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The parts of the bones directed outward from the body trunk were flattened. The pelvis had long, tapering pubic branches (pubic rami) that possibly met in a cartilaginous symphysis. The ventral fins also contained the major bones of the hind legs, femur, tibia, and fibula. Ankle bones (tarsal bones) and toes cannot yet be identified. The limbs were oriented to the side and could only be moved back and forth about 20 to 25°. The anal fin sat on a basal, fleshy peduncle. The caudal fin possessed three lobes, initially asymmetrical in basal forms and becoming more symmetrical externally in later forms. Only modern round scales with a median projection on the inner side, lacking a
cover all of the fins, which does not happen until after metamorphosis in genera like ''
Tristichopterids (Tristichopteridae) were a diverse and successful group of
A microanatomical and histological study of the paired fin skeleton of the Devonian sarcopterygian ''Eusthenopteron foordi
Journal of Paleontology'' 81: 143–153. All tristichopterids had become extinct by the end of the Late Devonian.
, such as the humerus, ulna and radius, can already be recognized.
tetrapodomorph
The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advan ...
fishes living throughout the Middle and Late Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
. They first appeared in the Eifelian
The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage.
North American ...
stage of the Middle Devonian. Within the group sizes ranged from a few tens of centimeters ('' Tristichopterus'') to several meters ('' Hyneria'' and ''Eusthenodon
''Eusthenodon'' (Greek for “strong-tooth” – ''eustheno''- meaning “strength”, -''odon'' meaning “tooth”) is an extinct genus of tristichopterid tetrapodomorphs from the Late Devonian period, ranging between 383 and 359 million yea ...
'').
Some tristichopterids share some of the features of the elpistostegalia
Elpistostegalia or Panderichthyida is an order of prehistoric lobe-finned fishes which lived during the Middle Devonian to Late Devonian period (about 385 to 374 million years ago). They represent the advanced tetrapodomorph stock, the fish ...
ns, a diverse clade of fishes close to the origin of (and including) tetrapods. This mainly concerns the shape of the skull and a reduction in size of the posterior fins.
An old and persistent notion is that ''Eusthenopteron
''Eusthenopteron'' (from el, εὖ , 'good', el, σθένος , 'strength', and el, πτερόν 'wing' or 'fin') is a genus of prehistoric sarcopterygian (often called lobe-finned fishes) which has attained an iconic status from its close ...
'' was able to crawl onto land using its fins. However, there is no evidence actually supporting this idea.M. Laurin, F. J. Meunier, D. Germain, and M. Lemoine 2007A microanatomical and histological study of the paired fin skeleton of the Devonian sarcopterygian ''Eusthenopteron foordi
Journal of Paleontology'' 81: 143–153. All tristichopterids had become extinct by the end of the Late Devonian.
Description
The Tristichopteridae were medium-sized (''Tristichopterus'', 30 cm) to very large fishes. The smallest forms (such as ''Tristichopterus'') attained lengths of 30 cm, and the largest forms (''Hyneria'') could grow several meters long, possessed teeth up to 5 cm long, and were the largest predators in their faunal communities.tetrapodomorphs The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advance ...
The parts of the bones directed outward from the body trunk were flattened. The pelvis had long, tapering pubic branches (pubic rami) that possibly met in a cartilaginous symphysis. The ventral fins also contained the major bones of the hind legs, femur, tibia, and fibula. Ankle bones (tarsal bones) and toes cannot yet be identified. The limbs were oriented to the side and could only be moved back and forth about 20 to 25°. The anal fin sat on a basal, fleshy peduncle. The caudal fin possessed three lobes, initially asymmetrical in basal forms and becoming more symmetrical externally in later forms. Only modern round scales with a median projection on the inner side, lacking a cosmine
Cosmine is a spongy, bony material that makes up the dentine-like layers in the scales of the lobe-finned fishes of the class Sarcopterygii. Fish scales that include layers of cosmine are known as cosmoid scales.
Description
As traditionally ...
layer occurred in the family.lepidotrichia
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 ...Polyodon
The American paddlefish (''Polyodon spathula,'' also known as a Mississippi paddlefish, spoon-billed cat, or spoonbill) is a species of ray-finned fish. It is the only living species of paddlefish (Polyodontidae). This family is most closely r ...
''. This might indicate that ''Eusthenopteron'' developed directly, with the hatchling already attaining the general body form of the adult.S. Cote; R. Carroll; R. Cloutier; L. Bar-Sagi (September 2002). "Vertebral development in the Devonian Sarcopterygian fish Eusthenopteron foordi and the polarity of vertebral evolution in non-amniote tetrapods". Journal of Vertebrate Paleontology. 22 (3): 487–502. doi:10.1671/0272-4634(2002)022 487:VDITDS.0.CO;2. ISSN 0272-4634.
Taxonomy
In the past, the Tristichopteridae were assigned to theOsteolepiformes
Osteolepiformes, also known as Osteolepidida, is a group of prehistoric lobe-finned fishes which first appeared during the Devonian period. The order contains the families Canowindridae, Megalichthyidae, Osteolepididae and Tristichopteridae. ...
, a group of lobe-fins that is now considered paraphyletic
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
. The sister taxon of the Tristichopteridae is ''Spodichthys'', which is very similar to the Tristichopteridae, but differs from them in the position of the extratemporal bone.
* '' Cabonnichthys''
* '' Canningius''
* '' Edenopteron''
* ''Eusthenodon
''Eusthenodon'' (Greek for “strong-tooth” – ''eustheno''- meaning “strength”, -''odon'' meaning “tooth”) is an extinct genus of tristichopterid tetrapodomorphs from the Late Devonian period, ranging between 383 and 359 million yea ...
''
* ''Eusthenopteron
''Eusthenopteron'' (from el, εὖ , 'good', el, σθένος , 'strength', and el, πτερόν 'wing' or 'fin') is a genus of prehistoric sarcopterygian (often called lobe-finned fishes) which has attained an iconic status from its close ...
''
* '' Heddleichthys''
* '' Hyneria''
* '' Jarvikina''
* '' Langlieria''
* ''Mandageria
''Mandageria fairfaxi'' (Pronunciation: Man-daj-ee-ree-a fair-fax-i) is an extinct lobe-finned fish that lived during the Late Devonian period (Frasnian – Famennian). It is related to the much larger '' Hyneria''; although ''Mandageria'' was sm ...
''
* '' Notorhizodon''
* ''Platycephalichthys
''Platycephalichthys'' is a genus of tristichopterid lobe-finned fish which lived during the middle Devonian, upper Givetian stage.
Phylogeny
Below is a cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") i ...
''
* '' Tristichopterus''
The following phylogeny is modified from Schwartz (2012). Here, ''Platycephalichthys'' is not considered a member of the Tristichopteridae:
References
*Ahlberg, PE and Z Johanson (2001). "Second tristichopterid (Sarcopterygii, Osteolepiformes) from the Upper Devonian of Canowindra, New South Wales, Australia, and phylogeny of the Tristichopteridae." in ''Journal of Vertebrate Paleontology'' 17:563-673. *Johanson, Z. and P.E. Ahlberg (1997). "New tristichopterid (Osteolepiformes; Sarcopterygii) from the Mandagery Sandstone (Famennian) near Canowindra, N.S.W., Australia." in ''Transactions of the Royal Society of Edinburgh'' 88:39-53. Prehistoric lobe-finned fish families Carboniferous bony fish Devonian bony fish Middle Devonian first appearances Late Devonian animals Late Devonian extinctions {{paleo-lobefinned-fish-stub