A hierarchical classification of freshwater mussel diversity in North America

Aim North America harbours the most diverse freshwater mussel fauna on Earth. This fauna has high endemism at the continental scale and within individual river systems. Previous faunal classifications for North America were based on intuitive, subjective assessments of species distributions, primarily the occurrence of endemic species, and do not portray continent‐wide patterns of faunal similarity. The aim of this study is to provide an analytical portrayal of patterns of mussel diversity in a hierarchical framework that informs the biogeographical history of the fauna. Location The study considered the mussel fauna of North America from the Rio Grande system northwards. Methods Patterns of mussel faunal similarity in 126 river systems or lake watersheds across North America were examined. The dataset was developed from the literature and consisted of recent species presence/absence (282 species) in each drainage unit; subspecies were not included. Patterns of mussel diversity were examined with hierarchical cluster analysis, based on a pairwise distance matrix between all drainage units. Results Cluster analysis revealed 17 faunal provinces within four major faunal regions: Mississippian, Atlantic, Eastern Gulf and Pacific. The Mississippian Region dominates the North American fauna with 11 provinces, including five not recognized by previous classifications: Mississippi Embayment, Upper Mississippi, Great Plains, Ohioan and Pontchartrain–Pearl–Pascagoula. Within the Eastern Gulf Region (containing three provinces), the Escambia–Choctawhatchee Province is distinctive from the Apalachicolan Province, under which it was previously subsumed. Patterns of diversity in the Atlantic Region (two provinces) and Pacific Region (one province) were similar to previous classifications. Main conclusions The classification proposed in this study largely corroborates earlier schemes based on the occurrence of endemic species but identifies additional heterogeneity that reflects unique assemblages of widely distributed species. The study proposes a hierarchical structure that illustrates relationships among these provinces. Although some provinces in the Mississippian Region have high endemism, all Mississippian provinces share a group of widely distributed species. The Atlantic and Eastern Gulf regions have distinctive, endemic faunas suggesting limited past connectivity with the Mississippian Region. The Pacific Region is the most distinct fauna in North America and bears close affinity to the Eurasian mussel fauna.     

Northern circumpolar distribution of brackish-water plathelminths

The composition of brackish-water faunas on both sides of North America shows a high degree of similarity with the corresponding faunas in European brackish waters in terms of species of the Plathelminthes. Twenty species are common to both the Atlantic coast of Canada and Northern Europe; a further nine brackish-water plathelminths are common to the Pacific coast of Alaska and Europe; and two species occur in all three areas. These patterns of distribution must be regarded as the result of past or present connections between the American and European populations of brackish-water species. The most parsimonious explanation is the hypothesis that a species-rich community of brackish-water plathelminths has a northern circumpolar distribution.     

Phylogeography and historical ecology of the North Atlantic intertidal

Abstract Recent glaciation covered the full extent of rocky intertidal habitat along the coasts of New England and the Canadian Maritimes. To test whether this glaciation in fact caused wholesale extinction of obligate rocky intertidal invertebrates, and thus required a recolonization from Europe, we compared American and European populations using allelic diversity and techniques adapted from coalescent theory. Mitochondrial DNA sequences were collected from amphi-Atlantic populations of three cold-temperate obligate rocky intertidal species (a barnacle, Semibalanus balanoides , and two gastropods, Nucella lapillus and Littorina obtusata ) and three cold-temperate habitat generalist species (a seastar, Asterias rubens ; a mussel, Mytilus edulis , and an isopod, Idotea balthica ). For many of these species we were able to estimate the lineage-specific mutation rate based on trans-Arctic divergences between Pacific and Atlantic taxa. These data indicate that some obligate rocky intertidal taxa have colonized New England from European populations. However, the patterns of persistence in North America indicate that other life-history traits, including mechanisms of dispersal, may be more important for surviving dramatic environmental and climatic change.     

