短吻贫齿龙(双孔亚纲:海龙目)的新材料及补充研究

记述了产自贵州关岭法郎组瓦窑段(上三叠统)短吻贫齿龙一新材料。新标本头后骨骼十分完整,使我们对该海龙的全身骨骼形态有了一个完整的认识,尤其是澄清了其肩带及前、后肢的解剖学特征。短吻贫齿龙牙齿稀少且局限于上、下颌的前端,以及末端指/趾骨(爪)扁平等性状表明,该种不是纯粹的肉食动物。依据新材料,短吻贫齿龙在局部形态上存在个体变异,并确认后肢趾趾式(2-3-4-5-5)可作为该海龙的特征之一。     

ANNUAL PRODUCTIVITY AND EXTRACELLULAR RELEASE OF DISSOLVED ORGANIC COMPOUNDS BY THE EPIBENTHIC ALGAL COMMUNITY OF A BRACKISH MARSH1

Annual productivity and excretion of organic compounds by epibenthic algae in a coastal Texas marsh were investigated using ¹⁴C techniques. Over the course of two years, productivity and extracellular release were measured bimonthly to assess the environmental factors affecting seasonal patterns. Annual productivity was estimated to be 71 gc·m^?2, approximately 10% of the estimated net aerial productivity of the grass canopy in this area. The percentage of photoassimilated carbon released was fairly constant, and the rate of excretion appeared to be primarily dependent upon the rate of carbon fixation. Greater rates of release were observed with high salinity, low soil moisture conditions. It was estimated that up to 10% of the DOC in adjacent tidal creek water could be produced by this community and could represent an important source of nutrients for consumers in the system.     

辽宁下白垩统九佛堂组伊克昭龙一新种

伊克昭龙 (Ikechosaurus)是一类长吻的离龙类 ,以前根据内蒙古的材料建立了孙氏种 (I.sunailinaeSigogneau Russell,1 981 )及高氏种 (I.gaoiL櫣ｅｔａｌ.,1 999)。根据蒙古的材料建立的TchoiriamagnusEfimov ,1 979也于 1 983年被原作者归入本属。本文记述了辽宁义县皮家沟九佛堂组新发现的一个近于完整保存的骨架 (中国科学院古脊椎动物与古人类研究所标本编号 :IVPPV 1 32 83) ,并建立一新种 :皮家沟伊克昭龙 (Ikechosauruspijiagouensissp .nov .)。新种以下列特征区别于伊克昭龙其他种 :轭骨前伸约至泪骨之半 ;眶间距小于眼眶短径 ;眶后骨与后额骨不愈合 ;髂骨片前突不发育 ,颈区不收缩 ;四肢中桡胫骨与肱股骨之比相对较小。另外其荐前椎数目与孙氏种相同 ,为 2 5枚 ,比鳄龙属 (Champsosaurus)少 1枚 ;坐骨明显比孙氏种短 ;桡肱骨长度之比为 0 .5 8,胫股骨长度之比为 0 .60 ,在所知新离龙类 (Neochoristodera)中属最小 ;前肢腕骨至少 7块 ,后肢跗骨至少 6块 ;指 /趾式均为 2 3 4 4 3。在正型标本中其第二远侧跗骨在左右脚中不对称。提出眶后骨与后额骨的愈合与分离以及轭骨眶后支发育程度不能作为Simoedosaridae和鳄龙科间的鉴别特征 ;股骨内转子与股骨头分离不该作为高氏种的鉴定特征 ;新离龙类?     

