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1.
David J. Holloway 《Palaeontology》2004,47(4):1015-1036
The Monorakinae is a subfamily of the Pterygometopidae characterised by the fusion of L2 and L3 in the glabella. The resulting bicomposite lobe is expanded backwards to reach the occipital furrow, displacing L1 from contact with the axial furrow and causing the realignment of S1 to a markedly oblique orientation. The bicomposite lobe is commonly bounded adaxially by a longitudinal furrow containing three pairs of apodemal pits. The Monorakinae was probably derived from the Pterygometopinae, and includes the genera and subgenera Monorakos , Carinopyge , Ceratevenkaspis , Elasmaspis , Evenkaspis ( Evenkaspis ) and E . ( Parevenkaspis ), of which Carinopyge , Elasmaspis and Evenkaspis ( Parevenkaspis ) are known only from limited parts of the exoskeleton. Monorakines have a stratigraphical range of Caradoc–Ashgill. Their known geographical distribution in the Siberian Platform, Taimyr, the Russian Far East, and the Seward Peninsula of Alaska is restricted to areas that in the Ordovician were part of the palaeocontinents of Siberia and Arctida, which must have been connected or situated close together at that time. The occurrence of monorakines in the Taimyr Peninsula but their absence from Baltica does not support the suggestion of some workers that Taimyr was part of Baltica in the Ordovician. 相似文献
2.
描述了陕西南郑梁山上奥陶统南郑组及临湘组的三叶虫 Kweichowilla liangshanensis sp. nov.,Triarthrus sp. 及 ? Aspidaegalina liangshanensis Chen (sp. nov.).前两者产于南郑组,后者产于临湘组.Kweichowilla 属系首次在陕西上奥陶统发现,Aspidaegalina 属在我国上奥陶统也是首次见及. 相似文献
3.
《Palaeoworld》2023,32(2):252-265
Heliolitine tabulate corals are extremely rare in pre-Katian (Upper Ordovician) rocks worldwide, hindering the understanding of their origin and early evolution. Here, we systematically study new heliolitine material from the upper member (Sandbian) of the Huadan Formation in the Yunnan-Sichuan border area, Southwest China, which includes Protaraea ningnanensis, Plasmoporella kiaeri, Wormsipora sp. and Heliolites spinosus. The findings indicate that Protaraea and Heliolites are ancestral forms of coccoserids and typical tubular heliolitines, respectively, and that the absence of trabecular septa is probably a primitive feature of plasmoporellids. The refined Ordovician stratigraphy of this area implies that the coccoserid Protaraea ningnanensis Lin, 1965 from the lower member (late Darriwilian) of the Huadan Formation is the earliest known heliolitine, which further indicates that all heliolitines might have evolved from Protaraea. The comparison of Protaraea with other early tabulate corals also suggests an independent heliolitine origin from auloporinids and sarcinulinids. 相似文献
4.
Community evenness has recently received much attention, either because it is related to ecosystem functioning or because it may affect estimation of diversity. Temporal and environmental trends in diversity and evenness of trilobite communities during the Late Cambrian – Early Ordovician of the Cordillera Oriental (north‐western Argentina) are here analysed. Richness and evenness increase through time in both deep subtidal (between fair‐weather and storm wave base) and offshore (below storm wave base) communities. Two significant patterns are superimposed on this general trend: (1) the magnitude of the increase in evenness is much more pronounced in deep than in shallower settings, and (2) richness and evenness trajectories are decoupled (while a significant rise in evenness is recorded in the middle Tremadocian (Tr2), an increase in richness is delayed until the late Tremadocian (Tr3)). In contrast to expectations, a single family (Olenidae) is dominant in samples associated with this earlier rise in evenness relative to richness. Hence, this trend is explained neither by the number of families present in the communities nor by the familial identity of the most abundant taxon. Large‐scale comparisons of the timing and geographical components of these trends are restricted to the patterns recognized in Laurentian North American studies. Results from the Cordillera Oriental mirror those of Laurentia regarding the rise in both metrics in deep marine settings. Nevertheless, the timing of this increase in richness and evenness is delayed in the Cordillera Oriental, supporting the idea that palaeogeographical regions differed in the nature and timing of ecological changes. Finally, the rise in trilobite alpha‐diversity through the Late Cambrian – Early Ordovician of the Cordillera Oriental supports the idea that trilobite alpha‐diversity did not decline worldwide, suggesting that the relative decline in trilobite alpha‐diversity is most probably caused by the dilution effect. 相似文献
5.
