Globosochonetes sp.
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publication ID |
https://doi.org/ 10.4202/app.2008.0309 |
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persistent identifier |
https://treatment.plazi.org/id/1B17B006-D463-972A-2EC8-014441F0F9F9 |
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treatment provided by |
Felipe |
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scientific name |
Globosochonetes sp. |
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Fig. 11 View Fig .
Material.—One almost complete shell, 1 incomplete dorsal valve and 3 slightly broken ventral valves.
Description. —Small to medium in size, attaining 4–9.7 mm in width and 3.5–7.7 mm in length, semicircular in outline, slightly wider than long, with length:width ratio 0.73–0.80, greatest width near the hinge line; ears small and poorly developed; concavo−convex in lateral profile. Traces of three pairs of spines can be observed in one ventral valve, symmetrically arranged at an angle probably of less than 30 ° to hinge line. Shell surface with faint and fine radial costellae which increase by branching on ventral and intercalation on dorsal valve; seven costellae per mm at 3 mm distance from the ventral beak and 5.5–7 near mid−anterior margin.
Ventral valve moderately and evenly convex in lateral profile, the greatest convexity at one−third of valve length from the ventral beak; ventral interarea narrow, apsacline to orthocline with small pseudodeltidium.
Dorsal valve slightly concave posteriorly with gradually decreasing curvature to the anterior and lateral margins; dorsal interarea linear, hypercline; elongate protegular node prominent on the dorsal beak.
Teeth in the ventral valve not observed due to the preservation; short, probably high posteriorly ventral median septum is observed in one specimen; adductor scars indistinct; endospines very small and indistinct, confined to periphery of valve, arranged in radial rows corresponding to intercostal spaces.
Dorsal interior with small, bilobate trifid cardinal process, posteriorly directed, anteriorly with weak pit; inner socket ridges relatively weakly developed with only slight curvature and divergent anteriorly at 125–130 °; anderidia not clear; median septum absent; a pair of accessory septa long and plate−like, divergent anteriorly at about 15 °; endospines fine, evident in region lateral to the accessory septa.
Remarks.—The specimens here described are characterized by a weakly costellate external ornamentation with 7 costellae per mm at 3 mm distance from ventral beak, less concave lateral profile, relatively large shell size, large cardinal process without or with very weak pit, and a pair of long and high, plate−like accessory septa. The assignment of this material to the genus Globsochonetes is based mainly on shell outline and internal structures of the dorsal valve. It differs, however, from Globosochonetes gracilis sp. nov. described above, as well as from other species of the genus by having relatively faint radial costellae and by the absence of well developed cardinal process pit, as well as large shell size and less convex lateral profile. The current material may represent a new form of the genus but more material is needed to describe it satisfactory.
Stratigraphic and geographic range.—It was found in sample MH1 taken at the base of the Muhua Formation.
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