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1.
Deep-water trawl surveys on seamounts around New Caledonia yielded62 specimens of the little-known genus, Scaeurgus. Members ofthis genus of octopuses typically occur at depths of 200–500m in temperate and tropical latitudes worldwide. Prior to thisstudy, Scaeurgus was considered to contain one to two species.The new material from New Caledonia contained a surprising diversityof Scaeurgus species from a small area: three distinct new speciesare described and limited material of a further two taxa isreported. A pygmy member of this genus is reported for the firsttime. Distributions of these new taxa are consistent with reportsof high endemism on the seamount systems in this region. Fifty-eightof the 62 specimens were collected from seamounts, with fourof the five taxa unique to a single seamount. (Received 12 January 2004; accepted 28 January 2005)  相似文献   

2.
A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstätten, but lobopodian phosphatized plates are found worldwide as typical components of Cambrian small shelly fossil assemblages (SSF). Details regarding intraspecific and ontogenetic variation in lobopod plates are elusive, and the lack of details of ornamentation in Lagerstätte specimens does not minimize the problem. We document here an assemblage of well‐preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny.  相似文献   

3.
试谈我国鹅膏菌的分类研究*   总被引:3,自引:0,他引:3  
杨祝良 《菌物学报》2000,19(3):435-440
在过去的一百余年中,国内外菌物学家对我国鹅膏菌属(Amanita)真菌进行了大量采集和分类研究。迄今为止,在菌物学文献中已为我国记载了近100种(含亚种、变种和变型)鹅膏菌,然而,其中许多是原描述于欧洲或北美的种类,它们在我国是否确有分布尚需开展深入研究。近几年来,作者对采自我国的部分鹅膏菌标本与欧美相似种的标本进行了比较研究,发现两者虽在外貌上有相似之处,但在内部结构上却有较大差别,在分子生物学方面也同样存在差异。若把它们作为同一分类单元处理似不恰当。我国幅员辽阔,森林、植被类型多样,众多与鹅膏菌形成外生菌根的树种为我国、东亚或东南亚的特有种,在它们长期的协同进化中,可能形成了不少特殊或亚洲的特有鹅膏菌。为能如实反映我国鹅膏菌的生物多样性,首先必须加强野外调查,在野外对子实体的形态及各部位的颜色进行仔细而准确的描述、拍照和绘图;其次对干燥良好的标本进行可靠的形态学、解剖学研究;此外,比较研究欧美相似种的标本也是十分必要的。本文所讨论的问题,在我国蘑菇目(Agaricales)其它类群的分类研究中可能也是值得注意的。  相似文献   

4.
The two genera Neostapfia and Orcuttia, recognized as being closely allied and sharing unusual features, are treated as the sole members of the tribe Orcuttieae. Neostapfia is monotypic; Orcuttia comprises eight taxa, six of which are universally treated as species, and two as varieties. Studies reported here are based on field work throughout the ranges of these two genera and examination of 550 herbarium specimens. Chromosome counts and seed protein analyses for all taxa are presented. These data indicate that each taxon is worthy of specific status and that Orcuttia, as traditionally treated, consists of discordant elements. It is concluded that a more satisfactory taxonomy results when this group is split into two genera. A new genus, Tuctoria, is described, and the combinations T. fragilis (Swallen) J. Reeder, T. greenei (Vasey) J. Reeder, and T. mucronata (Crampton) J. Reeder are proposed.  相似文献   

5.
There are few studies dedicated to species of the Order Parmales all over the world. All 12 taxa described are part of the marine ultraplankton (less than 5 μm). Analysis of filtered samples from the Gulf of Tehuantepec yielded specimens of two taxa of the group. One is a new species, belonging to the genus Tetraparma. Tetraparma insecta sp. nov. is solitary and spherical (2.8–3.8 μm diameter), and all plates lack ornamentations or knobs, the walls are smooth, and only the plate junctions are seen. The shield plates are convex and show a conspicuous rim, some of them with an indentation. This species shows superficial similarities with Tetraparma pelagica, the other species described of the genus, and is very similar to siliceous forms, previously found, with no formal name. The other species is the taxon Triparma laevis form mexicana (Kosman) stat. nov., earlier described for Mexican waters, which has an irregular ala, the shield plates have knobs at the center, the triradiate plates show a “Y”‐shaped keel, and the walls of plates and ala show minute granules. Tetraparma insecta was distributed widely in the study area and was relatively abundant, reaching a density of 4 × 104·L?1, with an evident preference for subsurface waters (10–20 m depth), whereas T. laevis form mexicana was rare and scarce. Both species seem to be restricted to tropical–subtropical waters. We discuss the taxonomy of Parmales, especially concerning the category of subspecies within the group. Parmales is a widespread group in cold and tropical waters.  相似文献   

6.
The arthrodires of the Eifelian Brandenberg Group of Hagen-Ambrock and Lasbeck (Northwest Germany) are described. A new tuberculated holonematid arthrodire (Holonema bruehni n. sp.) is represented by plates of the trunk shield and some plates of the head region. The tuberculation is here regarded as the plesiomorphic character of the Holonematidae compared to an ornamentation of ridges in advanced genera. This agrees with the stratigraphical occurrence of the new form. Additionally, several other plates belonging to at least three different taxa of coccosteid arthrodires have been found. Despite the absence of complete skeletons, the placoderm fauna is more diverse than the fauna of the classical Scottish Eifelian localities.  相似文献   

7.
A study was made of 30 apparently similar microsporangiate cone specimens of the lycopsid fructification Lepidostrobus found in coal balls of Middle Pennsylvanian age from Illinois and Kansas. None of these specimens was a complete cone, but at least 19 were large enough and well enough preserved to provide information regarding variation both within one cone and among several specimens. The data obtained substantiated the original assumption that all 30 specimens represented one species. Attempts to equate this one species with any of the similar, previously described North American taxa, Lepidostrobus coulteri, L. pulvinatus and Lepidocarpon magnificum-microsporangiate form, and the British taxon Lepidostrobus oldhamius, including the forms (α), (β), (γ) and pilosus, revealed that no significant differences existed among any of these taxa. Furthermore, all characteristics described for these taxa were referable to, and well within the range of variation of, the one species here analyzed. Differences among the taxa were found to represent only differences in maturation or normal variation. All these taxa are, therefore, conspecific and are assigned to one species which by priority is named Lepidostrobus oldhamius. The common association of the megasporangiate Lepidocarpon lomaxi with all these miorosporangiate cones, now recognized as representing the single taxon Lepidostrobus oldhamius, is strong evidence for the probability that Lepidocarpon lomaxi and Lepidostrobus oldhamius were produced by the same parent plant species.  相似文献   

8.
Holasteroids are a major clade of irregular echinoids that today is confined to the deep-sea, but which has a rich fossil record extending back to the start of the Cretaceous Period. A cladistic analysis of this clade, encompassing the great majority of living and fossil genera, is undertaken based on new data on test architecture. The classification of the group is reviewed and a new hierarchical scheme is proposed. The highly atypical apical disc structure of pourtalesiid holasteroids is discussed and critical data for understanding its plate homologies are provided by the most primitive pourtalesiid, the Late Cretaceous Galeaster . This supports the idea that plates previously identified as posterior genital plates in pourtalesiids are in fact ocular plates II and IV. An evolutionary tree for holasteroids is constructed by calibrating the cladogram against the stratigraphic record. This is then used to examine how holasteroid diversity and ecology have changed through time. Holasteroids have migrated into the deep-sea at least four times independently. Three of these lineages can be traced back to sister taxa living in deep-water continental shelf environments in the Late Cretaceous–early Tertiary, while a fourth represents a very much younger migration event, possibly Late Miocene in age.  相似文献   

