) is arched dorsally, making the buccal cavity larger, whereas the two lateral thirds by this measure are horizontal. There is a slit-shaped foramen on each maxilla on the palate. The very posterior section is formed by the

pterygoid Pterygoid, from the Greek for 'winglike', may refer to: * Pterygoid bone, a bone of the palate of many vertebrates * Pterygoid processes of the sphenoid bone ** Lateral pterygoid plate ** Medial pterygoid plate * Lateral pterygoid muscle * Medi ...

and ectopterygoid; these also form the projecting posteroventral mandibular rami. The

choana The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodili ...

e are as far back as possible without contacting the suborbital fenestrae; there is a thin choanal septum between them where they emerge in the pterygoids. The nasal bones are quite long, and sutured together along their whole length; they begin just behind the internarial bar where the premaxillae meet, and end with two processes beneath the frontal bone. The lacrimal bones are L-shaped, with one ramus projecting forwards to meet the maxilla and one ramus projecting downwards to form part of the orbit. The lacrimal also has a small process for articulating with a

palpebral An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eye ...

, which projects out over the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

; although the palpebrals are disarticulated, they have fallen into orbits and so can be examined. Both anterior and posterior palpebrals were present above each orbit. 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 mo ...

s are shaped rather like a stylised capital I, wider at each of the ends, and effectively separate the nasals and lacrimals. The frontal bones are fused into one large bone, as are the parietals. The frontal-parietal suture is strong and highly interdigitating; although the frontals bear a medial crest, the parietal skull table is flat save for the deep pits across it. In the juvenile specimen, the interorbital width is less than the width across the skull table (between the two supratemporal fenestrae), but in the adult interorbital width is almost twice skull table width. The supratemporal fenestrae have distinctive corners in them, formed by projections of the frontal bone. This feature seems to have occurred as the animal grew older. The

postorbital bone The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some v ...

s are small and slightly curved; they possess articulations for the posterior palpebral. The

squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral c ...

s, right at the back and top of the skull, are triradiate, with slender anterior processes that contact the postorbitals and offset posterior processes that dip down to the

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

. The jugals have relatively long anterior rami, but not long enough to contact the antorbital fossae. There is a small oval fossa located beneath each orbit. The quadratojugals are partially fused to the quadrates close to their

condyle A condyle (;Entry "condyle"
in
The braincase is quite well preserved. The supraoccipitals are small and triangular, with a short vertical nuchal keel on the occiput; large flanges extend off this to each side. The paraoccipital processes, which contact both the squamosals and the quadrate condyles, are marked with a series of striations. The

occipital condyles The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra. The condyles are oval or reniform (kidney-shaped) in shape, and their anteri ...

are ventrally deflected and are formed almost entirely by the

basioccipital The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull this area is rough and uneven, and is joined t ...

s. Each side of the skull has three Eustachian foramina present - two on each basioccipital, one anterior and one posterior, and one between basisphenoid and otoccipital in the basal tuber. A pair of crests runs between the quadrate and the pterygoid on each lateral side of the braincase. The lower jaw is U-shaped, to match the upper jaw; the

dentary 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 bone ...

bears twenty-one teeth on each side. The dentary becomes broader transversely than dorsoventrally as it turns the corners of the U-shape, due to wide and vascularised dentary shelves and alveolar margins. The two dentary bones are interdigitating at their symphysis, meaning that the lower jaw is entirely inflexible. The dentary projects somewhat posteriorly, forming the edge of the external

mandibular fenestra The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, ...

. Both angular and

surangular The suprangular or surangular is a jaw bone found in most land vertebrates, except mammals. Usually in the back of the jaw, on the upper edge, it is connected to all other jaw bones: dentary, angular, splenial and articular. It is often a mu ...

extend to the top of the coronoid process, and the surangular forms much of the jaw articulation. The

articular The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as ancestral mammals. Anatomy In most vertebrates, the articular bone is connected to two oth ...

has a glenoid for the quadrate condyles; it is saddle-shaped, with no anterior or posterior lip, although there is a prominent attachment crest posteroventral to the jaw joint. The teeth have subconical crowns that curve in towards the centre of the mouth; all are fairly small and not very worn, indicating relatively little use. Most of the teeth have small

carinae ''Carinae'' was an area of ancient Rome. It was one of its most exclusive neighborhoods, where many of the senatorial class lived. Florus described the ''Carinae'' as the "''most celebrated part of the city''" (''celeberrima pars urbis''). Des ...

present on their surfaces. The dentary symphysis has no teeth present to either side of it for 11 mm, but forms a sharpish edge which may have been used with the premaxillary teeth 1-3 for cutting into prey. The largest teeth are found at the corners of the skull.

