Alan Feduccia

Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China

Late Jurassic and Early Cretaceous birds from northeastern China, including many complete skeletons of Confuciusornis, provide evidence for a fundamental dichotomy in the class Aves that may antedate the temporal occurrence of the Late Jurassic Archaeopteryx. The abundance of Confuciusornis may provide evidence of avian social behavior. Jurassic skeletal remains of an ornithurine bird lend further support to the idea of an early separation of the line that gave rise to modern birds. Chaoyangia, an ornithurine bird from the Early Cretaceous of China, has premaxillary teeth.

‘Big bang’ for tertiary birds?

Abstract The early evolution of living birds has been sharply debated, with two disparate interpretations. Molecular-clock studies consistently date the emergence of modern bird orders at ∼100 million years ago or older, coincidental with major continental breakup. This is supported by some biogeographers who use phylogenetics, accept an ancient evolutionary origin and use historical geology to guide their reasoning. The fossil record, however, provides evidence that modern birds represent an explosive Tertiary radiation, following the Cretaceous–Tertiary cataclysm, and their origins are almost 50 million years younger than that predicted by molecular studies. Here, I argue that this explosive, punctuated model conforms to the typical pattern of vertebrate evolution characterized by rapid diversification following a major extinction event.

EVIDENCE FROM CLAW GEOMETRY INDICATING ARBOREAL HABITS OF ARCHAEOPTERYX

The Late Jurassic Archaeopteryx has been thought to have been a feathered predator adapted to running that represented a terrestrial stage in the evolution of true birds from coelurosaurian dinosaurs. Examination of claw geometry, however, shows that (i) modern ground- and tree-dwelling birds can be distinguished on the basis of claw curvature, in that greater claw arcs characterize tree-dwellers and trunk-climbers, and (ii) the claws of the pes (hind foot) and manus (front hand) of Archaeopteryx exhibit degrees of curvature typical of perching and trunk-climbing birds, respectively. On this basis, Archaeopteryx appears to have been a perching bird, not a cursorial predator.

Feathers of Archaeopteryx: Asymmetric Vanes Indicate Aerodynamic Function

Vanes in the primary flight feathers of Archaeopteryx conform to the asymmetric pattern in modern flying birds. The asymmetry has aerodynamic functions and can be assumed to have evolved in the selective context of flight.

A diapsid skull in a new species of the primitive bird Confuciusornis

Since the description of Confuciusornis (the oldest beaked bird) in1995, based on three partial specimens, large numbers of complete skeletons have been recovered,. Most new material of Confuciusornis, can be assigned to a single sexually dimorphic species, C. sanctus . Here we report a new species based on a remarkably well preserved skeleton with feathers and, for the first time in the Mesozoic record, direct evidence of the shape of a horny beak. It has a complete and large preserved postorbital that has a broad contact with the jugal bone. This character is presently only known in Confuciusornis, and may confirm previous suggestions of a postorbital in Archaeopteryx. The squamosal is in tight contact with the postorbital. These two bones form an arch dividing the upper and lower temporal fenestrae, as in other diapsid reptiles. The presence of a typical diapsid cheek region with two openings in Confuciusornis may preclude the presence of prokinesis (upper jaw mobility against the braincase and orbital area), a feeding adaptation found in most modern birds. The presence of a horny beak, characteristic of modern birds, coupled with a primitive temporal region provides new evidence for a mosaic pattern in the early evolution of birds.

