Latibrachythyris rotundata ( Sowerby, 1825 )
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https://doi.org/ 10.4202/app.00972.2022 |
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https://treatment.plazi.org/id/41708783-FFFF-FF92-8C8B-C820FAD1FE08 |
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Felipe |
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Latibrachythyris rotundata ( Sowerby, 1825 ) |
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Latibrachythyris rotundata ( Sowerby, 1825)
Fig. 16B–D View Fig .
1825 Spirifer rotundatus ; Sowerby 1825: 89, pl. 461: 1.
1859 Spirifera pinguis Sowerby, 1821 a ; Davidson 1859: 50 (pars), pl. 10: 2, 4.
1859 Spirifera pinguis Sowerby, 1821 a var. rotundata Sowerby, 1825 ; Davidson 1859: 50, pl. 10: 8–12.
2011 Latibrachythyris rotundatus ( Sowerby, 1825) ; Angiolini et al. 2011: 79, figs. 5, 6N –O. (cum syn.)
Material.—Two articulated specimens: MPUM 12043 ( RCK 15-1a); MPUM 12044 ( RCK 15-5). Six ventral valves: MPUM 12045 ( RCK 15-40); MPUM 12046 ( RCC 1B-26c; RCC 43-6; RCC 45-2; RCC 48-24; RCC 129-1). One dorsal valve: MPUM 12047 ( RCC 65G-12). One fragment: MPUM 12048 ( RCC 60-50). All from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.
Description.—Small, ventribiconvex shell with suboval outline; cardinal margin straight, wide, two-thirds of the maximum width. Commissure gently uniplicate. Ventral umbo curved; interarea apsacline, low. Delthyrium lacking deltidial plates. Distinct median sulcus starting as a furrow from umbo, becoming low and broadly rounded anteriorly. Dorsal umbo straight; interarea orthocline to gently anacline, very low. Fold starting at one-third shell length, low, rounded.
Ventral valve covered by 12–14 simple, broad, rounded lateral costae extending from the umbo, with narrow interspaces. One faint pair of costae in the sulcus bifurcating from sulcus-bounding costae at 4.0–6.0 mm from the umbo; sulcal median costa absent. Dorsal valve covered by 10–12 simple lateral costae extending from the umbo. Fold smooth. Micro-ornamentation of faint irregular growth lamellae.
Remarks.—The specimens differ from the ones of Latibrachythyris rotundata studied by Angiolini et al. (2011) in being smaller and in being strongly ventribiconvex. However, both the morphology and the ornamentation of the specimens are in the variability shown by L. rotundata , so they probably are juvenile specimens of the species. The specimens are not considered as juveniles of L. cf. crassa , as they lack the pattern of numerous ribs of different width that is described in the specimens from Ricklow Quarry assigned to it.
The specimens differ from L. pinguis in having a less convex and enrolled ventral valve, a less defined sulcus and in being more transverse. Moreover, in L. pinguis the cardinal margin is relatively wider and the interarea is more trapezoidal ( Angiolini et al. 2011).
Stratigraphic and geographic range.— Latibrachythyris rotundata is recorded in the upper Tournaisian–Visean of Ireland and England and in the Tournaisian–Visean of Belgium (e.g., Davidson 1859; Angiolini et al. 2011; this study).
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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Latibrachythyris rotundata ( Sowerby, 1825 )
| Carniti, Alessandro P., Porta, Giovanna Della, Banks, Vanessa J., Stephenson, Michael H. & Angiolini, Lucia 2022 |
Latibrachythyris rotundatus ( Sowerby, 1825 )
| Angiolini, L. & Long, S. & Davies, L. 2011: 79 |
Spirifer rotundatus
| Sowerby, J. de 1825: 89 |