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1.
Abstract: Ontogenies are described for the first time for three species of Early Cambrian oryctocephalid trilobites: the oryctocephaline Changaspis elongata Lee, in Chien and the oryctocarines Duyunaspis duyunensis Chang and Chien, in Zhou et al . and Balangia balangensis Chien from the Balang Formation in eastern Ghuizhou Province, south-west China. The complete protaspid to holaspid ontogeny for Duyunaspis duyunensis and incomplete meraspid to holaspid ontogenies for Changaspis elongata and Balangia balangensis are described. The relative degree of ontogenetic variation within the lineage Duyunaspis duyunensis – Balangia balangensis is analysed and indicates that Balangia may have evolved from Duyunaspis by paedomorphosis. Decrease in thoracic segment number and concomitant increase in pygidial segment number in the later genus mirrors the pattern seen in the evolution of another oryctocephalid genus, Arthricocephalus . In both cases, selection was probably targeting an increase in cephalic convexity. This resulted in the evolution of a larger pygidium due to increased elevation of the axis above the substrate. The ontogenetic development of Changaspis provides evidence supporting the view that the Oryctocarinae may be considered as paedomorphic descendants of the Oryctocephalinae. 相似文献
2.
Several hundred specimens of a tiny olenid trilobite, Ctenopyge ceciliae sp. nov., have been found in stinkstone nodules in the upper Cambrian Peltura scarabaeoides Zone in southern Sweden. This exceptionally spinose form is known only from disarticulated specimens, but is quite well preserved, and all growth stages are represented. The early ontogenetic stages are exceptionally small, the protaspis being only half the size of that of the associated Peltura species. There may have been no more than three thoracic segments. Thus the whole ontogeny was compressed, and this together with the very small size of the adult indicates a true miniaturisation. Whereas the likely control of the origin of the tiny C. ceciliae was basically progenesis, the extreme spinosity had a different origin; allometric growth or possibly peramorphosis. C. ceciliae is small enough for the spines to have appreciably retarded sinking through frictional effects, and this small trilobite is interpreted as a free-swimming or floating form. 相似文献
3.
The genus Ctenopyge is known mainly from disarticulated sclerites and from rare complete specimens flattened in shales. Hitherto, very few specimens have been found preserved intact and in three dimensions. In a recently discovered fauna, however, in the Peltura minor Subzone in Västergötland, central Sweden, there occur several species of Ctenopyge , of which many are complete and superbly preserved; moreover they occur at all stages of growth. Of these the abundant Ctenopyge ( Eoctenopyge ) angusta Westergård, 1922 is described and reconstructed here as an adult, and the entire ontogeny is documented for all post–protaspid growth stages. Many characters typical of the adult, such as the long genal spines and the caudal spine, develop very early in ontogeny, and the relative dimensions of the cranidium do not greatly change during growth. Macropleural spines, however, develop later. The transitory pygidium, relatively large and shield–shaped in the early meraspid, later becomes very small as the ten thoracic segments are liberated; a median spine develops on the last thoracic segment only at the holaspid stage. Instar groupings can be clearly distinguished for the early stages. Recurrent associations of sclerites are interpreted as moulting configurations. As reconstructed, the genal spines are horizontal and parallel with the extended thorax; an adaptation which presumably allowed the trilobite to rest on the sea floor. 相似文献
4.
Abstract: The ontogeny of the trilobite Protopeltura aciculata (Angelin, 1854) is described on the basis of material from the upper Cambrian (Furongian) of Andrarum (Skåne) and Hjelmsäter (Västergötland), Sweden. P. aciculata is present in the Parabolina brevispina and Parabolina spinulosa zones. Protopeltura aciculata is represented by all stages of growth, from early protaspides to holaspides, although most of the specimens are disarticulated and precise degrees are unknown. The cranidia have therefore been allocated to five morphological groups. Cuticular sculpture of the cranidia changes throughout ontogeny. Large tubercles are present in earlier stages, disappear gradually in middle meraspid stages and are replaced with a very faint granulation. The transitory pygidium, relatively large and shield‐shaped with upwardly and backwardly directed marginal spines in early meraspides, later becomes very small, triangular‐shaped and lacking spines as a late meraspid and holaspid. The development of hypostomes and librigenae is also described. Protopeltura aciculata shows major intraspecific variations throughout development, especially regarding the pygidium where variation is much less constrained than in many other olenids. This high developmental plasticity may be a survival strategy for a trilobite living in a stressed environment. Protopeltura inhabited a dysoxic environment, possibly unusually prone to localised spreading of anoxic or toxic water. Some morphs may have been less vulnerable than others to such stresses, surviving by chance and thus enabling the species to continue. 相似文献
5.
