The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods

Lin, J.‐P., Ivantsov, A.Y. & Briggs, D.E.G. 2011: The cuticle of the enigmatic arthropod Phytophilaspis and biomineralization in Cambrian arthropods. Lethaia, Vol. 44, pp. 344–349. Many non‐trilobite arthropods occur in Cambrian Burgess Shale‐type (BST) biotas, but most of these are preserved in fine‐grained siliciclastics. Only one important occurrence of Cambrian non‐trilobite arthropods, the Sinsk biota (lower Sinsk Formation, Botomian) from the Siberian Platform, has been discovered in carbonates. The chemical compositions of samples of the enigmatic arthropod Phytophilaspis pergamena Ivantsov, 1999 and the co‐occurring trilobite Jakutus primigenius Ivantsov in Ponomarenko, 2005 from this deposit were analysed. The cuticle of P. pergamena is composed of mainly calcium phosphate and differs from the cuticle of J. primigenius, which contains only calcium carbonate. Phosphatized cuticles are rare among large Cambrian arthropods, except for aglaspidids and a few trilobites. Based on recent phylogenetic studies, phosphatization of arthropod cuticle is likely to have evolved several times. □arthropod cuticle, Burgess Shale‐type preservation, fossil‐diagenesis, phosphatization.     

Cambrian biostratigraphy of the Bowers back-arc basin,Northern Victoria Land,Antarctica — A review

The Bowers Mountains in Northern Victoria Land contain the richest Cambrian Series 3 (Miaolingian, middle Cambrian) and Cambrian Series 4 (Furongian, late Cambrian) fossiliferous successions in Antarctica. Almost all the fossils are found within the Bowers Supergroup, which outcrops within the Bowers Terrane, a fault-bounded northwest-southeast oriented strip in Northern Victoria Land. The fossils provide the main age control on the history and evolution of the Bowers volcanic arc and back-arc basin. The great bulk of the fossils occur within the Spurs Formation. The fossil assemblages are dominated by agnostoids and polymerid trilobites with most ranging in age from Drumian to Paibian, although one fauna is of Jiangshanian age. Over 40 agnostoid taxa and over 100 polymerid trilobite taxa have been recorded from the rocks of the Bowers Supergroup. The youngest fauna occurs within the adjacent Robertson Bay Terrane, where a limited fauna of polymerid trilobites and conodonts from within a limestone olistolith have a very late Cambrian or early Ordovician age. Faunal affinities are mainly with Australia, New Zealand, North and South China and the Himalaya with lesser ties to Iran, Kazakhstan, Siberia and Laurentia.     

Trilobites from the lower and lowermost middle Cambrian of the Kiya River reference section (Kuznetsk Alatau)

The Kiya River reference section is characterized by trilohites confined to units X–XV of the Lower Cambrian Usa Formation and to the base of the lowermost Middle Cambrian Berikul Formation. Trilobites are represented by 130 species assigned to 77 genera. The given paper describes 38 species belonging to 27 genera. 16 species, 2 genera and one subfamily are new. All of them occur in the Usa Formation and in the Lower Cambrian pebbles of the Berikul Formation. Biostratigraphic analysis shows that the trilobite fauna contains characteristic trilobite assemblage elements of the Lower Cambrian regional stages in the Altay-Sayan Fold Belt, i.e. the Kiya and Kameshki regional stages (Atdabanian Stage), the Sanashtykgol regional stage (Botomian Stage), the Obruchev regional stage (Toyonian Stage). Table I shows trilobite species composition and vertical distribution in the reference section.     

Reassessment of the mode of life of Pagetia Walcott, 1916 (Trilobita: Eodiscidae) based on a cluster of intact exuviae from the Kaili Formation (Cambrian) of Guizhou, China

Pagetia is the most abundant trilobite in the Kaili Formation (lower to middle Cambrian). During the course of studying the museum collections of Kaili trilobites ( n  > 1000), a cluster containing 22 pagetiid individuals at various growth stages is noted. Specimens record the growth range from the degree 0 meraspid to late holaspid phases. Based on the relative completeness of the moults except for missing free cheeks, these specimens are interpreted as intact exuviae that had undergone minimal transport prior to burial. If Kaili pagetiids had pelagic or planktonic living habits as previously suggested, it would be difficult to explain the presence of intact exuviae in clusters. Therefore, Kaili pagetiids are interpreted here as having a benthic mode of life after the onset of the meraspid phase.     

