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.     

Multivariate hierarchical analyses of Early Jurassic Ostracoda assemblages

Palaeobiogeographic patterns of Early Jurassic ostracods from the northern and southern hemispheres (96 sections located in Europe, North Africa, Western Australia and North and South America) based on 243 species-level records document global patterns of distribution that can be compared to those previously published on ostracods from the European Epicontinental Sea and Tethyan and South Panthalassa areas. All described records of ostracods from both hemispheres spanning the Hettangian to Early Toarcian have been compiled and verified, and their patterns of origin and distribution have been interpreted. Jaccard coefficient of similarity was used to asses similarities among European, American and Tethyan ostracod shelf faunas. The numerical analysis shows a progressive longitudinal gradient in provincialism through the Early Jurassic, consistent with the northward drift of Tethyan ostracod faunas towards the European Epicontinental Sea and the southward movement of European taxa into Tethys and Panthalassa oceans. The spread of cosmopolitan species and extinction of endemic species, allied to the disappearance of geographical barriers, warmer climate conditions and rising sea levels can explain the reduction in ostracod diversity and the east-west provincialism throughout the Early Jurassic. Interchange between hemispheres, including bipolar distributions, are recognized from the Sinemurian time, pointing out that for most of the studied period, the climate worldwide was warm and tropical.     

The cranial morphology of Kayentachelys,an Early Jurassic cryptodire,and the early history of turtles

Gaffney, E.S. and Jenkins, F.A., Jr. 2010. The cranial morphology of Kayentachelys, an Early Jurassic cryptodire, and the early history of turtles. — Acta Zoologica (Stockholm) 91 : 335–368 The skull morphology of Kayentachelys aprix Gaffney et al., 1987 , a turtle from the Early Jurassic Kayenta Fm of northern Arizona, demonstrates the presence of cryptodiran synapomorphies in agreement with Gaffney et al. (1987, 1991, 2007) , and contrary to the conclusions of Sterli and Joyce (2007) , Joyce (2007) , Sterli (2008) , and Anquetin et al. (2008) . Specific characters found in Kayentachelys and diagnostic of cryptodires include the processus trochlearis oticum, the curved processus pterygoideus externus with a vertical plate, and the prefrontal–vomer contact, which are confirmed as absent in the outgroups, specifically the Late Triassic Proganochelys. The Joyce (2007) analysis suffers from the reduction of the signal from skull characters, with a consequently greater reliance on shell characters, resulting in pleurodires being resolved at various positions within the cryptodires. Kayentachelys reveals what a primitive cryptodire would be expected to look like: a combination of primitive and derived characters, with the fewer derived characters providing the best test of its relationships to other turtles. Although incompletely known, the Mid‐Late Jurassic Condorchelys, Heckeremys, and Eileanchelys may be early cryptodires close to Kayentachelys. We confirm the Late Triassic Proterochersis as a pleurodire, dating the pleurodire–cryptodire split as Late Triassic or earlier.     

