Tethyan Area Research Articles

Extreme Planktic Foraminiferal Dwarfism Across the ETM2 in the Tethys Realm in Response to Warming

AbstractPronounced warming negatively impacts ecosystem resilience in modern oceans. To offer a long‐term geological perspective of the calcareous plankton response to global warming, we present an integrated record, from two Tethyan sections (northeastern Italy), of the planktic foraminiferal and calcareous nannofossil response to the Eocene Thermal Maximum 2 hyperthermal (ETM2, ∼54 Ma). Our study reveals pronounced changes in assemblage composition and a striking dwarfing of planktic foraminiferal tests of up to 40% during the event, impacting both surface and deeper dwellers. The increased abundance of small placoliths among calcareous nannofossils is interpreted as community size reduction. Literature and our foraminiferal size data from Sites 1263 and 1209 (Atlantic and Pacific Oceans) highlights that the pronounced dwarfism is restricted to the Tethyan area. The ETM2 is characterized by warm sea surface temperatures as indicated by our δ18O data, but this warming is of global extent and cannot explain the unique dwarfism. Excluding evolutionary modifications, other potential drivers of dwarfism (eutrophication, deoxygenation, metabolic adaptation) cannot explain the exceptional dwarfism by themselves. The smallest sizes are in close temporal association with peaks in volcanic derived Hg/Th‐Hg/Rb recorded just before and at the ETM2 which could not have been brought into our sections through weathering. In contrast, size reductions are absent below and above the ETM2 at Hg peaks where δ18O data do not show warm conditions. We speculate that the local input of toxic metals from submarine volcanic emissions could have acted synergistically to warming, causing the unique dwarfism.

Central Asia revealed as a key area in evolution of Eremurus (Asphodelaceae)

Eremurus was described at the beginning of the 19th century. However, due to limited sampling and the small number of gene markers to date, its phylogeny and evolution are largely unknown. In this study, we analyzed plastomes from 27 species belonging to 2 subgenera and 3 sections of Eremurus, which are found in Central Asia (its center of diversity) and China. We also analyzed nuclear DNA ITS of 33 species, encompassing all subgenera and sections of the genus in Central Asia, southwest Asia and China. Our findings revealed that the genus was monophyletic, although both subgenera Eremurus and Henningia were found to be paraphyletic. Both plastome and nrDNA-based phylogenetic trees had three clades that did not reflect the current taxonomy of the genus. Our biogeographical and time-calibrated trees suggest that Eremurus originated in the ancient Tethyan area in the second half of the Eocene. Diversification of Eremurus occurred from the early Oligocene to the late Miocene. Paratethys Sea retreat and several orogenetic events, such as the progressive uplift of the Qinghai-Tibet Plateau and surrounding mountain belts (Altai, Pamir, Tian Shan), caused serious topographic and climate (aridification) changes in Central Asia that may have triggered a split of clades and speciation. In this transformed Central Asia, speciation proceeded rapidly driven mainly by vicariance caused by numerous mountain chains and specialization to a variety of climatic, topographic and soil conditions that exist in this region.

The Permian and Triassic history of the ostracod genus Liuzhinia

The ostracod genus Liuzhinia has been reported from Permian and Triassic marine deposits mainly from the Tethyan area but its classification and history remain obscure. Here we report on the discovery of a rare steinkern of Liuzhinia antalyaensis from the Early Triassic of South China bearing the first known adductor muscle scars, allowing for first insights into its supra-generic classification. We demonstrate that Liuzhinia does not belong to Bairdiidae and propose that the observed muscle scars could illustrate ancestral characters of Paracyprididae or Bythocyprididae. We summarize the diversity of Liuzhinia through time, including the newly described Liuzhinia phetchabunensis Forel & Chitnarin sp. nov. from the Middle Permian of central Thailand, and discuss its geographical distribution and environmental preferences over its stratigraphical range.

Petrography and Geochemistry of the Leucocratic Rocks in the Ophiolites from the Pollino Massif (Southern Italy)

In the Tethyan realm, leucocratic rocks were recognized as dikes and layers outcropping in the ophiolitic rocks of the Western Alps, in Corsica, and in the Northern Apennines. Several authors have suggested that the origin of leucocratic rocks is associated with partial melting of cumulate gabbro. Major and trace elements composition and paragenesis provided information about the leucocratic rocks genetic processes. This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. Plagioclase fractionation reflects negative Eu anomalies indicating its derivation from gabbroic crystal mushes. The chondrite normalized REEs patterns suggest the participation of partial melts derived from a metasomatized mantle in a subduction environment. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps. These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution.

Notes on Ditomina, with description of two new genera and a new species (Coleoptera, Carabidae) from the Middle East and India.

Two new monotypical genera of the subtribe Ditomina are described: Parapenthus gen. n. for Ditomus solitarius Peyron, 1858 from the Middle East, which was treated previously either within Penthus Chaudoir, 1843 or within Penthophonus Reitter, 1900, and Indocarterus gen. n. for I. inexspectatus sp. n. from the west of the Indian state of Maharashtra (type locality: Wai env., 70 km S of Pune). The possible genesis of Indocarterus gen. n. is discussed because it is the single genus of the subtribe distributed in the Oriental (Indo-Malayan) region in isolation from the other Ditomina which all occur in the West Palaearctic. It is assumed that the ancestor of this genus was isolated in the Indian Peninsula from the Tethyan area probably during the early stages of the diversification of Ditomina. In addition, the enigmatic genus Proditomus Schauberger, 1934 and its single species, P. mirus Schauberger, 1934, known only from the female holotype, are re-described and illustrated. Setation of the parameres and medial lobe in Ditomina is described for the first time. Previously, setae on the aedeagus of Carabidae, mostly on the parameres, were observed only in many basal lineages and, as exception, within Harpalinae, in some Lebiini and Panagaeini. A key to the genera and subgenera of Ditomina is provided.

Synchronization of the astronomical time scales in the Early Toarcian: A link between anoxia, carbon-cycle perturbation, mass extinction and volcanism

The Late Pliensbachian–Early Toarcian is a pivotal time in the Mesozoic era, marked by pronounced carbon-isotope excursions, biotic crises and major climatic and oceanographic changes. Here we present new high-resolution carbon-isotope and magnetic-susceptibility measurements from an expanded hemipelagic Late Pliensbachian–Early Toarcian section from the Middle Atlas Basin (Morocco). Our new astronomical calibration allows the construction of an orbital time scale based on the 100-kyr eccentricity cycle. The Early Toarcian Polymorphum Zone contains 10 to 10.5 repetitions of the 100-kyr eccentricity both in the carbon-isotope and the magnetic-susceptibility data, leading to an average duration of 1.00±0.08 myr. We also show that the Late Pliensbachian–Early Toarcian global carbon-cycle perturbation has an average duration of 0.24±0.02 myr. These durations are comparable to previous astrochronological time scales provided for this time interval in the most complete sections of the Tethyan area, and longer than what has been provided in condensed sections. Anchoring this framework on published radiometric ages and astrochronological time scales, we estimate that the carbon-cycle perturbation of the Late Pliensbachian–Early Toarcian corresponds with the early phase of the Karoo and Chonke Aike large igneous provinces. Likewise, our new age constraints confirm that the Toarcian oceanic anoxic event is synchronous to the main phase of the Ferrar volcanic activity. Thus, these successive and short phases of the volcanic activity may have been at the origin of the successive phases of the mass extinctions observed in marine biotas in the Pliensbachian and Toarcian times.

Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

ABSTRACTThis article presents a geological map and cross-sections at 1:50,000 scale covering an area of 609 km2 of the Eastern Prebetic Zone (SE Iberia). The structure of the studied area is characterized by an NW-directed fold-and-thrust belt and inactive salt diapirs that are parallel to the ENE- to NE-regional trend of the eastern Betic Cordillera. This regional trend is locally disrupted by the NW-trending Matamoros Basin, which is flanked by the active Jumilla and La Rosa diapirs. The geological map, the cross-sections and the outcrop observations support the hypothesis that the major Mesozoic rifting phase affecting the Eastern Prebetic Zone occurred during the Upper Jurassic to Santonian times coeval to the development of extensional basins in the Western Tethyan area. The proximal part of this passive margin was subsequently incorporated into the external part of the Betic thin-skinned fold-and-thrust belt. The Upper Cretaceous to Cenozoic tectonic evolution of the study area encompassed the following stages: a Campanian to Aquitanian NW-directed contraction; a Burdigalian to upper Miocene extensional reactivation of the main subsalt faults; and a Serravallian NW-directed contractional reactivation. In this scenario, the combined effect of the previous contractional reactivation of pre-existing salt structures together with the Miocene subsalt extension triggered passive salt extrusion of the La Rosa and Jumilla diapirs.

Role of the Qinghai-Tibetan Plateau uplift in the Northern Hemisphere disjunction: evidence from two herbaceous genera of Rubiaceae

To assess the role of the Qinghai-Tibetan Plateau uplift in shaping the intercontinental disjunction in Northern Hemisphere, we analyzed the origin and diversification within a geological timeframe for two relict herbaceous genera, Theligonum and Kelloggia (Rubiaceae). Phylogenetic relationships within and between Theligonum and Kelloggia as well as their relatives were inferred using five chloroplast markers with parsimony, Bayesian and maximum-likelihood approaches. Migration routes and evolution of these taxa were reconstructed using Bayesian relaxed molecular clock and ancestral area reconstruction. Our results suggest the monophyly of each Theligonum and Kelloggia. Eastern Asian and North American species of Kelloggia diverged at ca.18.52 Mya and the Mediterranean species of Theligonum diverged from eastern Asian taxa at ca.13.73 Mya. Both Kelloggia and Theligonum are Tethyan flora relicts, and their ancestors might have been occurred in warm tropical to subtropical environments along the Tethys coast. The Qinghai-Tibetan Plateau separated the eastern and western Tethyan area may contribute significantly to the disjunct distributions of Theligonum, and the North Atlantic migration appears to be the most likely pathway of expansion of Kelloggia to North America. Our results highlight the importance role of the QTP uplift together with corresponding geological and climatic events in shaping biodiversity and biogeographic distribution in the Northern Hemisphere.

Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary)

The Valanginian positive carbon isotope excursion and associated environmental changes, known as the Weissert Event, is the first in the series of Cretaceous Earth system perturbations. Here, we develop a multiproxy cyclostratigraphy from a 31.2-m-thick Upper Valanginian to lowermost Hauterivian section of the Bersek Marl Formation in Gerecse Mountains, Hungary, comprising alternating marlstone layers of varying clay and carbonate content. The bulk carbonate δ13C signal shows sustained, elevated values (up to 2.7‰) up to 19.2 m, followed by a decreasing trend upsection. Together with biostratigraphic data, this suggests that the lower part of the section was deposited during the plateau phase of the Late Valanginian Weissert Event. Spectral analyses of the multiproxy dataset, including magnetic susceptibility measurements and gamma-ray spectroscopy on the lower part of the section, led to the identification of precession, obliquity, and long and short eccentricity signals. A mean sedimentation rate of 14 m/Myr was calculated based on astronomical tuning. The cyclicity in the proxy signals reflects dilution cycles induced by the fluctuating rate of detrital runoff into the basin. This supports the idea that orbitally-forced humid-arid cycles controlled the pelagic alternating sedimentation during the Early Cretaceous throughout the Tethyan area.

TAXONOMIC AND BIOSTRATIGRAPHIC REASSESSMENT OFLITUOSEPTA RECOARENSISCATI, 1959 (FORAMINIFERA, LITUOLACEA)

The large lituolid foraminifer, Lituosepta recoarensis Cati, 1959, is recorded from Lower Jurassic shallow-water carbonate deposits of the Southern Tethyan area. This species is usually not abundant and its taxonomic status, as well as its stratigraphic distribution, have not always been well defined. The analysis of Cati’s stratigraphic section (Monti Lessini area, Monte Scandolara, north-eastern Italy, Southern Alps), from which the type material originates, yielded numerous well-preserved topotypes and permitted a detailed structural and morphological assessment of Lituosepta recoarensis . Microspheric and megalospheric generations are herein described and illustrated. Two generations of megalospheric forms, A1 and A2, are distinguished on the basis of morphological features. Comparing the Lituosepta species, the genus Planisepta (type species Lituosepta compressa Hottinger) is considered invalid and the original nomenclature Lituosepta compressa is retained. In the southern Tethyan margin the stratigraphic occurrence of L. recoarensis spans the upper Sinemurian–Toarcian interval.

Toarcian extreme warmth led to tropical cyclone intensification

Models predict that tropical cyclone intensity should increase on a warming planet. Observing this relationship remains, however, a difficult task since no clear trend is yet emerging from the anthropogenic record. The geological past offers the opportunity to study this relationship by looking at episodes of extreme warmth, such as the Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic, ca. 181 Ma). In this study, we document an increase in the occurrence of storm-related deposits during the onset of the T-OAE in the tide-dominated High Atlas Basin of Morocco, associated with a drastic deepening of the mean storm weather wave base. The palaeolatitude of the High Atlas Basin (18° North during the Early Jurassic) rules out winter storms as the driving mechanism behind the formation of these deposits and points to a dramatic intensification of tropical cyclone intensity during the T-OAE global warming. These new results, combined with the previously reported ubiquitous appearance of storm deposits during the T-OAE in tropical seas of the western Tethyan area, support the concept that the globally averaged intensity of tropical cyclones will increase in the coming century due to the anthropogenic climate change.

Palaeoclimate and palaeoenvironmental changes through the onset of the Valanginian carbon–isotope excursion: Evidence from the Polish Basin

Abstract The Valanginian Weissert episode of environmental change is associated with a positive carbon–isotope excursion (CIE) in δ13Ccarb and δ13Corg records and a crisis in pelagic and neritic carbonate production. The CIE was interpreted to represent the first oceanic anoxic event (OAE) of the Cretaceous, linked with the formation of the Parana–Etendeka large igneous province (LIP). Recent studies suggest though that the extent of oceanic anoxia was limited to high-latitude epicontinental seas and the Pacific, and that the Parana–Etendeka LIP postdates the Valanginian CIE. With these new interpretations, the palaeoenvironmental changes behind the observed perturbation of the carbon cycle remain to be elucidated. Here we present sedimentological and geochemical results from a drill core near Wąwal, central Poland. The excavated succession is of particular interest due to its near-shore depositional setting within the former Polish Basin and its preservation (up to 17 wt.% of aragonite). The core consists of lower to upper Valanginian silty to sandy clays deposited under fully marine conditions on top of an Upper Jurassic karstified limestone. A change in weathering mode from very humid and highly hydrolysing towards less humid and seasonally contrasted conditions is indicated by the abrupt change from a kaolinite- to a smectite-dominated clay-mineral association near the boundary between the early and late Valanginian. Moreover, two phosphate-rich horizons were identified, which correlate in time to northern Tethyan occurrences in the Helvetic Alps. The lower level is associated with the early Valanginian transgression and corresponds to peak humidity recorded in the Wąwal core. The upper layer corresponds to the paroxysmal phase of the Valanginian crisis in carbonate production. In the Wąwal core, evidence for anoxic conditions during the Valanginian CIE is lacking. The climatic conditions and changes identified in the Polish Basin are different from those of the northern Tethyan area, where an increase in humidity is observed near the early–late Valanginian boundary. The contrasting climate conditions are probably an expression of latitudinal shifts in the position of the northern mid-latitude humid belt.

Remarks on the identification of the Albian/Cenomanian boundary and taxonomic clarification of the planktonic foraminifera index speciesglobotruncanoides, brotzeniandtehamaensis

AbstractThe planktonic foraminifera assemblage across the Global Boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage defined at Mont Risou (Haute-Alpes in France) is here restudied to clarify the identification and stratigraphic distribution ofThalmanninella globotruncanoides( =Rotalipora globotruncanoidesSigal, 1948) andPseudothalmanninella tehamaensis( =Rotalipora tehamaensisMarianos & Zingula, 1966) whose appearance levels are primary and secondary criteria for placing the Albian/Cenomanian boundary. Since the ratification of the GSSP in 2002, the identification of the foraminifera index species across the Albian/Cenomanian boundary has been reported to be sometimes difficult either because of their rarity or uncertainty in the taxonomic identifications. We discuss the taxonomic status ofThalmanninella brotzeniSigal 1948, a species regarded for a long time to be a junior synonym ofTh. globotruncanoides, through images of Sigal's type materials deposited at the Musée National d’Histoire Naturelle (Paris), and elucidate the taxonomically important characters that enable unequivocal identification ofTh. brotzeni, Th. globotruncanoidesandPs. tehamaensis. Planktonic foraminifera marker species from Mont Risou are compared with well-preserved specimens from Blake Nose Plateau (ODP 171B, North Western Atlantic Ocean) to verify the reliability and stratigraphic distribution of these marker taxa outside the Mediterranean Tethyan area.

Maastrichtian monocotyledons of the Rusca Montană and Haţeg basins, South Carpathians, Romania

The Upper Cretaceous (Maastrichtian) formations of the Rusca Montană and Haţeg basins (Romania) yield a compressive fossil flora including the genera Sabalites and Pandanites. The Rusca Montană and Haţeg basins represent very important areas for Cretaceous palms, due to the remarkable density of foliar material and to their palaeogeographic significance for the Tethyan area. Sabalites longirhachis (Unger) J. Kvaček et Herman 2004, collected from the Haţeg and Poiana Ruscă basins, is described, discussed and figured, together with Pandanites trinervis (Ettingshausen) J. Kvaček et Herman 2004 (including here Romanian material formerly attributed to Pandanites austriacus, Pandanites acutidens and Pandanites romanicus Petrescu et Duşa 1970), while Pandanites spinatissimus Petrescu et Duşa sp. nov. (including here Pandanus tenuissimus Petrescu et Duşa 1982 nom. inval. and Pandanus barbui Petrescu et Duşa 1982 nom. inval.) is validated, emended and illustrated. These monocot taxa offer new and relevant insights into the palaeobiogeography and palaeoecology of the latest Cretaceous floras of Europe.

Maroccosuchus zennaroi (Crocodylia: Tomistominae) from the Eocene of Morocco: phylogenetic and palaeobiogeographical implications of the basalmost tomistomine

Maroccosuchus zennaroi Jonet & Wouters, 1977 from the Ypresian of the Oulad Abdoun Basin (Morocco) is described in detail based on numerous and well-preserved specimens. A phylogenetic analysis including 64 ingroup taxa and 238 characters reveals that M. zennaroi is the basalmost tomistomine. This clade is supported by 10 unambiguous synapomorphies, while only two – both related to the snout shape and observed in gavialoids – support a closer relationship between Kentisuchus spenceri and later tomistomines. Their absence in M. zennaroi could reflect its intermediate morphology between basal crocodyloids and longirostrine tomistomines. This clearly indicates a Lower Eocene, and no older than Late Palaeocene age for the tomistomine emergence, questioning the Late Eocene, Oligocene and Miocene ages proposed for Gavialis–Tomistoma divergence by molecular analyses. Considering this analysis, the biogeographical history of the tomistomines is evaluated. This history begins in western Tethys during the Lower Eocene or latest Palaeocene, with M. zennaroi followed by several West European tomistomines. The Tethys becomes the centre of dispersal to North America, Africa and Asia. The phylogenetic analysis also suggests at least two independent dispersals from the Tethyan area to Asia, with the extant Tomistoma schlegelii more closely related to European Miocene forms in the first instance, and Toyotamaphimeya machikanense and Penghusuchus pani more closely related to the North American Thecachampsa in the second instance. However, the small number of remains from the Oligocene and Late Eocene does not allow a clear date of divergence and dispersal routes to be ascertained.

Latitudinal variation of brachiopod ornamentation in the Jurassic faunas from the western Tethys and its possible relation to a predation gradient

In modern seas shell ornamentation becomes stronger towards the equator as a response to the increasing predation and a similar relationship was recorded in the case of mid-Palaeozoic brachiopods. It is expected that similar trends and relationship existed in the Jurassic, in the time of the Mesozoic Marine Revolution. The paper describes the latitudinal variation of brachiopod ornamentation in the western part of the Jurassic Tethys and neighbouring epicontinental areas and discusses their relationships to a possible predation gradient. The database included 29 localities (Pliensbachian, Bajocian, Callovian, and Tithonian/Volgian) covering the western Tethyan area from the palaeolatitudes 45° N to 10° S. In the Jurassic western Tethys, the brachiopod ornament was apparently the strongest in the high palaeolatitudes (45° N); decreased in the mid-latitudes and reached high values again near the equator. Considering the anti-predatory function of ornament, and other alternative hypotheses, the present study suggests that in the Jurassic the predation gradient was partly opposite to that of the Palaeozoic. The distribution of two main types of ornament showed opposite trends: spinosity was confined to higher palaeolatitudes whereas ribbing was stronger near the equator. This bipolarity is tentatively interpreted as adaptations to different types of predation; ribbing was a possible tool against durophages, whereas spinosity is supposed to hinder drilling predators.

Paleo movement of continents since 300 Ma, mantle dynamics and large wander of the rotational pole

Apparent polar wander (APW) is known to be mainly linked to internal mass distribution changes and in particular to changes in subduction and large-scale upwellings in the mantle. We investigate plate motions during the last 410 million years in a reference frame where Africa is fixed. Indeed, Africa has remained a central plate from which most continents diverged since the break-up of Pangea. The exact amount of subduction is unknown prior to 120Ma. We propose an approach, based on one hand on the study of the past subduction volcanism to locate ancient subduction activity, and on the other hand microplate motion history in the Tethyan area derived from geology and paleomagnetism. The peri-Pacific subductions seem to be a quasi-permanent feature of the Earth's history at least since the Paleozoic, with however localized interruptions. The “Tethyan” subductions have a complex history with successive collisions of continental blocs (Hercynian, Indo-Sinian, Alpine and Himalayan) and episodical rebirth of E–W subduction trending zones. Assuming that subducted slabs sink vertically into the mantle and taking into account large-scale upwellings derived from present-day tomography and intra-plate volcanism in the past, we compute the time variation of mantle density heterogeneities since 280Ma. Due to conservation of the angular momentum of the Earth, the temporal evolution of the rotational axis is computed in a mantle reference frame where the Africa plate is fixed, and compared to the apparent polar wander (APW) observed by paleomagnetism since 280Ma. We find that a major trend of both paleomagnetic and computed APW are successive oscillatory clockwise or counter-clockwise motions, with tracks separated by abrupt cusps (around 230Ma, 190Ma and 140–110Ma). We find that cusps result from earlier major geodynamic events: the 230Ma cusp is related to the end of active subduction due to the closure of the Rheic Ocean basin after the Hercynian continental collision (340–300Ma) and to renewed subduction zone West of Laurentia, whereas the 190Ma cusp results from the Indo-Sinian collision (270–230Ma) and the subsequent end of the Neo-Tethys ocean subduction.

