Onychodus
Encyclopedia
Onychodus is a genus
of prehistoric lobe-finned fish which lived during the Devonian
period (Eifelian - Famennian
stages, around 374 to 397 million years ago). It is one of the best known of the group of onychodontiform
fishes. Scattered fossil
bones of Onychodus were first discovered in 1857, in North America
, and described by John Strong Newberry
. Other species
were found in Australia
, England
, Norway
and Germany
showing that it had a widespread range.
Onychodus was about 2 to 3 meters in length and was a pelagic animal. Like other onychodontiformes, it had a pair of tooth spirals (parasymphysial tooth whorls) bearing tusk-like teeth.
The most well-preserved specimen
of Onychodus has been found at the Gogo Formation
of Western Australia
giving palaeontologists more information about the structure of the fish. Other species of Onychodus are known only from poor material based on isolated tusks, teeth and scales.
The most characteristic feature is a pair of retractable, laterally compressed tusk whorls at the front of the lower jaw. These were not attached to any other bone, but fit into a pair of deep cavities on the palate and were free to move. The lower jaw was connected with the upper jaw in a way that made the tusk whorl thrust out as a dagger when the head was raised. The upper jaw, containing 30 teeth which decrease in size posteriorly, is well preserved in many individuals. Juveniles have six tusks, while adults have three.
A relatively complete specimen of Onychodus from Western Australia shows that its length was 47 cm long, the head being 10 cm in length with tusks 1.2 cm long. This specimen is only about half the size of larger individuals, since skulls measuring 19 cm in length have been found. However, a single tusk 4 cm long was found, showing that this specimen belonged to an even larger individual. Evidence found of the body reveals that a cross section of this fish would have been oval in shape. On the sides of the body, Onychodus had a series of pores which provided a sensory system
that enabled the fish to locate prey and to position itself in narrow spaces. The tail fin is almost symmetrical around the vertebral column. It was rounded slightly and would have been very flexible with a broad sweep producing forward motion. A long fin extends posteriorly, along half the tail fin, forming the second dorsal fin. Evidence of the first dorsal fin is incomplete, but scientists believe that a fossil element found was its fin support. Ventrally, the large anal fin extends back beneath the anterior part of the tail fin. Scales that overlap anteriorly have been found, the smallest being only 5 mm across, and the largest 22 mm.
Onychodus is the type genus
of the order
Onychodontida
and the family
Onychodontidae
to which it belongs. The family name 'Onychodontidae' was created for Onychodus by the British
palaeontologist Arthur Smith Woodward
in 1891. The group of onychodontiformes, described in 1973 by the late Dr. Mahala Andrews
, was characterized by a highly kinetic skull and tusk-like teeth.
Suggestions by palaeontologist John A. Long
refer to a close phylogenetic relationship between Onychodus and the basal lobe-finned fish Psarolepis
from China
. It is generally acknowledged that Onychodus and Psarolepis are both basal bony fishes, because of the absence of major features that unite coelacanths, lungfishes and tetrapod
-like lobe-finned fishes. The position of Onychodus and Psarolepis in the cladogram
is outside the major clade of sarcopterygians (lobe-finned fishes), but at a position more derived than actinopterygians
(ray-finned fishes).
Onychodus fossils were first found in 1857 by Roy Wagner, Operations Manager for American Aggregates Corp., in Ohio
, USA, and were dated from Middle Devonian period. The remains made up the type specimen of Onychodus, later named Onychodus sigmoides, which was described and named by geologist
John Strong Newberry. One of his plates of the findings has been drawn by geologist Grove Karl Gilbert
. The name of the species Onychodus sigmoides comes from the word "sigmoid", meaning "S shaped", as were the teeth of Onychodus. All species were found having this type of teeth, but O. sigmoides was the first species described. The Onychodus specimen found by Wagner was given to Orton Geological Museum at the Ohio State University
.
The material collected of Onychodus sigmoides were a lower jaw and other single fragments, including parts of the skull, found at Ostrander
, Delaware County, Ohio
. All remains were found as isolated elements because the bones of Onychodus were loosely joined and dispersed quickly after the death of the fish. Studies show that Onychodus sigmoides was about 3 m in length and was the largest known bony fish of the Middle Devonian period.
Onychodus jaekeli was the second specimen described, clearly belonging to the genus Onychodus. Fossils have been found in Germany and described by palaeontologist Walter Gross
in 1965. Onychodus jaekeli has up to nine barbed tusks of equal length.
