共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
Comparing the magnitude of the current biodiversity crisis with those in the fossil record is difficult without an understanding of differential preservation. Integrating data from palaeontological databases with information on IUCN status, ecology and life history characteristics of contemporary mammals, we demonstrate that only a small and biased fraction of threatened species (< 9%) have a fossil record, compared with 20% of non‐threatened species. We find strong taphonomic biases related to body size and geographic range. Modern species with a fossil record tend to be large and widespread and were described in the 19th century. The expected magnitude of the current extinction based only on species with a fossil record is about half of that of one based on all modern species; values for genera are similar. The record of ancient extinctions may be similarly biased, with many species having originated and gone extinct without leaving a tangible record. 相似文献
3.
《Annales de Paléontologie》2017,103(2):127-134
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. 相似文献
4.
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. 相似文献
5.
6.
Edem A. Eniang;Stephanie N. Ajong;Gabriel Hoinsoudé Segniagbeto;Eniang Inemesit Edem;Sulemana Bawa Gbewaa;Fabio Petrozzi;Julia E. Fa;Daniele Dendi;Mathias Behangana;Andrew D. Walde;Nioking Amadi;Godfrey C. Akani;Sery Gonedele-Bi;Nic Pacini;Pearson McGovern;Luca Luiselli; 《African Journal of Ecology》2024,62(3):e13323
Biological communities are structured by a variety of biotic and abiotic relationships, whose understanding forms the basis for effective conservation. Among the myriad factors influencing community dynamics, resource partitioning stands out, potentially enriching ecosystem complexity but also carrying risks for conservation if disregarded. In this study, we investigated intersexual and ontogenetic niche differences among populations of the West African softshell turtle Trionyx triunguis in Liberia, Cote d'Ivoire, Ghana and Nigeria. We observed that these distinct populations exhibited similar habitat preferences, favouring large rivers with abundant riverbank and aquatic vegetation, and muddy substrates. Disparities in habitat preferences were evident among populations and across various life stages, indicating the adaptability of the species. We found that the species was active throughout the year, but most of our sightings and captures occurred during the wet season. In light of the species' vulnerability to overhunting, our research findings provide important data on the ecology of this species that can assist in its effective conservation across all life stages. 相似文献
7.
Summary We used data on Contemporary and Pleistocene molluscs at one site in the Gulf of California to evaluate and extend earlier ideas about the relationship between local abundance and geographic distribution. For each species whose shells occurred in one Recent and two Pleistocene deposits, we measured its abundance in the sample and relative latitudinal position within its contemporary geographic range. Species near the edges of their ranges showed uniformly low abundances, whereas those near the centres exhibited a wide range of abundances. Species near the edges of their ranges also appear to have exhibited greater changes in abundance, including more colonization and extinction events, between the Pleistocene interglacial sample and the Recent one. The constraint of location in the geographic range on maximal local and regional abundance appears to offer an example of a connection between patterns and processes on local, regional, and geographical scales. Characteristics of community structure, such as relative abundance of individual species and frequency of local co-existence of multiple species, may be influenced by the location of the sample site with respect to the geographic ranges of the constituent species. These results demonstrate emergent, statistical features of population ecology and community organization that are manifest over geographic space and evolutionary time. 相似文献
8.
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。 相似文献
9.
Pedro Abellán Cesar J. Benetti Robert B. Angus Ignacio Ribera 《Global Ecology and Biogeography》2011,20(1):87-100
Aim To undertake a quantitative review of the Quaternary fossil record of European water beetles to evaluate their geographical and temporal coverage, and to characterize the extent and typology of the shifts in their geographical ranges. Location Europe. Methods We compiled Quaternary water beetle records from public databases and published references. We included in the analyses species of 10 families of aquatic Coleoptera, and recorded range shifts through the comparison of the location of fossil remains with the current distribution of the species. We explored the ecological representativeness of the fossil record, as well as the relationship between range shifts and the habitat type of the species. Results Our final data set included over 9000 records for 259 water beetle species. Fossil remains of aquatic beetles have been documented exclusively north of 42° N, with most of the records from the British Isles and virtually none from southern Europe or the Mediterranean Basin. Over 80% of the records were from the Late Glacial and the Holocene periods (the last 15 kyr), and overall approximately 20% of the species have been recorded outside their present range (23% excluding Holocene records). Most range shifts were southern or western extensions of currently widespread, northern species, with 10 species displaying major range shifts through the Palaearctic. Lentic species were significantly more likely to have experienced major range shifts, even accounting for the general ecological bias of the fossil record towards lentic habitats. Main conclusions Our results show that the Quaternary record of aquatic Coleoptera is geographically, temporally and ecologically skewed, necessitating caution when extrapolating general conclusions about range changes and ecological stability to other areas or periods on the basis of such scattered evidence. Most central and northern European species for which there are fossil records seem to have conserved their ranges through the Late Pleistocene, with geographical shifts mostly restricted to species with current widespread north Palaearctic or Holarctic distributions. Major range shifts through the Palaearctic are taxonomically uneven, suggesting either an idiosyncratic behaviour of taxa depending on ecological or phylogenetic factors, or a sampling artefact produced by the limited availability of taxonomic expertise. 相似文献
10.
11.
凯里组发现遗迹化石９属１４种,主要是以ＰｈｙｃｏｄｅｓｐｅｄｕｍＳｅｉｌａｃｈｅｒ为主的遗迹群落,重要的遗迹属如：Ｃｏｃｈｌｉｃｈｎｕｓ,Ｇｏｒｄｉａ,Ｍｏｎｏｍｏｒｐｈｉｃｈｎｕｓ,Ｏｌｄｈａｍｉａ,Ｐｌａｎｏｌｉｔｅｓ,Ｔｒｅｐｔｉｃｈｎｕｓ等常见于世界各地寒武纪Ｃｒｕｚｉａｎａ遗迹相。根据遗迹化石表明凯里组沉积于盐份、含氧量正常,海水能量中等的浅海软基底潮下带环境。 相似文献
12.
13.
晚晨旦世高家山生物群化石新材料 总被引：2，自引：2，他引：2
对张录易等（１９９２）所建立的管状骨骼化石Ｑｉｎｅｌｌａ属进行重新修订,根据基本宏观特征、壳面装饰和壳壁套管式结构管将Ｑｉｎｅｌｌａ ｓｈａａｎｘｉｅｎｓｉｓ Ｚｈａｎｇ,Ｌｉ ｅｔ Ｄｏｎｇ,１９９２和Ｑｉｎｅｌｌａ ｌｉｊｉａｇｏｕｅｎｓｉｓ Ｚｈａｎｇ,Ｌｉ ｅｔＤｏｎｇ,１９９２归入Ｓｉｎｏｔｕｂｕｌｉｔｅｓ ｃｉｅｎｅｇｅｎｓｉｓ Ｍｃｍｅｎａｍｉｎ,１９８５而Ｑｉｎｅｌｌａ属征限外表在 相似文献
14.
15.
吉林省文物考古研究所和榆树市博物馆考古工作者,最近在整理大桥屯1991年、1992年出土的哺乳类动物化石过程中,发现一根人类左胫骨化石。该标本两端的关节残缺,仅保存胫骨的中上段部分,长23.3厘米。经初步观察、对比,榆树大桥屯人类胫骨化石属于成年人。 另外,在整理动物化石过程中,除了发现人类化石外,还获有几件人工打制的石制品,石制品仅有石核和石片,未见第二步加工的石器。 相似文献
16.
