title: Bone growth marks reveal protracted growth in New Zealand kiwi (Aves, Apterygidae).
abstract: The presence of bone growth marks reflecting annual rhythms in the cortical bone of non-avian tetrapods is now established as a general phenomenon. In contrast, ornithurines (the theropod group including modern birds and their closest relatives) usually grow rapidly in less than a year, such that no annual rhythms are expressed in bone cortices, except scarce growth marks restricted to the outer cortical layer. So far, cyclical growth in modern birds has been restricted to the Eocene Diatryma, the extant parrot Amazona amazonica and the extinct New Zealand (NZ) moa (Dinornithidae). Here we show the presence of lines of arrested growth in the long bones of the living NZ kiwi (Apteryx spp., Apterygidae). Kiwis take 5-6 years to reach full adult body size, which indicates a delayed maturity and a slow reproductive cycle. Protracted growth probably evolved convergently in moa and kiwi sometime since the Middle Miocene, owing to the severe climatic cooling in the southwest Pacific and the absence of mammalian predators.
authors.affiliation: AMNH, Department of Ornithology, Central Park West at 79th Street, New York, NY 10024, USA. ebourdon@amnh.org
authors.forename: Estelle
authors.initials: E
authors.lastname: Bourdon
authors.forename: Jacques
authors.initials: J
authors.lastname: Castanet
authors.forename: Armand
authors.initials: A
authors.lastname: de Ricqlès
authors.forename: Paul
authors.initials: P
authors.lastname: Scofield
authors.forename: Alan
authors.initials: A
authors.lastname: Tennyson
authors.forename: Hayat
authors.initials: H
authors.lastname: Lamrous
authors.forename: Jorge
authors.initials: J
authors.lastname: Cubo
mesh_terms: D000818:Animals; D001846:Bone Development; D018483:Diaphyses / Q000033:anatomy & histology / Q000254:growth & development; D009520:New Zealand; D046108:Palaeognathae / Q000033:anatomy & histology / Q000254:growth & development*; D013997:Time Factors