High migration rates shape the postglacial history of amphi‐Atlantic bryophytes

Paleontological evidence and current patterns of angiosperm species richness suggest that European biota experienced more severe bottlenecks than North American ones during the last glacial maximum. How well this pattern fits other plant species is less clear. Bryophytes offer a unique opportunity to contrast the impact of the last glacial maximum in North America and Europe because about 60% of the European bryoflora is shared with North America. Here, we use population genetic analyses based on approximate Bayesian computation on eight amphi‐Atlantic species to test the hypothesis that North American populations were less impacted by the last glacial maximum, exhibiting higher levels of genetic diversity than European ones and ultimately serving as a refugium for the postglacial recolonization of Europe. In contrast with this hypothesis, the best‐fit demographic model involved similar patterns of population size contractions, comparable levels of genetic diversity and balanced migration rates between European and North American populations. Our results thus suggest that bryophytes have experienced comparable demographic glacial histories on both sides of the Atlantic. Although a weak, but significant genetic structure was systematically recovered between European and North American populations, evidence for migration from and towards both continents suggests that amphi‐Atlantic bryophyte population may function as a metapopulation network. Reconstructing the biogeographic history of either North American or European bryophyte populations therefore requires a large, trans‐Atlantic geographic framework.     

The relation of Late Ordovician glaciation to the Ordovician-Silurian changeover in North American brachiopod faunas

Sheehan, P. M.: The relation of Late Ordovician glaciation to the Ordovician-Silurian changeover in North American brachiopod faunas.
The Ordovician-Silurian changeover of brachiopod faunas in North American epicontinental seas involved the abrupt extinction of endemic Late Ordovician stocks and subsequent repopulation of North American seas by Old World taxa. The Late Ordovician Gondwanaland glaciation may have lowered sea levels sufficiently to place severe stress on the widespread shallow marine faunas in North America, resulting in their eventual extinction. The Late Ordovician depositional history in North America is not well enough known to establish the presence of a latest Ordovician regression, but the earliest Silurian was an interval of off-lap in North America. Therefore, the glacial lowering of sea level is considered to be the most likely cause of the faunal changeover.     

The tropical history and future of the Mediterranean biota and the West African enigma

Aim Since the opening of the Suez Canal in 1869, many tropical taxa from the Indo‐West Pacific (IWP) realm have entered the Mediterranean Sea, which is experiencing rising temperatures. My aims are: (1) to compare biogeographically this tropical transformation of the Mediterranean biota with the tropical faunas of the Mediterranean and adjacent southern European and West African seas during the Late Oligocene to Pliocene interval; (2) to infer the relative contributions of the tropical eastern Atlantic and IWP to the tropical component of the marine biota in southern Europe; and (3) to understand why West Africa is not now a major source of warm‐water species. Location Southern Europe, including the Mediterranean Sea, and the coast of tropical West Africa. Methods I surveyed the literature on fossil and living shell‐bearing molluscs to infer the sources and fates of tropical subgenus‐level taxa living in southern Europe and West Africa during the Late Oligocene to Pliocene interval. Results Ninety‐four taxa disappeared from the tropical eastern Atlantic (including the Mediterranean) but persisted elsewhere in the tropics, mainly in the IWP (81 taxa, 86%) and to a lesser extent in tropical America (36 taxa, 38%). Nine taxa inferred to have arrived in the tropical eastern Atlantic from the west after the Pliocene did not enter the Mediterranean. The modern West African fauna is today isolated from that of other parts of the marine tropics. Main conclusions Taxa now entering the Mediterranean through the Suez Canal are re‐establishing a link with the IWP that last existed 16 million years ago. This IWP element, which evolved under oligotrophic conditions and under a regime of intense anti‐predatory selection, will continue to expand in the increasingly warm and increasingly oligotrophic Mediterranean. The IWP source fauna contrasts with the tropical West African biota, which evolved under productive conditions and in a regime of less anti‐predatory specialization. Until now, the post‐Pliocene West African source area has been isolated from the Mediterranean by cold upwelling. If further warming should reduce this barrier, as occurred during the productive and warm Early Pliocene, the Mediterranean could become a meeting place for two tropical faunas of contrasting source conditions.     

