Latonia sp.
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publication ID |
https://doi.org/ 10.26879/1323 |
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DOI |
https://doi.org/10.5281/zenodo.11033545 |
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persistent identifier |
https://treatment.plazi.org/id/03F52665-D046-FF9F-FE0D-9DB4FD1E716E |
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treatment provided by |
Felipe |
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scientific name |
Latonia sp. |
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Figures 13–15 View FIGURE 13 View FIGURE 14 View FIGURE 15
Material. Hambach 6C: three premaxillae (IPB-HaH 2050, IPB-HaH 2280/2281); 12 maxillae (IPB-HaH 2052/2053, IPB-HaH 2056/2060, IPB-HaH 2069/2070, IPB-HaH 2266/2267, IPB-HaH 2278); two frontoparietals (IPB-HaH 2002, IPB-HaH 2338); three angulars (IPB-HaH 2051, IPB-HaH 2396/2397); one atlas (IPB-HaH 2071); six trunk vertebrae (IPB-HaH 2072/2074, IPB-HaH 2221/ 2222, IPB-HaH 2229); one sacral vertebra (IPB-HaH 2219); two urostyles (IPB-HaH 2199/2200); three scapulae (IPB-HaH 2324/2325, IPB-HaH 2329); four humeri (IPB-HaH 2055, IPB-HaH 2061, IPB-HaH 2316, IPB-HaH 2336). Hambach 11: four maxillae (IPB-HaR 2016/2017, IPB-HaR 2041/ 2042); five angulars (IPB-HaR 2115/2117, IPB-HaR 2142/2143); four trunk vertebrae (IPB-HaR 2022/2023; IPB-HaR 2032/2033); one sacral vertebra (IPB-HaR 2014); one urostyle (IPB-HaR 2034); one humerus (IPB-HaR 2127); two ilia (IPB-HaR 2015, IPB-HaR 2083). Hambach 11C: two maxillae (IPB-HaR 2425/2426); one angular (IPB-HaR 2416); one ilium (IPB-HaR 2417).
Description. Premaxillae are moderately large in size and have a mediolaterally elongated pars dentalis, with a robust and short lamina horizontalis. The tooth row covers the entire length of the bone. In IPB-HaH 2050 ( Figure 13 View FIGURE 13 A-B; the only specimen in which it is complete), the tooth row shows 13 tooth positions. None of the specimens preserve the complete pars facialis, but a deep recess is recognisable on the inner surface of its base. The external surface of the bone is smooth.
Maxillae ( Figure 13 View FIGURE 13 C-H) are always fragmentary, but they can reach a very large size. The lamina horizontalis is robust and not strongly developed in medial direction; a moderately shallow groove for the palatoquadrate bar is present on the dorsal surface of its posterior portion. The processus palatinus is partially preserved only in IPB-HaH 2052, IPB-HaH 2056, IPB-HaH 2059 ( Figure 13 View FIGURE 13 E-F), IPB-HaR 2042, and IPB-HaR 2426; a moderately developed and strongly anteriorly inclined edge provided with a groove on its posterodorsal surface is present on the medial side of the process. The processus pterygoideus is usually broken off, but a large posterior depression is still recognizable on the medial surface between it and the processus zygomaticomaxillaris. When preserved (IPB-HaH 2058, IPB-HaH 2060, IPB-HaH 2266, IPB-HaH 2267, IPB-HaR 2016, and IPB-HaR 2017), the processus pterygoideus is short, moderately robust and pointed. The anterior margin of the depression is marked by a moderately developed ridge. The tooth row continues posteriorly slightly beyond the lamina horizontalis. The lateral surface is covered by a dermal sculpturing made by tubercles and ridges, which concentrates mainly in the posterodorsal part of the bone. IPB-HaH 2056, IPB-HaH 2057, IPB-HaH 2059, IPB-HaH 2060, IPB-HaH 2266, IPB-HaH 2267, IPB-HaH 2278, IPB-HaR 2041, IPB-HaR 2042, IPB-HaR 2425, and IPB-HaR 2426 have a smooth lateral surface, but they represent only the anterior end (IPB-HaH 2059), the middle portion of the bone (IPB-HaH 2056, IPB-HaH 2057, IPB-HaR 2042, IPB-HaR 2425, and IPB-HaR 2426) or part of the posteroventral portion (IPB-HaH 2060, IPB-HaH 2266, IPB-HaH 2267, IPB-HaH 2278, and IPB-HaR 2041). Some of these smooth specimens can be very large in size (e.g., IPB-HaH 2059).
