''Eusaurosphargis'' 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 a

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The earliest traditionally identified diapsids, the araeosc ...

reptile, known from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

(

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

and

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

age)

Besano Formation The Besano Formation is a geological formation in the southern Alps of northwestern Italy and southern Switzerland. This formation, a thin but fossiliferous succession of Dolomite (rock), dolomite and Shale, black shale, is famous for its preserva ...

of northern

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

and Prosanto Formation of south-eastern

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

. It contains a single species, ''Eusaurosphargis dalsassoi''. It was a small reptile, measuring long.

Discovery

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''Eusaurosphargis dalsassoi'' (BES SC 390) is a partial

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 ...

of a single individual found disarticulated but in close association. BES SC 390 was collected from an oil shale at Cava di Besano of the

(Grenzbitumenzone). These

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

al beds are equivalent to those at

Monte San Giorgio Monte San Giorgio is a Swiss mountain and UNESCO World Heritage Site near the border between Switzerland and Italy. It is part of the Lugano Prealps, overlooking Lake Lugano in the Swiss Canton of Ticino. Monte San Giorgio is a wooded mountai ...

, dating to the

boundary, probably to the latest Anisian at this location, of the early

, about 243

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

. Nicole Klein and Oliver J. Sichelschmidt (2014) described disarticulated remains they referred to ''Eusaurosphargis sp''. These remains were collected from the Dutch

Winterswijk Winterswijk (; also known as ''Winterswiek'' or ''Wenters'') is a Municipalities of the Netherlands, 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 ...

Quarry III of the Vossenveld Formation, dating to the late Anisian stage. A new, complete and almost entirely-articulated specimen was described in 2017 from Ducanfurgga, near

Davos Davos (, ; or ; ; Old ) is an Alpine resort town and municipality in the Prättigau/Davos Region in the canton of Graubünden, Switzerland. It has a permanent population of (). Davos is located on the river Landwasser, in the Rhaetian ...

, Canton Grisons (Graubünden) in Swiss Alps (PIMUZ A/III 4380). This specimen is of a juvenile and displays extensive

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 amph ...

armor and morphology that indicates that the animal was not aquatic as previously thought. Although a semi-aquatic lifestyle was not ruled out.

Etymology

''Eusaurosphargis'' was first described and named by Stefania Nosotti and Olivier Rieppel in

2003 2003 was designated by the United Nations as the International Year of Fresh water, Freshwater. In 2003, a Multi-National Force – Iraq, United States-led coalition 2003 invasion of Iraq, invaded Iraq, starting the Iraq War. Demographic ...

and the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

is ''Eusaurosphargis dalsassoi''. The generic name is derived from

Greek Greek may refer to: 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 of all kno ...

''eu'', meaning "true/well", ''sauros'', meaning "lizard", and ''sphargis'', the old genus name for the leatherback turtle, in reference to the many similarities ''Eusaurosphargis'' shares with '' Saurosphargis'', a taxon whose holotype was lost and was thus considered a mystery. Like the name of ''Saurosphargis'' itself, it also refers to ''Eusaurosphargis appear have''seemingly transitional traits between

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

s and other reptiles. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''dalsassoi'' honors the paleontologist

Cristiano Dal Sasso Cristiano Dal Sasso (born 12 September 1965) is an Italian paleontologist. He is known for having participated in the description of notable sauropsids such as the ichthyosaur ''Besanosaurus'' and the theropod dinosaurs ''Scipionyx'' and ''Saltrio ...

at the Milan Natural History Museum who was the first to realize the importance of BES SC 390.

Phylogeny

''Eusaurosphargis'' was first included in a

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

in its original description. Nosotti and Rieppel (2003) recovered it as 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 ...

of ''

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 complete h ...

'', and based on the description in the literature available for '' Saurosphargis'' (whose holotype is lost), they considered it to fall in the same

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 ...

. This group was found to be the sister-group of the clade that comprises thalattosauriforms and

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

ns. The anatomy of ''Saurosphargis'' was finally clarified by comparisons with the well-preserved specimens of '' Sinosaurosphargis'', and as a result ''Saurosphargis'' was no longer considered 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 ...

'', and thus could be included in a phylogenetic analysis. Li ''et al.'' (2011) found ''Saurosphargis'' and ''Sinosaurosphargis'' to form a clade separate from that of ''Eusaurosphargis'' and ''Helveticosaurus'', which they termed

Saurosphargidae Saurosphargidae is an extinct family of marine reptiles known from the Early Triassic (Olenekian stage) and early Middle Triassic (Anisian stage) of Europe and China. The type genus of the family is '' Saurosphargis'', named by Friedrich von Hu ...

. 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 ...

is simplified after the phylogenetic analysis of Li ''et al.'' (2014), which includes ''Eusaurosphargis'', ''Helveticosaurus'' and all known saurosphargid species. The removal / inclusion of

Ichthyopterygia Ichthyopterygia ("fish flippers") was a designation introduced by Richard Owen, 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 ...

was found to affect the

topology Topology (from the Greek language, Greek words , and ) is the branch of mathematics concerned with the properties of a Mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformat ...

the most - switching the positions of the ''Eusaurosphargis''+''Helveticosaurus'' and Thalattosauriformes clades, and altering the positions of several taxa within Eosauropterygia, which are not shown.

References

{{Taxonbar, from=Q3734995 Fossil taxa described in 2003 Middle Triassic reptiles of Europe Anisian life Prehistoric reptile genera