Postcranial skeleton and osteoderms

''Anatosuchus'' has a proatlas vertebra, eight

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

and probably 16

dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

, though only 15 are preserved. There are also two

sacral vertebrae The sacrum (plural: ''sacra'' or ''sacrums''), in human body, human anatomy, is a large, triangular bone at the base of the vertebral column, spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situ ...

. The dorsal vertebrae are amphicoelous, while the cervical centra lack hypapophyses. The proatlas is an inverted V-shaped piece of bone with a dorsal keel and is quite large relative to the

atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geogra ...

, which is made up of two separate neural arches. The axis has a low, subrectangular neural spine;

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

grow taller along the cervical vertebrae, with that of the third cervical vertebra being twice as tall as long and that of the seventh being almost five times as tall as long. The dorsal vertebrae are relatively long compared to their width, with length always more than half the width across the transverse processes. The

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

of the atlas and axis vertebrae are straight, whereas those of the other cervical vertebrae are short and triradiate. Dorsal ribs bend ventrally after they clear the osteoderm shield, forming a slight flange along the anterior margin; the ones closer to the posterior end have only one head. The

gastralia Gastralia (singular gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In thes ...

are quite poorly preserved between the girdles.

Osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s appear only to have been present on the dorsal surface; they were in pairs sutured together, each pair corresponding to one dorsal vertebra or up to three cervical ones. The articulation between rows is minimal, limited to a slight overlap between rows next to each other. The osteoderms are trapezoidal in shape and quite pitted; they articulate via a facet in the centre of the suture with their corresponding vertebra, the top of the neural spine of which fits into the facet. The

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

e are quite broad, but do not flare very widely at the distal end of the blade, which is tucked under the osteoderms. The

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

s are highly elongated. The humeri are long and have straight shafts; they are quite slender, with the width less than 10% of the length. The fossae on them where the olecranon processes would fit are strongly developed, suggesting that the legs could be held quite straight. The radii have strongly flared proximal ends, and are noticeably shorter than the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

e since these extend along the edges of the radiales. The ulnae are relatively curved. The radiales are strong, heavy bones, almost as wide as the radii, while the ulnares are poorly preserved. The manus are very large, and have strange fourth digits; each one has six

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

, rather than the normal four, although the total length is still only around 80% of that of the other digits. This is mainly due to their elongated

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

s. which have a narrow attachment groove along their length and are quite strongly arched. It is not known what benefit these specialised features conferred.

Classification

In the initial description of ''Anatosuchus'', it formed a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

with ''

Comahuesuchus ''Comahuesuchus'' is an extinct genus of notosuchian crocodylomorphs from the Santonian Bajo de la Carpa Formation of Argentina. It was described by palaeontologist José Bonaparte in 1991. The type species is ''C. brachybuccalis''.

'', within a less inclusive

Notosuchia Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group (see below); if Sebecosu ...

, also found to be monophyletic. However, further work proposed that ''Anatosuchus'' is not closely related to ''Comahuesuchus'', but instead is a member of

Uruguaysuchidae Uruguaysuchidae is a family of notosuchian crocodyliforms that lived in South America and Africa during the Cretaceous period. It includes the genera ''Araripesuchus'' and ''Uruguaysuchus ''Uruguaysuchus'' is an extinct genus of crocodylom ...

.Andrade MB, Bertini RJ, Pinheiro AEP. 2006. Observations on the palate and choanae structures in Mesoeucrocodylia (Archosauria, Crocodylomorpha): phylogenetic implications. ''Revista Brasileira de Paleontologia, Sociedade Brasileira de Paleontologia''. 9 (3): 323-332.

Palaeobiology

As the specific name indicates, ''A. minor'' was a very small crocodylomorph, with an adult body length estimated at around 70 centimeters. It had a very broad, duck-like snout. Despite its appearance it is considered to have a diet of small, aquatic creatures, and to get them it may have waded in water like a

heron The herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 72 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genera ''Botaurus'' and ''Ixobrychu ...

References

External links

Andrade et al. (2006)

Sereno et al. (2003)
{{Taxonbar, from=Q3278543 Early Cretaceous crocodylomorphs of Africa Uruguaysuchids Cretaceous animals of Africa Prehistoric pseudosuchian genera