Jan Zrzavý Pavel Duda Jan Robovský Isabela Okřinová Věra Pavelková Řičánková 《Zoologica scripta》2018,47(4):373-389
Phylogenetic relationships among 36 Recent and 42 extinct species of the Caninae (Canidae) were analysed, based on 360 morphological, developmental, ecological, behavioural and cytogenetic characters and 24 mitochondrial and nuclear markers. Primary phylogenetic analyses were accompanied by experimental analyses based on various combinations of data partitions and taxon samples. Leptocyon was recovered as a paraphyletic stem lineage of the Caninae; monophyly/paraphyly of the fox‐like canids (Vulpini) remains uncertain; Urocyon and Metalopex form a clade, possibly sister to all non‐Leptocyon canids; Otocyon, Nyctereutes and Nurocyon form a clade; dog‐like canids (Canini) are monophyletic (with South American Cerdocyonina and Afro‐Holarctic Canina); all South American hypercarnivores (Canis gezi, Protocyon, Speothos, Theriodictis) form a clade, close to Chrysocyon and Dusicyon; Canis arnensis, C. ferox, C. thooides, C. lepophagus and Eucyon spp. are basal to the Canina; Lycaon is an isolated African hypercarnivore; Cuon and its relatives (Xenocyon, possibly also Canis antonii, C. falconeri and Cynotherium) form a clade close to Canis s. str.; C. edwardii–C. etruscus–C. mosbachensis–C. palmidens–C. variabilis and hypercarnivorous Canis armbrusteri–C. dirus clades belong to Canis s. str. As the highly homoplastic morphological characters connected to dietary biology are the prominent characters available for the key fossil species, we conclude that macroevolutionary and palaeoecological analyses of the extinct and extant Caninae were to some extent compromised by the phylogenies used. 相似文献
17.
埃迪卡拉纪—寒武纪之交见证了地球—生命系统不同圈层的重大变革, 是复杂多细胞生物演化的重要转折期。华南是开展相关研究的主要区域之一, 但前人工作主要集中在化石材料丰富的浅水台地相区, 深水区生物组成面貌尚未得到充分认识。本研究对斜坡相区贵州交榜剖面的留茶坡组进行了详细研究, 通过酸蚀和薄片观察发现了丰富的化石材料, 包括: 海绵骨针、软舌螺、可能的原牙形类(? Protohertzina sp.)和织金钉类(? Zhijinites sp.)、球形疑源类、Megathrix longus, 及不同类型的多细胞藻类, 亲缘关系未定的Poratusiramus sp.、球形化石和形态多样的丝状、片状化石等。该化石组合属于寒武纪纽芬兰世幸运期, 其中的骨骼化石以海绵骨针为主。化石组合中既有与浅水区共有分子, 也有深水区特有类群, 丰富了斜坡相区的化石记录, 具有潜在的地层对比和演化意义。 相似文献
18.
A selective potassium leak is observed in resealed, human red blood cell ghosts when hemolysis is performed with distilled water at pH 6.5, 0° C. The leak, which has a maximum near pH 6.7, is suppressed when either magnesium or a chelating agent is present in the hemolysing medium. The potassium leak has the additional property that it can be suppressed after resealing by washing the ghost membranes in a medium containing a low concentration of ATP or EDTA. The data suggest that through the dilution of endogenous chelating agents at hemolysis a potassium leak may be unmasked. 相似文献
19.
利用改进后的Ｔｂ／ＤＰＡ荧光方法对在脉冲电场作用下人血影内Ｔｂ离子外渗的动力学过程进行了系统的研究。对不同场强和脉宽的电场处理的离子外渗量与时间的关系和电穿孔总面积随时间的变化进行了测量。结果表明,离子外渗的主要方式是由膜两侧浓度梯度导致的离子自由扩散。当脉冲宽度或强度两者之一给定的情况下,均存在临界场强和临界脉宽,在临界点以上电场作用下,膜上出现明显的电穿孔。在实验条件下,电穿孔的面积在２００－３００ｍｓ时达最大值,孔的面积和扩展速度与电场参数有关。临界点以下电场处理后,虽仍能测出离子的外渗,膜上可能未出现明显的电穿孔。 相似文献
20.
Isoleucine epimerization was used to date tooth enamel samples collected from the fossiliferous layers of several Pleistocene formations in the Rome area. To calibrate the isoleucine epimerization rate, we used teeth from the Isernia-La Pineta deposit, dated at approximately 0.70 m.a by K/Ar and Paleomagnetics. The chronological sequence obtained for the deposits is in close agreement with that indicated by biostratigraphic and geologic evidence. The isoleucine epimerization dates represent the first age determinations made directly on the fossil material from the Rome deposits. 相似文献