bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Late Triassic pterosaur from the Northern Calcareous Alps (Tyrol, Austria)
Authors: Wellnhofer Peter 
Published: April 2008

Abstract

Disarticulated skeletal remains of an eudimorphodontid pterosaur from the Late Triassic of the Karwendel Mountains in Tyrol, Austria, are described and figured. It is the second record of Triassic pterosaurs from the Northern Calcareous Alps, after previous discoveries in the Southern Calcareous Alps of northern Italy. The fossil material — isolated jaws, bones and fragmentary skeletal parts of one individual — was collected from the Norian Seefeld Beds (also called ‘Bitumenmergel’ or ‘Seefelder Fischschiefer’) near Seefeld in Tyrol. The fossiliferous formation of largely bituminous and calcareous layers originated on top of an extended marine carbonate platform, an equivalent to the nearly contemporaneous limestones and dolomites in the Southern Calcareous Alps, as exposed in Lombardy and Friuli in Italy, that has produced pterosaur fossils since 1973. Based on the biostratigraphic significance of conodont index fossils, the Seefeld Beds can be dated as Late Norian, most likely Sevatian. Sufficiently well-preserved skeletal elements include a jugal, isolated teeth, both mandibular rami with a dentition of uni-, tri- and pentacuspid teeth, cervical, dorsal and caudal vertebrae, ribs, sternum, scapulocoracoids, humerus, first wing phalanx, pelvis and tibia/fibula. There are morphological characters that support a subadult stage of the individual with an estimated wing span of 70–80 cm. The dentition is comparable to
Eudimorphodon ranzii
Zambelli from the Norian Calcare di Zorzino of Cene near Bergamo, northern Italy. However, some skeletal proportions and osteological features are distinctive from this taxon, as well as from a second species,
Eudimorphodon rosenfeldi
Dalla Vecchia from the Norian Dolomia di Forni of Friuli, northern Italy. The meaning of these differences in the Seefeld specimen, in particular the relatively long tibia and short wing phalanx 1, is discussed. The caudal zygapophyses and haemal arches are not elongated into the rod-like bony extensions significant for other known rhamphorhynchoid pterosaurs. It appears, however, that all speciments of
Eudimorphodon
lack elongated caudal zygapophyses. This might be evaluated as a primitive trait for these basal pterosaurs. The typical dentition permits the assignment of the Seefeld pterosaur to the genus
Eudimorphodon
. The fragmentary state of the skeleton and somewhat different skeletal proportions allow the author only to refer the specimen to
Eudimorphodon
cf.
ranzii
Zambelli 1973.
A new azhdarchid pterosaur from the Late Cretaceous phosphates of Morocco
Authors: Suberbiola Xabier Pereda , Bardet Nathalie , Jouve Stéphane , Iarochène Mohamed , Bouya Baâdi , Amaghzaz Mbarek 
Published: April 2008

Abstract

A large azhdarchid pterosaur is described from the Late Maastrichtian phosphatic deposits of the Oulad Abdoun Basin, near Khouribga (central Morocco). The material consists of five closely associated cervical vertebrae of a single individual. The mid-series neck vertebrae closely resemble those of azhdarchids
Quetzalcoatlus
and
Azhdarcho
in that they are elongate, with vestigial neural spines, prezygapophysial tubercles, a pair of ventral sulci near the prezygapophyses, and without pneumatic foramina on the lateral surfaces of the centra. The Moroccan pterosaur is referred to a new genus and species of Azhdarchidae:
Phosphatodraco mauritanicus
gen. et sp.nov. It is mainly characterized by a very long cervical vertebra eight, bearing a prominent neural spine located very posteriorly. Based on comparisons with azhdarchid vertebrae, the estimated wing span of
Phosphatodraco
is close to 5 m. This discovery provides the first occurrence of Late Cretaceous azhdarchids in northern Africa.
Phosphatodraco
is one of the few azhdarchids known from a relatively complete neck and one of the latest-known pterosaurs, approximately contemporaneous with
Quetzalcoatlus
.
Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania)
Authors: Buffetaut Eric , Grigorescu Dan , Csiki Zoltan 
Published: April 2008

