Ouledia lacuna, 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/626F6DD8-45BE-4245-A07F-456550BFE876 |
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taxon LSID |
lsid:zoobank.org:act:626F6DD8-45BE-4245-A07F-456550BFE876 |
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treatment provided by |
Felipe |
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scientific name |
Ouledia lacuna |
| status |
sp. nov. |
Ouledia lacuna nov. sp.
Figure 11 View FIGURE 11 A-C zoobank.org/ 626F6DD8-45BE-4245-A07F-456550BFE876
2007 Ouledia sp. ; Strougo et al., p. 88-94, pl.3, figs.
6-7.
?2008a Ouledia sp. ; Adnet et al., p. 338, figs. 2.3-4.
?2011 Ouledia sp. ; Underwood et al., p. 53-62, fig. 7J 2011 Ouledia sp. ; Adnet et al., p. 35, fig. 4L-N.
2016 Ouledia sp. ; Merzeraud et al., p. 14-15, tab. 1.
Etomology. Derived from Latin “lacuna ” for lagoon that the new species preferentially frequented.
Type locality and stratum. KEB 1-180 ( Figure 11A View FIGURE 11 ), from Souar-Fortuna Formations in Djebel el Kébar, Amamria hamlet near Soug-Jedid village (Sidi Bouzid Township), Tunisia: locality named KEB- 1 in Merzeraud et al. (2016) and previously dated (radiometric K-Ar datings) as middle Bartonian (38.7 ± 1.0 Ma to 40.7 ± 1.1 Ma, covering the NP17) in Marivaux et al. (2014a) .
Other material. Additional material, including figured KEB 1-181 to 1-182 ( Figure 11 View FIGURE 11 B-C), mainly consists of about 100 teeth from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.
Diagnosis. Fossil species of Ouledia known by uncupsided teeth with combination of characters that distinct the new species from O. sigei and O. casieri : a crown extremely narrow above the neck in uncuspided teeth with an occlusal surface never marked by a large mesio-distal furrow, a smooth enamel excepted on the lingual face of crown with the frequent development of fine alveolar network, a root always longer mesiodistally to the crown with two rounded lobes, hardly separated by a narrow groove.
Description
Teeth (including holotype) are small, not reaching more than 1.5 mm in height and width. There is no evidence of any dental sexual dimorphism in our large sample, having only female design (or male during non breeding period) without slender cusp. Crown and root are well differentiated by a slightly constricted neck. The root is always wider than crown. Teeth bear a thin, ovate crown in occlusal view ( Figure 11A View FIGURE 11 1, B1 View FIGURE 1 ), which is always much longer labiolingually than it is wide mediodistally. The unique mesio-distal crest is sharp edged, rectilinear ( Figure 11A View FIGURE 11 1, B1 View FIGURE 1 ) in occlusal view, and slightly concave in lingual or labial views ( Figure 11A View FIGURE 11 2, B2 View FIGURE 2 , C 1 View FIGURE 1 ), separating the labial face from the lingual face of the crown. The lateral angles of the crown are more or less sharp. The enamel is smooth, except behind the crown-root boundary where it may be slightly ornamented with alveolar net of folds on the lingual face ( Figure 11A View FIGURE 11 3 View FIGURE 3 ). The root is bilobate, displaced lingually ( Figure 11A View FIGURE 11 4 View FIGURE 4 ), as long as wide and massive. The root lobes are suboval or subrounded with a lingual face much more widely expanded than the labial face. The basal face is flat to slightly rounded, with a narrow medial groove preferentially marked on its lingual edge ( Figure 11B View FIGURE 11 2 View FIGURE 2 , C 1 View FIGURE 1 ), and bears a well-defined and large notch on its labial edge ( Figure 11A View FIGURE 11 1, B1 View FIGURE 1 , B 3 View FIGURE 3 ).
Remarks
Widely distributed despite its low abundance in most of the fossil-bearing localities, only two species have been described in Early Eocene deposits where specimens are more numerous. Regardless of the absence of typical teeth of male with cusp in our sample, this new species is nevertheless distinct from the type species Ouledia sigei Cappetta, 1986 , from the late Ypresian of Morocco, in showing a crown narrower above the neck in female teeth, a root always longer mesiodistally to the crown with two rounded lobes, hardly separated by a narrow groove. It is also distinct from Ouledia casieri (Kumar and Loyal, 1987) from the Ypresian of the lower Subathu Fm., India (Kumar and Loyal, 1987), in having an occlusal surface of the crown never marked by a large mesio-distal furrow, making a confined depressive basin in female teeth, and in having smooth enamel on the occlusal surface. Underwood et al. (2011) reported that rare examples of teeth of Ouledia are present throughout the section of Wadi al Hitan, Egypt, becoming more common only in the youngest deposits of QS. The latter authors figured only one tooth (Underwood et al., 2011, figure 7J from BQ) that corresponds to a “female” design, comparable to those observed in all specimens of Ouledia lacuna nov. sp. Being particularly worn, figure of Egyptian specimen does not allow to confirm the presence, or not, of the unusual ornamentation of the enameloid as observed in the material from KEB-1. From a close locality KM, Adnet et al. (2011, figure 4L-M) figured male and female teeth of Ouledia sp. Unfortunately, the scarce specimens from KM, also comparable to female teeth observed in EG and KEB, do not permit to conclude about the tooth morphology of the male teeth. Strougo et al. (2007) reported the presence of Ouledia at EG. The material from EG is as abundant as the Kebar sample (pers. observ. SA), and teeth with female design are entirely comparable to the material from KEB-1. Very scarce teeth (1%) with male design (cuspided crown) were observed in EG. There is no doubt that the specimens of Ouledia from EG belong to the same KEB-1 new species. Without considering the diagnostic morphology of the occlusal surface of the crown of O. casierii , and despite the surprising lack of tooth with breeding male design in KEB samples, this species of Ouledia (as those from Myanmar in Adnet et al., 2008b, and those of southwestern Morocco in Adnet et al., 2010) is rather strongly reminiscent to the Indian species compared to Moroccan species O. sigei .
This ambiguous gymnurid genus, sometimes considered as an extinct filter feeder (Underwood et al., 2011) and/or tolerant to fresh water inflow (Adnet et al., 2008), seems to represent a diverse component of the nearshore ecosystems of all equatorial seas during the Paleocene (Cappetta, 2012; Louterbach et al., 2014) and Eocene, from Peru (Louterbach et al., 2014) to Myanmar (Adnet et al., 2008b). Absence of cuspid teeth usually attributed to (breeding) male in KEB remains unaccountable unless this could reflect a strong spatial segregation of male outside lagoons, at least during the breeding season.
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