Evidence of Orbital Climate Forcing at the Triassic/Jurassic Boundary

Triassic–Jurassic climate in continental high-latitude Asia was dominated by obliquity-paced variations (Junggar Basin, Ürümqi, China)

Authors:

Sha et al

Abstract:

Empirical constraints on orbital gravitational solutions for the Solar System can be derived from the Earth’s geological record of past climates. Lithologically based paleoclimate data from the thick, coal-bearing, fluvial-lacustrine sequences of the Junggar Basin of Northwestern China (paleolatitude ∼60°) show that climate variability of the warm and glacier-free high latitudes of the latest Triassic–Early Jurassic (∼198–202 Ma) Pangea was strongly paced by obliquity-dominated (∼40 ky) orbital cyclicity, based on an age model using the 405-ky cycle of eccentricity. In contrast, coeval low-latitude continental climate was much more strongly paced by climatic precession, with virtually no hint of obliquity. Although this previously unknown obliquity dominance at high latitude is not necessarily unexpected in a high CO2 world, these data deviate substantially from published orbital solutions in period and amplitude for eccentricity cycles greater than 405 ky, consistent with chaotic diffusion of the Solar System. In contrast, there are indications that the Earth–Mars orbital resonance was in today’s 2-to-1 ratio of eccentricity to inclination. These empirical data underscore the need for temporally comprehensive, highly reliable data, as well as new gravitational solutions fitting those data.

Ichthyosaurus anningae: a new Fish Lizard From Hettangian/Sinemurian–Pliensbachian Jurassic England

A new species of Ichthyosaurus from the Lower Jurassic of West Dorset, England, U.K.

Authors:

Lomax et al

Abstract:

We describe a new species of Lower Jurassic (Hettangian/Sinemurian–Pliensbachian) ichthyosaur, Ichthyosaurus anningae, sp. nov., from west Dorset, England, U.K. The holotype of I. anningae (DONMG:1983.98), at least a subadult, is from the lower Pliensbachian Stonebarrow Marl Member (Charmouth Mudstone Formation). It is the most complete ichthyosaur known from this time interval worldwide. The species is assigned to Ichthyosaurus on the basis of humerus, forefin, and pectoral girdle morphologies. Diagnostic features of the species include a short, robust humerus with prominent processes; a femur in which the proximal width is almost as large as the distal width; and a very small femur relative to the humerus (humerus/femur ratio >1.7). Four other specimens, at least three of which are juveniles, are referred to this species. The new species may display sexual dimorphism in humeral morphology, but this cannot be confirmed due to a lack of stratigraphic information. With the recognition of I. anningae, at least three and possibly as many as five ichthyosaur species, representing three genera, are known from the Pliensbachian.

More Information About the Hettangian Jurassic/Post Triassic-Jurassic Mass Extinction Sponge Bob World

Andean sponges reveal long-term benthic ecosystem shifts following the end-Triassic mass extinction

Authors:

Ritterbush et al

Abstract:

Thick cherts and cherty dolomites in the basal Jurassic Aramachay Formation of Peru preserve a thriving continental shelf community dominated by siliceous sponges that followed the end-Triassic collapse of metazoan-rich carbonate accumulation. Similar Hettangian and Sineumurian deposits from Nevada, U.S.A., Austria, and Morocco suggest that an Early Jurassic siliceous sponge takeover was a widespread phenomenon that persisted for ~ 2 m.y. until metazoan-driven carbonate sedimentation recovered. The post-extinction dominance of siliceous sponges likely resulted from the confluence of metazoan carbonate reef collapse (removal of incumbents) and geochemical conditions that fostered the success of the siliceous sponge-dominated ecosystem. Simple mass balance calculations suggest the siliceous sponge takeover was likely permitted by an increased silica flux as a consequence of weathering Central Atlantic Magmatic Province (CAMP) basalts. The CAMP basalts alone could supply all the silica needed to sustain the sponge takeover, although contributions were also likely from increased hot-climate weathering of other silicates and possible reductions in dissolved silica demand by radiolarians. Detailed sedimentological, fossil, and microfacies analyses were conducted at six field sites across a shallow shelf system recorded in the central Peruvian Andes (Yauli Dome), focusing on the metazoan contribution to sedimentation. Sedimentary structures at all six sites demonstrated on-shelf deposition, similar to the underlying upper Triassic Chambará Formation (in contrast to the black shale-rich facies of the Aramachay Formation in other areas of Peru). Examination of up to 147 m of cherty dolomite from the Aramachay Formation revealed a siliceous sponge-dominated ecosystem, including sponge body fossils, compressed in situ sponge materials, and abundant transported spiculite sediments. Siliceous sponges, mostly demosponges and rare hexactinellids, account for the chert lithology and apparently dominated the local ecology for approximately two million years. The role of metazoan biocalcifiers in sediment production and ecological structure was profoundly reduced compared to the under- and overlying formations, representing a clear ecological state shift from pre-extinction carbonate to post-extinction siliceous dominated ecosystems before the carbonate system recovered ~ 2 m.y. after the extinction.

