Fig. 14.

Sarcopterygii. Schematic illustrations of integumentary elements from various non-tetrapodan aquatic sarcopterygians. (A) Glyptolepis (Dipnomorpha, middle to late Devonian). Scale demonstrating the superposition of multiple odontodes embedded in cellular bone. (B–D) Upper surface of the scales of three species of basal dipnomorphans. (B) Dipterus (late Devonian), (C) Osteolepis (middle Devonian), and (D) Porolepis (early Devonian). Cosmine, consisting of a pore-canal system covered by juxtaposed odontodes composed of dentine and ganoine, is common to many basal dipnomorphans (dipnoans and porolepiforms). (E) Latimeria chalumnae (Actinistia, Extant). As demonstrated by this section through the posterior field, in the coelacanth the scale is of elasmoid type; the upper region is composed of numerous overlapping odontodes, with dentine and ganoine, covering a thick, unmineralized basal plate of elasmodine. Scale bars: A = 250 µm; B = 70 µm; C = 100 µm; D = 140 µm; E = 200 µm.