Bone tissue histology of the Early Cretaceous bird Yanornis: evidence for a diphyletic origin of modern avian growth strategies within Ornithuromorpha

We present the first description of the bone microstructure of the ornithuromorph bird Yanornis from the Early Cretaceous Jehol ornithofauna. Yanornis is a derived member of independent ornithuromorphan clade, itself the sister group to the clade including Iteravis and ornithurans (including modern birds). We demonstrate that Yanornis grew continuously and probably was fully grown within the first or second year of life. No growth marks...