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"Monks, Neale"
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Sea-level change and rock-record bias in the Cretaceous: a problem for extinction and biodiversity studies
The association between mass extinction in the marine realm and eustatic sea-level change in the Mesozoic is well documented, but perplexing, because it seems implausible that sea-level change could actually cause a major extinction. However, large-scale cycles of sea-level change can and do alter the ratio of shallow to deep marine continental-shelf deposits preserved in the rock record both regionally and globally. This taphonomic megabias alone could be driving patterns of first and last occurrence and standing diversity because diversity and preservation potential both change predictably with water depth. We show that the Cenomanian/Turonian faunal event in western Europe has all the predicted signatures expected if taphonomic megabias was the cause. Grade taxa terminating in pseudoextinction and Lazarus taxa are predominantly found in the onshore facies that disappear for extended periods from the rock record. Before other mass extinctions are taken at face value, a much more careful analysis of biases in the rock record needs to be carried out, and faunal disappearances need to be analyzed within a phylogenetic framework.
Journal Article
A New Cheilostome Bryozoan Genus Pseudoplanktonic on Molluscs and Algae
The little-known bryozoan Membranipora eburnea Hincks is redescribed and designated the type species of the new genus Jellyella. The twinned ancestrula of this malacostegan-grade cheilostome places it within the Membraniporidae, along with Membranipora and Biflustra. Jellyella is distinguished by the presence of intricately branched processes (spinules) projecting into the zooidal chambers, and a calcitic skeletal ultrastructure of transversely arranged, elongate spindles. The \"Gulf weed bryozoan,\" Membranipora tuberculata (Bosc), is also assigned to the new genus as Jellyella tuberculata. Both species of Jellyella seem primarily to encrust floating substrates: based on available museum material. J. eburnea usually grows on drifting shells of dead individuals of the cephalopod Spirula but can also be found as an epizoan of the floating gastropod Janthina and on algae; J. tuberculata is normally an epiphyte of Sargassum. Collections of Spirula shells from beaches around the Indian, Pacific, and Atlantic Oceans are commonly encrusted by J. eburnea but very seldom by any other bryozoans. Jellyella is therefore interpreted as a rare example of a pseudoplanktonic genus among the typically benthic bryozoans.
Journal Article
Ecology, stratigraphy and phylogeny of the heteromorph ammonoidea of the albian
The heteromorph ammonites (Mollusca: Cephalopoda: Ammonoidea: Ancycloceratida) of the Albian stage of the Cretaceous are reviewed from phylogenetic, morphological, and evolutionary perspectives. By use of cladistic analyses (using computer-based parsimony analysis) it is possible to hypothesise a likely evolutionary procession of ancestors and descendants, and to test the monophyletic nature of the families of Turrilitaceae, and to define the relationship of these families with each other and with the Ancyclocerateceae from which they are presumed to have evolved.Analysis of functional morphology indicates that heteromorph ammonites may have formed two distinct ecological groups: benthic or demersal forms which lived at a variety of depths on or close to the sea floor; and planktonic forms which were confined to deep water (greater than 100 to 200 metres) and were ecologically equivalent to modern Spirula and the cranchid squids. Both benthic and planktonic forms passed through a planktonic juvenile stage, which may have been the important dispersive stage of the life cycle, resulting in the fossils of heteromorph ammonites being known from every continent.Heterochronic processes are identified as important evolutionary mechanisms. The origin of the major planktonic groups of turrilitaceaen heteromorph ammonites can be characterised by progenesis, the precocious onset of maturity at a size and morphology comparable to the juveniles of the ancestors.
Dissertation
How to hunt galaxies from the suburbs
[...] target galaxies that are at least 50° above the horizon. [...] concentrate on edge-on galaxies, which are easier to see than face-on galaxies of equivalent magnitude.
Magazine Article
Stargaze with your Mac
Use your Mac to explore the universe and bring back some snapshots!
Magazine Article
Design a newsletter in Pages
Import the stories, do the page layout and prepare the mailshot - all within Pages '08
Magazine Article