Bone histology in extant and fossil penguins (Aves: Sphenisciformes)

Substantial changes in bone histology accompany the secondary adaptation to life in the water. This transition is well documented in several lineages of mammals and non‐avian reptiles, but has received relatively little attention in birds. This study presents new observations on the long bone microstructure of penguins, based on histological sections from two extant taxa ( Spheniscus and Aptenodytes ) and eight fossil specimens belonging to stem...