Testudinidae
Creators: name: Luján, Àngel H.
name: Čerňanský, Andrej
name: Bonilla-Salomón, Isaac
name: Březina, Jakub
name: Ivanov, Martin
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Testudines
Testudinidae

description: Testudinidae indet. (Fig. 4)
LOCALITIES. — MWQ4/2018.
STUDIED MATERIAL. — Czech Republic. South Moravia Region, Mokrá-Quarry, shell and postcranial remains (Fig. 4 A-M): Pal. 1363, shell fragment; Pal. 1364, scapula (i.e., anterodorsal process fragment); Pal. 1365, right fibula.
DESCRIPTION
Only a shell fragment formed by two portions of plates is known (Fig.4 A-D).Pal.1363 corresponds most likely to a carapace portion, but it is poorly preserved and is not possible to assess this confidently. The length and maximum width of the preserved plate fragment is 6 cm. The external part is completely smooth and is not crossed by any sulcus (Fig. 4C, D). A suture is recognized on top of plate, which is concave and approximately 2 cm wide. A partial bone, belonging to the shoulder girdle, has been identified (Pal.1364: Fig.4 E-H). Only the anterodorsal process fragment is preserved.Pal.1364 is subcylindrical in cross-section and distally rounded.The distal surface ends in a rough rounded area to join with the visceral part of the carapace (Fig. 4H). The hind limb skeleton is restricted to one partial fibula (Fig. 4 I-M) that is elliptical in cross-section. Its distal articular surface is slightly small, oval and convex (Fig.4M).Both postcranial bones are poorly preserved and no significant details can be discerned.
REMARKS
Fossil remains of giant tortoises are not very common in Miocene assemblages of Central Europe; their record being limited to few localities from Austria, Germany, Hungary and Switzerland (Alba et al. 2010, 2011; Carmona et al. 2011; Luján 2015). Loveridge & Williams (1957) proposed that all European giant tortoises should be transferred into the extant genus Geochelone. This proposal was adopted for some time, and consequently, large tortoise remains in Europe are still frequently referred to in the literature as Geochelone sp. (e.g., Auffenberg 1974; Młynarski 1976). However, current phylogenies do not support a close relationship between Mio- Pleistocene large tortoises and Geochelone. More recently, Bourgat & Bour (1983) referred all giant fossil tortoises to the genus Cheirogaster. Most subsequent works accepted this genus attribution (e.g., Luján et al. 2010, 2014), until recently when Pérez-García & Vlachos (2014) proposed that European Neogene giant tortoises constitute a clade that is more derived than the type species of Cheirogaster.To allocate these taxa, Pérez-García & Vlachos (2014) erected the genus Titanochelon, with Ti. bolivari (Hernández- Pacheco, 1917) as its type species. This genus is characterized by a shell reaching over 100 cm and the fusion of marginal scutes 12 (i.e., constituting a supracaudal scute). However, the evolution of gigantism amongst fossil tortoises is clearly a homoplastic phenomenon, mainly related to insular conditions, or adaptation to either global or local environmental changes (Kear 2010; Luján et al. 2010, 2017b; Itescu et al. 2014). Similarly, the fusion of marginal scutes 12 occurs in many extant and extinct genera and cannot be considered autapomorphic for the genus Titanochelon. In summary, the taxonomy of the Miocene giant tortoises of Europe is still a subject of debate and will require improvement of existing data matrix (e.g., including more skull characters) in order to decipher the phylogenetic relationships of Titanochelon (Luján et al. 2017b).
description: Published as part of Luján, Àngel H., Čerňanský, Andrej, Bonilla-Salomón, Isaac, Březina, Jakub & Ivanov, Martin, 2021, Fossil turtles from the early Miocene localities of Mokrá-Quarry (Burdigalian, MN 4), South Moravian Region, Czech Republic, pp. 691-707 in Geodiversitas 43 (20) on page 698, DOI: 10.5252/geodiversitas2021v43a20, http://zenodo.org/record/5679113