9.
The Middle Jurassic (Bathonian) turtle material from the Mammal Bed at Kirtlington, Oxfordshire, England, has recently been tentatively referred to the Pleurosternidae, although the known synapomorphies of this clade were absent from the specimens. Here we present new evidence from shell bone histology that corroborates reports of pleurosternids at Kirtlington and further reveal that two different histomorphs (= two different taxa) are present in this locality. The first histomorph presents the distinctive histological structure of pleurosternids, which is described herein for the first time: the external cortical bone layers are differentiated into an inner zone of coarse, irregularly interwoven structural fibre bundles and an outer fine-fibred zone. The second histomorph has a more plesiomorphic structure and can only be assigned to Cryptodira indet. A morphological reassessment of the Kirtlington material fails to recognize two different taxa and shows that only sparse evidence supports the presence of pleurosternids in this locality. Shell bone histology thus appears as a powerful tool to study poorly preserved specimens and may in some case (like with pleurosternids) help resolve phylogenetic relationships. According to our results, the stratigraphic appearance of the Pleurosternidae is adjusted from the Kimmeridgian (Late Jurassic) to the Bathonian (Middle Jurassic), which significantly reduces the ghost lineage of Paracryptodira.     Bone histology, turtles, Paracryptodira, Pleurosternidae, Middle Jurassic, Kirtlington.  相似文献   

10.
Abstract:  A phylogenetic analysis of reproductive and oological (egg) traits of theropod taxa allows determination of the sequence in which these traits evolved in Theropoda. Our results indicate that several avian reproductive traits, such as adults sitting on eggs, asymmetrical eggs, unornamented eggshell surface, and complex eggshell ultrastructure, were already present in non-avian maniraptorans, and could have evolved in more basal theropods. In addition, non-avian maniraptorans laid two eggs at a time and orientated their eggs subvertically or subhorizontally in their nests, features not retained by neornithine birds. Based on our cladistic analysis it is also possible to infer the phylogenetic affinity of ootaxa of unknown parentage: Protoceratopsidovum was laid by a maniraptoran more derived than oviraptorids, and Parvoolithus probably belonged to a Cretaceous bird. Finally, our analysis reveals that many of the high-level categories of egg parataxonomy (morphotypes and basic types) are unnatural groupings (i.e. non-monophyletic). We recommend that these high-level categories be abandoned because oofamilies are sufficient to categorize egg taxa.  相似文献   

11.
Icon-like diagrams are used to summarize the anatomical patterns observed in leaf cross sections of 30 taxa of Festuca subgg. Festuca and Leucopoa occurring in western North America. Measurements of four variables, notes on the degree of development and the position of sclerenchyma, along with distribution maps of 24 native taxa, are presented. Twenty-nine diagrams were created from the synthesis of at least ten leaf-section drawings based on five plants chosen from across the geographic range of each taxon (fewer suitable specimens were obtained for two taxa). A key based on data collected in this study allows identification of species in subg. Festuca. Geographic distribution is more reliable than leaf anatomy for separating taxa in subg. Leucopoa.  相似文献   

12.
Abstract: We document here a new taxon of sphenodontian, Whitakersaurus bermani gen. et sp. nov., that is also the most complete sphenodontian fossil from the Upper Triassic Chinle Group in the south‐western USA and the first Chinle sphenodontian represented by more than a single fragmentary dentulous element. The holotype was recovered during preparation of block C‐8‐82 from the famous Coelophysis (Whitaker) quarry at Ghost Ranch, New Mexico, and is the most complete small vertebrate recovered from the quarry. Detailed lithostratigraphy and geologic mapping demonstrate that the Whitaker quarry is in the Rock Point Formation of the Chinle Group, so Whitakersaurus is the first sphenodontian reported from this unit. Records of the phytosaur Redondasaurus at the quarry and elsewhere in the Chinle Group demonstrate that the quarry, and thus Whitakersaurus, is of Apachean (late Norian–Rhaetian) age. The sphenodontian specimen consists of incomplete left and right dentaries, a partial left? maxilla?, and impressions of a probable palatal element, all of which preserve multiple teeth. Whitakersaurus is distinct from other sphenodontians in possessing a unique combination of the following features: marginal dentition pleurodont anteriorly and posteriorly acrodont; pronounced heterodonty in dentary, with as many as 15 smaller, peg‐like teeth anteriorly and several larger, posterior teeth that are conical and striated; faint radial ornamentation of posterior tooth crowns; presence of c. 19 dentary teeth; and absence of a distinct flange on posterior teeth. Numerous other details distinguish it from both more primitive and more derived taxa. Whitakersaurus, therefore, helps to document further mosaic evolution and an extensive diversification event of sphenodontians during Triassic time. Although sphenodontian taxa are relatively easily recognized, widely distributed, and common small‐ or microvertebrate fossils, the long stratigraphic ranges of taxa known from multiple specimens hinders their utility as index fossils with which to correlate strata across Pangaea.  相似文献   

