Is the early evolution of bony fishes obscured?

Updated February 17, 2021
with the shifting of Anableps to the basal bony fish (Fig. 1).

For readers in a hurry,
the answer to the headline question is, ‘no.’

Romano 2021 reports:
“About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic.”

Clade membership: According to Wikipedia“Neopterygii is a subclass of ray-finned fish (Actinopterygii). They could move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient.” Electroreception is a lost sense, even if it has later been re-evolved within Gymnotiformes and catfishes, which possess nonhomologous teleost ampullae. Better control of the movements of both dorsal and anal fins, resulting in an improvement in their swimming capabilities. 

According to the Wikipedia cladogram, Neopterygii include

  1. Lepisosteifomres (gars)
  2. Amiformes (bowfins)
  3. Teleosts (the rest of the ray-fin fish)

By contrast,
in the large reptile tree (LRT, 1801+ taxa) the earliest unequivocal ray fin fish is Doliodus (Fig. 1)  from the Early Devonian. Gars, bowfins, lobefins, placoderms and spiny sharks nest within the bony fish. Moray eels are among the most primitive taxa, and these are derived from hybodontid sharks. Counterintuititively, some of the more bizarre-looking bony fish, often deep sea forms, are among the most primitive bony fish.

Figure 1. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Figure 1. Taxa from the LRT on one branch of the bony fish. Doliodus is one of these.

Romano 2021 continues:
“In the Middle Triassic neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatus on our understanding of their diversification after the largest mass extinction event of the past.”

Figure 1. Taxa from the LRT on the other branch of the bony fish, including spiny sharks, bony tongues, placoderms, catfish and lobefins.

Figure 2. Taxa from the LRT on the other branch of the bony fish, including spiny sharks, bony tongues, placoderms, catfish and lobefins derived from Gregorius.

Taxon inclusion in the LRT
permits the association of taxa that had traditionally not been associated before. Traditional memberships and traditional clades are not supported by the LRT where spines evolve to become fins and vice versa.


References
Romano C 2021. A hiatus obscures the early evolution of modern lineages of bony fishes. Frontiers. Earth Science 8:618853 doi: https://doi.org/10.3389/feart.2020.618853
https://www.frontiersin.org/articles/10.3389/feart.2020.618853/full

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