摘要:

The relative abundance of suspension‐ and deposit‐feeding organisms in fossil communities has been used to interpret water turbulence in ancient environments. Trophic analysis of modern molluscan communities of San Francisco Bay and of Pliocene macroinvertebrate communities of the Kettleman Hills, California, suggests that the method is only partly valid for inshore environments, which may be more complex than those previously studied. Factors other than water turbulence must explain some differences in trophic proportions. Epifaunal communities consist largely of suspension‐feeding organisms regardless of other environmental factors, and relict sediments or sediments out of equilibrium with the normal hydrologic conditions in the area may lead to erroneous interpretations. Analysis of the total benthic macroinvertebrate communities of the southern California shelf indicates that the trophic proportions of the potentially fossilizable part of each community are not the same as the total community and is not always diagnostic of the enviro

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00971.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The macroinvertebrate fauna of the Corallian (Middle and Upper Oxfordian) often exhibits a clear relationship to ten types of substrates ranging from clays to oolites. Whereas diversity and abundance of infauna decreases with increasing grain size, abundance of epifauna increases. Suspension‐feeders dominate the ecological spectrum in all types of substrates, except for silts, where deposit‐feeders abound. These results have been compared to data from other horizons in the Jurassic and to observations in the Rec

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00972.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The first known sutural inversion in ammonoids occurred in the adolescent stage of a late CretaceousGlyptonoceras subcompressum(Forbes). Inversion has affected all folioles and lobules which are convex adapically instead of adorally, but not the tie‐points from which they are ‘suspended’ and which shape the principal saddle and lobes. The ventral median saddle is also normal due to its proximity to the siphuncle. The partially inverted sutures are also strongly approximated. This suggests that, in this instance, body advance was mainly by muscular pull against a negative pressure differential of cameral liquid to ‘ambient’ body pressure across the septal mantle, owing to insufficient liquid in the newly forming chamber. Conversely, a slightly positive pressure differential is inferred for normal ammonitic septum formation. In spite of reversal, the length of folioles and lobules remains constant, indicating the existence of a ‘permanent’ sinuous attachment band resembling the posterior aponeurosis ofNautilus, with tie‐points for primary

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00973.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

All enrolled Members of the International Palaeontological Association are now entitled to a free copy of the Third Edition. New Subscribing Members will receive the Directory as long as copies are left and are offered sets of back volumes ofLethaiaon very favourable conditions.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00974.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The spatangoidCyclaster danicushas been placed in the genusBrissopneustesby previous authors. The material from the Lower Danian of Denmark includes some abnormal individuals with depressed apical area. These have been previously interpreted as females with a marsupium. A study of both normal and abnormal tests indicates that the depressed apical area is not a marsupium but rather a malformation, possibly caused by adverse environmental conditions or by a parasite. The skeletal morphology indicates thatC. danicuswas a shallow burrowing form but the malformed individuals probably did not burrow.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00975.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00976.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The Stenolaemata comprise both basically single‐walled forms (Cyclostomata) and doublewalled forms (Trepostomata, Cystoporata and Cryptostomata) from their first appearance in the geological record. At the end of the Palaeozoic the main groups of apparently double‐walled stenolaemates died out, and only the single‐walled cyclostomates survived. During the Mesozoic, evolution within the Stenolaemata was apparently repeated by the further development of double‐walled forms such as cerioporids, lichenoporids and cancelloids, from single‐walled ancestors. These double‐walled groups are all remarkable homeomorphs of the major Palaeozoic groups of Bryozoa. A monophyletic origin of the post‐Palaeozoic Cyclostomata from Palaeozoic single‐walled forms is

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00977.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Acid‐resistant organic microfossils are described from outcrops and a boring through the middle and upper units of the VisingsÖ Beds in southern Sweden. 21 previously described acritarch species have been identified, and five new species are erected. The acritarchs include simple, although characteristically ornamented sphaeromorphs, one polygonomorph species and one acanthomorph species. Their mode of occurrence and possible lithofacial relationships are discussed. The acritarchs from the middle unit of the Visingso Beds indicate a Late Riphean age. The upper unit contains acritarchs previously known from Vendian and Lower Cambrian strata in the U.S.S.R., China and elsewhere. A Vendian age is suggested for this unit. A glacial origin is suggested for boulder beds in the middle unit of the VisingsÖ B

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00978.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Phosphatic conical microfossils from Upper Cambrian (Franconian) limestones of the Orr Formation in western Utah are described asUtahphospha sequinan.g., n.sp. The genus is also known from other localities in Utah and Nevada. The fossil has a distinct sequin‐like external sculpture which has been formed by outward accretion. A hole at the tip originated by abrasion from within. The fossils are interpreted as hatched cysts of an unknown organis

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00979.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Janospirais described from early Ordovician (Arenig) rocks of northern Spitsbergen. It is a curious microfossil, probably calcareous, about 1 mm in length, made up of an initial coil which expands distally into a straight tube, at the same time as producing a narrower tube almost in line with the first but in the opposite direction. Although showing some similarities to Foraminifera, molluscs and polychaetes, there are objections to its inclusion in any of these groups, and it is equally probable that it belongs to an unknown group with a planktic early growth stage.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1976.tb00980.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY