Latonia, Meyer, 1843
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publication ID |
https://doi.org/ 10.5281/zenodo.5378363 |
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persistent identifier |
https://treatment.plazi.org/id/03F57B1B-FFC6-FFE9-FD26-52C3FDA7F1FE |
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treatment provided by |
Marcus |
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scientific name |
Latonia |
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Latonia View in CoL aff. L. ragei Hossini, 1993 ( Fig. 2 View FIG )
MATERIAL EXAMINED. — 1 incomplete premaxilla (Béon 2004 LT 11), 8 incomplete maxillae (Béon 2004 LT 12, 13), 1 oticoccipital (Béon 2004 LT 14), 3 presacral vertebrae (Béon 2004 LT 15), 1 sacral vertebra (Béon 2004 LT 16), 1 coracoid (Béon 2004 LT 17), 2 humeri (Béon 2004 LT 18, 19), and 1 ilium (Béon 2004 LT 20).
DESCRIPTION
Premaxilla
The bone bears teeth but it lacks sculpture. On the lamina horizontalis, the pars maxillaris is less developed than the pars palatina that strongly protrudes medially. On the medial face, a deep depression is located at the base of the pars facialis.
Maxilla
All specimens lack sculpture. The lamina horizontalis is thick with a rounded medial border. The tooth row terminates beyond the posterior end of the lamina horizontalis. A broad and shallow posterior depression occurs on the medial face of the bone; in one specimen ( Fig. 2B View FIG ), a second, smaller and more posterior depression is present.
Oticoccipital
In dorsal view, the lateral prootic process (ramus lateralis; Špinar 1978) is elongate and slender, the sutural surface for the frontoparietal is striated, and the posterior prootic crest (prominentia ducti semicircularis posterioris; Roček 1994) forms a strong prominence directed posteromedially. In posterior view, the condyle is close to the medial border of the bone. The supracondylar fossa is deep and limited medially by a vertical ridge. The fenestra ovalis appears as the lateral aperture of a transverse elongate bony tube.
Vertebrae
The vertebrae are opisthocoelous. In presacrals, the centrum is cylindrical; as a result, the condyle and condyle are round. The neural arch is long, of the imbricate type, and provided with a strong neural spine that ends posteriorly as an interzygapophyseal point. The sacral processes of the sacral vertebra are incomplete, but they are directed posterolaterally. Apparently, they were moderately widened distally, as in the living Discoglossus .
Coracoid
The pars glenoidalis is well developed whereas the damaged pars epicoracoidalis appears to be moderately widened.
Humerus
The condyle is shifted laterally and the fossa cubitalis is shallow. The margin of the lateral crest is slightly deflected ventrally. Only one humerus is provided with a medial crest; in its proximal part, the border of the latter crest forms a medial, slightly prominent curve.
Ilium
The posterior part of the only available ilium is damaged. In posterior view, an interiliac groove is present while the interiliac tubercle is partly broken off. The shaft bears a low and medially bent dorsal crest. The posterior part of the crest forms the tuber superius that is low and slightly globulous.
COMMENTS
These specimens display a combination of features that unquestionably points to discoglossids: pars palatina of premaxilla long; medial face of the pars facialis of the premaxilla with a deep depression; maxilla toothed and high; lateral prootic process of oticoccipital elongate; fenestra ovalis at the lateral extremity of a bony tube; vertebrae opisthocoelous; centrum cylindrical; pars glenoidalis of coracoid expanded but pars epicoracoidalis moderately widened; condyle of humerus shifted laterally; interiliac tuber and interiliac groove present.
Several traits demonstrate that the discoglossid from Béon 1 belongs to the Discoglossus-Latonia assemblage: lamina horizontalis of maxilla thickened; lateral prootic process of oticoccipital slen- der; neural spines of vertebrae well developed; overall morphology of humerus similar; presence of a dorsal crest and a tuber superius on the ilium. The presence of a deep supracondylar fossa on the oticoccipital, the strong posteromedial projection of the posterior prootic crest, the presence of a broad depression on the medial face of the maxilla, the projection of the tooth row posterior to the lamina horizontalis, the medial curve of the border of the medial crest of the humerus, and the weakly prominent tuber superius of the ilium are consistent with Latonia and rule out referral to the living genus Discoglossus .
Latonia View in CoL is known in Europe from the late Oligocene to the early Pleistocene ( Delfino 2002; Rage & Roček 2003). The absence of sculpture distinguishes the species from Béon 1 from Latonia gigantea ( Lartet, 1851) that is known from the early Miocene (MN 4) to the early Pliocene (MN 15) ( Rage & Hossini 2000; Roček & Rage 2000). This character and the posterolaterally directed and moderately widened sacral processes of the sacral vertebra are reminiscent of L. ragei , a species known from the latest Oligocene (MP 30; Hossini 1993) to the early Miocene (MN 4; Sanchiz 1998a). L. vertaizoni (Friant, 1944) (late Oligocene) is the only other species in which the lack of sculpture on the maxilla is confirmed ( Roček 1994); but the anterior border of the sacral processes of this species is perpendicular to the vertebral axis, whereas in the species from Béon 1 this border is directed posterolaterally. The comparison with L. seyfriedi , the type species of the genus (MN 7+8, middle Miocene), is not possible because it is represented only by articulated specimens whose ventral face only is observable; consequently, it is impossible to determine whether sculpture is present on the maxilla ( Roček 1994).
A(d)
The specimens from Béon 1 are smaller than those representing L. ragei at Coderet (MP 30) and Laugnac (MN 2), both localities in France. The snout-vent length of the individuals from Béon 1 was about 9 to 13 cm whereas those from Coderet and Laugnac reached about 18 cm. In a d d i t i o n, i n t h e f o s s i l s f r o m C o d e r e t a n d Laugnac, the posterior prootic crest, medial crest of the humerus, and tuber superius of the ilium are more robust, the depression of the medial face of the maxilla is deeper and more distinctly limit- ed, and the sacral processes are directed slightly more posteriorly. In summary, the discoglossid from Béon 1 is close to L. ragei , but because of some differences, it cannot be referred to this species without reservation. However, the specimens from Béon 1 being smaller, the differences are perhaps only of ontogenetic nature.
REMARKS
Roček (1994) suggested that Latonia vertaizoni is present at Coderet (MP 30). This opinion was based on the absence of sculpture on the maxilla. But in the sacral vertebrae from Coderet, the sacral processes are not perpendicular to the vertebral axis, therefore they cannot belong to L. vertaizoni ; they are directed posterolaterally as in L. ragei . There is no significant difference between the specimens from Laugnac (MN 2), the type locality of L. ragei , and those from Coderet. Therefore, as stated by Hossini (1993) the Latonia species from Coderet is L. ragei ; this species is not restricted to the early Miocene.
Böhme (2002) reported L. ragei from MN 5 localities in Austria; thus the Austrian fossils would represent the youngest record of the species. But the identification rests on fragmentary remains scattered in several sites, therefore it cannot be accepted without reservation.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
