Connecting the thigh and foot: resolving the association of post-cranial elements in the species of Ilbandornis (Aves: Dromornithidae).

Worthy, T.H. & Yates, A., 27.3.2015. Connecting the thigh and foot: resolving the association of post-cranial elements in the species of Ilbandornis (Aves: Dromornithidae). Alcheringa 39, xxx–xxx. ISSN 0311-5518 Fossils of the two mid-sized dromornithid species classified in Ilbandornis are re-examined. A study of the large series of fossils from the late Miocene (ca 9–7 Ma) Alcoota Local Fauna shows that the holotypes of Ilbandornis woodburnei Rich and Ilbandornis lawsoni Rich, a femur and a tarsometatarsus, respectively, pertain to separate taxa. However, the femora and tibiotarsi of these species have been confused in the past. We provide qualitative descriptions and morphometrics to discriminate the limb bones, which overlap in absolute size. Ilbandornis woodburnei is characterized by short tarsometatarsi, tibiotarsi with relatively broad distal ends, and femora with a broad sulcus patellaris. In contrast, I. lawsoni has very elongate tarsometatarsi, slender tibiotarsi with relatively narrow distal ends, and femora with a narrow sulcus patellaris. Two morphotypes of the proximal pedal phalanges are present in the Alcoota LF. These manifest overlapping length ranges but are distinguished by relative robustness and other details of shape. For each phalanx II.1, III.1 and IV.1, those referred to I. lawsoni are more slender than those referred to I. woodburnei, with, for example, the trochlea articularis of II.1 and the proximal width of III.1 as a proportion of length, both more transversely compressed. Examination of the dromornithids from the middle Miocene Bullock Creek Local Fauna (ca 15–12 Ma), previously referred to? Bullockornis sp., and the late Miocene Ongeva LF (ca 7–6 Ma) reveals that two species of Ilbandornis are present in each fauna. On available data, these are indistinguishable from I. lawsoni and I. woodburnei, attesting to the continuity of these lineages minimally from 12 Ma to 7 Ma in parallel with a Dromornis lineage. Trevor H. Worthy [[email protected]], School of Biological Sciences, Flinders University, GPO 2100, Adelaide 5001, SA, Australia; Adam Yates [[email protected]], Museum of Central Australia, PO Box 831, Alice Springs, Northern Territory 0871, Australia.