The barracuda (genus: Sphyraena) enters the LRT

Sphyraena barracuda
is one of the terrors of the sea (Fig. 1), but it’s skull is a work of art and an engineering marvel (Fig. 2).

FIgure 1. Sphyraena barracuda in vivo. Note the anterior placement of the pelvic fins relative to the very long tail.

FIgure 1. Sphyraena barracuda in vivo. Note the anterior placement of the pelvic fins relative to the very long tail.

Today
the barracuda enters the large reptile tree (LRT, 1489 taxa (and see below)) alongside the swordfish (Xiphias gladius). Both are open water, fast, predatory swimmers derived from the bottom dwelling, slow-moving, sometimes air-breathing bowfin, Amia (Fig. 3). Note (Fig. 1) the reduction (but not absence!) of the postorbital and jugal bones in the barracuda along with the lack of teeth on the maxilla relative to the bowfin (Fig. 3).

Figure 1. The skull of the barracuda (genus: Sphyraena) with bones identified with colors.

Figure 1. The skull of the barracuda (genus: Sphyraena) with bones identified with colors.

Sphyraena barracuda (originally Esox sphyraena Linneaus 1758; up to 165cm in length) is the extant barracuda. Note the tiny remnants of the postorbital and jugal rimming the sclerotic ring. The maxilla terminates anterior to the orbit, but the jaw joint does not. The caudal region makes up most of the body based on the anterior migration of the pelvic fins. Barracudas are fast and wide-ranging open water swimmers. They have lost the ability or need to breathe air at the surface. Females can release 5000 to 30,000 eggs and hatchlings resemble little adults.

FIgure 3. The bowfin, Amia calva, is basal to both the electric eel and halibut in the LRT.

FIgure 3. The bowfin, Amia calva, is basal to both the electric eel and halibut in the LRT.

The point of these figures
is to simplify and illustrate the evolutionary paths derived taxa take, gaining and losing traits to more effectively adapt to their niche or to exploit a new niche, in this case, open water predation.

To those of you who thought
a small set of generalized character traits could not possibly lump and separate 360 tetrapod taxa, I hope you tone down your attacks now that the taxon list is 4x that number and includes everything from fish to birds.

To those of you who thought
digitally painting bones with transparent colors was a bad idea, I hope you have been won over by a technique that helps readers understand graphic images better than with line drawings and arrows attached to labels. I was not the first to employ this graphic method, which is gaining wider acceptance and use.

Figure 6. Subset of the LRT with Xiphias added.

Figure 4. Subset of the LRT with Xiphias and Sphyraena added.

Figure 3. Subset of the LRT focusing on bony ray fin fish and kin. Here Devonian Cheirolepis nests with extant deep sea Malacosteus.

Figure 4b. Subset of the LRT focusing on bony ray fin fish and kin when the LRT included 1524 taxa.

The LRT continues to document
a gradual accumulation of derived traits at every node, more accurately echoing evolutionary events than prior attempts employing fewer taxa and those excluding key taxa based on tradition and bias. Please use it as a guide when selecting taxa for your more focused studies.


References
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/Amia
wiki/Xiphias
wiki/Sphyraena

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