''Sauroctonus'' ("lizard killer") 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 ...

of gorgonopsian

therapsids Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including li ...

who lived during the end of the

Middle Permian The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0. ...

in what is now

European Russia European Russia is the western and most populated part of the Russia, Russian Federation. It is geographically situated in Europe, as opposed to the country's sparsely populated and vastly larger eastern part, Siberia, which is situated in Asia ...

. The first

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 ...

s, discovered in

Tatarstan Tatarstan, officially the Republic of Tatarstan, sometimes also called Tataria, is a Republics of Russia, republic of Russia located in Eastern Europe. It is a part of the Volga Federal District; and its capital city, capital and largest city i ...

, were initially believed to belong to a new

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of the

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

n genus '' Arctognathus'' (named ''A. progressus'' in 1938). The

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

was designated as such until 1940, when it was assigned to the genus ''

Inostrancevia ''Inostrancevia'' is an extinction, extinct genus of large carnivorous therapsids which lived during the Late Permian in what is now European Russia and Southern Africa. The first-known fossils of this gorgonopsian were discovered in the context ...

'' by

Ivan Yefremov Ivan Antonovich (Antipovich) Yefremov, sometimes Efremov (; 23 April 1908 – 5 October 1972) was a Soviet paleontologist, science-fiction author and social thinker. He founded taphonomy, the study of fossilization patterns. Biography He ...

, before being definitively classified in a separate genus erected by

Alexey Bystrow Alexey Petrovich Bystrow, sometimes spelled Alexey Petrovich Bystrov and Aleksei Petrovich Bystrow, (; February 1, 1899 – August 29, 1959) was a Soviet paleontologist, anatomist, and histologist. Biography Born in the village of Tarasov ...

(in 1955). The most complete, known fossils of ''S. progressus'' include

cranial Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...

and postcranial elements, currently all recorded from Tatarstan. These elements show that the animal was a mid-sized gorgonopsian. Nearly complete remains listed from

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

have been attributed to a second species, ''S. parringtoni'', which would make this genus the only known gorgonopsian to have lived in both

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

and

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. However, it has been proven that this assimilation is mistaken, as it is mainly based on superficial resemblances, leaving the latter awaiting a more in-depth study to determine its relationships with other representatives of the group. Moreover, studies published post-2018 prove that ''S. progressus'' belongs to a grouping of Russian gorgonopsians, placed alongside the genera '' Suchogorgon'', '' Pravoslavlevia'' and ''Inostrancevia'', due to some shared cranial characteristics.

Research history

''S. progressus''

In 1938, the

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

paleontologist Alexandra Paulinovna Hartmann-Weinberg described some

remains of gorgonopsians having been discovered in

, in the present-day

. One of the fossils described in his paper is an incomplete but well-preserved

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 ...

, cataloged

PIN A pin is a device, typically pointed, used for fastening objects or fabrics together. Pins can have the following sorts of body: *a shaft of a rigid inflexible material meant to be inserted in a slot, groove, or hole (as with pivots, hinges, an ...

156/5. Hartmann-Weinberg considers this specimen to belong to a new

of the

'' Arctognathus'', designating it as ''Arctognathus progressus''. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''progressus'' is incorrectly named due to its supposed morphological closeness to

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s, which have a large number of progressive and more

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

-like features than other gorgonopsians. It quickly became apparent that the species is no more related to these same cynodonts than the other gorgonopsians, and in 1940, only two years after the publication of his article, one of Hartmann-Weinberg's employees, the reputed

reclassified the

as a new species of the Russian genus ''

'', renaming it as ''Inostrancevia progressus''. In 1955, after the analysis of the material,

proposed a separate genus for the species, which he named ''Sauroctonus'', and designates the specimen PIN 156/5 as the

lectotype 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 associated. In other words, a type is an example that serves to anchor or centralizes ...

of the taxon a proposal that will be quickly recognized later. The

genus name Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial spec ...

''Sauroctonus'' comes from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

σαῦρος (''saûros'', "lizard") and κτόνος / (''któnos'', "murderer" or "killer"), to literally give "lizard killer", in reference to its carnivorous diet. All known specimens are from the type locality where the first known skull was discovered. Among these fossils remains figures PIN 156/6, a specimen containing a crushed skull, some anterior part of the postcranial

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

and numerous isolated bones.

''S.? parringtoni''

All confirmed remains of ''Sauroctonus'' are only recorded in Russian territory and belong to the species ''S. progressus'', mainly represented by cranial material. In 1950, a relatively complete skeleton, discovered in the Usili Formation in

, cataloged GPIT/RE/7113, was described by the German paleontologist

Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...

as a representative of the species ''Scymnognathus parringtoni'', being named in honor of Francis Rex Parrington. In 1970, the skeleton was reidentified by the French paleontologist

Denise Sigogneau-Russell Denise Sigogneau-Russell (born ''c.'' 1941/42) is a French palaeontologist who specialises in mammals from the Mesozoic, particularly from France and the UK. She is currently based at the Muséum National d'Histoire Naturelle. Background Denise S ...

as a specimen of '' Aelurognathus'', being renamed ''Aelurognathus parringtoni''. It is from 2007 that the paleontologist Eva V. I. Gebauer reclassifies it as an African representative of the genus ''Sauroctonus'', a claim that she would confirm again in 2014. However, this affiliation is formally rejected in 2018, as new classifications based on cranial anatomical traits show that derived gorgonopsians are separated into two

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of Russian and African origin, leaving GPIT/RE/7113 as an ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' within the latter group. Other specimens have been attributed to this species, but no concrete affiliation has been worked out to date. For example, the well-preserved skull cataloged SAM-PK-K10034, mentioned briefly in a study concerning the nocturnal vision of non-mammalian

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

s, is referred to as ''S.

cf. The abbreviation cf. (short for either Latin or , both meaning 'compare') is generally used in writing to refer the reader to other material to make a comparison with the topic being discussed. However some sources offer differing or even contr ...

parringtoni''.

