Two piranhas nest with the bowfin in the LRT

Updated August 4, 2020
with new cladogram and other details. The addition of many more taxa has separated these two early entries to the LRT. Please see more recent posts.

The extant Amazon river piranha,
Serrasalmus, nests in the large reptile tree (LRT, 1504 taxa; Figs. 1, 2) with the Jurassic pre-piranha, Diapedium (Fig. 3), itself derived from the bottom-dwelling bowfin, Amia (Fig. 4).

Figure 1. Skeleton of the red eye piranha, Serrasalmus rhombeus, in lateral view. Distinct from its bottom foraging predecessor, Alma, the skull and torso of this more agile swimmer are deeper and narrower.

Figure 1. Skeleton of the red eye piranha, Serrasalmus rhombeus, in lateral view. Distinct from its bottom foraging predecessor, Alma, the skull and torso of this more agile swimmer are deeper and narrower. Skeleton from ©Steve Huskey and used with permission.

Like Amia,
the postorbital and jugal in Serrasalmus form large cheek plates, replacing the lost squamosal.

Figure 2. GIF movie, 2 frames, identifying bones by color, the same as in tetrapods. The jugal is missing here. The quadrate is hidden beneath. The parietal forms a sagittal crest. The nostrils are large. Skeleton from ©Steve Huskey and used with permission.

Figure 2. GIF movie, 2 frames, identifying bones by color, the same as in tetrapods. The jugal is missing here. The quadrate is hidden beneath. The parietal forms a sagittal crest. The nostrils are large. Skeleton from ©Steve Huskey and used with permission.

Dapedium caelatum (Leach 1822; Thies and Hauff 2011; Lower Jurassic; UHH 2) nests as a sister to the extant Amia, but shares more traits with the piranha, Serrasalmus).

Figure 3. Dapedium with skull bones colorized and reconstructed using DGS methods.

Figure 3. Dapedium with skull bones colorized and reconstructed using DGS methods.

Amia calva (Linneaus 1766; up to 70cm in length) is the extant bowfin, able to breathe both water and air. Rather than two dorsal fins, an single elongate undulating fin is present. Hatchlings look like tadpoles. The squamosal and quadratojugal are absent. The lacrimal and jugal break apart into several bones. Females produce 2000 to 5000 eggs. Fossil relatives of Amia have a worldwide distribution in fresh and salt waters.

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

FIgure 4. The bowfin, Amia calva, is basal to both the electric eel and halibut in the LRT.

So far,
the LRT (Fig. 5) continues to nest taxa as sisters that share a long list of traits. The character list was never designed for fish, but it still works! The present relationships are often different than traditional taxonomic hypotheses of relationships, especially different from genetic analyses.

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
de Lacepéde BG 1803. Histoire naturelle des poissons. Tome Cinquieme. 5(1-21):1-803 + index.
Leach WE 1822. Dapedium politum. P. 45 in HT de la Beche Remarks on the geology of the south coast of England, from Bridport Harbour, Dorset, to Babbacombe Bay,
Devon. Volume 1, Transactions of the Geological Society of London, Series 2. Geological Society of London, London.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Linneaus C von 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. pp. 1–532. Holmiæ. (Salvius)
Thies D and Hauff RB 2011. A new species of Dapedium Leach, 1822 (Actinopterygii, Neopterygii, Semionnotiformes) from the EArly Jurassic of South Germany. Palaeodiversity 4:185–221.

wiki/Amia
wiki/Xiphias
wiki/Sphyraena
wiki/Piranha
wiki/Serrasalmus
wiki/Dapedium

 

 

 

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