| Deep continuous layers of iridophores were discovered in certain Asian Agkistrodon species. A survey of available snakes showed the banded iridophores to be present in North American Crotalus and Sistrurus also, indicating an unreported morphology to be a possible common phenomenon.;Reflectometry of four selected crotalids reveals positive correlation between iridophore quantities and albedo, but habitat adaptation and correlation of individual species/subspecies is difficult to show and only subjectively suggested. Published phylogenies of the species of the genera Agkistrodon, Calloselasma, Deinagkistrodon and Hypnale are revised to reflect taxonomic works and are correlated with iridophore pattern data. Phylogenetic relationships of Crotalus and Sistrurus are also revised with recent publications; they are neither supported nor contradicted because layered iridophores occur in all of their phylogenetic groups.;Skin samples from 147 species and/or subspecies of snakes of the families Leptotyphlopidae, Boidae, Colubridae, Elapidae and Viperidae were examined and photographed by polarized light microscopy. Dermal iridophore patterns were visually identified and categorized as (1) isolated cells, (2) lightly layered, (3) moderately layered and (4) heavily layered. Selected specimens were examined and photographed by electron microscopy; isolated iridophore ultrastructure and layered iridophore ultrastructure patterns are illustrated and described. |
