Ben Creisler | 2 Jul 07:53 2016
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[dinosaur] Evolution of Avian Cranium and of Avian Location + Suchian feeding


Ben Creisler



Some recent papers:


Bhart-Anjan S. Bhullar, Michael Hanson, Matteo Fabbri, Adam Pritchard, Gabe S. Bever, and Eva Hoffman (2016)
How to Make a Bird Skull: Major Transitions in the Evolution of the Avian Cranium, Paedomorphosis, and the Beak as a Surrogate Hand.
Integrative and Comparative Biology (advance online publication)
doi:10.1093/icb/icw069 

The avian skull is distinctive in its construction and in its function. Much of bird anatomical variety is expressed in the beak; but the beak itself, largely formed of the premaxillary bone, is set upon a shortened face and a bulbous, enlarged braincase. Here, we use original anatomical observations and reconstructions to describe the overall form of the avian skull in a larger context and to provide a general account of the evolutionary transformation from the early dinosaur skull—the skull of an archosaurian macropredator—to that of modern birds. Facial shortening, the enlargement of the braincase around an enlarged brain (with consequential reduction of circumorbital elements and the adductor chamber), and general thinning and looser articulation of bones are trends. Many of these owe to juvenilization or paedomorphosis, something that is abundantly evident from comparison of a juvenile early theropod (Coelophysis) to early avialans like Archaeopteryx. Near the avian crown, the premaxilla becomes dramatically enlarged and integrated into the characteristic mobile kinetic system of birds. We posit that this addition of a large element onto the skull may be biomechanically feasible only because of the paedomorphic shortening of the face; and kinesis of the beak only because of the paedomorphic thinning of the bones and loosening of articulations, as played out in reverse during the maturation of Coelophysis. Finally, the beak itself becomes elaborated as the hands are integrated into the wing. There are structural, kinematic, and neurological similarities between avian pecking and primate grasping. The ability to precision-select high-quality food against a complex but depauperate background may have permitted crown birds to survive the end-Cretaceous cataclysm by feeding on insects, seeds, and other detritus after the collapse of higher trophic levels in the food web.

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Ashley M. Heers (2016)
New Perspectives on the Ontogeny and Evolution of Avian Locomotion.
Integrative and Comparative Biology (advance online publication)
doi:10.1093/icb/icw065


Close correspondence between form and function is a central tenet of natural selection. One of the most striking, textbook cases for form–function congruence is the evolution of flight and the body plan of birds: compared with other tetrapods, extant adult birds have highly modified integuments and skeletons, and it has traditionally been assumed that many of these modifications are adaptations or exaptations for flight. However, developing birds that lack many of the morphological signatures of flight capacity nevertheless use their developing wings for a variety of flapping behaviors, such as wing-assisted incline running and even brief flight. Immature birds thereby demonstrate that rudimentary “flight” apparatuses are more functional than traditional assumptions about form–function relationships would predict. Here, I review the ontogeny of avian locomotion, highlighting how the developmental acquisition of flight in extant birds can improve our understanding of form–function relationships in the avian body plan, and provide insight into the evolutionary origin of flight among extinct non-avian theropod dinosaurs.

==

Paul Gignac and Haley O’Brien (2016)
Suchian Feeding Success at the Interface of Ontogeny and Macroevolution.
Integrative and Comparative Biology (advance online publication)
doi:10.1093/icb/icw041

Free pdf:

There have been a number of attempts to explain how crocodylian bite-force performance covaries with cranial form and diet. However, the mechanics and morphologies of crocodylian jaws have thus far remained incongruent with data on their performance and evolution. For example, it is largely assumed that the functional anatomy and performance of adults tightly fits the adult niche. At odds with this precept are groups with resource-dependent growth, whose juvenile stages undergo shifts in mass, morphology, and resource usage to overcome strong selection related to issues of small body size, as compared to adults. Crocodylians are an example of such a group. As living suchians, they also have a long and fossil-rich evolutionary history, characterized by analogous increases in body size, diversifications in rostrodental form, and shifts in diet. Here we use biomechanical and evolutionary modeling techniques to study the development and evolution of the suchian feeding apparatus and to formally assess the impact of potential ontogenetic-evolutionary parallels on clade dynamics. We show that patterns of ontogenetic and evolutionary bite-force changes exhibit inverted patterns of heterochrony, indicating that early ontogenetic trends are established as macroevolutionary patterns within Neosuchia, prior to the origin of Eusuchia. Although selection can act on any life-history stage, our findings suggest that selection on neonates and juveniles, in particular, can contribute to functionally important morphologies that aid individual and clade success without being strongly tied to their adult niche.

