[dinosaur] Late Permian-Early Jurassic vertebrate tracks + end-Guadalupian extinction + Varanus cranial kinesis + more

Ben Creisler
[email protected]

Some recent non-dino papers:

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

Ignacio Díaz-Martínez, Paolo Citton, Silvina de Valais, Carlos
Cónsole-Gonella & Santiago N.González (2019)
Late Permian-Early Jurassic vertebrate tracks from Patagonia:
biochronological inferences and relationships with southern African realms.
Journal of African Earth Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.jafrearsci.2019.103619&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=9SjHlJp8Y7rfaTYwOyw_TcjptZk5AcQVV6Obeph3Mxs&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_pii_S1464343X19302742&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=AfIuPr68Wfje_GTdst2fsAgL9_cN8c63bu91cpdGz3k&e= 

HIGHLIGHTS

Geo-palaeontological data suggest the Vera Formation is composed of two
sequences
The Lopingian-Early Jurassic tetrapod track record from southern Gondwana
is highlighted
Data suggest correlations between Patagonia and southern Africa
Trackmakers in both realms of southern Gondwana are homogeneously
distributed

Abstract

In recent years, new studies about vertebrate tracks found in the late
Permian-Triassic Los Menucos Complex and Early Jurassic Marifil Volcanic
Complex (Río Negro province, Patagonia, Argentina) have been published. In
those studies, the chronostratigraphic information of each track-bearing
unit has been discussed and the relationships between the record from
Patagonia and southern Africa have been highlighted. With the aim of
deepening both subjects, the biochronological and palaeobiogeographical
information of the main ichnotaxa found in the lower Mesozoic units of
Patagonia, Dicynodontipus, Pentasauropus and Anomoepus-like tracks, have
been analysed. Moreover, the updated chronological data from the Vera
Formation, Los Menucos Complex, in the Tscherig and Yancaqueo farm areas,
and from the Marifil Volcanic Complex near Perdomo farm, have been studied.
The entire biochronological, chronological and tectonic evidence suggests
that within the Los Menucos Complex there are two sequences: a lower one,
Wuchiapingian-Olenekian in age, near the Tscherig farm and bearing
Dicynodontipus tracks, and an upper sequence of Anisian-Rhaetian (?Norian)
age, in the Yancaqueo farm and bearing Pentasauropus tracks. This suggests
that the rocks historically defined as Vera Formation have different ages
in different areas and span a longer time interval than previously thought.
In the case of the Anomoepus-like tracks found in the Marifil Volcanic
Complex, the biochronological and geological data are consistent with an
Early Jurassic age. According to ichnological information and geological
background we propose a correlation between Patagonia and southern Africa
constrained in three main phases: 1. Lopingian to Early Triassic, Vera
Formation (Tscherig farm) and Balfour Formation, respectively; 2. Middle to
Late Triassic, Vera Formation (Yancaqueo farm) and lower Elliot Formation,
respectively; and 3. Early Jurassic, Marifil Volcanic Complex and upper
Elliot Formation, respectively. In addition, this correlation is supported
by a similarity in palaeoclimatic settings that allow inferring a
homogeneous distribution of trackmakers in both realms of southern
Gondwana. Finally, the palaeobiogeographic information of the studied
ichnotaxa and their putative trackmakers is consistent and shows an
extensive distribution, during a geotectonic moment with most of the
continents assembled forming Pangaea.

====

Michael R. Rampino & Shu-Zhong Shen (2019)
The end-Guadalupian (259.8 Ma) biodiversity crisis: the sixth major mass
extinction?
Historical Biology (advance online publication)
DOI: 10.1080/08912963.2019.1658096
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.tandfonline.com_doi_full_10.1080_08912963.2019.1658096&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=MCw0-VFVDPVhc9dlOvVWj86NrTcr5o52JieEeaua3Mk&e= 

The modern loss of species diversity has been labelled the 'sixth
extinction' subsequent to the five major mass extinctions widely recognised
in the Phanerozoic geologic record -- the end-Ordovician (443.8 Ma), the
Late Devonian (372.2 Ma), end-Permian (251.9 Ma), end-Triassic (201.4 Ma)
and end-Cretaceous (66 Ma) events. Rankings in terms of numbers of genera
suffering extinction, and especially in terms of ecological impact,
however, put the end-Guadalupian (end-Capitanian) (259.8 Ma) extinction
event in the same category with the other major mass extinctions. Thus,
there were apparently six major Phanerozoic mass extinctions, and the
current loss of species should perhaps be called the 'seventh extinction'.

=====

Alec T. Wilken, Kevin M. Middleton, Kaleb C. Sellers, Ian N. Cost & Casey
M. Holliday (2019)
The roles of joint tissues and jaw muscles in palatal biomechanics of the
Savannah monitor (Varanus exanthematicus) and their significance for
cranial kinesis.
Journal of Experimental Biology jeb.201459
doi: 10.1242/jeb.201459
https://urldefense.proofpoint.com/v2/url?u=https-3A__jeb.biologists.org_content_early_2019_08_30_jeb.201459&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=FgktIYHu6YAw4KmkpUxaLJnZB0zGi5ae3pyltL9Lcwg&e= 

Many vertebrates exhibit cranial kinesis, or movement between bones of the
skull and mandible other than at the jaw joint. Many kinetic species
possess a particular suite of features to accomplish this movement,
including flexible cranial joints and protractor musculature. Whereas the
musculoskeletal anatomy of these kinetic systems is well understood, how
these joints are biomechanically loaded, how different soft tissues affect
joint loading and kinetic capacity, and how the protractor musculature
loads the skull remain poorly understood. Here we present a Finite Element
Model of the savannah monitor, Varanus exanthematicus, a modestly kinetic
lizard, to better elucidate the roles of soft tissue in mobile joints and
protractor musculature on cranial loading. We describe the 3D resultants of
jaw muscles and the histology of palatobasal, otic and jaw joints. We
tested the effects of joint tissue types, bite point, and muscle loads to
evaluate the biomechanical role of muscles on the palate and braincase. We
found the jaw muscles have significant mediolateral components that can
impart stability across palatocranial joints. We found articular tissues
affect the magnitude of strains experienced around the palatobasal and otic
joints. We found that without protractor muscle loading, the palate,
quadrate and braincase experience higher strains suggesting this muscle
helps insulate the braincase and palatoquadrate from high loads. Finally,
we found the cross-sectional properties of the bones of Varanus
exanthematicus are well suited for performing under torsional loads. These
findings suggest that torsional loading regimes may have played a more
important role in the evolution of cranial kinesis in lepidosaurs than
previously appreciated.

===

Free pdf:

Alessandro Palci, Roger S. Seymour, Cao Van Nguyen, Mark N. Hutchinson,
Michael S. Y. Lee and Kate L. Sanders (2019)
Novel vascular plexus in the head of a sea snake (Elapidae, Hydrophiinae)
revealed by high-resolution computed tomography and histology.
Royal Society Open Science 6(9): 191099.
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1098_rsos.191099&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=AUlxTCdUz1TeT0aHFRUoUwlLQP9H8l3-Sm32TqEmW1E&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_10.1098_rsos.191099&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=7iL30aF-iYGIBWWu9NZoLKIECf4Yh9134BmB5bPz_z0&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_pdf_10.1098_rsos.191099&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=H0JNHkQPE7RZGnIzVGbn3jtVvDVjz7rpzwGcbSmON2o&e= 


Novel phenotypes are often linked to major ecological transitions during
evolution. Here, we describe for the first time an unusual network of large
blood vessels in the head of the sea snake Hydrophis cyanocinctus. MicroCT
imaging and histology reveal an intricate modified cephalic vascular
network (MCVN) that underlies a broad area of skin between the snout and
the roof of the head. It is mostly composed of large veins and sinuses and
converges posterodorsally into a large vein (sometimes paired) that
penetrates the skull through the parietal bone. Endocranially, this blood
vessel leads into the dorsal cerebral sinus, and from there, a pair of
large veins depart ventrally to enter the brain. We compare the condition
observed in H. cyanocinctus with that of other elapids and discuss the
possible functions of this unusual vascular network. Sea snakes have low
oxygen partial pressure in their arterial blood that facilitates cutaneous
respiration, potentially limiting the availability of oxygen to the brain.
We conclude that this novel vascular structure draining directly to the
brain is a further elaboration of the sea snakes' cutaneous respiratory
anatomy, the most likely function of which is to provide the brain with an
additional supply of oxygen.

News:

https://urldefense.proofpoint.com/v2/url?u=https-3A__theconversation.com_deep-2Dbreath-2Dthis-2Dsea-2Dsnake-2Dgathers-2Doxygen-2Dthrough-2Dits-2Dforehead-2D122784&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=vdJce1mc7wOHn4ARlEKAXswz9XbvNY6a-WV_ytixSVY&e= 
===


Claire Dobson,  Sam Giles,  Zerina Johanson,  Jeff Liston & Matt Friedman
(2019)
Cranial osteology of the Middle Jurassic (Callovian) Martillichthys
renwickae (Neopterygii, Pachycormiformes) with comments on the evolution
and ecology of edentulous pachycormiforms.
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1002_spp2.1276&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=4mazpvrmZyMAsPRe-1sE9tkfLQOr7AT5hN5R4dAyNPk&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_abs_10.1002_spp2.1276&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=Gels63_1KpIZHz97GoXl_dEkiY-yUE62M6xrtv2_0h8&s=ZH10ofdNAsNeERQu2oGlMfksIiEGAyVzuyp6KWcirIo&e= 

Our understanding of the ecology and phylogenetic relationships of
Pachycormiformes, a group of Mesozoic stem teleosts including the iconic
Leedsichthys, has often been hindered by a lack of comprehensive
morphological information. Micro‐CT scanning of an articulated, although
flattened, cranium of the edentulous Martillichthys renwickae from the
Middle Jurassic (Callovian) Oxford Clay of the UK reveals previously
unknown internal details of the most complete suspension‐feeding
pachycormiform skull known, including the palate, braincase and branchial
skeleton. The latter preserves gill rakers with elongate, pointed
projections similar to those of Asthenocormus, in contrast to the finer
fimbriations associated with Leedsichthys. We also reinterpret some
previously described features, including dermal bone patterns of the snout,
skull roof and lower jaw, and the morphology of the ventral hyoid arch.
These new anatomical data reinforce the phylogenetic placement of
Martillichthys as part of the Jurassic clade of edentulous pachycormiforms.
The elongate skull geometry of these Jurassic taxa is strikingly similar to
that of Ohmdenia, the sister taxon to edentulous pachycormiforms, but
contrasts sharply with the morphology of the Late Cretaceous edentulous
pachycormiform Bonnerichthys, raising questions over the phylogenetic
relationships among these taxa. Most significantly, Martillichthys shows
specialized characters with a restricted phylogenetic distribution among
suspension‐feeding pachycormiforms, including the distinctive gill rakers
and a greatly extended occipital stalk. Our analysis of Martillichthys
supports past interpretations of a close relationship with Asthenocormus,
and provides a model for interpreting the less complete remains of other
members of this enigmatic group of fishes.

====
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