''Makhaira rossica'' 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 ...

and

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of a

marine reptile Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...

belonging to the family

Pliosauridae Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous ( Rhaetian to Turonian stages) of Australia, Europe, North America and South America. The family is more inclusive than the archetypa ...

. It lived during the early

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 th ...

period (

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the Va ...

epoch, about 130 million years ago), and its fossils have been found in

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

Description

Although fragmentary, the

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 ...

s of this animal have enough to differentiate it from other similar

plesiosaurs 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 ...

. ''Makhaira'' must have measured about long, and like its other relatives, must have had a compact body with four large paddle-like limbs. The skull was elongated, particularly in the rostral area, with several sharp teeth. The characteristics of these teeth are unique, they are triangular in cross view and had carinae or grooves with denticles at the edges, which possessed a height greater than its width. Denticles varied in length along the ridge and formed a kind of undulation in the edge of the tooth. The first tooth protruded from 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 ...

, while the mandibular

symphysis A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together ...

(the part of the jaw in which both rami meet) was very long and had more than ten

tooth socket Dental alveoli (singular ''alveolus'') are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament. The lay term for dental alveoli is tooth sockets. A joint that connects the roots of the t ...

s on each side. The face was long and straight, devoid of any lateral expansion. Makhaira rossica mandible

Classification

''Makhaira rossica'' was first described in 2015, based on fossil remains recovered near the

Volga River The Volga (; russian: Во́лга, a=Ru-Волга.ogg, p=ˈvoɫɡə) is the List of rivers of Europe#Rivers of Europe by length, longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Cas ...

in the

Ulyanovsk Oblast Ulyanovsk Oblast (russian: Ульяновская область, ''Ul’janovskaja oblast’'') is a federal subject of Russia (an oblast). It is located in the Volga Federal District. Its administrative center is the city of Ulyanovsk. Populatio ...

, in Russia. This reptile was evidently a representative of the pliosaurids, a group of plesiosaurs characterized by their short neck and large head. Unlike most other Cretaceous pliosaurids, ''Makhaira'' was not large; it seems to be close to the origin of the clade known as Brachaucheniinae, which includes ''

Brachauchenius ''Brachauchenius'' (meaning 'short neck') is an extinct genus of pliosaurid that lived in North America (United States) and Morocco during the Late Cretaceous. History The type species, ''Brachauchenius lucasi'', lived in the Western Inland S ...

'' and ''

Megacephalosaurus ''Megacephalosaurus'' (; "great-headed lizard") is an extinct genus of short-necked pliosaur that inhabited the Western Interior Seaway of North America about 94 to 93 million years ago during the Turonian stage of the Late Cretaceous, containin ...

'', which lived a few million years later and reached larger sizes.

Paleobiology

''Makhaira'' was probably a predator of relatively large animals, as suggested by the slightly curved and serrated teeth. The peculiar teeth of ''Makhaira'' suggests that it fed on different types of prey, compared to other Cretaceous pliosaurids. The characteristics of the teeth of ''Makhaira'' are also very similar to those of

metriorhynchid Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhynchidae ...

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 ...

s and raise the question of whether these were still present at the end of the Cretaceous, as suggested by the discovery of an isolated tooth from the

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 ago), a ...

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

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 ...

References

{{Taxonbar, from=Q25399481 Pliosaurids Cretaceous plesiosaurs Plesiosaurs of Europe Sauropterygian genera