Stroboceras ancilis, Korn & Bockwinkel, 2022
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publication ID |
https://doi.org/ 10.5852/ejt.2022.831.1871 |
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publication LSID |
lsid:zoobank.org:pub:EAA2EAE2-DA8B-4516-B332-CB8423B8EEAA |
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DOI |
https://doi.org/10.5281/zenodo.6903207 |
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persistent identifier |
https://treatment.plazi.org/id/BA91AA8E-DD89-4E1E-8781-0BF2ADB763E1 |
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taxon LSID |
lsid:zoobank.org:act:BA91AA8E-DD89-4E1E-8781-0BF2ADB763E1 |
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treatment provided by |
Felipe |
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scientific name |
Stroboceras ancilis |
| status |
sp. nov. |
Stroboceras ancilis sp. nov.
urn:lsid:zoobank.org:act:BA91AA8E-DD89-4E1E-8781-0BF2ADB763E1
Figs 11–12 View Fig View Fig , Table 6
Diagnosis
Species of Stroboceras with weakly depressed, rounded-trapezoidal whorl profile (ww/wh ~ 1.40), venter flat, ventrolateral shoulder angular with sharp longitudinal ridges. Whorls weakly embracing. Whorl profile with a wide longitudinal groove on the outer flank near the ventrolateral margin and a midflank longitudinal ridge.
Etymology
From the Latin noun ‘ ancilis ’, meaning ‘shield’ and referring to the whorl profile.
Type material
Holotype ALGERIA • Sebkha de Timimoun 14.5 km west-southwest of Timimoun (locality TIM-C8); Argiles de Timimoun supérieur (Upper Bollandoceras Assemblage ; early to middle Viséan); Korn et al. 2002 Coll.; illustrated in Fig. 11C View Fig ; MB.C.30459.1 .
Paratypes ALGERIA • 4 specimens; Sebkha de Timimoun 14.5 km west-southwest of Timimoun (locality TIM-C8); Argiles de Timimoun supérieur (Upper Bollandoceras Assemblage ; early to middle Viséan); Korn et al. 2002 Coll.; MB.C.30459.2 – MB.C.30459.5 .
Description
Holotype MB.C.30459.1 is a phragmocone fragment of a quarter whorl without shell preservation ( Fig. 11C View Fig ). It has a depressed pentagonal whorl profile and is widest at about the middle of the flank. The outer half of the flank is occupied by a shallow longitudinal groove, delimited on the ventral side by an angular ventrolateral shoulder and on the umbilical side by a rounded ridge. On the venter, near the ventrolateral shoulder, there is a finer ridge accompanied on both sides by a shallow longitudinal groove. The venter is slightly concave. The umbilical wall is oblique and almost flat; it ends at the umbilical seam. There is a small, very shallow dorsal whorl zone ( Fig. 12A View Fig ).
The suture line shows four rounded lobes each on the venter, flank, umbilical wall and dorsal whorl zone ( Fig. 12B View Fig ). Of these, the rounded V-shaped external lobe is the deepest; the lateral lobe is somewhat asymmetrical and broadly rounded and the lobe on the umbilical wall is shallow. The internal lobe is small and broadly V-shaped.
The paratypes show little variation in conch shape and suture line. The ww/wh ratio is between 1.30 and 1.40 in all specimens and the whorl profile has a very similar shape. Paratype MB.C.30459.2 ( Fig. 11B View Fig ), however, shows slightly more sharply defined longitudinal ridges; its suture line ( Fig. 12D View Fig ) has slightly shallower lobes than the holotype.
Paratype MB.C.30459.3 is a heavily corroded specimen 37 mm in diameter ( Fig. 11A View Fig ). Although incomplete, it shows the general advolute conch form with whorls touching the preceding.
Remarks
Stroboceras ancilis sp. nov. differs from all other species of the genus by its almost rectangular whorl profile with a right-angled ventrolateral shoulder.
Table 6. Conch dimensions (in mm) and ratios of Stroboceras ancilis sp. nov.
| Specimen | dm | ww | wh | uw | ah | ww/dm | ww/wh | uw/dm | WER | IZW |
|---|---|---|---|---|---|---|---|---|---|---|
| MB.C.30459.3 | 36.6 | 16.8 | 12.1 | 15.1 | 12.1 | 0.46 | 1.39 | 0.41 | 2.23 | 0.00 |
| MB.C.30459.1 | – | 12.5 | 9.2 | – | – | – | 1.36 | – | – | – |
| MB.C.30459.2 | – | 10.7 | 7.8 | – | – | – | 1.37 | – | – | – |
| MB.C.30459.4 | – | 10.8 | 8.0 | – | – | – | 1.36 | – | – | – |
| MB.C.30459.5 | – | 7.5 | 5.7 | – | – | – | 1.31 | – | – | – |
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