A new coelacanth genus from the Famennian (Upper Devonian) of South Africa is described, principally from presumed juveniles. S erenichthys kowiensis gen. et sp. nov. uniquely shares with Diplocercides a ventral expansion of the elbow‐like lachrymojugal, as well as a symmetrical diphycercal tail supported by expanded neural and haemal spines and radials. Serenichthys is distinguished from Diplocercides by a number of derived characters, including possession of longer anterior parietals, a more crescent‐shaped postorbital with a more anteriorly positioned infraorbital canal, and a far smaller squamosal, which is well separated from the skull roof. By contrast, Serenichthys appears to lacks a second dorsal fin lobe, a derived feature present in Diplocercides. Most specimens of Serenichthys are between 3 and 6 cm in length. They have large eyes, and dermal bones of the skull ornamented with long wavy ridges, similar to the dermal ornament of other Devonian coelacanths such as Gavinia. Larger isolated operculae also collected from the Waterloo Farm locality and attributed to Serenichthys indicate that with growth the ridges on the dermal bones transformed into elongate tubercles, reminiscent of those of Diplocercides and Carboniferous taxa. Phylogenetic analysis resolves Serenichthys as the sister group of Holopterygius and all known post‐Devonian coelacanths. The clade including the unusual leaf‐shaped coelacanths, the Devonian Holopterygius and Carboniferous Allenypterus, branches from the coelacanth lineage immediately crownward of Serenichthys. The presence of abundant juveniles within an estuarine setting strongly parallels the discovery of similarly sized juveniles of Rhabdoderma exiguus together with eggs and yolk‐sack larvae in the Upper Carboniferous Mazon Creek biota. It is therefore argued that Serenichthys, like Rhabdoderma, was using the sheltered estuarine environment as a nursery. © 2015 The Linnean Society of London 相似文献
6.
Logical connections exist between evolutionary modularity and heterochrony, two unifying and structuring themes in the expanding field of evolutionary developmental biology. The former sees complex phenotypes as being made up of semi-independent units of evolutionary transformation; the latter requires such a modular organization of phenotypes to occur in a localized or mosaic fashion. This conceptual relationship is illustrated here by analyzing the evolutionary changes in the cranidial ontogeny of two related species of Cambrian trilobites. With arguments from comparative developmental genetics and functional morphology, we delineate putative evolutionary modules within the cranidium and examine patterns of evolutionary changes in ontogeny at both global and local scales. Results support a case of mosaic heterochrony, that is, a combination of local heterochronies affecting the different parts individuated in the cranidium, leading to the complex pattern of allometric repatterning observed at the global scale. Through this example, we show that recasting morphological analyses of complex phenotypes with a priori knowledge or hypotheses about their organizational and variational properties can significantly improve our interpretation and understanding of evolutionary changes among related taxa, fossil and extant. Such considerations open avenues to investigate the large-scale dynamics of modularity and its role in phenotypic evolution. 相似文献
7.
Tao Dai Xingliang Zhang 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2013,46(2):262-273
A detailed investigation of the morphology and ontogeny of the redlichioid trilobite Eoredlichia intermediata (Bulletin of the Geological Society of China, 3–4, 1940, 333) from the lower Cambrian Yu'anshan Member of the Heilinpu Formation, in Kunming, Yunnan Province, southwest China, is presented. The new material comprises a relatively complete ontogenetic series ranging from the early meraspid to the holaspid period, which reveals more details on morphological variation such as the appearance of bacculae in some holaspid specimens, contraction and disappearance of fixigenal spines, and macropleural spines of the first and second thoracic segments, which are all documented for the first time and can also be used as developmental markers defining ontogenetic phases. Two distinct morphotypes, possibly an expression of intraspecific variation or sexual dimorphism, are distinguished by the morphology of pleural spines of the second thoracic segment in meraspid degree 14 and holaspides. The trunk segmentation schedule of E. intermediata is also discussed and conforms to the protarthrous developmental mode. The distinction of the thoracic region into two portions can be observed during late meraspid and early holaspid periods, which might be considered as a reference for a better understanding on the relationship of tagmosis and growth segmentation among the Cambrian redlichiid trilobites. 相似文献
8.
9.
陕西韩城寒武系出露良好,化石丰富,从下寒武统上部至奥陶系为连续沉积,底部平行不整合覆盖厚约20m的霍山组石英砂岩之上。本区寒武 系主要以紫色和黄色泥页岩、泥灰岩、灰岩和白云质灰岩为主,张夏组主要以鲕状灰岩为主,夹生物碎屑灰岩,三叶虫主要有Changqingia chalcon,Changqingia luia sp.nov.,Manchuriella macar,Lianglangshania hueir ensis,Crepicephalia convexus,Eilura quadrata,Eilura(?)hanchengensis sp.nov.,Anmocarella chinensis,Dorypyge pergranosa,Dorypyge richthofeni,Liopeishania lubrica,Liopeishania marginata和Damesella paronai等。三山子组以白云质灰岩和灰质白云岩为主,在底部的白云质灰岩中产三叶虫Blackwelderia sp.,Damesops convexus和Cyclolorenzella acalle等,其中、上部未采到化石。 相似文献
10.
Przemysław Świś 《Historical Biology》2013,25(9):1161-1169
Abstract Alternognathus is a cavusgnathid conodont believed to be a relative and possible ancestor of the Siphonodella lineage, which is of crucial importance to the biostratigraphy of the Devonian–Carboniferous transition, as well as the Early Carboniferous Clydagnathus, with the most completely known soft tissue anatomy among conodonts. Specimens of Alternognathus from the Kowala quarry in central Poland have their basal cavities lacking any mineralised basal body tissue, exposing rhythmic growth increments of probably daily nature. This enables calibration of ontogeny and population dynamics of Alternognathus in absolute time units and to estimate the correspondence between data derived from isolated oral apparatus elements and the animal body size. The peak of mortality, probably resulting from predation, occurred at 18–28 days of the Alternognathus oral apparatus element secretion and the inferred whole animal length of about 1.6–2.9 cm. Based on analogy with present-day fish, the actual beginning of individual life presumably preceded the initiation of the mineral tissue secretion for about 8 days. This makes the dominant life cycle close to the lunar month length and suggests analogy to cyclic mortality of modern tropical organisms due to full moon light influence on their daily vertical migration. 相似文献
11.
Danita S. Brandt 《Ichnos》2013,20(1):28-43
Rusophycus is an ichnogenus comprising shallow burrows generally attributed to trilobites and other arthropods. The paleoethological interpretation of these structures is not conclusively known; workers variously have attributed the ichnogenus to feeding, resting, hiding/escape, hunting or nesting behaviors. Rusophycus morphology varies from unornamented, bilobed forms to forms that preserve details of ventral anatomy of the trace maker. Rusophycus occurs as single or multiple impressions. Some examples of multiple-Rusophycus assemblages are clearly the result of the activity of a single animal (e.g., serially arranged impressions of the same size), but others represent the activity of several individuals. Associated traces representing multiple individuals are especially interesting, for they may give evidence of complex behavior, for example, interactions between the trace makers. Some of the multiple-trace assemblages show alignment (congruent anterior-posterior orientation of the individuals) suggesting rheotactic behavior; other assemblages comprise randomly oriented traces. The difference between the aligned and randomly oriented assemblages may reflect differences in the current energy and amount of available food, and may also suggest the following feeding modes for these benthic-feeding arthropods: (1) alignment with head into the current in resource-poor environments, (2) orientation with head at an oblique angle to the current in high-energy, resource-poor environments, and (3) random orientation in low-energy, resource-rich environments. 相似文献
12.
