The tarpon (Megalops): closer to piranhas than to eels in the LRT

…Well, at least it is not related
to the two tested eels in the LRT, the moray eel (Gymnothorax) and the European eel (Anguilla), which we looked at earlier here and here. The former is closer to lobe finned rhizodontids from the Devonian and Carboniferous. The latter is closer to barracuda. Are there other eels out there the tarpon might be closely related to? I’ll find out as I add taxa, I suppose.

Figure 1. Tarpon (Megalops) skeleton.

Figure 1. Tarpon (Megalops) skeleton. Not very eel-like. Closer to the piranha.

Traditionally
the tarpon (Megalops atlanticus) has been considered an eel relative. Perhaps this is based on its life cycle, which includes elongated larvae born at sea. According to the Tennesee Aquarium, hatchling piranhas are also born tiny and slender.

Figure 2. Tarpon (Megalops) skull with tetrapod skull colors added. Note the large plate like postorbital and jugal here. Compare to Figure 3.

Figure 2. Tarpon (Megalops) skull with tetrapod skull colors added. Note the large plate like postorbital and jugal here. Compare to Figure 3.

After testing
in the large reptile tree (LRT, 1511 taxa) Megalops (Figs. 1,2) nested with the piranha, Serrasalmus (Fig. 3). The former has hundreds of the tiniest teeth lining its jaws. The latter has a few large triangular teeth.

Figure 4. Piranha (Serrasalmus) skull.

Figure 4. Piranha (Serrasalmus) skull.

Megalops atlanticus (Cuvier and Valenciennes 1847; up to 2.5m) is the extant Atlantic tarpon. Fast-swimming Megalops has large eyes and large fins. This open-seas predator sometimes uses its swim bladder as a lung by gulping air.

Figure 3. Subset of the LRT focusing on fish and updated here.

Figure 3. Subset of the LRT focusing on fish and updated here.

References
Cuvier G and Valenciennes A 1847. Histoire naturelle des poissons. Tome dix-neuvième. Suite du livre dix-neuvième. Brochets ou Lucioïdes. Livre vingtième. De quelques familles de Malacoptérygiens, intermédiaires entre les Brochets et les Clupes. 19: i-xix + 1-544 + 6 pp. Pls. 554-590.

wiki/Piranha
wiki/Serrasalmus
wiki/Tarpon

 

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