系统描述湖北宜昌和秭归新滩晚奥陶世庙坡组球接子类及多节类三叶虫动物群中的１４种,分属于９属、７科、。根据化石保存状态、挤压变形以及个体发育特征,对前人所报道的产于本组的有关三叶早作了大量归并、转移和重新厘定,新的材料支持解释Telephiana longicephala的性双形现象。Ａtractopyge系首次在庙坡组中发现,以往它在三峡地区只见于临湘组。文中还将新疆的一个保留命名种Ｌonchodomas cf.yohi重新命名为Ｌonchodomas zhangi sp.nov.。 相似文献
6.
Abstract: A medium diversity silicified Middle Cambrian faunal assemblage occurs in an olistolith of bioclastic limestone within Silurian siliciclastic turbidites on the slopes of Arpatektyr Mountain in the eastern Alai Range, Kyrgyzstan. The fauna includes the trilobites Raragnostus cf. mirus , Altikolia kurshabica sp. nov., Corynexochina weberi , Dorypyge richthofeniformis , aff. Jincella sp., Olenoides comptus , Skreiaspis aff. spinosus and Suluktella mambetovi sp. nov. Three of these taxa ( C . weberi , O . comptus and R . cf. mirus ) are considered locally to be characteristic of the Pseudanomocarina Beds, although Pseudanomocarina itself is not present. Altikolia and Suluktella are endemic to early Palaeozoic terranes of Central Asia, Corynexochina also occurs in South China and Skreiaspis is known elsewhere exclusively from the Middle Cambrian of 'West' Gondwana. Because of preservation in full relief, the silicified trilobite fauna allows a detailed understanding of some morphological structures, related especially to trilobite enrolment, otherwise inadequately known for many Mid-Cambrian polymerid trilobites. 相似文献
7.
Beatriz G. Waisfeld Diego Balseiro 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2016,49(3):379-392
Components of biodiversity are strongly scale dependent, but the relative importance of the patterns that operate at different scales and the links between them have been overlooked. To disentangle the ecological structure of Cambro‐Ordovician trilobite assemblages from the Argentine Cordillera Oriental at different scales, we explore patterns of abundance, dominance and occupancy across the onshore–offshore profile, and through three time intervals: Furongian, earliest Late Tremadocian (Tr2), latest Middle Floian–earliest Late Floian (Fl2–Fl3). At the regional scale, single taxa are overwhelming dominant in the Furongian (Parabolina) and in the earliest Late Tremadocian (Leptoplastides). Several dominants occur in the Floian, but just one (Famatinolithus) attains high occupancy and, rarely, high dominance. In contrast, only the Furongian records highly dominated local assemblages, whereas dominance distinctly decreases among Tr2 and Fl2–Fl3 ones. Thus, when both scales of analysis are combined, an unexpected scenario becomes evident: Tr2 assemblages resemble those of the Furongian at the regional scale, but mirror those of the Floian at the local scale. These results highlight a decoupling in local versus regional structures triggered by an earlier switch in dominance in local communities and a delayed change at the regional scale. Interestingly, this decrease in local dominance matches previous analyses accounting for a coeval step‐up in local evenness, suggesting that the Tr2 appears as a pivotal interval in the reorganization of communities in the Cordillera Oriental. This scenario emphasizes that biogeographical regions witnessed different regional‐scale processes, and suggests that scaling local and regional patterns provides new insights to unravel the history of biodiversity among benthic communities. 相似文献
8.
The proximal development of Parisograptus Chen and Zhang is described from three–dimensionally preserved specimens. The unique development features an origin of proximal thecae like a string of pearls vertically upon each other on the reverse side of the rhabdosome with the dorsal sides of the initial stipes placed side by side. The development differs strongly from that found in the superficially similar Arienigraptus in which the first thecal pairs grow downwards side by side, even though the rhabdosome shapes are quite similar. It represents a first step towards the development of a completely biserial rhabdosome and eventually leads to the biserial, monopleural glossograptids. 相似文献
9.
