Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 89. (Budapest 1997)

Vremir, M., Codrea, V. ; Farkas, B.: Trionyx stiriacus Peters, 1855 (Reptilia, Testudines) from the Sarmatian (Middle Miocene) of Minişu de Sus (Romania)

Horizon: Middle Miocene, Early Sarmatian (Volhynian, final Astaracian, MN 8 or possibly 7). Dimensions: see Tables 1-5. Description: MTB 21636/1 (Fig. 2) - The disk has a subcircular outline with a flat transverse carapacial profile, and a highly developed, bilobcd nuchal plate. The cranial margin is marked by a series of digited apophyses. The nuchal is 54 mm long and 192 mm wide at the midline. The shape of the pleurals is subscalloped on the front of the disk, and elongate quadrilateral with smooth external margins on the middle-posterior side. The free ends of the ribs show an obvious enlargement. They are relatively robust, having lengths of approximately 30 mm and widths of 17-28 mm, and thus generally represent 1/5 of the total length of the pleurals. No preneural; the neural file consists of 7 elements* generally of an elongate-hexagonal shape, in the anterior section of the series having short posterior and longer anterior sides, the more posterior plates having a reversed pattern; the alpha-numeric formula of neural configuration (cf. PRITCHARD 1988) is 6A-6P-6P-6P-4-6A-5. The first neural is the most massive of all, strongly enlarged anteriorly. The length of the neural file N 1-6 is 192 mm. On the basis of the available markers, the following dimensions can be estiTable 2. MTB 21636/1; dimensions of neurals (in mm) No. Length Anterior width Posterior width Maximal width N 1 47 21 19 25 N2 30 19 18 23 N3 35 18 10 21 N4 30 10 10 20 N5 23 10 11 16 N6 23 11 12 20 Table 3. MTB V-23; dimensions of pleurals (in mm) No. Length Proximal width Distal width P2 108* 55 P3 138 34 40 P4 146 33 43 P5 139 29 42 P6 133 33 58 P7 123 18* 36 (* - incomplete) * Whereas FARKAS (1995) followed CARPENTER (1981) and MEYLAN (1984, 1987) in counting the "presumably" fused preneural and first neural as two elements, it is regarded here as a single plate. Recent studies of ontogenetic development of the bony shell in Pelodiscus sinensis (WIEGMANN, 1834) by CHEREPANOV (1995) suggest that the most anterior neural develops from a single anläge in modern trionychids other than Aspideretes, and corresponds to the first neural of other chelonians. The occasional presence of a vestigial preneural in hatchlings of these species is thus considered an aberrant condition.