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Mollesaurus; Temporal range: Middle Jurassic, 171.6–170 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Ophthalmosauridae
Subfamily:	†Ophthalmosaurinae
Genus:	†Mollesaurus; Fernández, 1999
Species:	†M. periallus
Binomial name
	†Mollesaurus periallus; Fernández, 1999
Synonyms
	Ophthalmosaurus periallus Maisch & Matzke, 2000;

Mollesaurus is an extinct genus of large ophthalmosaurine ichthyosaur known from northwestern Patagonia of Argentina.^[1]

Etymology

Mollesaurus was named by Marta S. Fernández in 1999 and the type species is Mollesaurus periallus. The generic name is derived from the name of the Los Molles Formation, where the holotype was collected, and sauros, Greek for "lizard". The specific name is derived from periallos, Greek for "before all others", in reference to the fact that it is the oldest ophthalmosaurid and one of the oldest thunnosaurs.^[1]

History of study

Mollesaurus is known from the holotype MOZ 2282 V, articulated partial skeleton which preserved partial skull and most of the vertebral column. It was collected in the Chacaico Sur locality from the Emileia giebeli ammonoid zone of the Los Molles Formation, Cuyo Group, dating to the early Bajocian stage of the Middle Jurassic, about 171.6-170 million years ago. Mollesaurus, along with Chacaicosaurus cayi which was found at the same locality, are the only diagnostic ichthyosaur specimens from the Aalenian-Bathonian interval. It was found near Zapala city of the Neuquén Basin.^[1]

Maisch and Matzke (2000) regarded Mollesaurus to be a species of Ophthalmosaurus.^[2] However, all recent cladistic analyses found that Mollesaurus is a valid genus of ophthalmosaurid.^[3]^[4] 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).^[3] 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.^[5]

Phylogeny

The following cladogram shows a possible phylogenetic position of Mollesaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).^[6]

Ophthalmosauria

Ophthalmosaurinae

Acamptonectes densus

Mollesaurus periallus

	Ophthalmosaurus natans

	Ophthalmosaurus icenicus

Gengasaurus nicosiai

Nannopterygius yasykovi

	Nannopterygius enthekiodon

	Nannopterygius saveljeviensis

	Nannopterygius borealis

Arthropterygius volgensis

Arthropterygius lundi

Arthropterygius thalassonotus

	Arthropterygius hoybergeti

	Arthropterygius chrisorum

Platypterygiinae

Brachypterygius extremus

Aegirosaurus leptospondylus

Muiscasaurus catheti

Leninia stellans

Sveltonectes insolitus

Athabascasaurus bitumineus

Platypterygius americanus

	Acuetzpalin carranzai

	Platypterygius sachicarum

	Caypullisaurus bonapartei

	Grendelius mordax

	Grendelius alekseevi

	Grendelius pseudoscythicus

	Grendelius zhuravlevi

Undorosaurus kielanae

	Undorosaurus nessovi

	Undorosaurus gorodischensis

Platypterygius australis

	Plutoniosaurus bedengensis

	Simbirskiasaurus birjukovi

	Platypterygius hercynicus

	Sisteronia seeleyi

	Platypterygius platydactylus

	Maiaspondylus lindoei

References

^ ^a ^b ^c Fernández, Marta S. (1999). "A new ichthyosaur from the Los Molles Formation (Early Bajocian), Neuquen Basin, Argentina". Journal of Paleontology. 73 (4): 677–681. Bibcode:1999JPal...73..677F. doi:10.1017/S0022336000032492. JSTOR 1306766. S2CID 130751356.
^ Michael W. Maisch & Andreas T. Matzke (2000). "The Ichthyosauria". Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie). 298: 1–159.
^ ^a ^b Patrick S. Druckenmiller & Erin E. Maxwell (2010). "A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada". Canadian Journal of Earth Sciences. 47 (8): 1037–1053. Bibcode:2010CaJES..47.1037D. doi:10.1139/E10-028.
^ Fischer, Valentin; Edwige Masure; Maxim S. Arkhangelsky & Pascal Godefroit (2011). "A new Barremian (Early Cretaceous) ichthyosaur from western Russia". Journal of Vertebrate Paleontology. 31 (5): 1010–1025. Bibcode:2011JVPal..31.1010F. doi:10.1080/02724634.2011.595464. hdl:2268/92828. S2CID 86036325.
^ Valentin Fischer; Michael W. Maisch; Darren Naish; Ralf Kosma; Jeff Liston; Ulrich Joger; Fritz J. Krüger; Judith Pardo Pérez; Jessica Tainsh & Robert M. Appleby (2012). "New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary". PLOS ONE. 7 (1): e29234. Bibcode:2012PLoSO...729234F. doi:10.1371/journal.pone.0029234. PMC 3250416. PMID 22235274.
^ Nikolay G. Zverkov & Megan L. Jacobs (2021) [2020]. "Revision of Nannopterygius (Ichthyosauria: Ophthalmosauridae): reappraisal of the 'inaccessible' holotype resolves a taxonomic tangle and reveals an obscure ophthalmosaurid lineage with a wide distribution". Zoological Journal of the Linnean Society. 191 (1): 228–275. doi:10.1093/zoolinnean/zlaa028.