贵州台江下-中寒武统凯里组遗迹化石群落与环境关系的探讨

通过贵州台江凯里组中丰富的、分异度较高的、以原地埋藏为特征的遗迹化石的研究,探讨凯里组遗迹化石群落的沉积环境和埋藏环境。凯里组遗迹化石群落以节肢动物和软体动物的停息迹、爬行迹和游泳迹占优势,浅层内生爬行觅食潜穴和系统觅食潜穴占有一定的地位,也见有浅的居住滤食性潜穴,属Seilacher的Cruziana遗迹相,为正常浪基面和风暴浪基面之间的浅海软质基底陆棚低能环境,那里盐度正常、光照充足、含氧量充分、水体平静、沉积速率较快。在此环境中,浮游、游泳以及底栖爬行和固着生物类型大量地生长、繁殖和活动,表生遗迹和浅层内生遗迹十分丰富。生物死亡后的腐烂和分解,使得食泥生物大量繁盛。随着沉积物的覆盖和被埋藏生物遗体的分解、腐烂,沉积物内部还原能力逐渐增强,导致分解和腐烂过程终止。     

湘西晚寒武世多节类三叶虫新种及Erixanium属首次发现

文中描记 3个多节类三叶虫新种 :Hardyoidesdamaensissp .nov .,Meringaspisdamaensissp .nov .,andRhyssometopus (Rostrifinis)nitidussp .nov .,均产自湘西凤凰花桥组中部。同时描记首次在江南斜坡带中发现的Erixanium一属的保留命名种Erixaniumcf.E .sentum。Erixanium是全球性分布的多节类三叶虫 。     

Proposed GSSP for the base of Cambrian Stage 7, coinciding with the first appearance of Lejopyge laevigata, Hunan, China

The Luoyixi section, exposed in a roadcut along the Youshui River (Fengtan Reservoir), Guzhang County, Hunan Province, China, is proposed as the stratotype for the base of an unnamed stage boundary (base of the Cambrian stage provisionally termed Stage 7). The proposed position of the GSSP is 121.3 m above the base of the Huaqiao Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge laevigata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only with the primary stratigraphic marker (L. laevigata) but also with secondary biostratigraphic, sequence-stratigraphic, and chemostratigraphic correlation tools. The first appearance of L. laevigata is one of the most readily recognizable levels in the Cambrian, and can be correlated with precision to all paleocontinents.     

寒武纪早期澄江生物群中受创伤的中间型始莱德利基三叶虫(Eoredlichia intermedia)

三叶虫是寒武纪海洋中的常见动物,其受伤愈合现象的化石记录可以反映生态系统内物种之间竞争关系。中国华南寒武纪早期澄江化石生物群因保存软躯体构造化石而成为研究寒武纪大爆发时期古海洋生态群落的绝佳窗口,然而,澄江生物群中三叶虫受伤愈合现象的化石至今未见报道。中间型始莱德利基虫(Eoredlichia intermedia Lu,1940)是澄江生物群的常见物种,也是我国寒武系第二个三叶虫化石带的标准带化石。在2 000余枚中间型始莱德利基虫标本中,发现两枚成体标本的头甲侧边缘、颊刺和胸甲肋节保存了不同程度的残缺。据此推测,Eoredlichia intermedia在生命活动过程中曾受到碎壳型捕食动物的攻击或其他伤害而形成伤口。伤口部位边缘加厚且光滑,显示了明显的愈合痕迹。这些特征表明始莱德利基虫在受到非致死的伤害后,具备自身修复损伤的能力。这是迄今所知最为古老的,也是在澄江生物群中首次发现的三叶虫受伤并且愈合的标本,反映了寒武纪第二世第三期底栖生态系统中碎壳型捕食者和三叶虫猎物之间的军备竞赛生态关系。     

