WESTERN AUSTRALIAN PERMIAN BRACHIOPODS 
II 
Trigonotreta neoaustralis Archbold & Thomas, 
1986 
Fig. 6A-I 
Neospiriferid.—Dickins 1976: 100. 
Trigonotreta neoaustralis Archbold & Thomas 
1986: 152, figs 16A-J, 17A-L (with synonymy). 
Material CPC 28047-28049, a natural cast of an 
immature conjoined shell and two incomplete casts of 
juvenile dorsal valves from locality T127; and CPC 
28050, a ventral valve internal mould from locality 
TK5A. 
Comments. The distinctive transverse shell out¬ 
lines, nature and bundling of the costae and 
prominent growth lamellae permit ready assign¬ 
ment of the specimens to Trigonotreta neoaus¬ 
tralis, a species from the Sterlitamakian Fossil 
Cliff Member and the Callytharra Formation, 
and the Aktastinian Jimba Jimba Calcarenite. 
The specimens from locality T127 are juvenile 
and immature representatives of the species and 
hence exhibit the transverse shell outline charac¬ 
teristic of these ontogenetic stages (Archbold & 
Thomas 1986). The ventral valve internal 
mould represents a sub-mature specimen and 
possesses the characteristic bulbous apical callo¬ 
sity of the genus. 
Fig. 6. A-I, Trigonotreta neoaustralis Archbold & Thomas. A-C, CPC 28047, natural cast of shell in dorsal, 
posterior and dorsal views, x 1.8, x 1.6, x 1. D, E, CPC 28048, natural cast of dorsal valve, x 2 and x 1. F, G, CPC 
28049, natural cast of dorsal valve, x 2 and x 1. H, I, CPC 28050, internal mould of ventral valve and latex cast of 
mould, x 1.8. 