Multivariate hierarchical analyses of Early Jurassic Ostracoda assemblages

Palaeobiogeographic patterns of Early Jurassic ostracods from the northern and southern hemispheres (96 sections located in Europe, North Africa, Western Australia and North and South America) based on 243 species-level records document global patterns of distribution that can be compared to those previously published on ostracods from the European Epicontinental Sea and Tethyan and South Panthalassa areas. All described records of ostracods from both hemispheres spanning the Hettangian to Early Toarcian have been compiled and verified, and their patterns of origin and distribution have been interpreted. Jaccard coefficient of similarity was used to asses similarities among European, American and Tethyan ostracod shelf faunas. The numerical analysis shows a progressive longitudinal gradient in provincialism through the Early Jurassic, consistent with the northward drift of Tethyan ostracod faunas towards the European Epicontinental Sea and the southward movement of European taxa into Tethys and Panthalassa oceans. The spread of cosmopolitan species and extinction of endemic species, allied to the disappearance of geographical barriers, warmer climate conditions and rising sea levels can explain the reduction in ostracod diversity and the east-west provincialism throughout the Early Jurassic. Interchange between hemispheres, including bipolar distributions, are recognized from the Sinemurian time, pointing out that for most of the studied period, the climate worldwide was warm and tropical.     

Nuclear ribosomal DNA and karyotypes indicate a NW African origin of South American Hypochaeris (Asteraceae, Cichorieae)

Hypochaeris has a disjunct distribution, with more than 15 species in the Mediterranean region, the Canary Islands, Europe, and Asia, and more than 40 species in South America. Previous studies have suggested that the New World taxa have evolved from ancestors similar to the central European H. maculata. Based on internal transcribed spacer (ITS) sequences and fluorescence in situ hybridization (FISH) with 5S and 18S-25S rDNA of the previously overlooked Hypochaeris angustifolia from Moyen Atlas, Morocco, we show that it is sister to the entire South American group. A biogeographic analysis supports the hypothesis of long-distance dispersal from NW Africa across the Atlantic Ocean for the origin of the South American taxa rather than migration from North America, through the Panamian land bridge, followed by subsequent extinction in North America. With the assumption of a molecular clock, the trans-Atlantic dispersal from NW Africa to South America is roughly estimated to have taken place during Pliocene or Pleistocene.     

Paleobiogeographic relationships of angiosperms from the Cretaceous and early Tertiary of the North American area

The biogeographic affinities of the Cretaceous and early Tertiary angiosperm floras of the North American area (which includes Meso-America, and the Greater Antilles) have been the subject of considerable interest. Although recent treatments of isolated taxa have shown affinities between North American, European, east Asian and Neotropic floras, the relationships have not been quantified. This study compiles the records of fossils whose familial relationships seem secure. This provides a carefully culled, and uniformly presented review of the Cretaceous and Paleogene record from 1950 to 1989 and supplements LaMotte (1950). A subset of these records, which showed compelling evidence of subfamilial relationships, was analyzed to quantify the relationships of the Cretaceous, Paleocene, Eocene and Oligocene floras to other regions. The analysis suggests that for the entire period 24% of the fossil species had affinities with extant taxa from the Northern Hemisphere; 10% with taxa from the Northern Hemisphere that have a few species in South America; 17% with taxa from Eurasia; 3% with taxa with a disjunct Eurasian-South American pattern; 19% with taxa from South America and/or Africa; 8% with taxa from South America and/or Africa that have an important sister group in southeast Asia; 5% with taxa from the Old World; and 13% with taxa having other distribution patterns. Those fossils with affinities to Laurasian taxa are mostly found in the northern and western portions of the North American area. The fossils with affinities to South American and/or African taxa are found in the southern portions of North America, Meso-America, and the Greater Antilles. The taxa with disjunct distributions show both patterns. These patterns suggest that during this time there were wide-spread temperate elements, found throughout Laurasia; Boreotropical flora elements, distributed in North America, Europe and along the Tethys seaway to southeast Asia; and West Gondwana elements which show dispersion from South America across the proto-Caribbean. The paleobotanical data are compatible with current geological, paleontological and biogeographical studies.     