LOREN H. SMITH 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1998,31(2):99-110
Asymmetry in fossils can arise through a variety of biological and geological mechanisms. If geological sources of asymmetry can be minimized or factored out, it might be possible to assess biological sources of asymmetry. Fluctuating asymmetry (FA), a general measure of developmental precision, is documented for nine species of lower Paleozoic trilobites. Taphonomic analyses suggest that the populations studied for each taxon span relatively short time intervals that are approximately equal in duration. Tectonic deformation may have affected the specimens studied, since deviations from normal distributions are common. Several measures of FA were applied to 3–5 homologous measures in each taxon. Measurement error was assessed by the analysis of variance (ANOVA) for repeated measurements of individual specimens and by analysis of the statistical moments of the distributions of asymmetry measures. Measurement error was significantly smaller than the difference between measures taken on each side of a specimen. However, the distribution of differences between sides often deviated from a mean of zero, or was skewed or kurtosic. Regression of levels of FA against geologic age revealed no statistically significant changes in levels of asymmetry through time. Geological and taphonomic effects make it difficult to identify asymmetry due to biological factors. Although fluctuating asymmetry is a function of both intrinsic and extrinsic factors, the results suggest that early Cambrian trilobites possessed genetic or developmental mechanisms used to maintain developmental stability comparable to those of younger trilobites. Although the measures are biased by time averaging and deviations from the normal distribution, these data do not lend strong support to 'genomic' hypotheses that have been suggested to control the tempo of the Cambrian radiation. 相似文献
13.
本文研究了广西荔浦上泥盆统榴江组上部扁豆状灰岩中所含的法门期竹节石2属3种,其产出层位分别为牙形刺化石带的 Palmatolepis crepida带和 Pa.marginifera带。 相似文献
14.
Tae-Yoon Park 《Geobios》2011,44(5):481
The base of the Furongian Series in the Sino-Korean Block has not been clearly defined due to the lack of the index taxon, Glyptagnostus reticulatus. The Sesong Formation of the Taebaek Group, Taebaeksan Basin, Korea, has been known to range from the Guzhangian Stage of the Cambrian Series 3 to the middle Furongian Series, hence embracing the base of the Furongian Series. Silicified polymerid trilobites were recovered from the middle part of the Sesong Formation. Described are a total of 18 polymerid species of 13 genera: Neodrepanura sp. 1, Teinistion sp. 1, Huzhuia sp. 1, Huzhuia sp. 2, Liostracina simesi, Liostracina sp. 1, Parachangshania monkei, Parachangshania rectangularis nov. sp., Placosema bigranulosum, Fenghuangella laevis nov. sp., Baikadamaspis jikdongensis nov. sp., Baikadamaspis sp. 1, Prochuangia mansuyi, Maladioides coreanicus, Alataspis sesongensis nov. gen., nov. sp., Chuangia sp. 1, and ceratopygids genus and species indeterminate 1 and 2. The stratigraphic occurrence of these trilobites provides a basis for recognition of five zones across the base of the Furongian Series (in ascending order): the Neodrepanura, Liostracina simesi, Fenghuangella laevis, Prochuangia mansuyi, and Chuangia zones. The Neodrepanura and Chuangia zones are provisionally adopted from the previous biostratigraphic scheme, while the three other ones are newly proposed. The recommended base of the Furongian Series in the Taebaek Group of Korea coincides with the base of the Fenghuangella laevis Zone, which appears to represent an episode of profound trilobite faunal turnover. 相似文献
15.
《Palaeoworld》2016,25(4):600-615
Conodont biostratigraphical work was done at four sections recently found with occurrence of the rhynchonellide brachiopod genus, Dzieduszyckia Siemiradzki, in southern Guangxi and in the border area between Dushan County of Guizhou and Nandan County of Guangxi, South China. These sections represent two different types of facies, i.e., carbonate platform and intraplatform basin. The conodont analysis reveals that this genus occurs in the Upper triangularis Zone and the Middle crepida Zone at the Dazhai Section, through the Lower to Upper crepida zones at Dalong, and is restricted within the Upper rhomboidea Zone at the two intraplatform basin sections (Changtang and Duli). This result demonstrates that the occurrence of these peculiar rhynchonellide brachiopods in South China, regardless of the depositional environments, is within the Lower Famennian instead of the previously suggested Upper Famennian. Furthermore, this brachiopod genus in South China began to inhabit on the carbonate platform almost since the beginning of the Famennian and did not extend to the intraplatform basin facies until the late Early Famennian.Available biostratigraphic data indicate that during the Early and Middle Famennian, Dzieduszyckia is widely distributed not only in South China, but also throughout the world, such as Morocco and southern Ural.Observation on the new collections from the four studied sections reveals that the peculiar rhynchonellide brachiopods have a great morphological variation within each section. Significant differences existed among the collections from different sedimentary settings and localities, probably reflecting the environmental and geographic constraint on the morphology of Dzieduszyckia. Samples from different layers in the same section have nearly identical morphological variation, suggesting the temporal inheritance in morphology of the rhynchonellide brachiopod. 相似文献
16.