Ben Creisler | 2 Jul 00:00 2016
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[dinosaur] Allodaposuchus (Eusuchia) species


Ben Creisler


A new paper:

Alejandro Blanco & Christopher A. Brochu (2016)
Intra- and interspecific variability in allodaposuchid crocodylomorphs and the status of western European taxa.
Historical Biology (advance online publication)
DOI:10.1080/08912963.2016.1201081



The genus Allodaposuchus is an endemic eusuchian from the Late Cretaceous of Europe. This genus was erected in 1928 by Baron Franz Nopcsa based on Allodaposuchus precedens from the Maastrichtian of Romania. Fragmentary skulls recovered from France and Spain were later referred to A. precedens, but three new species of Allodaposuchus have since been described: A. subjuniperus, A. palustris and A. hulki. A set of remains from Velaux, France, was recently interpreted as an ontogenetic series of A. precedens, prompting the argument that other species referred to Allodaposuchus are synonyms of A. precedens. Here, we review intra- and interspecific variability among allodaposuchids. Diagnostic characters for different allodaposuchids are outside the ranges of variation for modern species. Ontogenetic (intraspecific) variation observed in the allodaposuchid from Velaux is not in conflict with the presence of at least four taxa in the European Archipelago during the Late Cretaceous.

Ben Creisler | 1 Jul 19:19 2016
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[dinosaur] Giant pterosaurs too big to fly? - Triceratops "family" + saving Mongolian dinosaurs + more



Ben Creisler

Some recent items:

Pterosaurs and the "too big to fly" controversy



****



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Triceratops "family"  of 4 dig continues in Wyoming by Black Hills Institute and Naturalis Biodiversity Center in Leiden (with audio)




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Saving Mongolia’s Dinosaurs:  Palaeocast interview with Bolortsetseg Minjin (podcast)


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Klaus-Peter Lanser's dinosaur discoveries in Balve, Germany (in German)


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Mark Witton's 'Recreating an Age of Reptiles' book now out


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North Dakota paleontologists provide public fossil digs in state



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Reviving the Dinosaurs exhibit at Mexico City's Universum Museo de las Ciencias (in Spanish)




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Weekly news roundup



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Chester, England-- city's proposed "dinosaur trail" brings public concerns about danger of real dinosaurs


Ben Creisler | 30 Jun 19:52 2016
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[dinosaur] Rarity of elasmosaurs in Maastrichtian strata of Netherlands and Belgium


Ben Creisler


A new paper:


Anne S. Schulp, Renée Janssen, Remy R. van Baal, John W.M. Jagt, Eric W.A. Mulder and Hubert B. Vonhof (2016)
Stable isotopes, niche partitioning and the paucity of elasmosaur remains in the Maastrichtian type area.
Netherlands Journal of Geosciences (advance online publication)



Remains of elasmosaurid plesiosaurs are exceedingly rare in the type-Maastrichtian strata (Late Cretaceous, southeast Netherlands and northeast Belgium), in stark contrast to relatively common skeletal remains of mosasaurs. Here, we present an analysis of δ13C stable isotope values for tooth enamel of two elasmosaur teeth from the type Maastrichtian. The δ13C signal is a proxy for foraging area, trophic level and diving behaviour, the net value of which in these rare elasmosaurs turns out to be not noticeably different from that for the much commoner mosasaurs in the type Maastrichtian. Therefore, the rarity of elasmosaurs in the area probably reflects a primary near-absence of such reptiles during the latest Cretaceous, rather than a taphonomic artefact.

Ben Creisler | 30 Jun 05:14 2016
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[dinosaur] Heterodontosaurid remains from Cañadón Asfalto Formation, Argentina



Ben Creisler

A new paper:

Marcos G. Becerra, Diego Pol, Oliver W.M. Rauhut and Ignacio A. Cerda (2016)
New heterodontosaurid remains from the Cañadón Asfalto Formation: cursoriality and the functional importance of the pes in small heterodontosaurids.  
Journal of Paleontology (advance online publication)

New ornithischian remains reported here (MPEF-PV 3826) include two complete metatarsi with associated phalanges and caudal vertebrae, from the late Toarcian levels of the Cañadón Asfalto Formation. We conclude that these fossil remains represent a bipedal heterodontosaurid but lack diagnostic characters to identify them at the species level, although they probably represent remains of Manidens condorensis, known from the same locality. Histological features suggest a subadult ontogenetic stage for the individual. A cluster analysis based on pedal measurements identifies similarities of this specimen with heterodontosaurid taxa and the inclusion of the new material in a phylogenetic analysis with expanded character sampling on pedal remains confirms the described specimen as a heterodontosaurid. Finally, uncommon features of the digits (length proportions among nonungual phalanges of digit III, and claw features) are also quantitatively compared to several ornithischians, theropods, and birds, suggesting that this may represent a bipedal cursorial heterodontosaurid with gracile and grasping feet and long digits. In particular, the elongated non-terminal pedal phalanges and morphology of digit III resemble features present in arboreal birds, a unique condition found so far among ornithischians.
Ben Creisler | 29 Jun 18:00 2016
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[dinosaur] Eutherian evolutionary rates after K-Pg mass extinction (free pdf)


Ben Creisler


A new paper with a free pdf:



Thomas John Dixon Halliday, Paul Upchurch & Anjali Goswami (2016)
Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass extinction
Proceedings of the Royal Society B 283: 20153026
DOI: 10.1098/rspb.2015.3026
Free pdf:

The effect of the Cretaceous–Palaeogene (K–Pg) mass extinction on the evolution of many groups, including placental mammals, has been hotly debated. The fossil record suggests a sudden adaptive radiation of placentals immediately after the event, but several recent quantitative analyses have reconstructed no significant increase in either clade origination rates or rates of character evolution in the Palaeocene. Here we use stochastic methods to date a recent phylogenetic analysis of Cretaceous and Palaeocene mammals and show that Placentalia likely originated in the Late Cretaceous, but that most intraordinal diversification occurred during the earliest Palaeocene. This analysis reconstructs fewer than 10 placental mammal lineages crossing the K–Pg boundary. Moreover, we show that rates of morphological evolution in the 5 Myr interval immediately after the K–Pg mass extinction are three times higher than background rates during the Cretaceous. These results suggest that the K–Pg mass extinction had a marked impact on placental mammal diversification, supporting the view that an evolutionary radiation occurred as placental lineages invaded new ecological niches during the Early Palaeocene.

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News:








Ben Creisler | 29 Jun 08:13 2016
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[dinosaur] Moveable Museum to Mongolia project + Baron Nopsca + Arlington Archosaur Site + more



Ben Creisler


Some recent items:

Moveable Museum to Mongolia, project to bring dinosaur heritage to children of Mongolia




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Our ancestors evolved faster after dinosaur extinction



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Half a million visitors to see Tristan the T. rex in Berlin (in German)



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Bay of Fundy dinosaur digs



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Digging at Arlington Archosaur Site in Texas



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Mosasaur from Chile (in Spanish)



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Young boy helps discover new mammal from fossil in Fukui




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Diversity of horned dinosaur frills



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Determining dinosaur sexes


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Bird hip? Lizard hip? Beaks are better!

Bay of fundy


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Expansion of Sternberg Museum paleontology collection


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Ben Creisler | 29 Jun 00:54 2016
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[dinosaur] K-Pg impact winter in New Jersey + Triassic hothouse + Carboniferous tetrapod tracks + more



Ben Creisler


Some recent (and not so recent) mainly non-dino papers that may be of interest:

Johan Vellekoop, Selen Esmeray-Senlet, Kenneth G. Miller, James V. Browning, Appy Sluijs, Bas van de Schootbrugge, Jaap S. Sinninghe Damsté, and Henk Brinkhuis (2016)
Evidence for Cretaceous-Paleogene boundary bolide "impact winter" conditions from New Jersey, USA.
Geology (advance online publication)
doi:10.1130/G37961.1

Abrupt and short-lived "impact winter" conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been available for such a climatic perturbation. Here we perform high-resolution TEX86 organic paleothermometry on three shallow cores from the New Jersey paleoshelf, (northeastern USA) to assess the impact-provoked climatic perturbations immediately following the K-Pg impact and to place these short-term events in the context of long-term climate evolution. We provide evidence of impact-provoked, severe climatic cooling immediately following the K-Pg impact. This so-called "impact winter" occurred superimposed on a long-term cooling trend that followed a warm phase in the latest Cretaceous.



===

Mingsong Li, Chunju Huang, Linda Hinnov, James Ogg, Zhong-Qiang Chen, and Yang Zhang (2016)
Obliquity-forced climate during the Early Triassic hothouse in China.
Geology (advance online publication)
doi:10.1130/G37970.1

The start of the Mesozoic Era is marked by roughly 5 m.y. of Earth system upheavals, including unstable biotic recovery, repeated global warming, ocean anoxia, and perturbations in the global carbon cycle. Intervals between crises were comparably hospitable to life. The causes of these upheavals are unknown, but are thought to be linked to recurrent Siberian volcanism. Here, two marine sedimentary successions at Chaohu and Daxiakou (South China) are evaluated for paleoclimate change from astronomical forcing. In these sections, gamma-ray variations indicative of terrestrial weathering reveal enhanced obliquity cycling over prolonged intervals, characterized by a 32.8 k.y. periodicity with strong 1.2 m.y. modulations. These suggest a 22 h length of day and 1.2 m.y. interaction between the orbital inclinations of Earth and Mars. Comparing the 1.2 m.y. obliquity modulation cycles in these sections with Early Triassic records of global sea level, temperature, redox, and biotic evolution suggests that long-term astronomical forcing was involved in the repeated climatic and biotic upheavals that took place throughout the Early Triassic.

==

Matthew R. Stimson, Randall F. Miller, Spencer G. Lucas, Adrian F. Park & Steven J. Hinds (2016) 
Redescription of tetrapod trackways from the Mississippian Mabou Group, Lepreau Falls, New Brunswick, Canada.
Atlantic Geology 52:  1--19


Red-bed strata exposed at Lepreau Falls, southern New Brunswick, were originally interpreted as belonging to the Triassic Lepreau Formation. Poorly preserved tetrapod trackways within the strata were previously assigned to two ichnospecies; one to a new Triassic ichnospecies, Isocampe lepreauense Sarjeant and Stringer, and the other to Rhynchosauroides cf. R. franconicus (Heller). Both were attributed to reptiles. Subsequent mapping of the rocks and reassignment of the exposed strata at Lepreau Falls to the Mississippian Mabou Group prompted our re-examination of the trackway fossils. Isocampe lepreauense was described from a specimen block preserving three trackways and the original description was based on erroneous interpretation of extramorphological digit drags. Rhynchosauroides cf. R. franconicus was a tentative assignment in a letter accompanying a cast in the New Brunswick Museum, but was never formally published. We redescribe and re-interpret all the trackways as gait variations produced by temnospondyls, and most closely resemble the Carboniferous ichnotaxon Matthewichnus.

