The cuticle of the aglaspidid arthropods, a red-herring in the early history of the vertebrates

The supposed early vertebrate Anatolepis has recently been reinterpreted by Peel (1979; Rapp. Gr∅nl. Geol. Unders. 91 ) as an arthropod, probably aglaspidid. The cuticle of Aglaspis shows a characteristic arthropodan structure, including laminations and ducts, but it is apparently composed of primary phosphate. Apart from composition, the skeletal histology of Anatolepis is totally different, and this, together with more general considerations, eliminates any possibility of arthropod affinity. Anatolepis remains the earliest known vertebrate. Aglaspididae, cuticle, ultrastructure, Vertebrata, Upper Cambrian.     

Decay and composition of the hemichordate Rhabdopleura: implications for the taphonomy of graptolites

Although the graptolites lacked biomineralised tissue, their skeletons are abundantly preserved in deeper-water mudstones. Decay experiments and observations on the closely related living hemichordate Rhabdopleura demonstrate that the periderm and stolon are highly resistant to decay, remaining intact for months, whereas the zooids are unrecognizable within days. The extreme rarity of the preservation of traces of the zooids in graptoloids reflects their planktic lifestyle; the zooids had normally decayed before burial. Curie-point-gas-chromatography (Py-GC) and Curie-point-gas-chromatography-mass spectrometry (Py-GC-MS) of the periderm of Rhabdopleura confirms that proteinaceous organic matter is a major constituent. Ultrastructurally preserved graptolite periderm (Ordovician, Oklahoma; Silurian, Arctic Canada), on the other hand, is a highly altered kerogen-like substance rich in aliphatic biomacromolecules. The composition of the preserved graptolite periderm reflects diagenetic replacement by components probably mainly derived from algal cell walls.     

The origin of pterygotid eurypterids (Chelicerata: Eurypterida)

Abstract: The Silurian and Lower Devonian pterygotid eurypterids were the largest of all arthropods, but their origin and early evolution are poorly understood. Pterygotus? ventricosus from Kokomo, Indiana, is shown to be the most basal of the pterygotids and constitutes the sister taxon to the rest of the clade. P.? ventricosus has walking appendages similar to those of Slimonia, which is the sister taxon of pterygotids. There is no evidence in P.? ventricosus of the dorsal median pretelson carina characteristic of other pterygotids, but the taxon does have the typical pterygotid undivided genital appendage. The status of the iconic pterygotid character (and presumed synapomorphy), the enlargement of the chelicerae, is uncertain in the Kokomo pterygotid. All the diagnostic characters of pterygotids did not develop simultaneously. A new genus Ciurcopterus is erected to accommodate the Kokomo pterygotid and Pterygotus? sarlei Ciurca and Tetlie.     

Characteristics of woods used recently and historically by Lesser Spotted Woodpeckers Dendrocopos minor in England

Lesser Spotted Woodpecker Dendrocopos minor numbers have declined greatly in England since the early 1980s for reasons that are not yet fully understood. It has been suggested that the species’ decline may be linked to the increase in Great Spotted Woodpeckers Dendrocopos major, changes in woodland habitat quality (such as deadwood abundance) and landscape‐scale changes in tree abundance. We tested some of these hypotheses by comparing the characteristics of woods in southern England where the species is still relatively numerous with those of woods used in the 1980s before the major decline. In each time period, habitat, predator and landscape information from woods known to be occupied by Lesser Spotted Woodpeckers was compared with those found to be unoccupied during surveys. Before the main period of decline, Lesser Spotted Woodpeckers used oak‐dominated, mature, open woods with a large amount of standing deadwood. Habitat use assessed from recent data was very similar, the species being present in mature, open, oak‐dominated woodlands. There was a strong relationship between wood use probability and the extent of woodland within a 3‐km radius, suggesting selection for more heavily wooded landscapes. In recent surveys, there was no difference in deadwood abundance or potential predator densities between occupied and unoccupied woods. Habitat management should focus on creating and maintaining networks of connected woodlands in areas of mature, open woods. Finer‐scale habitat selection by Lesser Spotted Woodpecker within woodlands should be assessed to aid development of beneficial management actions.     

Mark—Recapture Accurately Estimates Census for Tuatara,a Burrowing Reptile

Abstract: Estimates of population size are necessary for effective management of threatened and endangered species, but accurate estimation is often difficult when species are cryptic. We evaluated effectiveness of mark–recapture techniques using the Lincoln–Peterson estimator for predicting true census size of a population of tuatara (Sphenodon punctatus), a burrowing reptile that is a conservation priority in New Zealand. We found that Lincoln–Peterson estimates (NŇ = 85) were accurate for predicting the census size (N = 87) after only a 3-day mark–recapture survey. We recommend this method as a cost-effective way to accurately estimate population size for isolated, inaccessible tuatara populations, because it requires limited personnel, expertise, and time, and has low environmental impact on fragile sites.     

Is productivity of mesic savannas light limited or water limited? Results of a simulation study

A soil–plant–atmosphere model was used to estimate gross primary productivity (GPP) and evapotranspiration (ET) of a tropical savanna in Australia. This paper describes model modifications required to simulate the substantial C4 grass understory together with C3 trees. The model was further improved to include a seasonal distribution of leaf area and foliar nitrogen through 10 canopy layers. Model outputs were compared with a 5‐year eddy covariance dataset. Adding the C4 photosynthesis component improved the model efficiency and root‐mean‐squared error (RMSE) for total ecosystem GPP by better emulating annual peaks and troughs in GPP across wet and dry seasons. The C4 photosynthesis component had minimal impact on modelled values of ET. Outputs of GPP from the modified model agreed well with measured values, explaining between 79% and 90% of the variance and having a low RMSE (0.003–0.281 g C m^?2 day^?1). Approximately, 40% of total annual GPP was contributed by C4 grasses. Total (trees and grasses) wet season GPP was approximately 75–80% of total annual GPP. Light‐use efficiency (LUE) was largest for the wet season and smallest in the dry season and C4 LUE was larger than that of the trees. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in leaf area index (LAI) and foliar nitrogen (N_f) and relatively insensitive to changes in maximum carboxylation rate (V_cmax), maximum electron transport rate (J_max) and minimum leaf water potential (ψ_min). The modified model was also able to represent daily and seasonal patterns in ET, (explaining 68–81% of variance) with a low RMSE (0.038–0.19 mm day^?1). Current values of N_f, LAI and other parameters appear to be colimiting for maximizing GPP. By manipulating LAI and soil moisture content inputs, we show that modelled GPP is limited by light interception rather than water availability at this site.     

The origin of multiplacophorans – convergent evolution in Aculiferan molluscs

Abstract: Multiplacophorans are Palaeozoic (Silurian to Permian) stem group polyplacophorans with 17 shell plates in a particular arrangement of single terminal plates separated by three columns of plates forming five transverse rows. Their distinctive morphology has prompted disparate interpretations of their relationship to polyplacophorans. Some features are strikingly similar to crown group polyplacophorans and even to some living families. Here we describe two Devonian forms, Protobalanus spinicoronatus sp. nov., a hercolepadid from northeast Ohio, USA, and Hannestheronia australis gen. et sp. nov., a strobilepid from South Africa. Using the results from a Bayesian relaxed molecular clock to test competing scenarios of the relationship of multiplacophorans to crown group polyplacophorans, we demonstrate that multiplacophorans are stem group polyplacophorans in which certain characters of the crown group evolved convergently.