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[dinosaur] Arboroharamiya and evolution of mammalian middle ear + Antarctic K-Pg extinction + fossil vertebrate taphonomy




Ben Creisler
bcreisler@gmail.com


Some recent non-dino papers that may be of interest:


Jin Meng, Shundong Bi, Xiaoting Zheng and Xiaoli Wang (2016)
Ear ossicle morphology of the Jurassic euharamiyidan Arboroharamiya and evolution of mammalian middle ear.
Journal of Morphology
DOI: 10.1002/jmor.20565
http://onlinelibrary.wiley.com/doi/10.1002/jmor.20565/abstract


The middle ear bones of Mesozoic mammals are rarely preserved as fossils and the morphology of these ossicles in the earliest mammals remains poorly known. Here, we report the stapes and incus of the euharamiyidan Arboroharamiya from the lower Upper Jurassic (∼160 Ma) of northern China, which represent the earliest known mammalian middle ear ossicles. Both bones are miniscule in relation to those in non-mammalian cynodonts. The skull length/stapedial footplate diameter ratio is estimated as 51.74 and the stapes length as the percentage of the skull length is 4%; both numbers fall into the stapes size ranges of mammals. The stapes is "rod-like" and has a large stapedial foramen. It is unique among mammaliaforms in having a distinct posterior process that is interpreted as for insertion of the stapedius muscle and homologized to the ossified proximal (stapedial) end of the interhyal, on which the stapedius muscle attached. The incus differs from the quadrate of non-mammalian cynodonts such as morganucodontids in having small size and a slim short process. Along with lack of the postdentary trough and Meckelian groove on the medial surface of the dentary, the ossicles suggest development of the definitive mammalian middle ear (DMME) in Arboroharamiya. Among various higher-level phylogenetic hypotheses of mammals, the one we preferred places “haramiyidans” within Mammalia. Given this phylogeny, development of the DMME took place once in the allotherian clade containing euharamiyidans and multituberculates, probably independent to those of monotremes and therians. Thus, the DMME has evolved at least three times independently in mammals. Alternative hypothesis that placed "haramiyidans" outside of Mammalia would require independent acquisition of the DMME in multituberculates and euharamiyidans as well as parallel evolution of numerous derived similarities in the dentition, occlusion pattern, mandibles, cranium, and postcranium between the two groups and between "haramiyidans" and other mammals.

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Lorenzo Marchetti (2016)

New occurrences of tetrapod ichnotaxa from the Permian Orobic Basin (Northern Italy) and critical discussion of the age of the ichnoassociation.

Papers in Palaeontology (advance online publication)

DOI: 10.1002/spp2.1045

http://onlinelibrary.wiley.com/doi/10.1002/spp2.1045/abstract



The late Cisuralian (Artinskian–Kungurian) is a key time interval for Permian tetrapod evolution. In all the main low-latitude Pangean sites, the fossil footprint record clearly shows a diversification and dispersal of non-synapsid amniote tracks compared to the early Cisuralian (Asselian–Sakmarian). However, data on latest Cisuralian (i.e. late Kungurian) sites are quite fragmentary. A new ichnotaxonomic study was carried out in the central part of the Orobic Basin, where the highly-fossiliferous Pizzo del Diavolo formation crops out and can potentially cover this gap in knowledge. The following tetrapod ichnogenera were identified: Amphisauropus, Batrachichnus, cf. Dimetropus, Dromopus, Erpetopus, Hyloidichnus, Limnopus, cf. Merifontichnus and Varanopus; they can be attributed to seymouriamorph and temnospondyl amphibians; pelycosaur synapsids; and diapsid, parareptile and captorhinid reptiles. Dimetropus and Merifontichnus are identified for the first time in the Permian of Italy. The ichnoassociation, in agreement with the radiometric dating of the underlying Cabianca formation, suggests a late Kungurian (latest Cisuralian) age for the Pizzo del Diavolo formation. It includes the youngest and most diverse non-synapsid amniote ichnofauna of the Cisuralian with five different ichnogenera and possibly six ichnospecies, and thus constitutes a key area for the study of eureptile and parareptile dispersal at low latitudes 

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Michael Stein, Suzanne J. Hand & Michael Archer (2016)

A new crocodile displaying extreme constriction of the mandible, from the late Oligocene of Riversleigh, Australia.

Journal of Vertebrate Paleontology (advance online publication)

DOI: 10.1080/02724634.2016.1179041.

http://www.tandfonline.com/doi/full/10.1080/02724634.2016.1179041

 

A new fossil crocodile, Ultrastenos willisi, is described from a cranium and postcranial materials collected from the Riversleigh World Heritage Area, northwestern Queensland, Australia. The mandible displays pronounced anterior constriction, approaching that seen in the extant gharial, Gavialis gangeticus, and false gharial, Tomistoma schlegelii. As such, U. willisi potentially filled the ecomorphological niche associated with longirostry that has been previously unaccounted for in Riversleigh's Oligo–Miocene crocodile fauna. The pronounced constriction and features of the posterior cranium further distinguish U. willisi from all other known crocodiles, including the only reported Australian Oligo–Miocene longirostral crocodile, Harpacochampsa camfieldensis, from Bullock Creek in the Northern Territory. Ultrastenos willisi is recognized as a new genus and species assigned to subfamily Mekosuchinae on the basis of phylogenetic analysis.



http://zoobank.org/urn:lsid:zoobank.org:pub:7C6DC891-BD9C-4F84-AF7D-409A4A8C720D


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In open access:

James D. Witts, Rowan J. Whittle, Paul B. Wignall, J. Alistair Crame, Jane E. Francis, Robert J. Newton, Vanessa C. Bowman (2016) 
Macrofossil evidence for a rapid and severe Cretaceous–Paleogene mass extinction in Antarctica. 
Nature Communications 7: 11738 
doi:10.1038/ncomms11738
http://www.nature.com/ncomms/2016/160526/ncomms11738/full/ncomms11738.html


Debate continues about the nature of the Cretaceous–Paleogene (K–Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K–Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous–Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

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News


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Saradee Sengupta , Dhurjati Prasad Sengupta & Saswati Bandyopadhyay (2016)

Stratigraphy of the upper Gondwana formations around Sohagpur, western part of the Satpura Gondwana Basin, Central India.

Journal of the Geological Society of India 87(5): 503-519

DOI: 10.1007/s12594-016-0424-7

 

http://link.springer.com/article/10.1007/s12594-016-0424-7

The present work provides a detailed lithological map of the western part of the Satpura basin around Sohagpur and reports the presence of new archosauromorph fossil bones from that region. The study area is dominated by the Bagra Formation along with a narrow patch of the underlying upper part of the Denwa Formation. The lower Denwa and the underlying Pachmarhi formations are absent here. The presence of the Pachmarhi Formation, as a tongue shaped area, as mapped by Crookshank (1936) is discarded in this study on the basis of lithology and petrographic analyses, instead the presence of the Bagra Formation is suggested in this area. A comparison of the lithologies and the vertebrate faunas of the upper Gondwana formations between eastern and western part of the basin has been carried out for the first time. The comparison indicates that the Denwa Formation present in the western sector represents only the topmost part of the formation while the complete succession of Denwa is preserved in the eastern sector. The Bagra Formation in the western sector documents the presence of sheet-like sandstone bodies unlike the eastern part. The vertebrate fauna of the eastern part is dominated by temnospondyl amphibians while that of the western part is dominated by archosauromorph. The vertebrate fossils of upper part of Denwa Formation, found from similar lithologies in west and east though, have differences in the amount of transportation before their burial.


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Patrick J. Orr, Laetitia B. Adler, Susan R. Beardmore, Heinz Furrer, Maria E. McNamara, Enrique Peñalver-Mollá & Ragna Redelstorff (2016)

"Stick 'n' peel": Explaining unusual patterns of disarticulation and loss of completeness in fossil vertebrates.

Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)

doi:10.1016/j.palaeo.2016.05.024

http://www.sciencedirect.com/science/article/pii/S003101821630164X

 

Highlights


Most fossil vertebrate skeletons are incomplete and/or disarticulated; this is often the result of disturbance by water currents.

Existing taphonomic models emphasise the size, shape and density of bones when determining whether or not they will be transported in currents.

Decay fluids leaking from a carcass stick it to the substrate; bones on the downward-facing side are preferentially affected.

If subjected to a current, these bones are less likely to be removed than others; this anomaly, 'stick 'n peel', can impact significantly on the skeletal taphonomy of a carcass.

The phenomenon is common in the fossil record and can be identified retrospectively by a characteristic set of unusual taphonomic features.


Abstract


Few fossil vertebrate skeletons are complete and fully articulated. Various taphonomic processes reduce the skeletal fidelity of decaying carcasses, the effects of most of which are reasonably well understood. Some fossil vertebrates, however, exhibit patterns of disarticulation and loss of completeness that are difficult to explain. Such skeletons are one of two variants. They are incomplete, often markedly so, but the preserved parts are highly articulated. Alternatively, they are complete, or nearly so, but articulation varies markedly between parts of the body. A characteristic feature is the absence of skeletal elements that, on the basis of their larger size and/or greater density, would be predicted to be present. Here we erect a model, termed "stick 'n' peel", that explains how these distinctive patterns originate. The model emphasizes the role of decay products, especially fluids released from the carcass while resting on the sediment surface. These fluids permeate the sediment below and around the carcass. As a result, skeletal elements on the downward facing side of the carcass become adhered to the sediment surface, and are less likely to be remobilized as a result of current activity than others. The pattern of articulation and, especially, completeness is thus not what would be predicted on the basis of the size, shape and density of the skeletal elements. The effects of stick ‘n’ peel are difficult to predict a priori. Stick ‘n’ peel has been identified in vertebrate fossils in lacustrine and marine settings and is likely to be a common feature of the taphonomic history of many vertebrate assemblages. Specimens becoming adhered to the substrate may also explain the preservation in situ of the multi-element skeletons of invertebrates such as echinoderms, and integumentary structures such as hair and feathers in exceptionally preserved fossils.