Critical review of Pseudocucurbitidae (Miliolina, Foraminiferea) from the Late Triassic reef environments of the Tethyan area

Abstract. The Late Triassic foraminiferal genera Amphorella, Spiriamphorella, Urnulinella, Pseudocucurbita, Paratintinnina, Costifera and Siculocosta are considered junior synonyms of the genus Cucurbita. Consequently, the number of families of the Milioliporacea (Miliolina) is significantly reduced. The valid species of the genus Cucurbita are considered to be Cucurbita infundibuliforme Jablonský, 1973, C. subsphaerica (Borza & Samuel, 1977a) comb. nov., C. longicollum Senowbari-Daryan, 1983, C. battagliensis (Senowbari-Daryan, 1983) comb. nov., C. cylindrica (Senowbari-Daryan, 1983) comb. nov. and C. floriformis (Altiner et al., 1992) comb. nov..

Lower Cretaceous ammonites from the Neuquén Basin, Argentina: The Hauterivian genus Spitidiscus

Spitidiscus is a widely-distributed Hauterivian genus that briefly invaded the Neuquén Basin, Argentina, in mid Hauterivian times, well after it first evolved in the west Tethyan area. Its appearance in Argentina is linked with a globally-significant mid Hauterivian sea-level rise. This is marked in the basin by a sharp facies change in the Agrio Formation, from non-marine sandstones of the Avilé Member to marine sediments, often laminated black shales, with Spitidiscus at the base of the overlying Agua de la Mula Member. Our extensive field work has shown that Spitidiscus occurs across the whole basin, where it is represented by two species, Spitidiscus riccardii Leanza and Wiedmann and Spitidiscus kilapiae sp. nov. For most of its vertical range Spitidiscus occurs alone, characterising the S. riccardii Zone. But at the top of its range it is joined by the first crioceratitid ammonites, their appearance marking the base of the Crioceratites schlagintweiti Zone.

The evolution and biogeography of alpine species in Ranunculus (Ranunculaceae): A global comparison

AbstractThe origin and evolution of alpine floras potentially can be shaped by immigration via long‐distance dispersal or migration over mountain chains. Alternatively, origins of alpine species may be referred to regional speciation via origins from lowland ancestors and adaptation to high altitudes. Moreover, evolutionary histories of alpine species have also been influenced by Quaternary glaciations. Range fluctuations due to climatic oscillations have caused vicariant speciation and secondary con‐ tact hybridization. However, comparative phylogenetic studies on alpine floras from mountain systems of different continents are scarce. Here we review the phylogenetic relationships of alpine species of Ranunculus, an almost cosmopolitan genus with alpine representatives in all major mountain systems of the world. Based on molecular phylogenetic analysis of 245 alpine and lowland species (based on a combined dataset of ITS, matK, trnK and psbJ‐petA sequences), we try to elucidate origins of alpine buttercups. Results suggest that most major mountain systems (European Alpine System, Irano‐Turanian mountains, Himalayas, Central Asian mountains, African mountains, and Andes) have been colonized multiple times independently; only the North American alpine species fall all into one clade. In the European and Irano‐Turanian mountains, recruitment of alpine species from lower altitudes of the same area, and migration within the Tethyan area might have played a major role. The alpine species of the Himalayas, the Central Asian mountains, the North American alpine species and the Arctic species fall into another, distinct clade, which may suggest a northern migration route. The North American alpine clade comprises many lowland species and might have diversified via adaptive radiation. In contrast, the Himalayan species have no lowland source flora and might have originated from immigrants of the Central Asian mountains. Tropical alpine Ranunculi in the mountains of Eastern Africa and in Taiwan have originated after long‐distance dispersal from other continents. The origin of the New Zealand alpines could have been referred to long‐distance dispersal, probably following southern migration routes via the Antarctic and South America. The Andes have been colonized multiple times by related genera of Ranunculus. We conclude that autochthonous origins and regional diversification of buttercups play a major role in northern hemispheric mountain systems, where alpine species could have evolved from rich lowland source floras. In subtropical to tropical mountain systems, and in the Southern Hemisphere, alpine species have been rather recruited via immigration, including long‐distance dispersal from other continents. A high adaptive potential of Ranunculus to alpine habitats might have helped to evolve alpine species all over the world.