首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
In this paper, we describe a new species of Hemiacodon known only from University of Colorado Museum Loc. 92189 (Donna's Locality) in the Turtle Bluff Member of the Bridger Formation, Green River Basin, southwestern Wyoming. Donna's locality has yielded a diverse mostly small-bodied mammalian assemblage of Bridgerian and first appearance Uintan mammalian taxa, as well as range-through taxa. Together with H. engardae sp. nov., the faunal assemblage from Donna's Locality and more recently discovered localities in the same stratigraphic interval provides the first conclusive paleontological evidence of an earliest Uintan age (Ui1A biochron) for the Turtle Bluff Member of the Bridger Formation.The new species is represented by a sample of 11 specimens consisting of well-preserved upper and lower premolars and lower molars. H. engardae is distinct from H. gracilis on the basis of overall larger size as well as a combination of features of the premolars and molars related to a greater development of shearing crests. This suggests that H. engardae may have incorporated more foliage into its diet than the Bridgerian species, H. gracilis.  相似文献   

2.
Most omomyids are relatively small bodied (e.g. <500 g), but beginning in the middle Eocene, some omomyids began to grow larger. The largest omomyids occur in the late middle Eocene during the Uintan NALMA, reaching an estimated body mass over 1 kg. The hind limb skeleton of small omomyids is relatively well known, and is generally thought to show active arboreal quadrupedal and leaping adaptations. New postcranial specimens of previously unknown elements from the larger Uintan omomyids, Ourayia (two species), Chipetaia lamporea, and Mytonius hopsoni have recently been recovered from the Uinta Formation, Utah, and from the Mission Valley Formation, California, and they provide additional information concerning their locomotor behavior.The new specimens include several distal tibiae, partial calcanei, a complete talus and a proximal first metatarsal of Chipetaia; distal femora, distal tibiae, cuboids, and partial calcanei of Ourayia uintensis; a complete calcaneus of Ourayia sp.; and a partial calcaneus and talus of Mytonius. Metric analysis of these elements, together with qualitative observations of non-metric traits, indicate that Ourayia and Chipetaia show equal or greater development of traits associated with leaping behavior (including elongation of the calcaneus, navicular and cuboid) than do smaller omomyids from North America. The elements of Mytonius, although fragmentary, lack some leaping features that are well-developed in Ourayia and Chipetaia, suggesting that Mytonius may have relied more on arboreal quadrupedal locomotion than on leaping.  相似文献   

3.
The specialized grasping feet of primates, and in particular the nature of the hallucal grasping capabilities of living strepsirrhines and tarsiers (i.e., ‘prosimians’), have played central roles in the study of primate origins. Prior comparative studies of first metatarsal (Mt1) morphology have documented specialized characters in living prosimians that are indicative of a more abducted hallux, which in turn is often inferred to be related to an increased ability for powerful grasping. These include a well-developed peroneal process and a greater angle of the proximal articular surface relative to the long axis of the diaphysis. Although known Mt1s of fossil prosimians share these characters with living non-anthropoid primates, Mt1 morphology in the earliest crown group anthropoids is not well known. Here we describe two Mt1s from the Fayum Depression of Egypt - one from the latest Eocene (from the ∼34 Ma Quarry L-41), and one from the later early Oligocene (from the ∼29-30 Ma Quarry M) - and compare them with a sample of extant and fossil primate Mt1s. Multivariate analyses of Mt1 shape variables indicate that the Fayum specimens are most similar to those of crown group anthropoids, and likely belong to the stem catarrhines Catopithecus and Aegyptopithecus specifically, based on analyses of size. Also, phylogenetic analyses with 16 newly defined Mt1 characters support the hypotheses that “prosimian”-like Mt1 features evolved along the primate stem lineage, while crown anthropoid Mt1 morphology and function is derived among primates, and likely differed from that of basal stem anthropoids. The derived loss of powerful hallucal grasping as reflected in the Mt1 morphology of crown anthropoids may reflect long-term selection for improved navigation of large-diameter, more horizontal branches at the expense of movement in smaller, more variably inclined branches in the arboreal environment.  相似文献   