O. yassensis was found in New South Wales
at Canowindra site of Late Devonian, and described by palaeontologist David Lindley in 2002.
The new species found at Gogo Formation in Kimberley, Western Australia, Onychodus jandemarrai, is the best known species of the genus. It was described in 2006 based on extensive research by the late Dr. Mahala Andrews
, with colleagues Dr John Long, Dr Per Ahlberg, Prof. Ken Campbell and Dr Richard Barwick from material collected by the British Museum of Natural History, the Bureau of Mineral Resources and the Australian National University
in Canberra
. New material gathered by Dr. Long from the limestone in the Gogo formation, where he visited many times, contributed much information. Although much is known of this species, there are missing details such as the shape of the posterior end of the tail, the pectoral and pelvic fins and the first dorsal fin
. The name of species O. jandemarrai comes from the Aboriginal warrior Jandemarra who lived in that area.
Other less known species of Onychodus are: Onychodus anglicus (Woodward 1888) which was found in England, Onychodus arcticus (Woodward 1889) from Spitsbergen
, Norway, Onychodus hopkinsi and Onychodus ortoni (Newberry 1889) from North America, and Onychodus obliquidentatus (Jessen 1966), from Rhenish Massif, Germany.
Other distinctive traits are related to the tusk whorls on the lower jaw. Because they could rotate, this was a different method of jaw articulation which did not compare with primitive ray-finned fish. The lower jaw was entirely articulated with cartilage, without an intermediate structure between the opposite sides, allowing the separation of the bones when prey was struck. Moreover, the loose articulation caused lateral movement, making the tusk walls move out of alignment. The parts of the lower jaw would have rotated inwards upon closing in order for the tusk whorls to fit exactly into the hollow spaces in the upper jaw. It is suggested that a ligament attachment and retractor mechanism existed in a pit under the tusk whorl, a unique condition in vertebrates. The capacity of the teeth on the lower jaw to fit with the tooth rows in the upper jaw, upon closure, kept the tusk whorls in place.
Through studies scientists believe that Onychodus was an ambush predator. John A. Long has suggested that Onychodus probably hid in the Devonian reefs, lunging at its prey as it swam by. A fossil specimen of Onychodus from Western Australia was found with a placoderm fish half its length logged in its throat. This interesting find was described and illustrated by Dr. John A. Long. The pectoral fins were strong enough for the animal to "walk" around the sea floor in search of a hiding place between coral colonies. The posterior dorsal fin was quite powerful, providing quick speed for capturing prey.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of prehistoric lobe-finned fish which lived during the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period (Eifelian - Famennian
Famennian
The Famennian is one of two faunal stages in the Late Devonian epoch. It lasted from 374.5 ± 2.6 million years ago to 359.2 ± 2.5 million years ago. It was preceded by the Frasnian stage and followed by the Tournaisian stage and is named after Famenne, a natural region in southern Belgium.It was...
stages, around 374 to 397 million years ago). It is one of the best known of the group of onychodontiform
Onychodontida
Onychodontida is a group of prehistoric fish. This order was it represents a small group of sarcopterygian fishes that lived between Late Silurian to Late Devonian period...
fishes. Scattered fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
bones of Onychodus were first discovered in 1857, in 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...
, and described by John Strong Newberry
John Strong Newberry
John Strong Newberry was a American geologist, physician, explorer, author, and a member of the Megatherium Club at the Smithsonian Institution in Washington, D.C....
. Other species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
were found in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
showing that it had a widespread range.
Onychodus was about 2 to 3 meters in length and was a pelagic animal. Like other onychodontiformes, it had a pair of tooth spirals (parasymphysial tooth whorls) bearing tusk-like teeth.
The most well-preserved specimen
Specimen
A specimen is a portion/quantity of material for use in testing, examination, or study.BiologyA laboratory specimen is an individual animal, part of an animal, a plant, part of a plant, or a microorganism, used as a representative to study the properties of the whole population of that species or...
of Onychodus has been found at the Gogo Formation
Gogo Formation
The Gogo Formation in the Kimberley region of Western Australia is a Lagerstätte that exhibits exceptional preservation of a Devonian reef community.- Sedimentology :...
of Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
giving palaeontologists more information about the structure of the fish. Other species of Onychodus are known only from poor material based on isolated tusks, teeth and scales.