Jesse R. Carlucci Stephen R. Westrop 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2015,48(3):309-325
There have been surprisingly few empirical investigations of the fundamental principle that the architecture of depositional sequences exerts considerable control on observed patterns of faunal distribution and replacement. In this paper, we examine trilobite associations in two sequences of the Upper Ordovician (Sandbian) Bromide Formation of southern Oklahoma. Cluster analysis and ordination of genus abundance data identified five lithofacies‐related biofacies that are also differentiated by diversity patterns. Biofacies of the transgressive system tract (TST) of successive sequences are more similar to each other than they are to biofacies in the highstand systems tract (HST) of the same sequence. This similarity likely records dominance of large, robust convex sclerites in taphonomically degraded samples from condensed, strongly winnowed grainstone and rudstone. Horizons with articulated exoskeletons of isoteline trilobites preserved by obrution deposits occur most commonly in the early HST and record behavioural aggregations. Grainstone and rudstone of the later HST are less winnowed than those of the TST and show less fragmentation and sorting of sclerites. These changes in taphonomic conditions preserve ecological patterns more clearly. In most biofacies, rarefied alpha diversity (samples) and gamma diversity (biofacies) of middle‐ and outer‐ramp HST deposits are greater than in the TSTs, and biofacies replace each other down ramp. Diversity patterns do not agree with model predictions and other data sets that indicate low beta and high alpha diversity in the TST, likely because of taphonomic degradation. Vertical replacement of biofacies is expressed by the appearance of peritidal facies in which trilobites are rare. Biofacies shifts also characterize sequence boundaries and are most profound in the inner‐ramp successions characterized by sharp facies offsets. Comparison with bathymetrically similar deposits in the Taconic foreland basin showed similar diversity trends along environmental gradients, with some differences in shallow‐water settings attributed to taphonomic differences. 相似文献
10.
本文详细描述了重庆石柱漆辽剖面奥陶系达瑞威尔阶(Darriwilian)牯牛潭组至凯迪阶(Katian)宝塔组的牙形刺序列及其对比。牙形刺序列由上而下可分为:宝塔组Hamarodus brevirameus生物带和Amorphognathus superbus生物带;大田坝组的Baltoniodus alobatus,Baltoniodus variabilis和Yangtzeplacognathus jianyeensis生物带;牯牛潭组的Yangtzeplacognathus crassus生物带和Lenodus variabilis生物带。其中Hamarodus brevirameus生物带至Baltoniodus alobatus生物带上部为凯迪阶,B.alobatus生物带下部至Yangtzeplacognathus jianyeensis生物带上部为桑比阶(Sandbian),而Yangtzeplacognathus jianyeensis生物带下部,Yangtzeplacognathus crassus生物带和Lenodus variabilis生物带归入达瑞威尔阶。根据文中所识别的牙形刺序列,该剖面显然缺失了达瑞威尔阶中上部的牙形刺生物带如Pygodus serra生物带(即Yangtzeplacognathus protoramosus和Y.foliaceus生物带),Eoplacognathus suecicus和Dzikodus tablepointensis生物带。因此,在重庆石柱漆辽剖面奥陶系牯牛潭组和大田坝组之间的地层是不连续的,存在一明显的沉积间断,缺失了相当于牯牛潭组标准剖面中上部的地层(达瑞威尔阶中上部)。而这一沉积间断所发生的时间正好与达瑞威尔中晚期全球海平面下降相吻合。 相似文献
11.