4.
Didier Merle 《Geobios》2005,38(4):505
Jsowerbya, nov. gen. (Gastropoda: Muricidae) includes three species from the Eocene of the Paris and Hampshire basins. It increases the number of extinct muricid genera, which curiously represent a very small fraction of the described genera. The species of Jsowerbya, often mistaken for the muricopsine genus Muricopsis, possess a unique combination of characters shared with the subfamilies Ocenebrinae and Ergalataxinae. A cladistic analysis, based on structural homologies of the spiral sculpture, however, suggests that Jsowerbya is closely related to the Ocenebrinae. Thus, Jsowerbya is here regarded as one the most basal Ocenebrinae.  相似文献   

5.
We describe the eosimiid primate fossils collected during the course of four field seasons in the late middle Eocene Heti Formation of central China. In addition to providing new information about the anatomy of Eosimias centennicus, the Heti Formation sample documents substantial taxonomic diversity in the Asian eosimiid radiation. One new genus and three new species of Eosimiidae are proposed here. These include Eosimias dawsonae, n. sp.; Phenacopithecus xueshii, n. gen. and sp.; and Phenacopithecus krishtalkai, n. sp. The anatomy of the upper dentition of eosimiids is described in detail for the first time. As is the case for the lower dentition, a unique combination of primitive and derived traits characterizes the upper dentition of Eosimias and Phenacopithecus. Eosimiid upper molars bear many of the same derived features-including strong protocone cristae and the absence of a postprotocingulum-that have been cited as evidence for a special relationship between anthropoids and certain adapiforms. However, the upper molars of eosimiids further approximate those of other basal anthropoids in having reduced or absent conules and complete lingual cingula. These features are lacking in Periconodon and other adapiforms that have been regarded by some workers as being phylogenetically close to anthropoids. Given that similarities in upper molar anatomy are among the only derived features that can be cited in support of a possible adapiform ancestry for anthropoids, the occurrence of these same features in eosimiids significantly weakens the adapiform hypothesis of anthropoid origins. The holotype maxillary fragment of Phenacopithecus krishtalkai reveals that eosimiids possessed a relatively small infraorbital foramen and a deep lower face between the inferior orbital margin and the alveolar border. Eosimiids therefore lacked the orbital hypertrophy characteristic of living tarsiers and many fossil omomyids and microchoerids. Eosimiids apparently had relatively small orbits, suggesting that they maintained a diurnal activity cycle.  相似文献   

6.
Retinal lesions or other ocular manifestations are serious consequences of infection with the protozoan parasite Toxoplasma gondii. Whilst classically considered a consequence of congenital transmission, recent screening studies estimated that 2% of T. gondii seropositive persons in Europe and North America have retinal lesions, most of them persisting unnoticed. The situation is more dramatic in South America, probably due to the predominance of virulent strains. Some of these strains seem to exhibit ocular or neuronal tropism and are responsible for severe ocular lesions. Despite the medical importance, the physiopathological mechanisms have only recently begun to be elucidated. The particular immune-privileged situation in the eye has to be considered. Studies on French patients showed low or undetectable ocular parasite loads, but a clear Th1/Th17 type immune reaction. Suitable mouse models have appeared in the last few years. Using such a model, IL-17A proved to impair parasite control and induce pathology. In contrast, in South American patients, the parasite seems to be much less efficiently controlled through a Th2 type or suppressive immune response that favors parasite replication. Finally, several host genetic markers controlling immune response factors have been associated with ocular involvement of T. gondii infection, mainly in South America.  相似文献   

7.
New tetrapod footprints belonging to the ichnogenus Hyloidichnus have been discovered in Turkey for the first time, in the lower part of the Çakraz Formation (Northwestern Anatolia) and together with macrofloral imprints of Annularia and Stigmaria. These discoveries confirm the Permian age of the fossiliferous red beds in which the coniferophyte Walchia was previously recorded. Based on the stratigraphic range of Annularia, Stigmaria and Hyloidichnus known elsewhere, a Cisuralian age is proposed for these beds. These new ichno- and macrofloral remains, together with the sedimentological data (mudcracks, rain drops) suggest the presence of captorhinid reptiles living in a palustrine floodplain environment, and under a warm, seasonal climate alternating between humid and relatively long dry seasons. These climatic conditions may have permitted the migration of these captorhinids through Laurasia during the Permian.  相似文献   