SEXUAL DIMORPHISM IN SKATES (RAJIDAE) AND ITS POSSIBLE ROLE IN DIFFERENTIAL NICHE UTILIZATION

Adaptive radiation has been thought of generally as evolutionary divergence of species or higher taxonomic categories into differing zones or niches. Evidence is now accumulating to indicate that a lesser degree of adaptive radiation may also occur within animal populations, so that individuals may came to occupy different subniches or subzones (see Selander, 1966 and 1969, for a more complete discussion of this topic). When individuals within a population come to occupy differing subniches or adaptive subzones, the total niche of the species may be partitioned or even expanded in cases where the environmental situation will allow. Thus in many organisms sexual dimorphism may arise and result in a differential niche utilization by the sexes, which in turn may result in decreased intraspecific competition for food. The role of sexual dimorphism in birds as an adaptive agent in the reduction of intraspecific competition has been extensively reviewed and discussed by Selander (1966), and more recently additional data have been added by many authors. These are primarily cases in which morphological differences in the bill length between males and females indicates differences in foraging preferences between the sexes. Selander (1966) also suggested that behavioral polymorphism expressed as sexually dimorphic behavior could operate without concomitant modification of the feeding apparatus. This has been recently confirmed by Morse (1968) for wood warblers, Williamson (1971) for vireos, and Robins (1971) for a grassland sparrow. In these cases there were differences in foraging preferences between the sexes without expressed morphological differences in bill length. Birds have provided almost all of the examples of differential niche utilization by the sexes, primarily because foraging behavior is for the most part diurnal and easily observed. However, sexual differences which correlate with differences in foraging behavior have been recorded for several species of fresh-water fishes by Keast (1966), and for Anolis lizards by Schoener (1967, 1968). Sexual dimorphism in the feeding apparatus of skates has often been noted but almost no evidence concerning the significance of this phenomenon has been presented. Perhaps the most intriguing aspect of this phenomenon is that all skates (for which we have information) can be sorted roughly into three categories (Fig. 1): 1) essentially non-dimorphic, in which both sexes have pointed teeth adapted for grasping and tearing rather active prey; 2) dimorphic species in which teeth not brought into use are pointed, but the points are retained in the males while those in the females are quickly reduced to grinding buttons; and 3) dimorphic species in which the grinding character of the female dentition is genetically fixed and not just produced by wear. The purpose of this paper is to consider the possibility that the strongly dimorphic feeding apparatus in many skates represents another example of differential niche utilization by the sexes.

A new Chinese specimen indicates that 'protofeathers' in the Early Cretaceous theropod dinosaur Sinosauropteryx are degraded collagen fibres

Alleged primitive feathers or protofeathers in the theropod dinosaur Sinosauropteryx have potentially profound implications concerning feather morphogenesis, evolution of flight, dinosaur physiology and perhaps even the origin of birds, yet their existence has never been adequately documented. We report on a new specimen of Sinosauropteryx which shows that the integumental structures proposed as protofeathers are the remains of structural fibres that provide toughness. The preservation in the proximal tail area reveals an architecture of closely associated bands of fibres parallel to the tails long axis, which originate from the skin. In adjacent more exposed areas, the fibres are short, fragmented and disorganized. Fibres preserved dorsal to the neck and back and in the distal part of the tail are the remains of a stiffening system of a frill, peripheral to the body and extending from the head to the tip of the tail. These findings are confirmed in the holotype Sinosauropteryx and NIGP 127587. The fibres show a striking similarity to the structure and levels of organization of dermal collagen. The proposal that these fibres are protofeathers is dismissed.

The hand of birds revealed by early ostrich embryos.

Abstract. The problem of resolving the homology of the digits of the avian hand has been framed as a conflict between paleontological and embryological evidence, the former thought to support a hand composed of digits I, II, III, because of similarity of the phalangeal formulae of the earliest known bird Archaeopteryx to that of Mesozoic pentadactyl archosaurs, while embryological evidence has traditionally favored a II, III, IV avian hand. We have identified the critical developmental period for the major features of the avian skeleton in a primitive bird, the ostrich. Analysis of digit anlagen in the avian hand has revealed those for digits/metacarpals I and V, thus confirming previous embryological studies that indirectly suggested that the avian hand comprises digits II, III, IV, and was primitively pentadactyl.

Confuciusornis sanctus compared to Archaeopteryx lithographica

L.D. Martin, Z. ZhouNatural History Museum and Department of Systematics and Ecology,University of Kansas, Lawrence, KS 66045, USAL. HouInstitute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences, P.O. Box 643, Beijing 100044, ChinaA. FeducciaDepartment of Biology, University of North Carolina, Chapel Hill,NC 27599-3280, USA

Bird Origins Anew

— 1 — The Auk, Vol. 130, Number 1, pages 1−12. ISSN 0004-8038, electronic ISSN 1938-4254.  2013 by The American Ornithologists’ Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www.ucpressjournals. com/reprintInfo.asp. DOI: 10.1525/auk.2013.130.1.1 1E-mail: feduccia@bio.unc.edu The smallesT dinosaur is The bee hummingbird...found only in Cuba (Norell et al. 1995)