共查询到20条相似文献,搜索用时 15 毫秒
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Martin Ko??ák John W. M. Jagt Robert P. Speijer Peter Stassen Etienne Steurbaut 《PloS one》2013,8(11)
New coleoid cephalopods, assignable to the order Sepiida, are recorded from the Selandian/Thanetian boundary interval (Middle to Upper Paleocene transition, c. 59.2 Ma) along the southeastern margin (Toshka Lakes) of the Western Desert in Egypt. The two genera recognised, Aegyptosaepia n. gen. and ?Anomalosaepia Weaver and Ciampaglio, are placed in the families Belosaepiidae and ?Anomalosaepiidae, respectively. They constitute the oldest record to date of sepiids with a ‘rostrum-like’ prong. In addition, a third, generically and specifically indeterminate coleoid is represented by a single rostrum-like find. The taxonomic assignment of the material is based on apical parts (as preserved), i.e., guard, apical prong (or ‘rostrum-like’ structure), phragmocone and (remains of) protoconch, plus shell mineralogy. We here confirm the shell of early sepiids to have been bimineralic, i.e., composed of both calcite and aragonite. Aegyptosaepia lugeri n. gen., n. sp. reveals some similarities to later species of Belosaepia, in particular the possession of a distinct prong. General features of the phragmocone and protoconch of the new form are similar to both Belocurta (Middle Danian [Lower Paleocene]) and Belosaepia (Eocene). However, breviconic coiling and the presence of a longer ventral conotheca indicate closer ties with late Maastrichtian–Middle Danian Ceratisepia. In this respect, Aegyptosaepia n. gen. constitutes a link between Ceratisepia and the Eocene Belosaepia. The occurrence of the new genus near the Selandian/Thanetian boundary suggests an earlier origin of belosaepiids, during the early to Middle Paleocene. These earliest known belosaepiids may have originated in the Tethyan Realm. From northeast Africa, they subsequently spread to western India, the Arabian Plate and, probably via the Mediterranean region, to Europe and North America. 相似文献
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《Current biology : CB》2014,24(10):R384-R386
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《Current biology : CB》2014,24(11):R518-R520
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Jo?o Francisco Botelho Luis Ossa-Fuentes Sergio Soto-Acu?a Daniel Smith-Paredes Daniel Nu?ez-León Miguel Salinas-Saavedra Macarena Ruiz-Flores Alexander O. Vargas 《PLoS biology》2014,12(9)
From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal–anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal–anterior ossification does not support the dinosaur–bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal–posterior ossification develops from a cartilage referred to as “element x,” but its position corresponds to distal carpal 3. The proximal–posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal–posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications. 相似文献
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The wider availability of information on genomes has become essential for future advances in fungal biology, pathogenesis and epidemiology, and for the discovery of new drugs and diagnostics. MycopathologiaGENOMES is designed for the rapid publication of new genomes of human and animal pathogenic fungi using a checklist-based, standardized format.
相似文献7.
Mario Vaneechoutte 《Human Evolution》2000,15(3-4):243-251
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Sabrina Petra Ramet 《Ethnic and racial studies》2013,36(1):70-87
The mobilization of the countryside has direct consequences for political discourse about national values and in times of social crisis, the ‘conservatism’ of the countryside has the potential to assume an aggressive, offensive posture. When rural mobilization is accompanied by religious revival, group loyalty and so‐called ‘traditional’ values are sacralized. When rural mobilization, ethnic mobilization, and religious revival occur simultaneously, it signifies that the society is undergoing profound destabilization. Examining the case of Serbia, this article argues that while Serbia is, in cultural and social terms, predominantly rural in character, Titoist Communism imposed the values of the city on that culture, while the 1987 coup by Slobodan Milosevic represented, among other things, the triumph of the countryside over the city in Serbia. This article begins by characterizing the countryside in cultural terms, provides documentation of the importance of rural traditions in Serbian society, documents the rural character of the Serbian national movement, connecting its ideology and behaviour with populist appeals, and examines the contribution made by the Serbian Orthodox Church to the mobilization of the Serbian countryside. 相似文献
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《L'Anthropologie》2022,126(3):103051
Networking during the early stages of the Levantine Neolithic appears to have been encouraged by increasing demands for exotics, i.e. non-local commodities. The actual exchange of merchandise stimulated also transmission of knowledge, i.e. innovations. Together these were instrumental in affecting the social fabric of society. It appears that specific geographic settings as well as large-scale communal edifices played a pivotal role in sustaining and promoting Neolithic networking. 相似文献
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González-Romero R Ausió J Méndez J Eirín-López JM 《Journal of molecular evolution》2008,66(5):505-518