Abstract

Pterosaur remains from the Late Cretaceous of the Haţeg Basin of western Romania were reported by Nopcsa as early as 1899. Recent discoveries from the Late Maastrichtian Densuş-Ciula Formation include the giant azhdarchid
Hatzegopteryx thambema
, the holotype of which, consisting of skull elements and a humerus from the VĂlioara locality, is described in detail. A very large femur from the same formation at Tuştea is also described. The systematic position of
Hatzegopteryx
is discussed. The wing span of
H. thambema
is estimated to be close to that of
Quetzalcoatlus northropi
(≥12 m), but its skull is especially robust and may have been remarkably long (≥ 2.5 m). The skull bones of
H. thambema
consist of a very thin outer cortex enclosing an inner meshwork of extremely thin trabeculae surrounding very numerous small alveoli, an unusual structure reminiscent of expanded polystyrene. This peculiar structure, combining strength with lightness, can probably be considered as an adaptation to flight in a very large animal, through reduction of skull weight.
The detailed anatomy of
Rhamphorhynchus
: axial pneumaticity and its implications
Authors: Bonde Niels , Christiansen Per 
Published: April 2008

Abstract

An acid- and transfer-prepared, juvenile
Rhamphorhynchus muensteri
, despite some fragmentation, is in an excellent state of three-dimensional preservation, exposing exquisite anatomical details hitherto unknown in other pterosaurs. Here we describe the axial pneumatizations of the cervical and anterior dorsal vertebrae and the sternum. The interior of the cervical centra is subdivided into a pair of large camerae, presumably by air sacs entering by large pleurocoels in the sides of the centra. This so-called ‘camerate’ type of pneumatization is hitherto unknown in pterosaurs. Another excavation enters from the ventral side into the base of the neural arch and stretches between the pre- and postzygapophyses. This type of cavity also penetrates from the ventral side into the base of the first few transverse processes of the dorsal vertebrae, although these lack central pleurocoels. The cristospine also has a complex pneumatic foramen.

Skeletal pneumaticity is most probably a result of a highly derived pulmonary system, as in extant birds. Morphologically similar pneumatic features are present in most saurischian dinosaurs and it is possible that they are the result of convergence. Because basal members of the various groups, including Triassic pterosaurs, appear to lack skeletal pneumaticity, convergence seems likely, although the stem-ornithodiran parsimoniously possessed a more bird-like than ‘reptile’-like pulmonary system, albeit non-invasive. This points to possible tachymetabolism in these forms, which is in accord with the distribution of other factors such as integumentary structures and bone histology. It is concluded that evolution of this suite of advanced features, surprisingly, was among the earliest events in the ornithodiran lineage soon after it split off from its crocodilian sister-group.
Pterosaur tracks from the latest Campanian Cerro del Pueblo Formation of southeastern Coahuila, Mexico
Authors: Rodriguez-de la Rosa Ruben A. 
Published: April 2008

Abstract

A new vertebrate tracksite in southeastern Coahuila, northern México, known as the El Pelillal tracksite (Latest Campanian, Cerro del Pueblo Formation) has yielded an important ichnofauna that includes the tracks of turtles, crocodilians, a small theropod dinosaur, a mammal-like organism and the tracks of pterosaurs. The pterosaurian manus impressions share an extraordinary similarity, in size and morphology, with the Jurassic ichnogenus
Pteraichnus
Stokes 1957 and are referred to
Pteraichnus
sp.; however, the pes impressions differ in that they are rather very elongated. According to the geological features and ichnofauna the El Pelillal tracksite represents a shallow, freshwater or lacustrine deposit, which agrees with our knowledge about the habitat preference of Cretaceous pterosaurs. This newly discovered tracksite in southeastern Coahuila, Mexico, offers great potential for palaeoichnological research and is thus becoming important in the understanding of the palaeoecosystems during the Late Cretaceous in southern North America.
The John Quekett sections and the earliest pterosaur histological studies
Authors: Steel Lorna 
Published: April 2008

