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蕉带羽叶属一新种(Nilssoniopteris hailarensis sp.nov.)化石采于内蒙古自治区海拉尔盆地的一个钻孔中(北纬47°58′,东经117°10′)。其层位属于下白垩统伊敏组。该种以其全缘的窄线形长叶为特征。叶片及脉序为带羊齿型,表皮构造为本内苏铁型。叶片着生于中脉上表面的两侧。中脉在下表面宽约3mm,但在上表面露出的宽度仅有下表面宽度的1/3。被报道的种在叶形方面与西欧威尔登植物群的 Nilssonioptetis beyrichii(Schenk)典型标本较为接近,但两者的角质层特征有明显区别。对此本文作了较详细讨论。 相似文献
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本文详细记述了陕西府谷下三叠统和尚沟组中发现的一前棱蜥类骨架。依据头骨及头后骨骼特征订立一新属种:河套五角蜥(Pentaedrusaurus ordosianus gen.et.sp.nov.)。讨论中,对原归入前棱蜥科的袁氏三台龙(Santaisaurus yuani)的系统分类位置提出了修正意见,同时建议取消黄河保德蜥(Paoteodon huanghoensis)这一名称。 相似文献
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广东茂名一新种始新世Anosteira属龟化石 总被引：3，自引：0，他引：3
1954年初,北京地质学院古生物教研室接到一批要求鉴定的标本,其中有两块较为完整的龟类化石,当即转交中国科学院古脊椎动物研究室。这两块龟化石是邹耀显、李文彬二同志于1954年6月在广东省西部茂名县九区光松林和平头岭采到的,产于已固结的泥页岩中。在光松林所采—块固结程度较强,手指很难刻划,颜色 相似文献
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我国东北地区新蚤属一新种记述及有关问题讨论 总被引：1，自引：0，他引：1
1979年从哈尔滨市一只大仓鼠(Cricetulustriton)身上采得2只未定名新蚤属蚤,1979—1983年又陆续采得此种蚤。后在复查整理以往标本的过程中,又发现1951—1959及1978年均曾采得本种。此外在吉林、内蒙和黑龙江省的几个市、县也均获得此种。经反复核查鉴定认为是新蚤属(NeopsyllaWagner,1903)一新种,命名为单齿新蚤(Neopsyllamonodenta-tiformis)新种。鉴别特征本新种属于Hopkins&Rothschild1962所定的多毛组(setosagroup),以雄性抱器不动突和可动突的形状与本组的二齿新蚤(NeopsyllabidentatformisWagner,1893)相近,但又主要以雄性第8腹… 相似文献
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<正> 羊肚菌属约有15个种,在我国发现了5—8个种。羊肚菌属的所有种均可食,它们是真菌中味道鲜美的一类菌。在考察新疆天池自然保护区时,发现小顶羊肚菌中一个新变种:小顶羊肚菌卵褐变种(Morchella angusticeps Peck var.ovoideo-brunnea Mou var.nov.)。二个在新疆未曾报道过的种:小顶羊肚菌(M.angusticeps Peck)和粗柄羊肚菌(M.crassipes(Vent.)Pers.]。 相似文献
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对采自陕西镇巴小洋剖面下寒武统西蒿坪段的似软舌螺类(hayolithelminths)化石进行了研究,描述了一新种Torellella bisulcata sp．nov．,其主要特征为：磷质管状壳体,横切面透镜状,壳管的两个宽面凸度不等,一面为弧状,另一面扁平;壳管直或微弯曲,在壳管的两个窄的侧面各具一纵向浅凹沟,壳面光滑或饰有微弱的横向纹线。简要地讨论了似软舌螺类化石的生物亲缘关系,认为迄今为止,其仍为分类位置不明的化石类别。西蒿坪段中下部产有三叶虫颊刺和颈刺,表明此段沉积地层属于下寒武统筇竹寺阶而非梅树村阶。 相似文献
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Makoto Osada Takeshige Matsutani Tadashi Nomura 《Invertebrate reproduction & development.》2013,57(3):241-251
Summary During the tail-bud stage of Ascidiella aspersa embryogenesis, the test cells or innermost cells of the egg envelope manifest locomotive activities. Light microscopy further reveals that the adhesive behaviour of test cells changes in the course of embryogenesis. Mechanical dechorionation experiments performed on 846 embryos demonstrate that up to the tail-bud stage all test cells are attached to the inner surface of the chorion. The embryo is completely devoid of test cells. At the onset of larval tunic secretion, increasing numbers of test cells settle on the embryo until all test cells adhere to it. This switch in adhesive properties is completed within 65 min. The hatched larva carries the entire complement of test cells until the onset of metamorphosis. SEM and observations show that test cells do not establish direct cell-to-cell contacts to ectodermal cells but attach to the larval tunic. 相似文献
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滇西晚石炭世一早二叠世苔藓虫 总被引：2，自引：0，他引：2
简述了4个双壳类化石组合特征及沉积环境,描述了双壳类2新属(Sichuatrigonia, Pseudoburmesia)和11新种(包括新亚种). 相似文献
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Sperm ultrastructural features of the honeycomb (foam) oysters Hyotissa hyotis, H. sinensis, and H. mcgintyi (Gryphaeidae) are described and compared with other Ostreoidea and more generally with other pteriomorphian Bivalvia. Spermatozoa of H. sinensis and H. mcgintyi (the type species of Parahyotissa Harry 1985) exhibit (1) a broad, low‐conical acrosomal vesicle; (2) subacrosomal material (very electron‐dense granular material and an almost electron‐lucent axial rod); (3) a spheroidal nucleus with a wide anterior invagination (filled with subacrosomal components); (4) a midpiece composed of four spherical mitochondria surrounding a pair of centrioles (rootlet associated with proximal centriole); and (5) a flagellum. Sperm of Hyotissa hyotis (type species of Hyotissa Stenzel 1971) differ markedly from those of H. sinensis and H. mcgintyi, in having (1) a conical acrosomal vesicle showing coarse granular texture anteriorly; (2) a very electron‐dense axial rod; (3) a barrel‐shaped nucleus with a long, narrow anterior invagination (filled with both subacrosomal components) and a basal invagination partly housing the proximal centriole; and (4) five midpiece mitochondria and no proximal centriolar rootlet. Results indicate that H. sinensis should be relocated to another genus, possibly a revised genus Parahyotissa, and also show that the sperm of H. sinensis and H. mcgintyi show many similarities to those of the Ostreidae, with the exception that the ‘axial rod’ component of the subacrosomal material is less electron‐dense than the surrounding substance (more dense in Ostreidae, as in H. hyotis). No family defining sperm features of the Gryphaeidae can be identified. 相似文献
