Download Free The Downtonian And Devonian Vertebrates Of Spitsbergen Family Cephalaspidae By E A Stensio Book in PDF and EPUB Free Download. You can read online The Downtonian And Devonian Vertebrates Of Spitsbergen Family Cephalaspidae By E A Stensio and write the review.

The proliferation of scientific texts and their rapidly escalating costs demands of an author some justification for the production of yet another specialised volume; particularly one that treats of a relatively obscure group of animal- the Cyclostomes-whose significance is little appreciated outside the circle of professional biologists. Yet, within the zoological literature this group of vertebrates has always commanded a degree of attention, quite dispropor tionate to the comparatively small numbers of species involved or their economic importance. This special interest stems in the main from their unique phylogenetic status. Asjawless vertebrates the hagfish and the lamprey are regarded as the sole survivors of a once flourishing group of Palaeozoic vertebrates-the Agnathans-amongst which are numbered the first verte brates to appear in the fossil record. Because of this relationship to the fossil agnathans it was inevitable that past discussion of the phylogenetic signifi cance of the cyclostomes should have been dominated by comparative anatomists and palaeontologists, although in recent years their unique evolutionary position has increasingly attracted the interest of comparative physiologists and students of molecular evolution. Within the last fifteen years both the hagfish and the lamprey have been the subject of separate publications describing in detail many aspects of their morphology, physiology and life cycles (Brodal, A. and Fiinge, R., The Biology ofMyxine, 1963; Hardisty, M.W. and Potter, I.C., The Biology of Lampreys, 1971-72.
The vertebrate integument arose about 450 million years ago as an ‘armour’ of dermal bony plates in small, jawless fish-like creatures, informally known as the ostracoderms. This book reviews the major changes that have occurred in the vertebrate integument from its beginnings to the present day. Critical questions concerning the origin, structure and functional biology of the bony integument are discussed and intrinsically linked to major steps in vertebrate evolution and phylogeny—the origin of jaws and the origin of teeth. The discussions include the origins of mineralization of major vertebrate skeletal components such as the dermatocranium, branchial arches and vertebral column. The advances that led to the origin of modern fishes and their phylogenetic development are reviewed and include the evolution of fins and replacement of the bony plates with several types of dermal scales. The evolution of reptiles saw a major transformation of the integument, with the epidermis becoming the protective outermost layer, from which the scales arose, while the dermis lay below it. The biological significance of the newly-evolved β-keratin in reptilian scales, among the toughest natural materials known, is discussed in the context of its major contribution to the great success of reptiles and to the evolution of feathers and avian flight. The dermis in many vertebrates is strengthened by layers of oppositely oriented cross-fibres, now firmly entrenched as a design principle of biomechanics. Throughout the book conventional ideas are discussed and a number of new hypotheses are presented in light of the latest developments. The long evolutionary history of vertebrates indicates that the significance of the Darwinian concept of “survival of the fittest” may be overstated, including in our own mammalian origins and that chance often plays a major role in evolutionary patterns. Extensive illustrations are included to support the verbal descriptions. Professor Theagarten Lingham-Soliar is in the Department of Life Sciences at the University of KwaZulu-Natal.
In this authoritative three-volume reference work, leading researchers bring together current work to provide a comprehensive analysis of the comparative morphology, development, evolution, and functional biology of the skull.
Stratigraphy of Svalbard. Translation of Materialy po stratigrafii Shpitsbergen, Leningrad, 1967.
The marriage of evolutionary biology with developmental biology has resulted in the formation of a new field, evolutionary developmental biology, or "evo-devo. This volume reviews current research findings and thought in the broad field of evo-devo, looking at the developmental genetic mechanisms that cause variation and how alterations of these mechanisms can generate novel structural changes in a variety of plant and animal life. - Reviews current research findings and thought on evolutionary developmental biology, providing researchers an overview and synthesis of the latest research findings and contemporary thought in the area - Includes chapters discussing the evolutionary development of a wide variety of organisms and allows researchers to compare and contrast how genes are expressed in a variety of organisms—from fly to frog, to humans - Emphasizes the role of regulatory DNA in evolutionary development to give researchers perspective on how the regions of the genome that control gene expression and the protein factors that bind them are ultimately responsible for the diversity of life that has evolved