The Paleoclimate and Enviroment of Early Cretaceous Sichuan Basin, China

Lower Cretaceous paleosols and paleoclimate in Sichuan Basin, China

Authors:

Li et al

Abstract:

Abundant Lower Cretaceous (Berriasian–Hauterivian) paleosols have been recognized in the Sichuan Basin, along with the preserved pedogenetic features, e.g., soil horizons, soil structure, root traces and pedogenic nodules. Chemical, geochemical and mineralogical analyses were used to examine the paleosols. These paleosols were classified as Entisols, Inceptisols, Aridisols and Alfisols in terms of the modern soil taxonomic system. Early Cretaceous paleoprecipitation and paleotemperature in the Sichuan Basin were estimated from the degree of chemical weathering for non-calcareous paleosols, and from the depth to the calcic horizon and stable oxygen isotopic composition of pedogenic carbonates in calcareous paleosols, respectively. A temperate semi-arid climate generally prevailed in the Sichuan Basin as a part of the South China Block (SCB) and was controlled by subtropical high-pressure and a rain-shadow effect because the humid air masses from the Paleo-Pacific were impeded by the highlands of the South China Block. Further, several intervals of sub-humid paleoclimate occurred due to strengthened monsoonal circulation in the Early Cretaceous. Using the paleosol barometer, the paleoatmospheric CO2 levels of the Early Cretaceous are estimated to range from ∼120 to ∼520 ppmv, with a mean of 305 ppmv. Regional temperature is generally coupled with atmospheric CO2 concentration and is roughly consistent with the sea level fluctuation.

Purranisaurus potens: a Very Strange Metriorhynchid Thalattosaur From Tithonian Jurassic/Berriasian Cretaceous Patagonia

Purranisaurus potens Rusconi, an enigmatic metriorhynchid from the Late Jurassic–Early Cretaceous of the Neuquén Basin

Authors:

Herrera et al

Abstract:

The Tithonian record from northwestern Patagonia (Neuquén Basin) documents a complete succession of lower, middle, and late Tithonian marine reptiles. From the late Tithonian–early Berriasian of Patagonia, three marine crocodyliforms have been recorded: Dakosaurus andiniensis, Cricosaurus araucanensis, and Purranisaurus potens. Although P. potens includes the first metriorhynchid skull described from Patagonia, no detailed description and/or illustrations have been published. Since the mid-20th century, several authors have discussed the validity of P. potens. Recent preparation of the type material allowed a detailed description as well as exploration of its phylogenetic relationships. We consider P. potens as a valid taxon characterized by a unique combination of characters, such as medial and posterolateral processes of the frontal forming an angle of 60°; supratemporal fossae reaching the minimum interorbital distance, with the dorsal margin of the supratemporal arch being slightly concave in lateral view; thin bony lamina projecting from the lateral and medial alveolar margins of the maxilla; occipital surface ventral to occipital condyle parallel to transverse plane of skull; well-developed crest that extends along the entire height of the supraoccipital; and orbital process of the quadrate very conspicuous and acute, horizontal, and without bony attachment. Phylogenetic analysis recovers P. potens as deeply nested within Geosaurini and, contrary to previous proposals, not closely related to ‘Metriorhynchus’ casamiquelai and ‘M.’ westermanni. Internal relationships within Geosaurini are unresolved. Purranisaurus, as a monotypic genus, is restricted to the late Tithonian–early Berriasian.

Three Oldest Known Snake Fossils Found From Jurassic Bathonian Jurassic Britain, Kimmeridgian Jurassic Portugal

Fossilized remains of four ancient snakes have been dated between 140 and 167 million years old - nearly 70 million years older than the previous record of ancient snake fossils - and are changing the way we think about the origins of snakes, and how and when it happened. The findings have been published in the prestigious peer-reviewed journal Nature Communications.

"The study explores the idea that evolution within the group called 'snakes' is much more complex than previously thought," says lead author and professor Michael Caldwell in the Faculty of Science at the University of Alberta. "Importantly, there is now a significant knowledge gap to be bridged by future research as no fossils snakes are known from between 140 to 100 million years ago."

The oldest known snake, from Southern England, near Kirtlington, Eophis underwoodi, is known only from very fragmentary remains and was a small individual, though it is hard to say how old it was at the time it died. The largest snake, Portugalophis lignites, from coal deposits in Portugal, near Guimarota, was a much bigger individual at nearly a meter or more in length. Several of these ancient snakes (Eophis, Portugalophis and Parviraptor) were living in swampy coastal areas on large island chains in western parts of ancient Europe, while the North American species, Diablophis gilmorei, is found in river deposits from some distance inland in Western Colorado.

This new study makes it clear that the sudden appearance of snakes, some 100 million years ago, reflects a gap in the fossil record, not an explosive radiation of early snakes. From 167 to 100 million years ago, some 70 million years, snakes were radiating and evolving towards the elongate, limb-reduced body plan characterizing the now well known, ~100-90 million year old, marine snakes from the West Bank, Lebanon, and Argentina, that still possess small but well developed rear limbs. As is always the case, the distribution of these newer oldest snakes, and the anatomy of the skull and skeletal elements, makes it clear that even older snake fossils are waiting to be found.

"Based on the new evidence and through comparison to living legless lizards that are not snakes," explains Caldwell, "the paper explores the novel idea that the evolution of the characteristic snake skull and its parts appeared long before snakes lost their legs."

link.

paper link.

Relic Sauropod Lineage From Berriasian/Valanginian Cretaceous North America

The oldest Cretaceous North American sauropod dinosaur

Authors:

D'emic et al

Abstract:

Sauropod dinosaurs have been found in sediments dating to most of the Cretaceous Period on all major Mesozoic landmasses, but this record is spatiotemporally uneven, even in relatively well-explored North American sediments. Within the 80 million-year-span of the Cretaceous, no definitive sauropod occurrences are known in North America from two ca. 20–25 million-year-long gaps, one from approximately the Berriasian–Barremian and the other from the mid-Cenomanian–late Campanian. Herein, we present an undescribed specimen that was collected in the middle part of the twentieth century that expands the known spatiotemporal distribution of Early Cretaceous North American sauropods, partially filling the earlier gap. The material is from the Berriasian–Valanginian-aged (ca. 139 Ma) Chilson Member of the Lakota Formation of South Dakota and appears to represent the only non-titanosauriform from the Cretaceous of North America or Asia. It closely resembles Camarasaurus and may represent a form closely related to that genus that persisted across the Jurassic–Cretaceous boundary.

Should the Berriasian Cretaceous Really be the Berriasian Jurassic?

New constraints on the Jurassic–Cretaceous boundary in the High Andes using high-precision U–Pb data

Authors:

Vennari et al

Abstract:

The Jurassic–Cretaceous (J–K) boundary is poorly constrained, and is the only Phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section (GSSP). Precise radio-isotopic U–Pb data are unavailable for the earliest stage of the Cretaceous— the Berriasian. The age of the Jurassic–Cretaceous boundary was based on several assumptions, including the relative duration of ammonite zones, the constant spreading rates of magnetic anomalies, and the extrapolation of Rb–Sr or K–Ar isotopic data. This paper discusses a site in an Andean Basin of Western Gondwana showing the J–K boundary interval with geographically widespread nannofossil markers which are here uniquely combined with precise radiometric dates. The recent finding of a sequence of marine black shales in the High Andes of Argentina, interbedded with ash-fall tuffs, provides important constraints on this boundary. This succession bears calcareous nannofossils and ammonites, which allow correlation with well-established Tethyan floras and faunas in the northern hemisphere. The Tithonian–Berriasian transition in the Andes was recognized on the basis of ammonite zones and nannofossil bioevents for the first time in the southern hemisphere. The new ages obtained are 137.9 ± 0.9 Ma by sensitive high-resolution ion microprobe (SHRIMP), and 139.55 ± 0.09/0.18 Ma by chemical-abrasion isotope-dilution thermal ionization mass spectrometry (TIMS) near the base of the Berriasian. These new ages can be interpreted in two different ways. The first alternative would indicate that the present geological time table is correct and the fossil levels should be late Berriasian. The second alternative is that the J–K boundary is 5 Ma younger than the recently published geological time scale. The authors support the last alternative and propose that the J–K boundary should be close to 140 Ma.

