Amamriabatis heni, 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/F335D187-C316-4079-8904-FC516106743A |
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taxon LSID |
lsid:zoobank.org:act:F335D187-C316-4079-8904-FC516106743A |
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treatment provided by |
Felipe |
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scientific name |
Amamriabatis heni |
| status |
sp. nov. |
Amamriabatis heni nov. sp.
Figure 14 View FIGURE 14 A-G zoobank.org/ F335D187-C316-4079-8904-FC516106743A
?2011 aff. Burhnamia sp.; Underwood et al., p. 53-62, fig. 7B.
2016 Burhnamia sp.; Merzeraud et al., p. 14-15, tab.
1.
Etymology. In Honour to Mister Kamel Heni, citizen of Soug-Jedid, for his considerable help during the field seasons in the Djebel el Kébar area.
Type locality and stratum. KEB 1-219 ( Figure 14B View FIGURE 14 ) from the KEB-1 locality, Souar-Fortuna formations in Djebel el Kébar, Tunisia .
Other material. Additional material, including figured KEB 1-218, 1-220 to 1-224 ( Figure 14A View FIGURE 14 , C-G), mainly consists of fifty teeth, most usually broken and particularly damaged, from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.
Diagnosis. As that as the monotypic new genus.
Description
Teeth are medium sized (no more than 1 cm long) with a sub-hexagonal shape in occlusal view, extremely fragile, and easily breakable. The dentition seems similar to that of rhinopterids and some stem mobulids with teeth regularly decreasing in width from the symphysis toward the lateral tooth files (Cappetta, 2012; Underwood et al., 2017). The roots are usually unpreserved, often rolled and broken. The holotype ( Figure 14B View FIGURE 14 ) is most likely a tooth of the median tooth files, having a crown slightly wider than it is long. Its crown is relatively low, flattened and labiolingually extended with a possible surface wear, entirely flat and horizontal. The fine enameloid of the occlusal surface is almost smooth ( Figure 14C View FIGURE 14 1, B1, D1, E1 View FIGURE 1 ) to finely wrinkled ( Figure 14A View FIGURE 14 1, F1 View FIGURE 1 ). As observed in rhinopterid tooth plate, the labial visor and bulge are principally smooth and relatively sharp ( Figure 14C View FIGURE 14 3 View FIGURE 3 ), except on some largest specimens ( Figure 14F View FIGURE 14 ) where they can be irregular. However, and contrary to most of rhinopterids where the lingual face is regular and usually convex to fit the shape of the labial visor of incoming tooth row, the lingual face of Amamriabatis heni nov. gen. nov. sp. is narrower medially than laterally in lingual view (e.g., Figure 14B View FIGURE 14 2, D2 View FIGURE 2 , F 3 View FIGURE 3 ). It is also noticeably ornamented with numerous, strong and sinuous folds and grooves, as observable in the holotype in lingual view ( Figure 14B View FIGURE 14 2 View FIGURE 2 ). The deep ornamentation of this lingual face seems related to the moderate development of the transverse keel, which is oriented lingually as observable in some lateral teeth ( Figure 14A View FIGURE 14 3 View FIGURE 3 ), median teeth ( Figure 14B View FIGURE 14 2 View FIGURE 2 ), or anterior teeth ( Figure 14F View FIGURE 14 3 View FIGURE 3 ). However, in some teeth ( Figure 14D View FIGURE 14 2 View FIGURE 2 , D 3 View FIGURE 3 ) with particularly low crowns, the lingual face lacks these folds of enameloid. The transverse keel is sometimes salient lingually as in the holotype ( Figure 14B View FIGURE 14 1 View FIGURE 1 ), but it never extends toward the angular extremities of the crown, and it is often delimited by concave lateral borders, as particularly observed in the holotype ( Figure 14B View FIGURE 14 1 View FIGURE 1 ). The lingual salient border of the transverse keel is most often straight to slightly sinuous in occlusal view ( Figure 14B View FIGURE 14 1, F1 View FIGURE 1 ). The lower parts of the lingual and labial visors of the crown are relatively flat, horizontal, well developed, and form a continuous ring around the crown-root junction ( Figure 14A View FIGURE 14 2 View FIGURE 2 , B 3 View FIGURE 3 , C 2 View FIGURE 2 , D 3 View FIGURE 3 , F 2 View FIGURE 2 ). The polyaulacorhize root is rather fine, never longer than the crown length, and seems as lower than the crown elevation. It is formed by an alternation of broad and deep furrows, “U” shaped in section, and with no more than eight lamina, asymmetrical in shape and size. There is often a visible foramen in the middle of some furrows ( Figure 14A View FIGURE 14 2, C2, F2 View FIGURE 2 ).
