The Palaeozoic era is famous for its variety of fish, including the ancestors of the land vertebrates. However fish have also changed dramatically since then, and now some 95% of all living fish species are teleosts, which are not found at all until the Mesozoic. Here I have tried to give examples to illustrate the natural history of this group, which have taken over the seas at least as much as mammals and birds have the land and sky.
Drawings are based directly off the references given but are my own attempts to interpret them as living fish, for which I have no actual qualifications and may easily have made mistakes. All lengths are given as total lengths, i.e. include the tail fin or an estimate of it.
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The Triassic spans about 50 million years, broken down as follows:
| 252-247 | Induan, Olenekian |
| 247-237 | Anisian, Ladinian |
| 237-227 | Carnian |
| 227-206 | Norian |
| 206-201 | Rhaetian |
Fossil teleosts make their first appearance in this period. Along with Halecomorphi like modern bowfins and Ginglymodi like gars, these are part of a group that share mobile upper jaws, where the maxilla on each side can be rotated forward to cover the sides of the mouth during feeding. Most also have a supporting supramaxilla except when the mouth is small.
Early teleosts are set apart by also having the premaxilla at the front of the upper jaw detached. Sometimes this can be further specialized like in early Marcopoloichthys, small fish with no teeth and only a few scales, which have a long curved premaxilla presumably involved in suction feeding.
In most others the premaxilla has a short ascending process and can be pushed forward. The main Triassic group are the Pholidophoridae, named for their covering of thick ganoid scales. These are small marine fish that probably fed on plankton except for the very largest, Pholidorhynchodon, which were predatory on other kinds.
References for fish:
- Tintori, Sun, Lombardo, et al. (2007). New specialized basal neopterygians (Actinopterygii) from Triassic of the Tethys realm.
- Arratia (2013). Morphology, taxonomy, and phylogeny of Triassic pholidophorid fishes (Actinopterygii, Teleostei).
- Tintori, Sun, Ni, et al. (2015). Oldest stem Teleostei from the Late Ladinian (Middle Triassic) of Southern China.
- Arratia & Schultze (2024). The oldest teleosts (Teleostomorpha): their early taxonomic, phenotypic, and ecological diversification during the Triassic.
The Jurassic spans about 60 million years, broken down as follows:
| 201-193 | Hettangian, Sinemurian |
| 193-184 | Pliensbachian |
| 184-175 | Toarcian |
| 175-165 | Aalenian, Bajocian, Bathonian |
| 165-155 | Callovian, Oxfordian |
| 155-143 | Kimmeridgian, Tithonian |
During this period some teleosts start appearing in freshwater. The earliest known are the Archaeomaenidae, which have a free premaxilla but no ascending process. They first show up already on opposite ends of Pangaea, with Zaxilepis in Asia and Oreochima of similar size in Antarctica.
Later Aphnelepis and Archaeomaene are found together in Australia. The first have thick scales in front but thinner ones toward the tail, while in the second the whole body has only leptoid scales. These take the form of thin overlapping plates without outer enamel or articulations as in ganoid scales, providing a more flexible and streamlined covering.
A few other families are known from the Late Jurassic of central Africa and possibly Brazil, including Catervariolidae, Ankylophoridae, and Pleuropholidae. I am hoping to find a copy of Saint-Seine (1955, 1962) before I try writing about them.
References for fish:
- Su (1994). New Early Jurassic actinopterygians from Weixin, Yunnan.
[N.B. the scale bars do not agree with the measurements.]
- Bean (2021). Revision of the Mesozoic freshwater fish clade Archaeomaenidae.
[N.B. misquoted size for Z.]
- Bean (2024). A revision of the Late Jurassic fish Aphnelepis australis from the Talbragar Fossil Fish Bed of New South Wales, Australia.
The Early Jurassic marks a radiation of new teleosts with homocercal tails, where the vertebral column stops instead of extending along the rays into the fin. They also all share leptoid scales so are more flexible and built for propulsion than other relatives. The first known are Proleptolepis from England and some smaller kinds from Chile.
By the Late Jurassic these have split into several major groups, all but the first of which continue through at least the Cretaceous period:
- Ascalaboidiformes
- a. Ichthyodectiformes
b. Crossognathiformes
- a. Osteoglossomorpha (e.g. modern bonytongues)
b. Elopomorpha (e.g. modern eels)
- Otomorpha (e.g. modern herrings, carps, catfish)
- Euteleostomorpha (e.g. modern trouts, dragonfish, cods, gobies, perches)
Ichthyodectiformes include early Occithrissops, which probably fed on small particles, and later types like Thrissops that were predators of smaller fish. The latter are also one of a few fish where fossils have preserved a colour pattern, with small dark marks on the scales.
Crossognathiformes are first represented by Varasichthys and relatives from Chile and Cuba. Then Luisiella and the orthogonikleithrids Cavenderichthys, both placed somewhere between surviving lineages (crown teleosts), are the oldest examples of homocercal teleosts found in freshwater habitats.
Otherwise these groups are mostly known from the shallow seas around Europe. Here both ascalaboids like Tharsis and smaller orthogonikleithrids are common. There are also several Elopomorpha like Anaethalion as well as some leptocephalus larvae characteristic of that group.
Otomorpha are only represented by Tischlingerichthys, though by this point others had likely started to diversify in freshwater. Osteoglossomorpha are also largely freshwater and along with euteleosts are not certainly known until the Cretaceous.
References for fish:
- Nybelin (1974). A Revision of the Leptolepid Fishes.
- Schaeffer & Patterson (1984). Jurassic Fishes from the Western United States, With Comments on Jurassic Fish Distribution.
- Arratia (1987). Anaethalion and similar teleosts (Actinopterygii, Pisces) from the Late Jurassic (Tithonian) of Southern Germany and their relationships.
- Frickhinger (1994). Die Fossilien von Solnhofen / The fossils of Solnhofen.
[N.B. describes eyes as large in Tharsis and smaller in Anaethalion but compare details in Nybelin and Arratia.]
- Arratia (1997). Basal Teleosts and Teleostean Phylogeny.
- Tischlinger (1998). Erstnachweis von Pigmentfarben bei Plattenkalk-Teleosteern.
- Sferco, López-Arbarello, Báez (2015). Anatomical description and taxonomy of †Luisiella feruglioi (Bordas), new combination, a freshwater teleost (Actinopterygii, Teleostei) from the Upper Jurassic of Patagonia.
- Bean & Arratia (2019). Anatomical revision of the Australian teleosts Cavenderichthys talbragarensis and Waldmanichthys koonwarri impacting on previous phylogenetic interpretations of teleostean relationships.
References for distribution, dates, and classification:
- Wenz, Bernier, Barale, et al. (1994). L’ichthyofaune des calcaires lithographiques du Kimméridgien supérieur de Cerin (Ain, France).
- Cúneo, Ramezzani, Scasso, et al. (2013). High-precision U-Pb chronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic.
- Betancur-R, Wiley, Arratia, et al. (2017). Phylogenetic classification of bony fishes.
- Arratia, Schultze, Tischlinger (2019). On a remarkable new species of Tharsis, a Late Jurassic teleostean fish from southern Germany: its morphology and phylogenetic relationships.
- Tischlinger & Schweigert (2020). Neuer Ammonitenfund ermöglicht Alterseinstufung der Fossillagerstätte Ettling / New ammonite record allows dating of the Ettling Fossillagerstätte. [See also stratigraphy for reviewed locations.]
- Alvarado-Ortega & Alves (2022). Nusaviichthys nerivelai gen. et sp. nov., an Albian crossognathiform fish from the Tlayúa lagerstätte, Mexico.
- Parey, Louis, Montfort, et al. (2023). Genome structures resolve the early diversification of teleost fishes.
