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1.
The Baqueró Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America. Whereas the age of the upper part of the Group, namely the Punta del Barco Formation, has been recently dated at 114.67 ± 0.18 Ma, the rest of the unit still lacks precise dating. In this contribution a CA-TIMS U–Pb zircon age of 118.23 ± 0.09 Ma for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Ticó Formation (lower part of the Baqueró Group) is reported. This age constrains the duration of deposition of the Baqueró Group to approximately 4 Ma and provides new evidence for the age interpretation of the previously described angiosperm flora and associated pollen assemblages from this unit, until now interpreted as early Aptian or possibly Barremian in age. The Aptian age of the Baqueró Group allows a better comparison between the paleofloras from this southernmost region.  相似文献   

2.
The revision of the stratigraphy of the Cerro Bayo in the Bajo Grande area (Argentinean Patagonia) and the new 206Pb/238U age of 116.85 ± 0.26 Ma constrain the dating of the Baqueró flora, one of the most abundant Aptian floras of southern Gondwana. This flora, preserved in the Baqueró Group, represents an extinct biome that flourished ca. 118 Ma ago and was affected by increasing regional volcanism during the subsequent four millions years. The outcrops of the Cerro Bayo are characterized by fluvio-lacustrine deposits divided into three facies associations that include nine lithofacies. The first palynological record for the locality confirms the correlation of the lower part of the outcrops with the Anfiteatro de Ticó Formation (the oldest unit of the Baqueró Group). The new radiometric age and stratigraphy support recognition of the Bajo Tigre Formation (the middle unit of the Baqueró Group) in the area and date the earliest stage in angiosperm diversification in southern South America. Stratigraphic relationships among the Baqueró, Chubut and Divisadero groups are briefly discussed.  相似文献   

3.
The Baqueró Group holds a rich fossil flora including macrofloristic and palynological remains that characterize the Early Cretaceous vegetation of Argentina. The age of the upper part of the Group, known as Punta del Barco Formation, has been a topic of several discussions in the past. The type locality of this stratigraphic unit exposes fossiliferous tuffs together with muddy tuffs and tuffaceous sandstones beds. However, there have been no reliable age constraints for the fossil assemblages. 206Pb/238U analyses of zircon crystals yielded an age of 114.67 ± 0.18 Ma. This age control makes possible an improved analysis and comparison of the floras in the southern region.  相似文献   

4.
The Kholokhovchan Flora comes from tuffaceous – terrigenous deposits of the Vetvinskaya Member (Chalbugchan Group) in the Penzhina and Oklan rivers interfluve, Northeastern Russia. The depositional environment of the plant-bearing deposits is interpreted to have been a freshwater lake. The Kholokhovchan Flora hosts 42 fossil plant species belonging to Marchantiopsida, Polypodiopsida, Ginkgoales, Leptostrobales, Bennettitales, Pinales and Magnoliopsida. It is characterised by diverse angiosperms, less diverse conifers and ferns, by the presence of relatively ancient Sphenobaiera, Phoenicopsis and Pterophyllum together with advanced Late Cretaceous Taxodium, Glyptostrobus and angiosperms, among which platanoids are quite diverse. The Kholokhovchan Flora is most similar to Penzhina and Kaivayam floras of the Anadyr-Koryak Subregion and Arman Flora of the Okhotsk-Chukotka volcanogenic belt (Northeastern Russia) and should be dated as Turonian–Coniacian. The Kholokhovchan Flora, that populated volcanic plateaus and intermontane valleys, are characterised by a mixture of ancient “Mesophytic” plants with typical Late Cretaceous “Cenophytic” taxa. This peculiar composition probably reflects a gradual penetration of new angiosperm-dominated plant assemblages into older floras: during the Late Cretaceous, “Cenophytic” assemblages migrated along river valleys and other disturbed habitats into the interior of Asia, eventually occupying volcanogenic uplands, and in places replacing the “Mesophytic” fern-gymnospermous communities that existed there. Two new angiosperm species, as well as four the most characteristic conifers of the Kholokhovchan Flora, are described: Cupressaceae gen. et sp. indet. cf. Widdringtonites sp., Taxodium cf. olrikii, Taxodium sp., Glyptostrobus sp., Ettingshausenia vetviensis sp. nov. and Parvileguminophyllum penzhinense sp. nov.  相似文献   

