Latonia sp.

Latonia sp.

Figures 13 View Fig , 14 View Fig

Material. Vevi: eight maxillae ( UU VE 502– UU VE 509), two pterygoids ( UU VE 540 and UU VE 542), nine angulars ( UU VE 521– UU VE 528, and UU VE 538), six trunk vertebrae ( UU VE 530– UU VE 535), one sacral vertebra ( UU VE 529), two urostyles ( UU VE 510 and UU VE 511), one coracoid ( UU VE 537), one humerus ( UU VE 515), six radioulnae ( UU VE 513 and UU VE 516– UU VE 520), two ilia ( UU VE 536 and UU VE 541), and two tibiofibulae ( UU VE 512 and UU VE 514).

Description. Almost all of these bones from Vevi are very large and robust, indicative of the presence of a relatively large-sized frog ( Figs. 13 View Fig , 14 View Fig ). However, some smaller specimens are also present, especially among the vertebrae.

Te maxillae from Vevi have a smooth lateral surface

( Fig. 13a–m View Fig ). Te specimens preserve either the anterior end (or part of it) or portions of the bone posterior to the palatine process. Te anterior end is very long. Anteriorly, at least UU VE 507 ( Fig. 13k View Fig ), which represents the complete anterior portion, shows a deep articulation for the premaxilla. Te medial side of the maxilla has a high lamina horizontalis, which is not developed in medial direction. Te lamina ends posteriorly with a well-developed processus pterygoideus. Dorsally, the lamina hosts a deep and narrow groove for the palatoquadrate bar. Ventral to the lamina horizontalis, the alveolar portion bears small, pleurodont and closely-packed teeth. Te tooth row ends posteriorly roughly at the level of the processus pterygoideus. Te posterior end of the maxillae displays a distinct posterior depression on the medial surface, but this appears to be not defined anteroventrally by a ridge even in the largest maxillae. Te concavity of the margo orbitalis is shallow. Te largest and most complete maxillae reach a length of 14.4 mm.

Te fragmentary pterygoids from Vevi preserve part of the ramus maxillaris, provided with a well-developed and rounded ventral flange ( Fig. 13n, o View Fig ). A poorly-developed sculpturing is present on the flange; this is more easily visible on the better-preserved UU VE 540. Te largest fragment is 7.4 mm long.

Angulars from Vevi display two rounded processes on the medial side ( Fig. 13p–r View Fig ). Te paracoronoid process is small and horizontal. Te coronoid process is more developed and subvertical; it continues posteriorly in a laminar and lowering ridge. Te sulcus cartilagine Meckeli is very shallow in correspondence with the paracoronoid process, but deepens distinctly at the level of the coronoid one. A sharp crista mandibulae externa is present, marking ventrally a deep lateral depression on the posterior half of the bone. Te length of the angulars reaches up to 24.6 mm in the largest and most preserved specimen.

Te trunk vertebrae from Vevi are mainly represented by isolated subcylindrical centra, sometimes with a light degree of dorsoventral compression ( Fig. 14a, b View Fig ). Tese have a cotyle on one end and a condyle on the other. Even though it is not undisputedly possible to define an anterior and a posterior end, the presence of a sort of neck around the condyle hints towards an opisthocoelous condition for these vertebrae. In lateral view, the ventral surface is concave. UU VE 530 ( Fig. 14a View Fig ) and UU VE 531 ( Fig. 14b View Fig ) still bear a single, well-preserved transverse process each, which is robust, short and laterally expanded. Te process displays a wide and flat articulation surface for a free rib at its distal end. Te length of the largest centrum is 4.8 mm.

Te single available sacral vertebra (UU VE 529) from Vevi has an anterior condyle and two posterior condyles

( Fig. 14c–g View Fig ). Te anterior condyle is subcircular, whereas the posterior condyles are subelliptical and well separated. In lateral view, the ventral surface of the vertebral centrum is slightly concave. In anterior view, the neural canal is wide and roughly shaped as a mediolaterallyelongated triangle. Te dorsal surface of the neural arch is irregular, but a low carina neuralis is visible along its midline. Te transverse processes and the prezygapophyses are broken off. Te centrum of this vertebra is 5.2 mm long (measured along the midline) and 5.5 mm wide (measured as the maximum width at the posterior condyles).

Te urostyles from Vevi possess two anterior fossae condyloideae, which are mediolaterally elongated and contact each other in the middle ( Fig. 14h–j View Fig ). Tey do not coalesce. Te neural arch is poorly preserved in both specimens. Cylindrical transverse processes are present by its anterior end. Each process is followed by a lamina horizontalis. Tese laminae are very low in UU VE 510

( Fig. 14h–j View Fig ), but strongly more developed in UU VE 511. Te dorsal surface of the neural arch is completely missing in UU VE 511, but its anterior end is preserved in the other specimen. Based on the latter, it can be observed that there is no crista dorsalis and that the arch opened in a wide dorsal fissure. Te longest urostyle is at least 11.3 mm long, but it is not possible to estimate how much of its posterior portion is missing.

Te coracoid (UU VE 537) from Vevi misses the pars epicoracoidalis ( Fig. 14k View Fig ). Te middle portion is straight and narrow. Te pars glenoidalis is very wide. Te specimen is 8.9 mm long.

Only the distal half of a humerus (UU VE 515) from Vevi is preserved, in good overall conditions ( Fig. 14l–n View Fig ). Te diaphysis is straight and ends distally with a sphaerical eminentia capitata, which is slightly laterally shifted. A shallow fossa cubitalis ventralis is present. Structures on the medial side (i.e., epicondylus ulnaris and crista medialis) are strongly more developed than those on the lateral side (i.e., epicondylus radialis and crista lateralis). On the dorsal surface of the distal end, the olecranon scar is short, being almost as long as it is wide. Te complete length of the fragment reaches 11.6 mm.

Radioulnae from Vevi ( Fig. 14r–t View Fig ) have a massive proximal epiphysis, with a wide but short olecranon. Te dorsal surface of the olecranon shows a distinctly rough aspect. Te rest of the bone, distal to the collum antebrachii, is strongly mediolaterally compressed and expands towards the distal end. Te sulcus longitudinalis is very shallow, deepening and widening only in its distalmost half. Te very wide distal epiphysis is preserved only in UU VE 513 ( Fig. 14r View Fig ). Te radial and ulnar portions are mediolaterally compressed. Te length of this skeletal element, even though none of the specimens is complete, reaches up to at least 14.2 mm in the largest and most preserved specimen.

Te most complete ilium (UU VE 536) from Vevi has a rather high dorsal crest, which merges posteriorly with a poorly distinct and elongated dorsal tubercle ( Fig. 14o, p View Fig ). Te dorsal portion of the crest is missing. A distinct tubercular fossa (fossula tuberis superioris sensu Roček, 1994) is not present, but foramina are visible in the corresponding area. Most of the body of the ilium is broken away. Te anteroventral part of the acetabular rim is raised. Tere is no preacetabular fossa. UU VE 541, on the other hand, only preserves the body of the ilium. Laterally, the acetabular fossa is moderately wide and subcircular, with a very high anteroventral portion of the acetabular rim. Both the preacetabular and the supraacetabular fossae are absent. Te ventral acetabular expansion is well developed; the dorsal acetabular expansion is broken. On the medial side, a very deep and wide interiliac groove is present. Te interiliac tubercle is so well developed to an extent that it is not distinguishable from the medial side of the ventral acetabular expansion. UU VE 536 is 14.9 mm long ( Fig. 14o, p View Fig ). UU VE 541 is 8.5 mm long and 8.5 mm high.

Both tibiofibulae from Vevi preserve only the proximal half ( Fig. 14q View Fig ). Tey have a narrow diaphysis, which expands significantly towards the proximal epiphysis. Te width of the epiphysis is slightly less than twice the width of the narrowest part of the diaphysis. Te epiphysis bears a well-distinct and sharp crista cruris. In proximal view, the articular surfaces of both the tibial and the fibular portions are elliptical. Te main axes of these articular surfaces are roughly parallel. Te largest specimen is 19.4 mm.

Remarks. A large anuran taxon is represented in Vevi by remains that share a general discoglossine morphology. Presence of both paracoronoid and coronoid processes on the angular, a sulcus cartilagine Meckeli that deepens at the level of the coronoid process, maxillae with a long processus pterygoideus and a distinct medial depression on the posterior end, as well as the pterygoid provided with a ventral flange support an identification of this large discoglossine with a member of the widespread genus Latonia (Biton et al., 2013, 2016; Roček, 1994, 2013; Syromyatnikova & Roček, 2019; Syromyatnikova et al., 2019b). A precise specific identification is prevented by the absence in the sample of important elements such as frontoparietals and prooticooccipitals. However, few characters that are currently interpreted as taxonomically significant within Latonia (see Roček, 2013; Sorbelli et al., 2021; Syromyatnikova & Roček, 2019; Syromyatnikova et al., 2019b) can be observed. Unsculptured maxillae like those present in the Vevi material characterize all species of the genus, including a possible new species from the Italian Early Pleistocene ( Sorbelli et al., 2021), except for Latonia seyfriedi (including Latonia gigantea ; sensu Syromyatnikova et al., 2019b). Te maxillary tooth row ending with the lamina horizontalis is reminiscent of (some) specimens of L. seyfriedi (reported as L. gigantea in Syromyatnikova & Roček, 2019) and Latonia caucasica , whereas the coronoid process is unlike Latonia vertaizoni in being well developed. In the end, the sculptured ventral flange of the pterygoid is so far only reported for the possible Italian new species ( Sorbelli et al., 2021), but detailed description of referred pterygoids are unavailable for most of the extinct Latonia . As a matter of fact, apart from the extant Latonia nigriventer , this feature can be evaluated only on a single isolated pterygoid attributable to L. seyfriedi (Villa et al., 2019; mentioned there as L. gigantea ), which is unsculptured. Conflicting affinities, therefore, render it difficult to confidently point out possible relations with known taxa, also considering the known variation in at least some of the diagnostic features. More material and a clarification of the validity of diagnostic characters within Latonia are needed in order to better define the taxonomic identity of the Latonia from Vevi.

Discoglossidae indet.

Figure 15 View Fig

Material. Chalicorrema: two urostyles ( UU RA 518 and UU RA 519).

Description.

UU RA 518 and UU RA 519 are two fragments of urostyles ( Fig. 15 View Fig ). UU RA 519 preserves only part of the shaft

( Fig. 15c View Fig ). It has a low carina neuralis, which is open dorsally with a narrow longitudinal groove. UU RA 518 preserves the anterior end and part of the shaft, but not the carina neuralis ( Fig. 15a, b View Fig ). Anteriorly, it has two mediolaterallyextended cotyles, which merge in the midline. Ventrally, a small point is visible at the confluence between the two cotyles. Te fragments UU RA 518 and UU RA 519 are slightly less and slightly more than 10 mm long, respectively.

Remarks. Te dorsal fissuring of the neural arch is a feature shared by discoglossid (sensu Dubois et al., 2021) anurans (i.e., Discoglossus Otth, 1837 , and Latonia ; Roček, 1994; Biton et al., 2016), to which these two urostyles can be therefore assigned. All other observable features are coherent with such an identification. Nevertheless, the very fragmentary status of the specimens and the absence of other clear discoglossid remains in Chalicorrema prevent a more precise referral.