摘要:

The cyclocrinitids are an extinct tribe of dasycladacean green algae. They were anatomically very similar to certain Recent dasyclads, even at early growth stages. The morphology and preservation of cyclocrinitids strongly suggest that they had a siphonous cellular organization with extracellular, aragonitic calcification; these features are characteristic of living dasyclads. The light surficial calcification of cyclocrinitids and other dasyclads had important paleoecological effects. It restricted them to low‐energy waters, as it provided relatively little structural support. It also confined them to warm, tropical waters; they are good paleoequatorial indicators. The decline of these algae during the late Ordovician and early Silurian may therefore reflect the simultaneous cooling and glaciation. Receptaculitids are entirely unrelated organisms. Their meroms have several distinctive features; they are not homologous to the lateral branches of cyclocrinitids or dasyclads. Receptaculitid calcification was extensive and their thalli were apparently quite sturdy; they often occurred in reefs. Receptaculitids also lived in high‐latitude, cold‐water environments. Thus, they were ecologically unlike any calcareous green algae, and cannot be used as paleoequatorial indicators. Receptaculitids remain problematical, although the arrangement of meroms suggests plant affinities. □Calcareous algae, Problematica, Dasycladales, Cyclocriniteae, Receptaculitales, morphology, classification, paleoecology, paleoge

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01745.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Functional hypotheses for fossil organisms can be rigorously tested through the application of engineering principles and physical laws (paleobiomechanics). Alternative functional models for the telson (tail spine) of the large pterygotid eurypterids are examined in terms of the hydrodynamics of fish propulsion and of ship rudders. The telson probably served as a rudder for steering in the horizontal and vertical planes during swimming, rather than as a thrust producer. The aspect ratio of the telson may approach an ‘optimum’, for the production of rudder forces over a wide range of angles of attack. Pterygotids may have been highly agile, rather than rapidly swimming animals.Eurypterids, functional morphology, paleobiomechan

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01746.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01747.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01748.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

CassubiaLendzion 1977 andLiwianew name (forLiviaLendzion 1975 preoccupied) found in the subsurface Zawiszany formation of the basal Cambrian in NE Poland are identified as an anomalocarid and a ‘soft‐bodied’ trilobite, respectively, each being the oldest representative of its group. The presence of four free thoracic tergites inLiwia, the relatively strong sclerotization, and the apparent segmentation of the pygidial shield (expressed in the metameric distribution of marginal spines) indicate that the ‘soft‐bodied’ trilobites achieved their organization by secondary softening of the dorsal exoskeleton and suppression of the development of thoracic tergites

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01749.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01750.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A new graptolite species,Monoclimacis praemicropoma, from the Upper Wenlock of Poland is described. It is an ancestor of the Lower LudlowM. micropoma(Jaeckel). The phytogeny of thepraemicropoma‐micropomalineage is discussed.M. micropoma nannopoma(Jaeger) has been assigned to a separate evolutionary lineage.Graptolites, Wenlock, phytogen

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01751.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Three new genera of acrotretid brachiopods are of general morphological interest in that they display polygonal mosaics on the internal shell surfaces, features which are believed to be moulds of the outer epithelial cells. The mosaic is further noted in a specimen ofEoconulus, a form which may also belong to the Acrotretacea. Such mosaics have not previously been recorded from the Acrotretacea.Polygonal mosaics, epithelial moulds, outer epithelium, Eoconulus,Acrotretacea, Ordovician.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01752.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A carbonate buildup dominated by trepostome Bryozoa is described from Dinantian (Asbian) strata near Llandudno in North Wales. A three‐phase ecological succession is recognised within the buildup: (i) a basal diverse community with fenestrate, ramose, encrusting trepostome and cystoporate bryozoans in a mud rich wackestone; (ii) a bulk facies, dominated by encrusting and foliaceous, trepostome bryozoans in a fine packstone, and (iii) a thin capping phase, dominated by unilaminar, encrusting trepostome bryozoans in a slightly coarser lithology, including skeletal debris derived from the mound top and possible flanking beds. The buildup probably had topographic relief and developed in a shallow marine environment. The internal tripartite zonation reflects the growth of the structure into a shallower, higher energy regime, with the capping beds being deposited just below wave base. The buildup developed to the north of St. George's Land, on a carbonate shelf edge bordering the deeper basinal facies of the Irish Sea Basin.Dinantian, Asbian, buildup, trepostome Bryozoa, Foraminifera, corals, calcareous algae, Carboniferous, North Wale

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01753.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A. Hoffman&M. H. Nitecki (eds.) 1987:Problematic Fossil Taxa. Oxford Monographs on Geology and Geophysics no. 5.267 pp. Oxford University Press. ISBN 0–19–503992–0. Price £60 (

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1988.tb01754.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY