摘要:

Seilacher, Adolf 1989 07 15: Vendozoa: Organismic construction in the Proterozoic biosphere.Lethaia, Vol. 22. pp. 229–239. Oslo. ISSN 0024–1164.Ediacara‐type impressions of large, but flat and soft‐bodied organisms in Late Proterozoic rocks are here interpreted not as ancestors of modern animal phyla, but as foliate pneu constructions, whose quilting patterns had to be accommodated with various modes of growth. In this view Vendozoa represent an evolutionary experiment that failed with the coming of macropbagous predators. True Metazoa are also represented, but in the form of trace fossils rather than body impressions. *Precambrian fossils, evolution, constructional mor

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01332.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Baker, Peter G. 1989 07 15: Location and interpretation of ontogenetic relics in the shell of adult brachiopods.Lethaia, Vol. 22. pp. 241–245. Oslo. ISSN 0024–1164.Careful sectioning of critically orientated adultOrnithella bathonica(Rollier) shells has revealed, close to the umbo in the secondary fibrous shell layer of the brachial valve, relics of early ontogenetic structures which can be directly correlated with those of early juveniles ofZeilleria leckenbyi(Davidson ex Walker MS). It is now confirmed that very early in ontogeny, the brachial valve ofO. bathonicapossessed a septal pillar identical with that found in Z.leckenbyiand many terebratellacean species. *Brachiopoda. Terebratellidina, Ornithellidae, ontogenetic relics, buried microstruct

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01333.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01334.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:Lower Turonian inoceramid bivalves are described from the Sergipe Basin in northeastern Brazil, and a palaeoecological analysis of the region is attempted. The principal locality, Retiro 26, comprises a sequence of 35 m of the Cotinguiba Limestone Formation. Various unconformities occur in the sequence. The formation is inferred to have been deposited in an outer shelf environment of a subtropical shallow sea, with oscillating water depth, occasional strong bottom currents and ephemeral reductions of the oxygen level. The inoceramids show some endemism. Two inoceramid associations are recognized: theMytiloides mytiloidesand theMytiloides hercynicusassociations. Four new species of divergently ornamented inoceramids are described and referred to the new genusRhyssomytiloides. Two new species ofSergipiaand some previously known species ofMytiloidesandRhyssomytiloidesare also described.

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01336.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Brunton, C. Howard C.&Alvarez, Fernando 1989 07 15: The relationship between major lamellae and epithelial regressions in some articulate brachiopods.Lethaia, Vol. 22, pp. 247–250. Oslo. ISSN 0024–1164.Hiller (1988,Lethaia, Vol. 212) proposed three relationships between the secretory epithelium of articulate brachiopods and the shell surface ornamentations of growth lines, lamellae and spines. None of his models satisfy the growth of strongly lamellose athyrid shells and we propose a fourth involving strong regressions effecting both primary and secondary shell layers. In RecentTegulorhynchiawe suggest a growth function for the ‘frayed’ shell of Hiller occurring immediately in front of the

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01337.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Erwin, Douglas H. 1989 07 15: Molecular clocks, molecular phylogenies and the origin of phyla.Lethaia, Vol. 22, pp. 251–257. Oslo. ISSN 0024–1164.Protein, RNA and DNA sequences have been widely used to construct phylogenies and to calculate divergence times using a molecular clock. Reliance on molecular information is particularly attractive when fossil evidence is missing or equivocal, as in the Cambrian metazoan radiation. I consider the applicability of molecular clocks and phylogenetic analysis of molecular data to the origin of metazoan phyla, and conclude that molecular information is often ambiguous or misleading. Amino acid sequences are of limited use because the redundancy of the genetic code masks patterns of descent, while in a nucleotide sequence only four potential states exist at each site (the four nucleotide bases). In each case, homoplasy may often go undetected. The application of a molecular clock to resolve the timing of the metazoan radiation is unwarranted, while molecular phylogenetic reconstruction should be approached with care. A potentially more useful technique for phylogenetic reconstruction would be the use of patterns of genome structure and organization as characters. *Molecular clock, phylogenetics, metazoan radiation, origin of ph

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01338.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Klaus J. Müller&Dieter Walossek: External morphology and larval development of the Upper Cambrian maxillopodBredocaris admirabilisAbstract: Search for new material yielded more than ninety specimens of different growth stages ofBredocaris admirabilisMüller, 1983. It enables us to present an extended description of the largest stage, considered as adult, and of the larval sequence. Discovery of the tagma boundary of the cephalon behind the fifth pair of appendages led to the identification of the second maxilla, which has the same design as the thoracopods and is incorporated within the trunk limb series. The larval sequence comprises five successive metanaupliar instars, with delay of development of post‐maxillulary limbs. Stages between larvae and the presumed adult have not been found.Bredocaris, about 0.85 mm long as adult, is assumed to have lived epihenthically, swimming closely above a flocculent bottom layer. Lack of special feeding structures on the trunk limbs and retention of the larval cephalic feeding apparatus in the adult suggest rather simple nutritory habits; filter feeding can be ruled out. The morphology, in particular the possession of seven pairs of thoracopods, and ontogeny indicate a systematic position ofBredocariswithin the Maxillopoda and close alliance to the shield‐bearing members of this subclass, the Thecostraca. Differences betweenBredocarisand all known maxillopodan taxa are the basis for proposing the new order Orstenocarida and new family Bredocarididae. The major diagnostic characters of this new order include: a simple. posteriorly indented head shield, probably compound eyes, anterior three‐head appendages of naupliar shape, a 1st maxilla with rudimentary exopod and specialized for trophic function, a 2nd maxilla of trunk‐limb shape, a thorax composed of seven segments, each with a pair of biramous paddle‐shaped thoracopods, and a uniform abdomen carrying inarticulate, unsegmented

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01339.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

BergstrÖm, Jan 1989 07 15: The origin of animal phyla and the new phylum Procoelomata.Lethaia, Vol. 22, pp. 259–269. Oslo. ISSN 0024–1164.A model of metazoan evolution presented previously (BergstrÖm 1986 inZoologica Scripta 15) explains deuterostomian characters as derived from protostomian ones through loosening of the constraints in the spiralian type of morphogenesis. This fits phylogenies derived from studies of molecular sequences. The model helps explain (1) the well‐known mixture of proto‐ and deuterostomian features in several groups; (2) the difficulties in making a phylogeny based on comparative anatomy, and (3) the fossil explosion in the Cambrian. Since protostomian features such as a ciliated locomotory sole and a pelagic larva with ciliary bands are widely distributed in branches of the phylogenetic tree, they must have been present in the stem of the tree. Most probably the stem forms were pseudosegmented, which helps explain how segmentation, oligomery and non‐segmentation could evolve repeatedly in derived groups. Origination of new phyla involved macroevolutionary changes primarily in the mode of feeding and locomotion. The stem phylum, from which most other phyla appear to have been derived directly, is here named the Procoelomata. Machaeridian‐type animals are referred to it. The Ediacaran‐type Precambrian fossils Cannot be placed in the metazoan evolutionary tree. *Biochemical evolution, Cambrian fossil explosion, Deuterostomia, eukaryote evolution, Machaeridia. macroevolution, Precambrian fossils. Procoeloma

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01340.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The Meishucunian Stage of south China provides a window on the radiation of skeleton‐bearing metazoans at the beginning of the Cambrian. The section at Meishucun has been proposed as a candidate for a global stratotype of the Precambrian‐Cambrian boundary.Fossils and StrataNo. 24, by Qian Yi&Stefan Bengtson, presents a thorough reinvestigation of the bizarre Meishucunian biota on the basis of exquisitely preserved material. This monograph will become a central reference on the earliest Cambrian faunas and the problem of the Precambrian‐Cambrian boundary.Qian Yi&Stefan Bengtson: Palaeontology and biostratigraphy of the early Cambrian Meishucunian Stage in Yunnan Province, south ChinaAbstract: The skeletal fossils of the early Cambrian Meishucunian Stage from two key localities (Meishucun, Jinning County, and Xianfeng, Xundian County) in eastern Yunnan Province, China, are described and illustrated in detail to provide a basis for improved palaeobiological and biostratigraphical work. About 1250 new SEM illustrations (including a large number of stereo‐pairs) of well preserved material are presented. The taxonomy is extensively revised. When biological and preservational variability are taken into account, the number of genera and species may be reduced through synonymy to about one third of that reported in the literature. Thirty‐eight genera (2 of which are new) and 57 species (5 of which are new) are described. The biology and affinities of many of these taxa are also discussed, but excursions into supra‐generic taxonomy are generally restrained. The Meishucunian biotas of Yunnan consist of three successive assemblages with very few taxa in common. The first, theAnabarites‐Protohertzina‐ArthrochitesAssemblage, is dominated byAnabaritesand other sedentary tube‐dwelling organisms, but non‐sedentary benthic mollusc‐like fossils (Canopoconus) and probable predators (Protohertzina) also occur. The key elements of this fauna have a wide geographical distribution and may be compared with the earliest skeletal faunas on the Siberian Platform, the Canadian Cordillera, and other regions. The second, theSiphogonuchites‐ParagloborilusAssemblage, is characterized by a great diversity of vagile mollusc‐like and multisclerite‐bearing animals, but also sedentary tube‐dwellers and some possible predators (CyrtochitesandYunnan‐odus) occur. This fauna is largely endemic. The third. theLapworthella‐Tannuolina‐SinosachitesAssemblage, is mainly characterized by widely distributed taxa of multisclerite‐bearing animals (chancelloriids,Halkieria, Tannuolina, andLap worthella). It has elements in common with late Atdabanian

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01341.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Martin, Jose M., Braga, Juan C.&Rivas, Pascual 1989 07 15: Coral successions in Upper Tortonian reefs in SE Spain.Lethaia, Vol. 22, pp. 271–286. oslo. ISSN 0024–1164,During the Upper Tortonian (Upper Miocene), the Almanzora river corridor, a small Neogene basin in SE Spain, harboured coral reefs growing in three different environments: in fan deltas, beyond the influence of coarse terrigenous sedimentation; in the abandoned lobes of a delta complex; and on coastal margins. All of these reefs are composed of several successive beds, each of which may be made up mainly ofPoritesembedded in silt or of an initialPoriteslevel followed by a silt‐freeTarbellastraealevel on top.Poritesmay be associated with corallines. This structure is interpreted as being the result of an ecological succession repeated over and over again. A pioneer association consisting mainly ofPorites. by colonizing the substrate and continuing to grow through relatively adverse silt‐deposition conditions, prepares the ground forTarbellastraeato take over. A return to the previous conditions halts the growth of theTarbellastraeacolonies and thePoritesassociation once more establishes itself in the silt, or else the renewed rate of deposition is sufficiently heavy to suffocate the whole bioconstruction.*Ecological succession. coral reefs, Tortonian, southeas

ISSN:0024-1164    

DOI:10.1111/j.1502-3931.1989.tb01342.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY