AMMONITES AND NAUTILOIDS OF WADI HAJAR 



47 



Remarks. T. naifaensis is the most serpenticone and coarsely 

 ribbed species of Torquatisphinctes, being more evolute and having 

 fewer ribs than T. torquatus. The distinctive constrictions and seg- 

 mental growth are well seen 5-6 ribs before the aperture and the 

 coarse ribs are especially prominent on the inner whorls. Its Beckeri 

 Zone age is derived from its association with other ammonites in the 

 lower part of the Kilya Member. 



Occurrence. Lower marly part of the Kilya Member, Naifa Cliff 

 and Wadi Arus; Beckeri Zone, Upper Kimmeridgian. 



Gtms KATROLICERAS Spath, 1924a 

 Type species. Ammonites pottingeri J. de C. Sowerby, 1840. 



Katroliceras formosum Spath, 1931 



PI. 2, figs 3, 6; PI. 4, figs 1-3,5 



1 93 1 Torquatisphinctes tenuistriatus wzx.formosa Spath: 486, pi. 



95, figs 4a, 4b. 

 71931 Pachysphinctes bathyplocus (Waagen), var. sparsiplicata 



Spath: 495, pi. 78, figs 6a, 6b. 

 71959 Pachysphinctes bathyplocus (Waagen), var. sparsiplicata 



Spath; Collignon: pi. 1 18, fig. 447. 

 71959 Torquatisphinctes torquatus (Sowerby), var. belamboensis 



Collignon: pi. 118, fig. 448. 

 71959 Torquatisphinctes transitorius Collignon: pi. 120, fig. 453. 

 71959 Katroliceras sowerbyi Spath: Collignon; pi. 122, fig. 459. 

 71959 Katroliceras bassae Collignon: pi. 124, fig. 466. 

 71984 Katroliceras? cf. bathyplocus (Waagen); Verma & Wester- 



mann: 44, pi. 5, figs 2a, 2b. 



Material. 33 specimens, CAl 104-36. from the upper marly part 

 of the Kilya Member in Wadi Kilya. They include 9 microconchs, 9 

 macroconchs and 14 fragments or specimens too small to be identi- 

 fied as microconchs or macroconchs. 



Description. Microconchs. 6 adults have mouth-borders at 76, 

 71, 61, 51, 50 and 46 mm diameter, and body-chambers 0.7-0.8 

 whorls long. Microconchs become adult at a size before the distinc- 

 tive depressed whorls and widely spaced primary ribs oi Katroliceras 

 are developed. The primary ribs are modified, however, on the final 

 quarter whorl, becoming much more widely spaced, and all show 

 slight uncoiling of the umbilical seam and decrease of the whorl 

 breadth at the aperture. No lappets are preserved. 



Macroconchs. All 9 are incomplete, but two attain diameters of 98 

 and 96 mm, one being septate up to 95 mm diameter, indicating a 

 size of at least 130 mm diameter when complete. Whorls become 

 depressed and primary ribs widely spaced from about 70 mm 

 diameter. Macroconchs generally have slightly more massive whorls 

 than microconchs of the same size, though separation is generally 

 not possible below 40 mm diameter. 



In both dimorphs the whorls are evolute and the whorl section is 

 rounded-quadrilateral, varying between square and slightly de- 

 pressed, but becoming more depressed from 70 mm diameter in the 

 macroconch. Ribs on the inner whorls are straight, prorsiradiate or 

 slightly curved forwards, and relatively fine and dense; most bifur- 

 cate regularly at the ventro-lateral angle, but occasional ribs remain 

 single; from 50 mm diameter primary ribs become increasingly 

 widely spaced, some are triplicate or multiplicate, and there are 

 occasional intercalated secondary ribs; density of the ribs on the 

 venter shows considerable variation; about 3 shallow constrictions 

 per whorl are present on most specimens. 



