''Adamantinasuchus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

notosuchia Notosuchia is a clade of primarily Gondwanan mesoeucrocodylian Crocodylomorpha, crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogeny, phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ...

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. Extinct crocodylomorphs were considerably mor ...

from and named after the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Adamantina Formation The Adamantina Formation is a geological Formation (geology), formation in the Bauru Basin of western São Paulo (state), São Paulo state in southeastern Brazil. Its strata date back to the Late Cretaceous epoch of the Cretaceous, Cretaceous Per ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. It is known from only one

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

UFRJ-DG 107-R, collected by William Nava (hence the specific name ''navae''). The fossil consists of a partial

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

, fragmentary limb bones and a few broken vertebrae, and was found southwest of the town of Marilia, near a

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

dam. ''Adamantinasuchus'' was approximately long from nose to tail, and would have only weighed a few kilograms.

Features

Skull

''Adamantinasuchus'''s skull is quite well preserved; most of the right anterior part is present, along with some of the right posterior part, but the

cranium The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

is crushed and the left side of the skull is altogether missing. The right

lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

is also preserved, along with many of the teeth. The skull is small, only long and around high, but the elliptical

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

are very large, almost as long as the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

, which might suggest the animal was nocturnal.

Premaxilla and maxilla

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 mammals h ...

is covered in grooves and ridges, making it the most ornamented bone from the entire fossil. At the anterior end the premaxillae come together in a short triangular projection pointing ventrally and in another pointing dorsally. These would have been connected by a

cartilaginous Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

separating the two external nares, although this has not been preserved. The premaxilla bears two incisiform teeth and one

caniniform In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, eye teeth, vampire teeth, or fangs, are the relatively long, pointed tooth, teeth. In the context of the upper jaw, they are also known as ''fangs''. They can appear mo ...

tooth 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, tea ...

; this has led some to place it in the sphagesaurid group of crocodyliforms, since these also had differentiated teeth, although as the cladogram below suggests this is disputed. The maxillary dentition appears to bear out this theory as it bears seven molariform teeth of varying sizes. The

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

itself is mostly triangular, with a long anteroposterior base at the ventral side of which is a thin crest that covers the border of the dental alveoli. Towards the posterior end the maxilla is elongated, and it forms a long suture with the

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. Anatomy ...

beneath the large orbits. There are two large

foramina In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, arter ...

at the posterior end of the maxilla, and three small foramina at the anterior end, close to the premaxillary-maxillary border where another foramen is located.

Nasal, prefrontal, frontal and lacrimal

The

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 by their junction, form the bridge of the upper one third of the nose. Eac ...

is very incompletely preserved; what there is curves around ventrally, and is slightly sculptured towards the anterior end. The nasal projects back far enough to contact the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

with a thin, short blade. The

prefrontal Prefrontal may refer to: *Prefrontal bone, a skull bone in some tetrapods *Prefrontal cortex, a region of the brain of a mammal *Prefrontal scales The prefrontal scales on snakes and other reptiles are the scales adjacent and anterior to the fr ...

is triangular, and both left and right prefrontals are preserved, although the left prefrontal is only fragmentary. The prefrontal and frontal bones form a sinuous suture, although not a fully interdigitating one. The prefrontal's outer surface is very smooth, possibly due to contact with a

palpebral bone The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. It is also known as the adlacrimal or supraorbital, although the latter term may not be con ...

(not preserved). The

lacrimal bone The lacrimal bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...

is very small and has no distinguishing features, but contacts all of the nasal, prefrontal and frontal bones. The frontal is weakly convex in the middle and the anterior, but the posterior area of it is very flattened. Although the

parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

is not preserved, the interdigitating suture between parietal and frontal is still present, as is the crest across the bone here in the medial part.

Postorbital, jugal and quadratojugal

The

postorbital 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 ve ...

is fragmentary; from what is there, it is evident that it was squarish and posterolateral to the frontal bone rather than curving downwards. The jugal is thin, with a triangular transversal section and three branches. Its outer surface is smooth and there is a large foramen in the anterior section of the bone, close to the very thin crest in the medial portion that comes to a slender edge. The jugal is arched medially, curving out laterally away from the orbit, and is widest just behind the long suture with the maxilla, tapering to a bladelike portion at the posterior end. The

postorbital bar The postorbital bar (or postorbital bone) is a bony arched structure that connects the frontal bone of the skull to the zygomatic arch, which runs laterally around the eye socket. It is a trait that only occurs in mammalian taxa, such as most strep ...

is almost vertical, with an oval cross-section. The

quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...

is just behind the laterotemporal fenestra, and is slender and branched.

Lower jaw

The lower jaw as a whole is laterally compressed and curved anteroposteriorly, so that the narrow ventral surface is convex and the jaw forms a half-moon shape. The mandibular fenestra is elliptical, and does not excavate the

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

noticeably, rather remaining between angular and

surangular The surangular or suprangular 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 bone, angular, splenial and articular. It is o ...

