Ophthalmosaurus

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Ophthalmosaurus
Temporal range: Middle Jurassic to Late Jurassic (Callovian to Oxfordian), 165–157  Ma
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Possible record during the Berriasian
OphthalmosaurusIcenius-NaturalHistoryMuseum-August23-08.jpg
Composite skeleton (NHMUK PV R3702, R3893, R4124) of Ophthalmosaurus icenicus at the Natural History Museum, London, with the forelimbs mounted backwards [1]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order:† Ichthyosauria
Family:† Ophthalmosauridae
Subfamily:† Ophthalmosaurinae
Genus:† Ophthalmosaurus
Seeley 1874
Type species
†Ophthalmosaurus icenicus
Species
Synonyms
  • AncanamuniaRusconi 1942
  • KhudiakoviaArkhangelsky 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 icenicus updated reconstruction.png
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). [2] [3] It had a robust, streamlined body that was nearly as wide as it was tall in frontal view. Like other derived ichthyosaurs Ophthalmosaurus had a powerful tail ending in a pronounced bi-lobed caudal fluke whose lower half was formed around the caudal spine whereas the upper lobe was made up entirely from soft tissue. The limbs of Ophthalmosaurus were short and rounded with the forelimbs being noticeably larger than the hind limbs. The combination of rather inflexible trunk, powerful caudal fluke and reduced limbs suggests a tail-propelled mode of locomotion with the limbs helping with steering, differing from the 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 Harry Seeley in 1874 with particular focus on the morphology of the clavicular bones. Over the years following its description a variety of genera have been sunk into Ophthalmosaurus. [5] Among them, Apatodontosaurus, Ancanamunia, Baptanodon , Mollesaurus , Paraophthalmosaurus , Undorosaurus and Yasykovia were all considered 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 Spilsby Sandstone dating to the early Berriasian stage of the Lower Cretaceous has been referred to cf. Ophthalmosaurus (i.e., either Ophthalmosaurus or a closely related species). [19]

Classification

O. icenicus in Tubingen Ophthalmosaurus icenicus Tubingen.JPG
O. icenicus in Tübingen

Within Ophthalmosauridae, Ophthalmosaurus was once considered most closely related to Aegirosaurus . [20] However, many recent 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]

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

Related Research Articles

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 species level, or represent distinct genera, even being argued as invalid. While fossils referred to Platypterygius have been found throughout different continents, the holotype specimen was found in Germany.

Plutoniosaurus is an extinct genus of ophthalmosaurid ichthyosaur of uncertain validity from the Early Cretaceous of the vicinity of Ulyanovsk, European Russia.

<i>Caypullisaurus</i> Extinct genus of reptiles

Caypullisaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur from the Late Jurassic to the Early Cretaceous of Argentina. Its holotype was collected from the Vaca Muerta Formation of Cerro Lotena, Neuquen, dating to the early Tithonian stage of the Late Jurassic, about 150 million years ago. Caypullisaurus was first named by Marta Fernández in 1997 and the type species is Caypullisaurus bonapartei. It was a large ichthyosaur, measuring about 7 m (23 ft) long.

<span class="mw-page-title-main">Ophthalmosauridae</span> Extinct family of reptiles

Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Ophthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the Toarcian. Currently, the oldest known ophthalmosaurids is Mollesaurus 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. 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, with classic Platypterygiinae instead being referred to as Undorosauridae or Brachypterygiidae and Ophthalmosauria being used to unite these two groups.

<i>Brachypterygius</i> Extinct genus of reptiles

Brachypterygius is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic of England. The type species was originally described and named as Ichthyosaurus extremus by Boulenger in 1904. Brachypterygius was named by Huene in 1922 for the width and shortness of the forepaddle, and the type species is therefore Brachypterygius extremus. The holotype of B. extremus was originally thought to be from the Lias Group of Bath, United Kingdom, but other specimens suggest it more likely came from the Kimmeridgian Kimmeridge Clay of Kimmeridge Bay, Dorset, UK.

<i>Undorosaurus</i> Extinct genus of reptiles

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 4–6 metres (13–20 ft) long.

Mollesaurus is an extinct genus of large ophthalmosaurine ophthalmosaurid ichthyosaur known from northwestern Patagonia of Argentina.

<i>Chacaicosaurus</i> Extinct genus of reptiles

Chacaicosaurus is a genus of neoichthyosaurian ichthyosaur known from the Middle Jurassic of Argentina. The single known specimen of this genus was excavated from the Los Molles Formation in Neuquén Province, and is housed at the Museo Olsacher under the specimen number MOZ 5803. This specimen consists of a skull, forelimb, some vertebrae, and some additional postcranial elements. The genus was named by Marta Fernández in 1994, and contains a single species, Chacaicosaurus cayi, making it the first named distinctive ichthyosaur from the Bajocian stage. It is a medium-sized ichthyosaur with a very long snout, which bears a ridge running along each side. The forelimbs of Chacaicosaurus are small and contain four main digits.

<i>Grendelius</i> Extinct genus of reptiles

Grendelius is a genus of platypterygiine ophthalmosaurid ichthyosaur from the Late Jurassic (Kimmeridgian-Tithonian) of the UK and European Russia. It was a medium-sized ichthyosaur measuring about 4 metres (13 ft) long.

<i>Baptanodon</i> Extinct genus of reptiles

Baptanodon is an ichthyosaur of the Late Jurassic period, named for its supposed lack of teeth. It had a graceful 3.5 m (11 ft) long dolphin-shaped body, and its jaws were well adapted for catching squid. Major fossil finds of this genus have been recorded in North America. The type species, Sauranodon natans, was originally included under Sauranodon in 1879, but this name was preoccupied.

<i>Maiaspondylus</i> Extinct genus of reptiles

Maiaspondylus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaurs known from Northwest Territories of Canada, the Cambridge Greensand of England and the Voronezh Region of Russia.

<i>Arthropterygius</i> Extinct genus of reptiles

Arthropterygius is a widespread genus of ophthalmosaurid ichthyosaur which existed in Canada, Norway, Russia, and Argentina from the late Jurassic period and possibly to the earliest Cretaceous.

<i>Athabascasaurus</i> Extinct genus of reptiles

Athabascasaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from Alberta, Canada.

Sveltonectes is an extinct genus of platypterygiine ophthalmosaurid ichthyosaurs known from Ul’yanovsk region, western Russia.

<i>Acamptonectes</i> Extinct genus of ophthalmosaurid ichthyosaur known from England and Germany

Acamptonectes is a genus of ophthalmosaurid ichthyosaurs, a type of dolphin-like marine reptiles, that lived during the Early Cretaceous around 130 million years ago. The first specimen, a partial adult skeleton, was discovered in Speeton, England, in 1958, but was not formally described until 2012 by Valentin Fischer and colleagues. They also recognised a partial subadult skeleton belonging to the genus from Cremlingen, Germany, and specimens from other localities in England. The genus contains the single species Acamptonectes densus; the generic name means "rigid swimmer" and the specific name means "compact" or "tightly packed".

<span class="mw-page-title-main">Platypterygiinae</span> Extinct subfamily of reptiles

Platypterygiinae is an extinct subfamily of ophthalmosaurid thunnosaur ichthyosaurs from the early Late Jurassic to the early Late Cretaceous of Asia, Australia, Europe, North America and South America. Currently, the oldest known platypterygiine is Brachypterygius. Platypterygiines were characterized by square tooth roots in cross-section, an extremely reduced extracondylar area of the basioccipital, prominent dorsal and ventral trochanters on humerus and ischiopubis lacking an obturator foramen.

<i>Pervushovisaurus</i> Extinct genus of reptiles

Pervushovisaurus is a genus of platypterygiine ichthyosaur from the Late Cretaceous (Cenomanian) of the Saratov region in western Russia, the La Penthiève Beds of France and the Cambridge area of the UK.

<span class="mw-page-title-main">Timeline of ichthyosaur research</span>

This timeline of ichthyosaur research is a chronological listing of events in the history of paleontology focused on the ichthyosauromorphs, a group of secondarily aquatic marine reptiles whose later members superficially resembled dolphins, sharks, or swordfish. Scientists have documented ichthyosaur fossils at least as far back as the late 17th century. At that time, a scholar named Edward Lhuyd published a book on British fossils that misattributed some ichthyosaur vertebrae to actual fishes; their true nature was not recognized until the 19th century. In 1811, a boy named Joseph Anning discovered the first ichthyosaur fossils that would come to be scientifically recognized as such. His sister Mary would later find the rest of its skeleton and would go on to become a respected fossil collector and paleontologist in her own right.

<i>Keilhauia</i> Extinct genus of reptiles

Keilhauia is a genus of ophthalmosaurid ichthyosaur, a type of dolphin-like, large-eyed marine reptile, from the Early Cretaceous shallow marine Slottsmøya Member of the Agardhfjellet Formation in Svalbard, Norway. The genus contains a single species, K. nui, known from a single specimen discovered in 2010 and described by Delsett et al. in 2017. In life, Keilhauia probably measured approximately 4 metres (13 ft) in length; it can be distinguished by other ophthalmosaurids by the wide top end of its ilium and the relatively short ischiopubis compared to the femur. Although it was placed in a basal position within the Ophthalmosauridae by phylogenetic analysis, this placement is probably incorrect.

References

  1. ↑ Moon, B. C.; Kirton, A. M. (2016). "Ichthyosaurs of the British Middle and Upper Jurassic. Part 1, Ophthalmosaurus". Monographs of the Palaeontographical Society. 170 (647): 1–84. doi:10.1080/02693445.2016.11963958. hdl: 1983/983f82bf-a391-4cbc-b313-1fc754017eef . S2CID   133288616.
  2. 1 2 3 Motani, Ryosuke; Rothschild, Bruce M.; Wahl, William (1999). "Large eyeballs in diving ichthyosaurs" (PDF). Nature. 402 (6763): 747. Bibcode:1999Natur.402..747M. doi:10.1038/45435. ISSN   1476-4687. S2CID   5432366. Archived from the original (PDF) on 18 January 2017.
  3. 1 2 3 Motani, Ryosuke (2005). "Evolution of fish-shaped reptiles (Reptilia: Ichthyopterygia) in their physical environments and constraints" (PDF). Annual Review of Earth and Planetary Sciences. 33: 395–420. Bibcode:2005AREPS..33..395M. doi:10.1146/annurev.earth.33.092203.122707. S2CID   54742104. Archived from the original (PDF) on 2019-07-07.
  4. ↑ Schwab, Ivan R (2002). "My, what big eyes you have . . ". The British Journal of Ophthalmology. 86 (2): 130. doi:10.1136/bjo.86.2.130. ISSN   0007-1161. PMC   1771016 . PMID   11855367.
  5. ↑ H.G. Seeley (1874). "On the Pectoral Arch and Fore Limbs of Ophthalmosaurus, a new Ichthyosaurian Genus from the Oxford Clay". Quarterly Journal of the Geological Society. 30 (1–4): 696–707. doi:10.1144/gsl.jgs.1874.030.01-04.64. S2CID   129725722.
  6. ↑ Maisch MW, Matzke AT. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)298: 1-159.
  7. 1 2 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.[ permanent dead link ]
  8. 1 2 3 4 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. doi:10.1080/02724634.2011.595464. hdl:2268/92828. S2CID   86036325.
  9. 1 2 3 4 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.
  10. 1 2 Storrs, Glenn W.; Vladimir M. Efimov; Maxim S. Arkhangelsky (2000). "Mesozoic marine reptiles of Russia and other former Soviet republics". In Benton, M.J.; Shishkin, M.A.; Unwin, D.M. (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. 140–210. 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. 1 2 Nikolay G. Zverkov & Megan L. Jacobs (2021) [First published 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.
  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. 1 2 Michael W. Maisch (2010). "Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art" (PDF). Palaeodiversity. 3: 151–214.
  15. ↑ Fischer, V.; A. Clement; M. Guiomar; P. Godefroit (2011). "The first definite record of a Valanginian ichthyosaur and its implications on the evolution of post-Liassic Ichthyosauria". Cretaceous Research. 32 (2): 155–163. doi:10.1016/j.cretres.2010.11.005. hdl:2268/79923. S2CID   45794618.
  16. ↑ Barrientos-Lara, Jair Israel; Alvarado-Ortega, Jesús (2021-11-01). "A new ophthalmosaurid (Ichthyosauria) from the Upper Kimmeridgian deposits of the La Casita Formation, near Gómez Farías, Coahuila, northern Mexico". Journal of South American Earth Sciences. 111: 103499. Bibcode:2021JSAES.11103499B. doi:10.1016/j.jsames.2021.103499. ISSN   0895-9811.
  17. ↑ Paparella, Ilaria; Maxwell, Erin E.; Cipriani, Angelo; Roncacè, Scilla; Caldwell, Michael W. (2017). "The first ophthalmosaurid ichthyosaur from the Upper Jurassic of the Umbrian-Marchean Apennines (Marche, Central Italy)". Geological Magazine. 154 (4): 837. Bibcode:2017GeoM..154..837P. doi:10.1017/S0016756816000455. S2CID   132955874.
  18. ↑ Maxwell, E.E. (2010). "Generic reassignment of an ichthyosaur from the Queen Elizabeth Islands, Northwest Territories, Canada". Journal of Vertebrate Paleontology. 30 (2): 403–415. doi:10.1080/02724631003617944. S2CID   85143039.
  19. ↑ Fischer, V.; Maisch, M. W.; Naish, D.; Kosma, R.; Liston, J.; Joger, U.; Krüger, F. J.; Pérez, J. P.; Tainsh, J.; Appleby, R. M.; Fenton, B. (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.
  20. ↑ Fernández M. 2007. Redescription and phylogenetic position of Caypullisaurus (Ichthyosauria: Ophthalmosauridae). Journal of Paleontology81 (2): 368-375.
  21. ↑ Arkhangel’sky, M. S., 1998, On the Ichthyosaurian Genus Platypterygius: Palaeontological Journal, v. 32, n. 6, p. 611-615.
  22. ↑ Fischer, V.; Bardet, N.; Benson, R.B.J.; Arkhangelsky, M.S.; Friedman, M. (2016). "Extinction of Fish-shaped Marine Reptiles Associated with Reduced Evolutionary Rates and Global Environmental Volatility". Nature Communications. 7: 10825. Bibcode:2016NatCo...710825F. doi:10.1038/ncomms10825. PMC   4786747 . PMID   26953824.
  23. ↑ Hudson, John D.; Martill, David M. (1991). "The Lower Oxford Clay: production and preservation of organic matter in the Callovian (Jurassic) of central England". Geological Society, London, Special Publications. 58 (1): 363–379. Bibcode:1991GSLSP..58..363H. doi:10.1144/GSL.SP.1991.058.01.23. S2CID   129388168.
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