8.
Two ent-isopimarane-type diterpenoids were isolated from the New Zealand liverwort Trichocolea mollissima (Hook. f. and Tayl.) Gott., together with a known 1alpha-hydroxy-ent-sandaracopimara-8(14),15-diene. Their absolute structures have been established by modified Mosher's method, X-ray crystallography and by analyses of their CD spectra.  相似文献   

9.
10.
The south Texas Gulf coast is a unique ecosystem that contains a number of different bay systems. We used random amplification of polymorphic DNA (RAPD) markers to assess genetic diversity, differentiation and genetic distance between populations from two different bays that differed significantly in terms of flowering rate and disturbance. We found that while each bay contained a number of unique RAPD profiles, the average genetic diversity in each population was low. Genetic distance between the two populations was also low (Fst = 0.084) and the majority (92%) of the genetic variation was attributed to differences between individuals within populations. The population from the Laguna Madre location, however, was polymorphic for a larger number of markers, had a higher average genetic diversity and a larger number of unique RAPD profiles. The higher level of flowering at this location most likely accounts for the higher diversity.  相似文献   

11.
LINE-1 (L1) is the most represented sequence of the human genome (17% of the total genomic mass). Moreover, it has been proposed for many years and demonstrated more recently that L1 has contributed to the mobilization of pseudogenes, small non-coding RNAs, such as tRNAs or snRNAs, and SINEs. In fact, it is estimated that L1 is responsible for at least 30% of our genome. The mobilization of non-L1 RNAs can occur in different ways and at different steps of the retrotransposition cycle. Here, by looking at U6 snRNA sequences mobilized by L1, we have observed an ancient repeat sequence derived from U6, present in all primate genomes. We were able to trace its origin in Euarchota genomes, most likely during the divergence of the four orders; Scandentia, Dermoptera, Plesiadapiform (extinct) and Primates.  相似文献   

12.
The identification of the polysaccharides from tetrasporophytic plants of nine endemic New Zealand species belonging to the Gigartinaceae, ‘Gigartina’ ancistroclada, ‘G.’ grandifida, Gigartina dilatata, G. divaricata, G. macrocarpa, G. marginifera, G. pachymenioides, G. sp. ‘Lindauer 164’ and Sarcothalia livida using infra-red spectroscopy in conjunction with constituent sugar and glycosyl linkage/substitution analysis is reported. All nine species contain galactans with structures consistent with λ-type carrageenans. Differences in the structures of the galactans in these and a further six previously studied species indicate chemotaxonomically distinct groupings that correspond to Sarcothalia, ‘Sarcothalia’ and Gigartina genera plus some outliers. These distinct, chemotaxonomic groupings are aligned to those determined by rbcL sequence analysis reported in the literature.  相似文献   

13.
Two fossil taxa Tubulifloridites antipodica and T. viteauensis recovered from the Eocene Knysna Lignite of South Africa were examined with scanning (SEM) and transmission electron microscopy (TEM). The details of their sculpturing and wall structure are similar to the same species of fossil dispersed pollen taxa recovered from southwestern Africa and South America. Fifteen species of the woody South African taxa, Brachylaena (9 species) and Tarchonanthus (6 species) were investigated with SEM and TEM. All of the taxa are tricolporate, spherical to slightly prolate, microechinate to echinate and have a bilayered columellate infrastructure, except B.ilicifolia, which has a single columellate infrastructural level with the “granularization” of the outer portion of the infrastructural layer or the inner layer of the tectum. There is a similar distribution of plesiomorphic and derived pollen characters in a number of aster subfamilies and tribes suggesting a similar evolutionary progression of pollen, and pollen wall character evolution was occurring synchronously in a variety of aster subfamilies during the middle Tertiary and that these unique pollen features may be important to the evolution and diversification of the Asteraceae.  相似文献   

