Three terrestrial Pleistocene coucals (Centropus: Cuculidae) from southern Australia: biogeographical and ecological significance

The skeleton of Congruus kitcheneri, a semiarboreal kangaroo from the Pleistocene of southern Australia

The macropodine kangaroo, Wallabia kitcheneri, was first described in 1989 from a Pleistocene deposit within Mammoth Cave, southwestern Australia, on the basis of a few partial dentaries and maxilla fragments. Here, we recognize W. kitcheneri within the Pleistocene assemblages of the Thylacoleo Caves, south-central Australia, where it is represented by several cranial specimens and two near-complete skeletons, a probable male and female. We reallocate this species to the hitherto monotypic genus Congruus. Congruus kitcheneri differs from all other macropodid species by having a highly unusual pocket within the wall of the nasal cavity. It is distinguished from C. congruus by having a longer, narrower rostrum, a taller occiput and a deeper jugal. Congruus is closest to Protemnodon in overall cranial morphology but is smaller and less robust. In most postcranial attributes, Congruus also resembles Protemnodon, including general limb robustness and the atypical ratio of 14 thoracic to five lumbar vertebrae. It is distinguished by the high mobility of its glenohumeral joints, the development of muscle attachment sites for strong adduction and mobility of the forelimb, and large, robust manual and pedal digits with strongly recurved distal phalanges. These adaptations resemble those of tree-kangaroos more than ground-dwelling macropodines. We interpret this to imply that C. kitcheneri was semiarboreal, with a propensity to climb and move slowly through trees. This is the first evidence for the secondary adoption of a climbing habit within crown macropodines.

Postcranial Skeletal Pneumaticity in Cuculidae

Postcranial skeletal pneumaticity (i.e., epithelial-lined, air-filled bones) is a condition unique to birds among extant tetrapods. Previous research reveals extensive variation in the expression of this trait in different bird species, from taxa that pneumatize nearly the entire skeleton to others that do not pneumatize a single bone. These studies, however, have primarily focused on aquatic/semi-aquatic birds, specifically Anseriformes (screamers, ducks, geese, swans) and Aequorlitornithes (loons, gulls, penguins, storks, etc.). This is the first clade-centric study of pneumaticity in an exclusively terrestrial clade (i.e., a group without any proclivities for water), Cuculidae. Given the variation in body size and ecology exhibited by cuckoos, they represent an ideal group for evaluating previously established trends in pneumaticity patterns. Similar to previous studies, our results indicate that cuckoos do exhibit extensive postcranial skeletal pneumaticity but with much more limited variation in expression. Of the surveyed species, 30 of 41 display an identical expression pattern, pneumatizing all postaxial vertebrae, the humerus, sternum, and pelvic girdle. The remaining species (11/41) deviate from this pattern by no more than two elements (i.e., the femur or the scapula/coracoid). All variable species expand upon the basic cuckoo pattern, with five species pneumatizing the femur and the remaining six taxa pneumatizing both the scapula and coracoid. Furthermore, most variation occurs in early diverging clades, with distinct subclades associated with specific anatomical expansions in pneumaticity (e.g., pneumatic femora in Neomorphinae and pneumatic scapulae/coracoids in select members of Couinae and Centropodinae). Limited variation noted in Cuculidae may be the result of the relatively high base level of pneumaticity when compared with previously sampled groups of water-oriented birds. Additional analyses indicate a positive relationship between body mass and pneumaticity, with possible (i.e., non-quantifiable) relationships noted between the limited expansions from the basic cuckoo pattern and specific locomotor behaviors (e.g., pneumatic femora present in species with enhanced cursorial behavior). These basic trends have also been observed in other densely sampled neognath clades. Taken together, the data presented herein supports the hypothesis that changes in pneumaticity expression may be correlated with shifts in biomechanical loading regimes rather than solely as a weight saving (i.e., density-altering) mechanism.

Mitogenomic evidence of close relationships between New Zealand's extinct giant raptors and small-sized Australian sister-taxa

Prior to human arrival in the 13th century, two large birds of prey were the top predators in New Zealand. In the absence of non-volant mammals, the extinct Haast's eagle (Hieraaetus moorei), the largest eagle in the world, and the extinct Eyles' harrier (Circus teauteensis) the largest harrier in the world, had filled ecological niches that are on other landmasses occupied by animals such as large cats or canines. The evolutionary and biogeographic history of these island giants has long been a mystery. Here we reconstruct the origin and evolution of New Zealand's giant raptors using complete mitochondrial genome data. We show that both Eyles' harrier and Haast's eagle diverged from much smaller, open land adapted Australasian relatives in the late Pliocene to early Pleistocene. These events coincided with the development of open habitat in the previously densely forested islands of New Zealand. Our study provides evidence of rapid evolution of island gigantism in New Zealand's extinct birds of prey. Early Pleistocene climate and environmental changes were likely to have triggered the establishment of Australian raptors into New Zealand. Our results shed light on the evolution of two of the most impressive cases of island gigantism in the world.

Taxonomic review of the late Cenozoic megapodes (Galliformes: Megapodiidae) of Australia

Megapodes are unusual galliform birds that use passive heat sources to incubate their eggs. Evolutionary relationships of extant megapode taxa have become clearer with the advent of molecular analyses, but the systematics of large, extinct forms (Progura gallinacea, Progura naracoortensis) from the late Cenozoic of Australia has been a source of confusion. It was recently suggested that the two species of Progura were synonymous, and that this taxon dwarfed into the extant malleefowl Leipoa ocellata in the Late Pleistocene. Here, we review previously described fossils along with newly discovered material from several localities, and present a substantial taxonomic revision. We show that P. gallinacea and P. naracoortensis are generically distinct, describe two new species of megapode from the Thylacoleo Caves of south-central Australia, and a new genus from Curramulka Quarry in southern Australia. We also show that L. ocellata was contemporaneous with larger species. Our phylogenetic analysis places four extinct taxa in a derived clade with the extant Australo-Papuan brush-turkeys Talegalla fuscirostris, L. ocellata, Alectura lathami and Aepypodius bruijnii. Therefore, diversity of brush-turkeys halved during the Quaternary, matching extinction rates of scrubfowl in the Pacific. Unlike extant brush-turkeys, all the extinct taxa appear to have been burrow-nesters.