''Megalophthalma'' (meaning "large eye" from the

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 ...

''megale'' large"and ''ophthalmós'' eye" is an extinct

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 ...

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...

amphibian belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Plagiosauridae Plagiosauridae is a clade of temnospondyls of the Middle to Late Triassic. Deposits of the group are most commonly found in non-marine aquatic depositional environments from central Europe and Greenland, but other remains have been found in Russi ...

. It is represented by the single

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 ...

''Megalophthalma ockerti'' from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

Erfurt Formation The Erfurt Formation, also known as the Lower Keuper (German: ''Untere Keuper'', ''Lettenkeuper'', ''Lettenkohle'' or ''Lettenkohlenkeuper''), is a stratigraphic formation of the Keuper group and the Germanic Trias supergroup. It was deposited ...

in southern Germany, which is itself based on a single partial skull and a fragment of the lower jaw. ''Megalophthalma'' is distinguished from other temnospondyls by its very large

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

or eye sockets, which occupy most of the skull and are bordered by thin struts of bone. Like those of most plagiosaurids, the skull flat, wide, and roughly triangular. The orbits are pentagon-shaped. The bones at the back of the skull (the

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lobes of the ...

) are highly modified and show similarities with those of the plagiosaurid '' Plagiosternum''. Both ''Megalophthalma'' and ''Plagiosternum'' lack prefrontal and

postfrontal bone The postfrontal is a paired cranial bone found in many tetrapods. It occupies an area of the skull roof between and behind the orbits (eye sockets), lateral to the frontal and parietal bones, and anterior to the postorbital bone. The postfrontal ...

s. In fact, ''Megalophthalma'' and ''Plagiosternum'' are thought to form their own

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

or evolutionary grouping within Plagiosauridae called Plagiosterninae. In overall form ''Megalophthalma'' and ''Plagiosternum'' are intermediate between the basal plagiosaurid '' Plagiosuchus'' (which more closely resembles non-plagiosaurid temnospondyls) and the derived '' Gerrothorax'' (which has an even more highly modified skull than plagiosternines).

The authors who originally described ''Megalophthalma'' hypothesized that it and other plagiosaurids had eyes that were much smaller than the orbits. Most reconstructions of plagiosaurids, particularly those of ''Gerrothorax'', show them having flattened eyes that fill up most of the orbits. However, a flattened eye is extremely unlikely because the lens would be too close to the

retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

to focus an image. ''Megalophthalma'' and other plagiosaurids more likely had spherical eyes like those of modern amphibians. The skull of ''Megalophthalma'' is too shallow for a spherical eye the width of the orbit to fit within it, so the eye was probably much smaller, perhaps less than in diameter. The eye was probably positioned near the front of the orbit as in modern small-eyed amphibians like cryptobranchid salamanders and pipid frogs. Another possibility, although far less likely, is that ''Megalophthalma'' and other plagiosaurids had eyes similar to those of the living deep-sea fish ''

Ipnops ''Ipnops'' is a genus of deep-sea fish in the family Ipnopidae, which also includes the better-known tripodfish (''Bathypterois grallator The tripod fish or tripod spiderfish, ''Bathypterois grallator'', is a deep-sea benthic fish in the fa ...

'', which are reduced to sheet-like retina that cover the upper surface of the skull and are only able to detect movement from shadows. Like ''Ipnops'', plagiosaurids are hypothesized to have rested on the bottom of bodies of water and ambushed prey that swam above them. However, ''Ipnops'' and plagiosaurids are very distantly related, making it unlikely that lensless eyes evolved in ''Megalophthalma''.

References

{{Taxonbar, from=Q16985278 Triassic temnospondyls Triassic temnospondyls of Europe Plagiosauridae