Description
A relatively complete specimen of Onychodus from Western Australia shows that its length was 47 cm long, the head being 10 cm in length with tusks 1.2 cm long. This specimen is only about half the size of larger individuals, since skulls measuring 19 cm in length have been found. However, a single tusk 4 cm long was found, showing that this specimen belonged to an even larger individual. Evidence found of the body reveals that a cross section of this fish would have been oval in shape. On the sides of the body, Onychodus had a series of pores which provided a sensory system
Sensory system
A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic...
that enabled the fish to locate prey and to position itself in narrow spaces. The tail fin is almost symmetrical around the vertebral column. It was rounded slightly and would have been very flexible with a broad sweep producing forward motion. A long fin extends posteriorly, along half the tail fin, forming the second dorsal fin. Evidence of the first dorsal fin is incomplete, but scientists believe that a fossil element found was its fin support. Ventrally, the large anal fin extends back beneath the anterior part of the tail fin. Scales that overlap anteriorly have been found, the smallest being only 5 mm across, and the largest 22 mm.
Classification and systematics
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the 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...
Onychodontida
Onychodontida
Onychodontida is a group of prehistoric fish. This order was it represents a small group of sarcopterygian fishes that lived between Late Silurian to Late Devonian period...
and the family
Family (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...
Onychodontidae
Onychodontidae
Onychodontidae is an extinct family of sarcopterygian fishes which lived in the Early Devonian period.-Phylogeny:*Sarcopterygii**Diabolepis***D. speratus**Langdenia***L. campylognatha**Meemannia***M. eos...
to which it belongs. The family name 'Onychodontidae' was created for Onychodus by the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
palaeontologist Arthur Smith Woodward
Arthur Smith Woodward
Sir Arthur Smith Woodward was an English palaeontologist.-Biography:Woodward was born in Macclesfield, Cheshire, England and was educated there and at Owens College, Manchester. He joined the staff of the Department of Geology at the Natural History Museum in 1882. He became assistant Keeper of...
in 1891. The group of onychodontiformes, described in 1973 by the late Dr. Mahala Andrews
Mahala Andrews
Mahala Andrews was a palaeontologist. During her career, Andrews made many studies on the prehistoric lobe-finned fish Onychodus....
, was characterized by a highly kinetic skull and tusk-like teeth.
Suggestions by palaeontologist John A. Long
John A. Long (paleontologist)
John Albert Long is an Australian paleontologist who is currently the Vice President of Research and Collections at the Natural History Museum of Los Angeles County. He is also an author of popular science books. His main area of research is on the fossil fish of the Late Devonian Gogo Formation...
refer to a close phylogenetic relationship between Onychodus and the basal lobe-finned fish Psarolepis
Psarolepis
Psarolepis is a genus of extinct lobe-finned fish which lived around 397 to 418 million years ago . Fossils of Psarolepis have been found mainly in South China and described by paleontologist Xiaobo Yu in 1998...
from China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. It is generally acknowledged that Onychodus and Psarolepis are both basal bony fishes, because of the absence of major features that unite coelacanths, lungfishes and tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
-like lobe-finned fishes. The position of Onychodus and Psarolepis in the cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
is outside the major clade of sarcopterygians (lobe-finned fishes), but at a position more derived than actinopterygians
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
(ray-finned fishes).
Early discovery and research
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
, USA, and were dated from Middle Devonian period. The remains made up the type specimen of Onychodus, later named Onychodus sigmoides, which was described and named by geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
John Strong Newberry. One of his plates of the findings has been drawn by geologist Grove Karl Gilbert
Grove Karl Gilbert
Grove Karl Gilbert , known by the abbreviated name G. K. Gilbert in academic literature, was an American geologist....
. The name of the species Onychodus sigmoides comes from the word "sigmoid", meaning "S shaped", as were the teeth of Onychodus. All species were found having this type of teeth, but O. sigmoides was the first species described. The Onychodus specimen found by Wagner was given to Orton Geological Museum at the Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...
.
The material collected of Onychodus sigmoides were a lower jaw and other single fragments, including parts of the skull, found at Ostrander
Ostrander, Ohio
Ostrander is a village in Delaware County, Ohio, United States. The population was 405 at the 2000 census.-Geography:Ostrander is located at ....
, Delaware County, Ohio
Delaware County, Ohio
Delaware County is a fast-growing suburban county in the state of Ohio, United States, within the Columbus, Ohio Metropolitan Statistical Area. According to the United States Census Bureau's 2004 population estimates, Delaware County's population of 142,503 made it the fastest growing county in...
