Figure 8.

Tissue‐specific standardized expression of candidate genes in some vertebrates. Included are data from the African clawed frogs Xenopus laevis/tropicalis, zebrafish Danio rerio, chicken Gallus gallus, and lizard Anolis carolinensis. Highest expression values across these species are found in digestive tract, brain, and head. Note that tissue‐specific gene expression data are incomplete for most species. “Int and Ext Developmental” refer to internal and external “fetal” or “embryonal” tissues which, in absence of more specific information, are summarized under these categories for this manuscript. Synapomorphy—genes expressed in a structure not unambiguously comparable among species, for example, “tadpole” or “beak”