AMMONITES AND NAUTILOIDS OF WADI HAJAR 



Cecca ( 1 986), who recognized that the undulations on the venter are 

 a feature of microconchs, and they arranged most of the species 

 proposed or discussed by Zejszner (1846), Oppel (1865), Zittel 

 (1868, 1870) and Fontannes (1879) into dimorphic pairs. 



Haploceras staszycii (Zejszner, 1846) PI. 1, fig. 9 



1846 Ammonites staszycii Zejszner: pi. 4, figs 3a-3d. 



1 870 Haploceras staszycii (Zejszner); Zittel: 50, pi. 27, figs 2-6. 



1875 Haploceras staszycii (Zt']%znQr)\Vi\\ti &.¥mmenta\: 109, 



pi. 5, figs 10, 11.' 

 1 879 Haploceras staszycii (Zejszner); Fontannes: 1 1 , pi. 2, fig. 4. 

 1906 Haploceras sp. indet., Burckhardt: 90, pi. 24, figs 1-3. 

 1959 Haploceras elimatum (Oppel); Collignon: pi. 142, figs 536, 



537. 

 71959 Haploceras staszycii (Zejszner); Collignon: pi. 142. fig. 



539. 

 1961 Haploceras staszycii (Zejszner); Donze & Enay: 43. 



Material. Eight specimens, CA709-16, from the Breadloaf Con- 

 cretions in the Kilya Member, east side of Wadi Arus. 



Description. The collection consists of one adult microconch 

 with its complete mouth-border at 23.8 mm diameter; part of a 

 phragmocone of 24.5 mm diameter that is probably a microconch; 

 another microconch with a phragmocone 16.5 mm diameter fol- 

 lowed by half a whorl of incomplete body-chamber up to 25 mm 

 diameter; a fragment of the outer part of the body-chamber of a large 

 macroconch at 75-80 mm diameter; and four small specimens of 

 17-22 mm diameter. The whorls are involute and moderately thick, 

 with a small umbilicus, and a rounded whorl section in which the 

 whorl sides are gently convex, the umbilical walls rounded and 

 slightly undercut, and the venter is evenly arched. Flexuous radial 

 striae bend backwards at the middle of the whorl side, then become 

 stronger on the venter, especially on the adult body-chamber of the 

 microconch, where they form mid-ventral undulations. The adult 

 mouth-border of the microconch is immediately preceded by a slight 

 constricfion on the outer half of the whorl, then there is a collar-like 

 rostrum on the venter; a forwards projection in the mouth-border in 

 the middle of the whorl side follows the shape of the striae and forms 

 a small rudimentary 'lappet', but there is no long spatulate lappet as 

 in Glochiceras. 



Measurements 









D 



Wh 



Wb 



U 



CA709 21.7 



11.1 (0.51) 



7.5 (0.35) 



3.8(0.18) 



CA710 24.0 



13.5 (0.56) 



8.6 (0.36) 



3.5(0.15) 



Remarks. The two main species that occur abundantly in the 

 Becked and Hybonotum Zones are Haploceras staszycii (Zejszner) 

 and H. carachtheis (Zejszner). H. staszycii is based on a 60 mm 

 diameter original specimen (a macroconch) figured by Zejszner, 

 which is like the much smaller Yemeni specimens in having a small 

 umbilicus (U/D = 0.17) and gently rounded whorl sides. H. 

 carachtheis (Zejszner, 1846: pi. 4, fig. 1) differs in being less 

 involute (U/D = 0.26-0.30) and having flat whorl sides. In both 

 species the microconchs have ventral undulations on the final half 

 whorl of body-chamber. H. elimatum (Oppel; Zittel, 1868: 79. pi. 



41 



13, figs 1-7) occurs mainly higher in theTithonian, and has slightly 

 more evolute whorls, and a distinctive whorl section, in which the 

 greatest whorl breadth is near the umbilical edge and the gently 

 rounded whorl sides converge towards a narrowly rounded venter. 

