摘要:

Thulborn, Richard A. 1978 07 15: Aestivation among ornithopod dinosaurs of the African Trias.Lethaia. Vol. 11, pp. 185–198. Oslo. ISSN 0024–1164.Dental and circumstantial evidence supports the theory that ornithopod dinosaurs of the African Red Beds responded to seasonal changes in their environment by resorting to aestivation (dry season dormancy). One group of ornithopods. the heterodontosaurids. apparently suppressed tooth replacement to permit efficient grinding of their plant food and probably replaced their entire cheek dentitions while aestivating. The sympatric fabrosaurid ornithopods had a simple open‐and‐shut jaw action and replaced their teeth continuously in standard reptilian fashion. Seasonal dormancy must have imposed major constraints on the lives of fabrosaurids and heterodontosaurids. and these constraints are summarized in the model of a circannual lif

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01226.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Hohenegger. Johann 1978 07 15: Populationsgenetische Deutung des morphologischen Wandels der triassischen ForaminifereNodosaria striatoclavata. [A population genetic interpretation of the morphological transformation ofTriassic foraminiferNodosaria striatoclavata.]Lethaia, Vol. 11, pp. 199–215. Oslo. ISSN 0024–1164.In Middle Triassic (Ladinian) basin areas immediately adjacent to reefs,Nodosaria striatoeclavataSpandel exhibits during the early Ladinian a morphological transformation in the direction of the simultaneously occurringNodosaria liratellaTappan. Statistical confirmation of this trend is provided by such parameters as growth in test breadth and degree of bulging of the penultimate chamber. The ribbing, too, shows a directed change. There are three possible explanations for this morphological manifestation of a fusion of two species from a population genetic viewpoint: (1) Phyletic evolution ofNodosaria striatoclavatawith ‘convergence’ towardsNodosaria liratella. (2) Recurrent appearance of species which evolved rapidly from a single line of origin (‘punctuated equilibrium’). (3) Fusion of species through successive introgression of genes after the collapse o

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Brett, Carlton E. 197807 15: Host‐specific pit‐forming epizoans on Silurian crinoids.Lethaia, Vol. 11. pp. 217–232. Oslo. ISSN 0024–1164.Circular‐parabolic pits occur commonly on the endoskeletal remains of certain Paleozoic crinoids. Detailed study of several hundred specimens, representing about 30 pelmatozoan species from the Upper Silurian Rochester Shale of New York and Ontario, reveals that such pits occur exclusively in seven species of crinoids. Furthermore, there are consistent differences in the morphology and orientation of holes occurring on the different crinoid species. This suggests that distinct epizoan species settled selectively on given hosts. The relationship between the hole‐producing epizoans and crinoid hosts is inferred to have been a form of dependent commensalism. Preliminary surveys of other Paleozoic crinoid assemblages reveal similar host‐selectivity by pit‐producing epizoans. Crinoidepizoan pairs apparently co‐evolved through considerable spans of geologic time as related genera and species of different ages, from Silurian to Pennsylvanian, exh

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01229.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Kershaw, Stephen&Riding, Robert 1978 07 15: Parameterization of stromatoporoid shape.Lethaia, Vol. 11. pp. 233–242. Oslo. ISSN 0024–1164.Stromatoporoid cross‐sectional shape can be considered as a product of the interaction of three morphological variables: the relative proportions of basal, vertical and diagonal dimensions. The gross arrangement of internal lamination can be superimposed upon the resulting outlines. These shapes are taken to represent cross sections in any vertical plane through the centre of the coenosteum. This simple parameterization scheme is presented in triangular arrays which include the stromatoporoid morphotypes laminar, domical and bulbous, and varieties of them together with forms not utilized by stromatoporoids. Dendroid and irregular forms are too complex to be readily included in the scheme. Smooth and ragged varieties of laminar and domical forms are distinguished and related to sedimentation on the flanks of the coenosteum. Two types of mutual arrangement of latilaminae within the coenosteum are recognized: enveloping, where they completely overlap previous latilaminae, and non‐enveloping, where they do not. Laminar‐domical‐bulbous forms represent a series generated mainly by reduction of the basal dimension. They commonly exhibit enveloping latilaminae except in ragged varieties and some extended domes. Measurement of defined dimensions in the field allows stromatoporoid morphotypes to be plotted onto the triangular arrays and provides a rapid method of displaying the range of fo

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01230.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Fürsich. Franz Theodor 1978 07 IS: The influence of faunal condensation and mixing on the preservation of fossil benthic communities.Lethaia, Vol. 11, pp. 243–250. Oslo. ISSN 0024–1164.Condensation phenomena caused by environmental, biotic, or diagenetic factors are widespread in the fossil record, especially in shallow shelf sediments, and may alter the composition of ancient communities. Even without large‐scale transport being involved, often only time‐averaged seres will be available for palaeosynecological studies. This should be kept in mind when community analysis of such shell accumulations is a

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01231.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Harper, Charles W. Jr. 1978 07 15: Groupings by locality in community ecology and paleoecology: tests of significance.Lethaia, Vol. 11, pp. 251–257. Oslo. ISSN 0024–1164.Ecologic sample localities are commonly classified into groups on the basis of their species content; distinctive groups of localities are then commonly used to define discrete biofacies or communities. Yet, such locality groups and, by extension, the communities or biofacies inferred from them are almost never tested for statistical significance. Two approximate randomization tests are proposed as a step in this direction. One evaluates whether or not a given data set on which one or more locality groups are based exhibits adegree of clustering by localitythat is statistically significant. The second evaluates the statistical significance of thedegree of mappabilityexhibited by a given collection of inferred locality gro

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01232.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1978.tb01233.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY