Jurassic Brachiopods of Saudi Arabia

Abstract

No studies in depth have been made of the brachiopods from the Jurassic deposits of Saudi Arabia. This first study of the brachiopods from this important region is based mainly on a collection presented to the Smithsonian Institution by the Arabian-American Oil Company (Aramco). In addition, the study includes collections made by Drs. P.M. Kier and E.G. Kauffman of the Smithsonian Institution and R.W. Powers, C.D. Redmond and H.A. MacClure of the Arabian-American Oil Company. Sixty-one genera are described of which 29 are new. Of these 13 rhynchonellid genera are new: <i>Amydroptychus, Baeorhynchia, Colpotoria, Conarosia, Deltarynchia, Echyrosia, Eurysites, Heteromychus, Lirellarina, Nastosia, Pycnoria, Schizoria</i>, and <i>Strongyloria</i>. Other described genera are: <i>Burmirhynchia</i> Buckman, 1917, <i>Cymatorhynchia</i> Buckman, 1917, <i>Daghanirhynchia</i> Muir-Wood, 1935, <i>Gibbirhynchia</i> Buckman, 1917, <i>Globirhynchia</i> Buckman, 1917, <i>Kallirhynchia</i> Buckman, 1917, <i>Kutchirhynchia</i> Buckman, 1917, <i>Somalirhynchia</i> Weir, 1925, <i>Sphenorhynchia</i> Buckman, 1917, and <i>Torquirhynchia</i> Childs, 1969. Of Spiriferinacea, one genus, <i>Calyptoria</i>, is new and two genera are described: <i>Liospiriferina</i> Rouselle, 1977, and <i>Spiriferina</i> d'Orbigny, 1847. The Terebratulacea are represented by 11 new genera: <i>Arabatia, Arabicella, Arapsopleurum, Arapsothyris, Dissoria, Ectyphoria, Pionopleurum, Pleuraloma, Stenorina, Tanyothyris</i>, and <i>Toxonelasma</i>. Seventeen described terebratulaceans are <i>Apatecosia</i> Cooper, 1983, <i>Avonothyris</i>? Buckman, 1917, <i>Bihenithyris</i> Muir-Wood, 1935, <i>Dolichobrochus</i> Cooper, 1983, <i>Dorsoplicathyris</i>? Almeras, 1971, <i>Glyphisaria</i>? Cooper, 1983, <i>Gyrosina</i>? Cooper, 1983, <i>Habrobrochus</i> Cooper, 1983, <i>Kutchithyris</i>? Buckman, 1917, <i>Loboidothyris</i>? Buckman, 1917, <i>Orthotoma</i> Quenstedt, 1869, <i>Plectothyris</i>? Buckman, 1917, <i>Pseudowattonithyris</i>? Almeras, 1971, <i>Somalithyris</i> Muir-Wood, 1935; <i>Sphaeroidothyris</i> Buckman, 1917, <i>Stiphrothyris</i>? Buckman, 1917, and <i>Striithyris</i> Muir-Wood, 1935. The Zeilleriacea include four new genera: <i>Apothyris, Mycerosia, Sphriganaria</i> and <i>Xenorina. Described zeilleriids are Flabellothyris</i> Eudes-Deslongchamps, 1884, <i>Rugitela</i> Muir-Wood, 1936, and <i>Zeilleria</i> Bayle, 1878. A total of 166 species are described and 25 lots are identifiable as species. <i>Pseudoglossothyris</i>? <i>sulcata</i> Muir-Wood, 1935, from Somaliland (Somali Republic) is shown to be a zeilleriid, and the species is herein transferred to <i>Aulacothyris. Eudesia cardioides</i> Douvillé, 1916, is herein transferred to the new genus <i>Sphriganaria</i>. The Liassic Marrat Formation abounds in spiriferinids. The Dhruma Formation (Bajocian to Callovian) is rich in rhynchonellids which dwindle in numbers in late Dhruma beds. The overlying Tuwaiq Mountain and Hanifa formations (Callovian to Kimmeridgian) are conspicuous for the large numbers of terebratulaceans which far outnumber the rhynchonellids. Correlation with Jurassic sequences near and far is difficult because of the high degree of endemism shown by the Saudi Arabian brachiopods. Precise correlation with British and European faunas is not now possible. Relationships with the Jurassic faunas of the Sinai, Israel and East Africa in the Callovian is suggested by the presence of two species in common and generic representation shown by <i>Daghanirhynchia, Somalirhynchia, Bihenithyris, Somalithyris</i>, and <i>Striithyris</i>.