摘要:

Clarkson, E. N. K.&Henry, J. L.: Structures coaptatives et enroulement chez quelques Trilobites ordoviciens et siluriens. [Coaptative structures and enrollment in some Ordovician and Silurian trilobites.]Certain trilobites possessed highly adapted structures on the cephalon and pygidium, and sometimes also the thorar, which ensured very close interlocking of opposing surfaces during enrollment. Different kinds of structures are described in detail in selected Ordovician and Silurian genera. There is a simple ‘press‐stud’ mechanism axially situated on the opposing cephalic and pygidial doublures ofKloucekia micheli, whereas in various species ofCrozonaspisand inKloucekia dujardinia projecting cephalic beak fits into an excavation under the caudal spine. The cephalic beak and corresponding pygidial excavation seemingly evolve towards a more pronounced form in successive species throughout time.Colpocoryphe rouaulti, by contrast, has a pygidial protuberance interlocking with a cephalic excavation. Complete specimens ofEncrinurus tuberculatusandE. variolarishave very complex contact surfaces along opposing doublures, with various kinds of interlocking struc

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01186.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Knox, Robert W. O'B.: Ichnogenus Corophioides.A re‐examination of syntypes and topotypes of the type species,Corophioides polyupsilon, shows that its structure is distinct from that of the other forms ascribed to the ichnogenus. An emended diagnosis of the ichnogenus is given, restricting it to forms which show a true U‐within‐U structure. Most of the species formerly included inCorophioidesSmith 1893 can be referred toDiplocraterionTorell 1870, but in some cases a re‐examination of the type material is ne

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01187.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Sheehan, P. M.: The relation of Late Ordovician glaciation to the Ordovician‐Silurian changeover in North American brachiopod faunas.The Ordovician‐Silurian changeover of brachiopod faunas in North American epicontinental seas involved the abrupt extinction of endemic Late Ordovician stocks and subsequent repopulation of North American seas by Old World taxa. The Late Ordovician Gondwanaland glaciation may have lowered sea levels sufficiently to place severe stress on the widespread shallow marine faunas in North America, resulting in their eventual extinction. The Late Ordovician depositional history in North America is not well enough known to establish the presence of a latest Ordovician regression, but the earliest Silurian was an interval of off‐lap in North America. Therefore, the glacial lowering of sea level is considered to be the most likely cause of the faunal chang

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01188.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Fagerstrom, J. A.&Saxena, K. M. L.: Intracoenosteal variation in a Devonian stromatoporoid.Statistical analysis of four different features of coenosteal morphology measured in sixteen randomly distributed vertical and tangential thin sections from a specimen ofSyringostroma sherzeri(Grabau) from the Detroit River Group near Ingersoll, Ontario, indicates that although the degree of variation is very high, the variation in a single section is representative of the variation in the entire coenosteum. This discovery may therefore be regarded as a partial vindication of current practice in stromatoporoid taxonomy of baaing identifications on examination of one vertical and one tangential sectior. Furthermore, this study indicates that certain morphological features are less variable than others and are therefore of greater value as taxonomic criteria. In cases where the number of measurements per section is small, tests of the significance of differences based on a comparison of the medians, rather than means, is preferred because such tests do not assume that the data are normally distributed.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01189.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Krassilov, V.: Mesozoic plants and the problem of angiosperm ancestry.Trends leading to the foliar and floral structures of angiosperms may be deduced by comparison with Mesozoic gymnosperms. TheDebeya‐Fontaineagroup of Cretaceous angiosperms closely resembles the Early MesozoicScoresbyagroup of pteridosperms with regard to leaf characters. The bivalved capsules of JurassicLeptostrobus, with stigmatic bands, are regarded as the forerunners of certain types of angiosperm carpels. The angiospermous characters arose in several lineages of gymnosperms and were probably accumulated by non‐sexual transfer of genetic material. The earliest angiosperm mega‐ and microfossils have been reported from the Middle and Upper Jurassic of the northern hemisphere. Most of these angiosperms were confined to chaparral‐like communities dominated by shrubby conifers and cycadophytes. The rise of angiosperms was promoted by the climatic changes and the simultaneous rise of

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01190.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Dslingwater J. E.: The cuticle of a eurypterid.A description is given of the cuticular ultrastructure ofPterygotus (Pterygotus) ludensisSalter, 1859 from the ‘Passage Beds’ at Ludlow, Shropshire, England. Scanning electron microscope investigations revealed laminar units composed of fibrous elements, and fine perpendicular structures. The laminae resemble those of modern arthropod cuticles and some of the perpendicular elements may be pore‐canals. Three main layers are described; it is not possible to equate these with the histochemical subdivisions of extant cut

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01191.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Stearn, C. W.&Riding, R.: Forms of the hydrozoanMilleporaon a Recent Cora reef.Distribution of the calcareous hydrozoanMilleporain the shallow water off the west coast of Barbados supports the view that morphologic variation in this genus is not primarily the response of a single species to environmental factors. Four forms are present on the fringing reef (1 to 6 m depth) and on an offshore ridge (11 to 17m depth). Branching, bladed, and boxwork forms co‐exist at depths below 2 m and are thought to be genetically distinct (biospecies). They are equivalent toM. alcicornis, M. complanata, andM. squarrosarespectively. With decreasing depth they disappear in the order: branching, bladed, boxwork. This sequence reflects increasing colony strength and appears to be governed by increasing water agitation. The encrusting form is commonest in very shallow water, but also occurs in deeper water growing on gorgonians. It appears to be an environmental growth form of the other specie

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01192.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Cowen, R., Gertman, R.&Wiggett, Gail: Camouflage patterns inNautilus, and their implications for cephalopod paleobiology.Formal analysis of the pigment patterns of adultNautilusshows that they are perfectly camouflaged for life in open water. But because of their accretionary growth pattern, juveniles are not fully camouflaged for open water: this supports previous suggestions that youngNautilusare benthonic. The principles of camouflage are used to re‐assess some facets of cephalopod paleobiology. The life orientation of some early cyrtocones is re‐interpreted. ‘Ornament’ on ammonoids is seen as camouflage structure, and we infer photic‐nektonic, photic‐benthonic, and aphotic habitats for three major morphological groups of ammonites. Sexual dimorphism in ammonites was probably accompanied by sexual separation in habitat, except for a short (annual) mating season. This is not inconsistent with modern cephalo

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01193.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Palaeontology cannot progress without neontology, and the palaeontologist must often engage himself in investigations of recent plants and animals. There is, however, a clear tendency among palaeontologists to avoid the problems of hard preparation and incomplete documentation of life and death in the rocks. Resources intended for palaeontology are increasingly used for investigations of Recent organisms without more apparent relations than botany and zoology in general to urgent palaeontological problems. More fossil‐oriented palaeontology is advocate

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1973.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY