Calygirtyoceras darkaouaense Korn, Klug, and Mapes, 1999
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publication ID |
https://doi.org/ 10.4202/app.00220.2015 |
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DOI |
https://doi.org/10.5281/zenodo.10989676 |
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persistent identifier |
https://treatment.plazi.org/id/03E087FC-FFC5-FFC9-1809-FB25FAC3F9E8 |
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treatment provided by |
Felipe |
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scientific name |
Calygirtyoceras darkaouaense Korn, Klug, and Mapes, 1999 |
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Calygirtyoceras darkaouaense Korn, Klug, and Mapes, 1999 View in CoL
Fig. 5 View Fig .
Holotype: GPIT 1851-87 View Materials ; Korn et al. 1999: pl. 1: 7.
Type locality: 12 km southeast of Dar Kaoua, southeast of Erfoud, eastern Anti-Atlas, Morocco.
Type horizon: Early late Viséan ( Entogonites assemblage).
Material.— 6 specimens: three juvenile conchs in PIMUZ 31509 View Materials , PIMUZ 31516 View Materials , PIMUZ 31519 View Materials ; two additional juveniles in PIMUZ 31508 View Materials ; an incomplete adult specimen with septal crowding in PIMUZ 31513 View Materials .
Emended diagnosis (modified after Korn et al. 1999).— Calygirtyoceras with a juvenile cadiconic conch (dm 5–10 mm; ww/dm 0.60–0.71), a transitional discoidal, platyconic preadult conch shape and a large, thinly discoidal, oxyconic adult conch (dm 100–150 cm; ww/dm 0.30–0.40). Umbilicus very wide in juvenile growth stages (uw/dm 0.08; dm 5–10 mm) and very narrow near adulthood (uw/ dm 0.10–0.15; dm> 50 mm). Whorl expansion rate very low in juvenile whorls (dm <10 mm) and increasing to almost 3 at> 50 mm diameter. Adult ornamentation with fine, crenulated growth lines with biconvex and slightly rursiradiate course. Suture line with low median saddle (median saddle width/height ratio 0.30), broadly rounded ventrolateral saddle, and narrow external lobe (external lobe width/height ratio 0.55).
Description.—PIMUZ 31516 ( Fig. 5B View Fig ) is a cadiconic juvenile with a thinly to thickly globular, very evolute conch. The whorl cross section is strongly depressed with a hardly vaulted venter; at the thickest part of the flanks, 12–15 small nodes are developed at a diameter below 10 mm per half whorl. In the subsequent ontogenetic stage, the venter becomes more and more vaulted and rounded. At a whorl height of about 30 mm (PIMUZ 31513), the cross section becomes subtriangular with gently rounded flanks. PIMUZ 31513 is a fragment of an adult conch (septal crowding at dm ca. 110 mm). At this stage, the conch is extremely discoidal and involute ( Table 3 View Table 3 ). In this specimen, the external lobe is incompletely visible but V-shaped with a high ventrolateral saddle as present in the type-material. The V-shaped adventive lobe is inclined dorsally with a convex ventral flank.
Remarks.—In the original species diagnosis by Korn et al. (1999), the ontogenetic changes were described in a somewhat misleading way: in the same article, we ( Korn et al. 1999: p. 354) had stated that the “Umbilicus [is] very narrow in early growth stages (uw/dm = 0.08 at 20–30 mm dm) and slightly opening during ontogeny (stages (uw/dm = 0.10 to 0.12 at 40–60 mm dm).” When measuring the umbilical width throughout the entire post-hatching ontogeny, a rather constant reduction of the uw/dm ratio from 0.62 to 0.14 was measured. Also, the latest growth stage was unknown previously.
Stratigraphic and geographic range.—Early late Viséan, so far only known from the Tafilalt ( Morocco).
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