Leptocharias tunisiensis, 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/075E7036-4A5C-4E78-B634-F3F8F141C788 |
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taxon LSID |
lsid:zoobank.org:act:075E7036-4A5C-4E78-B634-F3F8F141C788 |
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treatment provided by |
Felipe |
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scientific name |
Leptocharias tunisiensis |
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sp. nov. |
Leptocharias tunisiensis nov. sp.
Figure 7 View FIGURE 7 F-K
zoobank.org/ 075E7036-4A5C-4E78-B634-F3F8F141C788
2002 Microscyliorhinus leggeti Case ; Mustafa and Zalmout, p.83, pl. 1, figs.12-14.
2007 Scyliorhinus sp. ; Strougo et al., p. 88-94.
2011 Leptocharias sp. ; Underwood et al., p. 52-62, tab. 1, figs. 6F-G.
2011 Crassescyliorhinus sp. ; Underwood et al., p.
52-62, tab. 1.
2011 Scyliorhinus sp.1 ; Adnet et al., p. 33, fig. 3R 2016 Scyliorhinus sp 1 and 2; Merzeraud et al., p. 14- 15, tab. 1.
Etymology. From Tunisia where the type material originates.
Type locality and stratum. KEB- 1-138, Figure 7F View FIGURE 7 from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.
Other material. Additional material, including figures KEB 1-139 to 1-143 ( Figure 7 View FIGURE 7 G-K), mainly consists of about 60 upper and lower teeth from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.
Diagnosis. Fossil species of Leptocharias characterized by a disjunctive monognathic heterodonty with partial overlapping of alternate files as observed in the living representative Leptocharias smithii . Antero-lateral teeth with high cusp curved distally and slightly a folded enameloid, twice as large as anterior teeth. Posteriors are quite symmetrical resembling those of scyliorhinid with plicate enameloid. This fossil species is, however, distinct in having lateral teeth with more stocky design, a well-marked overlapping surface on the labial part of the root, a lesser ornamented enamel of the crown in posterior teeth, and in a hemiaulacorhize vascularization of the root.
Description
The holotype is an antero-lateral lower tooth ( Figure 7F View FIGURE 7 ), probably from the third position following the dentition pattern of the living representative ( Leptocharias smithii ). Lower antero-lateral teeth are larger, more robust and highly asymmetrical compared with similar files of upper jaw ( Figure 7G View FIGURE 7 ). The main cusp is straight, robust, elongated beyond the distal root extremity, and strongly inclined toward the jaw commissure. A single pair of lateral cusplets is present but poorly developed and slightly turned off lingually. The two cutting edges are well developed from base to apex of the main cusp, the mesial one being slightly sigmoidal ( Figure 7F, H View FIGURE 7 ) to straight ( Figure 7G View FIGURE 7 ), probably depending of sex (Herman et al., 1991). In antero-lateral files, the labial ornamentation of crown is absent (on the holotype) or weak, and limited to the lateral extremities of the crown (on upper antero-lateral teeth; Figure 7G View FIGURE 7 1 View FIGURE 1 ). The lingual face of the principal cusp is strongly convex in profile ( Figure 7F View FIGURE 7 1 View FIGURE 1 ), and the ornamentation is fine, more regular with some ridges reaching the cusp apex. The root is very bulky, high and moderately wider than the crown. The root vascularization is always at a hemiaulacorhize stage in the available material, i.e., the medio internal foramen opens on the posterior part of the bulging lingual protuberance, offset relative to cusp, when the medio-external foramen opens on edge between basal and labial faces of the root. The root lobes are clearly asymmetrical and have strongly angular profile ( Figure 7F View FIGURE 7 1 View FIGURE 1 ) with several foramina, sometimes very large, opening on both side of the lingual protuberance. The labial part of the root is thinned compared with the rest, delimiting in fact a labial overlapping surface, which probably interlocked on the lingual protuberance of tooth from previous row.
In the more anterior files (e.g., Figure 7G View FIGURE 7 ), near the parasymphyseal, teeth show a morphology that reminds that of the laterals (see below); except that the crown is without any labial ornamentation, as it does in living representatives. In the lateral and posterior teeth ( Figure 7 View FIGURE 7 J-K) from both jaws, the crown has a medium to low principal cusp depending position of tooth in jaw, which is more or less inclined toward the commissure. A pair of well-developed mesial and distal cusplets is present, with sometimes a poorly developed second cusplet in the mesialmost region. Both cutting edges are well developed as in anterior files. The labial face of the crown, fully ornamented and bifid, largely overhangs the root lobes at both ends, as observable in occlusal view ( Figure 7J View FIGURE 7 3 View FIGURE 3 ). The ornamentation strengthens as more the tooth is located toward the jaw commissure ( Figure 7K View FIGURE 7 ). The lingual faces are always finely ornamented, as in antero-lateral files. The root vascularization is at a hemiaulacorhize stage (e.g., Figure 7J View FIGURE 7 2 View FIGURE 2 ), and shows two long and broad lobes, quite symmetrical, which are angular at the base. The overlapping surface, as observed in more anterior teeth, is less developed and reduced with respect to the extreme labial edge of the root basal face ( Figure 7J View FIGURE 7 2 View FIGURE 2 ). As in more anterior files, some large foramens open on both side of a large lingual protuberance.
Remarks
Herman et al. (1991) described in details the tooth morphology of this monotypic family. They noted that “except for the parasymphysial rows, a disjunct monognathic heterodonty is presented by anterior teeth, with a high principal cusp strongly oriented obliquely toward the commissure and much smaller lateral and posterior teeth with a slightly oblique principal cusp” (Herman et al., 1991, p. 76). In addition, Underwood and Ward (2008) suggested that large, angular, and highly asymmetrical root of Leptocharias could be then regarded as a character unique to this genus. In fact, as previously reported by Herman et al. (1991), this concerns only the antero-lateral teeth, and especially on the lower jaw of male leading to a very important disjunctive monognathic heterodonty (Herman et al., 1991; Cappetta, 2012). As the most lateral and posterior teeth are less asymmetrical with cusps slightly oblique, their distinction from scyliorhinid becomes more delicate. However, based on the tooth morphology and heterodonty of numerous fresh specimens available in our collections (e.g., Appendix 1), the genus is also characterized by a slight overlapping of its tooth rows, marked by a depressed labial part of the root compared to the lingual part, and especially to the robust lingual protuberance (= angular root of Herman et al., 1991 and Underwood and Ward, 2008). If we can observe this dental trait on the lateral teeth of both jaws of living Leptocharias , this feature tends to disappear on teeth near the jaw commissure. Confusion with scyliorhinids is obvious, especially in the fossil record that has proven to be scarce.
Strougo et al. (2007) reported at least two species of Scyliorhinus in GE. A re-examination of the material (pers. observ. SA.), led us to consider that a part of the material, unfortunately badly preserved, could actually belong to Leptocharias tunisiensis nov. sp. Underwood et al. (2011, text only) reported in the same levels of Wadi al Hitan (from MI to lower QS), the presence of typical antero-lateral teeth of Leptocharias (Underwood et al., 2011, Figure 6 View FIGURE 6 F-G from BQ) and robust teeth with a scyliorhinid pattern that they attributed to the Cretaceous genus Crassescyliorhinus Underwood and Ward, 2008 (in text only). The authors probably confused the latter with lateral and posterior teeth of Leptocharias as illustrated here. If confirmed, the material from Wadi al Hitan attributed to Crassescyliorhinus and Leptocharias are likely to be conspecific and could be assigned to L. tunisiensis nov. sp. considering the tooth morphology of figured antero-lateral teeth. Mustafa and Zalmout (2002) reported in Late Eocene of Jordan the occurrence of Microscyliorhinus leggetti Case 1994 , an Early Eocene species from Mississipi, USA, based on large scyliorhinid teeth (up to 5 mm). By the characters described in their text and despite a low-quality illustration, this record can be assigned to Leptocharias as well.
Leptocharias tunisiensis nov. sp. clearly differs from the unique fossil species of Leptocharias , Leptocharias cretaceus Underwood and Ward, 2008 in its own teeth bearing a strong ornamention of the crown, low cusp (compared to the width of the root), even in antero-lateral files, and in a flatter basal face of the root (sometimes at anaulacorhize stage). If the latter undoubtedly represents the oldest record of the Leptochariidae with the presence of a depressed labial part of the root (“root lobes with ‘corners’ projecting labially and linguolaterally” in Underwood and Ward, 2008, p. 529), both the morphology and ornamentation of the crown (especially in antero-lateral tooth files) is, however, sufficiently different from other Leptocharias representatives to belong to another, unnamed genus. A distinction between L. tunisiensis nov. sp and the living species Leptocharias smithii is more tenuous, because both taxa share the same peculiar heterodonty pattern, the same antero-lateral teeth morphology and the same variability in crown ornamentation. However, L. tunisiensis nov. sp. possesses teeth that are distinct in being more robust in aspect, in showing a labial face of the crown more bifid, with fainter ornamentation on lateral to posterior teeth.
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. Uppermost Lutetian-lowermost Bartonian ( Egypt), middle Bartonian ( Tunisia), and possibly to late Priabonian ( Egypt, Jordan).
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.
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