''Nannopterygius'' (meaning "small wing/flipper" in Greek) is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of ophthalmosaurid

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

that lived during the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic 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 rare, but geological formations co ...

to the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

(

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

Berriasian In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago) ...

stages).

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s are known from

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

, and

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

McGowan, C. & Motani, R. (2003). ''

Ichthyopterygia Ichthyopterygia ("fish flippers") was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitiv ...

''. ''In'' Sues, H.-D. Handbook of Paleoherpetology, vol. 8. Verlag Dr. Friedrich Pfeil, Munich, 175 pp., 19pls. and six species are currently assigned to the genus.

Description

''Nannopterygius'' was small for an ichthyosaur, measuring up to long at maximum. About of this was

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...

, including a deeply forked and probably

homocercal Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as see ...

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The head is long, with a typical long narrow

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

. The

eyes Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...

are large, hence its classification as an ophthalmosaurid, and have a bony

sclerotic ring Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are bel ...

inside the eye socket. There are at least 60 disc-shaped

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

, although owing to the condition of the fossil it is not possible to tell exactly how many there were, showing that ''Nannopterygius'' was flexible, agile and probably a fast swimmer. The

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

are long and curved, but do not quite join up. Most of the features are very similar to the close relative ''

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 ichth ...

.'' However, its paddles are much smaller, around for the forepaddles and only for the hindpaddles. This gave it a very

streamlined Streamlines, streaklines and pathlines are field lines in a fluid flow. They differ only when the flow changes with time, that is, when the flow is not steady. Considering a velocity vector field in three-dimensional space in the framework of ...

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

-shaped look, but would have made it quite difficult to generate much

lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...

or to turn quickly, making it an inefficient long-distance swimmer but speedy over short distances. It is therefore possible that it was an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey us ...

which plunged into shoals of fish quickly in the shallow seas where it lived.

Discovery and Classification

The first specimen was found in the Kimmeridgian

Kimmeridge Clay Formation The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for North ...

Kimmeridge Bay Kimmeridge Bay () is a bay on the Isle of Purbeck, a peninsula on the English Channel coast in Dorset, England, close to and southeast of the village of Kimmeridge, on the Smedmore Estate. The area is renowned for its fossils, with The Etche ...

, Dorset, UK and described by Hulke in 1871, who named it ''Ichthyosaurus enthekiodon''.Hulke, J. W. Note on an ''Ichthyosaurus'' (''I. enthekiodon'') from Kimmeridge Bay, Dorset. ''Quarterly Journal of the Geological Society'', 27, 440–441, pl. 17. This referred to its teeth being 'sheathed' in

cementum Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, a ...

and less likely to fall out than those of other ichthyosaurs. A year earlier, Hulke had described some remains from the same horizon and locality that he thought were ichthyosaurian, naming them ''Enthekiodon'' (no species given).Hulke, J. W. Note on some teeth associated with two fragments of a jaw from Kimmeridge Bay. ''Quarterly Journal of the Geological Society'', 26, 172–174. These are now lost, but Hulke considered them sufficiently similar to demote the name to species level. In 1922,

Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...

separated this species into the new genus ''Nannopterygius'', named for the small fore- and hindpaddles.Huene, F. F. von 1922. ''Die Ichthyosaurier des Lias und ihre Zusammenhänge''. Verlag von Gebrüder Borntraeger, Berlin, 114 pp., 22 pls. The first

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

is the most complete, but is flattened. All subsequent fossils are fragmentary. In 2020, several more species, including ''N. borealis'', and the species once contained in the genera ''Paraophthalmosaurus'' and ''Yasykovia'' were named based on remains found in

and

. The existence of two more species from

, ''N. mikhailovi'' and ''N. yakimenkae'', was confirmed by Yakupova & Akhmedenov (2022). The following cladogram shows a possible phylogenetic position of ''Nannopterygius'', which was found to be the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to '' Thalassodraco'', in Ophthalmosauria according to an analysis performed by Zverkov and Jacobs (2020).

Paleoecology

The type species is known from the Kimmeridge Clay Formation in Dorset, England. The Kimmeridge Clay hosts a wealth of marine fossils dating to the Kimmeridgian and Tithonian stages of the Late Jurassic, many of which are incredibly well preserved, however unfortunately very little has been published. At the time, Europe represented an island archipelago which was closer to the equator than it is today, surrounded by warm, tropical seas. The Kimmeridge Clay specifically represents an offshore marine environment, in which the seafloor was far enough below the surface not to be disturbed by storms. It was home to a great variety of marine life, including many cephalopods, fishes such as ''

Thrissops ''Thrissops'' (from el, θρῐ́ξ , 'hair' and el, ὄψις 'look') is an extinct genus of stem-teleost fish from the Jurassic and Cretaceous periods. Its fossils are known from the Solnhofen Limestone, as well as the Kimmeridge Clay. ''T ...

'' and the early ray '' Kimmerobatis'', and remains of occasional dinosaurs like ''

Dacentrurus ''Dacentrurus'' (meaning "tail full of points"), originally known as ''Omosaurus'', is a genus of stegosaurian dinosaur from the Late Jurassic to Early Cretaceous (154 - 140 mya) of Europe. Its type species, ''Omosaurus armatus'', was named in 18 ...

'' which had been washed out to sea. It is most famous for diversity of marine reptiles, such as the

metriorhynchid Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhynchidae ...

s ''

Metriorhynchus ''Metriorhynchus'' is an extinct genus of marine crocodyliform that lived in the oceans during the Late Jurassic. The type species, ''M. brevirostris'' was named in 1829 as a species of ''Steneosaurus'' before being named as a separate genus by ...