Abstract
In 1855, John Quekett, assistant curator to Richard Owen of the Hunterian Museum in London, published a catalogue of the museum’s thin-section specimens. Among them were 15 sections of pterosaur bone. These sections were cut from eight bones found in the Lower Chalk of Kent, the Wealden of Sussex and the Stonesfield Slate of Oxfordshire, and are believed to be the first pterosaur bone thin sections to have been produced and described. Six of these thin sections survived the bombing of London during the Second World War, although the bones from which they were cut were destroyed. The sections were re-examined in early 2001 and photographed in plane and crossed polarized light for the first time. The histology of one thin section is inconsistent with a pterosaurian origin. This case highlights the value of bone palaeohistology as an aid in confirming the identity of incomplete remains.
Histovariability in bones of two pterodactyloid pterosaurs from the Santana Formation, Araripe Basin, Brazil: preliminary results
Authors: Sayão Juliana M. 
Published: April 2008

Abstract
Thin sections of pterosaur bones have not been extensively studied so far. Until now mainly isolated bones were the subject of this type of analysis. Here we present preliminary results of the histological analysis of two pterodactyloid pterosaurs from the Romualdo and Crato Members of the Santana Formation. The first specimen (Museu Nacional, MN 4809-V) comprises both wings (from humerus to the third phalanx of the fourth digit) and one hindlimb (tibia, fibula and pes). The second (MN 6527-V) consists of a partial skeleton with the incomplete left wing (humerus, radius, ulna, carpals, pteroid, wing metacarpal, two phalanges of the fourth digit) and fragments of one hindlimb (complete tibia and proximal articulation of the femur). Thin sections of the diaphyseal portion of each bone were ground in transverse, longitudinal and oblique orientation and the histological structures were compared. The following features can vary in the first observed specimen (MN 4809-V): presence of primary and secondary tissues in the cortex; absence or presence and position of lines of arrested growth; resorption of primary structures. These variations in different bones of the same individual represent differential growth rates. The second specimen (MN 6527-V) is well vascularized and has fibro-lamellar bone indicative of rapid growth in the thin section of the radius, ulna and first phalanx of the fourth digit. This last feature is very similar to the condition observed in most living birds.
Ophiolite pulses, mantle plumes and orogeny
Authors: Dilek Yildirim 
Published: April 2008

Abstract
Ophiolites show a wide range of internal structure, pseudostratigraphy and chemical fingerprints suggesting various tectonic settings of their origin. In general, they are characterized as mafic-ultramafic assemblages and associated sedimentary and metamorphic rock units that formed during different stages of the Wilson cycle evolution of ancient oceans, and that were subsequently incorporated into continental margins through collisional and/or accretionary orogenic events. Distributions of ophiolites with certain age groups in different orogenic belts define distinct ophiolite pulses, times of enhanced ophiolite genesis and emplacement, in Earth history. These pulses coincide with the timing of major collisional events during the assembly of supercontinents (i.e. Rodinia, Gondwana and Pangaea), dismantling of these supercontinents, and increased mantle plume activities that formed widespread large igneous provinces (LIPs). Suprasubduction zone ophiolites in orogenic belts signify oceanic crust generation in subduction rollback cycles during the closing stages of basins prior to terminal continental collisions. Both collision-driven assembly of supercontinents and deep penetration of subducted slabs into the lower mantle may produce plumes that in turn facilitate continental rifting, sea-floor spreading and oceanic plateau generation, all of which seem to have contributed to ophiolite genesis. Accelerated LIP formation and seafloor spreading that are associated with superplume events are likely to have caused widespread collisions and tectonic accretion of ophiolites at global scales. Together, these spatial and temporal relations suggest close links between ophiolite pulses, mantle plumes and orogenic events in Earth history.
Melt migration in ophiolitic peridotites: the message from Alpine-Apennine peridotites and implications for embryonic ocean basins
Authors: Müntener Othmar , Piccardo Giovanni B. 
Published: April 2008

