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51.
John W. Salter's papers of 1856 and 1857 reported trace and body fossils from rocks of the Longmyndian Supergroup, Shropshire, that conventional wisdom had deemed literally “Azoic.” The significance of this work is reflected by its mention in On the Origin of Species, where it is cited as evidence for the existence of life prior to the Cambrian radiation. This study of Salter's historic specimens combined with recent field studies confirms that these structures likely represent microbial rather than metazoan markings. Nevertheless, this review confirms Salter as the unheralded founder of Precambrian palaeontology, many years before the existence of a Precambrian fossil record was widely known. This study also gives credit to a highly skilled palaeontologist, who appears to have struggled with psychological problems throughout his life. Salter had once been Adam Sedgwick's “youthful and cheerful companion” in the field, prior to embarking on an initially successful Geological Survey career. He was a widely renowned expert on Palaeozoic palaeontology, especially trilobites, but eventually fell into serious depression, which culminated in his suicide in 1869. Study and reinterpretation of his original materials reaffirms the importance of Salter's discoveries, and the Longmynd for our understanding of late Ediacaran palaeobiology. 相似文献
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53.
Gary A. P. Gibson 《ZooKeys》2013,(283):59-69
The extinct Eocene Baltic amber genus Propelma Trjapitzin 1963 is removed from synonymy under Eupelmus Dalman 1820 (Hymenoptera, Eupelmidae, Eupelminae) and treated as a valid genus within Neanastatinae Kalina 1984 based on examination of the holotype female of Propelma rohdendorfi Trjapitzin. Propelma rohdendorfi is redescribed, illustrated by photomacrographs, and compared to other described extant and extinct genera of Neanastatinae. Taxonomic, morphological and geological diversity of Neanastatinae relative to Eupelminae and Calosotinae is also discussed relative to potential age of the subfamily. 相似文献
54.
MtDNA sequences (396 bp cytochrome b and 369 bp 12S rRNA) from recent material and old museum specimens indicate Pleurodeles poireti and P. waltl form independent clades with 7.76% genetic divergence. Within P. poireti, populations from Djebel Edough, NE Algeria are very distinct with 6.12% genetic divergence from the remainder and may deserve separate species status. Away from Djebel Edough, P. poireti consists of three distinct clades (coastal NW Tunisia; central N Algeria; Constantine plus inland NW Tunisia) with a maximum genetic divergence of only 1%. P. waltl contains two clades with 2.96% genetic divergence, one in SE and E Spain plus north Morocco, the other in Portugal and SW and central Spain. Pleurodeles probably invaded NW Africa from SW Europe during the Messinian Salinity Crisis, when land contact was first established at 5.6 Ma, and then interrupted at 5.3 Ma. Molecular clocks, calibrated in the assumption that the latter event separated P. waltl and P. poireti, suggest that Pleurodeles diverged from its sister taxon, Tylototriton, at about 8.6–10 Ma. Djebel Edough P. poireti separated at about 4.2 Ma, perhaps through isolation on a temporary, now ‘fossil’, island initiated by the Messinian crisis. Differentiation in remaining P. poireti may have been caused by Pleistocene climatic fluctuations, while bifurcation in P. waltl appears to have taken place in the Pliocene approximately between 3.2 and 2 Ma. This species reached Morocco very recently, perhaps as a result of human introduction. Use in Pleurodeles of the slower divergence rates estimated in some other salamandrids results in a less parsimonious historical hypothesis that does not fit known geophysical events. 相似文献
55.
Gengo Tanaka 《Hydrobiologia》2005,538(1-3):231-242
The naupliar eye of podocopid ostracods is a useful character for considering evolution in photic environments. Based on external
morphologies and histological observations, naupliar eyes are here categorized into six types. The fossil record demonstrates
that the major evolutionary changes in podocopid naupliar eyes occured after the Ordovician. Eye types 1 and 2 are not joined
to the carapace by the hypodermal cells, and these two types are found in Palaeozoic ostracods. Eye type 3, 4, 5 and 6 are
extended on eye stalks, tightly joined to the carapace by the hypodermal cells, and use the carapace as the refractive cuticle
lens. Eye type 3 appeared in the Permian, and eye types 4, 5 and 6 appeared in the Early Jurassic. The design of the podocopid
naupliar eye diversified in the Early Jurassic. 相似文献
56.
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探讨古环境和古气候变化与哺乳动物演化之间的关系是目前古生物学研究领域中的一个热点,而哺乳动物化石牙齿釉质的碳、氧同位素分析是恢复古环境和古气候的一个重要手段。以往的哺乳动物化石牙齿釉质稳定同位素分析多集中在大哺乳动物化石,这主要是受到技术手段的限制,所需的样品量较大所决定的。但最近几年随着激光和离子显微探针技术的应用,对小哺乳动物化石(如啮齿类和兔形类)的牙齿釉质碳、氧同位素的分析和应用日趋成熟和广泛。除了传统的化学处理方法之外,对小哺乳动物化石牙齿釉质碳、氧同位素的分析还有以下三种方法:1)激光剥蚀气相色谱/同位素比值质谱分析;2)直接激光氟化技术;3)离子显微探针技术(SHRIMPII)。这些技术需要的样品量少,对标本的破损小,准确度和精密度高,所以在小哺乳动物化石和一些珍贵标本(如古人类化石)的稳定同位素分析中起到了重要作用。相对于大哺乳动物化石,小哺乳动物化石数量多、演化速度快,更能反映多个层位长时间序列的古环境和气候变化;而且小哺乳动物通常没有长距离迁徙的行为,栖息地局限,所以更能准确反映化石埋藏地点的古环境和气候状况。 相似文献
59.
Anumeha Shukla R. C. Mehrotra Nivedita Mandal Mahesh G. Thakkar 《Historical Biology》2013,25(8):970-977
The Kutch region of western India (Gujarat State) is today arid to semiarid and characterised by mostly ephemeral streams which carry water during the monsoon. The uneven distribution of rainfall and disturbed topography are the result of climate change during the Cenozoic period. Two fossil woods, namely Bauhinium palaeomalabaricum Prakash and Prasad (Fabaceae) and Ebenoxylon indicum Ghosh and Kazmi (Ebenaceae), are described from Kutch in order to provide insights into the palaeovegetation and palaeoclimate. Because the modern representatives of the present and previously described taxa from the same horizon are thermophilic in nature and grow in evergreen to deciduous forests, a warm and humid climate is interpreted. Furthermore, the finding of some mangrove taxa in the assemblage indicates the lagoonal to intertidal environment at the time of deposition. 相似文献
60.
Austin Boyd 《Historical Biology》2013,25(1-2):1-15
The mid-Pleistocene Kolymbia Flora of Rhodes, Greece occurs in the Lindos Bay Clay facies group of the Rhodes Formation and was deposited in a marine setting at about a depth of 200 m. Recorded in the flora are the youngest presence of Glyptostrobus in the eastern Mediterranean, an extinct species of Pinus very similar to the modern relict Pinus canariensis, and a new species of the disjunct Cedrus. These taxa indicate that some relict plant taxa existed on Rhodes later than previously recognised. The late presence of Taxodiaceae in the eastern Mediterranean may demerit its usefulness for determining the Pliocene–Pleistocene boundary. The finding of Liquidambar, Zelkova and Fagus in the flora supports the idea of Rhodes, and possibly the eastern Mediterranean, as a refugium during the mid-Pleistocene. Similar fossil assemblages should be found in adjacent Turkey because the Lindos Bay Clay records an extensive marine transgression probably resulting from graben tectonics that lead to the ultimate separation of Rhodes from mainland Turkey. 相似文献