Himantura souarfortuna, Adnet & Marivaux & Cappetta & Charruault & Essid & Jiquel & Ammar & Marandat & Marzougui & Merzeraud & Temani & Vianey-Liaud & Tabuce, 2020
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publication ID |
https://doi.org/ 10.26879/1085 |
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publication LSID |
lsid:zoobank.org:pub:B6B8E985-F1CF-4C10-BB00-602E5BF36C1C |
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persistent identifier |
https://treatment.plazi.org/id/03BA87C1-FFEE-FFFF-C291-E561CFF3B024 |
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treatment provided by |
Felipe |
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scientific name |
Himantura souarfortuna |
| status |
sp. nov. |
Himantura souarfortuna nov. sp.
Figure 12 View FIGURE 12 D-M
zoobank.org/ 7B76AC15-5452-454A-801A-603CF5C9C6AC
2016 Himantura sp.1 ; Merzeraud et al., p. 14-15, tab. 1.
Etymology. Derived from Souar-Fortuna formations where the holotype comes from.
Type locality and stratum. KEB 1-194 ( Figure 12G View FIGURE 12 ) from the KEB-1 locality, Souar-Fortuna formations in Djebel el Kébar, Tunisia .
Other material. Additional material, including figured KEB 1-191 to 1-193 and KEB 1-195 to 1-200 ( Figure 12 View FIGURE 12 D-F, H-M), consists of 100 male and female teeth from the KEB-1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia, including the specimens figured .
Diagnosis. Fossil Himantura only known by isolated teeth reaching a large size (4 mm long). The heterodonty is weak with only molariform teeth without cusp. It differs from the others representatives of urogymnins known to date by having teeth with a globular crown marked by a transversal keel, rarely cutting, and often bombed and striated by numerous regular vertical ridges, a finely rugose labial face, and a low root with well-separated lobes.
Description
The dentition is characterized by a gradual monognathic heterodonty, with high-crowned teeth which decrease in size toward the commissure. Evidence of dignathic heterodonty was not detected, all teeth being non cuspidate. Teeth can be relatively massive and can reach a large size with a maximum of 4.2 mm long ( Figure 12 View FIGURE 12 H-J). The holotype ( Figure 12G View FIGURE 12 ) is probably an antero-lateral tooth, considering the root shape of the selected specimen, with elongated root lobes. In occlusal view, the crown is sub-hexagonal in shape. The crown has an inward bent, rounded ( Figure 12 View FIGURE 12 G-J) to salient ( Figure 12F View FIGURE 12 ), transverse keel, which divides the crown into distinct labial and lingual faces. None of the teeth identified in this taxon have well-detached cusp, the few anterior teeth exempt of wear having only a more or less prominent cutting transversal keel ( Figure 12F View FIGURE 12 ). The lingual face of the crown is partially smooth, except in its occlusal extremity, domed, where several vertical deep ridges are equally distributed under and across the transverse keel ( Figure 12 View FIGURE 12 F-M). The labial face is convex and covered by numerous wrinkles of enameloid that often anastomose into irregular small crests and pits ( Figure 12G View FIGURE 12 2 View FIGURE 2 ). These peaks gradually fade towards the labial visor. The lower part of the labial visor is without ornamentation ( Figure 12G View FIGURE 12 2, K2 View FIGURE 2 ). The root is narrow with respect to the crown, whereas being relatively long. It is also relatively short compared to the crown in profile ( Figure 12D View FIGURE 12 2, G2 View FIGURE 2 ), and extends lingually beyond the lingual visor of the crown in occlusal view. The root is of holaulacorhizous type ( Figure 12D View FIGURE 12 3 View FIGURE 3 , K 2 View FIGURE 2 ), with two lobes separated by a large nutritive groove where a circular foramen opens labially ( Figure 12K View FIGURE 12 2 View FIGURE 2 ).
Some small teeth ( Figure 12D, E View FIGURE 12 ) have been provisionally attributed to this taxon. Their crown morphologies are quite different with the smallest one ( Figure 12D View FIGURE 12 ) being non cuspidate, with a unique secondary crest parallel to transversal keel. The largest teeth ( Figure 12E View FIGURE 12 ) exhibit a slight ornamented enameloid on their labial face, but no ridge across the bombed transversal keel.
Remarks
By the lack of well-detached cusp, the presence of an enameloid ornamentation over the occlusal part of the lingual face and over the entire labial face of crown, the presence of a short root with well-detached root lobes where an unique labial foramen opens, this morphology reminds the dental condition characterizing Himantura uarnak (Cappetta, 2012, figure 411; non Herman et al., 1998, pl. 8-9) or some large species of Pateobatis (e.g., Pateobatis bleekeri ), which were previously included into Himantura (Last et al., 2016) . Cappetta (2012, figure 411) and Herman et al. (1998, pl. 8-9) both figured teeth of Himantura uarnak with very different design, the second showing minute teeth with few ornamented crowns and a secondary transverse crest (as in Figure 12D View FIGURE 12 ) when the first remind the tooth morphology of adults of Himantura souarfortuna nov. sp. ( Figure 12 View FIGURE 12 F-J). As noticed by Cappetta (2012, p.418), teeth illustrated by Herman et al (1998) probably correspond to the morphology of a juvenile of H. uarnak , thereby indicating a relative strong developmental heterodonty. We could suspect that some teeth (e.g., Figure 12 View FIGURE 12 D-E) represent similar ontogenetic stages in H. souarfortuna nov. sp. Marrama et al. (2018) figured embedded teeth from a skeleton of Protohimantura vorstmani (de Beaufort, 1926) from the Miocene of Indonesia. Juveniles of H. souarfortuna nov. sp. and H. uarnak share the same semi-ovoid or sub-hexagonal crown, with a second transverse keel that partially characterizes this Miocene urogymnin too. Himantura (and other new urogymnin genera sensu Last et al., 2016) are particularly scarce in the fossil record compared to Dasyatis , probably due to its misidentification with the former (see also the review of the fossil record of urogymnins by Marrama et al., 2018). Only two fossil species are known, they concern the Neogene Himantura menoni (Sahni and Mehrotra, 1981) and Protohimantura vorstmani. Sahni and Mehrotra (1981) always suggested that teeth of their Himantura menoni were similar to those of the living Indian species Pateobatis bleekeri (formerly Himantura bleekeri ), except that the transversal keel in the extinct H. menoni does not run up to the lateral edges, and the lingual and labial faces are different in size. By this, H. menoni appears different from H. souarfortuna nov. sp. even if the latter has teeth that also resemble those of P. bleekeri (pers. observ. SA).
This new species testifies the occurrence of urogymnins sensu Last et al. (2016) since the Middle Eocene in western Tethys. Besides, it confirms the spatial and temporal dynamics of Urogymninae , substantiating an eastward movement of the fossil occurrences from the Tethys during the Eocene to the tropical Indo-Australian Archipelago after the Oligocene, where they are particularly well-represented today (Marrama et al., 2018). We provisionally referred this new species to the '"informal" genus Himantura pending more accurate figurations from neontologists because several species of Himantura have been recently attributed to other genera (e.g., Pateobatis ) by Last et al. (2016).
Specimens repositories. Holotype and Paratypes are deposited in the paleontological collections of the museum of the “ Office National des Mines ” of Tunis , 24 rue 8601, 2035 La Charguia, 1080 Tunis, Tunisia
Temporal range. Middle Bartonian ( Tunisia).
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.