5.
New plant macrofossil localities are found in the middle-upper part of the Albian Upper Hatira Formation of Makhtesh Qatan, an erosion crater in the northern Negev. These are so far the only outcrop localities in the Negev containing plant compressions and well-preserved sporomorphs. Their age assignments are controlled by the ammonite Knemiceras records below and above the plant-bearing sequence in the adjacent Makhtesh Hatira. The macrofossil assemblages are strikingly different in the sandy fluvial and shaly lacustrine facies, the former being dominated by Araucaria, Athrotaxopsis, Brachyphyllum and pinnatifid Sapindopsis, comparable at the plant assemblage and leaf morphological levels to the early to early late Albian assemblage of the North American Potomac flora. The lacustrine shale macrofossil assemblages appear archaic on account of their diverse pteridophyte component and sparse angiosperm remains. A new supposedly gnetophytic genus and species Qataniaria noae Krassilov, gen. et sp. nov. is dominant in the shale horizon. The sporomorph assemblages are strongly dominated by psilate trilete spores (87-93%). In the absence of elaterate forms, the angiosperm pollen Afropollis jardinus, Pennipollis, Tricolpites spp. and Walkeripollis sp. is consistent with the early Albian age. The abundance and diversity of conifers and the prominence of the fern bog assemblage suggest a relatively humid phase of the regional Albian climates.  相似文献   

6.
The mid-Cenomanian fish beds of Nammoura, Mont-Liban district, Lebanon contain a diverse fauna of aquatic and terrestrial vertebrates, a few crustaceans and moderately well-preserved plant remains of which a single species,Sapindopsis anhouryi , was previously described by Dilcher & Basson (1990). We add 11 species of ferns, gymnosperms and angiosperms of which Nammouria cretacea gen. et sp. nov, Nupharanthus cretacea gen. et sp. nov., Sapindopsis libanensis sp. nov. and Nammourophyllum altingioides gen. et sp. nov. are new taxa. The florule differs markedly from both Early Cretaceous and Turonian plant assemblages of the Middle East, thereby representing a distinct stage of the regional floristic evolution. Its phytogeographic affinities are with contemporaneous floras of North America, Central Europe and the Crimea. A combination of such features as xeromorphism, the prevalence of compound leaves, and the presence of deciduous angiosperm components and gymnosperms may indicate climatic conditions similar to those of the present day Mediterranean.  相似文献   

7.
In 2001 a partial skeleton of an Iguanodon was discovered in the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks near Ockley, Surrey, UK. When the dinosaur was excavated, a detailed stratigraphic section was logged and 25 samples taken for palynological and micropalaeontological (ostracod and megaspore) analysis, including a detailed sample set of the dinosaur bed itself. Qualitative and quantitative analysis of the palynoflora revealed rich and well-preserved non-marine assemblages of pollen and spores, including early angiosperms, and freshwater green algae. Four types of angiosperm pollen are described and assigned to the genus Retimonocolpites Pierce, 1961, but left in open nomenclature. Some marine elements such as dinoflagellate cysts are identified as the result of reworking of Middle and Upper Jurassic sediments. The pollen/spore assemblages depict a vegetational change from principally gymnosperm-dominated assemblages at the base to principally pteridophyte-dominated assemblages at the top of the section. The dinosaur bed shows a pteridophyte-dominated assemblage, with a significantly high amount of the freshwater green alga Scenedesmus novilunaris He Cheng-quan et al., 1992. Samples close to the dinosaur bed yielded the first useful ostracod finds from Smokejacks Brickworks: well-preserved assemblages containing Cypridea clavata (Anderson, 1939), Damonella cf. pygmaea (Anderson, 1941), Stenestroemia cf. cressida Anderson, 1971 and Stenestroemia sp. A, and fragments and damaged valves of a thin-shelled ostracod, possibly belonging to Mantelliana Anderson, 1966. Those identified as Cypridea clavata show a wide range of morphological variety and in opposition to Anderson's (1967, 1985) taxonomic scheme, which would assign them to up to five different taxa, they are considered to be intraspecific variants of a single species. The possibilities and limitations of age determination of the Wealden sediments using palynomorphs and ostracods are discussed; distinct forms of early angiosperm pollen, together with the ostracod fauna, are consistent with an early Barremian age. Pollen and spores are discussed in terms of their parent plants and the reconstruction of vegetation and palaeoclimate. Palynology and ostracods give evidence for temporary freshwater conditions at the time when the Iguanodon died and the carcase was buried.  相似文献   

