''Goronyosaurus'' is an extinct

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 marine lizard belonging to the

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...

family. Fossils of ''Goronyosaurus'' are exclusively known from the

Dukamaje Formation The Dukamaje Formation is a geological formation in Niger whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Dinosaur distribution ( ...

Niger ) , official_languages = , languages_type = National languagesNigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...

and also the Rima Formation of Nigeria, and are both

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 interval from ...

in age. The holotype was first described in 1930 as ''

Mosasaurus ''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages o ...

nigeriensis'', but subsequent remains revealed a highly unique set of adaptations that prompted the species to be reclassified as the only species of the new genus ''Goronyosaurus'' in 1972. These unique adaptations have made ''Goronyosaurus'' notoriously difficult to classify within the Mosasauridae and it is often left out of

phylogenetic analyses 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 ...

, although most authors agree that ''Goronyosaurus'' belonged to Mosasauridae. ''Goronyosaurus'' possesses unique teeth, which are unlike the teeth of any other mosasaur. Instead of the cutting teeth common among mosasaurs, ''Goronyosaurus'' has straight teeth with rounded apices adapted for smashing food.

Discovery and naming

The holotype of ''Goronyosaurus'', BMNH R14153, was found in northwestern

Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...

and was noted by

Franz von Nopcsa Franz may refer to: People * Franz (given name) * Franz (surname) Places * Franz (crater), a lunar crater * Franz, Ontario, a railway junction and unorganized town in Canada * Franz Lake, in the state of Washington, United States – see ...

in 1925, but he gave no species or genus name, and these remains were described more completely by Swinton ''et al.'' in 1930. The holotype material included only isolated

vertebrae 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 ...

, a single

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

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 tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

fragments and

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, tear ...

which Swinton ''et al.'' described and named as the new species ''

nigeriensis''. Later in the 1970s, a group of researchers from

Florence Florence ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilancio demografico an ...

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

, explored the

. Several localities where this

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

was exposed were searched. Additional material recovered included more vertebrae, a partial

humerus 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 roun ...

, a partial

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

, and a nearly complete

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 ...

lacking the rear of 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 ...

and parts of the mandible. Because of the material being found in the same horizon of the same region of Nigeria, and the similarities in size and anatomy, these new specimens were referred to ''M. nigeriensis'' by Augusto Azzarolli and his colleagues. A second, unnamed species, also from the

, was reported on by Lingham-Soliar & Theagarten in 1991.Lingham-Soliar & Theagarten. (1991). "Mosasaurs from the upper Cretaceous of Niger". ''Palaeontology''. 34: 653–670. It was found in the Mt. Igdaman locality in

Niger ) , official_languages = , languages_type = National languagesRima Formation in Nigeria. During the description of the new material, it was realized that there were significant differences from true ''Mosasaurus''. As such, Azzarolli ''et al.'' named the new genus ''Goronyosaurus'' for the remains. The generic name recognizes the Goronyo District of Nigeria, where the material was found. The skull from the newly discovered material, Geological Survey of Nigeria (abbreviated as N.G.) 1, was chosen to represent the

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

of the taxon. Referred specimens include all the previously discovered mosasaur remains, excluding three significantly larger vertebrae. Casts of all the material are present in the Museum of Geology and Palaeontology of the University of Florence.

Description

''Goronyosaurus'' is a small mosasaur, measuring up to long. Previously the body length had been estimated at , although Soliar (1988) identified that this length estimate was based on a false skull length to body length ratio (9.1:100). Based on the skull length to body length ratio of ''Tylosaurus'' (13.8:100), Soliar (1988) derived a body length estimate of from a long skull.

Skull

Most of the skull of ''Goronyosaurus'' is preserved in the material, although it is heavily crushed and distorted. Overall the skull is long and narrow compared to other mosasaurids, with an estimated complete length of and a width of only . Its skull length to skull width ratio (6.31:1) is most similar to '' Tylosaurus nepaeolicus'' (6.18:1) among other mosasaurs, followed by ''

Plesiotylosaurus ''Plesiotylosaurus'', meaning "near ''Tylosaurus''", is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Prognathodon''. The gen ...

'' (5.64:1) and '' Tylosaurus proriger'' (5.3:1). Goronyosaurus nigeriensis 1

The snout bones of 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 ...

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 ...

and

nasals In phonetics, a nasal, also called a nasal occlusive or nasal stop in contrast with an oral stop or nasalized consonant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. The vast majorit ...

are distorted and flattened laterally. The premaxilae bear strong teeth, with the anterior most tooth being placed directly behind the beginning of the snout. Large nerve

foramina In anatomy and osteology, a foramen (;Entry "foramen"
in

are placed close to the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

surface of the paired premaxilae. The maxillae bones are unusual for mosasaurids, as they bear teeth which extend posterior to the front of 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 a p ...

. It is uncertain exactly how many teeth there were in the maxilla due to breakage, but there is probably around eleven. The nasal bones which project between the external nares are very robust. They are approximately the same width for the entire length, and have a rugged surface, similar to tylosaurines. The nasal openings themselves are relatively small and posterior in ''Goronyosaurus''. Discussions of the

jugal bone 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. Anato ...

were presented significantly in Soliar (1988), due to the supposed morphology that was completely unlike any in known mosasaurs. Azzaroli ''et al.'' (1972) proposed that ''Goronyosaurus'' has an extremely long and tall jugal, which directly contrasts with the thin slender bones of other lepidosaurs. The functional implications proposed by Azzaroli were disregarded by Soliar in 1988, due to there being no precedent for such a mechanical adaptation. The identity of the jugals was doubted by Halstead & Middleton (1982), and Soliar (1988) instead proposed that the "jugal" of Azzaroli ''et al.'' was instead a

taphonomic Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...

combination of the jugal and

coronoid process of the mandible In human anatomy, the mandible's coronoid process (from Greek ''korōnē'', denoting something hooked) is a thin, triangular eminence, which is flattened from side to side and varies in shape and size. Its anterior border is convex and is continuou ...

. As such, the true jugal would be only around thick across a majority of its structure, similar in anatomy to ''

Liodon ''Liodon'' is a dubious genus of mosasaur from the Late Cretaceous, known from fragmentary fossils discovered in St James' Pit, England and possibly also the Ouled Abdoun Basin of Morocco. Though dubious and of uncertain phylogenetic affinities, ' ...

''. Much of the posterior skull has been crushed or broken away from the holotype. The strongly built parietals are very narrow, and are broken, although the articulation with the

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 e ...

was probably very intricate. The frontals are triangular, and articulate with the internarial bar strongly. The prefrontals are very crushed and distorted out of their original articulation, but were positioned like ''Tylosaurus'' in life. The prefrontals exclude the frontals from participating in the orbit. Goronyasaurus1DB

The

pterygoid bone The pterygoid is a paired bone forming part of the palate of many vertebrates, behind 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 th ...

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 sepa ...

is preserved, and bears teeth like in other mosasaurs. The two main processes of the pterygoid are broken, because of their long and slender shape, but it probable looked similar to related taxa. The process of the pterygoid that articulates with the ectopterygoid is similar to ''Tylosaurus'', being flattened vertically and strongly forked. Generally the occipital unit of ''Goronyosaurus'' is poorly preserved. The unit is narrow, and has tylosaurine features, as well as a unique morphology of the supraoccipital bone. Unlike on other taxa where the supraoccipital is flattened, in ''Goronyosaurus'' it has a distinct groove across its midline. The sides of the basisphenoid are unusually steep, and the vidian canal is uncovered, probably due to breakage of the thin sheet of bone that normally covers it. These features have been compared favourably to those in ''

Plioplatecarpus ''Plioplatecarpus'' is a genus of mosasaur lizard. Like all mosasaurs, it lived in the late Cretaceous period, about 73-68 million years ago. Description ''Plioplatecarpus'' was a medium-sized mosasaur, measuring long and weighing . The eyes ...

'', while the elongation and slenderness are similar more so to ''Tylosaurus''.

Dentition

Many isolated teeth found throughout Cretaceous Nigeria can be assigned to ''Goronyosaurus'', because of its unique tooth anatomy. Such isolated teeth display a similar polymorphic tapering, with

crowns A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...

that become blunter towards the back of the tooth row. These fit the morphology of ''Goronyosaurus'' to the exclusion of all other mosasaurs, except in the fact that such isolated teeth lack the fluted grooves of ''Goronyosaurus''. Teeth from the front of 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 tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

are slightly more robust than those more posterior, but still curve gently back. Centralized teeth have very blunt cutting edges, with enamel between 150–250 μm that has varying thickness while remaining shallow.

