Two 2020 papers on coelacanth fish phylogeny
(see References) both followed tradition and considered the Actinistia (the coelacanths), a subset of the Sarcopterygii, the lobe fins that led to Tetrapoda. This is what every textbook teaches. This is accepted, entrenched tradition.
Figure 1. Top: Gavinia after DGS reconstruction. Middle: Gavinia insitu from Long 1999, colors added here. Bottom: Freehand restoration of Gavinia from Long 1999, colors added here.
Middle Devonian Gavinia (Long 1999)
(Figs 1,2) is considered the basalmost coelacanth. It is represented by a single roadkill specimen with a heterocercal tail. Other coelacanths have a posterior caudal lobe, a strong character of the clade. Long 1999 provided a freehand sketch of Gavinia syntrips (Fig 1) along with a precise drawing of the skull and tail insitu.
Unfortunately, the middle portion was not preserved.
Figure 2. Actinistia origins and phylogeny. The outgroup here is Parasemionotus and basal taxa are not lobefins.
Here
DGS was applied to the insitu roadkill (Fig 1), then used that to reconstruct what remained of the lateral face of Gavinia (Fig 1). A minimum of freehand was used to restore missing parts. Some parts duplicated Long’s freehand drawing. Others were different.
Based on tested taxa,
the LRT more or less duplicated traditional phylogenies – except for the origin of the clade. Note the tiny taxa, Parasemionotus and Luganoia, at the origin of the coelacanths, duplicating the phylogenetic miniaturization that attends the genesis of many other clades in the LRT.
Figure 3. The giant coelacanth, Sanfrancisana, shown here to scale with a human.
In the Mesozoic of North Africa
Sanfranciscana (Fig 3) grew several times larger than a human. starting with tiny ancestor, Luganoia (Fig 1), no larger than a human little finger.
References
Long J 1999. A new genus of fossil coelacanth (Osteichthyes: Coelacanthiformes) from the Middle Devonian of southeastern Australia. Records of the Western Australian Museum Supplement 57:37–53.
Mondéjar-Fernández J, et al (4 co-authors) 2020. A microanatomical and histological study of the scales of the Devonian sarcopterygian Miguashaia bureaui and the evolution of the squamation in coelacanths. Journal of Anatomy DOI: 10.1111/joa.13428
Toriño P, Soto M and Perea D 2020. A comprehensive phylogenetic analysis of coelacanth fishes (Sarcopterygii, Actinistia) with comments on the composition of the Mawsoniidae and Latimeriidae: Evaluating old and new methodological challenges and constraints. Historical Biology 33(12): 3423–3443
https://doi.org/10.1080/08912963.2020.1867982
The Pterosaur Heresies 