8.
Seven packrat midden samples make possible a comparison between the modern and late Pleistocene vegetation in Kings Canyon on the western side of the southern Sierra Nevada. One modern sample contains macrofossils and pollen derived from the present-day oak-chaparral vegetation. Macrofossils from the six late Pleistocene samples record a mixed coniferous forest dominated by the xerophytic conifers Juniperus occidentalis, Pinus cf. ponderosa, and P. monophylla. The pollen spectra of these Pleistocene middens are dominated by Pinus sp., Taxodiaceae-Cupressaceae-Taxaceae (TCT), and Artemisia sp. Mesophytic conifers are represented by low macrofossil concentrations. Sequoiadendron giganteum is represented by a few pollen grains in the full glacial. Edaphic control and snow dispersal are the most likely causes of these mixed assemblages.The dominant macrofossils record a more xeric plant community than those that now occur on similar substrates at higher elevations or latitudes in the Sierra Nevada. These assemblages suggest that late Wisconsin climates were cold with mean annual precipitation not necessarily greater than modern values. This conclusion supports a model of low summer ablation allowing for the persistence of the glaciers at higher elevations during the late Wisconsin. The records in these middens also suggest that S. giganteum grew at lower elevations along the western side of the range and that P. monophylla was more widely distributed in cismontane California during the Pleistocene.  相似文献   

9.
Based on the palynological data from Well Ta-19-36 and Well Ta-19-37 in the Ta'nan Sag, and Well Ta-22-1 and Well Ta-21-1 in the Bayin Gobi Sag, a spore-pollen assemblage from the Damoguaihe Formation is named as Cicatricosisporites minutaestriatus- Aequitriradites spinulosus-Protopinus sp. assemblage in the Tamutsag Basin, Mongolia. The assemblage is characterized by abundant gymnosperm pollen and diverse fern spores, counted 46.35%–65.57% and 34.43%–52.58% in percentage respectively. Among the gymnosperm pollen, Pinuspollenites sp.(2.66%–16.94%), Protopinus sp.(0–11.38%) and Protopicea sp.(0–10.81%) are dominant; and Alisporites sp., Cerebropollenites sp., Podocarpidites sp., and Abietineaepollenites sp. are common. Some important elements, such as Chasmatosporites sp., Callialasporites prominulus, Parvisaccites sp., Parcisporites sp., Jiaohepollis cf. annulatus, J. bellus, J. verus, Polycingulatisporites sp., Schizaeoisporites certus, Classopollis annulatus are seen. Within the fern spores, Osmundacidites wellamanii(0.85%–4.93%), Appendicisporites sp.(0–4.45%), Baculatisporites comaumensis(0.80%–2.87%), Cicatricosisporites sp.(0.51%–2.66%), C. minor(0–2.14%), Foraminisporis asymmetricus(0–2.40%), Aequitriradites sp.(0– 2.19%) and Cyathidites minor(0–2.13%) are dominant; and some specie of Densoisporites, Cooksonites, Impardecispora, Pilosisporites, Schizaeosprites, Fixisporites, Leptolepidites, Trilobosporites, Kuylisporites, Klukisporites, Hsuisporites, Couperisporites, Maculatisporites are seen. The angiosperm pollen are rare in the assemblage, characterized by Clavatipollenites sp.(0–0.80%) and Songipollis sp.(0–0.27%). The geological age of the Damoguaihe Formation is assigned to Hauterivian – Barremian of Early Cretaceous according to the palynological data, due to the fact that there existed a lot of diverse spores of the family Schizaeaceae and prosperous gymnosperm saccat pollen which the corpus and sacci are differentiated completely, and the presence of early angiosperm pollen of Clavatipollenites. However, the zircon U-Pb isotopic dating of the volcanic rocks in the Nantun Formation indicated that the overlying strata of the Nantun Formation, i.e. the Damoguaihe Formation must be younger than 127.0±2.0–137.9±1.5 Ma. This is consistent with the palynological data. Furthermore, the vegetation reconstructed on the palynological data of the Damoguaihe Formation is conifer forest with shrubs and grassland, belonging to the semi-humid or humid middle to south subtropical climate. Moreover, three new species, namely Biretisporites punctatus sp. nov., Chasmatosporites reticulates sp. nov. and Concentrisporites contractus sp. nov. are described here.  相似文献   