 H. subelimatum Fontannes (1879: 12. pi. 2, figs 5, 6) is also 

 somewhat younger in age. and has rounded compressed and even 

 more evolute whorls. H. tithonius (Oppel: Zittel, 1868: 82, pi. 14, 

 figs 1-3) and H. leiosoma (Oppel; Zittel, 1868: 86. pi. 14. figs 5. 6) 

 are both very involute (U/D - ca.0.09). and have flat whorl sides and 

 a distinctive funnel-shaped umbilicus. Three specimens from the 

 Lower Tithonian of Madagascar figured by Collignon (1959: pi. 

 142. figs 536, 537, 539) appear to be examples of//, staszycii rather 

 than H. elimatiun for which they do not have the characteristic whorl 

 sides converging towards the venter. Many well-preserved 

 Haploceras from Mazapil, northern Mexico, were described by 

 Burckhardt (1906), mostly as new Mexican species, but one speci- 

 men identified as Haploceras sp. ind. (Burckhardt, 1906: 90, pi. 24, 

 figs I, 2) is closely similar, if not identical, to the Yemeni specimens. 

 The presence of Haploceras in the Breadloaf Concretions in the 

 lower part of the Kilya Member is important for confirming the 

 dating of the other ammonites in these concretions and also the more 

 abundant ammonites at Naifa Cliff that are slightly higher in the 

 succession. The oldest Haploceras are found in the uppermost part 

 of the Eudoxus Zone in south-western France and Germany, in 

 White Jura 54 (horizon 18 of the Crussol (Ardeche) section). H. 

 staszycii is recorded from that horizon and throughout the overlying 

 Beckeri Zone (White Jura el) according to the detailed records of 

 Holder & Ziegler (1959: 168, 181). Topmost Eudoxus Zone (and 

 more probably Beckeri Zone) is therefore the oldest age that can be 

 ascribed to the Perisphinctids and other ammonites that occur with 

 Haploceras in the Kilya Member in Wadi Hajar. 



Occurrence. The lower part of Kilya Member, Naifa Formation, 

 east side of Wadi Arus; Beckeri Zone, Upper Kimmeridgian. 



Haploceras umbilicatum sp. nov. PI. 1, fig. 11; Pi. 3, fig. 1 



HOLOTYPE. CA576 from bed 57 of the Mintaq Member. Mintaq 

 Salt Dome. 



Paratypes. CA577 from the same bed as the holotype, and 

 CA578 from bed 69 in the same section. 



Diagnosis. Has moderately compressed whorls and a larger um- 

 bilicus that other species ofHaploceras: in macroconchs the umbilical 

 width is 30-34% of the diameter at 100-135 mm diameter. The 

 whorl section is elliptical with no traces of umbilical or ventro- 

 lateral edges. Smooth except for sinuous growth striae or very 

 reduced ribs. 



Description. The holotype is the largest specimen. 136 mm 

 diameter at its (?adult) mouth border; it has a body-chamber that is 

 apparently more than 320° long, and parts of a poorly preserved, 

 recrystallized phragmocone. The larger paratype (CA577) is 118 

 mm diameter at its incomplete aperture and has a body-chamber 

 250° long following the recrystallized whorls of the phragmocone. 

 The smaller paratype (CA578) from bed 69 is a quaiter whorl 



PLATE 2 



Figs I, 2 Torquatisphinctes naifaensis sp. nov. L paratype, Breadloaf Concretion:,. Kilya Member (fauna 7). east cliff. Wadi Arus. SM F.I2168. xO-SS. 



2a, 2b, holotype, 0.5 m above base of middle limestone part of Kilya Member, Naifa Cliff, CA974. 

 Figs 3, 6 Katroliceras formosum Spath, upper marly part of Kilya Member (fauna 8). Wadi Kilya. 3a, 3b, CAl 104; 6a, 6b, CAl 10.5. wholly septate. 

 Fig. 4 Sutneria weidmanni Zeiss, Breadloaf Concretions, Kilya Member (fauna 7), east cliff. Wadi Arus. 4a-4d, SM F. 1 2 1 6.1; 4a, 4b, x 1 ; 4c, 4d, x2. 

 Fig. 5 Subdichotomoceras ?latissimum (Zwierzycki), upper marly part of Kilya Member (fauna 8). Wadi Kilya. 5a. 5b, CAl 145. 



