Rivista Italìana di Paleontologia e Stratigrafia NOTA BREVE - SHORT NOTE NE\T SYRINGOTHYRIDID GENUS (SPIRIFERINIDA, BRACHIOPODA) FROM THE EARLY PERMIAN OF INTERIOR OMAN LUCIA ANCIOLINI Receiced Decentber 15, 200A Key uords: Interior Oman, Brachìopoda, Spiriferinida, new genus, new spec:ies, Sakmarian. Riassunto. Nelie faune a brachiopodì del Permiano inferiore, si rinvengono spesso pochi, ma significativi esemplari apprrrentì rlh famiglia Svringothyrididae (Spiriferinida). Le successioni de1 Permiano inferiore dell:r zone ccntrale dcl Sultanato di Orlan, sì disrnuuono per la conservazione eccezìon:rle e l'estrcma abbondanza di queste iorm. che arrivano a costituirc fino al 90% dell'intera ;rssociazìone fossilifera. Tali ritror.ementi e la revisione di forme affinì hanno permesso di introdurre un nLÌovo gcnere, dcnominato Pachycyrtella con specic- ttpo P omanensls n. sp. -comprendente specie gondwanìane preceden- temente attribuite a Cyrtella, dalla quale si distinguono per l'interarea ventrale alta ecl oricntata da apsacììna a ortoclin:r e per l'umbone estremamente ispessìto e calloso. Abstract. Represent;rtives of the S,vringothvrididae (Spìriferini- da) ;rre a signifìcant colnponcnr of the E:rì; Permi.rn brrchiopod fau- nils! even ìf usuallY subordinate in number of specimcns, except for the lnterior of Oman, x.here thcl' dominate tlre faunal assemblage. A ncw qenu. lh.hltlrtellL - n irlr 11 pc-.pecie, P omnnrnris n. sp. - is here established:in order to include sondawanan specres - pre- viously ;rssigned to thc gcnts Cyrte/la - char:rcterized by high and apsacline to orthocljne ventral jnterarea, thick umbo and deep dorsal median furrow. Introduction. During recent investigations on rhe mid-upper Sakmarian (Early Permian) brachiopod fauna from the Saiwan Formation (Haushi-Huqf area, Interior of Oman) - coupled with the revision of coeval faunas from the Perigondwanan fringe (Central Aghanistan, Indian Himalaya, Kashmir) - it became .rppàrenr that it was necessary to establish a new syringothyridid genus based on the specimens previously determined as ?Cyrtella aff . C. nagmargensls (Bion, 1928) by Angiolini in Angiolini er al. (.1997). The neu' genus is here named Pachycyrtella n. gen. bec,ruse of its thick, heavy umbo and its cyrtel- loid shape. dccePted February 1 t, 2AAl Pacbycyrtella omanensis n. gen. n. sp. has been col- lected chiefly from a 4O-cm thick bed of hybrid arenites at the base of the Saiwan Formation at Saiwan (level OL14 in fig. 2 of Angiolini et a1., 1997), where it has been recorded in life-position, dominating the faunal assemblage. Pachycyrtella omdnensis n. gen. n. sp. displays the feature. of a typicrl opportunist species in a pioneer palaeocommunity: random distribution pattern over a limited area, clustering in groups, numerical dominance (> 85%), suspension feeding, rapid rates of reproduc- tion and grosrth (r-strate gy), early maturity, low mortal- ity of juveniles and mortality rates in the adults which are independent from the densitl' and from the size of the individuals. The mid-Sakmarian transgression above the glacial to alluvial deposits of the ?Upper Carboniferous-Lower Permian Al-Khlata Formation provides a new habitat, a cool and inorganic nutrient-rich environment, which is colonised by the opportunist Pachycyrtella omdnensis n. gen. n. sp. showing several morphological adaptations enabling its successful exploitation. In contrast with the apparent bipolar Cyrtella, the new genus was probably confined to the regions located at the Perigondr.anan fringe during the Early Permian, such as Oman, Central Afghanistan and the Himalaya. T, *,,. L-,.^ ^^^,,---f, :rlso in e:Ìstern Ausrruli.r. Systematic Paleontology. Figure d and described specimens are housed in the collections of the Museum of the Dipartimento di Scien- ze della Terra, IJniversità degli Studi of Milan, Italy (MPUM numbers) and in the Musée de Géologie of Lausanne (MGL numbers). Apriìe 2001 Dìpartinento di Scìenze della Terra, \ria Mangiagalli 3.1, 20133 Milano, Ital1., lucia(q,eJ5.gp.terra.uninri.it 126 Order Spiriferinìda Ivanova, 1.97 2 Suborder Spiriferinidina Ivanova, 1.972 Superfamily Syringothyridoidea Fredericks, 1926 Family Syringothl.rididae Fredericks, 1926 Subfamily Permasyrinxinae Vaterhouse, 1986 Remarks - In their preliminary classification of the spiriferid brachiopods for the revised Treatise, Carter et al. (199a) included in the family Syringothyrididae Fred- ericks, 1926 all the punctate, strophic, biconvex sprr- iferids with ornamentation of simple ribs, smooth fold and sulcus, and high to very high ventral interarea with perideltidial areas. Based on the presence or the absence of the syrinx and the ventral median septum, they dis- tinguished three subfamilies within the Syringothyridi- dae. Due to the supposed occurrence of a syrinx they included Subansiria Sahni & Srivastava, 1956 in the sub- lamily Syringothyridinae. However as suggested by Angioiini et aI. (tlvl) Subansiria lacks a true syrinx and thus must be included ir-r the subfamil,v Permasyrinxinae \íaterhouse, 1986 together with CyrtelÌa Fredericks, 1924 and Punctocyrtella Plodowski, 1968, previously considered synonyms by Carter et al. (1994) . As discussed in Angiolini et aL. (1997), Cyrtella and Punctocyrtella could be regarded as distinct and sep- arate genera and a new genus Pachycyrtella is established in order to includ perigondawanan species previously placed rn Cyrtella and characterized by a high and apsacline ventral interarea and thick umbo. Genus Pachycyrtella n. gen. Type species: P omanensìs n. sp. Etymology. Gcnus named for its thick, heavy umbo (from the ancient greek no,Xug) and rs Cyrtella like general shape. Diagnosis. Thick shelled, large species s'ith high :ps.rcìine to orthocline ventraÌ jnterarea. Ventral sulcus usually wide and shallor., dorsal fastigium deep11. furrowed. Ornamentation of coarse, adichoto- mous costae. Interior of ventral vaÌve q,ith variablv developed umbonal callus, thick delthyrial plate, lone dental platcs with ventral adminicu- la surrounding the posterior part o{ thc muscìe frcld. Interior of dor- sal valve with broad sessile cardinal process; socket plates and crural b;rses fused to the cardinal proccss bv a thrck callus. Discussion. The new genus Pacbycyrtella is erected in order to include species similar to Cyrtella but charac- terized by a high rnd apsacline to orthocline ventral interarea, by r thick umbonal callus, and deep dorsal median furrow. In fact, Cyrtella differs from Pachycyrtel- la by its catacline ventral interarea, smaller callus, more transverse shape and shallower furrow on the dorsal fold. Furthermore, Cyrtella has a characteristic internal sec- rion with narrow post-delthyrial lcentral r cavity rnd much wider umbonal chambers, very different frorn that of Pachycyrtella, characterised by a large central chamber. Pacbycyrtella n. gen. differs from Permasyrinx \íaterhouse, 1983 by its apsacline-orthocline interarea and the occurrence of a medial sulcus along the fold; from Pyramidtbyris Hu, 1983, Pseudosyringotbyris Fred- ericks, 1916 and Tuotalania Hu, 1983 by the orientltion of the ventral inte rarea and the dorsal fastigium which in the latter genera is not sulcate. The specimens determined as S. nagmdlgensis lry Termier et aI. (t0l+) from the Sakmarian of Central Afghanistan are assigned to rhe new gents Pachycyrtel- /a because of their apsacline interareas and thick umbones. The same holds true for those determined as Cyrtella nagmargensis by Archbold & Gaetani (1991) from the Late Sakmarian Chumik Formation Member A of Zanskar (India). Cyrtella subparallela \flaterhouse 1982 from the Early Sakmarian Elvinia Fm. of SE Bowen Basin (E Australia) is probably related to Pachy- cyrtella, having an apsacline ventral interarea and a heavl unrbonal thickening. On the contrary, examination of replicas of the type material of Cyrtella nagmargensis (Bion, 1928) from Kashmir - kindly shown to me by Dr. G. Plodowski of Senckenberg Museum (Frankfurt) - has pointed out that L. Angiolint PLATE 1 ' All x l. c\Lepr s hcn 'pecified r Fig. 1 - Pachycyrte lla omanenis n. gen. n. sp. Holotype, dorsal view of complete specimen MPUM 8125. Fig. 2 - Pachycyrtella omanenis n. gen. n. sp. Holotl'pe, ventral view of complcte specimen MPUM 8425. Fig. 3 - Pachycyrtella omattenis n. qen. n. sp. Par:type, lateral view of completc specimen MPUM 8426. F'ig. a - Pachycyrtella omanenis n. gen. n. sp. Paratype, ventral view of cornplete specimen MPUM 8426, bearing a ce mented spccimen oi Ether- ilosia sp. Fig. 5 - Pachycyrtella etmanenis n. gen. n. sp. Paratype , ventral vien- of complete specimen MPUM 8428, bearing a cemented specimen ol Etber- ilosia sp. Fig. 6 - Pacbycyrtella omanenis n. sen. n. sp. P:r:r1-pc, dorsal r-ien of a complete specimen MPUM 8129. Fig. / - Pacbycyrtel/a omanenis n. gen. n. sp. Paratype, r.entral valr-e interior, specimen MPUM 8131. Fig. 8 - Pachyq,rteÌla omanettis n. gen. n. sp. Paratvpe, dorsal view of complete specimen of a jur-enile MPUM 8427. Fig. 9 - Pachycyrtella omanetris n. gen. n. sp. Par.rtl-pe, dorsal valve interior, specimen MPUM/9/5 Fig. 10 - Pachycyrtella omanenìs n. sen. n. sp. Secondary layer showing fìne punct:rtìon, x 52, at a.77 cn from the umbo (MGL 63121). Fig. 11 - Pdcbycyrtella omanenis n. lien. n. sp. Section shorving dental plates and delth.rirl pl.rte x,l rr 1.29 cm from the umbo (MGL 63121). Pl. 1 Nerr' brachíopod from E,trh, I)ertttian of Onan t27 t28 L. Angiolint the original species nagmargensis belong to rhe genus Cyrtella. In fact, the Kashmir specimens are charac- terised by a catacline interarea, transverse shape and internal characters consistent with those ol Cyrtella leulibiana (Fredericks, 1916), type species ol Cyrtella. Furthermore, Cyrte/la nagmargensis from Kashmir is easily distinguishable from the genus Punctocyrtella by the orientation and height of its ventral interarea, the ornamentation and the internal characters of the ventral valve. The Tibetan C. nagmargensls from the Late Sak- marian Qudi Formation of Rutog Duoma (Hu, 1983) belongs to the genus Cyrtella, based on the orientation of the interarea and the internal sections. The \X/estern australian C. awstralis Thomas, 1971 from the Lyons Group and Callytharra Formation is to be retained in the genus Cyrtella, according to the ori- entation of the interarea. C. koopi Archbold, 1990 from the Sakmarian Cuncudgerie Sandstone (Cunning Basin) is difficult to judge being an internal mould. Occurrence. Early Permian of South Oman, Cen- tral Afghanistan, Zanskar (India), ? E, Australia. Pachycyrtella omanensis n. sp. 1959 Asyrinx haushiensis Hudson & Sudbury, p. 16-17, pl. 5, fig. 2. 1959 Pseudosyrinx sp. - Hudson tr Sudbur,v, p.46, pl.5, fig. 1a-b. 1997 Cyrtella aff. C. nagmargezsls - Angiolini et al., p. 391, fig. 11.1- 6, text fig.8,9,11, tab.5. Holotype .A complete specimen: MPUM 8425. Paratypes. 6 complete specimens: MPUtrl 8426, MPUM 8427, MPUM 8,+28, MPUM8429, MPUM 8,+30, MPUM 2960. 2 ventral valves: MPUM 8431, MGL6Z121. 1 dorsal valve: MPUM /925. Etymology. Species named for its provenance, the Sultanate of Oman. Type locality and age. Saiwan (coord. 2A"52'27"N- 57"36'26"F.),Interior of Oman, basal bed (OL1a) of the Saiwan For- mation, mid-Sakmarian. Description. Medium to large-sized biconvex shells with maximum width at hinge line. Cardinal extremities from angular in .juveniles to truncared in adults. Shell substance finely punctate and micropunctate. Ventral valve weakly convex, sub-rhomboidal in outline. Interarea high, generally slightly concave, ori- ented at a low angle with the commissural plane (from apsacline to nearly orthocline); perdideltidial areas not well demarcated. Delthyrium closed by stegidial plates; hypodeltidial and deltidiai furrows separated by a del- tidial ridge. Shallow and smooth ventral sulcus arising at umbo, widening anteriorly and protruding anteriorly as a tongue of variable length. Ornamentation of simple rounded costae, numbering fi-12 for each flank. Costae widening anteriorly up to 3-,1.5 mm in width at the ante- rior margin. Growth lrrmellae of two differenr sizes occur throughout the valve: coarser and widely spaced versus finer, more numerous and denser. Micrornamen- tation of minute pustules. Dorsal valve tr.lnsverse, strongly arched. Fastigium widening and getting higher anteriorly, bear- ing a deep and wide median furrow, becoming shallower at the anterior margin. Lateral dorsal margins strongly overlapping the ventral ones. Ornamentation of 10-12 simple rounded costae on each side of the fold. Costae widening anteriorly up to 3-3.8 mm at the anterior mar- gin. Growth lamellae as in the ventral valve. Ventral valve interior with large and concave delthyrial plare, showing a strongly conc.rve margin towards the hinge line. Umbonal callus variably devel- oped, embedding dental plates and adminicula and filling at vcriable degree the central cavity below delthyrial plate and the lateral cavities; anterior sides of apical cal- lus deeply pitted by genital markings. Dental plates high, merging with adminicula and concave towards iateral margins. Adminicula surrounding the posterior part of the muscle field. Teeth stout and coarse. Muscle field large, sub-rhomboidal, slightly depressed, dendritic on posterior part and longitudinally striated on anterlor part and divided by a myophragm. Dorsal valve interior with a broad, sessil laminated cardinal process; socket plates and crural plates fused to the cardinal process by a callus which is very large in mature specimens. Spiralia broad, tightly coiled, with postero-larerally directed apex. Adductor scars depressed with a thin median myophragm. Discussion. This description is in total agreement with that of ?C. aff. nagmargensis published by Angioli- ni in Angiolini et al. (1997, p.391-392) to which the reader is referred for details on the ontogentetic varia- tion, intraspecific variabilitir, and serial sections. The invalidity of the genus Asyrinx Hudson 6c Sudbury. lq59 - based on rwo non congeneric specimens - has a1read1. been pointed out by Angiolini in Angiolini et aL (1997\. Ackno.oledgements. M. Balìni, E. Garzanti, A. Nicore, J.P Platel, J. Roger and A. Tintori are thanked for joint field-lvork. J. Carter rnd G. Plodowski are thankcd for revìsion and encouragement. Reseerch financialll' supported rjthin the Peri-Tethys Pro- gremme and bv Italian CNR (Grant to M. Gaetanì). Nero bracbiopod from Early Permian of Oman REFERENCES 129 Angiolini L., Bucher H.. Pillevuit A.. Platei J.P., Roger J., Broutin J., Baud A., Marcoux J., & Al Hashmi H. (1997) - Early Permian (Sakmarian) brachiopods from Southeastern Oman. Geobios, 3A: 379-405, Lyon' Archbold N.\( & Gaetani M. (1993) - Early Permian Bra- chiopoda and Mollusca from the N\7 Himalaya, India. Riv. It. Paleont. Strat.,99 27-56,Milano. CarterJ.,JohnsonJ.G., Gourvennec R. & Hong-Fei H. (199a) - A revised classification of the Spiriferid brachiopods. Annals of Carnegie Mwsewm, 63:327-374, Pittsburgh. Hu C. (1933) - New genera and species of Spiriferacean bra- chiopods in the Late Carboniferous to Early Permian from Duoma District, Rutog, Xizang (Tibet), China. Journal of Wuhan College of Geology,l'9: 105-117, tVuhan. Hudson R.G.S. & Sudbury M. (1959) - Permian Brachiopoda from south-east Arabia. 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