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[dinosaur] Marine turtle evolution + Taphrosphys from Angola

Ben Creisler

New papers:

Serjoscha W. Evers & Roger B. J. Benson (2018)
A new phylogenetic hypothesis of turtles with implications for the timing and number of evolutionary transitions to marine lifestyles in the group.
Palaeontology (advance online publication)
doi: https://doi.org/10.1111/pala.12384

Data for this study (including CT volume files and mesh files for segmented models) are available in MorphoSource: http://www.morphosource.org/Detail/ProjectDetail/Show/project_id/462

Additional data (files and instructions for Templeton's tests; files and R code for similarity analysis; appendices including the characterâtaxon matrix, the character list and the character optimization) are available in the Dryad Digital Repository: https://doi.org/10.5061/dryad.2pb356h.

Evolutionary transitions to marine habitats occurred frequently among Mesozoic reptiles. Only one such clade survives to the present: sea turtles (Chelonioidea). Other marine turtles originated during the Mesozoic, but uncertain affinities of key fossils have obscured the number of transitions to marine life, and the timing of the origin of marine adaptation in chelonioids. Phylogenetic studies support either a highlyâinclusive chelonioid totalâgroup including fossil marine clades from the Jurassic and Cretaceous (e.g. protostegids, thalassochelydians, sandownids) or a less inclusive chelonioid totalâgroup excluding those clades. Under this paradigm, these clades belong outside Cryptodira, and represent at least one additional evolutionary transition to marine life in turtles. We present a new phylogenetic hypothesis informed by high resolution computed tomographic data of living and fossil taxa. Besides a wellâsupported Chelonioidea, which includes protostegids, we recover a previously unknown clade of stemâgroup turtles, Angolachelonia, which includes the Late Jurassic thalassochelydians, and the CretaceousâPalaeogene sandownids. Accounting for the Triassic Odontochelys, our results indicate three independent evolutionary transitions to marine life in nonâpleurodiran turtles (plus an additional twoâthree in pleurodires). Among all independent origins of marine habits, a pelagic ecology only evolved once, among chelonioids. All turtle groups that independently invaded marine habitats in the JurassicâCretaceous (chelonioids, angolachelonians, bothremydid pleurodires) survived the CretaceousâPalaeogene mass extinction event. This highlights extensive survival of marine turtles compared to other marine reptiles. Furthermore, deeplyânested clades such as chelonioids are found by the middle Early Cretaceous, suggesting a rapid diversification of crownâgroup turtles during the Early Cretaceous.


AdÃn PÃrez GarcÃa, Florias Mees & Thierry Smith (2018)
Shell anatomy of the African Paleocene bothremydid turtle Taphrosphys congolensis and systematic implications within Taphrosphyini.
Historical Biology (advance online publication)
DOI: 10.1080/08912963.2018.1497023

The bothremydid pleurodiran turtle Taphrosphys congolensis is a member of Taphrosphyina from the Paleocene of the Cabinda Province (Congo Basin, Angola). Very few specimens corresponding to elements of its shell have been so far figured. Abundant unpublished remains are analyzed in this paper. As a consequence, several regions of the shell are figured and characterized here for the first time, and intraspecific variability is recognized for several characters. Previous authors proposed some putative differences between the shells of Taphrosphys congolensis and the North American Paleocene Taphrosphys sulcatus. The increase in the knowledge about the shell of this African form allows us to refute most of them, the shell of both forms being recognized as more similar than previously identified. Thus, the identification of the genus Taphrosphys as restricted to three forms (i.e. the skull taxon Taphrosphys ippolitoi, and the skull and shell forms T. congolensis and T. sulcatus) is supported, and the record unquestionably attributable to this genus is modified from the Upper CretaceousâEocene lapse of time to the Paleocene exclusively.