Bone microstructure of Vegavis iaai (Aves, Anseriformes) from the Upper Cretaceous of Vega Island, Antarctic Peninsula

GARCÍA MARSÀ, JORDI; AGNOLIN, FEDERICO; NOVAS, FERNANDO

Historical Biology

Taylor and Francis

Año: 2017

Vegavis iaai is a neornithine bird coming from the Late Cretaceous Sandwich Bluff Member of the Lópezde Bertodano Formation (Maastrichtian), Antarctic Peninsula. Vegavis constitutes the only unquestionableCretaceous neornithine bird, and is known by the holotype and specimen MACN-PV 19.748. The goal ofthis paper is to present a detailed osteohistological analysis of V. iaai. Vegavis shows a highly vascularizedfibrolamellar matrix lacking lines of arrested growths, features widespread among modern birds. This isconsistent with previous hypotheses indicating that modern birds were dominant at high latitudes. This isprobably related to high-metabolic rates shared by modern birds, whereas archaic taxa as Enantiornithesare absent or form a minority part of High-Latitude bird assemblages. Vegavis was a diver, characterisedby a certain degree of limb osteosclerosis, with an increase of bone inner compactness, and inhibition ofsecondary remodelling, with no effect on the external dimensions of the bone, a combination of charactersrelated to diving lifestyle. Based on Relative Bone Thickness it is possible to infer that Vegavis was a footpropelleddiving bird, similar to some extant anseriforms. Occurrence of osteosclerotic limb bones inVegavis and Polarornis may constitute a derived shared feature, sustaining the hypothesis that both taxaare phylogenetically related.