Bone microstructure of bony-toothed birds (Odontopterygiformes) from the Eocene of Ikove, Ukraine: preliminary paleobiological implications

Abstract

ABSTRACT Histological structure of long bones from bony-toothed birds (Odontopterygiformes) from Early Lutetian locality Ikove (Ukraine) is examined for the first time. Six limb bones from Pelagornithidae cf. Dasornis sp. and Lutetodontopteryx tethyensis are described. The bones, although usually being fragmented, show good preservation at the microscopic level. Their microstructure (e.g. orientation and diameter of primary osteons) significantly varies, but the basic pattern and, therefore, the way of growth matches that of recent Neognathae (as well as a number of extinct taxa). In young birds, the periosteum quickly deposited well-vascularised primary bone, which at the same time was resorbed from inside, then the animal reached adult size and fast bone growth gave way to much slower deposition of circumferential layers of lamellar or parallel-fibred tissue on the outer and inner bone surfaces. The bones also underwent Haversian remodelling of various extent (from nearly absent to nearly full), generally stronger in larger bones and in the inner compacta. Bone microstructure is consistent with high metabolic rates, expected in Odontopterygiformes, and implies that their growth rates were comparable to those of recent Neognathae.