Figure 1
Phylogenetic distribution of dermal odontodes in vertebrates. (A) Simplified cladogram of the distribution of dermal odontode in vertebrates evolution3,4,9,28. Asterisk indicates the extinct lineages. Dermal odontodes (black) ornament whole body surface of some extinct jawless (Pteraspidomorphi) and jawed fish (placodermi), and chondrichthyans. The stem-group of actinopterygii and sarcopterygii possessed odonotode-like structure in their scales, called ganoine scales and cosmoid scales, respectively. Owing to the stem-group teleostei lost the dermal odontodes, almost no catfish species (Siluriformes) possess the dermal odontodes. While Loricarioidei show regains of dermal odontodes in their evolutionary history. Bone staining pictures and HE-stained transverse sections show the formation of dermal bones in the representative Siluroidei (Ictalurus punctatus, TL: 5 cm, bottom, n = 2) and Loricarioidei (Ancistrus sp., TL: 6 cm, top, n = 2). Black and gray boxes indicate gain and loss of dermal odontodes, respectively. CD cranial denticle, DBP dermal bony plate, SB skull bone.
