[dinosaur] Saxochelys, new baenid turtle from Cretaceous Hell Creek + last mammoth extinctions

Ben Creisler
[email protected]


Some non-dino papers:


Saxochelys gilberti gen. et sp. nov.

Tyler R. Lyson, Jacob L. Sayler & Walter G. Joyce (2019)
A new baenid turtle, Saxochelys gilberti, gen. et sp. nov., from the
uppermost Cretaceous (Maastrichtian) Hell Creek Formation: sexual
dimorphism and spatial niche partitioning within the most speciose group of
Late Cretaceous turtles.
Journal of Vertebrate Paleontology Article: e1662428
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1080_02724634.2019.1662428&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=MP8OMkXoMdhXxQPi6Wiro8CcEFqGTpPeM_87bo-7vv0&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.tandfonline.com_doi_full_10.1080_02724634.2019.1662428&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=F-PnVlwnQ7H8hj1l6yIdJMUOO2jzyeuAgpvpFylvnbM&e= 


The uppermost Cretaceous (Maastrichtian) Hell Creek Formation in North
America has yielded a diverse assemblage of fossil turtles dominated by
baenids. A population of over 30 individual skeletons from the Hell Creek
Formation of North Dakota comprises a new baenid turtle, Saxochelys
gilberti, increasing the number of recognized Hell Creek turtles to at
least 26, 11 of which are baenids. Saxochelys gilberti is differentiated
from all other baenids based on the presence of a nuchal scale, finely
sculptured shell, absence of an omega-shaped femoral-anal sulcus, presence
of an omega-shaped extragular-humeral sulcus, a cavum tympani that is
relatively smaller than the diameter of the orbit, presence of a robust
single scale on the posteromedial portion of the parietals, and jugal
exclusion from the orbital margin. Two distinct plastral morphologies,
concave (N = 8) and flat (N = 9), are interpreted as representing male and
female individuals, respectively. A ca. 10% size difference between the
sexes indicates that S. gilberti is a sexually size-dimorphic turtle with
larger females. This suggests female mate choice in this baenid turtle. A
referred S. gilberti skeleton from above the Cretaceous–Paleogene boundary
provides evidence for the survival of yet another species of turtle across
this extinction event. The type locality of S. gilberti is close both
stratigraphically and geographically to another locality consisting of a
completely different assortment of baenid species, suggesting a fine degree
of spatial niche partitioning in baenid turtles that may help explain the
extremely high diversity of the group within the Hell Creek Formation.

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Also might be interest...

Free pdf:

John B. Iverson, Peter V. Lindeman & Jeffrey E. Lovich (2019)
Understanding reproductive allometry in turtles: A slippery "slope".
Ecology and Evolution (advance online publication)
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1002_ece3.5697&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=7tzvJGN13SqYLL_22TaNBiC0UV9T4O1uMmOSGCMm9oA&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1002_ece3.5697&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=lb5e9kjq4TdHwWlcKObRhRwff-8F9xDVrvzv5CLwGDw&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_pdf_10.1002_ece3.5697&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=L4DUeIhmRZvqKMCYXOmnaOrIJqO6yyx46cZfWgmpv_o&e= 

Measures of reproductive output in turtles are generally positively
correlated with female body size. However, a full understanding of
reproductive allometry in turtles requires logarithmic transformation of
reproductive and body size variables prior to regression analyses. This
allows for slope comparisons with expected linear or cubic relationships
for linear to linear and linear to volumetric variables, respectively. We
compiled scaling data using this approach from published and unpublished
turtle studies (46 populations of 25 species from eight families) to
quantify patterns among taxa. Our results suggest that for log–log
comparisons of clutch size, egg width, egg mass, clutch mass, and pelvic
aperture width to shell length, all scale hypoallometrically despite
theoretical predictions of isometry. Clutch size generally scaled at ~1.7
to 2.0 (compared to an isometric expectation of 3.0), egg width at ~0.5
(compared to an expectation of 1.0), egg mass at ~1.1 to 1.3 (3.0), clutch
mass at ~2.5 to 2.8 (3.0), and pelvic aperture width at 0.8–0.9 (1.0). We
also found preliminary evidence that scaling may differ across years and
clutches even in the same population, as well as across populations of the
same species. Future investigators should aspire to collect data on all
these reproductive parameters and to report log–log allometric analyses to
test our preliminary conclusions regarding reproductive allometry in
turtles.

=====

Free pdf:

Laura Arppe,  Juha A. Karhu, Sergey Vartanyan, Dorothée G. Drucker, Heli
Etu-Sihvola & Hervé Bocherens (2019)
Thriving or surviving? The isotopic record of the Wrangel Island woolly
mammoth population
Quaternary Science Reviews 222: 105884
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1016_j.quascirev.2019.105884&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=sJopXv0X6xQaxUOa7YroZnZBU-mSlfifmgNlsYevGpY&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.sciencedirect.com_science_article_pii_S0277379119301398-3Fvia-253Dihub&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=cQJfAbsk32Bq3UWRc4sPXitJbSOAQxRgnH934rZJMn4&s=LXDawOgfcc0bVzHz7E0MBNqJLhMlmzSxDAgiZBKfS-Q&e= 

Highlights

No sign of habitat or forage deterioration in Wrangel Island mammoth
isotope levels.
Different energy economy compared to Siberian mammoths.
Increased weathering in mid-Holocene possibly led to freshwater quality
issues.
Short-term or catastrophic events are suggested as the cause of extinction.

Abstract

The world's last population of woolly mammoths (Mammuthus primigenius)
lived on Wrangel Island persisting well into the Holocene, going extinct at
ca. 4000 cal BP. According to the frequency of radiocarbon dated mammoth
remains from the island, the extinction appears fairly abrupt. This study
investigates the ecology of the Wrangel Island mammoth population by means
of carbon, nitrogen and sulfur isotope analyses. We report new isotope data
on 77 radiocarbon dated mammoth specimens from Wrangel Island and Siberia,
and evaluate them in relation to previously published isotope data for
Pleistocene mammoths from Beringia and lower latitude Eurasia, and the
other insular Holocene mammoth population from St. Paul Island. Contrary to
prior suggestions of gradual habitat deterioration, the nitrogen isotope
values of the Wrangel Island mammoths do not support a decline in forage
quality/quantity, and are in fact very similar to their north Beringian
forebears right to the end. However, compared to Siberian mammoths, those
from Wrangel Island show a difference in their energy economy as judged by
the carbon isotope values of structural carbonate, possibly representing a
lower need of adaptive strategies for survival in extreme cold. Increased
mid-Holocene weathering of rock formations in the central mountains is
suggested by sulfur isotope values. Scenarios related to water quality
problems stemming from increased weathering, and a possibility of a
catastrophic starvation event as a cause of, or contributing factor in
their demise are discussed.

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News

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