An unusual lizard (Reptilia: Squamata) from the Early Cretaceous of Las Hoyas, Spain

The Early Cretaceous (Barremian) lepidosaurian assemblage of Las Hoyas (Cuenca Province, Castilla-La Mancha), Spain, resembles that of roughly contemporaneous localities at Montsec (Catalonia), Una (Castilla-La Mancha) and Galve (Aragon) in being dominated by the scincomorph lizard Meyasaums ( Ilerdaesaurus ). It differs in the presence of two previously unknown taxa, one of which, described here, shows a strikingly unusual morphology in its ribs and distal limb skeleton suggestive of climbing specialization. This form is sufficiently distinct from other known taxa to warrant the erection of a new genus and species, Scandensia ciervensis gen. et sp. nov. Cladistic analysis of Scandensia suggests that it forms a sister taxon to living squamates (Iguania + Scleroglossa and all descendants of their most recent common ancestor).     

The origin and paleoecologic significance of the trace fossil Asteriacites in the Pennsylvanian of Kansas and Missouri

The trace fossil Asteriacites, recorded in Cambrian to Recent shallow- and deep-marine facies, is traditionally interpreted as the resting trace of asterozoans. Well-preserved specimens of A. lumbricalis are abundant in Pennsylvanian (Upper Carboniferous) shallow- and marginal-marine siliciclastic deposits of eastern Kansas and western Missouri. Detailed morphologic analysis of these specimens suggests that they record the activities of mobile epifaunal ophiuroids. Evidence of a brittle star (ophiuroid) producer rather than sea star (asteroid) is provided by (1) trace-fossil morphologic features reflecting the anatomy of the producer (e.g., well-differentiated central structure, slender vermiform arms) and ophiuroid burrowing technique (e.g., proximal arm expansion, arm branching), and (2) mode of occurrence (e.g., gregarious behavior, horizontal and vertical repetition). Vertical and horizontal repetition produces complex aggregates of A. lumbricalis that are interpreted either as escape structures (fugichnia) or as feeding structures, respectively. Ophiura texturata is proposed as a modern analogue for the A. lumbricalis producer, based on inferred life habit and feeding behavior. Asteriacites lumbricalis is present in two different intertidal trace-fossil assemblages. The first assemblage is characterized by high diversity and records tidal flats developed outside of embayments under normal marine conditions. The second assemblage consists of A. lumbricalis together with a few other ichnotaxa and represents a depauperate association that developed in restricted tidal flats within an embayment or estuarine setting. This challenges the conventional view of Asteriacites as a normal-marine salinity indicator. Some echinoderms, and particularly asterozoans, penetrate and inhabit modern environments of depressed salinity. The presence of Asteriacites in Pennsylvanian marginal-marine facies of Kansas and Missouri provides evidence that ophiuroids had adapted to brackish-water conditions by the late Paleozoic.     

A new subfamily of Figitidae (Hymenoptera, Cynipoidea)

Larvae of the parasitic wasp family Figitidae develop as internal parasitoids of other endopterygote insect larvae. The hosts are typically dipteran larvae living in other microhabitats but the earliest figitids probably attacked gall-inhabiting hymenopteran larvae. Here, we formally describe a new genus (Parnips) and subfamily (Parnipinae) for a species that is likely to be a surviving representative of these early gall-associated figitids. The species, P. nigripes , has been reared repeatedly from galls inside the seed capsules of annual poppies (Papaver dubium and P. rhoeas) in the Mediterranean region together with the gall inducer Barbotinia oraniensis belonging to the Cynipidae, the sister group of Figitidae. Parnips nigripes is strikingly cynipid-like and was first assumed to be a cynipid gall inducer of the genus Aulacidea. Phylogenetic analyses have since indicated that the similarity with the Cynipidae is symplesiomorphic and that P. nigripes belongs to the Figitidae, where it forms the sister group of all other extant figitids. Recently, it has also been shown that P. nigripes is a parasitoid of the gall-inducing Barbotinia oraniensis , consistent with its proposed phylogenetic position. Parnips nigripes shares several unusual morphological traits with its host. We speculate that many of these similarities are homologous even though the lineages separated at least 83 million years ago.     

Parasites and the blackcap's tail: implications for the evolution of feather ornaments

Although parasites may impair the expression of tail ornaments in birds, the importance of parasitism in driving the evolution of the initial stages of tail ornamentation is not well understood. Parasites could have negatively affected the expression of nonexaggerated, functional traits before these evolved ornaments, or they could have played a relevant role only after tails became ornamental and hence too costly to produce. To shed light on this issue, we studied the correlation between the abundance of feather mites (Acari, Proctophyllodidae) and the size, quality, growth rate and symmetry of tail feathers of blackcaps ( Sylvia atricapilla ), a non-ornamented passerine. Tail length was not correlated with mite load, yet blackcaps holding many mites at the moment of feather growth (fledglings) had lighter and more asymmetric feathers that grew at relatively lower rates. In blackcaps whose mite load was measured one year after feather growth (adults), only the negative correlation between mite intensity and feather symmetry remained significant. Changes in mite load since the moult season could have erased the correlation between condition-dependent feather traits and current parasite load in adults. Our results support the idea that different traits of non-ornamental feathers can signal parasite resistance. Therefore, parasitism could have played a central role in the evolution of tail ornamentation ever since its initial stages.  © 2002 The Linnean Society of London. Biological Journal of the Linnean Society , 2002, 76 , 481–492.     

Factors controlling planktonic size spectral responses to autumnal circulation in a Mediterranean lake

1. Studies of planktonic size spectra have been common in recent years, but few concerning the effects of autumnal lake processes on those distributions have been reported. We carried out such a study for 93 days during early circulation in a small, mesotrophic, seepage lake with only benthivorous fish. Two distinct mixing periods occurred before full circulation in Las Madres lake (Spain). As a proxy of overall planktonic‐ and phytoplanktonic size distributions, the shape of a Pareto I power function was traced over time. The phytoplanktonic size spectrum was also used to test the hypothesis that phytoplankton might show a trophic cascade during early circulation. 2. Our results demonstrated that the overall size spectrum changed smoothly during the autumnal mixing, with sequential changes controlled by a combination of biotic and abiotic variables, albeit experiencing different temporal delays, always shorter than a week. A first combined, autogenic process, driven both by algal competition and a crustacean trophic effect, and a second physical‐forcing process, driven by the combined effect of convective cooling and decreasing irradiance on mixed layer dynamics, may be related to the overall planktonic spectrum in the first and second periods of mixing, respectively. 3. The phytoplanktonic size spectrum did not appear to be dictated by a trophic cascade in Las Madres lake, their dynamics being mostly controlled by physical forcing, along with some effect of non‐edible primary producers and cladocerans in the first and second periods of mixing, respectively. 4. Our results and others covering early circulation with longer sampling periods suggest that planktonic size spectral dynamics during lake circulation is context‐dependent (i.e. varying from one lake to another), thus preventing generalisation. However, when further studies with finer temporal resolution have been carried out, it is likely that clear‐cut patterns in the planktonic size spectrum will emerge, arising from the interplay of autogenic plankton dynamics, implying some resistance to community change because of external physical forcing, and the velocity of autumnal mixing.