Mammalian Faunal Transition in Berriasian/Barremanian Cretaceous North America

Earliest Cretaceous mammals from the western United States

Authors:

Cifelli et al

Abstract:

Mammalian diversity in North America shifted significantly during the Early Cretaceous, from archaic groups dominant in the well-sampled faunas of the Late Jurassic to advanced forms (including early members of modern clades) by the Albian–Cenomanian. However, the dynamics of this transition are poorly understood, since faunas of earliest Cretaceous age are unknown. Here we describe the first fossil mammals from exposures of the Lakota Formation in the Black Hills of South Dakota, a unit correlated with the upper Berriasian–lower Barremian and positioned stratigraphically between the underlying Morrison Formation and Aptian–Albian units exposed elsewhere in North America. The mammalian fauna from the Lakota Formation is transitional with regard to the North American fossil record, representing a broad spectrum of both Jurassic and Cretaceous lineages: present are “plagiaulacidan” multituberculates allied with Late Jurassic Allodontoidea and Early Cretaceous Plagiaulacoidea; the geologically youngest dryolestoid(s) and “triconodontine” triconodontids (characteristic Late Jurassic taxa from the Morrison Formation); the oldest spalacotheriid “symmetrodont”; the first record of an amphitheriid-like stem zatherian from North America (abundant in the Middle Jurassic–earliest Cretaceous of Europe); and the oldest North American tribosphenic mammal (abundant and diverse on the continent by the end of the Early Cretaceous). Taxa making their first North American appearance in the Lakota Formation (Plagiaulacoidea, including a genus also known from the Purbeck of Britain; Spalacotheriidae, stem Zatheria, Tribosphenida) are also known from the Early Cretaceous of Western Europe, suggesting the possibility that they represent immigrants.

Kimmeridgian/Tithonian Jurassic Spain's Ecology Always had at Least two Megatheropods

Megatheropods as apex predators in the typically Jurassic ecosystems of the Villar del Arzobispo Formation (Iberian Range, Spain)

Authors:

Cobos et al

Abstract:

The limestone, sandstone and clays of the Villar del Arzobispo Formation (Kimmeridgian–Berriasian) crop out in the south of the Iberian Range (Spain), and from a palaeontological point of view, the formation is characterised by dozens of sites with dinosaur fossils. The most abundant are the sauropods and stegosaurs, while the ornithopods are scarce, and theropods (especially large–sized ones) are very rare. Here are described some fossils of large–sized theropods (a new tooth and a tridactyl trackway) found at two sites of this formation within the Peñagolosa sub–basin (Maestrazgo Basin) in Teruel province. The new tooth from Formiche Alto is attributed to a large indeterminate tetanuran, possibly a megalosaurid, and is closely related to other large fossil teeth from this formation in Riodeva and Galve (Teruel) and Alpuente (Valencia). In addition, a distinctive morphology of the large–sized tridactyl footprints in the trackway found at the El Castellar tracksite at the village of the same name, allows the establishment of a new ichnotaxon, Iberosauripus grandis ichnogen. et ichnosp. nov. It is easily differentiated from a number of previously named ichnotaxa and suggests the ichnological record of large theropods from the Upper Jurassic of Europe, North America and Asia can be divided into two distinct groups, whose trackmakers were probably members of Megalosauridae and Allosauridae. Keeping in mind that smaller and also different teeth related to allosaurids have been previously described, it is concluded that the dinosaur assemblages in this formation include at least two types of large–sized megatheropod tetanurans which, when fully grown, were responsible for the large–sized tridactyl footprints found in this unit. The predation pressure exerted by these theropods can be seen as a significant cause stimulating the gigantic sizes of some sauropods (like Turiasaurus and Losillasaurus) found in the same formation.

Berriasian Cretaceous Track Makers Were Orinthopod Dinosaurs, not Theropods

Discriminating between Medium-Sized Tridactyl Trackmakers: Tracking Ornithopod Tracks in the Base of the Cretaceous (Berriasian, Spain)

Authors:

Castanera et al

Abstract:

Background

Recent work on the Jurassic-Cretaceous transition of the Iberian Range (Spain) has opened a new window onto the interpretation of the trackmakers of some medium-sized tridactyl tracks. The ichnotaxon Therangospodus oncalensis has been described in the Huérteles Formation (Berriasian) and is one of the classical tracks from the area assigned to medium-sized theropods.

Methodology/Principal Findings

A review of the type locality of Therangospodus oncalensis (Fuentesalvo tracksite) and other tracksites from the Huérteles Formation (Berriasian) has yielded new information on the morphology, gait and trackmaker identity of the aforementioned ichnospecies. The new data suggest that the trackmaker is an ornithopod rather than a theropod on the basis of the length/width ratio, the anterior triangle length-width ratio, the short steps, the round to quadrangular heel pad impression and the probable manus impressions.

Conclusions/Significance

T. oncalensis shows similarities with various tracks from the Berriasian of Europe assigned to Iguanodontipus. The ichnotaxonomical status of this ichnospecies is here considered as Iguanodontipus? oncalensis due to the current state of knowledge of the ichnotaxonomy of medium-sized ornithopod tracks. This reassessment of I? oncalensis also has two significant implications for the palaeoecology of the faunas during the deposition of the Huérteles Formation: 1- the high number and percentage of theropod tracks would be lower than previous papers have suggested. 2- the gregarious behaviour described in the type locality (Fuentesalvo) would be among ornithopods instead of theropods.

A Pterosaur Trackway From Berriasian Cretaceous Germany

The First Record of the Pterosaur Ichnogenus Purbeckopus in the Late Berriasian (Early Cretaceous) of Northwest Germany

Authors:

Jahn J. Hornung & Mike Reich


Abstract:

A hypichnium of a manus imprint (preserved as plaster cast) indicates for the first time the presence of the large pterosaur ichnotaxon Purbeckopus cf. pentadactylus Delair, 1963 in the late Berriasian of northwest Germany. It is only the second record of Purbeckopus globally and the first pterosaur track from Germany. It provides evidence of a very large pterosaur (wingspan c. 6 m) in this area and from this time period not yet represented by skeletal remains. When compared with the English type material, the specimen exhibits some differences that are related mostly to different properties of the substrate on which both were left. These include, in the German track, an impression of the metacarpo-phalangeal joint of the wing finger, normally not present in pterosaur tracks. Also interesting is the rather blunt termination of the deeply impressed digits I–III, indicating rather short and blunt claws, which seem more suitable for walking than for grasping or climbing. The specimens of Purbeckopus in England and Germany occur in different environments: the English locality was situated close to a brackish lagoon, while the German site belongs to a limnic-deltaic system at the margin of a large, freshwater lake.

Constraints on the Jurassic-Cretaceous Boundary in the High Andes

New constraints in the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data

Authors:

1. Verónica V. Vennari (a)
2. Marina Lescano (a)
3. Maximiliano Naipauer (a)
4. Beatriz Aguirre-Urreta (a)
5. Andrea Concheyro (a)
6. Urs Schaltegger (b)
7. Richard Armstrong (c)
8. Marcio Pimentel (d)
9. Victor A. Ramos (a)

Affiliations:

a. Instituto de Estudios Andinos Don Pablo Groeber, Universidad de Buenos Aires-CONICET, Buenos Aires, Argentina

b. Section of Earth and Environmental Sciences, Université de Genève, Switzerland

c. Research School of Earth Sciences, Australian National University, Canberra, Australia

d. Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

Abstract:

The Jurassic-Cretaceous (J-K) boundary is poorly constrained, and is the only Phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section (GSSP). Precise radio-isotopic U-Pb data are unavailable for the earliest stage of the Cretaceous– the Berriasian. The age of the Jurassic-Cretaceous boundary was based on several assumptions, including the relative duration of ammonite zones, the constant spreading rates of magnetic anomalies, and the extrapolation of Rb-Sr or K-Ar isotopic data. This paper discusses a site in an Andean Basin of Western Gondwana showing the J-K boundary interval with geographically widespread nannofossil markers which are here uniquely combined with precise radiometric dates. The recent finding of a sequence of marine black shales in the High Andes of Argentina, interbedded with ash-fall tuffs, provides important constraints on this boundary. This succession bears calcareous nannofossils and ammonites, which allow correlation with well-established Tethyan floras and faunas in the northern hemisphere. The Tithonian-Berriasian transition in the Andes was recognized on the basis of ammonite zones and nannofossil bioevents for the first time in the southern hemisphere. The new ages obtained are 137.9 ± 0.9 Ma by sensitive high-resolution ion microprobe (SHRIMP), and 139.55 ± 0.09/0.18 Ma by chemical-abrasion isotope-dilution thermal ionization mass spectrometry (TIMS) near the base of the Berriasian. These new ages can be interpreted in two different ways. The first alternative would indicate that the present geological time table is correct and the fossil levels should be late Berriasian. The second alternative is that the J-K boundary is 5 Ma younger than the recently published geological time scale. The authors support the last alternative and propose that the J-K boundary should be close to 140 Ma.

Pterosaur Landing Trace Fossils Found

I've seen in some of the news bits our own Dave Hone quoted. Quite kewl.

Anyone have a link to the paper?

Earliest Spider Web in Amber

The tiny tangled threads of the world's oldest spider web have been found encased in a prehistoric piece of amber, a British scientist said Monday.

Oxford University paleobiologist Martin Brasier said the 140-million-year-old webbing provides evidence that arachnids had been ensnaring their prey in silky nets since the dinosaur age. He also said the strands were linked to each other in the roughly circular pattern familiar to gardeners the world over.

"You can match the details of the spider's web with the spider's web in my garden," Brasier said.

The web was found in a small piece of amber picked up by an amateur fossil-hunter scouring the beaches on England's south coast about two years ago, Brasier said. A microscope revealed the existence of tiny threads about 1 millimeter (1/20th of an inch) long amid bits of burnt sap and fossilized vegetable matter.

While not as dramatic as a fully preserved net of spider silk, the minuscule strands show that spiders had been spinning circle-shaped webs well into prehistory, according to Simon Braddy, a University of Bristol paleobiologist uninvolved with the find.

"It's not a striking, perfect web," Braddy said. "(But) this seems to confirm that spiders were building orb webs back in the early Cretaceous" — the geological term for the period of time between 145.5 and 65.5 million years ago when dinosaurs and small mammals shared the earth.

140 MYA puts it on the Valanginian-Berriasian boundary more or less.

New Cretaceous Bolivian Trackway Found

Bolivian farmer Primo Rivera had long wondered about the dents in a rocky hill near his home. Paleontologists solved the mystery this month: they are fossilized dinosaur footprints -- the oldest in Bolivia.

"I used to come to look at the prints when I was a kid ... but I didn't know what had made them," said Rivera, 35, who lives in the southern province of Chuquisaca.

The fossilized footsteps that intrigued Rivera for two decades are thought to be about 140 million years old, much older than other dinosaur prints found in the Andean country.

"The footprints we've found are important because they're the oldest ever found in Bolivia ... and the oldest footprints of Ankylosaurus ever found in the Southern Hemisphere," said Argentine paleontologist Sebastian Apesteguia in Buenos Aires.

Apesteguia, who led a two-week expedition sponsored by Chuquisaca's regional government, thinks the footprints belong to three different kinds of dinosaurs, including Ankylosaurus, an armored herbivore.

He said some of the prints were about 14 inches long, suggesting that the dinosaurs were "medium-sized ... about nine or 10 meters (about 30 feet) in length."

Close to the larger prints, the paleontologists found smaller ones that probably belonged to baby dinosaurs, indicating the offspring "were given some kind of care," Apesteguia said.

Dino tracks from SoAm from the Berriasian-Valangian (Early/Lower Cretaceous) Boundary. Interesting, interesting. They look like sauropod tracks, but its hard to tell for sure with those images. There are more through the link.