AMMONITES AND NAUTILOIDS OF WADI HAJAR 



85 



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Fig. 4 Cmssoliceras cf. wegetei Enay, approximately 8 m below top of 

 Billum Member (fauna 5), 0.5 km NE of river crossing at Al Ma'abir; 

 CA1263, xO.48 (from a colour photograph taken in the field). 



1959 Badenia wegelei Enay: 230 {nom. nov. forWegele, 1929: pi. 



5, fig. 4, non Perisphinctes acerrimus Siemiradzki, 1891). 

 1961 KatroUceras (Crussoliceras) tenuicostatum Geyer: 44, pi. 



4, figs 3, 5; pi. 5, fig. 3. 



Material. CA1263 from approximately 8 m below the top of the 

 Billum Member, 0.5 km NE of the river crossing at Al Ma'abir. 



Description. This ammonite is on the top surface of a block of 

 fine-grained grey limestone, weathering brown on the outside. It 

 consists of most of a highly evolute outer whorl of 210 mm maxi- 

 mum diameter. The whorl thickness cannot be seen, and removal of 

 part of the very splintery limestone shows that the hurried side is not 

 preserved. Widely spaced primary ribs, which tend to curve back- 

 wards at their ventral ends on the final third of a whorl, are separated 

 by wide smooth interspaces. The ribs bifurcate or trifurcate at the 

 ventro-lateral edge, and one rib near the beginning of the whorl gives 

 rise to four secondary ribs. There is a constriction half a whorl before 

 the aperture. The inner whorls are not exposed and are not thought to 

 be preserved in the matrix. It is an incomplete macroconch. 



Remarks. This species is characterized by widely spaced prima- 

 ries that divide into 2 or 3 secondaries at the ventro-lateral edge. One 

 of the specimens figured by Wegele (1929: pi. 6, fig. 1 ) appears to be 

 an almost complete microconch, while the other specimens of 

 Wegele and Geyer are probably macroconchs, like the Yemen speci- 

 men. Geyer (1961: 44) gave a new specific name to his specimen 

 from White Jura y3 in the Swabian Alb of SW Germany, rather than 

 using Enay's (1959: 230) earlier new name for Wegele's specimen 

 from the Franconian Alb. C. wegelei is more evolute, more 



serpenticone and has less massive whorls than C. crussolien.se 

 (Fontannes; lectotype refigured by Geyer, 1961 : pi. 5, fig. 4), though 

 differences between the two are not large, and intermediates may yet 

 be found. C. divisum (Quenstedt, 1888: pi. 106, fig. 1; Geyer, 1961: 

 44, pi. 3, fig. 5; pi. 5, fig. 1) is more distinct in having more widely 

 spaced ribs from a much earlier growth stage. 



Occurrence. Upper part of the Billum Member, Naifa Forma- 

 tion, Al Ma'abir; Divisum Zone, Lower Kimmeridgian. 



Subfamily LITHACOCERATINAE Zeiss, 1968 

 Genus LITHACOCERAS Hyatt, 1900 



Type SPECIES. Ammonites idmensis Oppc\, 1858. 



Subgenus LITHACOCERAS Hyatt, 1900 



Remarks. Lithacoceras ulmense occurs in the upper half of the 

 Beckeri Zone and the bottom of the Hybonotum Zone on the 

 Kimmeridgian - Tithonian boundary in White Jura ^ in southern 

 Germany (Ziegler, 1977: 23). This is the date of this type species of 

 Lithacoceras s.s., and many of the other species from the Upper 

 Oxfordian and throughout the Kimmeridgian that have been referred 

 to Lithacoceras in the past are now usually placed in other genera 

 (Zeiss, 1968:49;Atrops, 1982: 121;Atrops&Melendez, 1993:20). 

 The lectotype of L. (L.) ulmense is a macroconch, and Lithacoceras 

 s.s. is used as a subgenus for macroconchs that accompany some of 

 the microconchs of Lithacoceras (Subplanites). 



Lithacoceras (Lithacoceras) cf. ulmense (Oppel, 1858) 



PI. 19, fig. 6 



1858 Ammonites ulmensis Oppel: 771. 



1863 Ammonites ulmense Oppel; Oppel: 261. pi. 74, fig. 1 (non 



figs 2-4). 

 1914 Virgatosphinctes (Perisphinctes) ulmensis (Oppel); Schneid: 



159, pi. 4, fig. 3. 



1956 Lithacoceras ulmense (Oppel); Arkell: 784, pi. 43, fig. 6 

 (copy of Schneid, 1914: pi. 4, fig. 3). 



1957 Lithacoceras ulmense (Oppel); Arkell: L323, fig. 413-3 

 (copy of Schneid, 1914: pi. 4, fig. 3). 



1 959 Perisphinctes (Lithacoceras) ulmensis (Oppel ); Berckhemer 

 & Holder: 52, pi. 10, fig. 50. 



1961 Lithacoceras ulmense (Oppel); Holder: 1 13, pi. 5 (photo- 

 graph of the lectotype). 



1977 Lithacoceras ulmense (Oppel); Ziegler: 23, pi. 7, fig. 2. 



Material. Two specimens: SM F. 12202 from the base of the 

 middle limestone part of the Kilya Member in Naifa Cliff; and 

 CA1264 from the upper marly part of the Kilya Member in Wadi 

 Kilya. 



Description. SM F. 1 2202 is a large quarter-whorl fragment of a 

 body-chamber, of approximately 50 mm whorl height and 49 mm 

 whorl breadth, corresponding to a size of about 160 mm diameter; a 

 small part of the next inner whorl is present in the umbilicus. 

 CA1264 is a poorly preserved phragmocone ending at about 90 mm 

 diameter, to which are attached parts of the body-chamber extending 

 for nearly three-quarters of a whorl further, but the mouth-border is 

 not present. On all whorls the whorl section is smoothly rounded and 

 the venter evenly arched; the inner whorls are compressed, but larger 

 outer whorls are about as thick as high. The ribs are fine and dense 

 on the inner whorls and divide into two or three secondaries; on SM 

 F. 12202 the primary ribs become much more widely spaced and 