Abstract
Results of a field study as well as petrological and geochemical data demonstrate that substantial portions of the lithospheric mantle, exhumed during opening of the Jurassic Piedmont Ligurian ocean, were infiltrated by and reacted with migrating melts. Intergranular flow of ascending liquids produced by the underlying hot asthenosphere dissolved clinopyroxene ± spinel and precipitated orthopyroxene + plagioclase ± olivine, forming orthopyroxene + plagioclase-rich perioditite. Migrating liquids became progressively saturated in clinopyroxene, and then precipitated microgranular aggregates of clinopyroxene-bearing gabbronorite. Later, diffuse porous melt flow was replaced by focused porous flow, producing a system of discordant dunite bodies. Upon cooling, liquids migrating in dunite channels became progressively saturated in clinopyroxene and plagioclase, forming interstitial clinopyroxene at olivine triple points followed by clinopyroxene ± plagioclase megacrysts and gabbro veinlets within the dunite, and gabbro dykelets within plagioclase peridotites. Subsequent cooling during continued exhumation was accompanied by intrusion of kilometre-scale gabbroic dykes evolving from troctolite to Mg-Al and Fe-Ti gabbros. Migrating liquids, which infiltrated peridotite and formed gabbroic rocks, span a wide range of compositions from silica-rich single melt fractions to T- and N-MORB (mid-ocean ridge basalt), characteristic of the melting column beneath midocean ridges. Explanations for the progressive evolution of an igneous system from diffuse to focused porous flow and finally dyking include the competing effects of heating of the lithospheric mantle by ascending magmas from the underlying hot asthenosphere and conductive cooling by exhumation. Whether or not rift-related melt infiltration and heating is recorded by exhumed subcontinental lithospheric mantle along ocean-continent transitions and/or oceanic lithospheric mantle along slow-spreading ridges depends on the relative position to the underlying upwelling asthenosphere.
Geochemical and geochronological constraints on the origin and emplacement of the Yarlung Zangbo ophiolites, Southern Tibet
Authors: Malpas John , Zhou Mei-Fu , Robinson Paul T. , Reynolds Peter H. 
Published: April 2008

Abstract
The Indus-Yarlung Zangbo suture zone in southern Tibet marks the Eocene collision of the Indian continent and the Lhasa Block of Eurasia. It is characterized, particularly in its central portion, by an east-west belt of ophiolitic and related oceanic volcanic and sedimentary rocks that form a number of structurally juxtaposed geological terranes. Although tectonically disrupted in many places, almost complete ophiolite sequences exist at Luobusa and Zedong in the east and near Xigaze in the west. In Luobusa, the ophiolite sequence is thrust over the Tertiary molasse deposits of the Luobusa Formation or onto plutonic rocks of the Gangdese batholith. A mantle sequence dominates the ophiolite massif and consists chiefly of harzburgite and clinopyroxene-bearing harzburgite with abundant podiform chromitites enveloped by dunite. The Luobusa ophiolite formed the basement to an intra-oceanic volcanic arc, the Zedong terrane, which developed between the Mid-Jurassic and Mid-Cretaceous. Farther to the west, complete ophiolite sequences exist at Dazhuqu and near Xigaze. These ophiolites have suprasubduction zone geochemical signatures but there is no apparent development of a volcanic arc. Sensitive high-resolution ion microprobe U-Pb zircon analyses yield an age of 126 Ma for the crystallization of a quartz diorite from the Dazhuqu massif. Amphibolites that occur as large blocks in mélanges at the base of the ophiolites are considered to be remnants of dynamothermal metamorphic soles produced early in the ophiolite obduction process. Ar/Ar geochronology on amphibole and biotite separates from these rocks yields ages of 80 and 90 Ma, respectively, for this event, which is considered to have occurred as the Indian continental margin entered the intra-oceanic subduction zone. Continued northward subduction of the remaining portion of the Neo-Tethyan ocean floor beneath the southern margin of Eurasia produced the Gangdese continental arc on the southern margin of the Lhasa Block and led to the final closure of the ocean with the collision of India and Eurasia in the Eocene.
Ophiolites and global geochemical cycles: implications for the isotopic evolution of seawater
Authors: Gregory R. T. 
Published: April 2008

