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Tholodus from Russia + freshwater teleosaurids



Ben Creisler
bcreisler@gmail.com

Recent non-dino reptile papers not yet mentioned:

M. S. Arkhangelsky, N. G. Zverkov, & Yu. D. Zakharov (2016)
On the first reliable find of the genus Tholodus (Reptilia:
Ichthyopterygia) in the Asian peripheral area of the Panthalassic
ocean.
Paleontological Journal 50(1): 78-86
DOI: 10.1134/S0031030115060040
http: // link.springer.com/article/10.1134/S0031030115060040

pdf:

https: // 
www.academia.edu/21668479/On_the_First_Reliable_Find_of_the_Genus_Tholodus_Reptilia_Ichthyopterygia_in_the_Asian_Peripheral_Area_of_the_Panthalassic_Ocean

Until recently, Tholodus, a rare ichthyosaur with spherical tooth
crowns of the pressing–crushing type, has only been known from the
Middle Triassic (Anisian) beds of Western Europe. A record of Tholodus
remains in the Karazin Formation (Middle Anisian) of southern Primorye
(Russian Far East) significantly expands the range of these reptiles.


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Freshwater teleosaurids

Jeremy E. Martin, Uthumporn Deesri, Romain Liard, Athiwat
Wattanapituksakul, Suravech Suteethorn, Komsorn Lauprasert, Haiyan
Tong, Eric Buffetaut, Varavudh Suteethorn, Guillaume Suan, Philippe
Telouk and Vincent Balter (2016)
Strontium isotopes and the long-term residency of thalattosuchians in
the freshwater environment.
Paleobiology 42(1): 143-156
doi:  http: // orcid.org/0000-0001-9159-645X
http: // 
journals.cambridge.org/action/displayAbstract?fromPage=online&aid=10184791&fulltextType=RA&fileId=S0094837315000421

pdf:

https: // 
www.researchgate.net/publication/288020286_Strontium_isotopes_and_the_long-term_residency_of_thalattosuchians_in_the_freshwater_environment

Thalattosuchians are crocodylomorphs mainly known from marine strata
of Early Jurassic to Early Cretaceous age. They represent the earliest
crocodylomorph radiation to an aquatic habitat and their evolutionary
history offers very few records from freshwater settings. Here, we
report several exquisitely preserved thalattosuchian skulls attributed
to a derived teleosaurid from a pedogenic horizon located at the base
of a fluvial series of alternating silts and sandstones of the Phu
Kradung Formation (Upper Jurassic) of northeastern Thailand. Using
laser ablation multicollector inductively coupled mass spectrometry
(MC-ICP-MS) on tooth enamel and dentine, we measured isotopic ratios
of strontium (87Sr/86Sr) to test the habitat of these teleosaurids. In
addition, Sr concentrations of the dental tissues were estimated from
the calibrated signal intensities of the Sr isotope measurements. The
dataset includes bioapatite (teeth or scales) of eight terrestrial and
five aquatic vertebrates. Theropods exhibit lower Sr concentrations
both in enamel and dentine compared to others groups, a pattern in
accordance with the calcium biopurification process, which predicts
that Sr concentrations in the body of vertebrates decrease up the
trophic chain. It also excludes the possibility that diagenesis has
completely overprinted the Sr isotope compositions of the fossil
assemblage, which exhibits a homogeneous 87Sr/86Sr signature above the
Late Jurassic seawater value. Values for teleosaurid teeth are in the
range of other values for vertebrates in the continental assemblage
and imply that these crocodylomorphs did not migrate between
freshwater and marine habitats at least in the time constraint of the
mineralizing tooth. This result represents the first demonstration
that a population of teleosaurids was established for a prolonged time
in a freshwater environment. Whether the ability of teleosaurids to
inhabit freshwater habitats is a secondary adaptation or whether it is
plesiomorphic and inherited from freshwater ancestors is discussed.