Hettangian Jurassic Oceans Became Sponge Bob World After Triassic-Jurassic Extinction?

NEW EVIDENCE ON THE ROLE OF SILICEOUS SPONGES IN ECOLOGY AND SEDIMENTARY FACIES DEVELOPMENT IN EASTERN PANTHALASSA FOLLOWING THE TRIASSIC–JURASSIC MASS EXTINCTION

Authors:

Ritterbush et al

Abstract:

Paleoecological consequences of the global Triassic–Jurassic mass extinction (201.3 Ma) are poorly understood. Fossiliferous marine boundary records are rare, commonly condensed, and typically reveal facies changes previously attributed to eustacy. Sedimentology and biofacies analyses from stratigraphically expanded successions of the lowest Jurassic strata, New York Canyon, Nevada, were investigated with high-resolution paleoenvironmental observations, fossil surveys, and microfacies analysis. Following the collapse of the uppermost Triassic carbonate ramp, the lowest Jurassic Ferguson Hill Member of the Sunrise Formation records a midshelf habitat dominated by previously unrecognized siliceous sponges for approximately two million years. In addition, the earliest Jurassic strata from the Pucara Group, central Peruvian Andes, were examined and record a more greatly expanded stratigraphic succession of facies across the inner to middle shelf. Like Nevada, the lowest Jurassic Aramachay Formation is replete with intense concentrations of siliceous sponges. The revelation of widespread, ecologically dominant siliceous sponges has been overlooked despite detailed biofacies studies in both depositional systems. Sponges expanded across shallow environments with sparse benthic biocalcifier populations, and were likely aided by increased ocean silica concentrations from the weathering of the Central Atlantic Magmatic Province. Facies changes previously attributed to sea-level change are thus interpreted to result from the collapse of the carbonate factory concomitant with the mass extinction, with transition to an alternate state dominated by siliceous sponges before a return to carbonate platform development in the Sinemurian. Our study highlights the need to separate biofacies from paleoenvironmental analysis during mass extinction times when nonactualistic assemblages may dominate and deviate from expected environments (e.g., siliceous sponges as indicators of deep paleoenvironments).

Tachiraptor admirabilis: a new Theropod From Hetttangian Jurassic Venezuela

A newly described dinosaur, whose fossils are some of the first to be unearthed in Venezuela, turns out to be the close, relatively small kin of creatures that later evolved into multiton meat eaters such as Allosaurus and Tyrannosaurus rex. The creature, and another dinosaur whose fossils were found nearby and reported just 2 months ago, are filling in gaps in the fossil record and revealing new insights into dinosaur evolution in the wake of a mass extinction that happened about 201 million years ago.

The new species, dubbed Tachiraptor admirabilis, is a predator that gets part of its name from the Venezuelan state of Táchira, where the fossils were found. Only two bones of the ancient species have been unearthed, says Max Langer, a vertebrate paleontologist at the University of São Paulo in Brazil. Nevertheless, those bits (each from a different individual, and one of them not even a complete bone) tell scientists a lot, Langer notes.

link.

Hettangian Jurassic Temnospondyl Trackway From Africa Show Radically Different Movement Than Extant Terrestrial Tetrapods

A Temnospondyl Trackway from the Early Mesozoic of Western Gondwana and Its Implications for Basal Tetrapod Locomotion

Authors:

Marsicano et al

Abstract:

Background

Temnospondyls are one of the earliest radiations of limbed vertebrates. Skeletal remains of more than 190 genera have been identified from late Paleozoic and early Mesozoic rocks. Paleozoic temnospondyls comprise mainly small to medium sized forms of diverse habits ranging from fully aquatic to fully terrestrial. Accordingly, their ichnological record includes tracks described from many Laurasian localities. Mesozoic temnospondyls, in contrast, include mostly medium to large aquatic or semi-aquatic forms. Exceedingly few fossil tracks or trackways have been attributed to Mesozoic temnospondyls, and as a consequence very little is known of their locomotor capabilities on land.

