gray bichir

description

This description was done with a complete series of 10 finlets for an adult male Polypterus senegalus of 260 mm TL and with additional comparative observations of other specimens. We observe an anterior-posterior gradient of spine height in Polypterus senegalus as for all the Polypterus species, though with a difference in largest to smallest spine height ratio (Fig. 8). Even if finlet differentiation is posterior-anterior oriented, the shape of the posterior spine, generated first, is more similar to the first lepidotrichium at the second part of the dorsal fin than to the anterior spines, i. e. more bent at its lower third versus larger for the most anterior spines (Fig. 8: S 10). In transverse section, the shaft of the first spine shows a nearly straight anterior margin (Fig. 7 B), even though it is more or less rounded for distal sections (Fig. 7 C-I) as it is for the posterior spines. The anterior face of the finlet shaft is covered by a thin continuous ganoine layer (Fig. 3 B-E). It runs over the articular head downward to about its mid-height, ending at the superior transversal pad (Fig. 3 D, E). The transversal pad forms two anterior upper processes directly connected to th

Comparative morphology of the finlet spines of the extant Polypteridae (Osteichthyes; Cladistia). Systematic interest