In Australia,ratites(Aves:Palaeognathae)are represented in the extant fauna by the family Casuariidae with 1 species of emu Dromaius novaehollandiae and 1 cassowary Casuarius casuarius.The Australian fossil re-cord re...In Australia,ratites(Aves:Palaeognathae)are represented in the extant fauna by the family Casuariidae with 1 species of emu Dromaius novaehollandiae and 1 cassowary Casuarius casuarius.The Australian fossil re-cord reveals no other extinct ratite families but there are a number of other casuariid species.Most significant of these,due to its Oligo-Miocene age and because it is known from abundant material,is Emuarius gidju.Here,we describe additional material and confirm that the taxon had a temporal range of Late Oligocene to Mid-dle Miocene(approximately 24-15 Ma).We reveal new morphological details,including notably that the spe-cies had relatively much smaller eyes than D.novaehollandiae,in addition to a less well-developed cursori-al ability,as inferred from its pelvic limb.In these respects,Emuarius is similar to Casuarius and suggest that it was adapted to denser vegetation than the open woodlands and grasslands that characterise much of Austra-lia today and to which D.novaehollandiae,with its large eyes and enhanced cursorial ability,is strongly adapt-ed.Emuarius was compared to and found to be distinct from the poorly provenanced Australian fossil species C.lydekkeri.We conducted a phylogenetic analysis of morphological data that robustly shows that E.gidju is the sister taxon of Dromaius and together these taxa form a clade that is sister to Casuarius.This indicates that the evolution towards enhanced cursorality that characterises Dromaius took place after the divergence of the emu-cassowary lineages and was likely not the driving mechanism of this divergence.Comparisons between D.no-vaehollandiae and D.baudinianus revealed no qualitative skeletal differences and we suggest that the latter tax-on is best considered to be an island dwarf that should be taxonomically recognized at a subspecific level only.展开更多
文摘In Australia,ratites(Aves:Palaeognathae)are represented in the extant fauna by the family Casuariidae with 1 species of emu Dromaius novaehollandiae and 1 cassowary Casuarius casuarius.The Australian fossil re-cord reveals no other extinct ratite families but there are a number of other casuariid species.Most significant of these,due to its Oligo-Miocene age and because it is known from abundant material,is Emuarius gidju.Here,we describe additional material and confirm that the taxon had a temporal range of Late Oligocene to Mid-dle Miocene(approximately 24-15 Ma).We reveal new morphological details,including notably that the spe-cies had relatively much smaller eyes than D.novaehollandiae,in addition to a less well-developed cursori-al ability,as inferred from its pelvic limb.In these respects,Emuarius is similar to Casuarius and suggest that it was adapted to denser vegetation than the open woodlands and grasslands that characterise much of Austra-lia today and to which D.novaehollandiae,with its large eyes and enhanced cursorial ability,is strongly adapt-ed.Emuarius was compared to and found to be distinct from the poorly provenanced Australian fossil species C.lydekkeri.We conducted a phylogenetic analysis of morphological data that robustly shows that E.gidju is the sister taxon of Dromaius and together these taxa form a clade that is sister to Casuarius.This indicates that the evolution towards enhanced cursorality that characterises Dromaius took place after the divergence of the emu-cassowary lineages and was likely not the driving mechanism of this divergence.Comparisons between D.no-vaehollandiae and D.baudinianus revealed no qualitative skeletal differences and we suggest that the latter tax-on is best considered to be an island dwarf that should be taxonomically recognized at a subspecific level only.
