The origin of European eels and the origin of four-eyed fish

Updated January 16, 2021
with revised scores that now nest Xiphias, the swordfish, between Bavarichthys and Anguilla, the European eel. This is a novel hypothesis of interrelationships supported by skull shape and details, lack of ribs (in eels and swordfish) and a lack of pelvic fins in these two taxa. Traditionally these three taxa nest with other taxa. This clade is close to the anchovy clade in the LRT.

Today the extant topminnow,
Fundulus (Figs. 1), nests in ‘the Right Side’ of the Osteichyes, the clade that includes only ray fins (Fig. 2). The more taxa, the better cladodgram. Earlier errors are here corrected by the addition of taxa and data, some of which provide views not available earlier. Such work is still rewarding.

Figure 3. The four-eyed fish, Anableps, from three data sources. Compare to Fundulus in figure 4.

Figure 1. Skull of Fundulus from Gregory 1938.  Note the jugal (cyan blue). Compare to the barracuda, Sphyraena, in figure 2. 

Figure 2. Skull of the barracuda, Sphyraena. Compare to the killifish, Fundulus, in figure 1.

Figure 2. Skull of the barracuda, Sphyraena. Compare to the killifish, Fundulus, in figure 1.

Adding characters would never have resolved this issue.
Only adding taxa can do so, contra what so many PhDs say. Not sure why. It didn’t make sense in 2012 and it still doesn’t make sense in 2020. More characters are not needed. More taxa smooth out all the rough edges, illustrating the microevolution that ultimately creates macroevolution.

Part 2.
An overlooked European eel ancestor,
Bavarichthys (Arratia and Tischliner 2010; Late Jurassic) is here identified.

Figure 1. Bavarichthys is a big head/ short body anchovy from the Late Jurassic. Now it is ancestral to European eels.

Figure 1. Bavarichthys is a big head/ short body anchovy from the Late Jurassic. Now it is ancestral to European eels.

Bavarichthys incognitus
(Arratia and Tischlinger 2020; Late Jurassic) was originally considered a member of the “Crossognathiforms with a large head about 30% in standard length and a characteristically elongate snout, more than 25% in head length. In the LRT it nests between the extant anchovy, Elops and the extant European eel, Anguilla.

Figure 5. Skull of Anguilla, the European eel, compares well with that of Bavarichthys. Note the loss and reduction of preorbital bones.

Figure 6. Skull of Anguilla, the European eel, compares well with that of Bavarichthys. Note the loss and reduction of preorbital bones.

Protanguilla palau 
(Johnson et al. 2011; 18cm; Fig. 7) is a newly discovered ‘living fossil” transitional taxon from Bavarichthys to Anguilla. Distinct from eels, Protanguilla has gill rakers, fewer than 90 vertebrae, pterotic does not approach anterior margin of pterosphenoid, and the latter bone participates in the posterior margin of the orbit. Eels are traditionally associate with Elops. These new taxa fill in the gaps.

Figure 6. Protanguilla is a recently discovered short eel, transitional from Bavarichthys in the LRT.

Figure 7. Protanguilla is a recently discovered short eel, transitional from Bavarichthys in the LRT.

The nesting of Bavarichthys
basal to Protanguilla and Anguilla appears to be a novel hypothesis of interrelationships. Let me know if there is an earlier citation so I can promote it.


References
Arratia G and Tischlinger H 2010. The first record of Late Jurassic crossognathiform fishes from Europe and their phylogenetic importance for teleostean phylogeny. Fossil Record 13(2):317-341.
Johnson GD, Ida H, Sakaue J, Sado T, Asahida T and Miya M 2012. A ‘living fossil’ eel (Anguilliformes: Protanguillidae, fam nov) from an undersea cave in Palau. Proceedings of the Royal Society. (in press): 934–943. doi:10.1098/rspb.2011.1289

denmark/scientists-solve-the-riddle-of-eel-evolution/1420760
wiki/Killisfish – Fundulus
wiki/Pupfish
wiki/Anableps

wiki/Protanguilla

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.