Methane seeps on an Early Jurassic dysoxic seafloor

The rhythmically bedded limestone–marl–shale succession of the Blue Lias Formation (Lias Group, Early Jurassic age) of Kilve in Somerset (SW England) preserves a suite of large conical concretions that formed around methane seeps. These are 1–2 m high, and elliptical in plan (axes 2–4 m), with an outer limestone shell forming the flanks of the cone. The cone flank is composed of micritic carbonate (20–30 cm thick), which locally includes sheets and pods of intraclasts and bioclasts. The cycle-forming limestone beds of the host strata are composed of dark grey micrite with carbon-isotope values (δ¹³C = 0.6 to 0.8‰) consistent with carbon sourced from a mixture of seawater and by sulphate reduction, and oxygen-isotope values (δ¹⁸O = − 6‰) suggesting some degree of later diagenesis. The pale grey micrite that forms the sides of the mounds includes three-dimensional ammonites and intraclasts, and thus cemented close to the sediment–water interface prior to compaction. The mound-forming carbonate is markedly isotopically light with respect to carbon, but not with respect to oxygen (δ¹³C = − 24.3 to − 26.4; δ¹⁸O = − 2 to − 3.5‰). The isotope signature indicates that cements were probably derived from a mixture of sources that included biogenic methane. The intraclasts within the limestone suggest that syn-depositional physical brecciation and mixing of cements had occurred, and thus mixing of methane rich-fluids with the overlying surface waters is likely also to have occurred. The relatively heavy oxygen-isotope values may be indicative of anaerobic oxidation of methane. The mound-bearing interval of the Blue Lias Formation is benthos-poor and comprises predominantly laminated black shales, characteristic of poor bottom water oxygenation. The largest of the mounds is however, capped with fossiliferous breccias. Thus the mounds either formed benthic islands that elevated the biota into an oxic zone or, alternatively, they may have supported a chemotrophic community. Although cold seep deposits have been documented previously they are still comparatively rare. This example is one of the oldest in Europe, and is unusual amongst described ancient seeps in preserving relief that extended above the ancient seafloor.     

Seafloor erosion and sea-level change: Early Jurassic Blue Lias Formation of central England

Minor bedforms within the mudstone-dominated Early Jurassic Hettangian Saltford Shale Member (Liasicus up to Angulata Chronozone) of the Blue Lias Formation in central England, indicate weak seafloor erosion in a mid to outer ramp setting. Distal storm flows below maximum storm wave base are proposed as the most likely generative mechanism for silty scour and gutter casts that enclose concentrations of well-preserved schlotheimiid ammonites and arthropod trace fossils. Within the upper part of the Saltford Shale (probably Angulata Chronozone), a discrete layer of reworked and bioencrusted limestone nodules signifies an episode of more persistent seafloor erosion. The immediately overlying strata, transitional to the Hettangian–Sinemurian Rugby Limestone Member, are relatively bioturbated and feature fossils of macrobenthos, as well as shell concentrations resembling relatively proximal storm beds. This suggests that the reworked nodule horizon marks sea-level fall, rather than stratigraphic condensation associated with sediment starvation. The biostratigraphic evidence raises the possibility that this erosional episode correlates with a mid-Angulata Chronozone hiatus documented from the Wessex Basin, southwest England. Equally however, it could be linked to contemporaneous movement on one or more nearby faults, affecting the southern part of the English East Midlands Shelf.     

Some Fossil Plants from Early Jurassic in Western Hubei With the Relative Problem Between Fossil Plants and Coal-Bearing

Coniopteris magnifica sp. nov., Ctenophyllum chenyuanense sp. nov., C. laxilobum sp. nov., Mironeura dakengensis Zhou, are derived from the Xiangxi Formation (s.s.), Western Hubei. According to the aspect and characteristic of the Xiangxi flora, author considers the Xiangxi Formation as Early Jurassic in age. In this paper, the relative problem between the coal-bearing and the fossil plants is briefly discussed also.     

云南早侏罗世一新具嵴冠兽脚类恐龙

报道了具嵴冠的兽脚类恐龙一新属种,安龙堡双柏龙(Shuangbaisaurus anlongbaoensis gen.et sp.nov.).双柏龙发现于云南省楚雄彝族自治州双柏县下侏罗统冯家河组中,保存了部分头骨带下颌.双柏龙沿两侧眼眶背缘向上有嵴冠发育,这在其他兽脚类中未曾报道过.与其他早侏罗世体型较大且具一对矢状嵴冠的兽脚类(双嵴龙属和中国龙属)相比,双柏龙还独具一些特征组合,如相对较高的前颌骨体、抬高的前颌骨腹缘、后腹向延伸的轭骨后突及较小的上颞孔.比较研究表明,尽管中国“双嵴龙”(“Dilophosaurus”sinensis)可能应归入中国龙属(Sinosaurus),但未必属于模式种.双柏龙的发现将有助于研究基干兽脚类的演化,尤其是各类头骨骨饰在其中的作用.     

New morganucodontans from an Early Jurassic fissure filling in Wales (United Kingdom)

Abstract: Two new genera and species of morganucodontans, Bridetherium dorisae and Paceyodon davidi, are recognized as members of the Morganucodon‐sphenodont fauna preserved in a fissure filling (Pant 4) exposed in Pant Quarry, Vale of Glamorgan, southern Wales. Both taxa are based on isolated molariforms. Mode of occlusion of upper and lower molariforms in B. dorisae differs from the embrasure shearing pattern of Megazostrodon and the offset pattern characteristic of Morganucodon. Lack of a clear correlation between different patterns of occlusion and morphologies of their molariforms supports the working hypothesis that a close correlation between function and morphology of the molars characteristic of therian mammals, for example, was not present in morganucodontans. P. davidi is based on an isolated morganucodontan molariform that is significantly larger than any yet discovered. Several isolated morganucodontan‐like molariforms cannot be referred to these taxa. The new Welsh morganucodontans added to records from other sites indicate the group achieved considerable taxonomic diversity and a near global distribution by the Early Jurassic.     

Morphological and structural adaptations to soft substrates in the Early Jurassic monomyarians Lithiotis and Cochlearites

Lithiotis problematica and Cochlearites loppianus are sessile monomyarian bivalves known from the Early Jurassic of the Tethyan region, where they are found standing vertically in the calcareous mud of lagoonal fades. Their shells are characterized by a long cardinal area, ventrally displaced body space, thick attached valve, and a thin, flat free valve of equal length. A functional ligament is present only in juvenile stages of Cochlearites. To grow straight, the ventral end of the shell had to gape, so in both species it was probably the elasticity of the thin free valve that caused the shell to open. In the adult stage the shell grew only towards the venter with an apparently constant growth rate, while the soft body size remained unchanged. The outer shell is composed of a compact aragonitic layer, while the inner part is filled with loose chalky deposits which are thought to have functioned as supporting the soft body and lifting it upwards. These and other morphologic and structural features, as well as the growth pattern, can be explained as an adaptation of a sessile animal to soft muddy bottoms and rapid sedimentation. Some elongated Crassostrea living in similar environments show remarkable morphologic and structural convergence with Lithiotis and Cochlearites.     

Victims of the Early Toarcian anoxic event: the radiation and extinction of Jurassic Koninckinidae (Brachiopoda)

The significant mass extinction attributed to the Early Toarcian anoxic event had a severe impact on the phylum Brachiopoda. Beyond a serious decrease of species diversity, the extinction of the orders Spiriferidina and Athyridida is connected with this episode. The order Athyridida was represented by the family Koninckinidae in the Early Jurassic. The stratigraphical and geographical distribution of the three Early Jurassic koninckinid genera ( Koninckella, Koninckodonta, Amphiclinodonta ) shows a definite radiative pattern. The number of their nominal species increased from 2 to 17 from the Sinemurian to Early Toarcian; in the same time interval, their area increased from the Alpine region to the whole Mediterranean and the NW-European domains. This radiative evolution can be explained as the result of different factors: (1) morphological adaptation to muddy bottoms, (2) fundamental changes in the current pattern in the Tethys/Laurasian Seaway, and, possibly, (3) utilization of methane-based chemosynthesis as alternative food source. The radiation of koninckinids, leading from the cryptic habitats of the Tethyan rocky floors to the extensive muddy bottoms of the open European shelves, was abruptly terminated by the anoxic event in the Early Toarcian Falciferum Zone. The main causes of the extinction might be: (1) the excessive warming of Tethyan deep waters by thermohaline circulation, (2) the anoxic event, which was not survived by the spire-bearers, handicapped by their stiff, calcareous spiralia. Brachiopoda, Early Jurassic, Europe, extinction, Koninckinidae, radiation, Tethys.     

Lavinipes Cheminii Ichnogen., Ichnosp. nov., A Possible Sauropodomorph Track from the Lower Jurassic of the Italian Alps

A new ichnotaxon is described from the Lower Jurassic (Upper Hettangian-Lower Sinemurian) carbonate tidal flats on the central-eastern Italian Alps. The narrow-gauge trackway is that of a large quadrupedal dinosaur. The pes is functionally tetradactyl with three rounded antero-medially directed digits, and the manus is pentadactyl. This quadrupedal form is close to Otozoum and Pseudotetrasauropus jaquesi both traditionally related to sauropodomorph trackmakers. The similarity with Otozoum is so marked that Lavinipes and Otozoum could be cogeneric. But the overall evidence today is that the Otozoum trackmaker was generally bipedal, whereas the trackmaker of L. cheminii is fully quadrupedal. The manual prints of L. cheminii show five short clawless digits and are different from the tetradactyl slender toed manual prints of Otozoum. The possible sauropodomorph affinity of the L. cheminii trackmaker is here discussed with an attempt to a revision of the Late Triassic-Jurassic tracks which have been traditionally related to sauropod and prosauropod.     

New Early Jurassic brachiopods from the Western Tethys (Eastern Subbetic, Spain) and their systematic and paleobiogeographic affinities

Two new brachiopod genera (Alebusirhynchia and Praesphaeroidothyris), five new species (Alebusirhynchia jorali, Salgirella? goicoecheai, Praesphaeroidothyris cisnerosi, Lychnothyris lancisi, and Cincta peiroi) and a new combination (Securina plicata) have been recorded and established after the internal and external morphological study of populations attributed to Lower Jurassic carbonate successions of the South-Iberian Paleomargin (SE Spain). The analysis made enables us to detail the diagnostic characters of little-known genera such as Lychnothyris or Securina and to clarify the systematics of the group from new supraspecific definitions, establishing a new, strongly multicostate rhynchonellid genus (Alebusirhynchia) and a new smooth terebratulid genus (Praesphaeroidothyris). The palaeobiogeographic signature of these taxa has been analysed, revealing remarkable Mediterranean affinities. Thus, the previously restricted geographical distribution of these faunas can be extended to the westernmost Tethys areas, where the maximum degree of endemism is established for the brachiopod groups in the Subbetic domain around the Sinemurian-Pliensbachian transition.     

Brachiopod palaeobiogeography in the western Tethys during the Early Jurassic diversity maximum: introduction of a Pontic Province

The biogeography of Pliensbachian (Early Jurassic) brachiopods in western Tethys is investigated using complementary multivariate tools including metric and non-metric ordination, additive cluster and bootstrapped spanning network analyses, as well as one-way analysis of similarity and similarity percentage analysis. All analyses were conducted using the Dice and Simpson similarity indices for presence/absence data on occurrence datasets involving 24 assemblages homogenized at the species level, including (403 taxa) or excluding (210 taxa) species found in only one assemblage. The analyses present a highly consistent biogeographical picture involving three main clusters: the Euro-Boreal, Mediterranean and Pontic biochores. The brachiopod species typical of the newly defined Pontic biochore are illustrated. The three assemblages from the Atlas area are interpreted as a fourth biochore, compositionally intermediate between those of the Euro-Boreal and Mediterranean. The Mediterranean biochore can be further divided into an intra- and a peri-Mediterranean group. These five, palaeogeographically well-constrained biochores show moderate to high degrees of species endemicity, ranging from 20% (Atlas) to 58% (Euro-Boreal). Based on available evidence, and after a reasonable cutback of the customary scale of ranks, the following biogeographical categories and names are suggested for the western Tethyan Pliensbachian brachiopod biochores: Euro-Boreal Province, Mediterranean Province (including an intra-Mediterranean and a peri-Mediterranean Subprovince), Pontic Province and Atlas Subprovince. In addition, a still poorly documented brachiopod biochore occurs on the Gondwana margin as a possible precursor of the extensive Middle to Late Jurassic Ethiopian Province.     

Early Jurassic gastropods from England

Abstract: Twenty‐five gastropod taxa are reported from the Early Jurassic (Hettangian to Toarcian) of England. Of these, 14 are identified to species level, and the remaining 11 are treated in open nomenclature. One genus (Lensataphrus) and six species are introduced as new. The new species are Lensataphrus tatei, Lensataphrus tenuis, Tricarilda toddi, Cylindrobullina dorsetensis, Cylindrobullina ventricosa and Consobrinella greeni. The following new combinations are introduced: Cassianopsis hebertana (d’Orbigny, 1852) for Neritopsis hebertana; Cryptaulax abscisum (Terquem and Piette, 1868) for Cerithium abscisum; and Cylindrobullina avena (Terquem, 1855) for Striactaeonina avena. Most of the genera and some of the species are also known from Central Europe (Germany and France). Typical vetigastropod genera that are present in England and Central Europe are Colpomphalus, Costataphrus, Ooliticia, Eucycloscala and Eucycloidea. The caenogastropod genera Levipleura and Cryptaulax are present in both regions, as are the heterobranchs Tricarilda and Cylindrobullina. The heterobranch genus Consobrinella is reported from England for the first time. Gastropods seem to follow the diversity trends of other marine invertebrates during the Early Jurassic. They diversify until the Late Pliensbachian but decrease sharply in number around the Pliensbachian–Toarcian boundary. This may reflect both regional anoxia and a global mass extinction event in the Early Toarcian.     

Early Jurassic flora from South Primorye,Far East,Russia

A unique Early Jurassic flora from the Schitukhe Formation of South Primorye, Russia is further studied, with newly collected materials. The flora is composed of over 50 taxa. It is dominated by ferns (Dipteridaceae, Marattiaceae, etc.), cycads (Pterophyllum, Nilssonia, Ctenis, Taeniopteris, etc.), conifers (Cycadocarpidium, Podozamites, etc.), and other seasonally deciduous gymnosperms (Czekanowskiales, Ginkgoales, etc.), showing a special flora living in an ecotone zone between the Palaeofloristic realms of Siberian Flora and Euro-Sinian Flora in the East Asia during the early Early Jurassic. The flora is compared with its coeval floras from China and Japan. A new species Cycadocarpidium pacificum n. sp. is reported. The age of the Schitukhe flora is constrained by the marine mollusca fossils yielded in the sandwich marine beds of the Schitukhe Formation, as the Hettangian–Sinemurian.     

A new sauropodomorph ichnogenus from the Lower Jurassic of Sichuan,China fills a gap in the track record

A dinosaur tracksite in the Lower Jurassic Ziliujing Formation of Sichuan Province, China consists of a spectacular sub-vertical exposure, with multiple track-bearing levels and trackways showing parallel and bimodal orientations. Based on well-preserved material, the new ichnogenus and ichnospecies, Liujianpus shunan ichnogen. nov. ichnosp. nov. is erected to accommodate distinctive sauropodomorph trackways occurring in this assemblage. Liujianpus has a unique combination of features, some relating to the early Jurassic basal sauropodomorph (prosauropod in traditional usage) ichnogenus Otozoum, others to the sauropod ichnogenus Brontopodus. Despite such a mix of basal sauropodomorph- and sauropod-like features, the trackmaker of Liujianpus is likely a basal sauropodomorph. This identification is consistent with the occurrence of basal sauropodomorph skeletons from geographically and chronologically close localities. The other distinct morphotype from the tracksite is linked to a sauropod trackmaker. As such, the ichnofauna consisting of two distinct foot morphotypes reflects the diversity of sauropodomorph dinosaurs in the Early Jurassic of Asia.     

Tuberculate micro-ornament on the juvenile shell of Middle Jurassic ammonoids

In two genera of Callovian Ammonitina of distinct superfamilies, the juvenile shell displays a tuberculate micro-ornament in addition to growth lines. In contrast to the circular micro-tubercles of the ammonitella shell, post-embryonic tubercles are oval to longish in outline. They are arranged in rows running parallel to the growth lines in Kosmoceras (Spinikosmoceras) and cross the growth lines in Binatisphinctes.     

Brachiopod faunal exchange through an epioceanic-epicontinental transitional area from the Early Jurassic South Iberian platform system

The La Mola region (eastern External Betic Zone) can be regarded as one of the easternmost complete Jurassic successions of the Betic Cordillera in the Iberian Peninsula, but the paleogeographical setting of their outcrops remains widely discussed. Analysis of brachiopod assemblages from the Lower Jurassic improves the accuracy of previous paleogeographical data, enabling identification of a mainly epioceanic transitional area in which influences of epicontinental habitats are also detected. Assemblage 1, mainly with a Mediterranean affinity but also sharing several constituents with the African and Northeastern Iberian basins, typifies the Sinemurian–Pliensbachian transition. Assemblage 2, as a whole, shows a transitional character between epioceanic and epicontinental habitats; it is subdivided into two successive and interrelated sub-assemblages: Ass. 2a (Demonense–Tenuicostatum Zones) reveals a free connection with the epioceanic Subbetic area, whereas Ass. 2b (Uppermost Pliensbachian–Lower Toarcian) shows a closer relationship with epicontinental environments. Assemblage 3 (Uppermost Spinatum–basal Serpentinum Zones) is commonly recorded in the peri-Iberian epicontinental platform system integrated within the NW-European bioprovince, but it can also be regarded as a marginal assemblage that is widespread in the westernmost Tethyan margin prior to the Early Toarcian extinction event. Assemblage 2 constitutes a suitable index for assessing the paleobiogeographical affinity of the La Mola region, as Ass. 2a is progressively replaced by Ass. 2b, thus triggering the arrival of epicontinental taxa to the more intra-epioceanic Subbetic environments, inferring a possible connection through the La Mola transitional slope. Consequently, this region enabled a faunal mixing and exchange between both environments, and La Mola likely remained as an area that would facilitate migration and an effective dispersal seaway or, at least, did not constitute an ecological filter-barrier for brachiopods. Biostratigraphical data from brachiopods and ammonites are correlated for the first time in La Mola, refining and calibrating biochronostratigraphical gaps in the pre-Domerian deposits where biochronological markers are usually scarce, and around the Pliensbachian–Toarcian boundary, a crucial timespan in which the Early Toarcian extinction event took place.     

Vagorichnus,a new ichnogenus for feeding burrow systems and its occurrence as discrete and compound ichnotaxa in Jurassic lacustrine turbidites of Central China

A new ichnogenus, Vagorichnus, is figured and described from Jurassic lacustrine turbidites of the Anyao Formation, Henan Province, Central China. Vagorichnus consists of complex burrow systems composed of discontinuous curved to meandering segments in which irregular networks are formed. The ichnospecies V. anyao covers burrow systems characterized by constricted and irregularly annulated segments, and ridge‐like knobs. Although traces are preserved as hypichnial ridges on the sole of turbidite sandstones, several lines of evidence indicate that these ichnofossils record the activity of a post‐event infauna. Vagorichnus occurs as discrete and compound ichnotaxa. In the latter case, it grades into Gordia and Tuberculichnus. Vagorichnus is interpreted as invertebrate feeding structures (Fodinichnia).     

First record of Otozoum from Namibia

The first incontrovertible Otozoum moodii of Gondwana is described from the Etjo Formation (Waterberg Plateau, Namibia). Distinct Otozoum trackways and isolated footprints are reported from the Omuramba Omambonde tracksite, in the Otjozondjupa Region (North–central Namibia). Previously known only from North America, Europe and possibly Lesotho, the occurrence of Otozoum is a definitive time constraint for an Early Jurassic age of the Etjo Formation. The presence of Otozoum in the hyperarid facies and specifically in interdune setting of the Etjo Formation is in accordance with previous claims of environmental selectivity for this ichnomorph.