Remarks
The tooth morphology of Amamriabatis nov. gen. is reminiscent to that of some basal mobulids, such as Burhnamia, Eoplinthicus , Oromobula and Argoubia (see Adnet et al., 2012; Underwood et al., 2017 for reviews). However, a suite of anatomical details allows for a clear distinction from the latter, which led us to propose this new genus. Contrary to the Middle Eocene Burhnamia, the occlusal face of the crown in Amamriabatis is flat and its enameloid is more smoothed. The transverse keel is more developed medio-lingually, and the labial visor is smooth and more regular where the lingual, labial and lateral faces of the crown in Burhnamia are somewhat concave and covered with fine, but well-developed granulations. Contrary to the Late Eocene Eoplinthicus, Plinthicus , Argoubia and Oromobula (and also the majority of the Recent Mobulidae with comb-like teeth), the crown of the teeth of Amamriabatis is lower, the transverse keel (when developed) is never dissected, and the labial visor is never deeply ornamented. With these characteristics, Amamriabatis displays an unusual dental pattern corresponding to a mosaic of characters observable in many rhinopterids (e.g., angular and smooth labial visor, flat occlusal surface of crown with sub-hexagonal outline) and many characters of stem mobulids (e.g., narrow root compared to crown, low number of irregular root lobes; presence of a transversal keel medially expensed on crown, irregular ornamentation of lingual face of crown limiting a strong interlocking of the tooth rows). The affinities with both families remain unclear, but considering that the majority of features are present in stem mobulids (like Burhnamia), we considered here that Amamriabatis nov. gen. belongs to the Mobulidae .
Another uncertainty concerns the monospecific genus Eomobula , which was originally described from a small tooth sample from the Lower Eocene of the Egem Fm. ( Belgium), but was secondarily recorded by rare specimens in some Early–Middle Eocene localities (e.g., Kemp, 1994; Gheerbrant et al., 2003; Tabuce et al., 2005). Having very small teeth, this genus was attributed to a mobulid despite its teeth that show a very large occlusal face compared to the extremely reduced lingual and labial faces and a wide polyaulacorhize root as in myliobatids and rhinopterids. Herman et al. (1989), authors of Eomobula , themselves remarked that there was no real affinity in tooth morphology with other mobulids such as Burhnamia or Mobula , and suggested that this primitive mobulid probably represents an intermediate group between living representatives of the Myliobatidae and Mobulidae . Even if Enault et al. (2013) were not able to perform the enameloid histology of Eomobula to clarify its high-level taxonomical status among the Myliobatiformes , this genus is currently regarded as a peculiar Myliobatidae sensu stricto (Cappetta, 2006; Adnet et al., 2012; Hovestadt and Hovestadt-Euler, 2013), or possibly as a juvenile of an unknown myliobatid. Whatever the future valid status of this genus among the Myliobatidae , Amamriabatis nov. gen. is clearly distinct from Eomobula in having a low number of irregular root lobes, the presence of a transversal keel medially expended on the crown, and in displaying an irregular ornamentation of the lingual face of crowns, as observable in valid stem mobulids.
Underwood et al. (2011) reported in upper QS the presence of an unnamed genus that seems very similar in many respects to Burnhamia (Underwood et al., 2011, figure 7B as aff. Burhnamia sp.). Despite its surface wear, it differs in having a flat occlusal face showing some degree of wear, and could represent a secondarily macrophageous relative of Burnhamia . This preliminary comparison with other Burhnamia seems in accordance with the diagnosic features of the new KEB- 1 mobulid genus described here.
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) to possibly Late Eocene ( Egypt).
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.