''Ichthyosaurus'' (derived from

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 ...

() meaning 'fish' and () meaning 'lizard') is a

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 ...

ichthyosaur Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fo ...

s from the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic� ...

(

Hettangian The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triass ...

- Pliensbachian) of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

(

Belgium Belgium, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

and

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

). Some specimens of the ichthyosaurid '' Protoichthyosaurus'' from

and

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

have been erroneously referred to this genus in the past. It is among the best known ichthyosaur genera, as it is the

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

of the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Ichthyosauria Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on foss ...

.Maisch MW, Matzke AT. 2000. The Ichthyosauria. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' 298: 1-159McGowan 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

History of discovery

''Ichthyosaurus'' was the first complete fossil to be discovered in the early 19th century by

Mary Anning Mary Anning (21 May 1799 – 9 March 1847) was an English fossil collector, fossil trade, dealer, and palaeontologist. She became known internationally for her discoveries in Jurassic marine fossil beds in the cliffs along the English Cha ...

; the holotype of ''I. communis'', no coll. number given,Judy A. Massare & Dean R. Lomax (2018). A taxonomic reassessment of ''Ichthyosaurus communis'' and ''I. intermedius'' and a revised diagnosis for the genus, ''Journal of Systematic Palaeontology'', 16:3, 263-277, DOI: 10.1080/14772019.2017.129111 was a fairly complete specimen discovered by Mary and Joseph Anning around 1814 in

Lyme Regis Lyme Regis ( ) is a town in west Dorset, England, west of Dorchester, Dorset, Dorchester and east of Exeter. Sometimes dubbed the "Pearl of Dorset", it lies by the English Channel at the Dorset–Devon border. It has noted fossils in cliffs and ...

but was reported as lost by McGowan (1974) in his review of the latipinnate

ichthyosaurs Ichthyosauria is an taxonomy (biology), order of large extinction, extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of ...

. The name ''Ichthyosaurus'' was first used by Charles König in 1818, but it was not used in a formal scientific description, with the earliest described ichthyosaur being ''Proteosaurus'' by James Everard Home in 1819 for a skeleton which is now attributed to '' Temnodontosaurus platyodon.''

Henry De la Beche Sir Henry Thomas De la Beche KCB, FRS (10 February 179613 April 1855) was an English geologist and palaeontologist, the first director of the Geological Survey of Great Britain, who helped pioneer early geological survey methods. He was the ...

and William Conybeare in 1821 considered ''Ichthyosaurus'' to have taxonomic priority over ''Proteosaurus'' and named the species ''I. communis'' based on BMNH 2149 (now NHMUK PV R1158), a now partially lost specimen now assigned to '' Temnodontosaurus'' that was discovered and collected between 1811 and 1812. Conybeare, W. D. (1822). Additional notices on the fossil genera ''Ichthyosaurus'' and '' Plesiosaurus''. ''Transactions of the Geological Society of London'', 1, 103–123. One specimen that Home had assigned to ''Proteosaurus'' was the first complete ichthyosaur skeleton known, but it was destroyed in WW2. Two casts were rediscovered in 2022, showing that the specimen belonged to ''Ichthyosaurus'', but of uncertain species. During the 19th century, almost all fossil ichthyosaurs were attributed to ''Ichthyosaurus'', resulting in the genus having over 50 species by 1900. These species were subsequently moved to separate genera or synonymised with other species. ''I. anningae'', described in 2015 from a

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 preserve ...

found in the early 1980s in

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

, England, was named after Anning. The fossil was acquired by Doncaster Museum and Art Gallery, where it was misidentified as a

plaster cast A plaster cast is a copy made in plaster of another 3-dimensional form. The original from which the cast is taken may be a sculpture, building, a face, a pregnant belly, a fossil or other remains such as fresh or fossilised footprints – ...

. In 2008, Dean Lomax, from the

University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The University of Manchester is c ...

, recognised it as genuine and worked with Judy Massare, of the

State University of New York The State University of New York (SUNY ) is a system of Public education, public colleges and universities in the New York (state), State of New York. It is one of the List of largest universities and university networks by enrollment, larges ...

, to establish it as a new species.

Description

''Ichthyosaurus'' was smaller than most of its relatives, with the largest specimen of ''I. somersetensis'' measuring up to in length. In comparison, other species were much smaller, with the ''I. communis'' reaching up to in length, ''I. larkini'' probably up to , ''I. anningae'' up to , ''I. breviceps'' up to , and ''I. conybeari'' up to . Many ''Ichthyosaurus'' fossils are well-preserved and fully articulated. Some fossils still had baby specimens inside them, indicating that ''Ichthyosaurus'' was

viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...

. Similar finds in the related '' Stenopterygius'' also show this.Böttcher R. 1990. Neue Erkenntnisse über die Fortpflanzungsbiologie der Ichthyosaurier. ''Stuttgarter Beiträge zur Naturkunde, Serie B (Geologie und Paläontologie)'' 164: 1-51Martill D.M. 1993. Soupy Substrates: A Medium for the Exceptional Preservation of Ichthyosaurs of the Posidonia Shale (Lower Jurassic) of Germany. ''Kaupia - Darmstädter Beiträge zur Naturgeschichte'' 2: 77-97 Jurassic ichthyosaurs had a fleshy

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

on their back as well as a large

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

. ''Icthyosaurus'' is distinguished from other ichthyosaurs by having a wide forefin with 5 or more digits with an anterior digital bifurcation, but the morphology of the

humerus The humerus (; : humeri) 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 (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

and

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

s are also distinct from that of other Lower Jurassic ichthyosaurs, as is the arrangement of the

dermal bone A dermal bone or investing bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton, including much of the skull, jaws, gill covers, shoulder girdle, fin rays ( lepidotrich ...

s, though the suture lines used to diagnose these are not always visible.

Classification

This

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

below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell.

Palaeobiology

''Ichthyosaurus'' is suggested to have been a ram feeder, with the morphology of its hyobranchial apparatus suggesting that it was incapable of

suction feeding Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...

, using the jaws and teeth alone to capture prey. ''Ichthyosaurus'' is thought to have been a pursuit predator that was capable of sustained swift swimming via thunniform locomotion. Stomach contents of ''Ichthyosaurus anningae'' indicate that it fed on

cephalopods A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

(likely belemnites) and fish. Like other ichthyosaurs, it likely relied on its sense of sight, possibly in combination with

olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

. It was initially believed that ''Ichthyosaurus'' laid eggs on land, but fossil evidence shows that in fact the females gave birth to live young. As such, they were well-adapted to life as fully pelagic organisms (i.e. they never came onto land). Three pregnant females are known, all of the subspecies ''I. somersetensis.'' Although none of the fetuses show a clear birth orientation it is likely they exited tail-first, a common feature in highly aquatic vertebrates.

Cultural significance

Joseph Victor von Scheffels poem ''Der Ichthyosaurus'' describes its extinction in humouristic verses. A monument on Hohentwiel cites it as well. The poem has been translated among others by

Charles Godfrey Leland Charles Godfrey Leland (August 15, 1824 – March 20, 1903) was an American humorist and folklorist, born in Philadelphia, Pennsylvania. He was educated at Princeton University and in Europe. Leland worked in journalism, travelled extensivel ...

, Gaudeamus! Humorous Poems by Joseph Viktor von Scheffel
Ebook-Nr. 35848 on gutenberg.org
/ref> Some of the stanzas:

References