安徽淮南寒武纪一新三叶虫属——Huaiaspis

安徽淮南八公山地区寒武纪毛庄-徐庄期地层出露良好,化石丰富。在老鹰山剖面徐庄组底部的紫色页岩内所采集大量三叶虫标本中发现的一种新的三叶虫,命名为Huaiaspishuainanensisgen.etsp.nov.,它代表了一个尚未描记的且科级分类位置待定的新属新种。该三叶虫特点突出,是头部特征极度消隐且不具眼、眼叶、眼脊的“盲三叶虫”。该三叶虫为小尾型后颊类,主要特征为:壳面光滑,背壳呈次椭圆形,头盖半圆形;头鞍呈钟形向前收缩;背沟浅,仅在侧光下可见;活动颊平滑宽大,具有宽阔的活动颊刺;胸部由14节组成;尾部中轴粗壮,无边缘沟。     

山东寒武系苗岭统三叶虫消化系统的化石证据

三叶虫是寒武纪演化动物群中最引人注目的成员之一,其内部解剖结构一直以来受到广泛关注.与其他非生物矿化软体结构相比,三叶虫的消化系统更容易留下化石记录,为探索其内部结构提供了难得的机会.本文描述了来自山东省潍坊市寒武系馒头组的Proasaphiscus,Lioparia,Deiradonyx和Iranoleesia,以及...     

Taphonomic versus ecologic controls on taxonomic relative abundance patterns in tempestites

Evaluation of taphonomic sample bias in tempestites is an important prerequisite for paleoecologic analysis in storm-dominated shelf settings. Data from tempestites in the Upper Cambrian Bison Creek Formation of southern Alberta indicate that size, sorting greatly influences trilobite relative abundance patterns. Shifts in relative abundances of taxa both within and between beds are matched by changes in trilobite size. That is, collections fall into two intergrading types of assemblage which are dominated by taxa which reach large and small adult sizes, respectively. These shifts in dominance are interpreted as taphonomic variability within a single trilobite biofacies. Biofacies differentiation is expressed as abrupt changes in relative abundance patterns that are independent of trilobite size. Qualitative general models for size-sorting in tempestites are developed. Size-sorting in graded tempestites produces vertical shifts in relative abundances of taxa that mimic those expected in short-term autogenic ecologic succession. Size-sorting between beds in a single section could lead to an overestimation of the number of biofacies present. Size-sorting between proximal and distal portions of a depth gradient might generate abundance patterns that mimic those expected for 'depth-related communities', even in the complete absence of any underlying ecologic differentiation. The models represent taphonomic null hypotheses which must be rejected prior to making paleoecologic inferences in storm-dominated shelf environments. 0 Taphonomy, tempestites, Trilobita, Upper Cambrian, paleoecology.     

湖北秭归茅坪镇下茶庄剖面石牌动物群初探*

报道湖北秭归长江以南茅坪镇下茶庄剖面发现的寒武系下部(第2统第4阶)石牌动物群。该剖面石牌组出露良好,顶底界线清楚,总厚度208m。初步采集结果表明该剖面具有较大的开采潜力,化石数量上以腕足动物和软舌螺为主,同时还包括数量较多的三叶虫、双瓣壳节肢动物、开腔骨类和少量的鳃曳动物等,其中的腕足动物保存良好,数量丰度较大,壳体多以密集立体保存的内模形式出现,这是石牌组腕足动物大量壳体化石的首次报道。化石采集发现鳃曳动物与腕足动物可在相同的层面同时出现。与澄江动物群鳃曳动物化石相比,下茶庄剖面鳃曳动物的环纹保存的立体程度明显较强,但还未见到任何吻部和肠道结构保存。石牌动物群最早发现于长江以北宜昌三峡人家旅游风景名胜区内的王家坪剖面,但该地区石牌组覆盖严重,顶底未见出露,使王家坪剖面石牌动物群的后续研究存在较大困难。因此,石牌动物群在下茶庄剖面的发现和进一步采集和研究对深入揭示石牌动物群的组成、富集层位、群落结构和地理分布范围有重要的意义。     

Lower Cambrian trace fossil evidence for predation on trilobites

Predation upon trilobites previously has been inferred from large coprolites containing trilobite fragments, and from specimens of trilobites with healed wounds. The discovery of large burrows ( Dolopichnus gulosus , n. ichnogen., n. ichnosp.) in micritic quartz arenite of the Lower Cambrian Poleta Formation in Esmeralda County, Nevada, suggests that sea anemones preyed upon trilobites. Dolopichnus n. ichnogen., vertical cylindrical burrows with a central cylindrical core, is interpreted as dwelling burrows of sea anemones. In the specimens studied, the core contains coarser-grained material, and in one series of burrows, is composed of trilobitc fragments and micrite pellets. cemented with sparite. The central cylinder is interpreted to be a cast of the sea anemone's coelenteron, which in some specimens contains stomach contents.     

