sandersi can further be differentiated from Pelagornis ( Osteodontornis) orri by the presence of two (vs. sandersi can be differentiated from other species of Pelagornis by the slender caudal portion of the mandible, the more elongate beak, a larger number of mandibular pseudoteeth (31 vs. sandersi exhibits diagnostic characteristics of Pelagornis ( 10), including rostrum with transverse furrow, tricipital fossa situated on the ventral surface of humerus, and tibiotarsus with medial condyle markedly more anteriorly projected than lateral condyle.

cc, Lateral cnemial crest fac, fossa aditus canalis neurovascularis fc, facet haf, humeral articular facet ie, intercotylar eminence j, jugal lf, lateral furrow mtII, metatarsal trochlea II nfh, nasofrontal hinge pf, pneumatic foramen pp, paroccipital process sf, subcondylar fossa sup, supra-angulare sw, swelling on crista deltopectoralis syn, synovial joint tb, tubercle trf, transverse furrow.

Tarsometatarsus in (o) dorsal view (distal portion exposed in the medial view because of deformation) and (p) rotated to show the distal portion in dorsal view. Tibiotarsus in (l) cranial and (m) caudal views. (i) Partial furcula femur in (j) cranial and (k) caudal views. Scapula in (g) lateral and (h) medial views. Right humerus in (e) caudal and (f) cranial views. sandersi holotype (ChM PV4768) skull in (a) dorsal, (b) ventral, (c) left lateral (mandible in medial view), and (d) right lateral views (mandible in lateral view). exulans (Royal Albatross 3-m average wingspan) for scale. sandersi (elements preserved in the holotype are shown in white) with D. Given the challenges of flight at large size, there has been much debate over potential upper size limits for different styles of flight in vertebrates ( 1, 2, 11вЂ“ 13), and the evolution of specialized taxa, like teratorns and pelagornithids, has been tied to environmental factors, such as wind patterns ( 6, 14вЂ“ 16).ДЇig. In the past, the extinct terrestrial teratorn Argentavis magnificens ( 6) and the extinct soaring Pelagornithidae ( 7вЂ“ 10) greatly exceeded these sizes. Today, the largest directly measured wild individuals of volant birds reach wingspans of в€ј3.5 m (Royal Albatross Diomedea exulans) and masses of в€ј19 kg (Great Bustard Otis tarda and Kori Bustard Ardeotis kori) ( 5). Over their в€ј150-My history, birds evolved to span at least four orders of magnitude in size ( 2) and achieve a wide variety of flight styles, such a flap-gliding, soaring, and hovering. Flight ability in birds is largely governed by scaling effects, leading to a tradeoff between the benefits of physiological efficiencies and the drawbacks of decreasing power margin (ratio of available muscle power to required mechanical power) as size increases ( 1вЂ“ 4).

Bird with largest wingspan