============

Matthew R. Stimson, Randall F. Miller & Spencer G. Lucas (2016)
Reassessment of vertebrate ichnotaxa from the Upper Carboniferous 'Fern Ledges', Lancaster Formation, Saint John, New Brunswick, Canada.
Atlantic Geology 52: 21 - 35


Vertebrate ichnotaxa described by George Frederic Matthew in 1910 from the Upper Carboniferous (Lower Pennsylvanian) ‘Fern Ledges’ of Saint John, New Brunswick, were dismissed as dubious trackways by previous authors. Thus, three new ichnospecies Matthew described appeared in the 1975 Treatise on Invertebrate Paleontology as “unrecognized or unrecognizable” and were mostly forgotten by vertebrate ichnologists. These traces include Hylopus (?) variabilis, Nanopus (?) vetustus and Bipezia bilobata. One ichnospecies, Hylopus (?) variabilis, here is retained as a valid tetrapod footprint ichnotaxon and reassigned to the ichnogenus Limnopus as a new combination, together with other poorly preserved specimens Matthew labeled, but never described. Nanopus (?) vetustus and Bipezia bilobata named by Matthew in the same paper, have been reexamined and remain as nomina dubia.


====

Patrick R. Getty (2016)
Megapezia longipes Willard and Cleaves 1930 from the Pennsylvanian Rhode Island Formation of Massachusetts: ichnotaxonomic status.
Atlantic Geology 52: 119 - 124


The type and only specimen of the ichnospecies Megapezia longipes, from the Pennsylvanian Rhode Island Formation of Plainville, Massachusetts, consists of two poorly defined tracks, one made by a manus and the other by a pes, rather than a single pedal imprint. Whereas the type species of Megapezia, Megapezia pineoi, has tetradactyl pedal imprints, the pes imprint of Megapezia longipes is pentadactyl, a feature that precludes assignment to this ichnogenus. Rather, the tracks share two characteristics with the ichnogenus Matthewichnus, namely elongate digits II and III on the manus, and a pes imprint oriented anterolaterally to the manus imprint, and are thus tentatively reassigned to that ichnogenus. Cf. Matthewichnus longipes is retained as a separate ichnospecies pending the collection of additional ma-terial that can be compared with other species within the ichnogenus. With the tentative reassignment of the Plainville tracks to Matthewichnus, Megapezia becomes monospecific and is no longer recorded in New England. The tracks are the first known occurrence of Matthewichnus from this region.

==

Free pdf:

Jennifer A. M. Graves (2016)
De novo sex chromosomes and drastic rearrangements may have posed reproductive barriers between monotremes, marsupials and placental mammals.
BioEssays (advance online publication)
DOI: 10.1002/bies.201600019

Comparative mapping and sequencing show that turnover of sex determining genes and chromosomes, and sex chromosome rearrangements, accompany speciation in many vertebrates. Here I review the evidence and propose that the evolution of therian mammals was precipitated by evolution of the male-determining SRY gene, defining a novel XY sex chromosome pair, and interposing a reproductive barrier with the ancestral population of synapsid reptiles 190 million years ago (MYA). Divergence was reinforced by multiple translocations in monotreme sex chromosomes, the first of which supplied a novel sex determining gene. A sex chromosome-autosome fusion may have separated eutherians (placental mammals) from marsupials 160 MYA. Another burst of sex chromosome change and speciation is occurring in rodents, precipitated by the degradation of the Y. And although primates have a more stable Y chromosome, it may be just a matter of time before the same fate overtakes our own lineage.

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Alexander Gehler, Philip D. Gingerich, and Andreas Pack (2016)
Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite.
Proceedings of the National Academy of Sciences (advance online publication)
doi: 10.1073/pnas.1518116113 

Significance

Our data suggest that the sudden rise in atmospheric temperature during the Paleocene–Eocene transition was not accompanied by highly elevated carbon dioxide concentrations >~2,500 ppm. Instead, the low 13C/12C isotope ratios during the Paleocene–Eocene Thermal Maximum were most likely caused by a significant contribution of methane to the atmosphere. We present data applying a newly developed partial pressure of CO2 proxy.


Abstract

The Paleocene–Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene–Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene–Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM.

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Ben Creisler | 29 Jun 01:14 2016
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[dinosaur] Fwd: K-Pg impact winter in New Jersey + Triassic hothouse + Carboniferous tetrapod tracks + more

Apparently this post was blocked. I'll try again with an editing change...

---------- Forwarded message ----------
From: Ben Creisler <bcreisler <at> gmail.com>
Date: Tue, Jun 28, 2016 at 3:54 PM
Subject: K-Pg impact winter in New Jersey + Triassic hothouse + Carboniferous tetrapod tracks + more
To: dinosaur-l <at> usc.edu




Ben Creisler


Some recent (and not so recent) mainly non-dino papers that may be of interest:

Johan Vellekoop, Selen Esmeray-Senlet, Kenneth G. Miller, James V. Browning, Appy Sluijs, Bas van de Schootbrugge, Jaap S. Sinninghe Damsté, and Henk Brinkhuis (2016)
Evidence for Cretaceous-Paleogene boundary bolide "impact winter" conditions from New Jersey, USA.
Geology (advance online publication)
doi:10.1130/G37961.1

Abrupt and short-lived "impact winter" conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been available for such a climatic perturbation. Here we perform high-resolution TEX86 organic paleothermometry on three shallow cores from the New Jersey paleoshelf, (northeastern USA) to assess the impact-provoked climatic perturbations immediately following the K-Pg impact and to place these short-term events in the context of long-term climate evolution. We provide evidence of impact-provoked, severe climatic cooling immediately following the K-Pg impact. This so-called "impact winter" occurred superimposed on a long-term cooling trend that followed a warm phase in the latest Cretaceous.



===

Mingsong Li, Chunju Huang, Linda Hinnov, James Ogg, Zhong-Qiang Chen, and Yang Zhang (2016)
Obliquity-forced climate during the Early Triassic hothouse in China.
Geology (advance online publication)
doi:10.1130/G37970.1

The start of the Mesozoic Era is marked by roughly 5 m.y. of Earth system upheavals, including unstable biotic recovery, repeated global warming, ocean anoxia, and perturbations in the global carbon cycle. Intervals between crises were comparably hospitable to life. The causes of these upheavals are unknown, but are thought to be linked to recurrent Siberian volcanism. Here, two marine sedimentary successions at Chaohu and Daxiakou (South China) are evaluated for paleoclimate change from astronomical forcing. In these sections, gamma-ray variations indicative of terrestrial weathering reveal enhanced obliquity cycling over prolonged intervals, characterized by a 32.8 k.y. periodicity with strong 1.2 m.y. modulations. These suggest a 22 h length of day and 1.2 m.y. interaction between the orbital inclinations of Earth and Mars. Comparing the 1.2 m.y. obliquity modulation cycles in these sections with Early Triassic records of global sea level, temperature, redox, and biotic evolution suggests that long-term astronomical forcing was involved in the repeated climatic and biotic upheavals that took place throughout the Early Triassic.

==

Matthew R. Stimson, Randall F. Miller, Spencer G. Lucas, Adrian F. Park & Steven J. Hinds (2016) 
Redescription of tetrapod trackways from the Mississippian Mabou Group, Lepreau Falls, New Brunswick, Canada.
Atlantic Geology 52:  1--19


Red-bed strata exposed at Lepreau Falls, southern New Brunswick, were originally interpreted as belonging to the Triassic Lepreau Formation. Poorly preserved tetrapod trackways within the strata were previously assigned to two ichnospecies; one to a new Triassic ichnospecies, Isocampe lepreauense Sarjeant and Stringer, and the other to Rhynchosauroides cf. R. franconicus (Heller). Both were attributed to reptiles. Subsequent mapping of the rocks and reassignment of the exposed strata at Lepreau Falls to the Mississippian Mabou Group prompted our re-examination of the trackway fossils. Isocampe lepreauense was described from a specimen block preserving three trackways and the original description was based on erroneous interpretation of extramorphological digit drags. Rhynchosauroides cf. R. franconicus was a tentative assignment in a letter accompanying a cast in the New Brunswick Museum, but was never formally published. We redescribe and re-interpret all the trackways as gait variations produced by temnospondyls, and most closely resemble the Carboniferous ichnotaxon Matthewichnus.

