The distribution of lobe fins, spiny fins and ray fins
in the large reptile tree (LRT, 1756+ taxa, subset Fig. 1) indicate that each type of fin came and went and sometimes came back again.
So, contra traditional paleontology,
each type of fin does not represent a monophyletic clade. That would be “Pulling a Larry Martin” by setting up clades based on just a few characters.
The LRT provides a more holistic approach,
looking at 238 character traits from nose to toes and letting the software decide without tradition or bias. The LRT documents the multiple evolution of ray fins by convergence.
The basalmost lobefin in the LRT has gone unrecognized until now,
perhaps because Ticinolepis longaeva (Fig. 2) has such a little lobe on its pectoral fin and it is only known from Middle Triassic fossils. Ticinolepis longaeva nests at the base of all lobefins in the LRT (subset Fig. 1) so it would have had a Silurian genesis.
The resemblance of Ticinolepis longaeva to the next most basal lobefin,
Miguashaia (Middle Devonian; Fig. 3) is also instructive. (As a side note, Ticinolepis crassidens nests with Perleidus, not with Ticinolepis longaeva in the LRT, contra López-Arbarello and Sferco 2018).
(López-Arbarello and Sferco 2018; 12cm; Middle Triassic; MCSN 8072) nests at the base of the lobefin fishes. Note the tiny lobe in the middle of the ray fin. Compare that pectoral fin to the one in figure 3.
(Schultze 1973, Cloutier 1996; Middle Devonian; 45cm) was considered the sister group (outgroup) of the Actinista (coelocanths). Notably Miguashaia reverses to a heterocercal tail. That’s why it looks a little odd. The dentary is short and the teeth are small.
Final notes to be covered in more detail later:
Basal pectoral fins are rather inflexible and extend horizontally (Fig. 4). Ratfish hold their pectoral fins vertically, against the torso. Iniopterygians raise the pectoral fin to the dorsal margin. Moray eels lose their fins. So there is more variety here yet to explore.
López-Arbarello A and Sferco E 2018. Neopterygian phylogeny: the merger assay. Royal Society open sci. 5: 172337. http://dx.doi.org/10.1098/rsos.172337
Schultze H-P 1973. Crossopterygier mi heterozerker Schwanzfloss aus dem Oberdevon Kanadas, nebst einer Beschreibung von Onychodontida-Resten aus dem Middledevon Spaniens und aus dem Karbon der USA. Palaeontograhica A 143:188–208.