A new brittle star (Ophiuroidea: Ophiodermatina) from the Early Triassic Paris Biota (Bear Lake County,Idaho, USA)

Knowledge on the morphology of Early Triassic ophiuroids is very limited, in spite of the relatively high number of described species. This hampers attempts to use morphology-based phylogenetic analyses in order to explore the early diversification of the ophiuroid modern clades between the latest Paleozoic and the early Mesozoic. Here, a new ophiuroid from the Early Triassic of southern Idaho (USA) is described and assigned to the new taxon Shoshonura brayardi Thuy nov. gen., nov. sp. It is part of an exceptional Early Triassic faunal assemblage recently described as the Paris Biota. On account of the arm morphology and the shape of the arm spines and arm spine articulations, Shoshonura brayardi nov. gen., nov. sp. is considered a basal member of the suborder Ophiodermatina.     

Biogenic Iron Preserves Structures during Fossilization: A Hypothesis

It is hypothesized that iron from biological tissues, liberated during decay, may have played a role in inhibiting loss of anatomical information during fossilization of extinct organisms. Most tissues in the animal kingdom contain iron in different forms. A widely distributed iron-bearing molecule is ferritin, a globular protein that contains iron crystallites in the form of ferrihydrite minerals. Iron concentrations in ferritin are high and ferrihydrites are extremely reactive. When ancient animals are decaying on the sea floor under anoxic environmental conditions, ferrihydrites may initialize the selective replication of some tissues in pyrite FeS₂. This model explains why some labile tissues are preserved, while other more resistant structures decay and are absent in many fossils. A major implication of this hypothesis is that structures described as brains in Cambrian arthropods are not fossilization artifacts, but are instead a source of information on anatomical evolution at the dawn of complex animal life.     

A new holocrinid (Articulata) from the Paris Biota (Bear Lake County,Idaho, USA) highlights the high diversity of Early Triassic crinoids

After the end-Permian crisis and the extinction of their four Paleozoic subclasses, crinoids rapidly recovered. This group is classically believed to have radiated from a small surviving clade and to have diversified during the Middle and Upper Triassic from two lineages. Nevertheless, recent findings suggested that several lineages of crinoids had already diversified during the Early Triassic, and that their diversity has been overlooked. Here we describe a new form of holocrinid, Holocrinus nov. sp., from the earliest Spathian (Early Triassic) of southeastern Idaho (USA). So far, the exceptional completeness of sampled specimens, with skeletal elements of arms and stem in connection, is unique for the Early Triassic. They show that derived morphological features had already evolved ∼1.3 million years after the Permian–Triassic boundary, supporting the scenario of a rapid Early Triassic diversification of crinoids.     

Middle Triassic conodont apparatus architecture revealed by synchrotron X-ray microtomography

The composition of conodont apparatuses is crucial for understanding the feeding mechanisms of these early vertebrates. However, the multielement apparatus reconstructions of most species remain equivocal because they have been inferred from loose element collections, guided by knowledge from rare articulated ‘bedding plane assemblages’ and fused clusters, often from distantly related taxa. Even these natural assemblages can be difficult to interpret because the component elements can be closely juxtaposed or embedded in matrix, making it hard to discern the morphology of each element and their relative positions within the architecture of the feeding apparatus. Here we report five exceptionally preserved conodont clusters from the Middle Triassic Luoping Biota, Yunnan Province, Southwest China. These materials were scanned using synchrotron radiation X-ray tomographic microscopy (SRXTM), revealing the morphology and positional homology of the component elements in the fused clusters. We confirm that the apparatus of Nicoraella was composed of eight types of elements, comprising a total of 15 elements. SRXTM reveals the positional homologies of the component elements, viz. a single alate element is located in the S₀ position, flanked successively abaxially by pairs of breviform digyrate S₁ and S₂ elements, bipennate S₃ and S₄ elements, and a pair of inwardly curved breviform digyrate M elements. Carminate elements occupy the P₁ and P₂ positions. The apparatus of Nicoraella is among the most completely characterised of all conodonts and serves as a template for the reconstruction of gondollellids.     

New data on the palaeobiology of the enigmatic yunnanozoans from the Chengjiang Biota,Lower Cambrian,China

Interpretation of the enigmatic soft‐bodied yunnanozoans from the Lower Cambrian (Stage 3, Series 2) Chengjiang Biota has remained controversial for decades because of their strange body plan and their variable taphonomic alteration. Proposed affinities have ranged from stem bilaterian to stem vertebrate. A study of over seven hundred slabs, many newly collected, from five sections at two localities demonstrates that yunnanozoans have sclerotized dorsal and axial segments, a body cavity, a unique feeding region and a coiled alimentary canal. Although two genera have been previously discriminated, all specimens have the same number of filamentous arches (seven pairs) and of ventral circular structures (four pairs); this indicates that Haikouella Chen, Huang and Li, 1999 is a junior synonym of Yunnanozoon Hou, Ramsköld and Bergström, 1991. Our analysis reveals new details of the putative pharyngeal pores of Yunnanozoon lividum, and although there are similarities with the gill slits of deuterostomes, the question of their homology remains moot. The filamentous arches and their supporting rods were probably sclerotized and represent a specialized feeding structure. Yunnanozoans exhibit characters that are open to a number of alternative interpretations of putative homology, encompassing comparisons with deuterostomes and protostomes (including members of the Platyzoa). Given their unique features, and the current lack of secure homologies, the affinities of yunnanozoans should continue to be considered in a wider bilaterian context.     

寒武纪凯里生物群在贵州镇远竹坪地区的发现

贵州东部镇远县竹坪地区付家冲寒武系凯里组中上部Oryctocephalus indicus带至Peronopsis taijiangensis带粉砂质泥岩、泥岩中新发现丰富的多门类化石组合,共计22属及3未定属种,分属海绵动物、节肢动物、腕足动物、软体动物、棘皮动物、腔肠动物,鳃曳动物、水母状动物及藻类9大门类,其中动...     

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.     

Liaoxia Cao et S.Q. Wu (Gnetales): ephedroids from the Early Cretaceous Yixian Formation in Liaoning, northeastern China

Gnetalean compression-impression fossils are described from the Early Cretaceous Yixian Formation, Liaoning Province, north-eastern China, and assigned to six species of Liaoxia Cao et S.Q. Wu. The fossils have opposite-decussate phyllotaxis and cones comprising 2–12 pairs of bracts. Ovulate cones have seeds typically in a distal position. The species differ from each other and from previously described fossils in the absence or presence of leaves, shape of cones and seeds, and shape and position of cone bracts. The species of Liaoxia are probably close relatives of extant species of Ephedra L., but diagnostic reproductive details that could confirm this hypothesis are not preserved. The restricted information in the fossils and the poorly understood morphological diversity of extant Ephedra, prevent assignment of the fossils to any particular subgroup of Ephedra, as well as an explicit exclusion of them from the extant genus.     

A new choristodere (Reptilia: Diapsida) from the Lower Cretaceous of western Liaoning Province, China, and phylogenetic relationships of Monjurosuchidae

The publication of the scientific name Monjurosuchus splendens in 1940 documented the first tetrapod fossil of the later world-renowned Jehol Biota. For more than half a century since this discovery, however, Monjurosuchus has remained as a monotypic genus of the family Monjurosuchidae, and the relationships of the family with choristoderes have not been correctly recognized until quite recently. In this paper, a new monjurosuchid is named and described based on a nearly complete skull and postcranial skeleton from the Early Cretaceous Chiufotang Formation exposed near Chaoyang, western Liaoning Province, China. This new material documents the first occurrence of monjurosuchid choristoderes outside the type Lingyuan area, and extends the geological range of the family from the Yixian Formation to the younger Chiufotang Formation. Cladistic analyses were conducted with inclusion of monjurosuchids, and the results support the placement of the family Monjurosuchidae as a primitive clade outside the Neochoristodera. A new classification scheme is proposed for choristoderes on the basis of the recovered phylogenetic framework of the group.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 145 , 427–444.