Triassic Pholidophorus nests with Devonian Strunius

This is another overlooked relationship
assisted by a relabeling of fish skull bones using tetrapod names (Fig. 1).

Figure 1. Pholidophorus in situ + two skull drawings relabeled with tetrapod names.

Figure 1. Pholidophorus in situ + two skull drawings relabeled with tetrapod names.

Pholidophorus sp. (Agassiz 1832; Middle-Late Triassic; 40cm long) was a herring-like fish with primitive ganoid scales and poorly ossified spine. Traditionally considered an early teleost, with large eyes, here it nests with Late Devonian Strunius, but lacks the central process of the tail. Here the skull bones are re-identified with tetrapod labels. The pectoral and pelvic fins were similar in size.

Figure 2. Strunius skull enlarged to show detail. Inset shows the second origin of the dual external naris as the original apparently splits by the addition of a skin bridge creating two openings. Compare to figure 1.

Figure 2. Strunius skull enlarged to show detail. Inset shows the second origin of the dual external naris as the original apparently splits by the addition of a skin bridge creating two openings. Compare to figure 1.

Strunius rolandi (Jessen 1966; originally Glyptomus rolandi Gross 1956; 10 cm in length; Late Devonian) was considered a lobe-fin fish with ray fins. Here it nests with Cheirolepis, a traditional and transitional ray fin fish. The origin of the double naris in this lineage appears here as a split dividing the original single in two. The palate and possible choana are not known.

Figure 4. Subset of the LRT focusing on fish. Note the traditional members of the Holostei do not nest together here largely because they don't look alike, but more like other, more attractive taxa.

Figure 3. Subset of the LRT focusing on fish. Note the traditional members of the Holostei do not nest together here largely because they don’t look alike, but more like other, more attractive taxa.


References
Agassiz L 1832. Untersuchungen über die fossilen Fische der Lias-Formation. Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde, 3, 139–149.
Agassiz JLR 1835. Recherches sur les Poissons fossiles, 5 volumes. Imprimerie de Petitpierre et Prince, Neuchaatel, 1420 pp.
Agassiz JLR 1835. On the fossil fishes of Scotland. Report of the British Association for the Advancement of Science, British Association for the Advancement of Science, Edinburgh.

wiki/Strunius
wiki/Pholidophorus

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