内蒙古中始新世一似ameghinornithid鸟类(鸟纲:Cariamae:Ameghinornithidae?)

内蒙古二连盆地额尔登敖包剖面(相当于伊尔丁曼哈组)的中始新世早期地层中新发现的一件标本显示其属于一个与ameghinornithid相似的种,代表了Ameghinomithidae在亚洲的首个记录.新标本具有外踝半圆形,缺失骨质腱桥,伸肌沟外侧具有大而平的结节,以及其他与ameghinomithid和似ameghinomithid鸟类共有的特征.内蒙古标本与欧洲最古老的ameghinomithids记录大体属同一时代(约48 Ma).与同时期内蒙古哺乳动物群主要由亚洲类群组成兼有少量与北美有关的绝灭类群不同,这类鸟类中始新世时在北美缺失,而存在于欧洲和亚洲.加上埃及法尤姆早渐新世地层中发现的似ameghinomithid鸟类,这类已经绝灭的鸟类的地理分布似乎比过去所认为的要广泛得多.     

A re-evaluation of the ‘mid-Cretaceous sauropod hiatus’ and the impact of uneven sampling of the fossil record on patterns of regional dinosaur extinction

The mid-Cretaceous of North America and Europe has long been noted for the absence of sauropod dinosaurs, leading several authors to suggest that this depauperate interval is a consequence of an end-Albian sauropod extinction. This time period has become known as the ‘mid-Cretaceous sauropod hiatus’, with the subsequent presence of titanosaurian sauropods in the latest Cretaceous of North America and Europe interpreted as the result of dispersal of taxa from South America and Africa, respectively. However, several lines of evidence indicate that this hiatus is probably a sampling artefact. New fossil and trackway discoveries have considerably shortened the hiatus, reducing it to the Turonian–early Campanian in North America, and to just two short intervals in the late Cenomanian–early Turonian and late Coniacian–Santonian of Europe. Palaeoenvironmental analyses of sauropods demonstrate an inland terrestrial preference for titanosaurs, the dominant Late Cretaceous sauropods; however, during the hiatus there was a decline in inland deposits and increase in coastal sediments in Europe and North America, which would have greatly reduced the probability of preserving titanosaurs. Neither the decline in inland deposits, nor the ‘sauropod hiatus’, occurred elsewhere in the world. Statistical comparisons also demonstrate a significant positive correlation between fluctuations in inland deposits and sauropod occurrences during the mid–Late Cretaceous in Europe and North and South America. Lastly, cladistic analyses do not place latest Cretaceous North American and European titanosaurs within South American and African clades, contradicting the predictions of the ‘austral immigrant’ hypothesis. The latter hypothesis also receives little support from biogeographical analysis of dispersal among titanosaurs. Thus, the ‘sauropod hiatus’ of North America and Europe is most plausibly interpreted as the product of a sampling bias pertaining to the rarity of inland sediments and dominance of coastal deposits preserved in these two regions during the mid-Cretaceous. The presence of titanosaurs in these areas during the latest Cretaceous can be explained by dispersal from Southern Hemisphere continents, but this is no more probable than descent from Early Cretaceous incumbent faunas or dispersal from Asia.     

Halacaridae (Acari) von der Atlantikküste des borealen Nordamerikas

38 halacarid species from the coasts of the boreal West Atlantic Ocean have been recorded. In a wide-spread net of stations, samples were taken from different substrata in marine and brackish waters in order to obtain information on the biology and ecology of halacarid species. Several habitats with their flora, fauna and halacarid species are described. In intertidal areas on the coasts of boreal North America fewer species were found than known from European coasts. Similar habitats on the west and east coasts of the North Atlantic Ocean are compared with respect to their halacarid population. In the rhombognathine and the genusHalacarellus, most species found in the West Atlantic Ocean are known in the East Atlantic too, living in similar habitats. The generaAnomalohalacarus andCopidognathus are common both in North American and European waters, but comparable biotopes are inhabited by different species, though often related or very similar in their appearance. 45 % of the halacarid species found in the boreal West Atlantic Ocean are also known in the East Atlantic. Hypotheses as to the dispersal and geographical distribution of halacarid genera and species are discussed. It is supposed, that many of the amphiatlantic species invaded biotopes on the American and European coasts, shortly after these continental plates drifted apart.     

Tracing the patterns of non-marine turtle richness from the Triassic to the Palaeogene: from origin to global spread

Turtles are key components of modern vertebrate faunas and their diversity and distributions are likely to be affected by anthropogenic climate change. However, there is limited baseline data on turtle taxonomic richness through time or assessment of their past responses to global environmental change. We used the extensive Triassic–Palaeogene (252–223 Ma) fossil record of terrestrial and freshwater turtles to investigate diversity patterns, finding substantial variation in richness through time and between continents. Globally, turtle richness was low from their Triassic origin until the Late Jurassic. There is strong evidence for high richness in the earliest Cretaceous of Europe, becoming especially high following the Cretaceous Thermal Maximum and declining in all continents by the end-Cretaceous. At the K–Pg boundary, South American richness levels changed little while North American richness increased, becoming very high during the earliest Palaeogene (Danian). Informative data are lacking elsewhere for this time period. However, the Selandian–Thanetian interval, approximately 5 myr after the K–Pg mass extinction, shows low turtle richness in Asia, Europe and South America, suggesting that the occurrence of exceptional turtle richness in the post-extinction Paleocene fauna of North America is not globally representative. Richness decreased over the Eocene–Oligocene boundary in North America but increased to its greatest known level for Europe, implying very different responses to dramatic climatic shifts. Time series regressions suggest number of formations sampled and palaeotemperature are the primary influencers of face-value richness counts, but additional factors not tested here may also be involved.     

Introduced or glacial relict? Phylogeography of the cryptogenic tunicate Molgula manhattensis (Ascidiacea,Pleurogona)

Aim The tunicate Molgula manhattensis has a disjunct amphi‐Atlantic distribution and a recent history of world‐wide introductions. Its distribution could be the result of regional extinctions followed by post‐glacial recolonization, or anthropogenic dispersal. To determine whether the North Atlantic distribution of M. manhattensis is natural or human‐mediated, we analysed mtDNA cytochrome c oxidase subunit I (COI) sequence variation in individuals from cryptogenic and introduced ranges. Location North Atlantic Europe and America; Black Sea; San Francisco Bay; Osaka Bay. Methods Nuclear 18S rDNA sequences were used to resolve phylogenetic relationships and mtDNA COI sequences for phylogeographic analyses. Results Phylogenetic analyses confirmed that M. manhattensis and M. socialis, which are frequently confused, are distinct species. MtDNA haplotype diversity was nearly three times higher with deeper relationships among haplotypes on the North‐east American coast than in Europe. Diversity declined from south to north in America but not in Europe. In areas of known introductions (Black Sea, Japan, San Francisco Bay), M. manhattensis showed variable levels of haplotype diversity. Medium‐to‐high‐frequency haplotypes originating from the North‐west Atlantic were present in two locations of known introductions, but not in Europe. Private haplotypes were found on both sides of the Atlantic and in introduced populations. The mismatch distribution for the North‐east Atlantic coast indicates a recent expansion. Main conclusions Molgula manhattensis is native in North‐east America. However, whether it was introduced or is native to Europe remains equivocal. Additional sampling might or might not reveal the presence of putative private European haplotypes in America. The low European diversity may be explained by low effective population size and a recent expansion, or by low propagule pressure of anthropogenic introduction. Absence of medium‐to‐high‐frequency American haplotypes in Europe may be the result of exclusive transport from southern ports, or long‐term residence. These arguments are ambiguous, and M. manhattensis remains cryptogenic in Europe.     

