62 



M.K. HOWARTH 



1905 Simoceras cf. sautieri (Fontannes); Kilian & Guebhard: 



827, pi. 50, fig. 2. 

 1912 Nebrodites haizmanni Burckhardt: 89, pi. 22, figs l-A. 

 1959 Nebrodites (Nebrodites) hospes hospes (Neumayr); Ziegler: 



38, pi. l,figs 15, 16. 

 1959 Nebrodites (Nebrodites) hospes tninor (Qxienstedi); Ziegler: 



38, pi. l,fig. 17. 



Material. One specimen, CA736, from the Breadloaf Concre- 

 tions in the Kilya Member in the east cliff of Wadi Arus. Several 

 examples were seen in a bed of shell debris in the middle limestone 

 part of the Kilya Member, in the section south of Wadi Kilya; though 

 too fragile to be collected, two specimens were photographed in the 

 field. 



Description. The small specimen from Wadi Arus is an adult 

 microconch. It is almost complete at its aperture at 40 mm diameter, 

 where two large flared ribs are separated by a narrow constriction, 

 and only the lappet is missing in the mouth-border. The whorls are 

 evolute and quadrate. The ribs are straight and radial, a few bifurcate 

 either at the umbilical edge or near the middle of the side of the 

 whorl, then they pass onto the tabulate venter, which has a smooth 

 central band. Several constrictions are present. The specimens pho- 

 tographed in Wadi Kilya were 125-150 mm diameter; they had 

 similarly evolute whorls and parts of their body-chambers pre- 

 served. 



Remarks. Though species of Nebrodites are clearly dimorphic, 

 macroconchs and microconchs have not been associated in the 

 same described species. Many microconchs have been referred to 

 the species N. hospes (Neumayr), which occurs in the Acanthicum 

 Zone and lower half of the Eudoxus Zone in south-western Ger- 

 many, where complete adults are 25-60 mm diameter. Several 

 complete specimens were figured by Quenstedt (1888) and Ziegler 

 (1959), while smaller (25-40 mm diameter) and more finely 

 ribbed specimens were referred to N. macerrimus (Quenstedt; 

 Ziegler, 1959: 40, pi. 1, fig. 18). The many very much larger 

 macroconchs figured by Gemmellaro (1872b) and Ziegler (1959), 

 that have plain mouth-borders without lappets, range up to 260 

 mm diameter. The inner whorls of some of these, eg. N. peltoideus 

 and A', cafisii (Gemmellaro, 1872b: 154, 156, pi. 3, figs 5, 6 [pp. 

 47, 49, pi. 8, figs 5, 6 in the reprint]; Ziegler, 1959: 36, pi. 1, figs 

 10, 11), look to be idenfical with some examples of M hospes. and 

 it may be that the latter species is the microconch, and thus a 

 junior synonym, of one of the earlier described Gemmellaro spe- 

 cies. N. cafisii is one of the highest species to occur in south-west 

 Germany, in White Jura 84, in the upper half of the Eudoxus Zone, 

 according to the records of Ziegler (1958a: 185; 1959: 36). The 

 Yemeni specimens might belong to this species, and it might be 

 necessary to extend its range (and that of the genus) into the 

 Beckeri Zone on account of its association with other ammonites 

 of that date in Yemen. 



A specimen from the Mandawa-Kilwa area of southern Tanzania, 

 of uncertain date in the Kimmeridgian, figured as A^. 

 aethiopicoherbichi Dietrich ( 1 925 : 14, pi. 2, fig. 2), has similar inner 

 whorls, but has coarse widely spaced ribs on its outer whorl and 

 belongs to the subgenus Mesosimoceras. A large fragment from 

 Ethiopia referred to the same species by Venzo( 1959: 157, pi. 8, fig. 

 1) is not determinable, and examples from north-west Madagascar 

 were recorded by Besairie (1936: 64) but not figured. These are the 

 nearest occurrences of Nebrodites to southern Yemen. 



Occurrence. Lower and middle parts of the Kilya Member, 

 Wadi Arus and Wadi Kilya; Beckeri Zone, Upper Kimmeridgian. 



