The barracuda and the ladyfish

Sounds like a Disney cartoon,
but it’s the latest match made on the large reptile tree (LRT, 2206 taxa). Now Sphyraena, the barracuda, and Elops, the ladyfish (Figs 1 and 2) nest together between the cod (Gadus) and the cobia (Rachycentron). Let’s take a closer look.

These newly evolved traits all make Elops look like a more primitive taxon.
That’s what makes phylogenetic analysis a little tricky. That’s why it’s important to do a little ‘housekeeping‘ every so often. Take a look at a series of barracuda larvae shown below (Fig 4) for confirmation of this novel hypothesis on interrelationships.

These bauplan changes between Sphyraena and Elops are part of the reason
why this interrelationship went unnoticed until now. Related taxa, like the cod and cobia, share more traits with the barracuda. Elops is the oddball, often, but not always, the morphological exception at its present nesting in the LRT. Even so, trust your software because it recovers a longer list of similar traits that nest Elops with Sphyraena rather than elsewhere. That’s called maximum parsimony, the guiding principle behind phylogenetic analysis. And that’s why “Pulling a Larry Martin” (relying on just one or only a few traits) should be avoided.

Matsuura and Suzuki 1997 provided a diagram
of barracuda embryos and hatchlings (Fig 4) in which the rostrum is initially short and the orbit large relative to older barracuda. Note the dual dorsal fins at the last stage. Dual dorsal fins are found in related cod (Gadus). The anterior dorsal fin is retained by Elops, the ladyfish. The anterior dorsal fin is lost in adult Sphyraena, the barracuda. With these observations, larval development in Sphyraena, the barracuda, supports the recovery of Elops, the ladyfish as a close relative in the LRT largely due to phylogenetic miniaturization and reversal.

According to Wikipedia,
Elops is a member of the Elopiformes, then the Actinopterygii. Traditional members of the elopiformes include the tarpon, Megalops. The LRT does not support that hypothesis of interrelationships. Wikipedia does not connect the barracuda and the ladyfish.

Rather than indicate broad, vague and nebulous interrelationships,
like Wikipedia reports, the LRT documents the interrelationships and ancestries of every included taxon down to the level of genus back to the last common ancestor, a Cambrian or Ediacaran nematode worm close to Enoplus. As always, this novel hypothesis of interrelationships (Fig 3) now needs competing studies for confirmation, refutation or modification.

References
Matsuura Y and Suzuki K 1997. Larval development of two species of barracuda, Sphyraena guachancho and S. tome (Teleostei: Sphyraenidae), from southeastern Brazil. Ichthyological Research 44:369–378.