13.
14.
Phylogenetic analyses of 18S rDNA gene data for Choreonema thuretii (Corallinales, Rhodophyta) and available data for other coralline red algae indicated that Choreonema belongs to the same lineage as other taxa of Corallinales possessing tetra/bisporangial conceptacles with multiporate plates. These results, when integrated with extant morphological/anatomical data, ultrastructural data, and taxonomic data led to the conclusion that all taxa of Corallinales possessing multiporate conceptacles belong to a distinct family, the Hapalidiaceae. Recognition of the Hapalidiaceae as a distinct family was supported both phylogenetically and phenetically. The Hapalidiaceae includes those taxa of Corallinales whose tetrasporangia produce zonately arranged spores and whose tetra/bisporangia are borne in conceptacles, produce apical plugs, and develop beneath multiporate plates. The Hapalidiaceae includes the subfamilies Choreonematoideae, Melobesioideae, and Austrolithoideae, formerly placed in the Corallinaceae sensu lato . The Choreonematoideae lack cell connections between adjacent vegetative filaments and have a multiporate plate that is acellular at maturity, consisting only of a calcium carbonate matrix. The Austrolithoideae and Melobesioideae both have cellular pore plates; taxa of Melobesioideae have cell fusions between cells of adjacent vegetative filaments, whereas taxa of Austrolithoideae lack cellular connections between adjacent vegetative filaments. Inclusion of the Austrolithoideae in the Hapalidiaceae was based entirely on morphological/anatomical evidence; molecular evidence currently is lacking. Relevant historical and nomenclatural data are included.  相似文献   

15.
庭藤种综内分类群间变异式样的相关性   总被引:2,自引:0,他引:2  
在种子植物中,种内的分化类型之呈连续的数量性状变异式样者屡见不鲜。毛叶石楠Photinia villosa(Thunb.)DC[1]、短葶山麦冬Liri-ope muscari (Decne.)Bailey[2]和胡枝子Lespedeza bicolor Turcz.[3]就是很好的例证。  相似文献   

16.
A new armoured marine tardigrade, Nodarctus hallucis gen. et sp. nov., is described from specimens collected from sandy beaches of Haterumajima, Ishigakijima and Okinawajima Islands, Ryukyu Archipelago, Japan. It is a member of the rare family Renaudarctidae, which is characterized by a stocky body with dorsal and ventral plates and stumpy legs with digits, claws and accessory filaments. However, the collected animals have prominent characters that differ from the two known species of the family: subdivided dorsal segmental plates I–III lacking lateral processes, an acute caudal spike, indented sensory plates, short spikes and peculiar papillae on legs I–III, basal spikes of legs IV and only two digits on legs IV. These differences justify the erection of a new genus and species for the animal. Morphological affinities with other marine taxa, the function of the leg papillae and the distribution pattern of the new species are discussed.http://zoobank.org/urn:lsid:zoobank.org:pub:041878AA-B437-45BF-80E3-32591D21D965  相似文献   

17.
Abstract:  A new cinctan echinoderm, Graciacystis ambigua gen. et sp. nov. from Cambrian Series 3 rocks of Spain, is described based on more than 100 articulated specimens that range from 6 to 14.5 mm in thecal length. This material shows that Graciacystis ambigua, while plastic in thecal shape, is highly conservative in its thecal construction, with a fixed number of marginal plates and very limited addition of plates in the stele and ventral membrane through ontogeny. Ventral swellings on marginal elements are absent from the smallest specimens and become gradually more marked during growth. A cladistic analysis shows Graciacystis to be a basal cinctan, more derived than Sotocinctus and the Trochocystitidae and as sister group to a large clade formed by Sucocystidae + Gyrocystidae. The determinate growth pattern seen in Graciacystis seems to be the general pattern for all cinctans.  相似文献   

