''Dapedium'' (from , 'pavement') is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of primitive marine neopterygian

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

. The first-described finding was an example of ''D. politum'', found in the Lower Lias of Lyme Regis, on the Jurassic Coast of

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 ...

( Leach 1822). ''Dapedium'' lived in the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

to the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

period, from the late

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

to the early Aalenian.

Evolution

''Dapedium'' is one of the most diverse and abundant genera of ganoid fish from the early Jurassic of Europe. Its remains are known from many appropriately-aged lagerstätten throughout western Europe, with some records also known from eastern Europe. It appears to have been relatively rare during the Triassic, especially compared to other members of its family, but saw a large burst in diversification in the wake of the Triassic-Jurassic extinction event. It is thought that most Triassic dapediids had highly specialized feeding strategies or had less armor compared to the heavily-scaled, generalist ''Dapedium'', allowing it to survive the extinction event. These adaptations may have also enabled ''Dapedium'' to survive a second extinction event, the

Toarcian Oceanic Anoxic Event The Toarcian extinction event, also called the Pliensbachian-Toarcian extinction event, the Early Toarcian mass extinction, the Early Toarcian palaeoenvironmental crisis, or the Jenkyns Event, was an extinction event that occurred during the early ...

, although the abundance of ''Dapedium'' saw a dramatic decline after that, and it went extinct shortly afterwards. ''Dapedium'' was apparently a poor disperser, as despite its ecological success, there are no records of it outside Europe.

Species

The following species are known: * ''D. angulifer'' ( Agassiz, 1832) -

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� ...

(early

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 ...

) of England (

Blue Lias The Blue Lias is a formation (stratigraphy), geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest ...

) (=''Tetragonolepis traillii'' Agassiz, 1832) * ''D. ballei'' Maxwell & López-Arbarello, 2018 -

(early Aalenian) of Germany ( Opalinuston Formation) * ''D. caelatum'' Quenstedt, 1858 - Early Jurassic (early-middle

Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...

) of Germany ( Posidonia Shale) * ''D. colei'' Agassiz, 1835 - Early Jurassic (late Hettangian/early

Sinemurian In the geologic timescale, the Sinemurian is an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series. It spans the time between 199.5 ±0.3 annu ...

) of England (Blue Lias) * ''D. dorsalis'' (Agassiz, 1836) - Early Jurassic (Hettangian/ Pliensbachian) of England (" Lower Lias") * ''D. granulatum'' Agassiz, 1835 - late Hettangian/earliest late Sinemurian of England (Blue Lias/ Charmouth Mudstone) * ''D. magnevillei'' (Agassiz, 1836) - early Toarcian of France (" Upper Lias") * ''D. milloti'' Sauvage, 1891 - early Toarcian of France * ''D. noricum'' Tintori, 1983 -

(late

) of Italy ( Zorzino Limestone) * ''D. orbis'' Agassiz, 1836 - Hettangian/Pliensbachian of England ("Lower Lias") * ''D. pholidotum'' (Agassiz, 1832) - early-middle Toarcian of Germany (Posidonia Shale) * ''D. politum'' Leach, 1822 - early Sinemurian to earliest late Sinemurian of England (Blue Lias/Charmouth Mudstone) * ''D. punctatum'' Agassiz, 1835 - early Sinemurian to Pliensbachian of England (Blue Lias/Charmouth Mudstone) * ''D. stollorum'' Thies & Hauff, 2011 - early-middle Toarcian of Germany (Posidonia Shale) The complete fossil of an indeterminate ''Dapedium'' is known from the Toarcian of

Hungary Hungary is a landlocked country in Central Europe. Spanning much of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia and ...

, marking the only known specimen of this genus from eastern Europe. Records from India are thought to be erroneous.

Appearance

The various species of ''Dapedium'' ranged from long, and all had an oval to near-circular body. The skin was covered with thick, rhomboid, ganoid (enamel-like) scales. The smallest species so far found is ''D. noricum''. The skull was armoured with bony dermal plates, which were especially plentiful in the orbital region. These bones bore irregular tubercles. The small pectoral and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s, along with the extended

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

and

anal 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 o ...

s formed a functional unit with the tail. The tail was short and stout, providing the power for a sudden change in direction while the fish was swimming. The upper jaw of ''Dapedium'' was moveable and could protrude from the mouth, enabling a wider gape to capture larger prey.

Distribution

''Dapedium'' lived mostly in the Jurassic seas 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 ...

, a peripheral continental shelf sea of the Tethys Ocean. Notable finds have been made in Holzmaden,

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 ...

, in Temple Grafton,

Warwickshire Warwickshire (; abbreviated Warks) is a Ceremonial counties of England, ceremonial county in the West Midlands (region), West Midlands of England. It is bordered by Staffordshire and Leicestershire to the north, Northamptonshire to the east, Ox ...

and in Lyme Regis,

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.

Behaviour

The strong and pointed dentition suggests that ''Dapedium'' was durophagous, feeding on hard-shelled invertebrates, like mussels and sea urchins.

References

*''Detlev THIES & Annette HERZOG, New information on †Dapedium LEACH 1822 (Actinopterygii, †Semionotiformes), in Mesozoic Fishes 2 – Systematics and Fossil Record, G. Arratia & H.-P. Schultze (eds.): pp. 143-152, Verlag Dr. Friedrich Pfeil, München, Germany'' – {{Taxonbar, from=Q137782 Dapediidae Prehistoric ray-finned fish genera Triassic bony fish Jurassic bony fish Mesozoic fish of Europe Norian genus first appearances Sinemurian genera Hettangian genera Pliensbachian genera Toarcian genera Aalenian genera Middle Jurassic extinctions Jurassic Germany Fossils of Germany Posidonia Shale Fossils of England Fossils of Italy Fossils of France Fossils of Hungary Taxa named by William Elford Leach Fossil taxa described in 1822