''Mollesaurus'' 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 large ophthalmosaurine

ichthyosaur Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fo ...

known from northwestern

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

Etymology

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

1999 1999 was designated as the International Year of Older Persons. Events January * January 1 – The euro currency is established and the European Central Bank assumes its full powers. * January 3 – The Mars Polar Lander is launc ...

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 ''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 Argentina, officially the Argentine Republic, is a country in the s ...

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

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 ...

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 (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 ...

MOZ 2282 V, articulated 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 ...

which preserved partial

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and most of the

vertebral column The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmente ...

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

, Cuyo Group, dating to the early Bajocian stage of the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

, about 171.6-170

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 ...

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

Bathonian In the geologic timescale the Bathonian is an age (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...

interval. It was found near Zapala city of the Neuquén Basin. Maisch and Matzke (2000) regarded ''Mollesaurus'' to be a species of ''

Ophthalmosaurus ''Ophthalmosaurus'' (Greek ὀφθάλμος ''ophthalmos'' 'eye' and σαῦρος ''sauros'' 'lizard') is a genus of ichthyosaur known from the Middle-Late Jurassic. Possible remains from the earliest Cretaceous, around 145 million years ago, a ...

''. However, all recent

cladistic Cladistics ( ; from Ancient Greek 'branch') 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 ...

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 ''Platypterygius'' is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within ''Platypterygius'' likely are undiagnostic at the genus or ...

'' (but not ''Ophthalmosaurus''). Valentin Fischer, Michael W. Maisch, Darren Naish, 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.

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