Methodology/Principal Findings

We report a ca. 200 Ma trackway, Episcopopus ventrosus, from Lesotho, southern Africa that was made by a 3.5 m-long animal. This relatively long trackway records the trackmaker dragging its body along a wet substrate using only the tips of its digits, which in the manus left characteristic drag marks. Based on detailed mapping, casting, and laser scanning of the best-preserved part of the trackway, we identified synapomorphies (e.g., tetradactyl manus, pentadactyl pes) and symplesiomorphies (e.g., absence of claws) in the Episcopopus trackway that indicate a temnospondyl trackmaker.

Conclusions/Significance

Our analysis shows that the Episcopopus trackmaker progressed with a sprawling posture, using a lateral-sequence walk. Its forelimbs were the major propulsive elements and there was little lateral bending of the trunk. We suggest this locomotor style, which differs dramatically from the hindlimb-driven locomotion of salamanders and other extant terrestrial tetrapods can be explained by the forwardly shifted center of mass resulting from the relatively large heads and heavily pectoral girdles of temnospondyls.

Laquintasaura: The First Hettangian Jurassic Ornithischian From Venezuela

A palaeoequatorial ornithischian and new constraints on early dinosaur diversification

Authors:

Barrett et al

Abstract:

Current characterizations of early dinosaur evolution are incomplete: existing palaeobiological and phylogenetic scenarios are based on a fossil record dominated by saurischians and the implications of the early ornithischian record are often overlooked. Moreover, the timings of deep phylogenetic divergences within Dinosauria are poorly constrained owing to the absence of a rigorous chronostratigraphical framework for key Late Triassic–Early Jurassic localities. A new dinosaur from the earliest Jurassic of the Venezuelan Andes is the first basal ornithischian recovered from terrestrial deposits directly associated with a precise radioisotopic date and the first-named dinosaur from northern South America. It expands the early palaeogeographical range of Ornithischia to palaeoequatorial regions, an area sometimes thought to be devoid of early dinosaur taxa, and offers insights into early dinosaur growth rates, the evolution of sociality and the rapid tempo of the global dinosaur radiation following the end-Triassic mass extinction, helping to underscore the importance of the ornithischian record in broad-scale discussions of early dinosaur history.

Triassic-Jurassic Extinction Probably Caused by Global Warming Rather Than Ocean Acidification

Radiolarian biodiversity dynamics through the Triassic and Jurassic: implications for proximate causes of the end-Triassic mass extinction

Authors:

Kocsis et al

Abstract:

Within a ∼60-Myr interval in the Late Triassic to Early Jurassic, a major mass extinction took place at the end of Triassic, and several biotic and environmental events of lesser magnitude have been recognized. Climate warming, ocean acidification, and a biocalcification crisis figure prominently in scenarios for the end-Triassic event and have been also suggested for the early Toarcian. Radiolarians, as the most abundant silica-secreting marine microfossils of the time, provide a control group against marine calcareous taxa in testing selectivity and responses to changing environmental parameters. We analyzed the origination and extinction rates of radiolarians, using data from the Paleobiology Database and employing sampling standardization, the recently developed gap-filler equations and an improved stratigraphic resolution at the substage level. The major end-Triassic event is well-supported by a late Rhaetian peak in extinction rates. Because calcifying and siliceous organisms appear similarly affected, we consider global warming a more likely proximate trigger of the extinctions than ocean acidification. The previously reported smaller events of radiolarian turnover fail to register above background levels in our analyses. The apparent early Norian extinction peak is not significant compared to the long-term trajectory, and is probably a sampling artifact. The Toarcian Oceanic Anoxic Event, previously also thought to have caused a significant radiolarian turnover, did not significantly affect the group. Radiolarian diversity history appears unique and complexly forced, as its trajectory parallels major calcareous fossil groups at some events and deviates at others.

Theropod Found in Hettangian Jurassic Luxembourg

The first Early Jurassic (late Hettangian) theropod dinosaur remains from the Grand Duchy of Luxembourg

Authors:

Delsate et al

Abstract:

Body fossils of earliest Jurassic (Hettangian) dinosaurs are scarce worldwide. Here we report two isolated dinosaur remains from the marine upper Hettangian (the Schlotheimia angulata ammonite Zone) Luxembourg Sandstone Formation, collected at Brouch, Grand Duchy of Luxembourg. The small to medium-sized pedal phalanx III-1 is referred to a neotheropod dinosaur based on the combination of the following features: proximal end with a lateral margin formed by two straight margins meeting at a wide angle, distal end with a well-defined semilunate extensor fossa and a proximodistally elongated shaft. The isolated tooth crown most likely belongs to an indeterminate theropod, because of its labiolingually compressed shape and the presence of sharp mesial and distal carinae and denticles along its distal edge. These remains represent the first Jurassic dinosaur specimens reported from the Grand Duchy of Luxembourg, enlarging the meagre record of the group immediately after the Triassic-Jurassic mass extinction event.

Evidence of Eusocial Insects from the Hettangian/Sinemurian Jurassic of China?

Novel insect traces on a dinosaur skeleton from the Lower Jurassic Lufeng Formation of China

Authors:

1. Lida Xing (a, b)
2. Eric M. Roberts (c)
3. Jerald D. Harris (d)
4. Murray K. Gingras (e)
5. Hao Ran (f)
6. Jianping Zhang (a)
7. Xing Xu (g)
8. Michael E. Burns(b)
9. Zhiming Dong (g)

Affiliations:

a. School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

b. Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, Alberta T6G 2E9, Canada

c. School of Earth and Environmental Science, James Cook University, Townsville, Qld 4811, Australia

d. Physical Sciences Department, Dixie State College, 225 South 700 East, St. George, Utah 84770, USA

e. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada

f. Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin 541004, China

g. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China

Abstract:

Dense networks of burrow-like traces on the surfaces of bones are preserved on a partial skeleton of a prosauropod dinosaur (cf. Yunnanosaurus) from the Lower Jurassic Lufeng Formation in Yunnan, China. The traces, which gently meander across and, in places, shallowly excavate the surfaces of several axial and appendicular skeletal elements (total cumulative length over 29 m) consist of simple burrows, Y-shaped branches, overlapping intersections, and chambers. This unusual network is morphologically most similar to foraging traces of eusocial insects, particularly termites. Comparisons of known continental ichnofossils, demonstrate the novelty of this trace, which thus pertains to a new ichnotaxon, Taotieichnus orientalis ichnogen. et ichnosp. nov. Taotieichnus orientalis most closely resembles subaerial foraging galleries constructed of mud or carton (saliva and faecal material mixed with soil or partially digested wood particles) and produced by a range of subterranean termites. Periodic, possibly seasonal, use of carrion as a nutrient source, and the construction of carton foraging galleries over decomposing vertebrate carcasses, is a known, but little documented, dietary supplement for some xylophagus, neotropical termite species. These Early Jurassic traces constitute the earliest evidence of eusocial insect foraging behavior, and suggest that a possible adaptive radiation of stem- or crown-group termites as foragers—or, at least, opportunistic decomposers—of animal carcasses had already occurred by the Early Jurassic.

Hettangian Isle of Skye Corals Give Insight to Post Triassic-Jurassic Mass Extinction Paleoenvironment

The Hettangian corals of the Isle of Skye (Scotland): An opportunity to better understand the palaeoenvironmental conditions during the aftermath of the Triassic – Jurassic boundary crisis

Authors:

1. M. Gretz (a)
2. B. Lathuilière (b, c)
3. R. Martini (a)
4. A. Bartolini (d)

Affiliations:

a. Department of Geology and Paleontology, University of Geneva, 13 rue des Maraîchers, 1205 Geneva, Switzerland

b. Université de Lorraine G2R, UMR 7566, Vandoeuvre-lès-Nancy, BP 239, F-54506, France

c. CNRS G2R, UMR 7566, Vandoeuvre-lès-Nancy, BP 239, F-54506, France

d. Muséum National D’Histoire Naturelle, CR2P « centre de Recherche sur la Paléodiversité et les paléoenvironnements » CNRS UMR 7207, 8 rue Buffon, 75231 Paris Cedex 05, France

