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 ...
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
marine reptile
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including mari ...
s 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 ...
-
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 ...
boundary) of southern
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 ...
and 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 ...
.
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 ...
Bernhard Peyer
Bernhard Peyer (25 July 1885 – 23 February 1963) was a Swiss paleontologist and anatomist who served as a professor at the University of Zurich. A major contribution was on the evolution of vertebrate teeth.
Peyer was born in Schaffhausen, Swit ...
in 1955 based on a single nearly complete specimen T 4352 collected at Cava Tre Fontane from the Anisian-Ladinian boundary of
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 ...
, Switzerland. Peyer (1955) considered the species to be a very distinctive member of the order
Placodontia
Placodonts ("Tablet (pharmacy), tablet tooth, teeth") are an Extinction, extinct order (biology), order of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. They were part of Sauropterygia, the gro ...
, and thus erected Helveticosauridae as well as the superfamily Helveticosauroidea to contain it within Placodontia.
Nosotti and Rieppel (2003) described '' Eusaurosphargis'' from the equivalent beds at Cava di Besano of the
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 ...
(Anisian-Ladinian boundary) of Italy. Their
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 ...
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'', and thus it was assigned to Helveticosauridae. Based on the description in the literature available for '' Saurosphargis'' (whose
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 ...
is lost), they considered it to also fall in the Helveticosauridae
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 ...
. 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'', thus ''Saurosphargis'' was removed from Helveticosauridae, and placed in its own family
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 ...