IPB-HaH 2002 ( Figure 13 View FIGURE 13 I-J) is a moderately large fragment of frontoparietal, probably representing part of the left anterolateral portion of the bone. The ventral surface displays a narrow and elongated incrassatio frontoparietalis. The preserved portion of the incrassatio has a symmetrical appearance, thus suggesting that it was unpaired and that a small part of the right lateral side of the bone is also represented. The foramen parietale is not present in the preserved portion of the frontoparietal. The pars contacta is laminar and rather well developed. The anterolateral corner of the fragment represents part of the left anterior horn. The dorsal surface of the specimen is almost completely covered by a well-developed dermal sculpturing, made up by tubercles. These are densely arranged and some of them fuse to origin short ridges. Part of the anterior horn is unsculptured. IPB-HaH 2338 is a fragment of the left posterolateral portion of a frontoparietal with a similar dermal sculpturing.
Angulars ( Figure 13 View FIGURE 13 K-S) have a processus paracoronoideus anterior to the processus coronoideus. The two processes are similar in size. The former is horizontal, whereas the latter is almost vertical or slightly medially inclined. The processus coronoideus is well developed and does not extend posteriorly. By the processes, the sulcus cartilagine Meckeli is only a moderately shallow groove. A low crista mandibulae externa is visible on the lateral surface of the bone; it defines the ventral margin of a very slightly depressed area. In IPB-HaH 2051, IPB-HaH 2396, and IPB-HaH 2397, which are very large specimens, both the crista and the depressed area are more developed.
Presacral vertebrae ( Figure 14 View FIGURE 14 A-K) are opisthocoelous, robust and very large. The centrum is subcylindrical and the neural canal is subelliptical (main axis directed horizontally) in anterior view. The anterior cotyles of the atlas ( Figure 14 View FIGURE 14 A-E) are almost in contact medially. The same vertebra displays a sharp keel on its ventral surface. The transverse processes of the trunk vertebrae ( Figure 14 View FIGURE 14 F-K) are robust and laterally directed. The dorsal surface of the neural arch is large and flattened, with a low, moderately- or well-developed carina neuralis. Zygapophyses are suboval and twisted dorsally of about 45°.
Sacral vertebrae ( Figure 14 View FIGURE 14 L-O) have an anterior condyle and two posterior condyles. The dorsal surface of the neural arch shows a low carina neuralis developing a small posterior tip. Prezygapophyses are subelliptical and dorsally inclined of about 45°. Transverse processes are broken in both specimens, but in IPB-HaH 2219 they show a slight anteroposterior enlargement ( Figure 14L View FIGURE 14 ). The anterior margin of these processes is clearly perpendicular to the vertebral centrum in IPB-HaH 2219 ( Figure14L View FIGURE 14 ), but it seems posterolaterally inclined in IPB-HaR 2014 ( Figure 14M View FIGURE 14 ). However, transverse processes of the latter sacral vertebra are less preserved and reconstruction of their original shape is somehow doubtful.
Urostyles ( Figure 14 View FIGURE 14 P-R) preserve only the anterior end, showing two anterior cotyles. Except for IPB-HaH 2200 ( Figure 14Q View FIGURE 14 ), which is rather small, they can reach a large size. A transverse process is present on each side of the neural arch, continuing posteriorly in a horizontal lamina in IPB-HaR 2034 ( Figure 14R View FIGURE 14 ). The carina neuralis is not developed and, posteriorly to the transverse processes, the neural arch presents a narrow fissure in the middle of the dorsal surface.
Scapulae ( Figure 15 View FIGURE 15 A-F) are very large and robust. They are short and wide and show a very well-developed crista anterior (though broken in IPB-HaH 2325 and completely missing in IPB-HaH 2329). The pars suprascapularis is very wide. The pars acromialis is missing in all specimens, whereas the robust pars glenoidalis is always poorly preserved.
Humeri are very robust and large-sized. IPB-HaH 2055, IPB-HaH 2336, and IPB-HaR 2127 preserve only the distal end, IPB-HaH 2061 ( Figure 15 View FIGURE 15 G-H) misses the proximal half, whereas IPB-HaH 2316 lacks only the proximal portion. The eminentia capitata is spherical and distinctly shifted laterally compared to the axis of the diaphysis. A moderately deep fossa cubitalis ventralis is present, except for IPB-HaH 2061 and IPB-HaH 2336. The epicondylus ulnaris is more than twice as large as the radialis one. Cristae medialis and lateralis are well developed and sharp in IPB-HaH 2061 and IPB-HaH 2316 and moderately developed in IPB-HaH 2055, IPB-HaH 2336, and IPB-HaR 2127; the former bends in dorsal direction proximally. The olecranon scar is moderately large in most specimen (though it is poorly visible in IPB-HaH 2061 and IPB-HaR 2127), but small in IPB-HaH 2055.
Ilia ( Figure 15 View FIGURE 15 I-N) are large. They display a dorsal crest, which merges posteriorly with the dorsal tubercle. The tubercle is low, elongated and rather poorly distinct. The posterior portion of the dorsal crest, anteroventral to the tubercle, hosts a shallow tubercular fossa with few foramina on its lateral surface. The acetabular fossa is moderately wide and somehow elongated. The supraacetabular fossa is present and shallow. The dorsal acetabular expansion is short. Together with the strongly anteriorly-inclined dorsal tubercle, it originates a very obtuse angle. The ventral acetabular expansion seems more developed, but it is never completely preserved. The medial side of the ilial body displays a deep interiliac groove and the base of a (broken) interiliac tubercle.
Remarks. A large Latonia is clearly present in Hambach, being identifiable based on the following combination of characters ( Roček, 1994b, 2013): presence of both a coronoid and a paracoronoid process on the angular; posterior depression on the maxilla; ventral keel on the atlas; laterallyshifted eminentia capitata on the humeri; ilia with a thin dorsal crest and an obtuse angle between the tubercle and the dorsal acetabular expansion; and possibly also unpaired frontoparietal. Syromyatnikova and Roček (2019) recently summarized the most taxonomically-significant osteological features of the known species within this genus. The sculptured frontoparietal clearly exclude affinities with the extant Latonia nigriventer ( Mendelssohn and Steinitz, 1943) (see also Biton et al., 2013, 2016), whereas the well-developed coronoid process is unlike the morphology seen in Latonia vertaizoni ( Friant, 1944) . Furthermore, the absence of a posterior extension of the latter process differs from at least some Latonia ragei Hossini, 1993 . In the Latonia from Hambach, the maxillary tooth row exceeds posteriorly the extension of the lamina horizontalis, recalling in this L. nigriventer , L. ragei , and some Latonia seyfriedi von Meyer, 1843 (in the sense of Syromyatnikova et al., 2019, that is including Latonia gigantea ( Lartet, 1851) as well) but differing from Latonia caucasica Syromyatnikova and Roček, 2019 . The presence or absence of sculpturing on the maxillae was commonly used in the past to distinguish two groups within Latonia : sculptured maxillae were generally referred to L. gigantea , in contrast with L. ragei and L. vertaizoni having unsculptured maxillae. This distinction was, however, complicated by the fact that the lateral surface of the maxillae of L. seyfriedi was not known for a long time. Only recently, Syromyatnikova et al. (2019) demonstrated that the latter species has sculptured maxillae as well, proposing L. gigantea as a junior synonym of it based on this and other features. Moreover, Syromyatnikova and Roček (2019) added L. caucasica to the list of the Latonia species with unsculptured maxillae. To add further complexity to the maxillary sculpturing character, these dermal ossifications originate in Latonia as a separate layer, which only contacts the surface of the bone through fragile trabeculae ( Roček, 1994b; Syromyatnikova et al., 2019). Thus, separation of the sculptured layer from the bone due to breakage of these trabeculae is not unlikely, leading to the possible artifactual recognition of unsculptured maxillae in place of the original sculptured ones. What is more, maxillae referred to Latonia showing an overall smooth lateral surface, but with few rugosities usually concentrated on the posterodorsal corner, have been described lately (e.g., from the Early Miocene of Greece; Georgalis et al., 2019a). These may be interpreted as juveniles of sculptured forms when small, but the presence of some large elements presenting the same pattern (such as is the case with the Hambach fossils) hints towards the need of further scrutiny of this feature. Another important character for the identification of Latonia species is the direction of the sacral transverse processes. The possible presence of two different morphologies in the two sacral vertebrae from Hambach (i.e., clearly perpendicular versus possibly posterolaterally-inclined processes), furthermore coming from two different layers, may suggest the presence of two different taxa in the two different stratigraphic portions of the site. However, the uncertainty surrounding the observation of the second morphotype, together with the possible variation of this character apparent in at least L. seyfriedi (see Syromyatnikova and Roček, 2019) as well as the generally comparable morphology showed by all other Latonia remains from Hambach, suggest caution on this. It is evident that, based on the current state of knowledge, a specific identification of the Latonia from Hambach would be somehow ambiguous, and we thus refrain from proposing one, pending a detailed revision and clarification of the diagnostic characters of the species currently included in the genus.
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