============

Matthew R. Stimson, Randall F. Miller & Spencer G. Lucas (2016)
Reassessment of vertebrate ichnotaxa from the Upper Carboniferous 'Fern Ledges', Lancaster Formation, Saint John, New Brunswick, Canada.
Atlantic Geology 52: 21 - 35


Vertebrate ichnotaxa described by George Frederic Matthew in 1910 from the Upper Carboniferous (Lower Pennsylvanian) ‘Fern Ledges’ of Saint John, New Brunswick, were dismissed as dubious trackways by previous authors. Thus, three new ichnospecies Matthew described appeared in the 1975 Treatise on Invertebrate Paleontology as “unrecognized or unrecognizable” and were mostly forgotten by vertebrate ichnologists. These traces include Hylopus (?) variabilis, Nanopus (?) vetustus and Bipezia bilobata. One ichnospecies, Hylopus (?) variabilis, here is retained as a valid tetrapod footprint ichnotaxon and reassigned to the ichnogenus Limnopus as a new combination, together with other poorly preserved specimens Matthew labeled, but never described. Nanopus (?) vetustus and Bipezia bilobata named by Matthew in the same paper, have been reexamined and remain as nomina dubia.


====

Patrick R. Getty (2016)
Megapezia longipes Willard and Cleaves 1930 from the Pennsylvanian Rhode Island Formation of Massachusetts: ichnotaxonomic status.
Atlantic Geology 52: 119 - 124


The type and only specimen of the ichnospecies Megapezia longipes, from the Pennsylvanian Rhode Island Formation of Plainville, Massachusetts, consists of two poorly defined tracks, one made by a manus and the other by a pes, rather than a single pedal imprint. Whereas the type species of Megapezia, Megapezia pineoi, has tetradactyl pedal imprints, the pes imprint of Megapezia longipes is pentadactyl, a feature that precludes assignment to this ichnogenus. Rather, the tracks share two characteristics with the ichnogenus Matthewichnus, namely elongate digits II and III on the manus, and a pes imprint oriented anterolaterally to the manus imprint, and are thus tentatively reassigned to that ichnogenus. Cf. Matthewichnus longipes is retained as a separate ichnospecies pending the collection of additional ma-terial that can be compared with other species within the ichnogenus. With the tentative reassignment of the Plainville tracks to Matthewichnus, Megapezia becomes monospecific and is no longer recorded in New England. The tracks are the first known occurrence of Matthewichnus from this region.

==

Alexander Gehler, Philip D. Gingerich, and Andreas Pack (2016)
Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite.
Proceedings of the National Academy of Sciences (advance online publication)
doi: 10.1073/pnas.1518116113 

Significance

Our data suggest that the sudden rise in atmospheric temperature during the Paleocene–Eocene transition was not accompanied by highly elevated carbon dioxide concentrations >~2,500 ppm. Instead, the low 13C/12C isotope ratios during the Paleocene–Eocene Thermal Maximum were most likely caused by a significant contribution of methane to the atmosphere. We present data applying a newly developed partial pressure of CO2 proxy.


Abstract

The Paleocene–Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene–Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene–Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM.

===






Ben Creisler | 28 Jun 17:35 2016
Picon

[dinosaur] Cretaceous baby bird wings preserved in Burmese amber (free pdf)


Ben Creisler


A new paper in open access:

Lida Xing, Ryan C. McKellar, Min Wang, Ming Bai, Jingmai K. O’Connor, Michael J. Benton, Jianping Zhang, Yan Wang, Kuowei Tseng, Martin G. Lockley, Gang Li, Weiwei Zhang & Xing Xu (2016)
Mummified precocial bird wings in mid-Cretaceous Burmese amber.
Nature Communications 7: 12089 
doi:10.1038/ncomms12089

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.

==

News:





Poekilopleuron | 28 Jun 12:25 2016
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[dinosaur] Elongated theropod footprints from Paluxy River

Good day,

I would like to ask if there is already a scientific consensus about strange elongated theropod footprints from the Paluxy River? They were once though to be a remnant of upright standing tail-less form of theropod. Thank you, Tom

Gmane