''Adamantinasuchus'' 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 extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
notosuchian
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 ...
from and named after the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', the ...
Adamantina Formation
The Adamantina Formation is a geological formation in the Bauru Basin of western São Paulo state, in southeastern Brazil.
Its strata date back to the Late Cretaceous epoch of the Cretaceous Period, during the Mesozoic Era. The formation is p ...
of
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
. 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 preserved ...
,
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 several ...
UFRJ-DG 107-R, collected by William Nava (hence the specific name ''navae''). The fossil consists of a partial
skull
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, the ...
, fragmentary limb bones and a few broken vertebrae, and was found 25 km SW of the town of Marilia, near a
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including contro ...
dam. ''Adamantinasuchus'' was approximately 60 cm 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 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, the ...
is crushed and the left side of the skull is altogether missing. The right
lower jaw is also preserved, along with many of the teeth. The skull is small, only 60 mm long and around 30 mm high, but the elliptical
orbits are very large, almost as long as the
rostrum, 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 mammal has b ...
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 septum
In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
Examples
Human anatomy
* Interatri ...
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, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened howeve ...
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, tear ...
; 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
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 t ...
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 beneath the large orbits. There are two large
foramina 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
The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, par ...
with a thin, short blade. The
prefrontal 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 co ...
(not preserved). The
lacrimal bone 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 Human skull, skull which, when joined at a fibrous joint, form the sides and roof of the Human skull, cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, an ...
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 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 streps ...
is almost vertical, with an oval cross-section. The
quadratojugal 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
The skull is a bone protective Cranial cavity, 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 ...
is elliptical, and does not excavate the
dentary noticeably, rather remaining between
angular and
surangular. 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.
In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example, ...
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
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines conn ...
, 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 (; ) 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 a round ...
are entirely missing from the holotype. The
radius
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
and
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 ...
are present but very poorly preserved; only the straight and cylindrical
diaphysis 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 and a few
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.
...
are also preserved, showing that they both have laterally expanded extremities but that other than this the phalanges are cylindrical.
Hindlimbs
The
femora are both partially preserved, and each femur is quite robust, with an expanded head. The
fourth trochanter 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 tr ...
crest, stopping just before a slight torsion in the diaphysis. The
tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
is poorly preserved, but its diaphysis is straight and cylindrical. The
fibula
The fibula 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. Its upper extremity is ...
'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 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
Quadrate may refer to:
* Quadrate bone
* Quadrate (heraldry)
* Quadrate lobe of liver
* Quadrate tubercle
The quadrate tubercle is a small tubercle found upon the upper part of the femur. It serves as a point of insertion of the quadratus femori ...
or the
articular bones to tell whether its jaw was capable of back-and-forth movements necessary for
chewing 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 food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
or a
scavenger
Scavengers are animals that consume 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 herbivorous feeding b ...
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 modified from O’Connor ''et al.'', 2010:
References
{{Taxonbar, from=Q1012855
Sphagesaurids
Terrestrial crocodylomorphs
Late Cretaceous crocodylomorphs of South America
Cretaceous Brazil
Fossils of Brazil
Fossil taxa described in 2006
Prehistoric pseudosuchian genera