Coledium bruntoni, Sun & Baliński, 2011
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publication ID |
https://doi.org/ 10.4202/app.2010.0106 |
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persistent identifier |
https://treatment.plazi.org/id/03BB9544-FFBE-A66F-FF2A-F9809C72FB3A |
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treatment provided by |
Felipe |
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scientific name |
Coledium bruntoni |
| status |
sp. nov. |
Coledium bruntoni sp. nov.
Figs. 11 View Fig , 12 View Fig .
Etymology: In honour of the late Dr. Howard C.H. Brunton (1935– 2008), eminent brachiopodologist.
Holotype: Complete shell PKUM02−0426 illustrated in Fig. 11A View Fig .
Type locality: Muhua section, between villages of Muhua and Gedongguan (Guizhou province, South China).
Type horizon: Muhua Formation, correlated with the middle Tournaisian Lower Siphonodella crenulata conodont Zone.
Diagnosis.— Coledium with subpentagonal outline, flattened or concave ventral flanks, well developed posteriorly but lower anteriorly ventral sulcus, and recurved posterolateral
http://dx.doi.org/10.4202/app.2010.0106
ventral margins; dorsal valve about twice as convex as the ventral one, with posteriorly low but anteriorly conspicuous fold; up to 5 ribs on each ventral flank, and up to 3 ribs in the sulcus; flank ribs frequently forms distinct spurs at valve margins. From the most similar Coledium evexum Grant, 1965 differs by having a larger, wider, less ventrally inflated shell, and less steep cardinal margins.
Material.— Two complete and two slightly damaged shells and several fragments of disarticulated valves from sample MH1 . Dimensions of the holotype (in mm): length 8.6, width 9.6, thickness 6.5 .
Description.—Shell attains up to 15.2 mm in width, widest posteriorly at one−third total length, dorsibiconvex, subpentagonal in outline; cardinal extremities smoothly rounded, anterior margin straight or slightly emarginate, anterior commissure uniplicate, valve margins may be slightly geniculate and concentrically undulate because of several growth halts.
Ventral valve pentagonal in outline, slightly convex, with flattened or concave flanks; sulcus begins near the umbo where it is well delineated, more anteriorly it becomes poorly defined; tongue observed in large specimens only; beak suberect, interareas absent, posterolateral margins of the valve strongly recurved and overlapped by the edges of the dorsal valve ( Fig. 11B View Fig ).
Dorsal valve about twice as convex as the ventral one; fold poorly defined, becoming quite conspicuous in the anterior half of the valve.
Interior of ventral valve with a wide, dorsally concave spondylium attaining about 2.5 mm in length and supported by a low median septum. Dorsal interior with a weakly concave camarophorial plate supported by the median septum; median septum highest anteriorly ( Fig. 12 View Fig ); intercamarophorial plate and cardinal process (ctenophoridium) present ( Fig. 12B, D View Fig ).
Costae impersistent, very low, delicate and wide, on some specimens they are more strongly developed on the posterior region of the shell; in large specimens flank costae are very strong at the shell margin, where they develop long spurs; when present on both valves they project ventrally and dorsally at right angles to the valve surfaces; up to 5 ribs on each ventral flank, and up to 3 ribs in the sulcus.
Remarks.—The presence of a distinct spondylium and camarophorium indicates that these specimens belong to the stenoscismatoid rhynchonellides. The presence of an intercamarophorial plate in the dorsal valve is important taxonomically. These features, in combination with the general aspects of the shell and its ornament indicate an assignment to Atribonium Grant, 1965 or Coledium Grant, 1965 . In the latter genus, however, the presence of stolidium is very characteristic, while it is absent in the former. Although this structure is not well preserved on the shells from Muhua, presence of several undulate growth halts ( Fig. 11A View Fig 5) at the valve margins is indicative of a stolidium and, in consequence, our material is attributed to the genus Coledium .
The described form is most similar externally to Coledium evexum Grant, 1965 from the Early Mississippian (Kinderhookian) of Central Texas, USA (see Grant 1965: 112–114, pl. 15: 1–10; text−fig. 26). However, the Chinese species can be distinguished readily from the later by having a larger, wider, less ventrally inflated shell, and less steep cardinal margins. Coledium bruntoni sp. nov. is similar in size, general outline, and slightly concave ventral flanks to Coledium altisulcatum Carter, 1967 from the Chappel Limestone (Mississippian) of central Texas (see Carter 1967: 308–310, fig. 5, pl. 22: 9–12) but differs in having stronger radial ornament and less inflated dorsal umbo.
http://dx.doi.org/10.4202/app.2010.0106
Stratigraphic and geographic range.—Known only from the type locality and horizon.
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