Morphology, Phylogeny and Paleobiogeography of Fossil Fishes

Auszug

This book presents recent findings on the morphology, phylogeny and paleobiogeography of fossil fishes, honoring Professor Meemann Chang for her contributions to paleoichthyology and to the study of early vertebrate evolution. The seeds for this book started to germinate when a symposium honoring Meemann Chang was held at the 2005 Annual Meeting of the Society of Vertebrate Paleontology (SVP) in Mesa, Arizona. However, they had been planted long before as all of us, editors and contributors alike, can recount instances in which contact with Meemann had an effect on our early professional and personal development. This aspect of Meemann was brought into focus by Nature, which carried a report on her career based on interviews with her colleagues and former students attending the symposium (Dalton, 2006).
With a foreword by Dr. Henry Gee (Senior Science Editor of Nature), an introduction, 22 research papers by leading vertebrate paleontologists from 14 countries, and 220 photos and illustrations, this book covers important fossil forms ranging from the Paleozoic to the Cenozoic and reflects research advances based on traditional paleontological methods as well as new techniques such as CT scanning. The contributions came from almost all the major researchers in the study of early vertebrates, especially those working on Paleozoic and Mesozoic fishes, and cover all the major fossil fish groups studied by Meemann during her career, while reporting on new developments in each of these fields.
Agnathans have not been a major focus of Meemann’s research but her paper on a lamprey from the Jehol biota (Chang et al., 2006) was an important addition to our knowledge of a rarely preserved group. In this book, papers on anaspids and anaspid-like agnathans show that these animals may have had a spiral intestine similar to that of gnathostomes, and a new heterostracan from the western U. S. is named after her (the first of two such honors in this book). A paper on the enigmatic acanthodian Machaeracanthus shows it to have been an acanthodian with ‘paired pairs’ of pectoral fin spines and a perichondrally ossified scapulocoracoid, an important step forward in our understanding of this taxon. The contributions on placoderms include descriptive studies on new forms from northern Siberia and western Australia and also a review of pectoral fin development in gnathostomes based on a revision of previous hypotheses and new fossil arthrodire material. Chondrichthyans are represented by several papers describing new material but particularly by an important study on new articulated material from the Early Devonian of the Northwest Territories showing that the scale- and spine-based distinctions between acanthodians and chondrichthyans do not account for the diversity that is now apparent. The section on osteichthyans is extensive as might be expected since this is the main area that Meemann has worked on during her career. The first paper in this section describes how the appropriately named sarcopterygian Meemannia eos shows features of the odontodes that are shared between stem-group sarcopterygians, basal actinopterygians, and stem-group osteichthyans. Much new information on the neurocranium of fossil fishes has been developed in recent years using CT scanning and CT studies of the snout of Devonian dipnoans and the neurocranium of Powichthys provide new morphological and phylogenetic information. In addition, a study of the neurocranium of Litoptychius adds to information on sarcopterygian phylogeny and results in a clearer understanding of stem-tetrapod phylogeny, while new and uncrushed material of Eusthenopteron enables a revision of the morphology of the ethmosphenoid region. Lungfish are covered in three papers, and a study of fin morphology indicates that the postcranial anatomy may be an underexploited source of characters for phylogenetic studies in this group. The role of fossils in the development of an understanding of phylogenetic relationships is also examined here using the example of teleost phylogenies and it is concluded that despite the wealth of information from modern fish, fossils – particularly those of stem members from monophyletic groups – do have an important role to play. Finally Meemann’s interest in paleoecology and paleogeography is represented by two papers. The first, on the Jehol Biota, shows that the fish fauna, somewhat overshadowed by the remarkable dinosaur record, does have important paleobiogeographic implications with endemic forms indicating isolation until the Late Cretaceous when a dispersal to North America is hypothesized. The second paper is a very important overview of the Devonian vertebrate record in South America, something that has been very much needed. This demonstrates the presence of two faunal assemblages of which the earlier one equates with the “Malvinokaffric Realm” based on invertebrate communities.
This book is a tribute to the tenacity and dedication that Meemann Chang has shown to paleoichthyology and the widespread influence she has had on the field and the researchers involved in it.