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.

Makhaira rossica: a new Pliososaur With Crocodile Like Teeth From Hauterivian Cretaceous Russua

Peculiar macrophagous adaptations in a new Cretaceous pliosaurid

Authors:

Fischer et al

Abstract:

During the Middle and Late Jurassic, pliosaurid plesiosaurs evolved gigantic body size and a series of craniodental adaptations that have been linked to the occupation of an apex predator niche. Cretaceous pliosaurids (i.e. Brachaucheninae) depart from this morphology, being slightly smaller and lacking the macrophagous adaptations seen in earlier forms. However, the fossil record of Early Cretaceous pliosaurids is poor, concealing the evolution and ecological diversity of the group. Here, we report a new pliosaurid from the Late Hauterivian (Early Cretaceous) of Russia. Phylogenetic analyses using reduced consensus methods recover it as the basalmost brachauchenine. This pliosaurid is smaller than other derived pliosaurids, has tooth alveoli clustered in pairs and possesses trihedral teeth with complex serrated carinae. Maximum-likelihood ancestral state reconstruction suggests early brachauchenines retained trihedral teeth from their ancestors, but modified this feature in a unique way, convergent with macrophagous archosaurs or sphenacodontoids. Our findings indicate that Early Cretaceous marine reptile teeth with serrated carinae cannot be unequivocally assigned to metriorhynchoid crocodylomorphs. Furthermore, they extend the known diversity of dental adaptations seen in Sauropterygia, the longest lived clade of marine tetrapods.

Montsechia vidalii: Earliest Known Flowering Planet Discovered in Hautervian Cretaceous Spain

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet's earliest flowers, known as angiosperms.

"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences' Department of Geological Sciences.

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country's border with France.

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

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paper link.

There was a 4 C Temperature Drop at High Latitude During the Valanginian Cretaceous

Latitudinal temperature trends in the northern hemisphere during the Early Cretaceous (Valanginian - Hauterivian)

Authors:

Meissner et al

Abstract:

We present the first detailed stable isotope record (δ13C, δ18O) for the Valanginian (Lower Cretaceous) of the southern Boreal Realm. The observations are based on the geochemical analysis of 286 belemnite rostra from stratigraphically well-dated sections in northwest Germany. A major positive carbon isotope excursion (CIE) of ~ 2‰ in the early late Valanginian documents a perturbation of the carbon cycle. This positive CIE, which is well known as the 'Weissert Event' in the Tethys, is also displayed in composite carbon isotope records based on published and own data from three different palaeolatitudes (35°, 39°, 65° North). These findings suggest that the environmental changes indicated by the CIE in the early late Valanginian are synchronous, thereby pointing to a global control. The combined oxygen isotope data sets show long-term fluctuations of up to 7 °C with a cooling in the late Valanginian for both the southern and the arctic part of the Boreal Realm, while Tethyan data document only a ca. 1 °C cooling. Based on a reliable bio- and chemostratigraphic correlation between the different realms this study highlights the amplitude of the environmental perturbations in the Valanginian and supports the idea that a combination of regional and global factors caused such shifts.

A Large Enantiornithine Bird from Hauterivian Cretaceous China

A large enantiornithine bird from the Lower Cretaceous of China and its implication for lung ventilation

Authors:

Zhang et al

Abstract:

The Enantiornithes were the most taxonomically diverse bird group in the Mesozoic. Most of the known taxa are from Lower Cretaceous deposits of the Jehol Group in north-eastern China. A new specimen from the Jiufotang Formation in Jianchang, Liaoning Province, is described here; being a subadult individual at the time of death it had reached a relatively large size. The presence of uncinate processes, bicapitate and forked vertebral ribs, sternal ribs that were all of similar length, as well as the location of parapophyses and diapophyses on the thoracic vertebrae, may imply a rigid and volume-constant lung, and less efficient lung ventilation in enantiornithines.

