''Rukwasuchus'' 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 ...

peirosaurid Peirosauridae is a Gondwanan family of mesoeucrocodylians that lived during the Cretaceous period. It was a clade of terrestrial crocodyliforms that evolved a rather dog-like form, and were terrestrial carnivores. It was phylogenetically define ...

mesoeucrocodylia Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day. Diagnosis It was long known that M ...

n known from the middle

Cretaceous 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 ...

Galula Formation of southwestern

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ...

. It contains a single species, ''Rukwasuchus yajabalijekundu''.

Discovery

''Rukwasuchus'' is known from its

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 ...

, RRBP 08630, a well-preserved rear part of the

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, t ...

including the cranial table,

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 ...

, and interorbital region lacking the rostrum, the front portion 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 s ...

, both

lacrimals The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

, jugals, and quadratojugals, as well as 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 ...

. RRBP 08630 was collected during 2008 at Namba 2 locality (also known as RRBP 2007-02), together with the titanosaurian '' Rukwatitan bisepultus'' which is exclusive to this locality. Material referred to ''Rukwasuchus'' includes four isolated

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, te ...

, which came from the neighboring localities RRBP 2007-01 yielding the 3 teeth RRBP 07351, 07369, 09362, and RRBP 2009-01 yielding the tooth RRBP 09367. All specimens came from approximately 25 km south of

Lake Rukwa Lake Rukwa is an endorheic lake located the Rukwa Valley of Rukwa Region, Songwe Region and Katavi Region in southwestern Tanzania. The lake is the third largest inland body of water in the country. Geography The alkaline Lake Rukwa lies mid ...

in the Galula Study Area, Rukwa Rift Basin of southwestern Tanzania, belonging to the Namba Member of the Galula Formation which dates to the late

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

or possibly early Cenomanian stage of the middle

, approximately 100 mya.

Etymology

''Rukwasuchus'' was named by Joseph J. W. Sertich and Patrick M. O’Connor in

2014 File:2014 Events Collage.png, From top left, clockwise: Stocking up supplies and personal protective equipment (PPE) for the Western African Ebola virus epidemic; Citizens examining the ruins after the Chibok schoolgirls kidnapping; Bundles of wat ...

and 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 ''Rukwasuchus yajabalijekundu''. The generic name refers to

and the Rukwa Rift Basin, located in southwestern Tanzania, where the holotype of ''Rukwasuchus'' and other vertebrates were collected by the Rukwa Rift Basin Project, and ''suchus'',

Latin Latin (, or , ) is a classical language belonging to the 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 the power ...

ized from 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'', an Egyptian crocodile god. The specific name ''yajabalijekundu'' is derived from the Swahili language meaning "of/from the red outcrop", in reference to the Red Sandstone Group deposits exposed at the basin.

Description

The skull of ''Rukwasuchus'' possesses several

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

which distinguished it from other

crocodyliform Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only ps ...

s. These include the presence of a mediolaterally narrow, elongate, and septate internal narial fenestra located anteriorly on 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 * Med ...

, the presence of a markedly depressed posterior border of the parietal that excludes the supraoccipital from the dorsal cranial table, and a ventrally directed descending process of the postorbital with a well-developed posteroventral process. The morphology of the skull and isolated teeth suggests close relations to the

Hamadasuchus rebouli ''Hamadasuchus'' is an extinct genus of sebecian crocodylomorph. Fossils have been found from the Kem Kem Formation outcropping in southeastern Morocco. These beds date back to the Albian and Cenomanian stages of the Late Cretaceous. It wa ...

'' from the middle Cretaceous

Kem Kem Beds The Kem Kem Group (commonly known as the Kem Kem beds) is a geological group in the Kem Kem region of eastern Morocco, whose strata date back to the Cenomanian stage of the Late Cretaceous. Its strata are subdivided into two geological formation ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria ...

. ''Rukwasuchus'' is the only known sub-

Sahara , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...

from Africa, thus representing the only link between middle Cretaceous southern vertebrate faunas and much more abundant and taxonomically diverse faunas from northern Africa.

Phylogeny

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of

Crocodyliformes Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only ps ...

supports a close relationship between ''Rukwasuchus'' and other African members of

Trematochampsidae Trematochampsidae is an extinct family of mesoeucrocodylian crocodylomorphs. Fossils are present from Madagascar, Morocco, Niger, Argentina, and Brazil (in the case of ''Caririsuchus'', where some specimens have been found in the Romualdo Membe ...

, e.g. ''Hamadasuchus'' and ''

Trematochampsa ''Trematochampsa'' is a dubious extinct genus of crocodyliform from the Late Cretaceous (Coniacian-Santonian age) In Beceten Formation of Niger. Taxonomy The type species, ''T. taqueti'', was described by Eric Buffetaut in 1974. A second s ...

'', that is positioned within a larger clade of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...

s. The following

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

is simplified after the analysis of Sertich & O’Connor (2014); the relationships within

Sebecosuchia Sebecosuchia is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group was long thought to have first appeared in the Late Cretaceous with the baurusuchids and become extinct in t ...

and advanced

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 Sebec ...

ns are not shown.

References

{{Taxonbar, from=Q16992356 Cretaceous crocodylomorphs of Africa Fossils of Tanzania Fossil taxa described in 2014 Prehistoric pseudosuchian genera