Analysis of insect distribution in the Northern Hemisphere by the example of the subfamily Arctiinae (Lepidoptera,Arctiidae). 2. Species level

An attempt is made to apply cluster analysis to comparison of local faunas in the Northern Hemisphere at the species level by the example of the subfamily Arctiinae (Lepidoptera, Arctiidae). A total of 200 North African, Eurasian (New Guinea inclusive), and North American (north of the United Mexican States) local faunas have been considered. It is found that the circumarctic fauna is clearly separated from the Palearctic and Nearctic ones, being closer to the former only at the level of genera. Therefore, it is not reasonable to recognize the united European-Canadian subprovince of the boreal belt according to the tiger moth faunas. The Palearctic tiger moth fauna is characterized by relatively smooth variations within the boreal, subboreal, and western subtropical belts. The fauna gradually changes from the Amur catchment area to South China, Himalayas, and India so that all fauna types of these regions are closely related to one another and, to a lesser extent, to equatorial fauna types of Southeast Asia islands. The boundary between the Palearctic and Oriental (Indo-Malayan) provinces should be drawn north of the Yangtze catchment area. The most dramatic fauna change at the species level takes place between North China and the Yangtze catchment, and at the genus level, between Northern and Northeastern China. It is reasonable to establish a broad transition area between the two zoogeographic provinces in Eastern Asia. On the grounds of the nonuniform tiger moth fauna, the South Chinese-East Himalayan subprovince should be assigned to the Oriental (Indo-Malayan) province rather than the Palearctic one, as was repeatedly proposed. The Southwest-Asian fauna (Arabian Peninsula and southern Iran) is transitional between the Palearctic, African, and Oriental ones. Many African taxa penetrate to the west and south of the Arabian Peninsula, whereas Oriental and Paleotropical species penetrate to southern Iran. It is reasonable to elevate considerably the rank of the Quinghai-Tibet highland fauna by distinguishing its habitat as a separate zoogeographic subprovince, because the similarity between this fauna type and any other Palearctic fauna at the species level is much less than between temperate faunas of the Palearctic and Nearctic. The assignment of this fauna to the Palearctic is confirmed only at the genus level.     

Late devonian facies inter-relationships in bordering areas of the North Atlantic and their palaeogeographic implications

Late Devonian faunal and facies relationships are examined in seven around the North Atlantic — in eastern North America, Greenland, western Europe and northwest Africa. A shallow marine (“littoral”) environment, characterized by the genus Cyrtospirifer, is distinguished from a deeper water (“bathyal”) goniatite-conodont milieu on the one hand, and from the “Old Red Sandstone” terrestial facies bearing plant an d fresh-water fish remains on the other.Current or source directions indicate that an “Acadian Divide” existed, separating west-flowing drainage systems in North America from those flowing to the east on the Afro-European side. All species of the osteolepid Latvius, and the majority of species of Glyptopomus are found on the eastern flank. Conversely, the earliest amphibian, Ichthyostega, may have been confined to the western side of the divide.Palaeogeographic reconstruction places northwest Africa fairly close to the Catskill Delta in the Late Devonian, thus accounting for the presence of an “American fauna” in the former. North—south migration of littoral faunas along the Afro-European shores was, however, apparently inhibited.     

