Page:EB1922 - Volume 32.djvu/32

14

Origin of Birds. Palaeontologists still agree in endorsing Huxley's opinion that birds are " glorified reptiles." The origin of birds, according to recent reviewers such as Osborn and Gregory, brings us cjose to the two-temporal-arched (i.e. Diapsida) reptiles, namely, to the stem which also gave off the dinosaurs, the pterosaurs and the smaller parasuchians (Eu- parkeria). Fossil bird remains are extremely rare. The earliest bird known is the famous Archaeopteryx of the Jurassic of Soln- hofen, Germany. This is largely a bird, excepting in the tail, the simplicity of the feather arrangement and the possession of teeth. According to the four-winged hypothesis of origin ad- vocated by Beebe, we should some day discover a bird with parachute-like action in both fore and hind limbs. Recent con- tributions of note on this subject are those of Gerhard Heilmann (1913) and of William Beebe (1915), and the synthetic reviews of Osborn (1918) and Lull (1917).

Origin of Mammals. Evidence has been accumulating rapidly in favour of the theory that the origin of the mammals should be traced to the more progressive terrestrial mammal-like reptiles (the Cynodonlia) of the Permian and Triassic of South Africa and Europe, as described in the studies of Broom, Watson, Haughton, Osborn and Gregory. Structurally related to these Cynodonts are the so-called Protodonls of Osborn, e.g. Droma- Iherium and Microconodon of the Triassic of North Carolina. But of equal antiquity are the multituberculates, e.g. Plagiaulax and Microlestes, widely spread over Europe and North America. No substantial additions have been made during the decade to our knowledge of this vague period; readers are referred to the reviews of Osborn (1918) and Lull (1917), also to the recent works of Gregory, The Orders of Mammals (1910) and The Origin and Evolution of the Human Dentition (1921).

Origin of Primates and of Man. Combined palaeontological and anatomical evidence indicates that the source of the Primates is to be looked for among tree-living insectivorous mammals more or less closely similar to the modern tree shrews ( Tupaiidae) of Africa. This view advanced with ability by Gregory is in general accord with the opinion that during the phase of arboreal life many of the psychic and anatomical characters of the Pri- mates were acquired. It was not until the Lower Eocene of North America and of Europe that there appeared undisputed Primates of lemuroid affinity, e.g. notharctids and tarsioids in America, adapids and tarsioids in Europe. At this time the zoological relation of the two continents was close and it would appear that while the primitive horses were acquiring their cursorial characters on the ground, these primitive lemuroids were acquiring their distinctive characteristics in the trees. Actual ancestors of the existing Tarsius of Madagascar have been found in France (Pseudoloris). The attempt of Ameghino to trace the higher Primates to South American types, e.g. Homun- culus, appearing in the Lower Miocene of Patagonia, is not sup- ported, because these animals from the first are the true broad- nosed, i.e. platyrrhine, type still characteristic of South America. The Old World division of the catarrhines or narrow-nosed true Primates has been traced to the Parapithecus, described by Max Schlosser from the Lower Oligocene of Egypt. Propliopithecus is possibly ancestral to the true anthropoid apes and thus possibly related to the ancestors of man himself. Darwin's broad con- clusion that man was derived from " some ancient member of the anthropomorphous subgroup of Old World Primates " is fully sustained by anatomical evidence, but the precise lines of descent are still in dispute. Some hold that the human line came from Middle Tertiary anthropoid apes allied to Dryopithecus of France and Sivapithecus of India, while others (including the present writer) regard the Hominidae as a widely distinct family separated especially by its upright walking gait, by the non- divergence of the great toe, and by the retention of its tool-making thumb. A series of masterly reviews of this whole question has appeared in the American Museum publications from Gregory, whose recent memoir On the Structure and Relations of Noth- arctus, an American Eocene Primate (1920) sums up our present knowledge of this whole subject. (See also ANTHROPOLOGY.)

The Dinosaur Fauna of Alberta, Canada. The greatest new

achievement in exploration is the revelation of the dinosaur fauna of Alberta in the fossil beds extending along the Red Deer river, which were first made known to science by explorers of the Canadian Geological Survey in 1897, 1898, 1901. The first general review of this wonderful fauna was that of Osborn and Lambe, On Vetebratra of the Mid-Cretaceous of the North West Territory (1902), based chiefly on the collections in the Ottawa Museum. The American Museum explorations under Barnum Brown, which extended over ten years, have resulted in the discovery of the entire fauna of the middle portion of Upper Cretaceous time, a complete revelation especially of the dinosaur world as it approached the height of its adaptive radiation into herbivorous and carnivorous, armoured and defenceless, swift- moving and slow-moving types, which severally imitate more or less fully the long subsequent adaptive radiation of the mammals. In 1914 the Canadians renewed exploration, so that at present the Ottawa and Toronto Museums have rich collections, part of which has been described by the late Lawrence M. Lambe, while Osborn, Barnum Brown and W. A. Parks have also made known a part of this wonderful fauna. Two of the greatest extremes of adaptation, namely, Dcinodon or Gorgosaurus and Strulhiomimus, are figured in the accompanying Plate II. In the same plate appear some of the outstanding American dis- coveries of the decade.

NEW DISCOVERIES AMONG FOSSIL VERTEBRATES

Fossil 'Fishes. Dr. A. Smith Woodward's Fossil Fishes of the English Wealden and Purbeck (1915-8) is a beautifully illustrated memoir of the most thorough, systematic type, well sustaining the traditions set by Traquair and by the author himself in earlier works. The period dealt with affords an interesting cross- section of the stream of piscine evolution, at a time when many of the old Mesozoic ganoids were dying out and the telcost fishes were beginning their remarkable expansion. Other important systematic memoirs are those by Stolley on the ganoids of the German Muschelkalk (1920) and by Stensio (1921) on Triassic fishes from Spitzbergen. The latter memoirs contain a wealth of material of great morphological interest concerning the early stages in the evolution of the skull of the fringc-fmned and ray- finned ganoid fishes; this discussion also throws light on the origin of certain elements in the skull of higher vertebrates. In this connexion should be mentioned the brief but highly important paper on Eusthenopleron by W. L. Bryant (1919). This fringe- finned ganoid is of particular interest because the construction of its skull and paired limbs approaches the type which may be expected in the piscine ancestors of the land-living vertebrates. The arrangement of the elements on the under side of the skull of this fish raises morphological questions of wide general interest. Papers by Watson and Day (1916) and by Gregory (1915, 1920) deal with the ancestral relations of these fringe-finned ganoids with the land-living vertebrates (tetrapods).

The swarming fauna of Devonian arthrodires, ptyctodonts, cladodonts and other archaic fossil fishes from the vicinity of Buffalo, N.Y., is ably described by Bryant and Hussakof in their Catalog of the Fossil Fishes in the Museum of the Buffalo Society of Natural Sciences (1918). A serious difficulty encoun- tered by all students of recent and fossil fishes is the getting in contact with the vast and scattered literature of the subject. The great Bibliography of Fishes by Bashford Dean and his associates Eastman and E. W. Gudger (1917) will undoubtedly stimulate research in this field.

Fossil Amphibians. The outstanding publications in this field are The Coal Measures Amphibia of North America by R. L. Moodie (1916) and a memoir on The Structure, Evolution and Origin of the Amphibia by D. M. S. Watson (1919). Moodie 's memoir is a valuable description and compilation of the extensive and varied fauna of swamp-living amphibians of the American Coal Measures. Watson's memoir is a brilliant and highly original contribution to the classification and phylogeny of the labyrinthodonts. Much detailed work on fossil amphibians ap- pears in papers by von Huene, Broom, Williston, van Hoepen, Haughton and others.