UPPER ORDOVICIAN BRACHIOPODS FROM KAZAKHSTAN 



69 



Description. Shell smooth, dorsibiconvex, subpentagonal in out- 

 line, about 70% as thick as long and 95% as long as wide. Anterior 

 commisure sulciplicate. Ventral valve gently convex in lateral profile 

 with maximum thickness about one-third valve length from the 

 small, slightly erect pointed beak posterior to the hinge line. Sulcus 

 about 60% as wide as the valve, originating in the umbonal area at 

 about 4-5 mm from the beak, strongly deepening anteriorly and 

 divided medianly by high angular costa originating near mid-valve. 

 Dorsal valve strongly and evenly convex with maximum thickness at 

 mid-valve with median fold originating slightly anterior to mid- 

 valve and bearing two strong angular ribs. 



Ventral interior with small teeth and deep, narrow spondylium on 

 the low median septum. Dorsal interior with narrow cruralium raised 

 anteriorly on a low median septum extending anteriorly not more 

 than 1 .5 mm in adults. Inner plates small, thickened, slightly curved 

 in cross-section. Brachial processes short. 



Measurements. (47 1/1 2375) conjoined valves, L=14.0,W=1 6.9, 

 T=6.3, Sw=8.9; (474/12375) conjoined valves, L=20.4, W=21.0, 

 T=11.2, Sw=8.7; (475/12375) conjoined valves, L=22.9, W=24.5, 

 T=10.2, Sw=12.8; (476/12375) conjoined valves, L=16.5, W=19.8, 

 T=6.5, Sw=11.2; (479/12375) conjoined valves, L=10.5, T=6.7, 

 Sw=6.7. 



Discussion. This species usually occurs in the upper Anderken 

 Formation together with Parastrophina iliana, but can be easily 

 distinguished in being half the size, in the smooth shell with a single 

 costa in the sulcus and two in the fold of mature specimens, and in the 

 sulciplicate anterior commissure. 



Parastrophina plena closely resembles Parastrophina uniplicata 

 Fu, 1982 from the Jinhe Formation (Caradoc) of northwest China in 

 its smooth shell, sulciplicate anterior commissure, and in the 

 characters of the dorsal fold and ventral sulcus. They may be 

 conspecific. 



Genus IL1STROPHINA Gen.nov. 



TYPE SPECIES. Uistrophina tesikensis sp.nov. 



Diagnosis. Shell smooth, ventribiconvex with well-developed 

 dorsal median fold and ventral sulcus; ventral interior with 

 spondylium sessile posteriorly, raised anteriorly on low median 

 septum; dorsal interior with cruralium supported by high median 

 septum; well defined alate plates and long brachial processes. 



DISCUSSION. Externally Uistrophina is most similar to Eostrophina 

 (Zhan & Rong 1995) but differs in having a narrow spondylium 

 sessile posteriorly, raised anteriorly on a low median septum and 

 well developed alate plates. It differs from Liostrophia in having 

 strongly raised cruralium supported by a median septum instead of a 

 sessile cruralium or separated outer plates; however, present know- 

 ledge of the interior of type species of the former remains inadequate. 

 Uistrophina resembles Parastrophina and Parastrophinella in the 

 interior morphology of both valves, but differs in having a smooth 

 shell and a sessile spondylium posteriorly. Jin and Copper (1997) 

 demonstrated that in Parastrophinella the cruralium is supported by 

 the median septum along its entire length, but, in contrast to 

 Uistrophina, the dorsal median septum in Parastrophinella is very 

 low and buried within secondary shell in the apical area. 



Uistrophina tesikensis sp. nov. 



PI. 12. figs 28-35; Figs 15, 17 



Etymology. After the type locality. 



HOLOTYPE. BC 56823, PI. 12, figs 32-35, conjoined valves, from 

 Sample 948, Tesik River. 



Material. 14 pairs of conjoined valves (including BC 56823-24) 

 and one dorsal valve, all from Sample 948, Tesik River. 



Description. Shell smooth, dorsibiconvex, subcircular in outline, 



Table 25 Measurements of ventral valves of Uistrophina tesikensis sp. nov.. Sample 948, Tesik river. 





L 



W 



T 



Ld 



Sw 



St 



LAV 



T/L 



LdAV 



Sw/W 



N 



9 



9 



9 



9 



9 



8 



9 



9 



9 



9 



X 



7.5 



8.2 



5.1 



7.5 



5.7 



3.9 



92.3% 



68.2% 



92.2% 



70.2% 



s 



1.01 



1.46 



0.82 



0.98 



0.96 



0.94 



4.7 



6.6 



4.9 



5.4 



MEM 



6.2 



6.4 



4.2 



6.2 



4.6 



2.4 



83.8% 



58.3% 



82.9% 



63.9% 



MAX 



9.8 



11.7 



6.8 



9.7 



7.8 



5 



97.5% 



79.4% 



97.5% 



80.7% 





PLATE 13 



Figs 1-29 Liostrophia pravula sp. nov., Akchoku Mountain, Kujandysai section. 1-15, Sample 8256; 1-5, BC 57550, conjoined valves, ventral, dorsal, 

 anterior, posterior and lateral views, x 2; 6-10, BC 57551, conjoined valves, dorsal, ventral, anterior, posterior and lateral views, x 2; 11-15, BC 57552, 

 conjoined valves, dorsal , ventral, lateral, posterior and anterior views, x 2. 16-29, Sample 2538; 16-20, BC 57553, holotype, conjoined valves, dorsal, 

 ventral, lateral, anterior and posterior views, x 2; 21-24, BC 57554, conjoined valves, ventral, dorsal, anterior and lateral views, x 2; 25-29, BC 57555, 

 conjoined valves, ventral, dorsal, posterior, lateral and anterior views, x 2. 



Figs 30-50 Parastrophina iliana sp.nov. 30-33, Sample 8217, Kujandysai section, BC 57556, conjoined valves, dorsal, anterior, lateral and ventral views, 

 x 2. 34-37, Sample 2538, Kujandysai section, CNIGR 4/12361, conjoined valves, lateral, dorsal, ventral and posterior views, x 2. 38-42, Sample 100, 

 Anderkenyn-Akchoku section, BC 57557, holotype, conjoined valves, dorsal, ventral, posterior, anterior and lateral views, x 2. 43-46, Sample 8256, 

 Kujandysai section, BC 57558, conjoined valves, dorsal, lateral, ventral and posterior views, x 2. 47-50, Sample 628, Kujandysai section, BC 57559, 

 conjoined valves, dorsal, lateral, ventral and anterior views, x 2. 



Figs 51-58 Parastrophina plena Sapelnikov & Rukavishnikova, 1975. 51-54, Sample 2538. Kujandysai section, BC 57562, conjoined valves, lateral, 

 dorsal, ventral and anterior views, x 2. 55-58, Sample 8214, Anderkenyn-Akchoku section, BC 57563, conjoined valves, anterior, lateral, ventral and 

 dorsal views, x 2. 



Figs 59-74 Plectosyntrophia unicostata sp. nov., Anderkenyn-Akchoku section. 59-62, 67-70, Sample 626; 59-62, BC 57568, conjoined valves, dorsal, 

 posterior, lateral, and ventral views, x 2; 67-70, BC 57570, conjoined valves, holotype, lateral, ventral, dorsal and posterior views, x 2. 63-66, 71-74, 

 Sample 100; 63-66, BC 57569, conjoined valves, lateral, anterior, dorsal and posterior views, x 2; 71-74, BC 57571, conjoined valves, lateral, dorsal 

 ventral and anterior views, x 2. 



Figs 75-77 Didymelasma cf. transversa Fu, Sample 2538. Kujandysai section. BC 57573, conjoined valves, dorsal, lateral and ventral views, x 2. 



