Natural assemblages of Hindeodus conodonts from a Permian–Triassic boundary sequence,Japan

Hindeodus parvus and Hindeodus typicalis occur in a deep‐water chert and claystone section in the Mino Terrane, Japan, which has been identified as a Jurassic accretionary complex. Conodont fossils are preserved as natural assemblages of impression fossils on bedding planes in claystone. In this study, 13 assemblages of Hindeodus species were recognized, comprising at most 13 elements which generally maintain the original composition and structure of an apparatus. We discriminated pairs of carminiscaphate P₁, angulate P₂ and makellate M elements, as well as a single alate S₀ element and two digyrate and four bipennate elements constituting the S array. Although the digyrate and bipennate elements are preserved in the S₂ and S_3–4 positions, respectively, a pair of S₁ elements was not found due to incompleteness in the natural assemblages. The conodont biostratigraphy indicates that the lithological boundary between chert and claystone units in the study section corresponds exactly to the Permian–Triassic boundary.     

Conodonts from the Early Triassic microbialite of Guangxi (South China): implications for the definition of the base of the Triassic System

We describe a new Early Triassic (Griesbachian) succession of conodont faunas from a high‐resolution sampling of the basal Early Triassic microbial limestone and the base of the overlying unit at the Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). The microbial limestone records the earliest phase of the Early Triassic biotic recovery after the end‐Permian mass extinction. For the first time, rich conodont faunas are reported from within the microbialite. The faunas from Wuzhuan are largely dominated by anchignathodontids, including several Isarcicella species, which were previously documented only from strata above the microbialite. A total of 14 conodont species assigned to three genera is recorded from the Wuzhuan section. Starting from the base of the microbialite upwards, several species are sequentially added to the conodont assemblage. The alpha diversity peaks at the top of the microbialite. The conodont record in the considered microbialite interval at Wuzhuan is presumably unaffected by local ecological changes. It therefore more likely represents an evolutionary rather than an ecological pattern. We compare the Wuzhuan's conodont record with a well‐supported phylogenetic model and suggest that the sequence of first occurrences at Wuzhuan is the closest to the ‘true’ sequence of evolutionary events that took place during this Griesbachian radiation of anchignathodontids. Based on comparisons with the GSSP section at Meishan, we suggest further that the first occurrence of Hindeodus parvus in Meishan does not correspond to its first appearance datum.     

Parafurnishius,an Induan (Lower Triassic) conodont new genus from northeastern Sichuan Province,southwest China and its evolutionary implications

A fundamental aspect of taxonomy at the generic level, critical to understand Early Triassic conodont evolution, is the composition of the multielement apparatus. In this paper, we document a platform-bearing new conodont genus, Parafurnishius n. gen., as well as its multielement apparatus from the Griesbachian Feixianguan Formation (Lower Triassic) in Xuanhan County, northeastern Sichuan Province, southwest China. The new conodont genus is characterized by numerous robust and irregularly distributed conical denticles with variable platform morphology that has a possible affinity with the P₁ elements of Furnishius. These genera have apparatuses similar to those of Ellisonia and are classified with the family Ellisoniidae. The strong intraspecific variation of P₁ elements and the growth series within the entire sample population suggest that Parafurnishius may have evolved from the Griesbachian Isarcicella by developing random denticle positioning away from the platform centre, and then possibly evolved into younger Triassic Furnishius by developing a stable blade configuration. This preferred interpretation implies an ellisonid apparatus for Isarcicella. Alternatively, Parafurnishius may have evolved from Ellisonia and developed a homeomorphic P₁ element with Isarcicella. This new taxon has strong intraspecific variation of denticle growth orientation during the Early Triassic.     

中国西藏聂拉木色龙西山二叠系—下三叠统牙形刺

本文详细描述了西藏聂拉木色龙西山二叠系—下三叠统牙形刺共７属２０种;组建了自下而上的７个牙形刺带：Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ,Ｃｌａｒｋｉｎａｃａｒｉｎａｔａ,Ｎｅｏｓｐａｔｈｏｄｕｓｋｕｍｍｅｌｉ,Ｎ,ｃｒｉｓｔａｇａｌｌｉ,Ｎ．ｐａｋｉｓｔａｎｅｎｓｉｓ,Ｎ．ｗａａｇｅｎｉ,Ｎｅｏｇｏｎｄｏｌｅｌｌａｊｕｂａｔａ－Ｎｅｏｓｐａｔｈｏｄｕｓｔｒｉａｎｇｕｌａｒｉｓ带;发现了这些牙形刺带与菊石带的对比关系。色龙西山剖面缺失二叠系顶部的层位,由于色龙群顶部产Ｍｅｓｏｇｏｎｄｏｌｅｌｌａｉｄａｈｏｅｎｓｉｓ,Ｍ．ｐｈｏｓｐｈｏｒｉｅｎｓｉｓ和Ｍ．ｓｐｐ．等牙形刺,其时代可能为栖霞晚期至茅口早期,考虑到再沉积的可能性,其时代也不会晚于吴家坪期。下三叠统发育较完整,特别是底部,但是由于再沉积或凝缩的原因,在三叠系底部常有二叠系的牙形刺出现或出现混合动物群。本文讨论了二叠－三叠系界线,并把菊石Ｏｔｏｃｅｒａｓｌａｔｉｌｏｂａｔｕｍ带和牙形刺Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ带之底作为三叠系之底界。     

Testing hypotheses of element loss and instability in the apparatus composition of complex conodonts: articulated skeletons of Hindeodus

Knowledge of the conodont skeleton, in terms of the morphology of the elements and the positions they occupy, provides the foundation for understanding of homology, taxonomy and evolutionary relationships in conodonts. This knowledge also underpins analyses of conodont functional morphology and feeding. Direct evidence of skeletal anatomy and apparatus architecture comes from natural assemblages: fossils that preserve together the articulated remains of the conodont apparatus, either collapsed onto a bedding plane or as clusters of elements in which juxtaposed and overlapping elements have been fused together by diagenetic minerals. Here we describe six clusters of the biostratigraphically important conodont Hindeodus parvus from the Lower Triassic Shangsi section, Sichuan Province, South China. Five of these clusters represent the partial remains of articulated skeletons, providing direct evidence of the number and arrangement of elements in the apparatus. Combined with data from previously published natural assemblages this provides a test of the hypothesis that Triassic conodonts had a reduced dentition. Hindeodus parvus possessed a complete raptorial array of two M and nine S elements (unpaired S₀; symmetrically paired S₁, S₂, S₃, S₄); the paired P₁ locations were occupied by carminiscaphate elements, but the apparatus lacked P₂ elements. This is consistent with broader evidence for a particularly high degree of integration and constraint operating on the S–M array of morphologically complex conodonts, leading to conserved architecture of the array over a period of more than 250 million years. The loss of elements from the P domain implies a change in food processing ability and, given the predominance of data from P elements in conodont taxonomy and biostratigraphy, the hypothesis of element loss from the P domain has significant implications for the broader understanding of conodont diversity and evolutionary patterns.     

泥盆纪最早期和最晚期珊瑚群研究的进展——兼论泥盆纪珊瑚的绝灭、复苏及其底栖组合

由于志留泥盆纪之间没有发生明显的生物更替现象,所以泥盆纪最早期（Ｌｏｃｈｋｏｖｉａｎ）的珊瑚仍保留着浓厚的志留纪珊瑚的色彩。真正的泥盆纪类型的珊瑚是从早泥盆世中期（Ｐｒａｇｉａｎ）才开始兴起的,至晚泥盆世早期（Ｆｒａｓｎｉａｎ）末惨遭绝灭。晚泥盆世晚期（Ｆａｍｅｎｎｉａｎ）的珊瑚却与石炭纪珊瑚有着较为密切的关系。晚泥盆世的珊瑚经历了绝灭残存复苏３个发展阶段。泥盆石炭纪之交,泥盆纪最晚期（Ｓｔｒｕｎｉａｎ）的珊瑚再遭绝灭,至石炭纪初代之于Ｔｏｕｒｎａｉｓｉａｎ型的珊瑚。正当华南锡矿山（相当于Ｆａｍｅｎｎｉａｎ早期）的珊瑚群罹难的时刻,新疆北部洪古勒楞（亦相当于Ｆａｍｅｎｎｉａｎ早期）却形成了Ｆ／Ｆ大绝灭后生物理想的避难所。     