描述了陕西南郑梁山上奥陶统南郑组及临湘组的三叶虫 Kweichowilla liangshanensis sp. nov.,Triarthrus sp. 及 ? Aspidaegalina liangshanensis Chen (sp. nov.).前两者产于南郑组,后者产于临湘组.Kweichowilla 属系首次在陕西上奥陶统发现,Aspidaegalina 属在我国上奥陶统也是首次见及. 相似文献
17.
SHARON D. KLAVINS 《Botanical journal of the Linnean Society. Linnean Society of London》2004,144(3):275-287
New collections of pyritized axes of the lycophyte Wexfordia hookense have been made from the Upper Devonian (uppermost Famennian) type locality at Sandeel Bay, County Wexford, in south-eastern Ireland. The specimens reveal additional histological features that permit reinterpretation of the morphology of this taxon and reevaluation of its taxonomic affinities. Wexfordia is shown to possess both secondary xylem, with narrow, uni- to biseriate rays, and periderm. The range of variation in relative amounts of primary and secondary xylem can be correlated with position in the mature plant. This evidence indicates that Wexfordia was a small tree rather than an herbaceous form. Fine structure of tracheids and additional anatomical features strongly support affinities with Carboniferous arborescent Isoetales, rather than Devonian Protolepidodendrales, and further support the hypothesis that radiation in this lineage was well underway prior to the Carboniferous. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 275–287. 相似文献
18.
FRANCIS LETHIERS 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1983,16(1):39-49
About one hundred papers and studies have been utilized for a synthesis of ostracode palaeobiogeography during the Frasnian and Famennian. The pelagic entomozoid species have worldwide distributions: they are not used for distinguishing the palaeobiogeographic areas. Five provinces probably existed during the Frasnian and five during the Famennian. The palaeobiogeographic area of the Palaeotethys is constant during this time. There are important faunistic relations between the Western Canadian Platform and the Russian Platform, that is to say, along the Northern margin of the North-Atlantic Continent, during Late Devonian time. The province of Southeastern Asia remains isolated. The number and limits of the palaeobiogeographic areas have been controlled by climate and some geographical barriers. 相似文献
19.
Z. A. Tolokonnikova 《Paleontological Journal》2007,41(5):537-541
New bryozoans from the Upper Devonian (Famennian) of the borderlands of the Kuznetsk Coal Basin are described: Orthopora tomensis sp. nov. and Minussina incrustata sp. nov. 相似文献
20.
CATHERINE CRÔNIER JEAN-CHRISTOPHE AUFFRAY PHILIPPE COURVILLE 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2005,38(2):123-135
The best insight into the development of Devonian phacopids has been obtained from Trimerocephalus lelievrei Crônier & Feist, 1997, a Famennian phacopine from Morocco, where changes in size and shape have been quantified. In this study, a morphometric approach has been used: (1) to retrodeform and then establish patterns of morphological variation in a well preserved but tectonically deformed assemblage belonging to another phacopine species Weyerites ensae (Richter & Richter, 1926), a Famennian phacopine from Thuringia, and (2) to establish patterns of developmental and evolutionary changes within two closely related species: Weyerites ensae and Trimerocephalus lelievrei. The method of retrodeformation using a set of discrete points presumed to be homologous on all studied individuals, has demonstrated that the next analyses are possible on the retrodeformed material as compared to the undeformed material. Morphometric analysis based on outline analysis has permitted demonstration of progressive shape change in agreement with ontogenetic ordination and a comparison of changes in size and shape in Weyerites ensae. The main changes in shape appear to occur in the meraspid period, whereas increase in size takes place mainly in the holaspid period. This pattern, already reported for Trimerocephalus lelievrei, can be generalized for phacopine trilobites from the Late Devonian. Moreover, the comparison of the two ontogenetic trajectories has shown that most of the differences are related to 'structural' changes, probably linked to a relative pre- post-displacement. The results suggest that ecological adaptation may be studied by examining the changes in development that occur within species through time and space. 相似文献