14.
Species of the subgenus Leishmania (Leishmania) cause the debilitating disease leishmaniasis on four continents. Species grouped within the Leishmania donovani complex cause visceral leishmaniasis, a life-threatening disease, often associated with poverty, and affecting some 0.5 million people each year. The Leishmania glycoprotein GP63, or major surface protease, is a metalloprotease involved in parasite survival, infectivity and virulence. Here, we show that evolution of the gp63 multigene family is influenced by mosaic or fragmental gene conversion. This is a major evolutionary force for both homogenisation and for generating diversity, even in the absence of sexual reproduction. We propose here that the high GC content at the third codon position in the gp63 family of Old World Leishmania may be higher in multicopy regions, under the biased gene conversion model, because increased copy numbers may lead to increased rates of recombination. We confirm that one class of gp63 genes with an extended 3'end signal, gp63(EXT), reveals genetic groups within the complex and gives insights into evolution and host associations. Gp63(EXT) genes can also provide the basis for rapid and reliable genotyping of strains in the L. donovani complex. Our results confirmed that a more stringent definition of Leishmania infantum is required and that the species Leishmania archibaldi should be suppressed.  相似文献   

15.
A new species of Nelumbo Adanson is described from the Eocene of the Changchang Basin, Hainan Island, South China. This is the first comprehensive report on a fossil Nelumbo species from the Eocene of the Changchang Basin, Hainan Island. The co-occurrence of fruits, tubers, rhizomes with numerous adventitious roots, leaves, and receptacles indicates that the plants grew where they are preserved. These specimens, combined with palynological assemblage and other macrofossils, indicate a tropical or subtropical humid climate in the Changchang Basin from the late early Eocene to early late Eocene.  相似文献   

16.
The continued washing, sorting, and identification of middle Eocene (45 Mya) primates from the Shanghuang fissure-fillings (Jiangsu Province, China) have produced additional hind limb elements. All are isolated elements. The strepsirhine hind limb elements include a first metatarsal and a talus, which are appropriate in size and morphology to pertain to Adapoides troglodytes. Adapoides is interpreted as a quadrupedal-climbing (nonleaping) primate with similarities to living lorises and the fossil primate Adapis. The haplorhine hind limb elements are estimated to span a range of adult body sizes from tiny (17 g) to small (200 g). Included among the new sample of haplorhine hind limb specimens is the smallest primate talus reported thus far. These new postcranial specimens expand our understanding of early haplorhine hind limb anatomy and demonstrate additional similarities between Shanghuang eosimiids and other anthropoids.  相似文献   

17.
18.
Here we report the presence of Spiroplasma 16S rRNA in populations of two parasitic Leptus mites (Leptus sayi; Leptus lomani) and their Agathemera walking stick hosts. In walking sticks Spiroplasmas were detected in the gut, as well as muscle-tissues, but not in eggs. Throughout Argentina 15.4% of L. sayi populations and 14.3% of L. lomani populations surveyed screened positive for Spiroplasma. Phylogenetic analyses (ML, BCMC) place all sequences within the Ixodetis group. Most sequences form a well-supported sister subclade to the rest of Ixodetis. We briefly discuss the role of Leptus mites in the natural transmission of Spiroplasma.  相似文献   

19.
The late-third-instar labial disc is comprised of two disc-proper cell layers, one representing mainly the ventral half of the anterior compartment (L-layer) and the other, the dorsal half of the anterior compartment and most, if not all, of the posterior compartment (M-layer). In the L-layer, Distal-less represses homothorax whereas no Distal-less-dependent homothorax repression occurs in the M-layer where Distal-less is coexpressed with homothorax. In wild-type labial discs, clawless, one of the two homeobox genes expressed in distal cells receiving maximum (Decapentaplegic+Wingless) signaling activity in leg and antennal discs, is specifically repressed by proboscipedia. A fate map, inferred from data on basic patterning gene expression in larval and pupal stages and mutant phenotypes, indicates the inner surface of the labial palpus, which includes the pseudotracheal region, to be a derivative of the distal portion of the M-layer expressing wingless, patched, Distal-less and homothorax. The outer surface of the labial palpus with more than 30 taste bristles derives from an L-layer area consisting of dorsal portions of the anterior and posterior compartments, each expressing Distal-less. Our analysis also indicates that, in adults and pupae, the anterior-posterior boundary, dividing roughly equally the outer surface of the distiproboscis, runs along the outer circumference of the inner surface of distiproboscis.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号