. All remains were found as isolated elements because the bones of Onychodus were loosely joined and dispersed quickly after the death of the fish. Studies show that Onychodus sigmoides was about 3 m in length and was the largest known bony fish of the Middle Devonian period.
Later discoveries
Walter R. Gross
Walter R. Gross was a German palaeontologist. During his career, Gross made important studies on prehistoric fishes....
in 1965. Onychodus jaekeli has up to nine barbed tusks of equal length.
O. yassensis was found in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
at Canowindra site of Late Devonian, and described by palaeontologist David Lindley in 2002.
The new species found at Gogo Formation in Kimberley, Western Australia, Onychodus jandemarrai, is the best known species of the genus. It was described in 2006 based on extensive research by the late Dr. Mahala Andrews
Mahala Andrews
Mahala Andrews was a palaeontologist. During her career, Andrews made many studies on the prehistoric lobe-finned fish Onychodus....
, with colleagues Dr John Long, Dr Per Ahlberg, Prof. Ken Campbell and Dr Richard Barwick from material collected by the British Museum of Natural History, the Bureau of Mineral Resources and the Australian National University
Australian National University
The Australian National University is a teaching and research university located in the Australian capital, Canberra.As of 2009, the ANU employs 3,945 administrative staff who teach approximately 10,000 undergraduates, and 7,500 postgraduate students...
in Canberra
Canberra
Canberra is the capital city of Australia. With a population of over 345,000, it is Australia's largest inland city and the eighth-largest city overall. The city is located at the northern end of the Australian Capital Territory , south-west of Sydney, and north-east of Melbourne...
. New material gathered by Dr. Long from the limestone in the Gogo formation, where he visited many times, contributed much information. Although much is known of this species, there are missing details such as the shape of the posterior end of the tail, the pectoral and pelvic fins and the first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
. The name of species O. jandemarrai comes from the Aboriginal warrior Jandemarra who lived in that area.
Other less known species of Onychodus are: Onychodus anglicus (Woodward 1888) which was found in England, Onychodus arcticus (Woodward 1889) from Spitsbergen
Spitsbergen
Spitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...
, Norway, Onychodus hopkinsi and Onychodus ortoni (Newberry 1889) from North America, and Onychodus obliquidentatus (Jessen 1966), from Rhenish Massif, Germany.
Paleobiology
Many features of onychodont anatomy are known only from Onychodus itself. As other onychodontiformes, it has a highly kinetic and flexible skull. This unusual characteristic was due to the loose attachment of the skull bones, which sometimes overlapped, and were connected only by soft tissue and cartilage. Even the braincase was only partially made of bone.Other distinctive traits are related to the tusk whorls on the lower jaw. Because they could rotate, this was a different method of jaw articulation which did not compare with primitive ray-finned fish. The lower jaw was entirely articulated with cartilage, without an intermediate structure between the opposite sides, allowing the separation of the bones when prey was struck. Moreover, the loose articulation caused lateral movement, making the tusk walls move out of alignment. The parts of the lower jaw would have rotated inwards upon closing in order for the tusk whorls to fit exactly into the hollow spaces in the upper jaw. It is suggested that a ligament attachment and retractor mechanism existed in a pit under the tusk whorl, a unique condition in vertebrates. The capacity of the teeth on the lower jaw to fit with the tooth rows in the upper jaw, upon closure, kept the tusk whorls in place.
Ambush behavior
External links
- Onychodus, at PalaeosPalaeosPalaeos.com is a web site on biology, paleontology, cladistics and geology and which covers the history of Earth. The site is well respected and has been used as a reference by professional paleontologists such as Michael J. Benton, the professor of vertebrate palaeontology in the Department of...
. - Fossil fish found in American Aggregates Quarry, from Ohio Geology.
- Onychodontiformes, from University of BristolUniversity of BristolThe University of Bristol is a public research university located in Bristol, United Kingdom. One of the so-called "red brick" universities, it received its Royal Charter in 1909, although its predecessor institution, University College, Bristol, had been in existence since 1876.The University is...
. - Two fossils of Onychodus hopkinsi, 1 & 2, at New York State MuseumNew York State MuseumThe New York State Museum is a research-backed institution in Albany, New York, United States. It is located on Madison Avenue, attached to the south side of the Empire State Plaza, facing onto the plaza and towards the New York State Capitol...
.