Sansabella gelaohensis Guillam & Forel & Song & Crasquin 2022, sp. nov.

Sansabella gelaohensis Guillam & Forel sp. nov. urn:lsid:zoobank.org:act: 7626056B-A0B0-41BE-AC1D-308F2A935888 Fig. 7G–N Sansabella sp. Coen, 1989: pl. 2 fig. 11. Diagnosis Smooth Sansabella species with a convex free margin, strong ventral overlap, a postero-ventral spine at LV, hinge line straight, occupying entire dorsal margin. Etymology The specific epithet refers to the Gelaohe Formation in which all the specimens were found. Material examined Holotype CHINA • 1 complete carapace (Fig. 7G); Blue Snake section, Gelaohe Formation, sample 19BAI 74; Famennian, late Devonian; P6M 3882. Paratypes CHINA • 1 complete carapace (Fig. 7 H); Blue Snake section, Gelaohe Formation, sample 19BAI 74; P6M 3883 • 1 complete carapace (Fig. 7I); Blue Snake section, Gelaohe Formation, sample 19BAI 74; P6M 3884. All from the Famennian, late Devonian. Other material CHINA • 1 complete carapace (A-1, Fig. 7J); Blue Snake section, Gelaohe Formation, sample 19BAI 74; P6M 3884 • 1 complete carapace (A-2, Fig. 7K); Blue Snake section, Gelaohe Formation, sample 19BAI 74; P6M 3885 • 1 complete carapace (A-3, Fig. 7L); Blue Snake section, Gelaohe Formation, sample 19BAI 74; P6M 3886 • 1 complete carapace (A-4, Fig. 7M); Blue Snake section, Gelaohe Formation, sample 19BAI 63; P6M 3887 • 1 complete carapace (A-5, Fig. 7N); Blue Snake section, Gelaohe Formation, sample 19BAI 63; P6M 3888 • 98 carapaces; Blue Snake section, Gelaohe Formation, samples 19BAI 60, 19BAI 63, 19BAI 67–69, 19BAI 74. All from the Famennian, late Devonian. Dimensions See Fig. 4B. Description Carapace large, subcircular in lateral view, slightly preplete, with Lmax above mid-H. RV larger than LV, overlapping it all around with maximum along VB and interruption at DB directly posterior to ACA. Hinge line straight, invaginated, occupying entire dorsal margin and equivalent to about 70% of the Lmax. Dorsal margin straight. Cardinal angles blunt, ACA about 135°, PCA about 130°. Ventral margin largely convex at both valves. Left valve with a short latero-ventral spine, slightly posterior to mid-L. AB largely convex with maximum of convexity around mid-H. PB from narrowly rounded in juveniles to close to vertical in adults, with maximum of convexity around the upper ⅓ rd of H. Shallow sulcus opened dorsally sometimes visible, located in front of mid-L, never extending below mid-H. Node sometimes visible, located in the antero-dorsal part of carapace, just in front of the sulcus. Juveniles morphologically similar to adults except for the size, morphology of PB and less developed ventral spine. Carapace smooth. Remarks This species, identified as Sansabella sp., was only briefly described by Coen (1989) from a sample from the Famennian, late Devonian, Gelaohe Formation of Baihupo section, Dushan County. Sansabella gelaohensis sp. nov. differs from the majority of species belonging to Sansabella Roundy, 1926 by its subcircular lateral outline. More precisely, it differs from Sansabella amplectans Roundy, 1926 from the Mississippian of Texas (Roundy 1926) in which the larger valve is the left one and has a parallelogram lateral outline. Sansabella gelaohensis sp. nov. also differs from Sansabella polonica Błaszyk & Natusiewicz, 1973 from the Tournaisian of Poland (Błaszyk & Natusiewicz 1973) which has a longer trapezoidal carapace, a reticulate surface with a more distinct sulcus at both valves which begins in the medial part of the DB. Sansabella sinuoventralis Lethiers, 1981 from the Famennian of Western Canada (Lethiers 1981) has a more convex VB. Sansabella? curiosa Stewart & Hendrix, 1945 from the Upper Devonian of Ohio (Stewart & Hendrix 1945) has LV larger than RV, H practically uniform throughout its L, a less convex VB, a granulate or reticulate ornamentation. The H/L scatter plot (Fig. 4B) does not allow to discriminate different ontogenetic stages but the wide distribution of the dimensions of the specimens clearly indicates that several stages are present in the assemblages studied. Occurrence Gelaohe Formation, Baihupo section, Dushan, Guizhou, South China, Famennian, late Devonian (Coen 1989). Samples 19BAI 60, 19BAI 63, 19BAI 67-69, 19BAI 74, Gelaohe Formation, Blue Snake section, Famennian, late Devonian (this work).

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