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[dinosaur] Cenozoic turtle papers with free pdfs: Tasbacka juvenile + Procolpochelys + Apalone + Trachemys

Ben Creisler

Some recent papers on Cenozoic turtles that are currently free:

Free pdf:

Johan Lindgren, Takeo Kuriyama, Henrik Madsen, Peter Sjövall, Wenxia Zheng, Per Uvdal, Anders Engdahl, Alison E. Moyer, Johan A. Gren, Naoki Kamezaki, Shintaro Ueno & Mary H. Schweitzer (2017)
Biochemistry and adaptive colouration of an exceptionally preserved juvenile fossil sea turtle.
Scientific Reports 7, Article number: 13324 (2017)

The holotype (MHM-K2) of the Eocene cheloniine Tasbacka danica is arguably one of the best preserved juvenile fossil sea turtles on record. Notwithstanding compactional flattening, the specimen is virtually intact, comprising a fully articulated skeleton exposed in dorsal view. MHM-K2 also preserves, with great fidelity, soft tissue traces visible as a sharply delineated carbon film around the bones and marginal scutes along the edge of the carapace. Here we show that the extraordinary preservation of the type of T. danica goes beyond gross morphology to include ultrastructural details and labile molecular components of the once-living animal. Haemoglobin-derived compounds, eumelanic pigments and proteinaceous materials retaining the immunological characteristics of sauropsid-specific β-keratin and tropomyosin were detected in tissues containing remnant melanosomes and decayed keratin plates. The preserved organics represent condensed remains of the cornified epidermis and, likely also, deeper anatomical features, and provide direct chemical evidence that adaptive melanism – a biological means used by extant sea turtle hatchlings to elevate metabolic and growth rates – had evolved 54 million years ago.


Free pdf:

Robert E. Weems  and K. Mace Brown  (2017)
More-complete remains of Procolpochelys charlestonensis (Oligocene, South Carolina), an occurrence of Euclastes (upper Eocene, South Carolina), and their bearing on Cenozoic pancheloniid sea turtle distribution and phylogeny.
Journal of Paleontology 91(6): 1228-1243

New and more-complete material of Procolpochelys charlestonensis Weems and Sanders, 2014 provides the first detailed information on the skull, jaw, and plastron of this species, which occurs in the Oligocene Ashley and Chandler Bridge formations near Charleston, South Carolina. This material allows a much more detailed comparison of this turtle with the co-occurring pancheloniid species Ashleychelys palmeri Weems and Sanders, 2014 and Carolinochelys wilsoni Hay, 1923a, as well as with its Miocene successor Procolpochelys grandaeva (Leidy, 1851). Fused dentaries, found in the Cooper River north of Charleston, belong to the pancheloniid genus Euclastes, previously known only from the Upper Cretaceous and Paleocene. This specimen, apparently from the upper Eocene Parkers Ferry Formation, expands the temporal range of this genus and indicates that Euclastes survived in the North Atlantic basin far longer than was previously known. These new finds, combined with previous records of fossil pancheloniid sea turtles, provide an improved picture of the temporal distribution, evolutionary trends, and likely phylogeny of pancheloniids from the Late Cretaceous to the present.


Free pdf:

Apalone amorense sp. nov.

Valdes, N., J. R. Bourque, and N. S. Vitek. 2017. 

A new soft-shelled turtle (Trionychidae, Apalone) from the Late Miocene of north-central Florida.

Bulletin of the Florida Museum of Natural History 55(6):117–138.


Trionychid fossils from the late Miocene (late Clarendonian) Love Bone Bed in Alachua County, Florida, are described as a single taxon that represents a new species, Apalone amorense sp. nov. A phylogenetic analysis recovers A. amorense as sister to all extant representatives of Apalone. The new species is relatively small at adult size compared to other species of Apalone and exhibits a mosaic of similarities with extant species of Apalone. It shares the presence of four plastral callosities, lack of surface contact between the jugal and parietal, and a mid-sized postorbital bar with A. ferox, and unfused hyo-hypoplastra (except in some older individuals where these fuse), variably open suprascapular fontanelles in all but the largest individuals, and dermal sculpturing similar to A. mutica and A. spinifera. The age and proposed phylogenetic position of A. amorense are consistent with previously published estimated divergence dates for the clade.


Free pdf:

 Mario Vargas-Ramírez, Carlos del Valle, Claudia P. Ceballos and Uwe Fritz (2017)

Trachemys medemi n. sp. from northwestern Colombia turns the biogeography of South American slider turtles upside down.


DOI: 10.1111/jzs.12179



South America was invaded by slider turtles (Trachemys spp.) twice, with one immigration wave estimated to have reached South America 8.6–7.1 million years ago (mya) and a second wave, 2.5–2.2 mya. The two widely disjunct South American subspecies of Trachemys dorbigni (northeastern and southern Brazil, Río de la Plata region of Argentina and Uruguay) are derived from the first dispersal pulse, while the two South American subspecies of Trachemys venusta (Colombia, Venezuela) originated from the second immigration event. We describe a new species of slider turtle from the lower Atrato river basin of Antioquia and Chocó departments, northwestern Colombia. This new species, the Atrato slider (Trachemys medemi n. sp.), is the first representative of the older immigration wave inhabiting northern South America. Using phylogenetic analyses of 3,242 bp of mitochondrial and 3,396 bp of nuclear DNA, we show that T. medemi is more closely related to T. dorbigni than to the geographically neighboring subspecies of Trachemys grayi and T. venusta from Central America and northern South America. The two subspecies of T. dorbigni are separated from the Atrato slider by the Andes and the Amazon Basin, and occur approximately 4,600 km and 3,700 km distant from T. medemi. According to molecular clock calculations, T. medemi diverged from the last common ancestor of the two subspecies of T. dorbigni during the Pliocene (4.1–2.8 mya), with T. dorbigni diversifying later (2.3–1.9 mya) in eastern South America beyond the Amazon basin. The divergence of the T. dorbigni subspecies overlaps with the estimated arrival of T. venusta in South America (2.5–2.2 mya). This time is characterized by massive climatic and environmental fluctuations with intermittent dispersal corridors in South America. According to their distribution, it seems likely that the ancestors of the extant subspecies of T. dorbigni dispersed along the eastern corridor, leaving a relict population northwest of the Andes with T. medemi. The distribution range of T. medemi is surrounded by taxa derived from the second southern range expansion of slider turtles, so that it can be concluded that T. venusta circumvented the habitats occupied by the ancestors of the Atrato slider when entering South America.

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