Summary
The following figure is a summarized phylogenetic tree for the Teleostei, showing that the stem line of the taxon and its ancestor stem line (i.e. the stem-Neopterygii) are documented by transitional fossils. As will be seen below, the red star shown below represents multiple transitional fossils.
The major transitions represented by the above tree are the development of characteristics that distinguish (1) the Neopterygii from the Chondrostei and (2) the Teleostei from the Holostei. The main differences are as follows:
- The Neopterygii diverged from the Chondrostei with the acquisition of a better control of the movements of both dorsal and anal fins, resulting in an improvement in their swimming capabilities. They additionally acquired several modifications in the skull, which allowed the evolution of different feeding mechanisms (López-Arbarello, 2012). The Chondrostei, on the other hand, lost much of the bone in their skeleton, which has ended up partially cartilaginous.
- The major differences between the Teleostei and the Holostei occur mainly in the head and the tail. The teleosts are characterized primarily by shared derived features (synapomorphies) in the tail region, while the synapomorphies of the Holostei pertain mainly to skull structure (Merck, 2019c).
Introduction
The teleosteans (class Teleostei, clade Neopterygii) comprise a clade that contains most of the ray-finned fishes alive in the world today, with nearly 30,000 species (Ravi and Venkatesh, 2018). They consist of two major divisions ("megacohorts"), the Elopocephalai and the Osteoglossocephalai, as shown in the following phylogenetic tree:
The crown group of the Teleostei, represented above by the black dot, comprises all living teleost fishes, together with all extinct species descended from the last common ancestor of all living Teleostei.
Below we will consider the evolution of the stem lines of the Teleostei and of the higher-order clade to which they belong, the Neopterygii. These stem lines are depicted as red and blue lines respectively in the above phylogenetic tree.
This tree is summarized in the context of geological time in the figure below:
Below we will consider the evolution of the stem lines of the Teleostei and of the higher-order clade to which they belong, the Neopterygii. These stem lines are depicted as red and blue lines respectively in the above phylogenetic tree.
This tree is summarized in the context of geological time in the figure below:
This time tree is constrained by fossils that will be discussed below. It indicates that the successive divisions of the Actinopterygii (ray-finned fishes) that gave rise to the Teleostei took place between the Early Devonian and the Late Carboniferous or Permian, a period of up to 165 million years.
We will now consider the evolution of the Teleostei in three stages:
We will now consider the evolution of the Teleostei in three stages:
- The stem-Neopterygii
- The stem-Teleostei
- Within the crown-Teleostei
The stem group of the Neopterygii
The stem-Neopterygii are quite well represented in the fossil record. Their phylogenetic relationships are shown in the tree below:
The oldest known member of the stem-Neopterygii is Discoserra pectinodon, described from the Early Carboniferous (Serpukhovian) Bear Gulch Limestone member of the Heath Formation at a location south of Becket, Fergus County, Montana (Lund, 2000; Latimer and Giles, 2018). This species is illustrated below, together with other members of the stem group for which public-domain images are available (for a larger view, click on image):
Names in red indicate that the fossil is younger than the oldest known crown-group fossil.
* after name indicates that the image represents a life restoration
* after name indicates that the image represents a life restoration
The images shown above are numbered in order from most basal towards the crown group, but no obvious trends can be seen.
The oldest known crown-group neopterygian is Watsonulus eugnathoides, a member of the crown-Holostei, found in the Early Trassic (Induan) Middle Sakamena Formation, Sakamena Group, Ambilombe Bay, Madagascar (Benton et al, 2015). No public-domain image is available.
The stem group of the Neopterygii developed from Early Carboniferous to Early Triassic time, as shown in the time tree below:
The oldest known crown-group neopterygian is Watsonulus eugnathoides, a member of the crown-Holostei, found in the Early Trassic (Induan) Middle Sakamena Formation, Sakamena Group, Ambilombe Bay, Madagascar (Benton et al, 2015). No public-domain image is available.
The stem group of the Neopterygii developed from Early Carboniferous to Early Triassic time, as shown in the time tree below:
As indicated above, the stem-to-crown transition for the Neopterygii could have lasted as long as 75 million years. However, most of the stem-group fossils do not occur within that time interval, but appear after the crown group. These fossils represent post-crown descendants of ancestors that would have separated from the stem line during or before the Early Triassic.
The stem group of the Teleostei
The stem-Teleostei are very well represented in the fossil record. Their phylogeny is shown below in a combined tree taken from two recent publications:
The oldest known member of the stem-Teleostei is the genus Parapholidophorus, which has been described from the Middle Triassic (Ladinian) of Catalonia, Spain (Beltan, 1972, cited in Fossilworks; Arratia, 2017). No image is available of that fossil, which was not assigned to a species, but a Late Triassic species of genus Parapholidophorus, together with other members of the stem group, are shown below (click on image for larger version):
Names in red indicate that the fossil is younger than the oldest known crown-group fossil.
* after name indicates that the image represents a life restoration
* after name indicates that the image represents a life restoration
The images shown above are numbered in order from most basal towards the crown group, but no obvious trends can be seen, apart from perhaps a tendency for the tails to become more like those of modern teleost fish.