Abstract:

At Ob Lusa (Isle of Skye, Scotland), six distinct coral beds were observed in a modern outcrop where a Hettangian succession is exposed. The coral associations are monogenic, belonging to Lepidophyllia, a massive cerioid genus. The lowest bed has relatively well-developed colonies that form small bioconstructions, whereas the other beds have small and dispersed colonies that are completely drowned in the matrix. Their morphology and size can vary, but the general growth fabric is dominated by platy colonies. This type of growth fabric is defined as a platestone. The most surprising characteristic of these specimens, especially for the platy corals, is their growth pattern; many samples do not exhibit the classical growth polarity because they are bifacial. Geochemical analyses (δ180, δ13C) were conducted on oyster shells that were associated with the corals. The results indicate that the mean palaeotemperature was approximately 22 °C. Sedimentological analysis revealed shallow settings where the hydrodynamic energy and siliciclastic inputs fluctuated. The general faunal assemblage of the outcrop had low diversity and was mainly composed of allochthonous bioclasts. The corals at Ob Lusa clearly did not live under ideal environmental conditions for the development of corals.

Complete Remains of an Early Jurassic/Late Triassic Sauropod

Scientists have discovered in China the first complete skeleton of a pivotal ancestor of Earth's largest land animals – the sauropod dinosaurs. The new species, tentatively dubbed Yizhousaurus sunae, lived on the flood plains around Lufeng in the Yunnan Province of South China about 200 million years ago. The species helps explain how the iconic four-footed, long-necked sauropod dinosaurs evolved.

Unlike the 120-foot-long, 100-ton sauropod giants that came later, Yizhousaurus was about 30 feet in length, but it shows all of the hallmarks of later sauropods: the beginning of a long neck, a robust skeleton and four-legged posture. It also comes with an intact fossilized skull – which is very rare and crucial for understanding its place in the evolution of sauropods.

"Sauropods have these big bones but their skulls are very lightly constructed and also very small," said paleontologist Sankar Chatterjee of Texas Tech University. Chatterjee presents the discovery on Sunday, Oct. 31 at the annual meeting of the Geological Society of America in Denver.

Yizhousaurus's skull is broad, high and domed, less than a foot long with a short snout, eye sockets on the sides for scanning enemies. It has an unusually wide and U-shaped jaw, in top view, like that seen in later Camarasaurus, said Chatterjee. Numerous serrated and spoon-shaped teeth of the upper and lower jaws would shear and slide past each other for cutting plant material during feeding. The sturdy teeth and raised neck let the animal very easily nip small branches from treetops and then chew the plant material.

Abstract here.

So is this Hettangian or Rhaetian/Norian?

Basal Theropods Had Bird Hands

Two handprints pressed into the mud of an ancient lakeshore 198 million years ago has given paleontologists new insights into the anatomy and evolution of early carnivorous dinosaurs. The theropod who crouched down had a bird-like forelimb structure with palms that always faced inwards, says lead researcher Andrew Milner, which indicates that they stopped using their forelimbs for walking early in their evolutionary history.

The handprints discovered in Utah are part of a larger track that clearly show the hind feet and, occasionally, the dragging tail. But at one point, Milner said, the theropod apparently stopped and crouched to rest. At that point, between the footprints, is the clear circular impression of the ischium or pelvis, “basically a butt print,” Milner said. And to each side of the tracks are the handprints, which are mirror images of each other. They clearly show the third digit pressed into the ground and traces of the second digit, with the claw curling inward. The hands were positioned as they would be for “holding on to a basketball rather than dribbling it,” [Los Angeles Times], comments paleontologist Tom Holtz, who wasn’t involved in the research.

The new study, published in the journal PLoS ONE, indicates that the unidentified species of theropod couldn’t turn the palms of its hands face down or face up like a human, but could bend them back against the arm similar to how a bird folds its wings. Jerry Harris, who coauthored the paper, said being able to fold the hands against the arms evolved before feathery wings — and at a time earlier than the period normally associated with theropods.

Sarah at Gombessa Girl has two posts on the subject. She knows the people involved and helped out to some extent it seems. Some interesting evolutionary implications here. I wonder how the "birds are not dinosaurs!!!" crowd are going to react? heh.