Novel spiny shark-to-bony fish transition series

Slogging through the process
of modeling actual evolutionary events with trait analysis, the LRT appears to present a novel hypothesis of interrelationships linking certain spiny sharks, Early Devonian 3cm long Mesacanthus and Early Devonian, 5.2cm Triazeugacanthus (Fig 1) with that clade of basal bony fish derived from placoderms.

Of course, this hypothesis needs testing by independent workers.
At present, this hypothesis of very fragile.

Figure 1. Two spiny sharks, Mesacanthus and Triazeugacanthus, now appear to be basal to Triassic bony fish close to Amia, the extant bowfin, illustrated here in phylogenetic order. ” data-image-caption=”

Figure 1. Two spiny sharks, Mesacanthus and Triazeugacanthus, now appear to be basal to Triassic bony fish close to Amia, the extant bowfin, illustrated here in phylogenetic order.

” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=78″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=265″ class=”size-full wp-image-85420″ src=”https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=584&h=2256″ alt=”Figure 1. Two spiny sharks, Mesacanthus and Triazeugacanthus, now appear to be basal to Triassic bony fish close to Amia, the extant bowfin, illustrated here in phylogenetic order.” width=”584″ height=”2256″ srcset=”https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=584&h=2256 584w, https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=39&h=150 39w, https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg?w=78&h=300 78w, https://pterosaurheresies.files.wordpress.com/2024/04/hulettia_diagram588-1.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Figure 1. Two spiny sharks, Mesacanthus and Triazeugacanthus, now appear to be basal to Triassic bony fish close to Amia, the extant bowfin, illustrated here in phylogenetic order.

Nothing is ever settled here,
but revisiting and revising Triazeugacanthus based on a new Bauplan, seems to be shedding new light on this novel hypothesis of interrelationships.

Note the origin of
more less similar fin rays in both the pectoral and pelvic fins from the more primitive morphology in which the leading edge of a pectoral and pelvic fin were both spines. In the transitional taxon, Hulettia (Fig 1), the leading edge ray is more robust than the other rays.

If you want to remind me that catfish have a similar pectoral fin with a robust leading ray, you are correct. In the LRT catfish are closely related to this series of taxa.

Triazeugacanthus affinis
(Miles 1966; Chevrinais, Sire and Cloutier 2017, Early Devonian; 380 mya; up to 5.2cm) is a small acanthodian basal to ray-fin fish not in the clade that produced tetrapods. That clade includes Prohalecites and Hulettia at its base.

References
Chevrinais M, Sire, J-Y and Cloutier R 2017. From body scale ontogeny to species ontogeny: Histological and morphological assessment of the Late Devonian acanthodian Triazeugacanthus affinis from Miguasha, Canada. PLOS ONE. 12 (4): e0174655. Bibcode:2017PLoSO..1274655C. doi:10.1371/journal.pone.0174655
Miles RS 1966. The acanthodian fishes of the Devonian Plattenkalk of the Paffrath. Trough in the Rhineland. Arkiv för Zoologica (Stockholm)18: 147–194.

wiki/Mesacanthus
wiki/Triazeugacanthus
wiki/Hulettia