HISTORICAL BIOGEOGRAPHY OF THE BANANAQUIT (COEREBA FLAVEOLA) IN THE CARIBBEAN REGION: A MITOCHONDRIAL DNA ASSESSMENT

We analyzed mitochondrial DNA (mtDNA) restriction-site variation in bananaquit (Coereba flaveola; Aves, Coerebinae) populations sampled on 12 Caribbean islands and at 5 continental localities in Central America and northern South America. Multiple fixed restriction-site differences genetically defined several regional bananaquit populations. An mtDNA clade representing all Jamaican bananaquits was the most divergent; the estimated average sequence divergence (d_xy) between Jamaican and all other mtDNA haplotypes surveyed was 0.027. Three groups of populations, representing Central America, northern South America, and the eastern Antilles (Puerto Rico to Grenada) were nearly equally differentiated among themselves (average d_xy = 0.014), and may represent a single, recent range expansion. Within the eastern Antilles, three geographically restricted haplotype groups were identified: Puerto Rico, north-central Lesser Antilles (U.S. Virgin Islands to St. Lucia), and Grenada–St. Vincent. The evolutionary relationships of these groups were not clear. Genetic homogeneity of the island populations from the U.S. Virgin Islands to St. Lucia suggested a recent spread of a specific north-central Lesser Antillean haplotype through most of those islands. Haplotype variation across this region indicated that this spread may have occurred in two waves, first through the southernmost islands of St. Lucia, Martinique, and Dominica, and more recently from Guadeloupe to the north. The geographic distribution of mtDNA haplotypes, and of bananaquit populations, suggests periods of invasiveness followed by relative geographic quiescence. Although most genetic studies of bird populations have revealed homogeneity over large geographic areas, our findings provide a remarkable counterexample of strong geographic structuring of mtDNA variation over relatively small distances. Furthermore, although the mtDNA data were consistent with several subspecific distinctions, it was clear that named subspecies do not define equally differentiated evolutionary entities.     

A GREEN DINOFLAGELLATE WITH CHLOROPHYLLS a and b: MORPHOLOGY,FINE STRUCTURE OF THE CHLOROPLAST AND CHLOROPHYLL COMPOSITION1

A green-colored marine unicell has been grown in unialgal culture and its morphology, chloroplast fine structure, and chlorophyll composition investigated. The organism is typical of dinoflagellates in its shape, flagellation, nucleus, mitochondria, and trichocysts. It is similar to Gymnodinium but possesses fine body scales. Chloroplasts and two kinds of vesicles bounded by double membranes, but no organelles obviously identifiable as nuclei or mitochondria, are associated in ribosome-dense cytoplasm separated by a double membrane from the dinophycean cytoplasm. The chloroplasts are unlike any previously reported for dinoflagellates. Each is enclosed by an envelope consisting of a double membrane. Chloroplast lamellae consist of three appressed thylakoids. Interlamellar pyrenoids are present. Pigment analysis reveals chlorophylls a and b but not chlorophyll c. It seems likely that the organism is an undescribed dinoflagellate containing an endosymbiont with chlorophylls a and b and that the reduction of the endosymbiont nucleus and mitochondria has permitted a more initmate symbiosis.     

EVALUATION OF THE ALASKA HARBOR SEAL (PHOCA VITULINA) POPULATION SURVEY: A SIMULATION STUDY

We used simulation to investigate robust designs and analyses for detecting trends from population surveys of Alaska harbor seals. We employed an operating model approach, creating simulated harbor seal population dynamics and haul-out behavior that incorporated factors thought to potentially affect the performance of aerial surveys. The factors included the number of years, the number of haul-out sites in an area, the number and timing of surveys within a year, known and unknown covariates affecting haul-out behavior, substrate effects, movement among substrates, and variability in survey and population parameters. We found estimates of population trend were robust to the majority of potentially confounding factors, and that adjusting counts for the effects of covariates was both possible and beneficial. The use of mean or maximum counts by site without covariate correction can lead to substantial bias and low power in trend determination. For covariate-corrected trend estimates, there was minimal bias and loss of accuracy was negligible when surveys were conducted 20 d before or after peak haul-out attendance, survey date became progressively earlier across years, and peak attendance fluctuated across years. Trend estimates were severely biased when the effect of an unknown covariate resulted in a long-term trend in the fraction of the population hauled out. A key factor governing the robustness and power of harbor seal population surveys is intersite variability in trend. This factor is well understood for sites within the Prince William Sound and Kodiak trend routes for which at least 10 consecutive annual surveys have been conducted, but additional annual counts are needed for other areas. The operating model approach proved to be an effective means of evaluating these surveys and should be used to evaluate other marine mammal survey designs.