Eopengornis martini: a new Enantiornithine From China's Hauterivian Cretaceous Jehol Biota

Insights into the evolution of rachis dominated tail feathers from a new basal enantiornithine (Aves: Ornithothoraces)

Authors:

Wang et al

Abstract:

We report on a new enantiornithine Eopengornis martini gen. et sp. nov. from the lowest horizon of the Jehol Biota in Hebei, China; dated at 130.7 Mya, this is the second oldest avian bearing fossil deposit in the world, recording the First Appearance Datum of Enantiornithes. The new specimen, only the second enantiornithine and third bird reported from this horizon, preserves numerous synapomorphies with the largest Lower Cretaceous enantiornithine Pengornis houi from the Jiufotang Formation dated at 120 Mya. Together, they form a new avian lineage that lasted over 10 Myr, which is longer than any known clade of Lower Cretaceous enantiornithine. Eopengornis reveals new information about basal enantiornithine morphology such as the presence of a metatarsal V, helping to clarify the early evolution of these dominant Cretaceous avians. Furthermore, Eopengornis preserves a previously unrecognized tail morphology: a pair of elongate fully pennaceous rachis dominated feathers. This discovery confirms hypotheses proposing that the rachis dominated racket-plumes in basal birds represent modified pennaceous feathers. We suggest that the ornamental racket-plumes in enantiornithines and Confuciusornis evolved independently from the basal pygostylian condition, which we infer was a tail formed of normal flight feathers.

Earliest Evidence of Semi-Aquatic Ferns From Hauterivian/Barremian Cretaceous Spain

Earliest record of semi-aquatic fern leaves (Family Marsileaceae) in the Mesozoic of Eurasia (Lower Cretaceous, Spain)

Authors:

Sender et al

Abstract:

In this paper we present new macrofossils of semi-aquatic fern Family Marsileaceae consisting of leaves and leaflets from the upper Hauterivian- lower Barremian Pinilla de los Moros Formation, Salas de los Infantes village, Burgos province, north of Spain. The leaves show two elliptic to flabellate-shaped leaflets that are joined to a petiole. Leaflets present entire margins and dichotomous anastomosed vein pattern. Comparison between the studied leaves and other marsileaceous leaves indicates close similarities with Regnellites nagashimae species. These leaves were deposited in a related fluvial environment near to the place where semi-aquatic plants grew. The studied macrofossils constitute at present the earliest record of leaves of Family Marsileaceae in the Mesozoic of Eurasia at the moment.

A Valanginian/Hauterivian Cretaceous Ichthyosaur Graveyard From Chile

A Lower Cretaceous ichthyosaur graveyard in deep marine slope channel deposits at Torres del Paine National Park, southern Chile

Authors:

Stinnesbeck et al

Abstract:

Remnants of ophthalmosaurid ichthyosaurs recently discovered in the vicinity of the Tyndall Glacier in the Torres del Paine National Park of southern Chile are extremely abundant and well preserved. After three field campaigns to the area, a total of 46 articulated and virtually complete ichthyosaur specimens, both adults and juveniles, were tentatively assigned to four different species of Ophthalmosauridae. Preservation is excellent and occasionally includes soft tissue and embryos. The skeletons are associated with ammonites, belemnites, inoceramid bivalves, and fishes as well as numerous plant remains. The enormous concentration of ichthyosaurs is unique for Chile and South America and places the Tyndall locality among the prime fossil Lagerstätten for Early Cretaceous marine reptiles worldwide.

The deposit is Early Cretaceous (Valanginian–Hauterivian) in age and forms part of a monotonous bathyal to abyssal sequence of the Late Jurassic to late Early Cretaceous Rocas Verdes back-arc basin. In this region, the Tyndall ichthyosaur population may have profited from cold upwelling currents that caused abundant life at the shelf edge including masses of belemnites and small fish, the preferred diet of ichthyosaurs. The abundance of almost completely articulated ichthyosaur skeletons in the Tyndall area suggests that some animals fell victim to episodic mass-mortality events caused by turbidity currents traveling downslope through a submarine canyon. They lost orientation, drowned, and were dragged into the deep sea by these turbulent high-energy gravity flows. Their bodies ended up in an oxygen-deficient basin environment where they were immediately embedded by the fine turbidite suspension fallout. The Tyndall ichthyosaur locality thus combines characteristics of both concentration and conservation Lagerstätten.

A Ceratopsian Dinosaur From Hauterivian/Berremian Cretaceous Japan

The First Basal Neoceratopsian Dinosaur from the Lower Cretaceous Kanmon Group in Kyushu, Southwestern Japan

Authors:

Tanoue et al

Abstract:

An isolated tooth specimen from the Lower Cretaceous Kanmon Group in Kyushu Island, south-western Japan was initially identified as a hadrosaurid. It is reidentified herein as a neoceratopsian tooth based on the presence of a wide and prominent primary ridge on the crown, a shallow indentation on the right side of the primary ridge in non-occlusal view, and a horizontally oriented cingulum at the base of the crown. The poorly developed cingulum and shallow indentation suggest that it does not pertain to a ceratopsid, but is only referable to a basal neoceratopsian. This represents the first basal neoceratopsian specimen from the Lower Cretaceous of Kyushu Island.

Bay of Biscay Drilling Project in 1981 Yields Interesting Early Cretaceous Paleobotanical Insights

Plant remains from Early Cretaceous deposits on the Goban Spur, Bay of Biscay, North Atlantic Ocean, and their palaeoenvironmental significance

Authors:

Batten et al

Abstract:

Site 549 of the Deep Sea Drilling Project was drilled on the Goban Spur in the Bay of Biscay in 1981. The core recovered from this North Atlantic location included 290 m of Barremian and possibly partly Hauterivian “syn-rift” deposits overlain unconformably by rocks of early Albian age. The number and variety of spores and pollen grains in the palynomorph assemblages and associated palynofacies through these units together with the presence of some pieces of wood, fragments of foliage, and a few megaspores in the lowest part of the Cretaceous succession suggest that the source area vegetation was, at least initially, relatively close to the site of deposition. Ginkgoalean, bennettitalean, and other gymnosperm groups are represented in the plant mesofossil assemblage but most of the fragments of foliage show cheirolepidiaceous characteristics. Five species belonging to this family have been identified and described. Two of these, Frenelopsis atlantica Zhou and Batten and Frenelopsis? alvinii Zhou and Batten, are new and one is unnamed. The composition of the three informally identified suites of spore and pollen assemblages recovered from 49 samples through the Early Cretaceous succession is consistent with age determinations of parts of it determined previously on the basis of dinoflagellate cysts, foraminifera, nannoplankton, and other fossils.

Malawania anachronus: A Ghost Lineage Ichthyosaur Taxon From the Early Cretaceous of

An international team of scientists have revealed a new species of ichthyosaur (a dolphin-like marine reptile from the age of dinosaurs) from Iraq, which revolutionises our understanding of the evolution and extinction of these ancient marine reptiles.

The results, produced by a collaboration of researchers from universities and museums in Belgium and the UK and published today (May 15) in Biology Letters, contradict previous theories that suggest the ichthyosaurs of the Cretaceous period (the span of time between 145 and 66 million years ago) were the last survivors of a group on the decline.

Ichthyosaurs are marine reptiles known from hundreds of fossils from the time of the dinosaurs. "They ranged in size from less than one to over 20 metres in length. All gave birth to live young at sea, and some were fast-swimming, deep-diving animals with enormous eyeballs and a so-called warm-blooded physiology," says lead author Dr Valentin Fischer of the University of Liege in Belgium.

Until recently, it was thought that ichthyosaurs declined gradually in diversity through multiple extinction events during the Jurassic period. These successive events were thought to have killed off all ichthyosaurs except those strongly adapted for fast-swimming life in the open ocean. Due to this pattern, it has been assumed that ichthyosaurs were constantly and rapidly evolving to be ever-faster open-water swimmers; seemingly, there was no 'stasis' in their long evolutionary history.

In the new study (which properly includes Appleby as an author), researchers name it Malawania anachronus, which means 'out of time swimmer'. Despite being Cretaceous in age, Malawania represents the last-known member of a kind of ichthyosaur long believed to have gone extinct during the Early Jurassic, more than 66 million years earlier. Remarkably, this kind of archaic ichthyosaur appears characterised by an evolutionary stasis: they seem not to have changed much between the Early Jurassic and the Cretaceous, a very rare feat in the evolution of marine reptiles.

"Malawania's discovery is similar to that of the coelacanth in the 1930s: it represents an animal that seems 'out of time' for its age. This 'living fossil' of its time demonstrates the existence of a lineage that we had never even imagined. Maybe the existence of such Jurassic-style ichthyosaurs in the Cretaceous has been missed because they always lived in the Middle-East, a region that has previously yielded only a single, very fragmentary ichthyosaur fossil," adds Dr Fischer.

Thanks to both their study of microscopic spores and pollen preserved on the same slab as Malawania, and to their several analyses of the ichthyosaur family tree, Fischer and his colleagues retraced the evolutionary history of Cretaceous ichthyosaurs. In fact, the team was able to show that numerous ichthyosaur groups that appeared during the Triassic and Jurassic ichthyosaur survived into the Cretaceous. It means that the supposed end of Jurassic extinction event did not ever occur for ichthyosaurs, a fact that makes their fossil record quite different from that of other marine reptile groups.

When viewed together with the discovery of another ichthyosaur by the same team in 2012 and named Acamptonectes densus, the discovery of Malawania constitutes a 'revolution' in how we imagine ichthyosaur evolution and extinction. It now seems that ichthyosaurs were still important and diverse during the early part of the Cretaceous. The final extinction of the ichthyosaurs – an event that occurred about 95 million years ago (long before the major meteorite-driven extinction event that ended the Cretaceous) – is now even more confusing than previously assumed.

Darren Naish has a great write up at Tetrapod Zoology.  

Sciurumimus albersdoerferi: A Feathered Megalosaur

A new species of feathered dinosaur discovered in southern Germany is further changing the perception of how predatory dinosaurs looked. The fossil of Sciurumimus albersdoerferi, which lived about 150 million years ago, provides the first evidence of feathered theropod dinosaurs that are not closely related to birds. The fossil is described in a paper published in the Proceedings of the National Academy of Sciences today.

"This is a surprising find from the cradle of feathered dinosaur work, the very formation where the first feathered dinosaur Archaeopteryx was collected over 150 years ago," said Mark Norell, chair of the Division of Palaeontology at the American Museum of Natural History and an author on the new paper along with researchers from Bayerische Staatssammlung für Paläontologie und Geologie and the Ludwig Maximilians University.

Theropods are bipedal, mostly carnivorous dinosaurs. In recent years, scientists have discovered that many extinct theropods had feathers. But this feathering has only been found in theropods that are classified as coelurosaurs, a diverse group including animals like T. rex and birds. Sciurumimus—identified as a megalosaur, not a coelurosaur— is the first exception to this rule. The new species also sits deep within the evolutionary tree of theropods, much more so than coelurosaurs, meaning that the species that stem from Sciurumimus are likely to have similar characteristics.

"All of the feathered predatory dinosaurs known so far represent close relatives of birds," said palaeontologist Oliver Rauhut, of the Bayerische Staatssammlung für Paläontologie und Geologie. "Sciurumimus is much more basal within the dinosaur family tree and thus indicates that all predatory dinosaurs had feathers."

The fossil, which is of a baby Sciurumimus, was found in the limestones of northern Bavaria and preserves remains of a filamentous plumage, indicating that the whole body was covered with feathers. The genus name of Sciurumimus albersdoerferi refers to the scientific name of the tree squirrels, Sciurus, and means "squirrel-mimic"—referring to the especially bushy tail of the animal. The species name honors the private collector who made the specimen available for scientific study.

"Under ultraviolet light, remains of the skin and feathers show up as luminous patches around the skeleton," said co-author Helmut Tischlinger, from the Jura Museum Eichstatt.

Sciurumimus is not only remarkable for its feathers. The skeleton, which represents the most complete predatory dinosaur ever found in Europe, allows a rare glimpse at a young dinosaur. Apart from other known juvenile features, such as large eyes, the new find also confirmed other hypotheses.

"It has been suggested for some time that the lifestyle of predatory dinosaurs changed considerably during their growth," Rauhut said. "Sciurumimus shows a remarkable difference to adult megalosaurs in the dentition, which clearly indicates that it had a different diet."

Wow.  This is cool!