Laccognathus
Encyclopedia
Laccognathus is an extinct genus of amphibious
lobe-finned fish from Europe
and North America
. They existed from the Middle Devonian to the Late Devonian (around 397.5 to 360 mya). The name comes from Greek for 'pitted jaw'.
The skeleton
of Laccognathus was structured such that large areas of the skin were stretched out over solid plates of bone. This bone was composed of particularly dense fibers-- so dense that cutaneous respiration (exchange of oxygen
through the skin) was not a likely trait exhibited by Laccognathus. Rather, the dense ossification
s served to retain water inside the body as Laccognathus traveled on land between bodies of water.
Holoptychiidae
in the extinct order
Porolepiformes
. They are not direct ancestors of tetrapods like the clade
Tetrapodomorpha
, but instead belong to the clade Dipnomorpha. Their closest living descendants are the members of the subclass
Dipnoi (lungfishes).
Amphibious fish
Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits. These fish use a range of terrestrial locomotory modes, such as...
lobe-finned fish from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. They existed from the Middle Devonian to the Late Devonian (around 397.5 to 360 mya). The name comes from Greek for 'pitted jaw'.
Description
Species of Laccognathus were characterized by the presence of three large pits (fossae) on the external surface of the lower jaw which may have had sensory functions. It is the origin of the genus name, from Greek λάκκος ('pit') and γνάθος ('jaw'). Laccognathus grew to approximately 1–2 m (3.3–6.6 ft) in length. They had very short dorsoventrally flattened heads, less than one-fifth the length of the body. Like other sarcopterygians, their fins arise from pairs of fleshy lobes.The skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
of Laccognathus was structured such that large areas of the skin were stretched out over solid plates of bone. This bone was composed of particularly dense fibers-- so dense that cutaneous respiration (exchange of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
through the skin) was not a likely trait exhibited by Laccognathus. Rather, the dense ossification
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...
s served to retain water inside the body as Laccognathus traveled on land between bodies of water.
Taxonomy
Laccognathus are classified under the familyFamily (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Holoptychiidae
Holoptychiidae
Holoptychiidae is an extinct family of lobe-finned fishes which lived during the Devonian period. At least one genus, Laccognathus, is thought to have been amphibious....
in the extinct order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Porolepiformes
Porolepiformes
Porolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period . The group contains two families: Holoptychiidae and Porolepididae....
. They are not direct ancestors of tetrapods like the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Tetrapodomorpha
Tetrapodomorpha
Tetrapodomorpha is a clade of vertebrates, consisting of tetrapods and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish...
, but instead belong to the clade Dipnomorpha. Their closest living descendants are the members of the subclass
Subclass
Subclass may refer to:* Subclass , a taxonomic rank intermediate between class and superorder* Subclass , a class that is derived from another class or classes...
Dipnoi (lungfishes).
Species
The following are the species classified under Laccognathus. A fourth undescribed species recovered from the Middle Devonian of Latvia may exist.- †Laccognathus panderiLaccognathus panderiLaccognathus panderi is an extinct lobe-finned fish from eastern Europe. They existed from the Middle Devonian to the Late Devonian .L...
Gross, 1941
-
- Recovered from the Middle Devonian and Late Devonian formations of various parts of eastern EuropeEastern EuropeEastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
.- †Laccognathus grossiLaccognathus grossiLaccognathus grossi is an extinct lobe-finned fish from eastern Europe. They existed during the Middle Devonian. The species is named after Walter Gross, who collected the first Laccognathus fossils belonging to L. panderi.L...
Vorobyeva, 2006
- †Laccognathus grossi
- Recovered from the Middle Devonian Gauja FormationGauja FormationThe Gauja Formation is a Middle Devonian fossil locality in Estonia and Latvia. It is named after the Gauja River, where it is exposed along the banks....
of LatviaLatviaLatvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...
.- †Laccognathus embryiLaccognathus embryiLaccognathus embryi is an extinct species of porolepiform lobe-finned fish recovered from Ellesmere Island, Canada. It existed during the Frasnian age of the Late Devonian epoch .-Discovery:...
Downs et al., 2011
- †Laccognathus embryi
- Recovered from Late Devonian Fram FormationFram FormationThe Fram Formation is a Late Devonian sequence of rock strata on Ellesmere Island that came into prominence in 2006 with the discovery in its rocks of examples of the transitional fossil, Tiktaalik, a sarcopterygian or lobe-finned fish showing many tetrapod characteristics...
of Ellesmere IslandEllesmere IslandEllesmere Island is part of the Qikiqtaaluk Region of the Canadian territory of Nunavut. Lying within the Canadian Arctic Archipelago, it is considered part of the Queen Elizabeth Islands, with Cape Columbia being the most northerly point of land in Canada...
, CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, the same locality from which TiktaalikTiktaalikTiktaalik is a genus of extinct sarcopterygian from the late Devonian period, with many features akin to those of tetrapods . It is an example from several lines of ancient sarcopterygian "fish" developing adaptations to the oxygen-poor shallow-water habitats of its time, which led to the...
was found.
- Recovered from the Middle Devonian and Late Devonian formations of various parts of eastern Europe
See also
- HoloptychiusHoloptychiusHoloptychius is an extinct genus of porolepiform lobe-finned fish from the Devonian period. It is known from fossils worldwide.Holoptychius was streamlined predator about long, which fed on other bony fish. Its rounded scales and body form indicate that it could have swum quickly through the water...
- SarcopterygiiSarcopterygiiThe Sarcopterygii or lobe-finned fishes – sometimes considered synonymous with Crossopterygii constitute a clade of the bony fishes, though a strict classification would include the terrestrial vertebrates...
- List of sarcopterygians
- List of prehistoric bony fish