10.
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11.
A new genus and species, Rebouliothallus huolinhensis sp. nov., and two uncertain species, Ricciopsis sp. and Hepaticites sp., are described. The fossils were collected from the Lower Cretaceous Huolinhe Formation of Huolinhe Basin, northeastern China. The new genus Rebouliothallus was established in the Aytoniaceae family of Marchantiales. Rebouliothallus huolinhensis appears to be quite similar to species of the extant genus Reboulia Raddi. The species is characterized by the relatively large ventral scales. Ventral scales are large, imbricate and arranged in two rows on the ventral surface. Rhizoids are either pegged or smooth. Ricciopsis sp. is characterized by the rosette-forming thallus. Hepaticites sp. shows some similarities to liverworts. Of the forty-nine Early Cretaceous floras of China, only two floras, one from the Huolinhe basin, Inner Mongolia and the other from the Jixi Basin, Heilongjiang Province, contain fossil liverworts. The rare fossil liverwort records in the Early Cretaceous floras of China may be the result of taphonomic bias.  相似文献   

12.
The Albian Alexander Island macrofossil flora from the Antarctic Peninsula preserves a diverse community of liverworts (Marchantiophyta), ferns (Polypodiopsida), Lycopodiales, Equisetales, Cycadales, Ginkgoales, seed-ferns (Bennettitales and Pentoxylales), Coniferales, and the first representatives of angiospermous leaves in Antarctica. Despite the presence of angiosperms in this assemblage, ferns are the most diverse element of the flora and are also ecologically dominant, while angiosperms contribute a smaller component to floristic diversity and have low abundance. Here we describe 11 fern taxa from this assemblage. The fossils are assigned to Cladophlebis, Sphenopteris and two newly created genera. The new genera and species are described under Adiantitophyllum serratum gen. et. sp. nov. and Nunatakia alexanderensis gen. et. sp. nov., and the new species are recognized as Cladophlebis dissecta sp. nov., Cladophlebis drinnanii sp. nov., Cladophlebis macloughlinii sp. nov. and Sphenopteris sinuosa sp. nov. In total, there are 24 fern species known from Alexander Island. In comparison to older floras (Jurassic) there is a greater diversity of ferns, while latest Cretaceous floras preserve significantly fewer fern species and more angiosperms. Possible factors that might account for such high fern diversity are high rainfall or generally humid conditions, regular disturbances by flooding and occasionally fire, and the preservation of a diverse range of fern communities that represent several palaeoenvironments.  相似文献   

13.
Fossil diatom assemblages from a 12-m core from Kirchner Marsh were compared with modern surface assemblages from 159 Minnesota and labrador lakes using cluster analysis. The deepest levels of the core (spruce pollen zone 13,000 to 10,200 yr B.P.) resemble modern diatom assemblages from deep oligotrophic lakes of northeastern Minnesota. Diatom assemblages of the pine pollen zone (about 10,200 to 9500 yr B.P.) have few modern analogs. In the oak zone (9500 yr B.P. to present) after a brief pulse of diatom species indicative of eutrophication, the assemblages are dominated by species characteristic of shallow lakes, suggesting a drop in the lake water level during the prairie period (5500 to 7500 yr B.P.). Macrofossil data of W. A. Watts and T. C. Winter (1966, Geological Society of America Bulletin77, 1339–1360) show that this shift to shallow-water diatoms occurred when aquatic macrophytes appeared at the site in abundance.  相似文献   

