FOSSILS AND STRATA Shards of the Cambrian explosion

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 Strata No. 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 China Abstract: 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, the Anabarites-Protohertzina-Arthrochites Assemblage, is dominated by Anabarites and 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, the Siphogonuchites-Paragloborilus Assemblage, is characterized by a great diversity of vagile mollusc-like and multisclerite-bearing animals, but also sedentary tube-dwellers and some possible predators (Cyrtochites and Yunnan-odus) occur. This fauna is largely endemic. The third. the Lapworthella-Tannuolina-Sinosachites Assemblage, is mainly characterized by widely distributed taxa of multisclerite-bearing animals (chancelloriids, Halkieria, Tannuolina, and Lap worthella). It has elements in common with late Atdabanian faunas in other regions of the world.     

FOSSILS AND STRATA Two new numbers on conodonts

Numbers 15 and 16 of Fossils and Strata have now been published. Both numbers deal with conodonts. Number 15 contains the proceedings of the Third European Conodont Symposium (ECOS 111), held in Lund, Sweden, 30th August to 1st September, 1982. Number 16 is Svend Stouge's monograph on the conodonts of the Middle Ordovician Table Head Formation of western Newfoundland. Both may be ordered from Universitetsforlaget, Postboks 2959, Tφyen, Oslo 6, Norway, at the prices quoted below (exclusive of postage and handling).     

Trace fossils of Cambrian aglaspidid arthropods

A new trace fossil, Raaschichnus gundersoni , from the Upper Cambrian St. Lawrence Formation of Wisconsin, was produced by an aglaspidid arthropod. The rusophyciform trace, which occurs singly and in series, is distinctive in showing marks left by the tail-spine. Other trace fossils previously considered to have been made by aglaspidids were probably excavated by animals lacking a tail-spine and with appendage morphologies very different from the aglaspidids of Wisconsin.     

贵州威宁及邻近地区新生界中再沉积有孔虫

８０年代,当时的一些主要报纸和有关杂志相继报道过贵州威宁及其邻近地区上第三系中曾发现一批海相有孔虫化石,由此推断云贵高原曾受到晚第三纪的海侵。经过笔者鉴定,这批有孔虫为再沉积的石炭纪标本,其中不仅有非Ｔｉｎｇ小有孔虫,还有Ｔｉｎｇ类,从Ｔ类化石分析,其时代无疑为早石灰世,从而匡正了对云贵高原新生代地质历史的认识。     

AMNIOTE PHYLOGENY AND THE IMPORTANCE OF FOSSILS

Abstract— Several prominent cladists have questioned the importance of fossils in phylogenctic inference, and it is becoming increasingly popular to simply fit extinct forms, if they are considered at all, to a cladogram of Recent taxa. Gardiner's (1982) and Løvtrup's (1985) study of amniote phylogeny exemplifies this differential treatment, and we focused on that group of organisms to test the proposition that fossils cannot overturn a theory of relationships based only on the Recent biota. Our parsimony analysis of amniote phylogeny, special knowledge contributed by fossils being scrupulously avoided, led to the following best fitting classification, which is similar to the novel hypothesis Gardiner published: (lepidosaurs (turtles (mammals (birds, crocodiles)))). However, adding fossils resulted in a markedly different most parsimonious cladogram of the extant taxa: (mammals (turtles (lepidosaurs (birds, crocodiles)))). That classification is like the traditional hypothesis, and it provides a better fit to the stratigraphic record. To isolate the extinct taxa responsible for the latter classification, the data were successively partitioned with each phylogenetic analysis, and we concluded that: (1) the ingroup, not the outgroup, fossils were important; (2) synapsid, not reptile, fossils were pivotal; (3) certain synapsid fossils, not the earliest or latest, were responsible. The critical nature of the synapsid fossils seemed to lie in the particular combination of primitive and derived character slates they exhibited. Classifying those fossils, along with mammals, as the sister group to the lineage consisting of birds and crocodiles resulted in a relatively poor fit to data; one involving a 2—4 fold increase in evolutionary reversals! Thus, the importance of the critical fossils, collectively or individually, seems to reside in their relative primitive-ness, and the simplest explanation for their more conservative nature is that they have had less time to evolve. While fossils may be important in phylogenetic inference only under certain conditions, there is no compelling reason to prejudge their contribution. We urge systematists to evaluate fairly all of the available evidence.     

Chin surgery III: revelations

This article is a logical extension of previous articles written on the topic of aesthetic chin surgery. In it, the authors expand on previously published surgical techniques and provide specific updates to increase success in some unusual situations. They review the indications for and uses of reduced-height implants, discuss the validity of centralized chin incisions in both reconstruction and revisions, show the diversity of mentalis muscle anatomy and chin pad variations, reveal the importance of the lip-to-labiomental crease inclination in cases of macrogenia, note a key update on reefing the mentalis muscle to a higher position for permanent sulcus position, discuss the issues of lower lip position and lower incisor show, and expound on the horizontal smile/chin ptosis phenomenon.     

TRACE FOSSILS FROM THE PRECAMBRIAN AND BASAL CAMBRIAN

Certain worm-like configurations on rocks are recognized as shrinkage-crack infillings. Some genuine Precambrian trace fossils are briefly described. The early Cambrian contains a richer assemblage, including some distinctive and widespread form genera. The study of early trace fossils leads to conclusions not only on facies, but also on the evolution of behaviour and functional morphology in soft-bodied organisms.     

论中国早寒武世原牙形类和牙形状化石——分类评述和地层意义

原牙形类和牙形状化石是早寒武世微小骨骼化石中非常特征的一个类群。自二十世纪70年代以来,这些齿状的微型磷质骨片化石在中国下寒武统含小壳化石地层中被大量发现,据统计已描述有25属52种。通过文中的评述和讨论,证实其中的一些属种是次异名或属于无效的分类名称,还有一些在归属上尚存在疑问。通过对原牙形类和牙形状化石定义的讨论,将先前指定为原牙形类的13个属进行了分类评述。表明其中的5个属是次异名,还有2个属是未知的节肢动物。其它的12个牙形状化石属中也有5个属是次异名,它们不仅显示了有多种动物亲缘的牙形状形态,而且大多属于绝灭生物,只有Beshtashella和Paraformitchella(=Beshtashella)被指定为软体动物。文中还简要地讨论了大多数属的时空分布,包括3个阶段的原牙形类地层分布,这不仅具有划分对比地层的意义,而且还反映了原牙形类的演化趋势。     

STRESS, EXTINCTIONS AND EVOLUTIONARY CHANGE: FROM LIVING ORGANISMS TO FOSSILS

1. Natural populations are exposed to environmental stress of varying intensities. This provides a reference point for extrapolations from the living biota to fossils and vice versa. 2. Evolutionary change is likely when there are resources in excess of maintenance and survival needs. It is largely precluded at species borders by the metabolic costs of stress; from this follows climatic tracking by species. 3. A relatively small increase in abiotic stress could underlie extinctions of stress-sensitive endemic species and the spread of stress-resistant generalist and widespread species. Widespread fossil species appear resistant to extinction under the stress level of normal background extinctions. 4. Synergistic interactions among generalized stresses should increase the likelihood of extinctions, especially for stresses with energetic consequences. 5. Some marine organisms survived the K-T mass extinction event because of stress-evasion mechanisms such as stress-resistant life-cycle stages with low metabolic rates. 6. In moderately stressed and narrowly fluctuating environments, sufficient genetic variability and metabolic energy should be available to permit adaptation. In these environments phyletic gradualism is expected. 7. In highly stressed and widely fluctuating environments, a punctuated evolutionary pattern is expected whereby stasis occurs most of the time. 8. Evolutionary patterns therefore can vary depending on the details of the interaction between stress, environmental fluctuations, energy availability and genetic variability. 9. Little evolutionary change is expected when the availability of energy is severely restricted. Examples include cave animals in stable but stressed environments and ‘living fossils’ in widely fluctuating but stressed environments. 10. Since the primary effect of abiotic stress may be at the level of energy carriers, a reductionist approach permits generalisations in considering extinctions and conditions under which diversification is likely.     

内蒙古地区中新世木化石及古气候意义

木化石采自内蒙古赤峰平庄煤矿。矿区内展布的地层有两套,下部为晚中生代含煤地层,上部为第三系。木化石打自上部第三系,同层具有丰富的叶部化石。现报道的木材化石共３种,平庄原始黄杉型木Ｐｓｅｕｄｏｔｓｕｇａｘｙｌｏｎ ｐｉｎｇｚｈａｎｇｅｎｓｉｓ ｓｐ．ｎｏｖ．,东北云杉木Ｐｉｃｅａｘｙｌｏｎ ｍａｎｃｈｕｒｉｃｕｍ Ｓｚｅ和松型木Ｐｉｎｕｘｙｌｏｎ ｓｐ．等。其中的原始黄杉型木的最近亲缘属黄杉属。就生     

Chloroplast signaling: retrograde regulation revelations

Developing chloroplasts are able to communicate their status to the nucleus and regulate expression of genes whose products are needed for photosynthesis. Heme is revealed to be a signaling molecule for this retrograde communication.     

QUATERNARY STRATIGRAPHY AND MAMMAL FOSSILS OF YIHE AND SHUHE RIVER DRAINAGES

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