云南澄江早寒武世地层并论中国的Parabadiella,摩洛哥的Abadiella及澳大利亚的Abadiella huoi

根据近来的发现,区域地层的阐明及生物在寒武系界线上下的变化,澄江早寒武世地层划分作了修订。早寒武世岩石地层名称的更换,年代地层及生物地层单位的分带这里作了简述.目前的岩石地层单位从上到上是渔户村组（梅树阶）,黑林铺组（筇竹寺阶）,红井哨组、乌龙箐组（沧浪铺阶）及山邑村组（龙王庙阶）。此层序可分为2个亚带。所有的组合带在中国西南地台区都有存在,但两个亚带在澄江是区域性的。云南东部震旦系与寒武系的界线暂时置于渔户村且小歪头山段的底界,位于小壳化石最早出现的下部。中国的Parabadiella,摩洛哥的Abadiella及澳大利亚的Abadiella huoi这里重新作了研究。Parabadiella及Abadiella是两个不同的属。模式标本的图片在这里再次刊出。澳大利亚的Abadiella huoi一种应是Wutingaspis的一个新种（Wutingaspis jelli Chang sp.nov)。Opik(1975）的Dolerolenus(?)sp.nov.一种应归属Parabadiella huoi一种。Parabadiella是中国也是澳大利亚寒武系最古老的三叶虫。澳大利亚的Wutingaspis jelli的层位与摩洛哥Abadiella的层位相当,可与中国的Wutingaspis-Eoredichia带的上部对比。     

Early Cambrian biogeography in the North Atlantic region

A model of Early Cambrian trilobite biogeography in the North Atlantic region (Theokritoff 1979. Lethaia 12 , 281–295) is reviewed and modified in the light of new data. The presence of Wanneria in conglomerates bearing the Elliptocephala asaphoides fauna strengthens correlation of the E. asaphoides fauna as well as, by implication, the upper part of the Calluvia Zone with the middle part of the Bonnia-Olenellus Zone. The faunas of the Bastion Formation of East Greenland and of the Devil's Cove Limestone of northern Newfoundland are reinterpreted as shelf faunas. Additional occurrences of Archaeocyatha are noted in Spain and northwest Scotland but reports of Archaeocyatha in northern Norway and East Germany are not authenticated. Neither Salterella nor 'Volborthella' are now recognized as characteristic of any trilobite province. Although Ordovician acritarch provinces show congruence with trilobite provinces, available data on Early Cambrian plankton are not sufficient to support algal provincialism. Interpretation of the geological record suggests that the Early Cambrian lapetus Ocean was stratified with a well-mixed oxygenated zone overlying a phosphate-rich oxygen minimum zone and that the Elliptocephala asaphoides fauna should be reinterpreted as a warm-water fauna.     

Potential Global Standard Stratotype-section and Point (GSSP) for a Cambrian stage boundary defined by the first appearance of the trilobite Ptychagnostus atavus, Drum Mountains, Utah, USA

The base of the Ptychagnostus (or Acidusus) atavus Zone is one of the most clearly recognizable horizons on an intercontinental scale in the Cambrian System, and would serve as an excellent position for the base of a new stage-level chronostratigraphic subdivision. Among well-exposed, readily accessible sections in Laurentia, the “Stratotype Ridge” section, Drum Mountains, western Utah, USA, is perhaps the most suitable for a Global Standard Stratotype-section and Point (GSSP) defined by the first appearance datum (FAD) of the cosmopolitan agnostoid trilobite P. atavus. In the “Stratotype Ridge” section, the FAD of P. atavus occurs near the base of a calcisiltite bed 62 m above the base of the Wheeler Formation. A position corresponding closely to this horizon can be recognized with precision in Gondwana, Siberia, Kazakhstan, and Baltica using a combination of stratigraphic tools, the most useful of which are trilobite biostratigraphy, conodont biostratigraphy, and sequence stratigraphy. Brachiopod biostratigraphy and chemostratigraphy provide general constraints on the position of the horizon intercontinentally.     