14.
The upper Cenomanian–lower Turonian paleoenvironments of the Preafrican Trough carbonate platform is characterized by analyzing the structure of the ostracod assemblages and the information provided by other groups, and also by linking together the paleontological and geochemical data (detrital influx-redox-paleoproductivity proxies, δ13C curve). Two different domains (eastern and western) can be recognized on the platform during the late Cenomanian, before the onset of the OAE2. The western domain corresponds to a low-energy environment developed on a mid and/or outer ramp with hypoxic waters, low detrital influx and low paleoproductivity. The paleoecological assemblages show limited specific diversity but variable density. The ostracods are opportunistic and unspecialized (r strategists), being associated with Buliminidae, surface and intermediate-water planktonic foraminifera, and fishes. The eastern domain corresponds to an inner ramp and/or peritidal environment with oxic waters, low detrital influx and low paleoproductivity, developed in a higher energy environment with paleoecological assemblages showing high diversity but variable density. The ostracods are more specialized (K strategists), being represented by diverse and constant assemblages associated with diversified benthic foraminifera, calcareous sponges and echinoderms, as well as intermediate- and deep-water planktonic foraminifera. The onset of the OAE2 has no influence on the western ostracod assemblages, but leads to the decline of the ostracod fauna and the disappearance of the deep-water planktonic foraminifera in the eastern domain. During the early Turonian, after the OAE2, the platform becomes an outer ramp with increased paleoproductivity, but is associated with a decrease of taxonomic diversity in hypoxic waters. The ostracods are very sparse and unspecialized, associated with siliceous sponges, Buliminidae, surface-living planktonic foraminifera, fishes and pelagic crinoids. Marine paleobiogeographic communication is relatively easy across the carbonate platforms between the Preafrican Trough and other Moroccan regions, as well as between Morocco and different parts of the South Tethyan and East Atlantic margins belonging to the Cenomanian–Turonian South Tethyan Ostracod Province (STOP). Thirteen new species are described: Cytherella tazzouguertensis n. sp., Bairdiacypris chaabetensis n. sp., Bythocypris amelkisensis n. sp., Pontocypris tadighoustensis n. sp., Procytherura? elongatissima n. sp., Loxoconcha akrabouensis n. sp., Hemiparacytheridea sagittaemucronata n. sp., Rehacythereis errachidiaensis n. sp., Rehacythereis zizensis n. sp., Veenia (Nigeria) tardaensis n. sp., Veenia (Nigeria) mediacostarobusta n. sp., Xestoleberis? preafricanensis n. sp., and Xestoleberis circinatus n. sp.  相似文献   

15.
Early Pleistocene sediments bearing gastropod shells and pollen flora were found during coring at Jawornik (South Poland) at a depth interval of 54.30–39.00 m, beneath the oldest till of the Carpathians. Thirteen land-snail taxa identified in 55 samples of the core formed two molluscan assemblages. In the bottom part, typical cold-loving snails were found (e.g. Vallonia tenuilabris, Pupilla loessica, Vertigo genesii, Columella columella), whereas in the upper part only Semilimax kotulae was present. The succession of molluscan assemblages may suggest that at the site of deposition, after a phase of tundra, steppe-tundra or forest-steppe landscape with patches of wet habitats in cold climate, the climate became slightly milder but still cool, favourable to the spreading of boreal (coniferous) woodlands. Pollen analysis was performed only for the upper part of the profile. The pollen spectra, besides the Tertiary (Miocene) elements, contained sporomorphs common to the Tertiary and Quaternary floras. Among them, the highest percentages were noted for Pinus haploxylon t., P. diploxylon t., Picea, Quercus, Ericaceae, Betula, and Ulmus. The fact that the sediments with organic remains underlie the oldest Scandinavian till suggests that they are older than the oldest glacial unit of the South-Polish Complex (Narevian = Menapian, ~ 1.2 Ma).  相似文献   

16.
A microfossil assemblage has been found in the widely spaced (300 km apart) Baikit and Katanga areas (inner Siberian Platform) in stratigraphically coeval strata in the lower part of the petroliferous Kamo Group (Riphean). It comprises complex protists Tappania plana Yin; acritarchs Valeria lophostriata Jank., Satka sp., Lophosphaeridium sp., Pulvinosphaeridium sp., and Miroedichia sp.; porous vesicles of Tasmanites sp. and Osculosphaera sp.; vesicles with anastomosing processes, and spiral filaments of Obruchevella and Glomovertella. Siberian fossil microbiota is considerably more diverse than biota with Tappania protists known in Australia and China. A taxonomically similar fossil biota found 1500 km northeast of the well-studied Riphean section in the Olenek uplift suggests that the host rocks, too, are stratigraphically coeval. This permits refining the age of remains of the first complex eukaryotes from the inner platform and is an additional correlation criterion for the lower Kamo Group.  相似文献   