Abstract
Isotopic profiles through ophiolite complexes provide the necessary link between the study of global geochemical cycles and plate tectonics. The hydrothermal circulation that occurs beneath the sea floor is the primary mechanism for exchange between the mantle of the Earth and the hydrosphere. The subduction of the hydrothermally altered crust and overlying sediments is the primary mechanism for crustal recycling. Oxygen and strontium isotopes of seawater track the competition between continental weathering and mid-ocean ridge hydrothermal exchange to control the composition of the oceans. Information derived from ophiolite studies on the elemental fluxes and the depth of seawater penetration into the oceanic crust provides constraints on the important rate constants associated with these competing processes. The same tectonic rates that account for the Sr isotope evolution of seawater indicate that the oxygen isotopic composition of the ocean is constrained to vary within narrow limits (per mil level). Isotopic analysis of dredge samples and ophiolite complexes demonstrates that seawater-ocean crust interactions result in a oxygen isotopic zonation of the oceanic crust with masses (concentration times volume) centred on the initial isotopic composition of the crust. This requires that the oxygen isotopic composition of the ocean resides at near steady-state conditions over Earth history. The inferences from ophiolite complexes contrast strongly with the results of measurements on carbonates from epicontinental seaways, particularly for the Palaeozoic. Ophiolites and greenstone belts track exchange processes between the ocean and the igneous crust whereas most carbonate measurements track the surface ocean on continental shelves. For oxygen isotopes, the mass of epicontinental seaways and the rates of meteoric water input suggest a resolution to the controversy that accounts for both data sets.
Hydrothermal circulation and metamorphism in crustal gabbroic rocks of the Bay of Islands ophiolite complex, Newfoundland, Canada: evidence from mineral and oxygen isotope geochemistry
Authors: Giguère E. , Hébert R. , Beaudoin G. , Bédard J. H. , Berclaz A. 
Published: April 2008

Abstract

The gabbroic crust of the Ordovician Bay of Islands ophiolite complex formed in an island-arc setting near the North American continental margin. Detailed structural studies on the North Arm Mountain massif provide us with a scheme of syn-oceanic deformation events recorded in the crust. During a first transtensional stage, which generated gabbroic rocks, sheeted dykes and lavas, the temperature of formation of amphiboles in the gabbroic unit fell with time in three steps from 880–745 °C, to 790–680 °C and to 550–500 °C. The Ti, Na and Al
IV
contents of amphiboles decreased, whereas the Si activity of the fluid increased with time. The first amphibole to form has typical mid-ocean ridge basalt δ
18
O
VSMOW
indicating equilibration with a magmatic fluid or evolved seawater at low fluid/rock ratio. Lower δ
18
O values for some amphiboles (0–2.5‰) indicate the circulation of large volumes of seawater. The lowest δ
18
O values are found in the inner part of the shear zones, which channelled deep infiltration of seawater into the gabbroic unit. During brittle deformation, infiltration of low-temperature seawater produced prehnite, carbonate and quartz veins, and plagioclase with high δ
18
O. This study documents that the hydration of ophiolitic crust in the Bay of Islands ophiolitic complex occurred mainly along pre-obduction oceanic structures in an intraoceanic setting.
Ophiolites as faithful records of the oxygen isotope ratio of ancient seawater: the Solund-Stavfjord Ophiolite Complex as a Late Ordovician example
Authors: Muehlenbachs Karlis , Furnes Harald , Fonneland Hege C. , Hellevang Bjarte 
Published: April 2008

Abstract

Fragments of the Ordovician sea floor preserved in the Solund-Stavfjord Ophiolite Complex in Western Norway serve as proxies for the δ
18
O of Ordovician seawater. The pillow basalt sections at Oldra and Strand are both enriched in
18
O, recording their alteration by seawater at low temperature on the sea floor. In contrast, the sheeted dykes and gabbros generally are depleted of
18
O, reflecting the modal proportion of secondary, low-
18
O chlorite and epidote formed from seawater at high temperature. These isotopic contrasts simply reflect the high water to rock ratio of sea-floor alteration and the temperature dependence of the
18
O partitioning between minerals and water. Superposition of high-δ
18
O pillows on low-δ
18
O dykes and gabbros is a necessary consequence of alteration at both low and high temperatures by a fluid near 0‰ and is easily recognized in well-preserved ophiolites. Also, the δ
18
O of seawater can be independently calculated from
18
O fractionations among secondary minerals. Older, dismembered and highly metamorphosed segments of the oceanic crust may still retain the original seawater imprint because their subsequent obduction and metamorphism was relatively closed to external fluids. Suites of diamond-bearing nodules from kimberlites still have contrasting high- and low-δ
18
O eclogites, proving that even subduction into the mantle is not sufficient to erase the seawater fingerprint. Inspection of the sea-floor, ophiolite and eclogite data reveals no secular trend in δ
18
O, indicating that the δ
18
O of seawater has not changed with geological age. Because the δ
18
O of seawater itself is fixed by sea-floor-seawater exchange, the constancy of δ
18
O of seawater implies that the scale and style of sea-floor-seawater interactions has not changed over time.