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Two molecular protocols for the identification of mussel and scallop have been developed using specific primers targeting
the mitochondrial 16S ribosomal DNA gene and the nuclear 18S ribosomal DNA gene. Primers for the mitochondrial 16S ribosomal
DNA gene in multiplex polymerase chain reaction (PCR) protocols yielded diagnostic DNA fragments for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis (335 bp), the king scallop Pecten maximus (382 bp) and the black scallop Mimachlamys varia (398 bp). DNA from the queen scallop Aequipecten opercularis showed no consistent PCR amplification of the 16S rDNA gene. Primers for the nuclear 18S rDNA gene in standard PCR protocols
yielded similar-sized, diagnostic DNA fragments (approx. 190 bp) for the mussels Mytilus edulis, Mytilus galloprovincialis, and the hybrid Mytilus edulis/galloprovincialis, the king scallop Pecten maximus, the black scallop Mimachlamys varia, and the queen scallop Aequipecten opercularis. Both protocols have been tested with Mytilus spp., P. maximus, and 6 other bivalve species from a wide range of locations in Irish and European waters. Cross reaction of the specific
primers with DNA template from any of the 6 other bivalve species was not observed. Rapid DNA extraction using FTA Card technology
and the16S rDNA primers allowed for the detection of at least 10 mussel larvae in a subsample of natural plankton. 相似文献
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We examined the presence and location of small cardioactive peptide (SCP)‐like neuropeptides in both the central and peripheral nervous systems of D‐hinge, newly eyed, and pediveliger larvae of Crassostrea virginica. Results indicate that SCP‐like substances are present early in development (D‐hinge larvae), and that presence in the central and peripheral nervous systems increases as the larva develops toward metamorphic competence (pediveliger larvae). In addition, in newly eyed and pediveliger larvae, SCP‐like labeling is found in a varying number of neurons within all central ganglia, with the possible exception of the accessory ganglia. Varicose labeling of axons is also documented within the ganglia, commissures, and connectives, as well as in peripheral nerves. Peripheral tissues innervated by axons exhibiting SCP‐like immunoreactivity include the velum, foot, esophagus, mantle, and various musculatures. As indicated by the location of SCP‐like labeling in various organs and tissues, it is likely that these neuropeptides modulate muscle contraction or ciliary beating in molluscan larvae such as those of C. virginica. 相似文献
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Lower Campanian siliceous sponges from epicontinental deposits of the Subhercynian Cretaceous Basin in Germany contain amygdaloidal depressions which are distinguished as a new ichnospecies of the ichnogenus Cuenulites. These bioerosion traces are interpreted as borings of semi-endolithic bivalves, produced without significant rotation movement, probably mostly by chemical action. As there are no signs of tissue reaction in the bored sponges, the structure is considered to be produced post mortem to the sponge, probably in a foreshore-shoreface setting, with redeposition offshore. 相似文献
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Daniel A. Driscoll Alexander M. Dunhill Thomas L. Stubbs Michael J. Benton 《Palaeontology》2019,62(1):51-75
The quality of the fossil record affects our understanding of macroevolutionary patterns. Palaeodiversity is filtered through geological and human processes; efforts to correct for these biases are part of a debate concerning the role of sampling proxies and standardization in biodiversity models. We analyse the fossil record of mosasaurs in terms of fossil completeness as a measure of fossil quality, using three novel, correlating metrics of fossil completeness and 4083 specimens. A new qualitative measure of character completeness (QCM) correlates with the phylogenetic character completeness metric. Mean completeness by species decreases with specimen count; average completeness by substage varies significantly. Mean specimen completeness is higher for species‐named fossils than those identified to genus and family. We consider the effect of tooth‐only specimens. Importantly, we find that completeness of