An operculum of the Silurian nautiloid Aptychopsis from Arctic Canada

Three articulated valves of the genus Aptychopsis are interpreted as the operculum of a nautiloid. The valves are joined by an organic film which covers the entire dorsal valve. This genus has not been previously reported from North America.     

Aptychopsid plates - jaw elements or protective operculum

The three plates characteristic of Aptychopsis have been described as a jaw apparatus in this orthocone cephalopod as well as an operculum for it. Due to the limited material, interpretations have in various cases been made from photographic illustrations and those results are discussed in this article. The area of the aptychopsid plates is compared with the apertural area of the cephalopod and the results show a great similarity. Arguments for and against soft parts outside the aptychopsid plates are discussed as well as the position of the plates. Material from a Silurian shale in southern Sweden is described. ? Aptychopsis, aptychopsid plates. Cephalopoda, operculum, jaw apparatus, Silurian.     

The earliest vascular land plants: continuing the search for proof

New collections from Bringewoodian strata (Silurian, Ludlow Series, Saetograptus leintwardinensis incipiens Zone) in Wales have yielded the oldest known specimens of the plant Cooksonia . From evidence at younger (Eř;éolí/Downton) horizons this genus is considered to be a vascular plant; although no tracheids have been isolated from the Bringewoodian specimens, on the basis of comparative morphology they are concluded to be the oldest recorded tracheophytes. The types of evidence relevant to the identification of vascular plants are briefly reviewed, and the relationships of the Welsh Cooksonia flora to other late Silurian floras are discussed. Confident stratigraphical dating is a prerequisite for any discussion of early plant evolution, emphasising the desirability of an integrated approach incorporating both geologial and palaeobotanical investigations. The dating of two published records of diverse Silurian floras, including lycopods, is questioned; recent dating of the Australian Baragwanathia flora as early Ludlow on the basis of graptolites is not supported by the shelly faunal evidence, which indicates a correlation within the Lower Devonian.     

Heterochrony in Silurian phacopid trilobites as suggested by the ontogeny of Acernaspis

New material of early growth stages of the Silurian (Llandovery) trilobite Acernaspis is described. Pre-adult ontogenetic stages of this genus closely resemble adults of the post-Llandovery genus ***Ananaspis. A heterochronic descent of Ananaspis from Acernaspis is proposed. ***Ananaspis is interpreted as pae-domorphic, having arisen largely through neoteny. Neotenic changes already appear in the lineage in the last Acernaspis species, and Ananaspis then underwent continuous ncotcnic change throughout its known Silurian history. ▭ Heterochrony, neoteny, Silurian, Trilobita, Phacopidae, Acernaspis. Ananaspis.     

论志留纪陕西珊瑚属Shensiphyllum Ge et Yü,1974

ShensiphyllumGeetYü,1974为丛状复体珊瑚,以发育一列马蹄型鳞板,羽榍扇形排列为主要特征,是志留纪四射珊瑚已知唯一发育马蹄型鳞板的属。该属在我国上扬子区广泛分布于上兰多维列统(Llandovery)特列奇阶(Telychian)中,主要产自川北、陕南的宁强组、云南大关的大路寨组(中、上Telychian阶))、湖北长阳的纱帽组及四川朝天的王家湾组(下特列奇阶)。文中报道和描述川北朝天王家湾组中发现的3个新种Shensiphyllumsimplexsp.nov.,S.proliferumsp.nov.,S.intermediumsp.nov.。王家湾组是已知ShensiphyllumGeetY櫣产出的最低层位。详细讨论该属的骨骼构造特征、生长繁殖方式,探讨该属起源及其演化,根据新资料修订该属的属征,赞同将该属置PhacellophyllidaeWedekind科。     

Silurian craniide brachiopods from Gotland

Seven craniide brachiopod genera are described from the Silurian (Wenlock–Ludlow) of Gotland, including one new genus and five new species. The new genus and species Thulecrania septicostata is unique among Silurian craniides as it possesses solid spines. The new species Lepidocrania multilamellosa is the first Silurian record of this poorly known Permian genus. The problematic North American Propatella Grubbs, 1939 , was originally described as a gastropod, but the new species Propatella palmaria from Gotland shows that it is a craniide with sutured hollow spines of a type not previously recorded from Silurian craniides. The dorsal valves of the new species Valdiviathyris? bicornis are remarkably similar to those of the type species and represent the first possible Palaeozoic record of this poorly known extant craniide. This first systematic study of craniide brachiopods from the Silurian of Gotland shows that the diversity is relatively high as compared to other known Silurian craniide faunas, but a more thorough comparison is not possible due to the lack of data from most parts of the world. The new data from Gotland support the view that the craniides were not affected by the end‐Ordovician extinction.     

Pattern of some Silurian bioevents

The best‐known Silurian bioevent occurred at the end of the Wenlock: the lundgreni event, together with the nassa‐ludensis crisis, was established among planktic graptolites. The East Baltic data show several peaks of high diversity (especially triangulatus, turriculatus, scanicus zones) and three levels of low diversity of graptolites (antennularius, radians, ludensis zones). These are more or less coincident with sea‐level changes. Energetic innovation of the shallow shelf corals started in the early Silurian. The late Wenlock regression seems not to affect them seriously but the late Silurian decline coincides with the aridization of the climate and a regression of the shelf seas. The Agnatha had strong radiations in the Wenlock (ludensis Zone) and Ludlow (leintwardinensis Zone), the fishes in the Pridoli. Many Silurian vertebrates were long‐ranging and extinction rate was relatively low; only at the late leintwardinensis level and in the latest Ludlow did considerable extinctions occur.     

Apertural constrictions in some oncocerid cephalopods

Stridsberg, Sven 1981 12 15: Apertural constrictions in some oncocerid cephalopods. Lethaia , Vol. 14, pp. 269–276. Oslo. ISSN 0024–1164.
In some oncocerid cephalopods the shape of the aperture, siphuncle and the general outline of the shell have long served as generic characters. The aperture is mostly elaborated into a certain number of sinuses which take their final shape only in the adult. Therefore, knowledge of the relative age of the animal is required. The last chamber may serve as an indicator of age. A last chamber smaller than the second last indicates a mature specimen. This is because continued growth would have caused the death of the animal as the buoyancy turned negative. Moreover, it is of great importance to study the growth lines along the peristome to observe whether growth has ceased or not. Growth variations have been compared with growth stages. Furthermore, a constricted or contracted aperture can only be determined on specimens with the shell still preserved. Functional parallels are drawn between the Aprychopsis operculum and the restricted aperture. * Cephalopoda, Oncorerida. aperture, ontogeny, growth lines, functional morphologv , Aptychopsis. Silurian, Gotland .     

Siluro-devonian Conodonts from the Camelford Limestone, Wellington, New South Wales, Australia

Conodont data have been utilized to identify the Silurian/Devonian boundary within the Camelford Limestone near Wellington, NSW. Conodont faunas are documented from the eosteinhornensis Zone to early delta Zone with one new species of Walliserodus ( W. multistriatus ) and two new species of Ozarkodina ( O. brocki and O. camelfordensis ) described. An apparatus reconstruction of Belodella anomalis is also presented.     

A NEW SILURIAN EURYPTERID (ARTHROPODA: CHELICERATA) FROM CHINA

Abstract:  The oldest eurypterid from China is described as Hughmilleria wangi sp. nov., from the Xiaoxiyu Formation (Silurian: latest Llandovery) of Hunan Province. H. wangi is relatively similar to two species from North America, but differs in the development of epimera on the postabdomen, a slightly wider carapace, a styliform telson and the dimensions of the penultimate podomere of the paddle. The Llandovery age of the specimen substantially reduces the ghost range of the genus Hughmilleria . The exact phylogenetic relationship between the different species in Hughmilleria , the most basal genus in the pterygotoid clade, cannot be resolved because the plesiomorphic states within this clade are poorly known. The shapes of the telson and swimming paddle of the Chinese species suggest that it is more primitive than its North American relatives, which is in accord with its greater age.     

Genetic evidence for wild-living Aspideretes nigricans and a molecular phylogeny of South Asian softshell turtles (Reptilia: Trionychidae: Aspideretes, Nilssonia)

Aspideretes nigricans was long thought to be one of the rarest turtle species of the world, being restricted to a single site in Bangladesh; its specific distinctness was repeatedly doubted. Using mtDNA sequence data of all four Aspideretes species, we provide evidence that A. nigricans is a distinct species that is sister to A. hurum . Furthermore, A. nigricans is not endemic to Bangladesh, but also occurs in Assam, India. While all applied phylogenetic analyses (Bayesian Analysis, Maximum Likelihood, Maximum Parsimony, Neighbor Joining) strongly suggest a well-supported clade containing the four Aspideretes species and Nilssonia formosa , the monophyly of Aspideretes is at best weakly supported. We propose to synonymise the genera Aspideretes Hay, 1904 and Nilssonia Gray, 1872, resulting in an expanded genus Nilssonia with the species N. formosa (Gray, 1869), N. gangetica (Cuvier, 1825), N. hurum (Gray, 1831), N. leithii (Gray, 1872) and N. nigricans (Anderson, 1875). Genetic structure within N. nigricans is weak, while we detected two distinct genetic lineages within N. gangetica , one occurring in the Brahmaputra River system and the other in the Ganges and Indus River basins.     

A survey of running crab spiders (Araneae: Philodromidae) in Iran

Nine species and four genera of Philodromidae are identified and recorded from various parts of Iran including Pulchellodromus medius (O. Pickard-Cambridge, 1872) (genus and species new to Iran) and Thanatus setiger (O. Pickard-Cambridge, 1872) (new to Iran). The male of Rhysodromus hierosolymitanus (Levy, 1977), which was previously known only from females, is described and diagnosed here.     

The Late Namurian genusCancelloceras (Carboniferous Ammonoidea) and its distribution

The genusCancelloceras (family Gastrioceratidae) comprises three subgeneraCancelloceras, Crencelloceras n. subgen. andMonitoceras differing in conch ornamentation.Cancelloceras is cosmopolitan and regarded as the index genus for the Upper Namurian G₁ Zone, the Yeadonian. The lower boundary of the G₁ Zone is defined by the entry ofCancelloceras (Crencelloceras) branneroides, whereas the first representatives of the genus appeared earlier, in the Middle Namurian R₂ Zone. The upper boundary of the G₁ Zone is marked by the extinction ofCancelloceras and the entry of its descendant genusGastrioceras. Cancelloceras comprises 27 species.     

A southward extension of the Silurian Tuvaella brachiopod fauna

The co-occurrence of Tuvaella gigantea Chernyshev, Tannuspirifer pedaschenkoi (Chernyshev), Leptos-trophia elegestica Chernyshev and Stegerhynchus sp. in the Upper Hongliuxia Formation, Barkol, NE Xinjiang, China, shows that this is a representative of the well-known Tuvaella Fauna in China. The correlation of the Tuvaella gigantea Assemblage Zone of the Upper Hongliuxia Formation at its type locality is discussed to document the correlation of this formation with the Pichishui Beds of the Upper upper Chergak Formation in Tuva, the Woduhe Formation m the Lesser Khingan Mountains, and other equivalents based on the presence in some abundance of T. gigantea , and without T. rackovskii. The Tuvaella gigantea-bearing strata are tentatively assigned to the Ludlow. With regard to the paleozoogeographic affinity of the Tuvaella Fauna it is at present suspected by some that the area inhabited by Tuvaella represents a peculiar zoogeographic province or region during the Silurian. However, the information available indicates that the Tuvaella occurrences in east-central Asia represent nothing more than a specialized environmental situation in the light of the presence of a single endemic genus, i.e. Tuvaella itself, among 25 articulate brachiopod genera examined. The evidence of both lithology and brachiopods investigated has important implications for suggesting a shallow, commonly rough-water environment between low intertidal and high subtidal areas.     

Graptolite extinction at the Llandovery—Wenlock boundary

Combined graptolite range data through the late Llandovery and early Wenlock of the Canadian Arctic Islands, the British Isles, and Lithuania reveal that survivorship rates from one zone to the next are between 56 and 85%, except at the Llandovery—Wenlock boundary, where only 19% (8 of 42) of the taxa of the upper sakmaricus—crenulata Zone survive into the centrifugus Zone. The high rate of graptolite extinction appears to coincide with glacioeustatic sea-level fall and may be attributed to changing oceanic temperatures, salinity, circulation patterns, oxygenation, and/or productivity associated with the onset of a glacial maximum event. □ Graptolite, extinction, Silurian, Llandovery, Wenlock.     

Phylogenetic position and generic status of the Japanese botiid loach

The phylogenetic position revealed by partial mtDNA sequence analysis supports the placement of the Japanese botiid loach into the genus Parabotia Dabry de Thiersant 1872 instead of Leptobotia Bleeker 1870; i.e., Parabotia curta (Temminck and Schlegel 1846) is its valid name.     

THE EARLY JURASSIC AMMONITE BADOUXIA FROM BRITISH COLUMBIA, CANADA

Abstract:  Most species of the Lower Jurassic ammonite genus Badouxia are restricted to the eastern Pacific where they are of fundamental importance to the Hettangian/Sinemurian ammonite zonation of North America. The fauna from the type area for the genus has been restudied and four species and two transitional forms are now recognized. Badouxia forticostata and Badouxia castlensis are new. Badouxia occidentalis (Frebold) and Badouxia oregonensis Taylor are placed in synonymy with Badouxia canadensis (Frebold). These major taxonomic changes and subsequent modification to the range of B . canadensis require revisions to the current zonation for the Western Cordillera of North America. The Oregonensis Zone is re-named the Mineralense Zone. The Canadensis Zone is abandoned and its previously defined Rursicostatum and Columbiae subzones are elevated to the level of full zones. Large samples indicate that most species of Badouxia display a remarkable range of continuously variable morphology. In addition, the genus shows some of the best-documented evidence of sexual dimorphism in Early Jurassic ammonites. Badouxia spans the Hettangian/Sinemurian boundary and based on the range of different species, five stratigraphic intervals are recognized. Intervals 1–3 correlate with the north-west European Angulata Zone. The majority of interval 4 and the whole of interval 5 correlate with the north-west European Bucklandi Zone. The age of the base of interval 4 is uncertain.     

DISCOVERY OF MONOGRAPTIDS IN BASAL PART OF LOWER SILURIAN FROM S. ANHUI WITH SPECIAL REFERENCE TO THEIR ORIGIN

For a long time, the evolutionary series of a idoraptids-dimorphograptids-monograptids has been generally recognized by graptolite researchers. In the past years, the akidograptids were found to appear in the Lower Silurian Parakidograptus acuminatus Zone, while the dimorphograptids in the P. acuminatus and Orthograpius vesiculosus Zones, but the monograptids appeared as late as in the O. vesiculosus zone; this evolutionary series can be easily accepted by other people. Chen Xu and Lin Yao-kun (1978) pu...     

LUNGMACHI FORMATION GRAPTOLITES FROM SANLANGPU OF XIXIANG, SOUTHERN SHAANXI

The specimens referred to the Lungmachi Formation graptolites in the present paper were collected from Sanlangpu of Xixiang, Southern Shaanxi, consisting of 8 genera and 51 species or subspecies including 12 new species (see Table l in the Chinese text). This paper describes only the new species, with the rest being shown in tablesand plates. According to the present data on hand, the Lungmachi Formation graptolites studied here may be divided into 4 zones as follows:4. Orthograptus vesiculosus Zone (L_3)3. Parakidograptus acuminatus Zone (L_2)2. Glyptograptus persculptus Zone (L_1)1. Diplograptus bohemicus Zone (W_6)The first graptolite zone belongs to the Upper Ordovician, while the others to the Lower Silurian, indicating that the Lungmachi Formation in our studied area is a lithostratigraphic unit stridling across the Ordovician-Silurian boundary.This paper is in commemoration of the respectable late Prof. Mu En-zhi, to whom the writers are very much obliged for his kindness inguiding their scientific researches.