Species diversity and endemism in the Daphnia of Argentina: a genetic investigation

Although the temperate regions of South America are known to have a diverse daphniid fauna, there has been no genetic evaluation of the existing taxonomic system or of the affinities between the North and South American faunas. The present study analyses mitochondrial DNA sequences and allozyme variation to investigate species diversity in 176 Daphnia populations from Argentina. This work established the presence of at least 15 species in Argentina, six of which are either undescribed or are currently misidentified and two of which represent range extensions of North American taxa. Eleven of the Argentine species appear endemic to South America, while the remaining four also occur in North America. In the latter cases, the close genetic similarity between populations from North and South America indicates the recent exchange of propagules between the continents. While biological interactions and habitat availability have undoubtedly contributed to the observed species distributions, chance dispersal has apparently played a dominant role in structuring large-scale biogeographical patterns in this genus and probably in other passively-dispersed organisms.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 171−205.     

Caddisflies from Cenozoic resins of Europe

Analysis of the available data on the findings and taxonomical structure of caddisflies (Insecta, Trichoptera) in the Cenozoic fossil resins of Europe shows that there are four European amber regions (Baltic, Rovno, Saxonian, and Danish) are characterized by a relatively abundant trichopteran fauna, comprising 27 families, 72 genera, and 256 species. These faunas show the dominance of Psychomyioidea (families Polycentropodidae, Psychomyiidae, and Ecnomidae) with Polycentropodidae comprising up to 75% of all records. The amber faunas are second in the dominance of Polycentropodidae only to the terminal Eocene of Florissant (84% of Polycentropodidae). No modern caddisfly species have been found. The amber regions are significantly different in the species composition of Trichoptera although the generic and family structures are similar. Comparison with the modern faunas of Europe shows the absence of advanced Limnephilidae, which are characteristic of the Holocene faunas of Europe, and the rarity of recently abundant Hydropsychidae and Hydroptilidae. The overall composition of amber Trichoptera suggests that it is structurally related to the faunas of Caucasus and Southeastern Asia and might be evidence of seasonally low-contrast (equable) climate in the Late Eocene of Europe.     

西藏南部聂拉木地区晚泥盆世—早石炭世的介形类

本文系统描述西藏南部聂拉木地区晚泥盆世–早石炭世介形类共计15属24种。根据介形类的组合面貌及孢子、牙形刺的研究结果推断,亚里剖面上的亚里组时代为晚泥盆世–早石炭世,泥盆系-石炭系界线(D-CB)大致位于亚里东沟段顶部至沟陇日段。亚里组产出的介形类生态组合属于光滑速足目集群或艾菲尔生态型,指示亚里组在沉积时为远岸浅水沉积环境,且在上部腊扎蒲段水深变浅。亚里组介形类面貌与华南泥盆纪介形类相似程度高,与俄罗斯和欧美地区也有相似的属种,说明泥盆纪-石炭纪之交介形类的地理隔离并不显著,在各个板块之间有属种交流的可能。     

Cones, Seeds, and Foliage of Tetraclinis Salicornioides (Cupressaceae) from the Oligocene and Miocene of Western North America: A Geographic Extension of the European Tertiary Species

The cupressaceous genus Tetraclinis is recognized from the Oligocene and Miocene of western North America on the basis of co-occurring seed cones, seeds, and foliage branches. Morphological and anatomical comparisons with the two previously recognized European Tertiary species indicate that the North American specimens are morphologically inseparable from Tetraclinis salicornioides (Unger) Kvacek. The North American taxon is treated as a new variety, T. salicornioides (Unger) Kvacek var. praedecurrens (Knowlton) comb. et stat. nov., and is distinguished from the European representatives, T. salicornioides (Unger) Kvacek var. salicornioides, by slight anatomical differences in the leaf epidermis. Although cones and seeds of the fossil species are closely similar to those of extant Tetraclinis articulata, the foliage is more "spreading," composed of flattened segments with fused facial and lateral leaves that are apparently adaptive for a more mesic climate. The recognition of T. salicornioides in western North America along with the absence of Tetraclinis in the fossil and recent flora of eastern Asia provide evidence for communication of the species across the North Atlantic during the early or middle Tertiary.