Rhyssochonetes, Johnson, 1970

Ma, Xue-Ping, Sun, Yuan-Lin, Hao, Wei-Cheng & Liao, Wei-Hua, 2002, Rugose corals and brachiopods across the Frasnian- Famennian boundary in central Hunan, South China, Acta Palaeontologica Polonica 47 (2), pp. 373-396 : 383-384

Rhyssochonetes ? sp. 2

Fig. 9C–E, S .

Material.—Over 50 complete shells.

Remarks. —The present shells have the following main characters: shell small, weakly to moderately concavoconvex, transversely oval; ventral interarea apsacline, with well developed pseudodeltidium; dorsal interarea catacline, with chilidium. The diagnostic features of this form are its hinge spines, which are orthomorph parallel (a character which are different from species of Rhyssochonetes ) and symmetrically arranged ( Fig. 9E, S ), and its ornamentation which consists of very weak radial parvicostellae and concentric undulating fila. Some specimens only show concentric undulating fila and others show both radial and concentric ornaments. This form is different from Rhyssochonetes ? sp. 1 in its much weaker surface ornament and less convex ventral valve. Its general features suggest an assignment to the Dagnachonetinae of the Chonetidae . However, its internal structures are unknown, hence its taxonomic affiliation cannot be established with certainty at present.

Occurrence.—Central Hunan Province; in the Shetianqiao section (sample S−H−0), late Frasnian.

Figures

Fig. 9. A, B. Rhyssochonetes? sp. 1, sample S−Y−2, ventral and dorsal views, PUM 00055; × 3. C–E, S. Rhyssochonetes? sp. 2, sample S−H−0. C. Ventral view, PUM 00062, × 3. D. Dorsal view showing the interarea, PUM 00048, × 5. E. Ventral view, note the orthomorph parallel arranged hinge spines (arrowed), PUM 00061b, × 3. S. Enlargement of arrowed area of E, × 11.5. F–H. Leioproductus hunanensis Liu, 1982, sample C−H, lateral, dorsal and ventral views, PUM 00031, × 2. I. Productella sp. 2, sample C1−0, dorsal view showing some spines present on the valve, PUM 00035, × 3. J, K. Productella lachrymosa var. asiatica Tien, 1938; sample C7. J. Ventral view, PUM 00002, × 1.5. K. Dorsal view, PUM 00032, × 2. L, M. Productella sp. 1, sample S−Y−4.L. Ventral view, PUM 00018, × 2. M. Dorsal view, PUM 00015, × 2. N–R. Praewaagenoconcha linglingensis (Wang, 1956), sample C−H. N. Dorsal view, PUM 00030, × 2. O. Dorsal view, PUM 00034, × 2. P, Q. Ventral and lateral views, PUM 00024; × 2. R. Dorsal interior showing the slit−like sockets, PUM 00059, × 3.3. T–V. Sinalosia rugosa gen. et sp. nov., sample S−Y−2. T. Showing the distinct interarea with ventral pseudodeltidium and dorsal chilidium, which is medially divided by cardinal process as to form a narrow V−shaped slit gap, PUM 01001, × 6. U, V. Lateral and internal views of cardinal process, PUM 01002; × 6.