Family PACHYCERATIDAE Buckman, 1918 

 Genus ERYMNOCERAS Hyatt, 1900 



Type species. Ammonites coronatus Bruguiere, 1789. 



Subgenus PACHYERYMNOCERAS Breistroffer, 1947 

 Type SPECIES. Pachyceras jarryi DouviWe. 1912. 



Erymnoceras (Pachyerymnoceras) jarryi (Douville, 1912) 



PI. 11, fig. 4 



1912b Pachyceras jarryi Douville: 37, figs 37^3; pi. 1, figs 3-5, 



7,8,10,12. 

 71970 Erymnoceras (Pachyerymnoceras) cf. jarryi (Douville); 



lmlay:D13, pi. 2, figs 1,2. 

 1 977 Pachyceras (Pachyervmnoceras) jarryi Douville; Charpy 



& Thierry: 206-208, figs 4D, 4E; pi. 3, figs 1, 2; pi. 5, figs 



2,3. 

 1983 Pachyerymnoceras cf Jarryi (Douville); Lewy: 26, figs 6B, 



6H; pi. 4, fig.3. 



Material. Three specimens: CA838 from 17 m below the top of 

 the Upper Shuqra (ie. below the base of the Lower Storm Bed at the 

 bottom of the Madbi Formation) and 6 m above the limestone 

 containing large Paracenoceras meridionale Tintant in central Jebel 

 Billum; CAl 181 from a similar horizon in the Upper Shuqra, 1 km 

 east of the road south of the Al Ma' abir river crossing; and C A 1182 

 from the top part of the Middle Shuqra at the same locality. 



Description. All three specimens are crushed and distorted to 

 varying amounts. CA838 has slightly distorted phragmocone up to 

 about 40 mm diameter, followed by three-quarters of a whorl of a 

 more severely crushed body-chamber, and is probably complete at 

 its aperture at 60 mm diameter. CA 1181 has part or all of its body- 

 chamber preserved, is 65 mm diameter, crushed laterally, and the 

 ornament is fairly well seen. CAl 182 is 80 mm diameter and is very 

 rough and weathered, but probably has most of its body-chambers 

 preserved; on account of its preservation it is best determined as 

 Eiymnoceras (Pachyermnoceras) cf. jarryi. The whorls are de- 

 pressed and cadicone, with a funnel-shaped umbilicus, and an 

 angled umbilical edge leading almost directly into a broad arched 

 venter. The body-chambers might be less depressed, but it is difficult 

 to see the original shape of the whorl section. Bold ribs issue in twos 

 or threes from prominent tubercles on the umbilical edge, and a few 

 of them branch again, or more ribs are intercalated, just above the 

 tubercles. The ribs cross the venter radially or are angled slightly 

 forwards, and diminish considerably along the mid-ventral line. 

 There are 12-13 umbilical tubercles and 36-38 ribs on the venter of 

 the final whorl of CA838. 



Remarks. Allowing for the distortion, the figured specimen (PI. 

 ll,fig. 4) is closely similar to Douville's (1912b: pl. 1, figs 10, 10a) 

 holotype, which is an undistorted specimen from the Upper Callovian 

 (probably Lamberti Zone) of Normandy. More specimens from this 

 area, including a neotype, were figured by Charpy & Thierry (1977: 

 pl. 5, fig. 2). Examples of Pachyerymnoceras from Jebel Tuwaiq, 

 central Saudi Arabia, have been figured by Arkell (1952), Imlay 

 (1970) and Enay et al (1987), and from Israel and Sinai by Lewy 

 (1983) and Gill et al (1985). The varying amounts of distortion 

 suffered by most specimens have led to different species classifica- 

 tions that are difficult to reconcile, eg. the Jebel Tuwaiq specimen 

 figured by Imlay (1970: pl. 2, figs 1, 2), which is very like the Jebel 

 Billum specimen, was referred to the new s^tcitsPachyerymnoceras 

 levantinense by Lewy (1983: 25) on account of its sudden change to 