18.
A key question in palaeontology is whether the fossil record taken at face value is adequate to represent true patterns of diversity through time. Some methods of assessing data quality have depended on the commonly observed covariation of palaeodiversity and fossiliferous formation counts through time, based on the assumption that the count of formations containing fossils, to a greater or lesser extent, drives diversity; but what if diversity drives formations? Close study of two fossil records, early tetrapods (Devonian–Jurassic) and dinosaurs, shows how the relationship between new taxa and new fossiliferous formations varies through research time. Initially, each new find represents a new fossiliferous formation and discovery follows the ‘bonanza’ model (fossils drive formations). In unexplored parts of the world, new taxa are identified frequently in new regions/formations. Only after time, in well‐explored continents such as Europe and North America, does collecting style switch to a mix of exploration for new formations and re‐sampling of known fossiliferous formations. Data are most striking for dinosaurs, where the Triassic–Jurassic record largely comprises finds from Europe and North America, where new formation discoveries reached their half‐life in 1914. This contrasts with the Cretaceous, which is dominated by rapidly rising discoveries from regions outside Europe and North America and the formation half‐life for these ‘new’ lands is 1986, showing that 50% of new Cretaceous dinosaur‐bearing formations were identified only in the past 30 years. The relationship between dinosaur‐bearing formations and palaeodiversity then combines three signals in variable amounts, reflecting the original diversity (relative abundances of particular taxa in different formations), redundancy (new fossiliferous formations accruing because of new fossil finds) and sampling (intensity of exploration for new fossiliferous formations, and of search within already‐sampled formations). For fossil vertebrates at least, formation counts of various kinds are poor predictors of sampling, missing, for example, the bonanza samples of Lagerstätten such as the Yixian Formation in China: thousands of specimens, dozens of species, but counted as one formation. These observations suggest that formation count cannot be regarded as an unbiased metric of sampling.  相似文献   

19.
Abstract:  A new semionotiform fish, Isanichthys palustris gen. et sp. nov., is described from the Late Jurassic – Early Cretaceous Phu Kradung Formation, north-east Thailand. I. palustris is known from a single, nearly complete specimen found alongside abundant Lepidotes specimens at the Phu Nam Jun locality. I. palustris shows a mixture of semionotid-like characters, such as the pattern of cheek ossifications, and lepisosteid-like characters, such as the body shape and a dorsal fin opposed by an anal fin. I. palustris possesses only some of the characters currently used to define the Semionotidae. Cladistic analyses including various semionotid and gar taxa, together with Amia calva and Leptolepis coryphaenoides , suggest that the Semionotiformes (Lepisosteidae and 'Semionotidae') form a monophyletic clade, but the 'Semionotidae' taxa form an unresolved polytomy. The relationships between Semionotiformes, Halecomorphi and Teleostei are unresolved. When restricted to the best-known taxa, however, the analysis shows the monophyly of the Semionotidae sensu stricto ( Semionotus + Lepidotes ) and a sister-group relationship between halecomorphs and teleosts. These last two results are regarded as the preferred hypothesis for further studies. I. palustris is the only known example of a predaceous, probably piscivorous, 'semionotid'. It illustrates the great diversity and ecological adaptation of the semionotiforms during the Late Jurassic – Early Cretaceous. We question the phylogenetic relationships of 'ancient fishes' founded on molecular-based trees because we suspect that the use of very few Recent taxa as representatives of previously diverse lineages is an inevitable, but important, bias in the construction of such trees.  相似文献   

20.
A new camuropiscid arthrodire, Latocamurus coulthardi gen. et sp. nov., is described from the Upper Devonian Gogo Formation, Western Australia. Latocamurus , known from two complete specimens, is recognized as a camuropiscid by its narrow, spindle-shaped armour, deep postnasal plates participating in the orbits, preorbital plates which meet mesially, cheek unit firmly sutured to skull roof, posterior check plates tightly interconnected and much reduced, and the robust durophagous dentition. It is characterized by its downturned snout, broad, flat rostral plate, and narrow, deep parasphenoid. It is placed phyletically as the plesiomorphic sister taxon to all other camuropiscids which are more derived in having, inter alia , an anterior lateral plate which anteriorly contacts the anterior ventrolateral plate and pointed rostral plates. The family Camuropiscidae Dennis & Miles 1979b is redefined to incorporate features of the new genus. Camuropiscids and Incisoscutum are closely related by features of the postnasal plate and cheek.  相似文献   

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