Friday, July 21, 2017

[Paleontology • 2017] Owadowia borsukbialynickae • A New Pancryptodiran Turtle from the Late Jurassic of Poland and Palaeobiology of Early Marine Turtles


 Owadowia borsukbialynickae
Szczygielski, Tyborowski & Błażejowski, 2017


Abstract

Although Western Europe has yielded numerous Jurassic turtle taxa, several represented by cranial material or complete skeletons, the fossil record of the Jurassic turtles remains scarce to the north and east from Germany. Although some Late Jurassic testudinates were historically described from Poland, they were, thus far, represented by fragmentary remains that never were properly figured or described in detail. Therefore, very little is known about the mid-Mesozoic diversity of turtles in that region of the continent. A new pancryptodiran turtle genus and species, Owadowia borsukbialynickae, is described from the uppermost Jurassic (Tithonian, ca. 148 Ma) carbonate sediments of the Kcynia Formation in Owadów-Brzezinki Quarry, near Tomaszów Mazowiecki in central Poland. The lower jaw morphology and palaeoecological setting inhabited by the new genus and species, together with the trophic relationships of the Jurassic pancryptodiran turtles, are discussed in an attempt to determine the potential range of mode of life of O. borsukbialynickae. We propose that the new specimen belongs to a new durophagous pancryptodiran turtle taxon. O. borsukbialynickae might have spent considerable time in the marine environment and specialized on eating hard-shelled invertebrates like bivalves and decapod crustaceans, common to that setting.


Figure 5: Owadowia borsukbialynickae, life restoration during feeding on decapod crustacean.
Digital painting by T. Szczygielski 

SYSTEMATIC PALAEONTOLOGY

Order Testudinata Klein, 1760
Pancryptodira Joyce, Parham, & Gauthier, 2004
Incertae sedis

Genus Owadowia gen. nov.

Type species. Owadowia borsukbialynickae sp. nov.

Etymology. Owadowia, from Owadów-Brzezinki Quarry—the locality where remains of this new turtle were found.
Owadowia borsukbialynickae sp. nov.

Etymology. borsukbialynickae, in honour to the Polish palaeontologist, Prof. Magdalena Borsuk-Białynicka—a long time researcher of the Mesozoic reptiles.

Type specimen. ZPAL V/O-B/1959 (Figures 2-4), stored in the collections of the Institute of Palaeobiology, Polish Academy of Sciences in Warsaw, a fragment of the lower jaw, right coracoid, right ilium, and mostly complete right femur.

Type locality. Owadów-Brzezinki Quarry of Nordkalk GmbH, Sławno, close to Tomaszów Mazowiecki (Central Poland). 

Occurrence. Kcynia Formation, Tithonian, Upper Jurassic; the first lithofacial unit within Zaraiskites zarajskensis subzone.

Diagnosis. Relatively large Jurassic turtle (estimated carapace length around 50 cm) with narrow and V-shaped lower jaw, relatively short and wide but pronounced snout, massive, spoon-like symphysis, no symphyseal hook, well-developed triturating surface in the symphyseal area, moderately developed triturating surface with parallel lingual and labial ridges along the mandibular rami, the labial ridge much higher and sharper than the lingual ridge, the lingual ridge only present laterally and gradually disappearing towards the midline of the symphyseal area, splenial large. The triangular, symmetrical coracoid plate without anterior or posterior expansions, the coracoid neck without coracoid foramen. The slender and proximally and distally slightly curved femur with deep, U-shaped intertrochanteric fossa, small fibular condyle and prominent, well-developed tibial condyle. The ilium with expanded ventral end, constricted neck and well-developed, thin dorsal fan with posterior and no anterior expansion, no signs of sutural attachment to the carapace.


CONCLUSIONS
A new pancryptodiran turtle, Owadowia borsukbialynickae, is described from the Tithonian lagoon limestones of Owadów-Brzezinki Quarry, Poland. The most characteristic trait of this new taxon is its expanded triturating surface indicating a durophagous ecology. The morphology of O. borsukbialynickae mandible is unlike that any other Jurassic turtle known thus far, but rather resembles the Cretaceous protostegids and recent cheloniids, which suggests that this turtle might have inhabited a similar trophic niche. While it is possible that O. borsukbialynickae was a semiaquatic or freshwater turtle, the lower jaw morphology and its inferred feeding preferences make such assumption unlikely, and rather suggest that this animal spent a lot of time in a shallow water, possibly marine environment, like Owadów-Brzezinki lagoons. The taphonomic evidence (the quantitative dominance of marine vertebrates in the Owadów-Brzezinki bone-bed, lack of any brackish and freshwater taxa, and absence of transportation) suggests that O. borsukbialynickae was an inhabitant of these lagoons, rather than a terrestrial animal that inhabited the adjacent land. Such assumptions may be supported in the future by new finds and isotope data.


Tomasz Szczygielski, Daniel Tyborowski and Błażej Błażejowski. 2017. A New Pancryptodiran Turtle from the Late Jurassic of Poland and Palaeobiology of Early Marine Turtles. Geological Journal. DOI: 10.1002/gj.2952

No comments:

Post a Comment