''Silvestrosaurus'' is an extinct aquatic

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of lariosaurine

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 ...

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 bec ...

n known from the

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 ...

(

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 Trias ...

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

Monte San Giorgio Monte San Giorgio is a mountain and UNESCO World Heritage Site on 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 mountain, risin ...

, southern Switzerland. It contains a single species, ''Silvestrosaurus buzzii'', originally considered to be a species of the closely related ''

Lariosaurus ''Lariosaurus'' is an extinct genus of nothosaurid from the Middle Triassic (late Anisian to late Ladinian stage) of central and western Europe and China. With a length of just , it was one of the smallest known nothosaurs. First discovered at ...

''. The species was named by Tschanz in 1989, based solely on 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 seve ...

PIMUZ T/2804 comprising the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

, the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, and a dis-articulated partial

postcrania 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 s ...

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

. '' Cyamodus hildegardis'' tooth bearing elements were found in the stomach region of the specimen. The holotype was collected at Punkt 902 of Monte San Giorgio, from layer 97 of the Grenzbitumen zone, dating to the Anisian-Ladinian boundary of the Middle Triassic. Kuhn-Schnyner (1990) reassigned the species to its own genus, creating the combination ''S. buzzii''. The generic name honors a church near the collection locality of the holotype, dedicated to Saint Sylvester, a

Pope The pope ( la, papa, from el, πάππας, translit=pappas, 'father'), also known as supreme pontiff ( or ), Roman pontiff () or sovereign pontiff, is the bishop of Rome (or historically the patriarch of Rome), head of the worldwide Cathol ...

during the reign of

Constantine the Great Constantine I ( , ; la, Flavius Valerius Constantinus, ; ; 27 February 22 May 337), also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to convert to Christianity. Born in Naissus, Dacia Mediterran ...

, and 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 ...

''saurus'', meaning "lizard", a common suffix for genus names of extinct reptile. Rieppel (1998) reassigned ''S. buzzii'' back to its original combination ''

buzzii'', together with another lariosaurine genus ''

Ceresiosaurus ''Ceresiosaurus'' is an extinct aquatic genus of lariosaurine nothosaurid sauropterygian known from the Middle Triassic (Anisian-Ladinian boundary) of Monte San Giorgio, southern Switzerland and northern Italy. Ceresiosaurus, meaning "Lizard of ...

''. Rieppel (1998) found the two species to form a clade with ''Lariosaurus valceresii'', while the other species of ''Lariosaurus'' (incl. the type ''L. balsami'') formed a second clade, a

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 ...

to the first. In 2004, however, this synonymy was objected by Hänni who described and named a second species for ''

'', and by several other authors since.

Features

''Silvestrosaurus'' is very similar to its close relative ''Lariosaurus'' (see above) but there are enough differences for most people to assign them to different genera. The

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery * ...

has no contact with the

prefrontal Prefrontal may refer to: *Prefrontal bone, a skull bone in some tetrapods *Prefrontal cortex, a region of the brain of a mammal *Prefrontal scales The prefrontal scales on snakes and other reptiles are the scales connected to the frontals, toward ...

, separated by processes of the

frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...

and

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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 ...

, and many parts of the skull, such as the parietal and postfrontal bones, are much broader and flatter than in ''Lariosaurus.'' The

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

s do not meet in an anteromedial suture, unlike in ''Lariosaurus.'' In ''Silvestrosaurus'' the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

is slightly longer than the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

, but in ''Lariosaurus'' they are the same length or the radius is shorter. As the back half of the skeleton is missing, we cannot compare the number of

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...

e. Nor can we compare the hindfeet to see if ''Silvestrosaurus'' had paddles like ''Ceresiosaurus'' rather than individual toes like ''Lariosaurus.'' However, the front limbs definitely had paddles. ''Silvestrosaurus'' was only around long as an adult, making it relatively small for a nothosaur. Larger specimens would have belonged to individulas measuring long.

References

Fossil taxa described in 1989 Fossil taxa described in 1990 Nothosaurs Triassic sauropterygians Middle Triassic reptiles of Europe Anisian life Sauropterygian genera {{triassic-reptile-stub