Coccocephalichthys enters the LRT

Today’s post is best understood in pictures
(Figs. 1–3) as a new transitional taxon is added between two previous sisters that were widely separated in time and had distinct morphologies (still, closer to one another than to any other of the 1565+ taxa).

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 1. 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 2. This drawing does not separate the frontals and parietals, or the parietals and postparietals. So scores may change for these.

Coccocephalichthys wildi (originally Coccocephalus wildi Watson 1925; Whitley 1940; Poplin and Véran 1996; Late Carboniferous; Fig. 2) was originally considered a palaeoniscid, like Cheirolepis.

Figure 2. Coccocephalichthys (formerly Coccocephalus) is a Late Carboniferous transitional taxon between Devonian Strunius and Cretaceous Saurichthys.

Figure 2. Coccocephalichthys (formerly Coccocephalus) is a Late Carboniferous transitional taxon between Devonian Strunius and Early Triassic Saurichthys.

In the large reptile tree (LRT, 1569 taxa) Late Carboniferous Coccocephalichthys nests between Late Devonian Strunius (Fig. 1) and Early Triassic Saurichthys (Fig. 3) + Thunnus, the extant tuna. Note the genesis of the long rostrum along with the reduction of the squamosal here. Several bones are re-identified above based on tetrapod homologs.

Figure 1. Saurichthys, shaped like a barracuda, sister to the tuna.

Figure 3. Early Triassic Saurichthys, shaped like a barracuda, sister to the tuna.

Most of the time,
this is how the LRT grows, by adding new transitional taxon between two presently tested taxa. In this case, the transitional taxon neatly helps illustrate the evolution that occurred between the two extremes. Using tetrapod labels (Fig. 2) has proven to help us understand the identity of facial bones in these fish.

Using colors to identify bones
is something I started doing in the vampire pterosaur, Jeholopterus (see header above, far right) in 2003. I was wondering if someone could send me an earlier example of this graphic technique? Today it seems to be growing in popularity, especially so since there are no additional color charges for papers published online.


References
Poplin C and Véran M 1996. A revision of the actinopterygian fish Coccocephalus wildifrom the Upper Carboniferous of Lancashire. In Milner, A. R. (ed.) Studies on Carboniferous and Permian vertebrates. Special Papers in Palaeontology 52: 7-29.
Watson DMS 1925. The structure of certain palæoniscids and the relationships of that group with other bony fish. Proceedings of the Zoological Society of London, 54: 815–870.
Whitley GP 1940. The Nomenclator Zoologicus and some new fish names. Australian Naturalist, 10:241–243.

wiki/Strunius
wiki/Thunnus
wiki/Saurichthys
wiki/Cheirodus
wiki/Mimipiscis
wiki/Coccocephalichthys

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