The morphology of Opabinia regalis and the reconstruction of the arthropod stem-group

Opabinia regalis Walcott is an enigmatic fossil from the Middle Cambrian Burgess Shale of uncertain affinities. Recent suggestions place it in a clade with Anomalocaris Whiteaves from the Burgess Shale and Kerygmachela Budd from the Greenlandic Sirius Passet Fauna; these taxa have been interpreted as 'lobopods'. Consideration of available Opabinia specimens demonstrates that reflective extensions from the axial region, previously thought to be either gut diverticula or musculature, can be accommodated in neither the trunk nor the lateral lobes that arise from it. They must therefore be external structures independent of the lateral lobes. On the basis of their sub-triangular appearance, size and taphonomy, they are considered here to represent lobopod limbs. Some evidence for the existence of terminal claws is also presented. The question of whether Kerygmachela, Opabinia and Anomalocaris constitute a monophyletic or paraphyletic grouping is considered. While they share several characters, most of these are plesiomorphies. Further, Opabinia and Anomalocaris share several arthropod-like characters not possessed by Kerygmachela. It is concluded that these three taxa probably form a paraphyletic grouping at the base of the arthropods. Retention of lobopod-like characters within the group provides important documentation of the lobopod-arthropod transition. A proper understanding of Opabinia and its close relatives, which may include the tardigrades, opens the way for a reconstruction of the arthropod stem-group. This in turn allows the construction of a speculative but satisfying scenario for the evolution of major arthropod features, including the origin of the biramous limb, tergites and arthropod segmentation. 'Arthropodization' may thus be seen not to be a single event but a series of adaptive innovations. OPABINIA, ANOMALOCARIS, KERYGMACHELA, Burgess Shale, problematica, Lobopodia, Arthropoda.     

贵州剑河中寒武世中期甲劳组水母状化石的发现

贵州剑河革东镇八郎村南甲劳组中部钙质白云岩中新近发现的具有粗强放射状辐管的水母状化石和其下凯里组中具细辐管及同心环的拟轮盘水母(Pararotadiscus)有明显区别,属于伊尔东钵科(Eldoniidae)。其层位晚于中寒武世早期凯里生物群中拟轮盘水母(Pararotadiscus)层位1个化石带,属中寒武世中期,是该类化石在中国的最高层位,相当于北美布尔吉斯页岩生物群中Eldonia化石层位。     

Controls on gut phosphatisation: the trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah)

Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods – typically the most diverse fossilised organisms in Cambrian ecosystems – where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace.     

Biostratigraphy of the Peri-Gondwana Cambrian trilobite fauna (northern Kerman,Iran) and correlation with other countries

Polymeroid trilobite fauna from two stratigraphic sections (Godbondar and Kuhbanan) of the Kuhbanan Formation in northern Kerman (central Iran) were studied and subjected to biostratigraphic analysis. Eleven genera and species are recognised from the latest Early Cambrian and Middle Cambrian Peri-Gondwanian successions of the study sections. The recognised fauna includes Afghanocare lategenatum, Blountia blountia, Iranoleesia sp., Iranoleesia pisiformis, Kermanella kuhbananensis, Kermanella lata lata, Kermanella lata minuta, Kermanella sp., Redlichia chinensis, Redlichia noetlingi and Redlichia sp. Based on trilobite distribution, three trilobite biozones were recognised in the study sections, namely Redlichia noetlingi biozone, Kermanella kuhbananensis biozone and Iranoleesia pisiformis biozone. The age of the study sections is late Early Cambrian to late Middle Cambrian based on the recognised trilobite biozones. The recognised late Early Cambrian trilobite assemblages (especially Redlichia and Kermanella) from northern Kerman are similar to those found from some other parts of Gondwana or Peri-Gondwana terrains (north India, Pakistan, northwestern Kashmir, Tajikistan, South Australia, South China and Afghanistan) and show affinities with fauna found in some other parts of Iran (Alborz, northern Iran; Tabas, eastern Iran; southeast Karman).