I. the origin of species by means of natural selection

Leu-M

An improved and updated version of the statistical LOWESS fit to the marine 87Sr/86Sr record and a revised look-up table (V3:10/99; available from j.mcarthur@ucl.ac.uk) based upon it enables straightforward conversion of 87Sr/86Sr to numerical age, and vice versa, for use in strontium isotope stratigraphy (SIS). The table includes 95% confidence intervals on predictions of numerical age from 87Sr/86Sr. This version includes the Triassic and Paleozoic record (0509 Ma) omitted from previous versions because of the paucity of adequate data at the time of preparation. We highlight differences between the previous versions of the table and the current version and discuss some aspects of the 87Sr/86Sr record that may have geological significance. We give examples of how the table can be used and where it has proven useful.

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Strontium Isotope Stratigraphy: LOWESS Version 3: Best Fit to the Marine Sr‐Isotope Curve for 0–509 Ma and Accompanying Look‐up Table for Deriving Numerical Age

The new Conductivity Bridge derives its bridge source. voltage from a self-contained vacuum tube oscilltor adjusted to approximately 1,000 cycles. Voltage for the amplifier and null indicator tubes is provided by a.builtin D.C. power supply which operates directly from the A.C. power source. 9-324 Conductivity Bridge, without Conductivity Cell, for use with 110 volts 5060 cycle A.C. 9-351.Cosi~uCvity Cell, for use with Conductivity Bridge, constant 0.8, $20.00

The Vertebrate Eye and Its Adaptive Radiation.

Very different palaeogeographical reconstructions have been produced by a combination of palaeomagnetic and faunal data, which are re-evaluated on a global basis for the period from 500 to 400 Ma, and are presented with appropriate confidence (or lack of it) on six maps at 20 Ma intervals. The palaeomagnetic results are the most reliable for establishing the changing palaeolatitudes of Baltica, Laurentia and Siberia. However, global palaeomagnetic reliability dwindles over the 100 Ma, and more evidence for relative continental positioning can be gleaned from study of the distribution of the faunas in the later parts of the interval. The new maps were generated initially from palaeomagnetic data when available, but sometimes modified, and terranes were positioned in longitude to take account of key faunal data derived from the occurrences of selected trilobites, brachiopods and fish. Kinematic continuity over the long period is maintained. The many terranes without reliable palaeomagnetic data are placed according to the affinities of their contained fauna. The changing positions of the vast palaeocontinent of Gondwana (which has hitherto been poorly constrained) as it drifted over the South Pole during the interval have been revised and are now more confidently shown following analysis of both faunal and palaeomagnetic data in combination, as well as by the glacial and periglacial sediments in the latest Ordovician. In contrast, the peri-Gondwanan and other terranes of the Middle and Far East, Central Asia and Central America are poorly constrained.

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Earth geography from 500 to 400 million years ago: a faunal and palaeomagnetic review

Section One: Overview. 1.1: Introduction. 1.2: The Phanerozoic Timescale. 1.3: Biochronology. 1.4: Isotopic Geochronology. 1.5: Magnetostratigraphy. 1.6: Numerical Callibration of Major Phanerozoic Boundaries. Section Two: Explanatory Notes on Biostratigraphic Charts. 2.1: Cambrian. 2.2: Ordovician. 2.3: Silurian. 2.4: Devonian. 2.5: Carboniferous. 2.6: Permian. 2.7: Triassic. 2.8: Jurassic. 2.9: Cretaceous. 2.10: Cainozoic. 2.11: Quaternary Foraminifera Biostratigraphy. Section Three: Bibliography

An Australian Phanerozoic timescale

The relationships of placoderm fishes

The evolutionary transition from water to land exerts a continuing fascination, heightened by recent discoveries of transitional fossils in Canada and the reinterpretation as tetrapods (or near-tetrapods) of fossils once classified as fishes. But signs of land life are detectable even further back. A spectacularly preserved 380-million-year old fossil of the fish Gogonasus from the Devonian of Australia is fish-like in many respects, yet features of its ear and limbs are unexpectedly advanced. The transition from fishes to tetrapods was one of the most dramatic events in the evolution of vertebrates, but many pivotal fossils are incomplete, resulting in gaps in the data that are used for phylogenetic reconstruction. Here we present new observations from the most complete, acid-prepared Devonian tetrapodomorph fish yet discovered, Gogonasus1,2, which was previously placed just crownward of Kenichthys and rhizodontids3,4, the most primitive taxa on the tetrapod lineage. Unexpectedly, Gogonasus shows a mosaic of plesiomorphic and derived tetrapod-like features. Whereas the braincase and dermal cranial skeleton exhibit generalized morphologies with respect to Eusthenopteron5 or Panderichthys6, taxa that are traditionally considered to be phyletically close to tetrapods7,8, the presence of a deeply invaginated, wide spiracle, advanced internal spiracular architecture and near-horizontal hyomandibula are specialized features that are absent from Eusthenopteron9. Furthermore, the pectoral fin skeleton of Gogonasus shares several features with that of Tiktaalik, the most tetrapod-like fish10. A new phylogenetic analysis places Gogonasus crownward of Eusthenopteron as the sister taxon to the Elpistostegalia. Aspects of the basic tetrapod limb skeleton and middle ear architecture can now be traced further back within the tetrapodomorph radiation.

An exceptional Devonian fish from Australia sheds light on tetrapod origins

Five faunal provinces based on vertebrates are proposed for Early Devonian time, as follows: a cephalaspid province (Euramerica), an amphiaspid province (Siberia), a tannuaspid province (Tuva); a galeaspid-yunnanolepid province (South China), and a wuttagoonaspid-phyllolepid province (East Gondwana). It is suggested that certain major groups of early vertebrates differentiated in isolation on these continental areas as freshwater environments were invaded, and the interrelationships of some agnathans and placoderms endemic to these areas are analyzed using the cladistic vicariance biogeographic method of Platnick & Nelson (1978). Two possible episodes of biotic dispersal are identified; between Laurentia and Baltica at the end of the Silurian, and between Gondwana and Euramerica during the Late Devonian. Amongst placoderm fishes a Gondwana origin is suggested for Phyllolepis, antiarchs indicate affinity between Gondwana and South China, and euarthrodires may have evolved in Euramerica. Phylogenetic analys...

Gavin C. Young

Papers

An Australian Phanerozoic timescale

The relationships of placoderm fishes

An exceptional Devonian fish from Australia sheds light on tetrapod origins

Biogeography of Devonian vertebrates

A new Early Devonian placoderm from New South Wales, Australia, with a discussion of placoderm phylogeny