Tatiana N. Koren Vera Gorshenina Tatiana Tolmacheva 《Pal?ontologische Zeitschrift》2004,78(1):195-212
The lower and lowermost Middle Ordovician strata of the Volkhov Stage exposed in the vicinity of St. Petersburg, Russia, yield
a graptolite fauna at several stratigraphic levels, being more often confined to the mud-mound clays than to the normally
stratified, Condensed carbonates. Overall taxonomic diversity of the Volkhov graptolites is relatively low and associations
include no more than seven species in ail localities. TheTetragraptus, Didymograptus andXiphograptus species found are pandemic and have quite extensive stratigraphie ranges within the mid-Arenig Series. Based on the graptolite
zonation, the Volkhov Stage can be correlated to thePseudophyllograptus angustifolius elongatus andDidymograptus (Expansograptus) hirundo graptolite biozones of Baltoscandia and to the upperDidymograptus simulans toDidymograptus (Expansograptus) hirundo biozones of the British graptolite succession. TheIsograptus victoriae lunatus lower zonal boundary probably falls within the graptolite-bearing interval of the lower Volkhov Stage. As the result of indirect
biostratigraphic and interpretative lithological correlations, the first appearance ofUndulograptus austrodentatus at the base of the Darriwilian Stage is deemed to be close to the boundary of theMegistaspis simon andM. limbata trilobite biozones and the lowerBaltionodus norrlandicus conodont Biozone of the upper Volkhov Stage. Seven dichograptid species belonging to four genera are described, one of them,Azygograptus volkhovensis n. sp., new.
相似文献
12.
John M. Malinky 《Palaeontology》2002,45(3):511-555
Hyolith assemblages of early to mid Ordovician age in Sweden include the hyolithids Hyolithus bisulcatus Holm, H. concinnus Holm and H. innotatus Holm, which are confirmed as representatives of Hyolithes Eichwald. Dorsolinevitus Syssoiev is known from D. dispar (Holm), D. textilis (Holm) and D. vomer (Holm), and Carinolithes Syssoiev is represented by C. hospes (Holm) and C. triumvir (Holm). Sulcavitus caelatus (Holm), the type species that forms the basis for a family and even an order according to some, is redescribed; the order is suppressed. Hyolithus cymbium Holm is transferred to Stelterella gen. nov., and Theca crispata (Boll) is now the type species of Crispatella gen. nov. The unusual orthothecid Quadrotheca quadrangularis (Holm) is redescribed; the concept of Trapezotheca aemula (Holm) is emended, and Semielliptotheca dens (Holm) is transferred to Trapezotheca . Semielliptotheca Syssoiev is poorly known from only one species, S. rosmara (Holm), and that genus is now considered to be unrecognizable. Hyolithus exaratus Hadding is identified as closely related to the gastropod Lytospira norvegica Koken, and specimens of Hyolithus sp. nos 11, 12 and 13 Holm and Hyolithus sp. indet. Wiman, remain to be located. 相似文献
13.
Phylogenetic analysis of the Early and early Middle Ordovician (Tremadoc and Arenig) ostracod species of Baltoscandia suggests a polyphyletic origin for the suborder Beyrichiocopa. Binodicopes, leiocopes and eridostracans are excluded from the beyrichiocopide clade. An independent origin from the basal ostracods is suggested for the binodicopes and eridostracans. The palaeocopes form a strongly supported monophyletic clade. Within this suborder, the ctenonotellid and the tetradellid families together form a monophyletic clade. The tetradellids are paraphyletic, being a stem-group for the ctenonotellids. Nanopsis nanella , the earliest known ostracod from the Tremadoc, is a basal palaeocope. The early eridostracans Conchoprimitia and Incisua , with their uncomplicated carapace morphology, might be the most primitive ostracods. 相似文献
14.
R. M. Owens 《Palaeontology》2004,47(3):557-578
Species belonging to genera of three families of the Proetida (Proetidae, Rorringtoniidae and Toernquistiidae) are described from the upper Ashgill of southern Sweden, and the same or related species noted from the adjacent parts of northern and central Europe. Proetidae are represented by Paraproetus brevifrons (Angelin), Ogmocnemis irregularis Kielan, Ogmocnemis jaanussoni sp. nov. and Parvigena putealis sp. nov.; it is argued that all belong to the Cornuproetinae, not Tropidocoryphinae where they were previously classified. Ogmocnemis is resurrected for some Upper Ordovician species included previously in Decoroproetus . The rorringtoniid genera Rorringtonia and Madygenia are recognised for the first time in southern Sweden, and it is argued that these are probably closely related, and both are included in the same family; both are recorded for the first time from Silurian (Llandovery) strata. Zetaproetus is claimed to be a junior subjective synonym of Rorringtonia. Solariproetus , first described from north-west China, is assigned to the Toernquistiidae as a late, derived member, and S. prosthemesos sp. nov. is described from late Rawtheyan strata in the Holy Cross Mountains, Skåne and the English Lake District. Comments are given on the stratigraphical and palaeogeographical distribution of these taxa. 相似文献
15.
SYNOPSIS. It is evident from a survey of the Russian literature that many species of avian haematozoa recorded do not meet the basic criteria required by the International Code of Zoological Nomenclature. Thus 28 species of Haemoproteus and 4 species of Leucocytozoon are considered to be nomina nuda, while 1 species, Leucocytozoon turtur orientalis is a synonym of L. marchouxi. 相似文献
16.
Abstract: Twenty‐six species (nineteen of them formally named) of scutelluid trilobites belonging to eight genera are described from limestones of the lower Wenlock to Ludlow Mirrabooka Formation and its stratigraphical equivalents in the Orange district of New South Wales. Two genera, Borenoria and Mirrabooka, are new. Japonoscutellum, previously employed mainly for several species from Japan, is a globally widely distributed genus in rocks of middle Llandovery to Ludlow age and includes a number of species previously assigned to Kosovopeltis. Japonoscutellum is remarkably diverse in the faunas from Orange where it is represented by eleven species, one of them known also from Kazakhstan. Flexiscutellum and Tosacephalus are regarded as junior synonyms of Decoroscutellum and Kosovopeltis, respectively. The homology of various scutelluid cephalic structures is discussed, in particular the cephalic borders and border furrows that have routinely been misidentified; the term ‘bolus’ is introduced for the variably developed swelling that is enclosed by S1 on the glabella of most scutelluids. New species are Australoscutellum iota, A. microps, A. pulex, A. trica, Borenoria cirrita, Decoroscutellum planes, Eoscutellum annosum, Illaenoscutellum tryo, Japonoscutellum borenorense, J. crassum, J. diascetum, J. gephyricum, J. guttulatum, J. serangicum, J. strabo, Kosovopeltis trepida, K. xynon and Mirrabooka harryi. Some of these trilobites show strong affinity with species from the Kurosegawa Terrane of south‐western Japan and the Chu‐Ili Terrane of Kazakhstan, as previously reported also for the effaced Illaenina from the same limestones. Australoscutellum and Mirrabooka are presently known only from eastern Australia. The new genus Securifrons is proposed for several species previously assigned to Kosovopeltis or Eokosovopeltis from the Sandbian or Katian to Llandovery of North Greenland, Canada, Scotland, South China and New South Wales. 相似文献
17.
18.
The diversity of heterolobosean amoebae, important members of soil, marine and freshwater microeukaryote communities in the temperate zones, is greatly under-explored in high latitudes. To address this imbalance, we studied the diversity of this group of free-living amoebae in the Arctic and the Antarctic using culture dependent methods. Eighteen strain representatives of three heterolobosean genera, Allovahlkampfia Walochnik et Mulec, 2009 (1 strain), Vahlkampfia Chatton et Lalung-Bonnaier, 1912 (2) and Naegleria Alexeieff, 1912 (15) were isolated from 179 samples of wet soil and fresh water with sediments collected in 6 localities. The Allovahkampfia strain is the first representative of the genus from the Antarctic; 14 strains (7 from the Arctic, 7 from the Antarctic) of the highly represented genus Naegleria complete the ‘polar’ cluster of five Naegleria species previously known from the Arctic and Sub-Antarctic regions, whereas one strain enriches the ‘dobsoni’ cluster of Naegleria strains of diverse origin. Present isolations of Naegleria polaris De Jonckheere, 2006 from Svalbard, in the Arctic and Vega Island, in the Antarctic and N. neopolaris De Jonckheere, 2006 from Svalbard and Greenland in the Arctic, and James Ross Island, the Antarctic demonstrate their bipolar distribution, which in free-living amoebae has so far only been known for Vermistella Morand et Anderson, 2007. 相似文献
19.
