Shoshonia arctopteryx gen. et sp. nov., an early coelacanth that preserves the oldest and most primitive paired fin skeleton known for that group. (A) Holotype (FMNH PF 15327) showing right flank scales and pectoral fin. Regions of the fish preserved in this specimen indicated by red area highlighted in hypothetical reconstruction. (B) Positive cast of the pectoral fin, including endoskeletal and dermal components. Fin endoskeleton has been false-color tinted for clarity. (C) Interpretive drawing of the pectoral fin endoskeleton. Abbreviations: l.sc, scales covering central lobe of pectoral fin; mes.III, mesomere three; mes.IV, mesomere four; mes.V, mesomere five; pr.v, ventral process of the mesomere; r.dst, distal radial; r.pst, postaxial radial; r.pre, preaxial radial.
Fig. 4. The evolution of pectoral appendages in early sarcopterygian fishes. Simplified cladogram adapted from that in Fig. 3 showing the distribution of major changes in pectoral appendage pattern in sarcopterygian fishes. This diagram encompasses the early diversity of pectoral appendages within crown-clade Sarcopterygii, and also illustrates selected patterns in proximal outgroups. Many previous depictions of sarcopterygian fin evolution (Coates et al. 2002; Long et al. 2006; Shubin et al. 2006) have been confined to the dipnomorph/tetrapodomorph clade, giving the misleading impression that the conditions found in dipnomorphs might be generalized. Bars representing character changes are color coded to indicate the aspects of morphology to which they refer, while the lengths of branches are scaled to the number of unambiguous character changes occurring along them. A key for these character changes is provided in supplementary material. Few changes separate Shoshonia and ‘osteolepiform’-grade tetrapodomorphs such as Gogonasus, Rhizodopsis, and Eusthenopteron from the base of Sarcopterygii as well as actinopterygian and acanthodian outgroups, but Latimeria and dipnomorphs are highly apomorphic, with many of their specializations arising in parallel.
First discovery of a primitive coelacanth fin fills a major gap in the evolution of lobed fins and limbs. Matt Friedman1,Michael I. Coates, Philip Anderson. Evolution & Development Volume 9, Issue 4, pages 329–337, July/August 2007 (pdf)