Proceedings of the Royal Society of Victoria 102(2): 121-122, 1990:11:30 
SHORT COMMUNICATION 
RE-ASSESSMENT OF THE ARABIAN PERMIAN CHONETID BRACHIOPOD 
CHONETES AR.4BICUS HUDSON & SUDBURY 
CHONETESARABICUS is a remarkable tiny species 
ofachonetidbrachiopod originally described from the 
Early Permian Lusaba Limestone of the Haushi Area 
(Sultanate of Oman) by Hudson & Sudbury (1959). 
The small size of the species raises questions as to its 
correct generic placement, despite the assignment of 
the species by Archbold (1983: 68) to Neochonetes 
(Sommeriella), a subgencric group noted for its larger 
species size (Archbold 1981). 
The new material described herein permits us to 
confirm the generic position of the species and to 
assess several critical morphological characters. 
In 1984 one of us (C.F.B.) collected a large suite of 
topotypic specimens from the Lusaba Limestone. The 
limestone is interpreted as being a shallow marine 
deposit from an open subtidal environment with fairly 
high energy conditions, consistent with the earlier 
views of Hudson & Sudbury (1959). 
The age of the Lusaba Limestone was considered by 
Hudson & Sudbury (1959) to be comparable with that 
of the Fossil Cliff Formation of Western Australia (a 
unit usually considered to be of Sterlitamakian age; 
Archbold 1982), but, as the Lusaba Limestone occurs 
stratigraphically above the occurrence of the Late 
Sakmarian (Sterlitamakian) ammonoid Metalego- 
ceras , the formation may be earliest Artinskian (Aktas- 
tinian) as suggested by Waterhouse (1976: 84). 
MORPHOLOGY OF THE SPECIES 
The species was well described by Hudson & Sudbury 
(1959), although some doubt has existed as to whether 
their material represented a mature species. We illus¬ 
trate three specimens (Fig. 1A-C), coated with 
ammonium chloride, to provide details not clearly 
visible in the original figures of uncoated specimens 
Specimen No. 
Width 
Hinge 
width 
Ventral 
height 
Dorsal 
height 
UTGD 98800 
9.8 
8.8 
_ 
7.0 
UTGD 98799 
7.2 
6.8 
5.5 
— 
UTGD 98798 
6.8 
5.8 
— 
4.5 
Table 1. Measurements of figured specimens (in 
mm). 
(Hudson & Sudbury 1959, pi. 3, figs 6-16, pi. 6, figs 
14-18). 
Measurements of the three figured specimens are 
provided in Table 1. Specimens are held in the Depart¬ 
ment of Geology, University of Tasmania. Pertinent 
morphological features include the distinct brachial 
ridges of the largest dorsal valve (UTGD 98800), indi¬ 
cating the maturity of the specimen, and the nature of 
the ventral internal rows of papillae and the dorsal 
external ornament (UTGD 98799 and 98798 respec¬ 
tively). The coarse denticulation of the ventral hinge 
reported by Hudson & Sudbury (1959) is regarded by 
us as due to post mortem abrasion of isolated valves. 
The feature is variably developed, often irregular, and 
a similar appearance can occur at the rear margin of 
the ventral interarea. 
We conclude that the species belongs in Neochonetes 
(Sommeriella) and that the larger representatives of 
the species are mature specimens rather than 
juveniles. 
ACKNOWLEDGEMENTS 
We are grateful to Mrs Isabel Munro for typing the 
manuscript. Our work is supported by funding from 
Fig. 1. A-C, Neochonetes (Sommeriella) arabicus (Hudson & Sudbury). A, UTGD 98800, dorsal valve internal 
view, X 5. B, UTGD 98799, ventral valve internal view, X 5.5. C, UTGD 98798, dorsal valve external view, 
X 5.5. 
121 
