''Mollesaurus'' is an extinct

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 large ophthalmosaurine ophthalmosaurid

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 ...

known from northwestern

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

Etymology

''Mollesaurus'' was named by Marta S. Fernández in

1999 File:1999 Events Collage.png, From left, clockwise: The funeral procession of King Hussein of Jordan in Amman; the 1999 İzmit earthquake kills over 17,000 people in Turkey; the Columbine High School massacre, one of the first major school s ...

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( ...

is ''Mollesaurus periallus''. The generic name is derived from the name of the

Los Molles Formation The Los Molles Formation is a geologic formation of Early to Middle Jurassic age, located at northern and central part of Neuquén Basin at Mendoza Shelf in Argentina. It is overlain by the Niyeu–Lajas Formation.McIlroy et al., 2005 Descript ...

, where the holotype was collected, and ''sauros'',

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 ...

for "lizard". The specific name is derived from ''periallos'',

for "before all others", in reference to the fact that it is the oldest ophthalmosaurid and one of the oldest thunnosaurs.

History of study

''Mollesaurus'' is known from 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 ...

MOZ 2282 V, articulated partial

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 ...

which preserved partial

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 ...

and most of the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

. It was collected in the Chacaico Sur locality from the ''Emileia giebeli'' ammonoid zone of the

Cuyo Group The Cuyo Archipelago or Cuyo Islands, is a group of about 45 islands lying to the northeast of the Philippine island of Palawan.''Traveler's Companion Philippines 1998'' p.214 Kirsten Ellis, Globe Pequot Press Globe Pequot, 1998 It lies south of ...

, dating to the early

Bajocian In the geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relatin ...

stage of the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations ...

, about 171.6-170

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

. ''Mollesaurus'', along with '' Chacaicosaurus cayi'' which was found at the same locality, are the only diagnostic ichthyosaur specimens from the

Aalenian The Aalenian () is a subdivision of the Middle Jurassic Epoch/ Series of the geologic timescale that extends from about 174.1 Ma to about 170.3 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian. Stratigraphic ...

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. St ...

interval. It was found near

Zapala Zapala is a city and touristic destination in the Patagonian province of Neuquén, Argentina with about 32,000 inhabitants according to the . The city is located at the geographic center of the province at the confluence of national and provincial ...

city of the

Neuquén Basin Neuquén Basin ( es, Cuenca Neuquina) is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The ba ...

. Maisch and Matzke (2000) regarded ''Mollesaurus'' to be a species of ''

Ophthalmosaurus ''Ophthalmosaurus'' (meaning "eye lizard" in Greek) is an ichthyosaur of the Jurassic period (165–150 million years ago). Possible remains from the Cretaceous, around 145 million years ago, are also known. It was a relatively medium-sized ichth ...

''. However, all recent

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analyses found that ''Mollesaurus'' is a valid genus of ophthalmosaurid. Patrick S. Druckenmiller and Erin E. Maxwell (2010) found it to be the basalmost member of the ophthalmosaurid lineage that included '' Brachypterygius'', '' Caypullisaurus'' and '' Platypterygius'' (but not ''Ophthalmosaurus''). Valentin Fischer, Michael W. Maisch,

Darren Naish Darren William Naish is a British vertebrate palaeontologist, author and science communicator. As a researcher, he is best known for his work describing and reevaluating dinosaurs and other Mesozoic reptiles, including '' Eotyrannus'', ''Xeno ...

, Ralf Kosma, Jeff Liston, Ulrich Joger, Fritz J. Krüger, Judith Pardo Pérez, Jessica Tainsh and Robert M. Appleby (2012) found it to be the basalmost member of

Ophthalmosaurinae Ophthalmosaurinae is an extinct subfamily of ophthalmosaurid thunnosaur ichthyosaurs from the Middle Jurassic to the late Early Cretaceous (Bajocian - Albian) of Europe, North America and South America. Currently, the oldest and the basalmost ...

Phylogeny

The following cladogram shows a possible phylogenetic position of ''Mollesaurus'' in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).

References

{{Taxonbar, from=Q6896406 Ophthalmosaurinae Middle Jurassic ichthyosaurs Bajocian life Middle Jurassic reptiles of South America Jurassic Argentina Fossils of Argentina Neuquén Basin Fossil taxa described in 1999 Ichthyosauromorph genera

Etymology

History of study

Phylogeny

See also

References