Aequiloboidea: A new Early Jurassic ammonite superfamily of the Mediterranean Tethys

A comprehensive outline of the Jurassic ammonoid superfamily Aequiloboidea is here presented: this group is known from? Rhaetian-early Hettangian to early Pliensbachian and it is exclusively found within the Mediterranean Tethys (Austrian Alps, Bavarian Prealps, Tuscany, Umbria-Marche and Abruzzi Apennines, Morocco, Tunisia, western Hungary). On the basis of the available documentation, it is composed by two families (Aequilobidae and Sinuiceratidae), to which five genera belong: Aequilobus Bilotta (previously informally indicated as “genus from Monte Bove”), Dudresnayiceras Rakús, Sinuiceras Venturi and Ferri, and Sphenoacanthites Venturi, Nannarone and Bilotta, plus Xenoloboceras nov. gen., which position at the family level is uncertain. All of them share a peculiar combination of morpho-structural characters, which was never observed in any form referable to known groups. Due to the particularities presented by the Aequiloboidea and to the scarce documentation on the earliest Jurassic in the Mediterranean regions, it is currently impossible to demonstrate that this taxon originated within any of the already-known Jurassic ammonoid orders (Phylloceratida and Psiloceratida). An at least partially independent derivation cannot be excluded, as suggested also by the results of a cladistic analysis.     

First evidence of brachiopod diversification after the end-Triassic extinction from the pre-Pliensbachian Internal Subbetic platform (South-Iberian Paleomargin)

Lower Jurassic brachiopods are widely known in the External Betic Zone. Their occurrence was so far virtually restricted to the easternmost Subbetic Zone where they underwent a diversity burst and radiation event during the late Sinemurian–early Pliensbachian interval, leading to a bloom in brachiopod diversity from the early Pliensbachian onwards. Taxonomical and paleobiogeographical analyses performed in a newly recorded assemblage from the most offshore areas of the Subbetic Basin (Granada province, Spain) reveals that this diversification event occurred earlier than expected hitherto, probably in the Turneri–Obtusum chronozones, as similarly observed in the most intra-Tethyan basins such as the Northern Calcareous Alps and Transdanubian Ranges, illustrating the recovery of the background conditions for the establishment of diversified brachiopod communities after the end-Triassic extinction event. A new rhynchonellide species, Alebusirhynchia vorosi nov. sp., is formally described among the ten different taxa recorded for the first time in this area. The Mediterranean paleobiogeographical affinities revealed by the brachiopod assemblage emphasizes that the onset of the Mediterranean/Euro-Boreal bioprovinciality and the initial brachiopod diversification in the pre-Pliensbachian Internal Subbetic platform took place earlier in the Sinemurian as well, following the Euro-Boreal monotypic record previously reported in this region.     

Ammonite diversity and its palaeobiogeographical structure during the early Pliensbachian (Jurassic) in the western Tethys and adjacent areas

The early Pliensbachian (Early Jurassic) is known as a time of marked provincialism in the marine realm, notably between the Mediterranean Tethys and North–West Europe. In order to test this observation quantitatively, we compiled 104 locality-level species lists from those areas based on a comprehensive revision of early Pliensbachian ammonites. With this dataset, we also explore the relationship between ammonite richness and biogeography at the scale of the sub-chronozone during the early Pliensbachian. Using various multivariate statistics and rarefaction techniques, we show that: (i) there is a sharp contrast between the NW European (NWE) and the Mediterranean (MED) provinces, although there is some mixing in Austroalpine and Pontic ammonite faunas; (ii) species richness in the MED province is about twice that in the NWE province for each chronozone; (iii) ammonite species richness tends to decrease during the early Pliensbachian, especially at the Ibex–Davoei transition; and (iv) the NWE and MED sensu stricto provinces both record the same pattern of variations in richness despite the fact that their taxonomic compositions have virtually nothing in common at the species level. We suggest that the low ammonite richness of the Davoei chronozone may be related to a coeval warming of seawaters, but that this was insufficient to affect the sharp palaeobiogeographic contrast between the two provinces. This persistent compartmentalisation probably reflects a major palaeogeographical structure, such as an emerged or near-emerged barrier running from the Betic range to the Briançonnais ridge. Overall, it seems that the diversity and distribution of early Pliensbachian ammonite species were simultaneously controlled by climate, palaeogeography and eustasy.     

Diversity and extinction patterns of permian brachiopoda of South China

The stratigraphical and geographical distribution of 851 brachiopod species from 216 genera and 65 families in the Permian of South China are analysed. It is revealed that the brachiopod diversity underwent two sharp falls during the Permian. The first occurred at the end of Maokouan, accompaning the widely recognised, extensive regression across the Maokouan‐Wujiapingian boundary. Fifty‐seven species of 29 genera survived this first major extinction event. The second sharp reduction of brachiopod diversity took place in the later Changhsingian, with only 17 Permian‐type brachiopod species of 12 genera straggling into the earliest Triassic. Detailed stratigraphic analysis shows that more than 90% of the Changhsingian brachiopod species disappeared at different levels in the Changhsingian before the widely perceived end‐Permian ‘mass extinction’ occurred. It is also notable that each of the step‐wise diversity reduction events was apparently heterochronous. In view of the evidence from lithologies, faunal components and geochemical analyses, the two sharp falls of Permian brachiopod diversity in South China are considered to be closely related to multiple interactions of an environmental deterioration caused by large‐scale regressions.     

Evolutionary patterns in the terebratulid genus Caryona Cooper (Brachiopoda,Jurassic of France)

The study of ontogenetic and morphological changes in different species of the brachiopod genus Caryona COOPER (Terebratulidae) from the Lower Callovian‐Lower Oxfordian of northern France shows a succession (and an interference) of processes which vary according to the characters studied. This is an example of “mosaic evolution”;. The ontogenetic changes result from heterochrony, especially acceleration and hypermorphism. The main phylogenetic tendency is peramorphosis in most characters. This evolutionary pattern agrees with phyletic gradualism.

Moreover, analysis of the internal characters demonstrates the limited value of these in discrimination of the various genera.     

Toarcian carbon isotope shifts and nutrient changes from the Northern margin of Gondwana (High Atlas, Morocco, Jurassic): Palaeoenvironmental implications

The Early Toarcian is marked by a global perturbation of the carbon cycle and major marine biological changes. These coincide with a general decrease in calcium carbonate production and an increase in organic carbon burial, and culminate in the so-called Toarcian Oceanic Anoxic Event. It is believed that the environmental crisis was triggered by the activity of the Karoo-Ferrar large igneous province. In order to further document the Early Toarcian palaeoenvironmental perturbations, carbon isotope, total organic matter, calcareous nannofossils and phosphorus content of the Amellago section in the High Atlas rift basin of Morocco were investigated. This section is extremely expanded compared to the well-studied European sections. Its position along the northern margin of the Gondwana continent is of critical importance because it enables an assessment of changes of river nutrient input into the western Tethyan realm. The carbon isotope curve shows two negative excursions of equal thickness and amplitude, at the Pliensbachian-Toarcian boundary and at the transition from the Polymorphum to the Levisoni Zone. This confirms the supra-regional nature of these shifts and highlights the possible condensation of the first “boundary” shift in European sections. Phosphorus content is used to trace palaeo-nutrient changes and shows that the two negative carbon isotope shifts are associated with increased nutrient levels, confirming that these episodes are related to enhanced continental weathering, probably due to elevated greenhouse gases in the atmosphere. In the High Atlas Basin, the increase in nutrient levels at the Pliensbachian-Toarcian boundary is moreover likely to be the main factor responsible for the coeval demise of the Saharan carbonate platform. A middle Toarcian event, centered on the boundary between the Bifrons and Gradata Zones, characterized by a positive carbon isotope excursion and nutrient level rise, is documented in the Amellago section.     

The genus <Emphasis Type="Italic">Unispirifer</Emphasis> Campbell (Brachiopoda,Spiriferida) in the Early Carboniferous of the Moscow Syneclise

Two new species of the genus Unispirifer Campbell, U. semicircularis and U. parvus, are established as a result of a revision of Early Carboniferous spiriferids from the Moscow Syneclise. These forms have previously been described under Spirifer tornacensis Koninck, 1883 and S. taidonensis Tolmatschow, 1924.     

Patterns of biotic change in Middle Jurassic to Early Cretaceous Tethyan radiolaria

The rate of taxic turnover of nearly 400 radiolarian species/subspecies is analyzed in order to document long term biotic change of plankton during the Middle Jurassic to Early Cretaceous (Aalenian to Aptian). The pattern and dynamic of diversity change is described using four indices: rate of species first and last occurrence, rate of diversification and rate of turnover. Plots of cumulative sampling effort suggest that the analyzed data represent an adequate sample of total standing diversity for most examined stages. Rates of species first occurrence exceed rates of last occurrence for most of the Middle Jurassic, except for the middle Bajocian. In contrast, the Late Jurassic was a time of decreasing radiolarian diversity and the Kimmeridgian records the lowest rate of diversification. It is followed by a dramatic increase in first occurrences near the Jurassic–Cretaceous boundary with as a result the highest rate of diversification recorded in the late Tithonian. Regional radiolarian diversity was stable throughout most of the Early Cretaceous. A stratigraphic permutation test was performed to assess the influence of uneven sampling on the observed pattern of taxic turnover and identified the intervals for which randomly obtained patterns are significantly different from the observed pattern. The Kimmeridgian and late Tithonian events coincide with substantial climate-derived perturbations in water cycling, nutrient supply and oceanic productivity. They point to a negative relationship between radiolarian macroevolution and changes in the state of nutrient availability, although further work is needed to refine the temporal resolution of this relationship and to explore ecological aspects of its causal link with respect to radiolarian evolution.     

Jurassic radiolarites in a Tethyan continental margin (Subbetic, southern Spain): palaeobathymetric and biostratigraphic considerations

A region of the pelagic Subbetic basin within the Southern Iberian Continental Margin is studied in lithostratigraphical and biostratigraphical detail. Jurassic radiolarites (Jarropa Radiolarite Formation, Bathonian–Oxfordian) interbedded with shallow-water marine limestones have been recognized. Underlying the radiolarites (Camarena Formation, Bajocian) are oolitic limestones showing shallowing-upward cycles with karstic surfaces on the top, corresponding to deposition on an isolated carbonate platform on volcanic edifices. The Milanos Formation (upper Kimmeridgian–Tithonian), overlying the radiolarites, contains calciclastic strata with hummocky cross-stratification, which indicate outer carbonate ramp deposition. In the Jarropa Radiolarite Formation some calcisiltite strata with hummocky cross-stratification have been found. The bathymetry of the Subbetic Jurassic pelagic sediments, including the radiolarites, is considered as moderate or shallow in depth. We suggest that the pelagic character of the Jurassic sediments in this margin and their equivalents in other Alpine domains is a consequence of distance from the continent (beyond the pericontinental platform) but not necessarily of depositional depth.     

Middle and Late Jurassic terebratulides from New Zealand

Terebratulide brachiopods are found throughout the New Zealand Mesozoic, and by the Jurassic are second only to rhynchonellides in abundance and diversity. Only two species have been described from the Late Jurassic, Kutchithyris hendersoni Marwick, 1953 and Holcothyris (?) kaiwaraensis Campbell, 1965. In this study, one new genus and 14 new species are described, and three additional forms placed in open nomenclature.Nearly all the material comes from the Murihiku Terrane on the west coast of the North Island south of Auckland, and most from a small number of shellbeds with diverse faunas. Two key localities for Middle Jurassic (Bajocian–Bathonian) brachiopods are Opuatia Cliff at Port Waikato, and a quarry in the Marokopa Valley. Two species of fairly large terebratulide, Loboidothyris waitomoensis n. sp. and L. grantmackiei n. sp. are tentatively assigned to the genus Loboidothyris. A further species which may also belong to this genus, L. awakinoensis n. sp. is found in the Awakino Valley to the south. Two species of Zeilleria, Z. opuatiaensis n. sp. and Z. waiohipaensis n. sp. and one of Aulacothyris, A. waikatoensis n. sp. are also recognised. A new species of Kutchithyris, K. marokopaensis n. sp., less strongly folded than K. hendersoni, is also present.Captain King's Shellbed is a metre-thick Oxfordian shellbed that can be traced from Kawhia to the Awakino Valley. It has a rich and diverse fauna in which terebratulides are prominent. Kutchithyris hendersoni is the most abundant, followed by Crispithyris nauarchus n. gen. n. sp. The fauna also includes the same two species of Zeilleria as in the Middle Jurassic, and the costellate terebratulide Terebratulina leeae n. sp.Brachiopods are much less common in the later part of the Jurassic (Kimmeridgian and Tithonian). A further species of Kutchithyris, K. challinori n. sp., a second species of Terebratulina, T. putiensis n. sp. and one of Zeilleria (Z. sp.) are present. A rare form is the small subcircular Disculina mancenidoi n. sp. Holcothyris kaiwaraensis is known only from the Late Jurassic Pahau Terrane of North Canterbury, but a second species of Holcothyris, H. campbelli n. sp. is present in the Late Oxfordian and Kimmeridgian of the Kawhia area.Aulacothyris, Terebratulina, and Zeilleria are cosmopolitan. Kutchithyris and Holcothyris are Tethyan. Loboidothyris is more widely distributed but generally Tethyan. Disculina is described from Southern England and France, but has since been recognised in the Caucasus and Japan, and may also have a Tethyan distribution.     

Oxygen‐restricted facies of the basal Jurassic of North West Europe

Events across the Triassic‐Jurassic boundary are a matter of great interest because this marks the time of one of the five biggest marine mass extinctions in the Phanerozoic. Some of the best sections across the boundary are in north west Europe; attention here is focussed on the basal Jurassic. Sedimentological and palaeoecological study has been undertaken of a number of sections in England and Germany, most of them borehole cores, and indicate a range of oxygen‐restricted facies, signifying episodic fluctuations between anoxic and dysoxic conditions. Analysis of the Th/U ratio in the coastal outcrop of St. Audrie's, Somerset, confirms this interpretation. The Triassic‐Jurassic boundary in north west Europe is characterised by a regression‐transgression couplet, with the corresponding sea‐level change being quite possibly of short duration.     

THE ENIGMATIC EARLY CAMBRIAN SALANYGOLINA– A STEM GROUP OF RHYNCHONELLIFORM CHILEATE BRACHIOPODS?

Abstract:  New material of the enigmatic brachiopod Salanygolina obliqua Ushatinskaya from the Early Cambrian of Mongolia shows that it has a colleplax – a triangular plate – in the umbonal perforation, which is enlarged by resorption. This structure is otherwise only known from the equally enigmatic Palaeozoic orders Chileida and Dictyonellida (Rhynchonelliformea, Chileata). The colleplax in Salanygolina is here considered to be homologous with that of the chileates. Salanygolina is also provided with a ridge-like pseudodeltidium, which is another chileate feature. Other characters of Salanygolina , like the radial arrangement of adductor muscle scars and postero-medially placed internal oblique muscles are characteristic of chileates, but also found in the paterinates. In contrast, mixoperipheral dorsal valves with low rudimentary interareas are well known in paterinates, but not yet recorded from chileates. Thus, Salanygolina shows a mosaic combination of morphologic characters, known both from the paterinates and chileates, indicating that it may represent a stem group of the rhynchonelliform chileate brachiopods. The laminar phosphatic secondary shell of Salanygolina is composed of closely packed and nearly identical hexagonal prisms, oriented with their long axis normal to the laminae in a honeycomb pattern. The prism walls appear to have originally been composed of organic membranes and might represent precursors of the organic sheaths of calcite fibers that are typical of calcitic shells with a fibrous microstructure.     

紧凑型夏玉米群体的辐射截获

测量了紧凑型夏玉米 (掖单 1 3)群体的太阳总辐射和光合有效辐射 ( PAR)的反射率、透过率和截获率 .结果表明 ,紧凑型夏玉米具有直立型叶片的透光和截获特点 ,抽雄前总辐射和 PAR的消光系数分别为 0 .2 84和 0 .40 1 ,良好的透光特性使紧凑型夏玉米比平展型的能承受更大的种植密度 .雄穗的透过率约为 75% ,去掉部分雄穗能改善叶簇的光照条件 .本文探讨了总辐射和 PAR的日平均截获率 (āQ)和 (āu)和绿色叶面积指数 ( L )的关系     

A quantitative palaeobiogeographical analysis on the distribution of Sterlitamakian‐Aktastinian (Early Permian) western Pacific brachiopod faunas

A presence/absence data matrix of 183 genera from 29 faunal stations (selected from 33 initially compiled faunal stations on the basis of sampling and study adequacies) is analysed by cluster analysis, nonmetric multidimensional scaling, principal coordinate analysis and minimum spanning tree. Five core faunal groups are revealed and interpreted as representing five biotic provinces. They are the Verkolyma Province embracing the Kolyma Massif, Verchoyan Mountains, east Zabaikal, central north Mongolia, Inner Mongolia and the Sikhote Alin terrane; the Cathaysian Province of the Yangtze block, North China block, the Tarim Basin and the Kitakami Masssif; an incipient Cimmerian Province composed of western peninsular Malaysia and south Thailand; the Westralian Province of the Western Australian intracratonic basins, Timor, Irian Jaya, peninsular India, the Himalaya, Lhasa terrane, western Qiangtang block and the Baoshan block; and the Austrazean Province of eastern Australia and New Zealand. The palaeogeographical implications of the provincial patterns recognised are discussed and a modified version of Sterlitamakian‐Aktastinian western Pacific palaeogeography is presented.