Sánchez-Villagra, M.R., Winkler, J.D., Wurst, L. 2007. Autopodial skeleton evolution in side-necked turtles (Pleurodira). -Acta Zoologica Carpal and tarsal anatomy was documented based on the observation of dry skeletons of adult specimens representing 25 species in 15 genera and on data taken from the literature. In addition, histological sections and cleared and double-stained autopodia of recently hatched and juvenile specimens representing seven chelid and pelomedusoid species were studied. There is much more morphological diversity in the manus than in the pes. Variation in autopodial skeletons includes: the astragalus and calcaneum are either separated or fused; fusion of distal carpals 3 -4 − 5 or just 4-5; number of centralia in the carpus; and presence/absence of a pisiform and of an accessory radial element. The widespread and probably basal phalangeal formula for Pleurodira is 2.3.3.3.3. Deviations are Pelomedusa subrufa , exhibiting a reduction to 2.2.2.2.2, Pelusios spp. with one phalanx less in digit I and for one species in digit V as well, and Acanthochelys pallidipectoris with an additional phalanx in the fourth finger. Six discrete characters itemizing some of the morphological variation observed were plotted on a composite pleurodire phylogeny, revealing not only homoplastic patterns but also the utility of some characters in supporting the monophyly of several clades. The pisiform is the last carpal element to ossify in Chelus fimbriatus. We hypothesize that the so-called fifth hooked metatarsal represents the fusion of distal tarsal 5 with metatarsal V. The accessory radial element that was occasionally present in the turtles examined may represent an atavism of the otherwise lost radiale of turtles.

Fossil eggshells from the Late Miocene Urumaco Formation of north-western Venezuela are reported. Stereomicroscopy and scanning electron microscopy were used to examine shell gross morphology and ultrastructure, respectively. Diagnostic turtle features in the eggshells include a distinct pattern of crystal aggregations within the shell units. The eggs had an elliptical shape with a maximum diameter of c. 56AE5 mm and width of c. 43AE5 mm, as measured in a specimen preserving the egg's outline. Scattered clutches of broken eggshells were found embedded in one horizon of a coarse, sandy sediment, with grains not well sorted containing foraminifera and fragments of bivalve shells. The sediments are rich in ichnofossils and the reddish colour of the sandstone indicates an oxidizing environment. These facts suggest that the eggs were deposited in a beach directly facing the sea or brackish waters, perhaps near a river delta or lagoon, as is typical of the Urumaco sequence. In the same stratigraphical layer and next to one of the egg clusters, a carapace assignable to the pelomedusoid Bairdemys venezuelensis was found, suggesting that this species was a colonial nester that laid its eggs in beaches and lived in a marine or nearshore marine environment.

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Summary1. Experiments in ecology occur in the laboratory, mesocosm or field. The choice of venue can influence the outcome and may be associated with trade-offs involving realism and precision. 2. We evaluated these trade-offs in an experiment measuring effects of venue on larval traits of Rana temporaria tadpoles. The design included laboratory, mesocosm and field venues, crossed with two treatments (presence and absence of caged Anax imperator dragonfly larvae). Realism of venues was evaluated by comparing experimental with wild tadpoles. 3. Venue influenced nearly every trait we measured, but some were more sensitive to venue than others. Larval and metamorphic performance, external morphology and predator-induced plasticity in many traits varied among venues, while behaviour was less dependent on venue. Tadpoles in mesocosms were most similar to those in field enclosures and the wild, although the phenotypic response to predation risk was greatest in the mesocosm venue. The laboratory environment triggered highly distinctive morphology. Precision was not higher in the laboratory than in other venues. 4. This study suggests that both constraints and research questions must be considered when choosing an appropriate experimental venue.

Fecundity selection, acting on traits enhancing reproductive output, is an important determinant of organismal body size. Due to a unique mode of reproduction, mating success and fecundity are positively correlated with body size in both sexes of male-pregnant Syngnathus pipefish. As male pipefish brood eggs on their tail and egg production in females occurs in their ovaries (located in the trunk region), fecundity selection is expected to affect both sexes in this species, and is predicted to act differently on body proportions of males and females during their development. Based on this hypothesis, we investigated sexual size dimorphism in body size allometry and vertebral numbers across populations of the widespread European pipefish Syngnathus typhle. Despite the absence of sex-specific differences in overall and region-specific vertebral counts, male and female pipefish differ significantly in the relative lengths of their trunk and tail regions, consistent with region-specific selection pressures in the two sexes. Male pipefish show significant growth allometry, with disproportionate growth in the brooding tail region relative to the trunk, resulting in increasingly skewed region-specific sexual size dimorphism with increasing body size, a pattern consistent across five study populations. Sex-specific differences in patterns of growth in S. typhle support the hypothesis that fecundity selection can contribute to the evolution of sexual size dimorphism.