Axial skeleton

Although the first two

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 ...

are unknown, several others from along the neck have been preserved. The

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 ...

are robust and the zygapophyses are well developed, but the articulation of the

neural arch 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 ...

between vertebrae is not present. The processes that articulate with cervical

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- ...

become stronger towards the back of the neck. Multiple

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 ...

are known from along the back. Their

centra Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the stores are all owned by individual franchisees. The chain has three different ...

begin as cylindrical, but become flattened closer to the pelvis. No neural arches are preserved in any dorsal vertebrae. Zygapophyses are weakly present, unlike in the cervical vertebrae, but the inter-arch articulations are still absent. The transverse processes are directed slightly anteriorly and dorsally, and become less pronounced towards the pelvis.

Classification

Due to its unique characteristics and features, ''Goronyosaurus'' is notoriously difficult to classify and is left out of most phylogenetic analyses. ''Goronyosaurus'' was originally named within its own subfamily, Goronyosaurinae. However, this was based on the characters of the jugal now known to be incorrect. Soliar found that ''Goronyosaurus'' was within

Tylosaurinae The Tylosaurinae are a subfamily of mosasaurs,Williston, S. W. 1897. Range and distribution of the mosasaurs with remarks on synonymy. ''Kansas University Quarterly'' 4(4):177-185. a diverse group of Late Cretaceous marine squamates. Members of t ...

in 1988, based on a phylogeny of cranial-only characters.

Mosasaurinae The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except ...

was collapsed into a single unit, so relationships of ''Goronyosaurus'' within it were not tested. A placement within the Tylosaurinae is not necessarily correct however, as the genus was found as forming a clade with the genera ''

Prognathodon ''Prognathodon'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Clidastes''. ''Prognathodon'' has been recovered from depos ...

'', ''

'' and '' Ectenosaurus,'' which would place it within the

, in a comprehensive 2010 analysis of the

Anguimorpha The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to '' Varanus'' and '' Anguis'' than ''Scincus ''Scincus'' is a genus of skinks, lizards in the family Scincidae. Th ...

. The results from their analysis of morphology-only characters in extinct and

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

taxa is shown below, collapsed to only display Mosasauridae. The placements of Prognathodontini and

Mosasaurini Mosasaurini is a extinct tribe of mosasaurine mosasaurs who lived during the Late Cretaceous and whose fossils have been found in North America, South America, Europe, Africa and Oceania, with questionable occurrences in Asia. They are highly d ...

follow Russell (1967). Goronyosaurus nigeriensis abelov

The clade of ''Goronyosaurus'' and ''

'', and the other branch with Mosasaurini, were found to be grouped by two unique (

unambiguous Ambiguity is the type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement ...

) features, the lack of frontal bone bordering the nasal opening, and a

with a hooked process behind the

glenoid cavity The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from el, gléne, "socket", reflecting the shoulder joint's ball-and-socket form. It is a sha ...

. An earlier version of the 2010 analysis found a more typical phylogeny of mosasaurs, with ''Goronyosaurus'' closest to ''

Plotosaurus ''Plotosaurus'' ("swimmer lizard") is an extinct genus of mosasaur from the Upper Cretaceous (Maastrichtian) of Fresno County, California. Originally named ''Kolposaurus'' (meaning "bay lizard") by Berkeley paleontologist Charles Lewis Camp in 19 ...

'' in derived Mosasaurinae, and the clade

Plioplatecarpinae Plioplatecarpinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "plioplatecarpines" and have been recovered from all continents, though the occu ...

resolved, including '' Ectenosaurus'' and ''

'' (the latter typically a mosasaurine). A clade of ''Goronyosaurus'' and ''Plotosaurus'' was diagnosed by the presence of teeth to the very front of the premaxilla, extension of the tooth row below and behind the orbit, frontally contacting the maxillae, the unforked shape of the contact between skull roof and supratemporal arch bones, location of the vidian canal opening moved posteriorly, absence of zygapophyseal articulations in vertebrae, and complete separation of the deltoid anc pectoral muscle crests on the humerus.

Paleobiology

Diet

''Goronyosaurus'' has a unique tooth morphology among mosasaurs. Unlike a majority of mosasaurs, which have cutting teeth, ''Goronyosaurus'' has straight teeth with a rounded apex designed more for smashing food. This means that it may have competed with mosasaurs with cutting teeth, as well as large predatory

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

s and

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

References

{{Taxonbar, from=Q142060 Mosasaurids Fossil taxa described in 1972 Mosasaurs of Africa