Fig. 4. Ossification patterns of the carpus and tarsus in five families of the derived salamander suborder Salamandroidea.

In each species of Ambystomatidae (A), Dicamptodontidae (B), Rhyacotritonidae (C), Plethodontidae (D to H), and Salamandridae (I to R), specimens [catalog numbers placed between the carpus (top row) and tarsus (bottom row)] are arranged from left to right to show an increased ossification of the mesopodium (not to scale; dorsal view; color-coded following Fig. 2, with digit II colored in gold to differentiate the preaxial side of the limb). Postaxial dominance is present in the ossification of nondigital arch mesopodials with preaxial column as the last part to ossify. In digital arch mesopodials, preaxial dominance is present in Ambystomatidae (A), Dicamptodontidae (B), and Notophthalmus meridionalis (tarsus only) (L) but is reversed in Plethodontidae (D and F to H) and Salamandridae (K to M and O), where distal carpal/tarsal 4 ossifies earlier than basale commune. Along the proximodistal axis, mesopodials ossify from proximally to distally in most taxa, with a reserved ossification sequence found in the preaxial column of two salamandrids (I and J). Note that species with names colored in cyan have carpus ossified later than tarsus and that species with names colored in red have carpus ossified earlier than tarsus. CAS, California Academy of Sciences; CNAR, National Autonomous University of Mexico; MCZ, Museum of Comparative Zoology; MVZ, Museum of Vertebrate Zoology; NCSM, North Carolina Museum of Natural Sciences; RAN, Ronald Nussbaum Collections at Museum of Zoology; SLU, Southeastern Louisiana University Vertebrate Museum.