Allometry in Anisian (Middle Triassic) segminiplanate conodonts and its implications for conodont taxonomy

Conodonts are a clade of chordates and are valuable indicator fossils for biostratigraphy. The segminiplanate (neogondolelliform) conodonts represent a major morphological group ranging from upper Carboniferous to Upper Triassic marine sediments. However, the morphological similarity of segminiplanate P₁ elements generates problems for taxonomy, especially in the Permian and Triassic clades. This paper represents the first study of morphological variation in Triassic segminiplanate conodonts using a geometric morphometric approach. The laminar microstructures observed in conodont cross‐sections indicate that, within our analysed specimens, smaller conodonts with fewer laminae are generally from an earlier ontogenetic stage while larger conodonts with more laminae are from a later stage of ontogeny. Using linear regressions between relative warp scores from both upper and lateral views and conodont length, we demonstrate strongly allometric growth patterns for the species Paragondolella bifurcata Budurov & Stefanov. Our results indicate that the species‐group taxon Pg. praeszaboi bystrickyi (Kovacs et al.) is an early growth stage of Pg. bifurcata and thus synonymous. We suggest that the allometry of conodonts should be considered seriously, especially when there are numerous transitional morphologies between large‐ and small‐sized conodonts. Reconstructing the ontogenetic series and using larger‐sized conodonts within the numerous transitional morphologies in the population of a rock sample for the definition of new species are suggested for future studies.     

Brachiopods and other fossils from the Permo-Triassic boundary beds of the Antalya Nappes (SW Taurus, Turkey)

An uppermost Permian-Lower Triassic biota of brachiopods, conodonts, algae and foraminifers from the Pamucak and Kokarkuyu formations at Çürük Da? (Antalya, Turkey) is here described. The brachiopods belong to two different assemblages: a lower assemblage, early Wuchiapingian in age, with Spinomarginifera cf. S. helica, Spinomarginifera cf. S. iranica, Alatorthotetina sp. ind., Orthothetina sp. ind., Ombonia antalyensis nov. sp. and few specimens of Pennospiriferinoidea; an upper assemblage, Changhsingian in age, comprising S. cf. S. iranica, Spinomarginifera cf. S. spinosocostata, Spinomarginifera sp. ind. and Orthothetina sp. ind., characteristic taxa of the low diversity survival brachiopod faunas of latest Permian age (Survival Fauna 1). The occurrence of the conodont Hindeodus cf. praeparvus above the brachiopod fauna confirms its Changhsingian age. The oolitic grainstones at the top of the Pamucak Formation contain Permocalculus sp., Macroporella cf. apachena, species of Hemigordius and Palaeozoic Lagenida. Coarse calcite fibrous cements pervade the oo-bioclastic grainstones, suggesting early marine cementation. The base of the Kokarkuyu Formation is characterized by the disaster forms Earlandia amplimuralis and “Cornuspira” mahajeri, gastropods and ostracods. The conodont Isarcicella lobata has been recovered 31 m above the base of the Kokarkuyu Formation, indicating the occurrence of the second Triassic conodont zone above the parvus biozone and below the staeschei biozone. The faunal content at the transition of the Pamucak and Kokarkuyu formations records the biotic survival in the aftermath of the end-Permian extinction. Facies evolution from lower energy inner platform wackestones and packstones to higher energy open platform oolitic grainstones indicates a transgression at the top of the Pamucak Formation, which continues into the Lower Triassic Kokarkuyu Formation.     