The study of histone evolution has experienced a rebirth, for two main reasons: the identification of new essential histone variants responsible for regulating chromatin dynamics and the subsequent contradictions posed by this variability as it pertains to their long-term evolution process. Although different evolutionary models (e.g., birth-and-death evolution, concerted evolution) may account for the observed divergence of histone genes, conclusive evidence is lacking (e.g., histone H1) or totally nonexistent (e.g., histone H2A). While most of the published work has focused on deuterostomes, very little is known about the diversification and functional differentiation mechanisms followed by histone protein subtypes in protostomes, for which histone variants have only been recently described. In this study, we identify linker and core histone genes in three clam species. Our results demonstrate the prevalence of an 'orphon' H1 lineage in molluscs, a group in which the protostome H1 and sperm nuclear basic proteins are on the verge of diversification. They share an early monophyletic origin with vertebrate-specific variants prior to the differentiation between protostomes and deuterostomes. Given the intringuing evolutionary features of the histone H1 family, we have evaluated the relative importance of gene conversion, point mutation, and selection in maintaining the diversity found among H2A subtypes in eukaryotes. We show evidence for the first time that the long-term evolution of this family is not subject to concerted evolution but, rather, to a gradual evolution following a birth-and-death model under a strong purifying selection at the protein level. 相似文献
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The objective of this paper is the structural and narrative reconstruction of representations of ‘nature’, ‘wildlife’ and
‘landscape’, held by rural residents of the Dadia Forest Reserve. Data collection involved in-depth interviews. Employing
a social representations’ approach, we recovered representational elements that are expected in the case of rural belief systems,
such as negative dispositions towards wolves and foxes, as well as elements of an urban adherence, such as nature’s independence.
Representational elements refer to visual aspects of the countryside, which seem compatible with the figurative nucleus of
the rural idyll. Concerning ‘wildlife’, residents focused on vultures, which comprise the main tourist attraction of the reserve.
Scientific knowledge adds to the complexity of the narrative schema, which corresponds to the representation of ‘wildlife’.
Interviewees perceived the rural landscape as an interface between the natural and the human-conditioned environment. Our
study shows that interviewees make no reference to environmental conservation or quality of life issues, as it could be expected
according to relatively wide definitions of the term ‘environmentalism’. Environmental messages reinforced by ecotourism development
seem to be recalled primarily in terms of their compatibility with the perceived economic benefit of local people. Despite
ecotourism development, representational elements that diverge from a tourist version of ‘nature’, ‘wildlife’ and ‘landscape’
were not pronounced within rural belief-systems. Further interventions within the study area are needed, in order to address
a variety of topics under the environmental conservation discourse and raise the environmental awareness of rural residents. 相似文献
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Recumbirostran ‘microsaurs,’ a group of early tetrapods from the Late Carboniferous and Early Permian, are the earliest known example of adaptation to head-first burrowing in the tetrapod fossil record. However, understanding of the diversity of fossorial adaptation within the Recumbirostra has been hindered by poor anatomical knowledge of the more divergent forms within the group. Here we report the results of μCT study of Quasicaecilia texana, a poorly-known recumbirostran with a unique, broad, shovel-like snout. The organization of the skull roof and braincase of Quasicaecilia is found to be more in line with that of other recumbirostrans than previously described, despite differences in overall shape. The braincase is found to be broadly comparable to Carrolla craddocki, with a large presphenoid that encompasses much of the interorbital septum and the columella ethmoidalis, and a single compound ossification encompassing the sphenoid, otic, and occipital regions. The recumbirostran braincase conserves general structure and topology of braincase regions and cranial nerve foramina, but it is highly variable in the number of ossifications and their extent, likely associated with the reliance on braincase ossifications to resist compression during sediment compaction and mechanical manipulation by epaxial and hypaxial musculature. Expansion of the deep ventral neck musculature in Quasicaecilia, autapomorphic among recumbirostrans, may reflect unique biomechanical function, and underscores the importance of future attention to the role of the cervical musculature in contextualizing the origin and evolution of fossoriality in recumbirostrans. 相似文献
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《Current biology : CB》2019,29(16):R792-R794
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SEAN F. Craig LAWRENCE B. Slobodkin GREGORY A. Wray CHRISTIANE H. Biermann 《Evolutionary ecology》1997,11(2):127-143
Animal polyembryony appears to be paradoxical because it clones an unproven genotype at the expense of genetic diversity in a clutch. However, it is employed by at least 18 taxa in six phyla (excluding instances of occasional twinning). Most polyembryony occurs in parasitic stages or in other environments whose quality is not predictable by the mother; in some instances, it compensates for a constraint on zygote number. We predict that polyembryony is likely to evolve when the offspring has more information regarding optimal clutch size than the parents. 相似文献