中国鳖科Pelodiscus属一新种研究

本邀请季１个产自桂东北及邻近地区的鳖类新种－小鳖。该鳖种生活在水质清洁,砂砾石底质的江段,６０年代以前出产额丰,现已难觅踪影。对野生小鳖资源的保护已迫在眉睫。     

A revision of the trionychid turtle Procyclanorbis sardus Portis, 1901 from the late Miocene of Sardinia (Italy)

Procyclanorbis sardus Portis, 1901 is the first fossil trionychid turtle described from Sardinia. This late Miocene taxon was originally considered to have affinities with the African and southern Asian cyclanorbines. We here redescribe in detail the holotype specimen of this species, which has suffered severe degradation since its original publication. A comparison between the original state of the fossil and its current state of preservation is provided. On the basis of its anatomy, affinities of Procyclanorbis sardus with cyclanorbines are discarded and this taxon is demonstrated to be an indeterminate pan-trionychine. The distribution of fossil trionychids in the Mediterranean Islands is also discussed.     

An integrative approach to examining a homology question: shell structures in soft‐shell turtles

Understanding the patterns of shell reduction in turtles is relevant when examining both fossils and living forms. The soft‐shelled turtles (Trionychidae) are characterized by the general reduction of the peripheral bony elements of the carapace, and some species possess structures of contested homology. By examining Remane's ‘principal criteria’, we addressed the primary homology of the prenuchal and the posterior peripheral ossicles (= PPOs) of the Asian flapshell turtles, Lissemys spp., thus evaluating their topological equivalence, their structural quality, and the presence of intermediate forms in ontogeny and phylogeny. We conducted an analysis of gross morphology, bone histology, and ontogeny of these elements in a large sample of living and fossil trionychids and their sister‐group, the carettochelyids. We conclude that the prenuchal comprises a neomorphic structure that does not fulfil any of the homology criteria examined. The assessment of the homology of PPOs is less straightforward because of the presence of partly conflicting evidence. Nevertheless, PPOs and standard peripherals share an antero‐posterior polarity of the ossification pattern, which we interpret as a significant shared underlying developmental pattern. Depending on the phylogenetic position of Lissemys in trionychid phylogeny, the hypothesis of PPOs homology with standard peripherals is a straightforward one or, alternatively, one involving homologous developmental processes at other levels of the hierarchy, resulting in similar microstructural characteristics of these bony shell features. In this respect, we consider the antero‐posterior polarity of the ossification pattern of both PPOs and standard peripherals as providing potential evidence for the homology of the genetic control regulating the expression of both these structures, and therefore we interpret these structures as homologues on the basis of a deeply homologous underlying developmental process. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 462–476.     

A neglected lineage of North American turtles fills a major gap in the fossil record

Abstract: The fossil record of the two primary subclades of softshell turtles (Trionychidae) is exceedingly asymmetric, as a result of a ghost range of total clade Cyclanorbinae that is estimated at 80 Ma. Herein, we present the first phylogenetic analysis of Trionychidae that includes a representative of the poorly studied taxon Plastomenidae, which is known from the Campanian to Eocene of North America. The analysis reveals that plastomenids are stem cyclanorbines, thus significantly reducing the apparent ghost range of total group Cyclanorbinae to approximately 30 Ma. Plastomenids are either an early branching clade of stem Cyclanorbinae, or they represent a paraphyletic grade that gave rise to modern cyclanorbines. Although abundant, the fossil record is still too poorly understood to distinguish between these two primary hypotheses. The previously persistent extremely long ghost range of total clade Cyclanorbinae appears to have been the result of a research bias.     

Effect of acclimation temperature and substrate type on selected temperature,movement and activity of juvenile spiny softshell turtles (Apalone spinifera) in an aquatic thermal gradient

In some turtle species, temperature selection may be influenced by environmental conditions, including acclimation temperature and substrate quality. These factors may be particularly important for softshell turtles that are highly aquatic and often thermoregulate by burying in the substrate in shallow water microhabitats. We tested for effects of acclimation temperature (22 °C or 27 °C) and substrate type (sand or gravel) on the selected temperature and movement patterns of 20 juvenile spiny softhshell turtles (Apalone spinifera; Reptilia: Trionychidae) in an aquatic thermal gradient of 14–34 °C. Among 7–11 month old juvenile softshell turtles, acclimation temperature and substrate type did not influence temperature selection, nor alter activity and movement patterns. During thermal gradient tests, both 22- and 27 °C-acclimated turtles selected the warmest temperature (34 °C) available most frequently, regardless of substrate type (sand or gravel). Similarly, acclimation temperature and substrate type did not influence movement patterns of turtles, nor the number of chambers used in the gradient tests. These results suggest that juvenile Apalone spinifera are capable of detecting small temperature increments and prefer warm temperatures that may positively influence growth and metabolism, and that thermal factors more significantly influence aquatic thermoregulation in this species than does substrate type.