17.
The plant remains and palynological assemblages are studied in detail in the section of the coal-bearing upper part of the Aptian Starosuchan Formation near the village of Molchanovka (Partizansk Basin, South Primorye region). On the basis of the light and electron microscopic study of the disperse cuticles, it was established that the coals are mostly composed of remains of taxodialean Elatides asiatica (Yok.) Krassil., subordinate Miroviaceae, rare ginkgoalean Pseudotorellia sp., and bennettite Nilssoniopteris rithidorachis (Krysht.) Krassil. The spores Gleicheniidites and pollen Taxodiaceaepollenites are dominant in the palynospectrum of the coal interlayer. It was found that dominant taxodialeans and gleicheniaceous ferns with less abundant Miroviaceae, ginkgoaleans, and rare bennettites occurred in the Aptian swamp communities of the Partizansk basin. Shoots and leaves of Elatides asiatica, fronds of Birisia onychioides (Vassil. et K.-M.) Samyl., are dominant in the burials of plants from the clastic rocks. The fragments of leaves of Nilssoniopteris, scale-leaved conifers, and Ginkgo ex gr. adiantoides are rare. The disperse cuticle of these layers mostly includes Pseudotorellia sp.; however, its remains in burials were not found. The spores Laevigatosporites are dominant in the palynospectra from the clastic interlayers. Ginkgocycadophytus and taxa close to Pinaceae are plentiful among the pollen of gymnosperms.  相似文献   

18.
华北地块东北缘红庙子盆地鹰嘴砬子组孢粉化石   总被引：1，自引：1，他引：0  
王成龙  刘雪松  张梅生 《地质通报》2019,38(7):1089-1094
报道华北地块东北缘地区红庙子盆地鹰嘴砬子组的孢粉化石,建立了Cicatricosisporites-Abietineaepollenites-Piceites组合,该组合的主要特征为:以裸子类双气囊花粉和海金沙科孢子为主,含一定量裸子类无气囊花粉,未见被子类花粉,孢粉组合特征可与松辽盆地沙河子组对比。一些具有早白垩世时代意义的孢粉化石,如Cicatricosisporites sp.,Cicatricosisporites undulates和Cicatricosisporites implexus的出现,表明鹰嘴砬子组的地质时代为早白垩世。根据孢粉化石资料,推测华北地块东北缘地区在鹰嘴砬子组沉积时期古植被面貌以松科和杉科组成的松柏类针叶林为主,林下生长着真蕨类。古气候相当于湿润-半湿润的亚热带气候。  相似文献   

19.
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20.
This paper discusses a well-represented fossil record of cartilaginous fishes (Chondrichthyes) from southern South America. The recovered samples allow the recognition of three assemblages with chronostratigraphic and paleogeographic value: i) typical Maastrichtian sharks and rays with affinities to eastern Pacific fauna, including the taxa Ischyrhiza chilensis, Serratolamna serrata, Centrophoroides sp. associated to Carcharias sp., and Dasyatidae indet.; ii) a scarce reworked assemblage of Paleocene–Early Eocene age including the taxa Otodus obliquus and Megascyliorhinus cooperi; iii) a rich assemblage with reworked taxa of Early to Middle Eocene age, together with autochthonous deposited Middle to Late Eocene taxa with close affinities to paleoichthyofaunas recovered from the North Atlantic, represented by Carcharias ‘hopei’, Odontaspis winkleri, Carcharoides catticus, Macrorhizodus praecursor, Carcharocles auriculatus, Striatolamia sp., Striatolamia macrota, Hexanchus agassizi, Notorhynchus sp., Myliobatis sp., Abdounia sp., Pristiophorus sp., Squatina sp., cf. Rhizoprionodon sp., Ischyodus sp., and one new species, Jaekelotodus bagualensis sp. nov. The studied samples include for the first time taxa with well established chronostratigraphic resolutions as well as taphonomic information that help clarifying the age of the fossil-bearing units. In addition, they provide relevant information about the evolution of the Magallanes (=Austral) Basin from the Upper Cretaceous to the Paleogene, suggesting a probable connection with the Quiriquina Basin of south-central Chile during the latest Cretaceous. Finally, the studied assemblages indicate a latitudinal pattern of distribution that provides valuable data on the environmental evolution and temperature of southern South America during the Paleogene.  相似文献   

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