Ophthalmosaurus

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Ophthalmosaurus
Temporal range:
Ma
Possible record during the Berriasian
O. icenicus skeleton at the Natural History Museum, London, with the forelimbs mounted backwards[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: †Ichthyosauria
Family: †Ophthalmosauridae
Subfamily: †Ophthalmosaurinae
Genus: †Ophthalmosaurus
Seeley 1874
Type species
†Ophthalmosaurus icenicus
Species
Synonyms
  • Ancanamunia Rusconi 1942
  • Khudiakovia Arkhangelsky 1999

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, are also known. It was a relatively medium-sized ichthyosaur, measuring 4 m (13 ft) long and weighing 940 kg (2,070 lb).[2][3]
Named for its extremely large eyes, it had a jaw containing many small but robust teeth. Major fossil finds of this genus have been recorded in Europe with a second species possibly being found in North America.

Description

Life restoration
of O. icenicus

Ophthalmosaurus was a medium-sized ichthyosaur, growing to measure 4 m (13 ft) in length and weighing between 930–950 kg (2,050–2,090 lb).

anguilliform (eel-like) way more basal ichthyosaurs swam. The skull of Ophthalmosaurus was long with a slender, toothed rostrum and an enlarged posterior portion of the cranium. The dentition was relatively small with robust tooth crowns and the lateral area of the cranium was almost entirely occupied by the animal's massive eyes that gave the genus its name. The proportionally large eyes of Ophthalmosaurus measured 22–23 centimetres (8.7–9.1 in) in diameter at the outer margin of the bony sclerotic ring, while the sclerotic aperture itself measured 10 centimetres (3.9 in) in diameter.[2][4]

Discovery and species

Ophthalmosaurus was first described by

junior synonyms of Ophthalmosaurus in a study published by Maisch & Matzke in 2000.[6]

However, more recent

cladistic analyses have contested Maisch & Matzke's conclusion. Mollesaurus periallus from Argentina was considered a valid genus of ophthalmosaurid by Druckenmiller and Maxwell (2010),[7][8][9] Paraophthalmosaurus and Yasykovia were both recovered as distinct genera by Storrs et al., but were later sunk into Nannopterygius[10][11][12] while Undorosaurus's validity is now accepted by most authors, including Maisch (2010) who originally proposed the synonymy.[8][10][13][14][15] The two other Russian taxa might be also valid.[8][14] Likewise the Mexican ophthalmosaurid Jabalisaurus had also been referred to Ophthalmosaurus before being described as a distinct species and genus in 2021.[16]

Ophthalmosaurus natans was described as Sauranodon, then later renamed to Baptanodon by Marsh in 1880. However this decision was questioned not long afterwards with Baptanodon instead being considered an American species of Ophthalmosaurus. Recent analysis have recovered the species as closer to other ophthalmosaurines than to the Ophthalmosaurus type species,[7][9][17] suggesting that the previous name should be reinstated. Similarly, Ophthalmosaurus chrisorum, whose holotype has been recovered in Canada and described by Russell in 1993, was moved to its own genus Arthropterygius in 2010 by Maxwell.[18]

While primarily known from the Jurassic, material from the

Lower Cretaceous has been referred to cf. Ophthalmosaurus (i.e., either Ophthalmosaurus or a closely related species).[19]

Classification

O. icenicus in Tübingen

Within

cladistic analyses found Ophthalmosaurus to nest in a clade with Acamptonectes and Mollesaurus. Aegirosaurus was found more closely related to Platypterygius, and thus does not belong to the Ophthalmosaurinae.[8][9]

Phylogeny

The cladogram below follows Fischer et al. 2012.[9]

Thunnosauria 

The following cladogram shows a possible phylogenetic position of Ophthalmosaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).[12]

Ophthalmosauria
Ophthalmosaurinae
Platypterygiinae

Brachypterygius extremus

Aegirosaurus leptospondylus

Muiscasaurus catheti

Leninia stellans

Sveltonectes insolitus

Athabascasaurus bitumineus

Platypterygius americanus

Acuetzpalin carranzai

Platypterygius sachicarum

Caypullisaurus bonapartei

Platypterygius australis

Plutoniosaurus bedengensis

Simbirskiasaurus birjukovi

Platypterygius hercynicus

Sisteronia seeleyi

Platypterygius platydactylus

Maiaspondylus lindoei

Palaeobiology

Ophthalmosaurus icenicus possessed small teeth with robust tooth crowns and signs of slight wear differing notably from the robust teeth of later species of Platypterygius, known to have hunted large prey including turtles and birds, and the minute teeth of Baptanodon, interpreted to be a soft prey specialist. Fischer et al. (2016) conclude that this intermediary tooth morphology indicates that Ophthalmosaurus icenicus was most likely a generalist predator, feeding on a variety of smaller prey items.[22]

Ophthalmosaurus could likely dive for around 20 minutes. Assuming a conservative cruising speed of 1 metre per second (3.3 ft/s) (2 metres per second (6.6 ft/s) being more likely), Ophthalmosaurus could reach depths of 600 metres (2,000 ft) or more during a dive, reaching the mesopelagic zone.[3] However, while studies on the biomechanics of Ophthalmosaurus suggests that such feats could be physically achieved, studies on the environment of the Peterborough member of the Oxford Clay suggest that Ophthalmosaurus instead inhabited relatively shallow waters there, being determined to have been just 50 metres (160 ft) deep at a distance of 150 kilometres (93 mi) from the shore.[23]

See also

References

  1. S2CID 133288616
    .
  2. ^
    S2CID 5432366. Archived from the original
    (PDF) on 18 January 2017.
  3. ^
    S2CID 54742104. Archived from the original
    (PDF) on 2019-07-07.
  4. PMID 11855367
    .
  5. S2CID 129725722
    .
  6. ^ Maisch MW, Matzke AT. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie) 298: 1-159.
  7. ^
    doi:10.1139/E10-028.[permanent dead link
    ]
  8. ^
    S2CID 86036325
    .
  9. ^
    PMID 22235274
    .
  10. ^
    ISBN 9780521545822
    .
  11. ^ N. G. Zverkov, M. S. Arkhangelsky and I. M. Stenshin (2015) A review of Russian Upper Jurassic ichthyosaurs with an intermedium/humeral contact. Reassessing Grendelius McGowan, 1976. Proceedings of the Zoological Institute 318(4): 558-588
  12. ^
    doi:10.1093/zoolinnean/zlaa028
    .
  13. ^ McGowan C, Motani R. 2003. Ichthyopterygia. – In: Sues, H.-D. (ed.): Handbook of Paleoherpetology, Part 8, Verlag Dr. Friedrich Pfeil, 175 pp., 101 figs., 19 plts; München
  14. ^ a b Michael W. Maisch (2010). "Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art" (PDF). Palaeodiversity. 3: 151–214.
  15. S2CID 45794618
    .
  16. ISSN 0895-9811
    .
  17. S2CID 132955874
    .
  18. S2CID 85143039
    .
  19. PMID 22235274
    .
  20. ^ Fernández M. 2007. Redescription and phylogenetic position of Caypullisaurus (Ichthyosauria: Ophthalmosauridae). Journal of Paleontology 81 (2): 368-375.
  21. ^ Arkhangel’sky, M. S., 1998, On the Ichthyosaurian Genus Platypterygius: Palaeontological Journal, v. 32, n. 6, p. 611-615.
  22. PMID 26953824
    .
  23. S2CID 129388168
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Ophthalmosaurus&oldid=1216664084"