species does not correlate with completeness of specimens. Completeness varies by palaeogeography: North American specimens show higher completeness than those from Eurasia and Gondwana. These metrics can be used to identify exceptional preservation; specimen completeness varies significantly by both formation and lithology. The Belgian Ciply Formation displays the highest completeness; clay lithologies show higher completeness values. Neither species diversity nor sea level correlates significantly with fossil completeness. A generalized least squares (GLS) analysis using multiple variables agrees with this result, but reveals two variables with significant predictive value for modelling averaged diversity: sea level, and mosasaur and plesiosaur‐bearing formations (the latter is redundant with diversity). Mosasaur completeness is not driven by sea level, nor does completeness limit the mosasaur diversity signal. 相似文献
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本文介绍下辽河西部坳陷下第三系锦128井5块样品生物标志物(主要是正烷烃及δ~(13)C值)的研究。其正烷烃碳数分布范围为C_(15)—C_(25),主峰碳为C_(15)、C_(16)或C_(17)。C_(21)+C_(22)/C_(28)+C_(29)比值很大,表明这些岩样有机质来源可能和海产藻类群落有关。5块样品OEP值依次分别为1.2487,0.9569,0.9394,0.9905和0.9889非常符合生油岩0.9—1.2的标准数值。正烷烃碳数范围主要在C_(10)—C_(25),苯馏分表现出低碳和中碳芳香烃优势,说明锦128井①—⑤样品属于高成熟度的油层,特别是J128-1,2,5的层位。以上这些数值正和沟鞭藻化石反映的油源丰度和成熟度相一致。本文结果证明用生物标志物判别石油母质来源、油层对比、油气丰度和成熟度乃是很有效的方法。 相似文献
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JOHN M. HEALY PAULA M. MIKKELSEN † RÜDIGER BIELER fls 《Zoological Journal of the Linnean Society》2008,153(2):325-347
The systematic position and affinities of the marine bivalve genus Hemidonax (Heterodonta, Veneroida) are investigated using comparative sperm ultrastructure, with particular focus on the various groups to which this genus has been assigned [Donacidae (Tellinoidea), Cardiidae (Cardioidea) and Crassatellidae (Crassatelloidea)]. Ultrastructural examination (using transmission electron microscopy) reveals that Hemidonax pictus produces sperm of the aquasperm type, with a short, rounded-conical acrosomal vesicle, a short, barrel-shaped nucleus, a short midpiece (composed of two centrioles and four surrounding mitochondria) and a flagellum containing a conventional 9 + 2 pattern axoneme. The acrosomal vesicle exhibits a wedge-shaped, highly electron-dense, basal ring component, and less dense anterior component (including a thin, electron-lucent layer apically, which may prove to be a useful apomorphy for Hemidonax ). A loose, granular deposit of subacrosomal material is located within a narrow invagination traversing most of the length of the vesicle. Comparison with sperm of other heterodont bivalves shows no close connection between Hemidonax and the Donacidae (Tellinoidea) or with the Crassatellidae (or other crassatelloideans). Although certain Veneridae (Veneroidea) and Cardiidae (Cardioidea, especially Fragum ) show much better conformity in sperm morphology to that observed in Hemidonax , no complete match could be found among studied taxa. We conclude that Hemidonax should be retained in its own, previously introduced family Hemidonacidae, and the latter be placed incertae sedis within the Euheterodonta. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 153 , 325–347. 相似文献
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Masahiro Nakaoka 《Population Ecology》1993,35(2):199-213
Long-term variation in recruitment was estimated by constructing projection matrices for a marine bivalve, Yoldia notabilis, at two stations in Otsuchi Bay, northeastern Japan, and the effects of its variation on population dynamics were examined using a simple matrix model. The matrix model was developed from the Leslie matrix, in which the population growth rate λ was expressed as a function of recruitment rate r0. The equilibrium recruitment rate rs, or the recruitment rate required to maintain population at constant size (λ=1), was expressed by the reciprocal of the reproductive value of a newly recruited individual. The estimates of rs for the field population were lower at the shallower station than at the deeper station, reflecting higher survivorship and fecundity. Past recruitment rate estimated both by the field samplings for 3 years and by the back-calculation from the current age structure for over 10 years showed large yearly variation, ranging between 0 and 58.6×10−4. The estimates were larger than rs, and hence, large enough to increase population size (λ>1) only in approximately one-third of the estimated years. This suggests that the population has been maintained by occasional successful recruitment occurring once every few years. 相似文献