Description

The skull size of ''Sauroctonus'' is 22.5 cm long, indicating that it should be a medium-sized gorgonopsian. The skull is narrow posteriorly with small

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 ...

. The

temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines above, and the zygomatic arch below. Its floor is formed by the outer surfaces of four bones of the skull. The fossa is filled by the te ...

is elongated, the cranial arches are narrow, and the

dentary bone 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 moderately high. As in '' Viatkogorgon'', ''Sauroctonus'' also has high

palatal 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 ...

tuberosities that have many

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 ...

, the bones poorly sculpted, and

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s only slightly larger than the postcanine teeth. There are also 4 to 6 postcanine teeth on the

maxillary bone 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 maxillar ...

Classification

The

taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...

position of ''Sauroctonus'' has changed many times over the decades. In 1974, the Russian paleontologist Leonid Petrovich Tatarinov classified ''Sauroctonus'' within the family Gorgonopsidae, and in the subfamily Cynariopinae, alongside various African genera such as '' Cynariops'', '' Scylacognathus'' or '' Scylacops''. In a book published in 1989, Sigogneau-Russell leaves ''Sauroctonus'' as a gorgonopsian whose placement is undetermined. Mikhail Ivakhnenko still classifies ''Sauroctonus'' within the Gorgonopsidae in 2003, without assigning it to any subtaxon. In his 2007 thesis, Gebauer considers ''Sauroctonus'' to be a basal Gorgonopsidae. These repetitive classification changes have left ''Sauroctonus'' in an uncertain position among the gorgonopsians, with some seeing it as close to the African genera, while others consider it to belong to a lineage in its own right. It is from 2018 that paleontologists Christian Kammerer and Vladimir Masyutin definitively reclassify ''Sauroctonus'' in a group of Russian gorgonopsians, alongside the genera ''Inostrancevia'', '' Pravoslavlevia'' and '' Suchogorgon'', in particular for certain shared cranial characteristics, more precisely for close contact between 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 * Medial ...

and the

vomer The vomer (; ) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms ...

. This classification will be immediately followed by the next studies. The following

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 ...

showing the position of ''Sauroctonus'' within Gorgonopsia follows Kammerer and Rubidge, 2022:

Paleobiology

One of the most recognizable features among gorgonopsians is the presence of long, saber-like canines on the upper and lower

jaw The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth ...

. A study published in 2020 shows that several prehistoric predators with this comparable morphology would have had various possible prey-killing techniques. Among the gorgonopsians, ''Sauroctonus'' is found to have had a reduced jaw opening, unlike in the closely related ''Inostrancevia'', indicating that it would not have been as specialized in hunting as the other representatives of the group.

Paleoecology

''S. progressus'' is known from the locality of Sjomin Ravine, located in the republic of Tatarstan, in the northeast of European Russia. This fossil site, discovered in 1938 and dating from the end of the Middle Permian (

Capitanian In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian Epoch or Series. The Capitanian lasted between and million years ago. It was preceded by t ...

), is mainly represented by

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

s and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...

s with separated layers of fine

polymictic Polymictic lakes are holomictic lakes that are too shallow to develop thermal stratification; thus, their waters can mix from top to bottom throughout the ice-free period. Polymictic lakes can be divided into cold polymictic lakes (i.e., those th ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, which contains fossils of

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s, represented by isolated bones and fragmentary skeletons, as well as rare

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

remains. Apart from ''S. progressus'', the main tetrapods identified in the area include the

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

therapsid '' Idelesaurus'', the

reptiliomorph Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...

'' Chroniosuchus'', the

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...

Dvinosaurus ''Dvinosaurus'' is an extinct genus of amphibious Temnospondyli, temnospondyls localized to regions of western and central Russia during the Middle Permian, middle and late Permian, approximately 265-254 million years ago. Its discovery was first ...

'', and even

sauropsid Sauropsida ( Greek for "lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds (which, as theropod dino ...

s, including the

pareiasaur Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with osteoderms which covered large areas of the body. They first appeared in southern Pangea during the Middle Per ...

Scutosaurus ''Scutosaurus'' ("shield lizard") is an extinct genus of pareiasaur parareptiles. Its genus name refers to large plates of armor scattered across its body. It was a large anapsid reptile that, unlike most reptiles, held its legs underneath its b ...

'' and the

archosauriform Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemming from the last common anc ...

Eorasaurus ''Eorasaurus'' is an extinct genus of archosauromorph reptile known from the middle late Permian (late Capitanian or early Wuchiapingian age) of Tatarstan, European Russia. It contains a single species, ''Eorasaurus olsoni''. When originally des ...

''.

Notes

References

{{Taxonbar, from=Q132968 Gorgonopsia Prehistoric therapsid genera Lopingian synapsids of Africa Fossils of Tanzania Lopingian synapsids of Europe Fossils of Russia Lopingian genus first appearances Lopingian genus extinctions Fossil taxa described in 1955