Saurosphargidae 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 ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 ...

s known from the early

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

(

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic Ep ...

stage) of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones 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 ...

of the family is '' Saurosphargis volzi'', named by

Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...

in 1936 based on a single specimen collected from the lower Anisian Lower Muschelkalk of Gogolin,

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...

- a section of 12 incomplete back vertebrae with

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

s. The generic name of ''Saurosphargis'' is derived from

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 ...

''sauros'', "lizard", and ''sphargis'', the old genus name for the

leatherback turtle The leatherback sea turtle (''Dermochelys coriacea''), sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to and weights ...

, in reference to the dorsal

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

"body armor" and broadened ribs forming a closed chest rib basket, traits that are seemingly transitional between

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s and other reptiles. However, due to the only known specimen' destruction during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, many authors considered ''Saurosphargis'' to be a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''. Nevertheless, even based on surviving descriptions alone, many differences were noted even from its closest known relative at the time, '' Eusaurosphargis dalsassoi'' from the Anisian-Ladinian boundary of the southern

Alps The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, Sw ...

. Various hypotheses existed for the affinities of these species, and together with ''

Helveticosaurus ''Helveticosaurus'' is an extinct genus of diapsid marine reptile known from the Middle Triassic (Anisian-Ladinian boundary) of southern Switzerland. It contains a single species, ''Helveticosaurus zollingeri'', known from the nearly complet ...

'', they were originally thought to be

placodont Placodonts (" Tablet teeth") are an extinct order of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. They were part of Sauropterygia, the group that includes plesiosaurs. Placodonts were genera ...

s, but later studies suggested relatedness to other

sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...

ns and / or

ichthyopterygia Ichthyopterygia ("fish flippers") was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitiv ...

ns. It wasn't until nearly a century after the discovery of ''Saurosphargis'', that other specimens closely related to it were found in

. In 2011, Li ''et al.'' described and named three of these specimens, '' Sinosaurosphargis yunguiensis'', referring to this species being the Chinese version of ''Saurosphargis''. The specimens of ''Sinosaurosphargis'' were collected from Member II of the

Guanling Formation The Guanling Formation is a Middle Triassic (Anisian or Pelsonian in the regional chronostratigraphy) geologic formation in southwestern China. Description The formation encompasses two members. The first member is primarily calcareous mudston ...

, dating to the Pelsonian (mid-late

). Based on very detailed descriptions and figures of ''Saurosphargis'' in Huene (1936), and based on comparisons with the well-preserved ''Sinosauropshargis'', Li ''et al.'' (2011) resurrected ''Saurosphargis volzi'' as a valid species, and erected the family Saurosphargidae to contain the two. Furthermore, they reported the discovery of material referable to ''Saurosphargis'' from the Lower Muschelkalk of

Winterswijk Winterswijk (; also known as ''Winterswiek'' or ''Wenters'') is a municipality and a town in the eastern Netherlands. It has a population of and is situated in the Achterhoek, which lies in the easternmost part of the province of Gelderland in th ...

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

, that is under preparation. ''Saurosphargis'' and ''Sinosaurosphargis'' were included in a

phylogenetic analysis 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 ...

, and were recovered in a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

Saurosphargidae which was found to be the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

of Thalattosauriformes.

Sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...

was recovered as the sister taxon of their combined group, with a clade formed by ''Eusaurosphargis'' and ''Helveticosaurus'' in a position basal to it. In 2014, Li ''et al.'' described a second species of ''

Largocephalosaurus ''Largocephalosaurus'' is an extinct genus of basal saurosphargid, a marine reptile known from the Middle Triassic (Anisian age) Guanling Formation of Yunnan and Guizhou Provinces, southwestern China. It contains a type species, ''Largocephalo ...

'', that was initially interpreted as an

eosauropterygia Sauropterygia (" lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria bec ...

n due to the limited preparation of the

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 ...

of its type species ''L. polycarpon''. The second species ''L. qianensis'', known from three specimens, and the newly prepared portions of ''L. polycarpon''

postcranial Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

skeleton, revealed the same osteoderm "body armor" and broadened rib basket that are unique to saurosphargids. Thus, ''Largocephalosaurus'' was reinterpreted as a saurosphargid and a phylogenetic analysis recovered both species, forming a monophyletic ''Largocephalosaurus'', as basal to the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

formed by ''Saurosphargis'' and ''Sinosaurosphargis''. All four known specimens of ''Largocephalosaurus'' came from the Luoping Biota, from Member II of the Guanling Formation, that yielded ''Sinosaurosphargis'', alongside various invertebrates, fish, basal

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

s, ''

Atopodentatus ''Atopodentatus'' is an extinct genus of basal sauropterygian known from the early Middle Triassic (Pelsonian substage, Anisian to Ladinian stage) of Luoping County, Yunnan Province, southwestern China. It contains a single species, ''Atopodenta ...

'', and several species of

n, including both

pachypleurosaur left, 220px, '' Pachypleurosaurus'' Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles that vaguely resembled aquatic lizards, and were limited to the Triassic period. They were elongate animals, ranging in size from , w ...

s and

nothosaurid Nothosauridae are an extinct family of carnivorous aquatic sauropterygian reptiles from the Triassic time period of China, France, Germany, Israel, Italy, Netherlands, Russia, Switzerland, and northern Africa. Phylogeny The cladogram shown bel ...

Phylogeny

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 d ...

is simplified after Li ''et al.'' (2014)

, showing interrelationships of all known Saurosphargidae species, and the placement of the clade within

Sauria Sauria is the clade containing the most recent common ancestor of archosaurs (such as crocodilians, dinosaurs, etc.) and lepidosaurs ( lizards and kin), and all its descendants. Since most molecular phylogenies recover turtles as more closely re ...

. ''Saurosphargis'' was coded solely based on the holotype. The removal / inclusion of

Ichthyopterygia Ichthyopterygia ("fish flippers") was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitiv ...

was found to affect the

topology In mathematics, topology (from the Greek language, Greek words , and ) is concerned with the properties of a mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformations, such ...

the most - switching the positions of the ''Eusaurosphargis''+''Helveticosaurus'' and Thalattosauriformes clades, and altering the positions of several taxa within

Eosauropterygia Sauropterygia (" lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria bec ...

, which are not shown. The Saurosphargiformes are sometimes grouped together with Sauropterygia in a clade called Sauropterygomorpha.

References

{{Taxonbar, from=Q20984193 Middle Triassic reptiles Fossils of China Middle Triassic first appearances Middle Triassic extinctions Prehistoric reptile families