Measurements 



D Wh Wb U 



CAl 106, macroconch 95.5 23.6(0.25) 28.6(0.30) 49.8(0.52) 



CAl 104, macroconch 94.5 27.2(0.29) 29.3(0.31) 49.0(0.52) 



CAl 105, macroconch 71.0 21.0(0.30) 24.2(0.34) 34.3(0.48) 



CA1108, microconch 72.0 19.8(0.28)22.8(0.32)36.0(0.50) 



CA1107. microconch 65.5 19.3(0.29)21.0(0.32)33.5(0.51) 



CAl 109, microconch 63.0 17.0(0.27) — 31.3(0.50) 



Remarks. Amongst the many examples of Katroliceras figured 

 by Waagen (1875), Futterer (1894), Spath ( 1931 ). Collignon (1959) 

 and Verma & Westermann (1984), only a few are close to this Yemeni 

 species, of which the distinctive features are the fine-ribbed, 

 prorsiradiate, inner whorls and the quadrate, slightly depressed 

 whorl section. The specimen from the Hybonotum Zone of Cutch 

 figured by Spath (1931: pi. 95, fig. 4) as Torquatisphinctes 

 tenuistriatus var. formosa is the closest match. The holotype of 

 Spath's variety is 73 mm diameter and does not show adult features 

 of either dimorph (the holotype of Torquatisphinctes tenuistriatus 

 Spath (1931: pi. 85, fig. 1) has much more finely ribbed inner 

 whorls). It is less certain that the holotype of Spath's ( 1 93 1 : pi. 78 

 fig. 6) variety Pachysphinctes bathyplocus var. sparsiplicata be- 

 longs to the same species because the inner whorls are less fmely 

 ribbed and distinctive and Katroliceras features are still not devel- 

 oped at 90 mm diameter. On the other hand, the four specimens from 

 bed 525 in the Hybonotum Zone at Belambo, Manera, Madagascar, 

 figured under four different names by Collignon (1959: figs 448, 

 453, 459, 466) are extremely similar to each other and to the Yemeni 

 species. Finally, it is likely that Verma & Westermann's ( 1 984: pi. 5, 

 fig. 2) fine adult microconch (with a small lateral lappet) from the 

 base of the Hybonotum Zone at Mombasa, Kenya, also belongs to 

 this species, the only difference being its slightly less finely ribbed 

 inner whorls. The multiplicity of specific names for Katroliceras 

 will only be sorted out when collections from single horizons allow 

 the amount of variation in a species to be discovered. Judging from 

 the present collection from a single horizon in Yemen, such variation 

 is only moderate, and is mainly in rib density, especially of the 

 secondary ribs on the venter. 



Complete microconchs are figured in PI. 4, figs 1, 5, which show 

 the rib modification at the aperture, though lappets are missing, 

 while the microconch of PI. 4, fig. 3 shows the fine-ribbed inner 

 whorls well. The macroconchs of PI. 2, fig. 3 and PI. 4. fig. 2 show 

 the broad depressed whorls and modified ribs that develop from 70 

 mm diameter, and PI. 2, fig. 6 is an immature macroconch. 



Occurrence. The upper marly part of Kilya Member, Naifa 

 Formation, Wadi Kilya; Hybonotum Zone, Lower Tithonian. 



Katroliceras pottingeri (J. de C. Sowerby, 1840) PI. 4, fig. 6 



1840 Ammonites pottingeri l.itC. Sowerby: 719, pi. 61, fig. 10. 

 1875 Perisphinctes pottingeri (Sowerby); Waagen: 183, pi. 51, 



fig. 1. 

 71875 Perisphinctes katrolensis V^aagen: 184, pi. 103. 

 1894 Perisphinctes pottingeri (Sowerby); Futterer: 7, pi. 1. figs 



1,2. 

 1931 Katroliceras pottingeri (J. de C. Sowerby); Spath: 505. pi. 



83, fig. 4; pi. 98, fig. 4; pi. 102. fig. 5. 

 1931 Katroliceras waageni Spath: 508 (nom. now for Waagen, 



1875: pi. 51, fig. 1). 

 7 1 P3 1 Katroliceras leren.se Spath; 5 1 1 , pi. 89, fig. 1 . 

 1959 Perisphinctes pottingeri (Sowerby); Collignon: pi. 121, 



figs 455, 456. 

 1959 Perisphinctes pottingeri (Sowerby), var. analavalonensis 



Collignon: pi. 121. fig. 457. 