The earliest known member of the teleostean crown group is Anaethalion zapporum, a member of the total-group Elopomorpha (synonymous with the Elopocephalai) found in the Late Jurassic (Late Kimmeridgian) Rögling Formation at the village of Schamhaupten, near Eichstätt, Bavaria, Germany (Benton et al, 2015). No image of this species is available in the public domain, but an un-named species of the genus Anaethalion is shown in the next section below together with other members of the crown-Teleostei.
The stem group of the Teleostei developed from Middle Triassic to Late Jurassic time, as illustrated below:
The earliest known member of the teleostean crown group is Anaethalion zapporum, a member of the total-group Elopomorpha (synonymous with the Elopocephalai) found in the Late Jurassic (Late Kimmeridgian) Rögling Formation at the village of Schamhaupten, near Eichstätt, Bavaria, Germany (Benton et al, 2015). No image of this species is available in the public domain, but an un-named species of the genus Anaethalion is shown in the next section below together with other members of the crown-Teleostei.
The stem group of the Teleostei developed from Middle Triassic to Late Jurassic time, as illustrated below:
The above plot indicates that the transition from the appearance of the teleostean stem group to the appearance of the crown-Teleostei could have lasted as long as 85 million years.
Evolution within the crown-Teleostei
In this section we are concerned with the origin of the orders (which have names ending in “formes”) and more highly ranked taxa such as superorders into which the elasmobranch crown group is divided. A phylogenetic tree, derived from two recent publications, of fossils interpreted to belong to the teleostean crown group is shown below:
Images of the fossils for which public-domain images are available are shown below (for a larger view, click on image):
Illustrated above are stem-Elopiformes (Anaethalion and Paraelops), stem-Albuliformes (Osmeroides and Brannerion) and stem-Osteoglossocephalai (Cavenderichthys, Waldmanichthys, Orthogonikleithrus and Leptolepides).
The time frame of evolution of the crown-Teleostei, at least for the fossils interpreted to belong to the crown group, is shown below:
The time frame of evolution of the crown-Teleostei, at least for the fossils interpreted to belong to the crown group, is shown below:
The above plot suggests the following durations of stem-crown transitions within the crown-Teleostei:
- Ostariophysi: Up to 21 million years
- Osteoglossocephalai: Up to 36 million years
- Albuliformes: Up to 25 million years
- Elopiformes: Up to 36 million years
Image credits - Teleosteans
- Header (Banded Archerfish, Toxotes jaculatrix) By Chrumps, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Ebenaqua ritchei By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Bobosatrania groenlandica By DiBgd [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Discoserra pectinodon By Gyik Toma (Tommy the paleobear) from Romania [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]
- Brembodus ridens By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Gibbodon cenesis By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Mesturus verrucosus By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Mesturus sp. By Raimond Spekking / CC BY-SA 4.0 (via Wikimedia Commons)
- Arduafrons prominoris By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Eomesodon gibbosus By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Peltopleurus lissocephalus By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Dipteronotus ornatus By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Pachycormus bollensis By Daderot [CC0]
- Orthocormus cornutus (13a) By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Orthocormus cornutus (13b) By DiBgd [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Hypsocormus insignis (14a) By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Hypsocormus insignis (14b) By Dmitry Bogdanov [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Vinctifer comptoni By Hectonichus [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Aspidorhynchus acutirostris By Daderot [CC0]
- Belonostomus muensteri By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Prohalecites sp. By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Eurycormus speciosus By Daderot [CC0]
- Malingichthys nimaiguensis By A. Tintori, Z. Y. Sun, P. G. Ni, C. Lombardo, D. Y. Jiang and R. Motani. 2015, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
- Pholidoctenus serianus By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Parapholidophorus nybelini By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Pholidophorus latiusculus By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Pholidorhynchodon malzannii By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Lombardichthys gervasuttii By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Siemensichthys macrocephalus By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Ankylophorus similis By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Dorsetichthys bechei By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Leptolepis coryphaenoides By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Tharsis dubius By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Ebertichthys ettlingensis By Martin Ebert [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]
- Ascalabos voithii By Ghedoghedo [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Varasichthys ariasi (33a) By Sergio Soto-Acuña; Rodrigo A. Otero; David Rubilar-Rogers; Alexander O. Vargas [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Varasichthys ariasi (33b) By Gloria Arratia. Published by Sergio Soto-Acuña; Rodrigo A. Otero; David Rubilar-Rogers; Alexander O. Vargas [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Luisichthys vinalensis By Nobu Tamura (http://spinops.blogspot.com) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
- Anaethalion sp. By Ghedoghedo [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
- Paraelops cearensis By Ghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
- Osmeroides lewesiensis By creativecommons.org/licenses/by/4.0/ © The Trustees of the Natural History Museum, London
- Brannerion sp. By Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
- Cavenderichthys talbragarensis By Michael Frese , Gerda Gloy, Rolf G. Oberprieler, Damian B. Gore, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
- Waldmanichthys koonwarri By Source: Museums Victoria Copyright Museums Victoria / CC BY (Licensed as Attribution 4.0 International)
- Orthogonikleithrus hoelli By Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
- Leptolepides sprattiformis By Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons