the specifics of the fossil record. The first passerines are now thought to have evolved in Gondwana (in the Southern Hemisphere) in the late Paleocene or early Eocene, around 50 million years ago. The initial split was between the New Zealand wrens (Acanthisittidae) and all other passerines (Eupasserine), and the second split involved the Tyranni (suboscines) and the Passeri (oscines or songbirds). A rupture of the Gondwanan continent caused the core split of the Eupasseres, which were divided into these groups, one in Western Gondwana (Tyranni) and the other in Eastern Gondwana (Passeri). Passeri experienced a great radiation of forms out of the Australian continent. A major branch of the Passeri, parvorder Passerida, expanded deep into Eurasia and Africa, where a further explosive radiation of new lineages occurred. This eventually led to three major Passerida lineages comprising about 4,000 species, which in addition to the Corvida and numerous minor lineages make up songbird diversity today. Extensive biogeographical mixing happens, with northern forms returning to the south, southern forms moving north, and so on. Fossil record Earliest passerines Perching bird osteology, especially of the limb bones, is rather diagnostic. However, the early fossil record is poor because the first Passeriformes were relatively small, and their delicate bones did not preserve well. Queensland Museum specimens F20688 (carpometacarpus) and F24685 (tibiotarsus) from Murgon, Queensland, are fossil bone fragments initially assigned to Passeriformes. However, the material is too fragmentary and their affinities have been questioned. Several more recent fossils from the Oligocene of Europe, such as Wieslochia, Jamna, Resoviaornis and Crosnoornis, are more complete and definitely represent early passeriforms, although their exact position in the evolutionary tree is not known. From the Bathans Formation at the Manuherikia River in Otago, New Zealand, MNZ S42815 (a distal right tarsometatarsus of a tui-sized bird) and several bones of at least one species of saddleback-sized bird have recently been described. These date from the Early to Middle Miocene (Awamoan to Lillburnian, 19–16 mya). Early European passerines In Europe, perching birds are not too uncommon in the fossil record from the Oligocene onward, but most are too fragmentary for a more definite placement: Wieslochia (Early Oligocene of Frauenweiler, Germany) Resoviaornis (Early Oligocene of Wola Rafałowska, Poland) Jamna (Early Oligocene of Jamna Dolna, Poland) Winnicavis (Early Oligocene of Lower Silesian Voivodeship, Poland) Crosnoornis (Early Oligocene of Poland) Passeriformes gen. et sp. indet. (Early Oligocene of Luberon, France) – suboscine