CARADOC BRACHIOPODS FROM THE SHAN STATES 



Superfamily STROPHOMENOIDEA King, 1846 



Family STROPHOMENIDAE King, 1846 



Subfamily FURCITELLINAE Williams, in Williams et al., 1965 



Genus BELLIMURINA (BELLIMURINA) Cooper, 1956 



125 



chilidium, and from Kjerulfina in its lack of ventral geniculation and 

 rugae. Megamyonia has distinctive ventral trans-muscle septa and 

 other very different characters. Odoratus has ventral geniculation 

 and lacks ventral muscle bounding ridges. Rhipidomena is resupi- 

 nate and has dorsal trans-muscle ridges. 



Bellimurina (Bellimurina)? sp. 



PL 4, fig. 8 



Discussion. One ventral valve (internal and external moulds, 

 BB37585 ) from the equivalents of the Upper Naungkangyi Group at 

 Linwe, Southern Shan States, has some characters typical of 

 Bellimurina (Bellimurina), such as a convex ventral valve with 

 dorsal geniculation, a surface covered by zigzag rugae, and short and 

 divergent dental plates (Cooper 1956: 854); but lack of material, 

 especially dorsal valves, still makes our identification uncertain. 

 Bellimurina rudis Xu, Rong & Liu (1974: 153, pi. 66, figs 14-16), 

 from the Shihtzupu Formation (early Caradoc) of northern Guizhou, 

 South China, is larger in shell size, has much stronger zigzag rugae 

 and more impressed ventral muscle field with distinctive surround- 

 ing ridges. It is therefore not conspecific with this Burmese specimen. 



Family RAFINESQUINIDAE Schuchert, 1893 

 Subfamily RAFINESQUININAE Schuchert, 1893 



Genus DIRAFINESQUINA gen. nov. 



TYPE SPECIES. Dirafinesquina globosa sp. nov. 



DIAGNOSIS. Family characteristics of Rafinesquinidae. Like 

 Rafinesquina but with ventral valve bounding ridges surrounding a 

 suboval muscle field; cardinal process lobes weaker and erect rather 

 than anteriorly directed and with socket ridges better developed. 



Description. As for Dirafinesquina globosa below. 



Discussion. The true Rafinesquina, from the Caradoc-Ashgill of 

 North America, has been revised and reillustrated by Rong & Cocks 

 (1994). Reed (1906, 1936) attributed various Burmese specimens to 

 species of Rafinesquina (see specific discussion below), but we 

 consider that all the specimens in our collections and some of Reed's 

 material from the Shan States may be grouped together within a 

 single species, erected below as Dirafinesquina globosa. 



The new genus can be firmly placed within the subfamily 

 Rafmesquininae and the family Rafinesquinidae by its cardinalia, 

 normal convexity and lack of rugae. There are ten other members of 

 the subfamily. Of those of comparable age, Rafinesquina itself 

 appears the closest, but with the differences mentioned in the 

 diagnosis above. Dirafinesquina differs from Colaptomena and 

 Hedstroemina in the large chilidium and pseudodeltidium and from 

 the former in the lack of dorsal median septum; and from the latter 

 in the lack of strong dental plates. It differs from Kjaerina in the 

 suboval rather than triangular ventral muscle field and larger 



Dirafinesquina globosa sp. nov. 



PI. 4, figs 9-11; PI. 5, figs 1-3, 5 



71936 Rafinesquina cf. alternata Conrad; Reed: 69, pi. 3, fig. 6. 

 1936 Rafinesquina cf. semiglobosina Davidson: Reed: 70, pi. 3, 

 fig. 7. 



HOLOTYPE. BB37593 (PI. 4, fig. 11), from the equivalents of the 

 Upper Naungkangyi Group at Linwe (Locality AM78), Southern 

 Shan States, longitude 96°33'E, latitude 21°14'N. 



MATERIAL AND LOCALITIES. 31 specimens: three dorsal internal 

 and two external, 20 ventral internal and six external moulds from 

 the equivalents of the Upper Naungkangyi Group at Linwe (Locality 

 AM78) and Loke-pyin (about 14 km southeast of Ye-ngan, Locality 

 AM 106), Southern Shan States. 



Description. Exterior. Large, subcircular shell more than 20mm 

 long and wide with length/width ratio about 1.0. Lateral profile 

 concavo-convex; dorsal valve evenly and gently concave; ventral 

 valve gently convex posteriorly, with variable but sometimes sharply 

 increasing convexity dorsally at about mid-length. Cardinal ex- 

 tremities round or rectangular, maximum width along the hinge line 

 or a little anterior to it. Large flat apsacline ventral interarea with an 

 arched pseudodeltidium, narrower anacline dorsal interarea with a 

 much larger and more arched chilidium. Ornament of multibranching 

 parvicostellae, 3-5 finer costellae between two coarser ones. No 

 growth lines observed. 



Ventral interior. Small rod-like or triangular teeth supported by 

 weak dental plates which extend forward as muscle bounding ridges. 

 Well-impressed, elongated oval muscle field 43-55% valve length 

 and 37-39% valve width; a pair of long, kidney-shaped adductor 

 scars slightly elevated and open anteriorly; diductor scars narrowing 

 anteriorly, but longer than the adductor scars. Saccate vascular 

 markings with a pair of vascular media originating from the anterior 

 ends of adductor scars. 



Dorsal interior. Relatively small cardinalia (Type B of Rong & 

 Cocks 1994) with a variably developed, sometimes ponderous, 

 cardinal process; triangular, sessile and discrete lobes including a 

 plate-like shaft and a swollen myophore, and project ventrally and 

 anteriorly; low, short, straight and variably thick socket ridges 

 separated from the cardinal process; notothyrial cavity elevated; 

 small shallow sockets open antero-laterally. Well-impressed circular 

 muscle field, particularly posteriorly; low and wide myophragm 

 starting from the notothyrial platform and narrowing anteriorly. No 

 vascular markings observed. 



Measurements. Most of our specimens are broken and so only 



PLATE 4 



Figs 1-7 Ishimia subdeltoidea (Reed). Tawmawgon. 1, BC 52420, ventral internal mould, x 1.5. 2, SMA 3124, latex cast of ventral exterior, x 1.5. 3a, 3b. 



SMA 3127, latex cast and internal mould of dorsal interior, x 1.5. 4, SMA 3126, dorsal internal mould, x 2. 5, SMA 3125, dorsal external mould, oblique 



view showing the dorsal geniculation, x 1.5. 6. BC 52191, dorsal internal mould showing small curved socket ridges, x 2. 7a-c, B 29664. latex cast and 



internal mould of a dorsal valve with another dorsal internal mould to the right, both with weaker platforms, x 1.5. 

 Fig. 8 Bellimurina {Bellimurina)! sp. BB 37585, Linwe, Locality AM78, latex cast of ventral exterior, x 4. 

 Figs 9-11 Dirafinesquina globosa gen. et sp. nov. Linwe, Locality AM78. 9a-c, BB 37607, lateral, posterior and ventral views of ventral internal mould, x 



1.5. 10, BB 37600, latex cast of dorsal interior showing the cardinalia and muscle field, x 5. 11a, lib. BB 37593, Holotype. latex cast and internal mould 



of dorsal interior, x 5. 