Stromatolite-dominated microbialites at the Permian–Triassic boundary of the Xikou section on South Qinling Block,China

Permian–Triassic boundary microbialites (PTBMs) are organosedimentary carbonates formed immediately after the end-Permian mass extinction. All those reported PTBMs constrained by convincing conodont biozones are present stratigraphycally not higher than the Hindeodus parvus zone and most of them are dominated by thrombolites. This paper provides the first record of a brief, but spectacular development of stromatolite-dominated PTBMs within the basal Isarcicella isarcica conodont zone of the earliest Triassic from the Xikou section of South Qinling Block that was at the margin of the North China Block during the Permian–Triassic transition and was geographically separated from the major occurrence of post-extinction microbialites in the South China Block. This stromatolite cap overlies a 3.7-m-thick oolitic limestone and is composed of a lower 0.2-m-thick bed and an upper 0.5-m-thick bed, separated by a 0.2-m-thick greyish green siliciclastic mudstone. These two stromatolite beds mainly consist of columnar stromatolites with subordinate domal stromatolites. The intercolumn and interstitial spaces within the stromatolites are filled with oolitic grainstones. At the microscopic scale, laminoid structures in stromatolites comprise wavy, millimetric-domical and tangled laminae. The increased grain and fossil contents and/or bioturbation in the domical and tangled laminae indicate that the formation of these laminae is likely related to an increase in the populations and the disruptions by benthic metazoans, as well as an influx of sediment grains. The δ¹³C_carb values fluctuate between 2‰ and 3‰ in the uppermost Permian strata; a distinct negative shift of 1.9‰ occurs at the topmost oolitic grainstone, just below the lower stromatolite bed, and the lowest value of −0.1‰ is located at the base of the upper stromatolite bed. The stratigraphic succession from stromatolites to thrombolites of the PTBMs may represent a transgressive succession and/or a transient ecosystem recovery immediately after the end-Permian mass extinction. The thrombolites-dominated PTBMs mainly developed in near-equator shallow marine geographic locations, and stromatolite-dominated PTBMs mainly developed at higher latitude settings, which probably indicates that a relatively lower diversity and abundance of marine benthic metazoans existed at higher latitudes after the end-Permian mass extinction.     

Antitropicality and convergent evolution: a case study of Permian neospiriferine brachiopods

Antitropical distribution is a biogeographical pattern characterized by natural occurrences of the same species or members of the same clade in the middle‐ or middle‐to‐high‐latitudinal habitats of both hemispheres, either on land or in marine environments, without appearing in the intervening tropical environments. For most of the noted examples of Permian antitropical distribution, particularly in marine invertebrates, the causes of disjunctions have been mainly linked to either dispersal or vicariance models. Little attention has been paid to other possible mechanisms. This study investigated the antitropicality of some Permian neospiriferine brachiopods through detailed taxonomic revision, comparison of palaeobiogeographical distribution, and a phylogenetic analysis. Several species, previously assigned to Kaninospirifer, are here reassigned to other genera, especially to Fasciculatia in the northern hemisphere and to Quadrospira in the southern hemisphere during the Permian. Both Kaninospirifer and Fasciculatia appear to have been restricted to north‐western Pangea and north‐eastern Asia during the Permian, but there is no robust evidence to suggest their presence in the southern hemisphere to which Imperiospira and Quadrospira were confined. In spite of the distributional separation between the two pairs of neospiriferine genera in the Permian palaeobiogeographical regime, they share considerable numbers of morphological characters, such as a large shell, subdued fasciculation, and reduction of ventral adminicula. Notwithstanding these morphological similarities, our phylogenetic reconstruction of the neospiriferines does not support a close relationship between these genera. This therefore must indicate that these similar morphological features were independently acquired, probably with these taxa living in spatially separate but ecologically compatible environmental conditions in the mid‐latitudinal area of each hemisphere during the Permian. We regard this as an example of convergent evolution.     

An assessment of the status of Polycirridae genera (Annelida: Terebelliformia) and evolutionary transformation series of characters within the family

A phylogenetic analysis was performed to determine the monophyly of non‐monotypic genera of the terebelliform family Polycirridae, i.e. Polycirrus, Amaeana, Lysilla, and Hauchiella, and the evolution of characters among members of this clade. The monotypic genera, Enoplobranchus and Biremis, were also included, together with members of both known species in Hauchiella. Representative species were included for remaining genera: 14 species of Polycirrus, six species of Amaeana, and six species of Lysilla. Out‐groups consisted of representatives of Spionidae, Cirratulidae, and Sabellariidae, as well as several species of Telothelepodidae. A total of 40 in‐ and out‐group species were coded for 50 subjects (‘characters’) and 117 subject–predicate relationships (‘states’). Although results are consistent with recent phylogenetic studies within Terebelliformia that suggest Polycirridae monophyly, only Hauchiella was found to be monophyletic, albeit part of the more inclusive clade comprising remaining polycirrid genera. Evolutionary transformation series are discussed for selected characters in relation to the non‐monophyly of Polycirrus, Lysilla, and Amaeana. Implications for the use of supraspecific taxa as ‘taxonomic surrogates’ are highlighted. The definition of Polycirridae is emended. © 2015 The Linnean Society of London     

Late Bashkirian and early Moscovian conodonts from the Naqing section,Luodian, Guizhou,South China

Late Bashkirian and early Moscovian conodonts are abundant and diverse at the Naqing section, South China. All conodont genera known to have numerous species in the late Bashkirian–early Moscovian are recorded here, including Declinognathodus, Diplognathodus, Gondolella, Idiognathodus, Idiognathoides, Mesogondolella, Neognathodus, and Neolochriea. At Naqing, many species of these genera provide a succession of conodont chronomorphoclines throughout the Bashkirian–Moscovian boundary interval. They demonstrate that deposition was remarkably continuous through the boundary interval, a major criterion for selecting a Global Stratotype Section and Point (GSSP). This paper describes the current state of knowledge for several of these chronomorphoclines, and also provides an updated range chart of conodonts recovered from the Naqing section and their correlation with other regions.The taxon that best matches the current concept for the base of the Moscovian Stage in its type region is the phylogenetic first occurrence of Diplognathodus ellesmerensis. An ancestral form with most of the characteristics of D. ellesmerensis occurs at Naqing. More specimens are needed to completely document the chronomorphocline, but because D. ellesmerensis is found worldwide — including that close to the base of the type Moscovian — its evolutionary first occurrence would provide an almost ideal GSSP to define the base of the international Moscovian Stage.     

A new study of Olenekian–Anisian boundary conodont biostratigraphy of the Tulong section in Himalaya Terrane,southern Tibet

The Himalaya Terrane of southern Tibet exposes successive shallow-marine carbonate deposits from the Lower to Upper Triassic, and is a key region for studying the Triassic conodont biostratigraphy at the northern margin of the Indian Plate. On the basis of newly collected samples from the Kangshare and Laibuxi formations at the Tulong section, 11 conodont species of 7 genera were identified, and four conodont zones were established, namely, the Novispathodus abruptus Zone (lower Spathian, first reported in Tibet), the Columbitella jubata Zone (middle Spathian), the Triassospathodus symmetricus Zone (upper Spathian), and the Chiosella timorensis Zone (lowermost Anisian) in ascending order. The first occurrence (FO) of Chiosella timorensis indicates the Olenekian–Anisian boundary (OAB) at Bed 25, upper part of the Kangshare Formation. The regional and global correlation of these conodont zones is synthesized.     

The early Triassic rhynchosaur Mesosuchus browni and the interrelationships of basal archosauromorph reptiles

Restudy of the unique diapsid reptile Mesosuchus browni Watson, from the Cynognathus Assemblage Zone (late Early Triassic to early Middle Triassic) of the Burgersdorp Formation (Tarkastad Subgroup; Beaufort Group) of South Africa, confirms that it is the most plesiomorphic known member of the Rhynchosauria. A new phylogenetic analysis of basal taxa of Archosauromorpha indicates that Choristodera falls outside of the Sauria, Prolacertiformes is a paraphyletic taxon with Prolacerta sharing a more recent common ancestor with Archosauriformes than with any other clade, Megalancosaurus and Drepanosaurus are sister taxa in the clade Drepanosauridae within Archosauromorpha, and are the sister group to the clade Tanystropheidae composed of Tanystropheus, Macrocnemus, and Langobardisaurus. Combination of the phylogenetic relationships of basal archosauromorphs and their known stratigraphic ranges reveals significant gaps in the fossil records of Late Permian and Triassic diapsids. Extensions of the temporal ranges of several lineages of diapsids into the Late Permian suggests that more groups of terrestrial reptiles survived the end-Permian mass extinction than thought previously.     

Genetic diversity and phylogenetic position of the subclass Astomatia (Ciliophora) based on a sampling of six genera from West African oligochaetes (Glossoscolecidae, Megascolecidae), including description of the new genus Paraclausilocola n. gen

To more confidently assess phylogenetic relationships among astome ciliates, we obtained small subunit (SSU) rRNA sequences from nine species distributed in six genera and three families: Almophrya bivacuolata, Eudrilophrya complanata, Metaracoelophrya sp. 1, Metaracoelophrya sp. 2, Metaracoelophrya intermedia, Metaradiophrya sp., Njinella prolifera, Paraclausilocola constricta n. gen., n. sp., and Paraclausilocola elongata n. sp. The two new species in the proposed new clausilocolid genus Paraclausilocola n. gen. are astomes with no attachment apparatus, two files of contractile vacuoles, and an arc-like anterior suture that has differentiations of thigmotactic ciliature on the anterior ends of the left kineties of the upper surface. Phylogenetic analyses were undertaken using neighbor-joining, Bayesian inference, maximum likelihood, and maximum parsimony. The nine species of astomes formed a strongly supported clade, showing the subclass Astomatia to be monophyletic and a weakly supported sister clade to the scuticociliates. There were two strongly supported clades within the astomes. However, genera assigned to the same family were found in different clades, and genera assigned to the same order were found in both clades. Thus, astome taxa appear to be paraphyletic when morphology is used to assign species to genera.     

The first tunicate with a calcareous exoskeleton (Upper Triassic,northern Italy)

The first tunicates with a calcareous exoskeleton are reported from Late Triassic buildup‐slope deposits of the Dolomites. Although examples of this group have been known since the early 1900s from the middle–upper Permian of eastern Asia and Sicily as Khmeria, they were erroneously attributed to rugose corals. These early representatives are small, double‐valved, conical skeletons, which evolved into multi‐plated capsules with up to 35 opercula. The latter are joined along zigzag margins, which in life could probably be opened for the atrial and branchial siphons. The construction and shape of these skeletons distinguish them from plants or other invertebrate phyla, while they share several similarities with living tunicates, specifically to sessile ascidians. Apart from a soft‐bodied genus from the lower Cambrian of China, ascidians are known only from isolated spicules, which occur sporadically from the Lower Jurassic onwards. The calcareous skeleton of these Late Triassic tunicates consists of aragonitic fibres, which form spherulitic or clinogonal microstructures. It seems that the stellate aragonitic spicules of Jurassic to Recent ascidians are a vestige of Permian–Triassic ancestors, which after the Carnian lost the ability to construct compound solid skeletons but partly still retain a soft double‐valved or multi‐operculate cellulose‐like tunic. The following taxa are described as new: Order Khmeriamorpha with the genera Khmeria Mansuy and Zardinisoma gen. nov., and the following species: Khmeria stolonifera (late Permian), Khmeria minima (Late Triassic), Zardinisoma japonicum (late Permian), Z. cassianum, Z. pyriforme, Z. polyplacophorum and Z. pauciplacophorum (all Late Triassic).     

Morphology and Phylogeny of Two Novel Ciliates,Arcanisutura chongmingensis n. gen., n. sp. and Naxella paralucida n. sp. from Shanghai,China

The morphologies of two novel ciliates, Arcanisutura chongmingensis n. gen., n. sp. and Naxella paralucida n. sp., collected from Shanghai, China, have been investigated using live observation and silver staining methods. Arcanisutura n. gen. can be easily distinguished from related genera by its inconspicuous, oblique anterior suture. Arcanisutura chongmingensis n. sp. is mainly recognized by its elongated body with a tail‐like posterior end, 25–33 somatic kineties, and 4–11 excretory pores. Naxella paralucida n. sp. can be distinguished from its congeners based on its two short nassulid organelles, fusiform trichocysts, 37–49 somatic kineties, and 16 nematodesmal rods. The small‐subunit (SSU) rRNA gene sequences of these two species are presented, revealing the phylogenetic positions of Arcanisutura and Naxella. Phylogenetic analyses show that Arcanisutura forms a sister clade to other synhymeniid genera, namely, Chilodontopsis, Orthodonella, and Zosterodasys; Naxella is most closely related to Nassula spp. and is located within the monophyletic clade of the family Nassulidae.