'' and ''

Plesiosuchus ''Plesiosuchus'' is an extinct genus of geosaurine metriorhynchid crocodyliform known from the Late Jurassic (late Kimmeridgian to early Tithonian stage) of Dorset, England and possibly also Spain. It contains a single species, ''Plesiosuchus ...

'', the

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

s ''

Colymbosaurus ''Colymbosaurus'' is a genus of cryptoclidid plesiosaur from the Late Jurassic (Callovian-Tithonian) of the UK and Svalbard, Norway. There are two currently recognized species, ''C. megadeirus'' and ''C. svalbardensis''. Both species are relati ...

'' and ''

Kimmerosaurus ''Kimmerosaurus'' ("lizard from Kimmeridge") is an extinct genus of plesiosaur from the family Cryptoclididae. ''Kimmerosaurus'' is most closely related to ''Tatenectes''. Discovery There are very few fossil remains of ''Kimmerosaurus'' known. ...

'', and the ichthyosaurs '' Grendelius'' and ''Thalassodraco''. The apex predators of the Kimmeridge ecosystem would have been the several species of the

pliosaurid Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous ( Rhaetian to Turonian stages) of Australia, Europe, North America and South America. The family is more inclusive than the archetypa ...

Pliosaurus ''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marine re ...

'' which have been recovered there, as well as large metriorhynchids like ''Plesiosuchus''. Additionally, the

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...

s ''

Cuspicephalus ''Cuspicephalus'' is an extinct genus of monofenestratan pterosaur known from Dorset in England. Its fossil remains date back to the Late Jurassic period. Discovery ''Cuspicephalus'' is known from the holotype MJML K1918, a partial skull ...

'' and ''

Rhamphorhynchus ''Rhamphorhynchus'' (, from Ancient Greek ''rhamphos'' meaning "beak" and ''rhynchus'' meaning "snout") is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such ...

'' are also known from the Kimmeridge Clay. The species ''N. yasykovi'' and ''N. saveljeviensis'' are known from the Volga region of Russia, which gives the Volgian stage its name. Though very little is known or published about the fossils of these localities, fossils of a number of marine animals have been recovered, including several species of the ichthyosaurs ''Arthropterygius'', ''Grendelius'', and ''Undorosaurus''. In addition, fossils of the pliosaurid ''Pliosaurus rossicus'' and indeterminate remains belonging to a metriorhynchid, as well as a high diversity of ammonites including the large-bodied taxon ''

Titanites ''Titanites'' is an extinct ammonite cephalopod genus within the family Dorsoplanitidae, that lived during the late Tithonian of the Late Jurassic. Description Species of the genus ''Titanites'' can reach large sizes, with a diameter of about ...

'', are also known from the Volgian-aged sediments of this region.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 Additionally, the species ''N. borealis'' is known from earliest Cretaceous sediments of the Slottsmøya Member of the

Agardhfjellet Formation The Agardhfjellet Formation is a Formation (geology), geologic formation in Svalbard, Norway. It preserves fossils dating back to the Oxfordian (stage), Oxfordian to Berriasian stages, spanning the Late Jurassic-Early Cretaceous boundary. The form ...

. The Slottsmøya Member consists of a mix of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

s and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

s and was deposited in a shallow water

methane seep A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the seep ...

environment. The seafloor, which was located about below the surface, seems to have been relatively dysoxic, or oxygen-poor, although it was periodically oxygenated by clastic sediments. Despite this, near the top of the member, various diverse assemblages of invertebrates associated with cold seeps have been discovered; these include

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s, lingulate brachiopods,

bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

, rhynchonellate brachiopods, tubeworms, belemnoids, tusk shells,

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomo ...

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s, and

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. Ther ...

, numbering 54 taxa in total. Though direct evidence from Slottsmøya is currently lacking, the high latitude of this site and relatively cool global climate of the Tithonian mean that sea ice was likely present at least in the winter. In addition to ''Nannopterygius'', the Slottsmøya Member presents a diverse assemblage of other marine reptiles, including the ichthyosaurs ''Undorosaurus gorodischensis'', several species belonging to the genus ''Arthropterygius'', and a partial skull attributed to ''Brachypterygius sp.'' The presence of these taxa indicates that there was significant faunal exchange across the seas of Northern Europe during this time period. Additionally, 21

ian specimens are also known from the site, including two belonging to the large pliosaur ''Pliosaurus funkei'', three to '' Colymbosaurus svalbardensis'', one to ''

Djupedalia engeri ''Djupedalia'' is an extinct genus of cryptoclidid plesiosauroid plesiosaur known from the uppermost Jurassic of central Spitsbergen, Norway. It is named after Øystein Djupedal, the former Minister of Education and Research who helped fund the ...

'', one to '' Ophthalmothule cryostea'', and one each to '' Spitrasaurus wensaasi'' and '' S. larseni''. Many of these specimens are preserved in three dimensions and partially in articulation; this is correlated with high abundance of organic elements in the sediments they were buried in.

References

{{Taxonbar, from=Q1028280 Fossil taxa described in 1922 Middle Jurassic ichthyosaurs Jurassic reptiles of Europe Late Jurassic ichthyosaurs Ichthyosaurs of Europe Jurassic United Kingdom Fossils of Great Britain Tithonian life Fossils of Svalbard Agardhfjellet Formation Early Cretaceous ichthyosaurs Berriasian life Cretaceous Norway Ophthalmosauridae Ichthyosauromorph genera

Description

Discovery and Classification

Paleoecology

See also

References