MYLIOBATIDAE Bonaparte, 1838
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publication ID |
https://doi.org/ 10.26879/1283 |
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persistent identifier |
https://treatment.plazi.org/id/A1525343-6630-FF85-FC1F-B040FEA2FC5B |
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treatment provided by |
Felipe |
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scientific name |
MYLIOBATIDAE Bonaparte, 1838 |
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Family MYLIOBATIDAE Bonaparte, 1838 View in CoL Myliobatidae gen. et sp. indet.
Figure 10 View FIGURE 10 A-F
1861 Myliobates toliapicus Ag. ; Rogovich, p. 12, pl. 2, figs. 14, 22.
Material. Nineteen teeth, NMNHU-G 391/3, Vyshhorod.
Description. The teeth ( Figure 10A–F View FIGURE 10 ) are hexagonal and mesiodistally elongated. The root consists of thin, uniformly narrow lobes, fused at the tip, and oriented perpendicular to the crown in the form of a comb. The crown overhangs the root, and it is separated from it by a sharp transverse ridge on the labial side and has a respective recess on the lingual side. It consists of a thin enameloid layer, the surface of which is either straight or convex. There are faint longitudinal ridges and numerous nutritive foramina on the transverse edges of the crown.
Remarks. The series of teeth described above was assigned to the family Myliobatidae based on several characters, including hexagonal shape, mesiodistal elongation, and the presence of multiple nutritive grooves (Cappetta, 2012). We refrain from assigning these fragmentary specimens to a particular genus due to the poor state of their preservation. In addition, the recent molecular divergence estimated by Villalobos-Segura and Underwood (2020) indicates that myliobatid genera did not diverge until the Neogene. Thus, Paleogene forms seemingly represent stem members of their respective lineages and cannot be assigned to any extant genera.
Myliobatiformes indet.
Figure 10 View FIGURE 10 G-I
1843 Myliobates Owenii [sic]; Agassiz, p. 331, pl. 45, figs. 11-13.
1861 Myliobates Owenii [sic] Ag.; Rogovich, p.
11, pl. I, fig. 7.
1912 Myliobates Owenii [sic] Ag.; Savtchenko, p. 167, pl. XIII, fig. 4.
1912 Myliobates sp. ; Savtchenko, p. 167-168, pl. XIII, figs. 1-3.
2019 Myliobatinae indet. 2; Trif et al., p. 13-14, fig. 7.13-7.15.
2021 Myliobatiformes indet.; Szabó et al., p.
391, pl. IX, figs. J’-M’.
2022 Myliobatiformes indet.; Trif et al., fig. 9A-C.
Material. One broken caudal spine, NMNHU-G 391/2, Vyshhorod.
Description. The flattened caudal spine ( Figure 10G–I View FIGURE 10 ) is large with a preserved length of 14.6 cm and maximum width of 2.0 cm. It is broken into three fragments of different sizes. The spine gradually tapers towards the distal tip. Both lateral edges at a distance of about 4 cm from the base bear short sawtooth barbs that are proximally curved and increase in size to the tip. Both dorsal and ventral surfaces of the spine are striated and covered by irregular grooves parallel to each other. In addition, there are two longitudinal ridges on the ventral side of the spine.
Remarks. Rogovich (1861) initially identified this specimen as Myliobates Owenii [sic], and, in fact, it looks identical to those figured by Agassiz (1843, pl. 45, figs. 11-13). However, M. owenii is now recognised a nomen dubium because it was erected based on the caudal spine and not on dentition (Pollerspöck and Straube, 2022). According to Hovestadt and Hovestadt-Euler (2013) and Trif et al. (2022), caudal spines of Myliobatiformes have little diagnostic value and therefore we leave the specimen considered here in open nomenclature.
Elasmobranchii indet.
Figure 11 View FIGURE 11
1861 Lamna (vertebrae); Rogovich, p. 62, pl. IX, figs. 2, 3, 5.
1861 Shark vertebrae; Rogovich, p. 63, pl. IX, figs. 7, 8.
Material. Nine vertebrae, NMNHU-G 391/125, 391/126, 391/127, 391/129, 391/130, 391/131, 391/133, 391/134, 391/135, Vyshhorod.
Description. The vertebrae are represented by well-calcified, unperforated, amphicoelous centra with a variable range of sizes but quite similar in overall morphology.
Remarks. Because of the wide range of size and morphological variations observed among the nine vertebrae, they most certainly represent multiple taxa. For example, NMNHU-G 391/126, 391/129, 391/130, 391/131, 391/133, 391/134, and 391/135 may belong to the same taxon because they exhibit laterally oblong articular surfaces, but the articular surfaces are circular in NMNHU-G 391/ 125 and 391/127. However, they cannot be interpreted as Lamniformes because their intermedialia does not exhibit any noticeable radiating calcified lamellae. The slight dorsoventral compression observed in these vertebrae may indicate that they belong to a batoid, but we conservatively describe them here as Elasmobranchii indet. They may belong to one or more of the aforementioned taxa in this study, and their exact taxonomic identifications are difficult because they are not accompanied by any teeth, which have higher diagnostic value.
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