. The dorsal end of the dentary extends posteriorly around part of the surangular; the outer surface of the dentary is entirely smooth. The surangular has a triangular cross-section and is tallest in the anterior portion. A lateral projection extends from it to partially cover the mandibular fenestra. At the posterior end the surangular is closer to cylindrical. The angular is medially excavated by the mandibular fenestra, and forms a vertical contact zone with the dentary; at the posterior end, it is vertically expanded upwards to form a narrow blade. The dentary carries three teeth on the preserved portion, which closely resemble those on the maxilla.

Teeth

The teeth are noticeably

heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...

in ''Adamantinasuchus'', with a mixture of incisiform, caniniform and molariform teeth. The first two teeth in the premaxilla are incisiform; they are small, pointed and

conical In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the ''apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines, ...

, and they bear small grooves. The third premaxillary tooth is caniniform and is much larger than the incisiform teeth, though it is a similar conical shape. Its tip points slightly backwards, and the crown bears small grooves. All seven maxillary teeth are molariform, though they vary greatly in size; the first three and the last two are much smaller than the two middle ones, only about half the size overall. All the maxillary teeth have one deep root, oval in cross-section, and there is a slight constriction between this and the crown of the teeth, which are flattened obliquely to produce a spatulate shape. The outer surfaces of the maxillary teeth are smooth and bear a few grooves, whereas the inner surfaces are covered in denticles that grow smaller towards the tip of each tooth. The two large central molariform teeth have a second set of denticles around the base of the inner surface of each tooth. Only three teeth are preserved on the dentary, one of which contacts a maxillary tooth's inner surface with its outer surface. The denticles on this tooth's outer surface perfectly match up with those of the inner surface of the maxillary tooth, forming a chisel contact surface for grinding or cutting food.

Forelimbs

The

humeri The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of ...

are entirely missing from the holotype. The

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

and

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

are present but very poorly preserved; only the straight and cylindrical

diaphysis The diaphysis (: diaphyses) is the main or midsection (shaft) of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue (fat). It is a middle tubular part composed of compact bone which surrounds a centr ...

of the radius is visible, and a small fraction of the ulna. This is, however, enough to show that it is bowed, typically for a crocodyliform. The radius's proximal extremity is wider than its distal extremity; the ulna's proximal portion is also wide, about three times the thickness of the diaphysis. The

metacarpals In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular skeleton, appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones (wrist, wris ...

and a few

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

are also preserved, showing that they both have laterally expanded extremities but that other than this the phalanges are cylindrical.

Hindlimbs

The

femora The femur (; : femurs or femora ), or thigh bone is the only bone in the thigh — the region of the lower limb between the hip and the knee. In many four-legged animals the femur is the upper bone of the hindleg. The top of the femur fits in ...

are both partially preserved, and each femur is quite robust, with an expanded head. The

fourth trochanter The fourth trochanter is a shared characteristic common to archosaurs. It is a protrusion on the posterior-medial side of the middle of the femur shaft that serves as a muscle attachment, mainly for the '' musculus caudofemoralis longus'', the m ...

forms a

rugose Rugose means "wrinkled". It may refer to: * Rugosa, an extinct order of coral, whose rugose shape earned it the name * Rugose, adjectival form of rugae Species with "rugose" in their names * ''Idiosoma nigrum'', more commonly, a black rugose tra ...

crest, stopping just before a slight torsion in the diaphysis. The

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

is poorly preserved, but its diaphysis is straight and cylindrical. The

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

's diaphysis is oval in cross-section and expands towards a flattened distal end; its proximal end is missing.

Diet

''Adamantinasuchuss teeth seem to be quite well adapted for an

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

diet, since they are heterodont and have well-developed molariform teeth - it might, like '' Chimaerasuchus,'' have included plants in its diet. There is insufficient preservation of the quadrate or 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 o ...

bones to tell whether its jaw was capable of back-and-forth movements necessary for

chewing Chewing or mastication is the process by which food is crushed and ground by the teeth. It is the first step in the process of digestion, allowing a greater surface area for digestive enzymes to break down the foods. During the mastication proc ...

plants, but the relative lack of wear on its molariform teeth suggest that it was probably only capable of dorsoventral biting motions, not chewing, and that it mainly ate softer food than plants. The teeth were also wider laterally than anteroposteriorly, which might have made back-and-forth chewing motions difficult or impossible; it is therefore probable that ''Adamantinasuchus'' was mainly

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

or a

scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...

of small corpses, since the incisiform and caniniform teeth would have been useful for seizing its prey or pulling strips of flesh off a carcass while the molariform teeth could have chewed it up.

Phylogeny

Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

modified from O’Connor ''et al.'', 2010:

References

{{Taxonbar, from=Q1012855 Sphagesauridae Terrestrial crocodylomorphs Late Cretaceous crocodylomorphs of South America Cretaceous Brazil Fossils of Brazil Fossil taxa described in 2006 Prehistoric pseudosuchian genera