Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from 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 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...

to the early

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

(

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age. Stra ...

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in ...

) worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Opthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the

Toarcian The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toar ...

. Currently, the oldest known ophthalmosaurids is ''

Mollesaurus ''Mollesaurus'' is an extinct genus of large ophthalmosaurine ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina. Etymology ''Mollesaurus'' was named by Marta S. Fernández in 1999 and the type species is ''Mollesauru ...

'' from the early Bajocian of Argentina, as well as indeterminate remains of the same age from Luxembourg and Canada. Named by George H. Baur, in 1887, the family contains the basal taxa like ''

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 ich ...

''. Appleby (1956) named the taxon Ophthalmosauria which was followed by some authors, but these two names are often treated as synonyms; Ophthalmosauridae has the priority over Ophthalmosauria. However, some researchers argue that Ophthalmosauridae should be restricted to the group typically referred to as

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 basal ...

, with classic

Platypterygiinae Platypterygiinae is an extinct subfamily of ophthalmosaurid thunnosaur ichthyosaurs from the early Late Jurassic to the early Late Cretaceous (Kimmeridgian - Cenomanian) of Asia, Australia, Europe, North America and South America. Currently, the ...

instead being referred to as Undorosauridae or Brachypterygiidae and Ophthalmosauria being used to unite these two groups.

Phylogeny

Ophthalmosauridae is a

node-based taxon Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a '' type'', which ...

defined by Ryosuke Motani (1999) as "the last common ancestor of '' Brachypterygius extremus'' and ''

Ophthalmosaurus icenicus ''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 ic ...

'' and all of its descendants". The definition he proposed for Ophthalmosauria was exactly the same. In this case both definitions are synonyms. The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell. Valentin Fischer, Edwige Masure, Maxim S. Arkhangelsky and

Pascal Godefroit Pascal Godefroit is a Belgian paleontologist. He discovered dinosaurs like '' Olorotitan'' in 2003. Godefroit is the director of earth and life sciences This list of life sciences comprises the branches of science that involve the scientific st ...

(2011) described a new genus of Ophthalmosauridae. They redefined it as "the last common ancestor of '' Arthropterygius chrisorum'' and ''Ophthalmosaurus icenicus'' and all of its descendants". In this case Ophthalmosauria isn't a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linn ...

of Ophthalmosauridae. The cladogram below follows Fischer ''et al.'' 2011. *Note: Placement of Ophthalmosauria by definition. Fischer ''et al.'' (2012) described another new genus of Ophthalmosauridae. They defined for the first time two subfamilies within the Ophthalmosauridae,

and

. ''Ophthalmosaurus'' and ''Platypterygius'' were found to be non-

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

. Ophthalmosauridae was characterized by a reduced extracondylar area, a plate-like dorsal trochanter, a

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...

with a facet for an anterior accessory element and the absence of notching on the paddle elements of the forefin. The cladogram below follows Fischer ''et al.'' 2012.

Since 2019

In 2019, two species of ''

Cryopterygius ''Cryopterygius'' (meaning 'frozen fin' in Greek) is an extinct genus of ophthalmosaurid ichthyosaur known from the uppermost Jurassic of Central Spitsbergen, Norway. The type species, ''Cryopterygius kristiansenae '', is known from a single, but ...

'' were assigned to the genus ''

Undorosaurus ''Undorosaurus'' is an extinct genus of ophthalmosaurid ichthyosaur known from western Russia, Svalbard, and Poland. It was a large ichthyosaur, with the type species measuring long and weighing . Discovery and naming ''Undorosaurus'' was named ...

'' by Zverkov & Efimov (2019). The authors considered the type species of the former genus, ''C. kristiansenae'', to be synonymous with ''Undorosaurus gorodischensis''; second species of ''Cryopterygius'', ''C. kielanae'', was tentatively maintained by the authors as a distinct species within the genus ''Undorosaurus''. The following cladogram shows a possible phylogenetic positions within Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).

References

{{Taxonbar, from=Q1936147 Middle Jurassic ichthyosaurs Late Jurassic ichthyosaurs Early Cretaceous ichthyosaurs Aalenian first appearances Turonian extinctions Ichthyosaurs Prehistoric reptile families