AMMONITES AND NAUTILOIDS OF WADI HAJAR 



ribs, and have non-tuberculate ribs between. Some species develop 

 more robust, quadrate whorls, some have widely spaced ribs on 

 inner whorls, and the ribs without tubercles may fade at larger sizes. 

 All the synonyms listed above agree with these characters. The 

 biostratigraphic range from Upper Tithonian to the top of the 

 Berriasian is similar to the range of Berriasella. 



Malbosiceras cf. aizyensis Mazenot, 1939 Pi. 20, figs 4, 8 



1939 Berriasella aizyensis Mazenot: 86, pi. 9, figs 4-6; pi. 10, 



fig- 1. 

 1973 Malbosiceras aizyensis (Mazenot); Le Hegarat: 82, pi. 9. 



figs 3, 4. 



Material. Eight specimens, CA932-39, from the shell bed 26 m 

 above the base of the Arus Member, eastern Jebel Billum. 



Remarks. These are all small fragments from ammonites of up to 

 60 mm diameter. They have widely spaced, wiry primary ribs that 

 divide into 2, 3 or 4 secondaries. The lateral tubercle is just begin- 

 ning to develop at 50-60 mm diameter, but as in Mazenot's originals 

 it is inconspicuous at these small sizes. All are more coarsely ribbed 

 than Berriasella (B.) oppeli which occurs in the same shell bed. 

 Malbosiceras aizyensis occurs in the top of the Upper Tithonian in 

 SE France according to the records of Mazenot (1939) and Le 

 Hegarat (1973). 



Occurrence. Arus Member, Hajar Formation, eastern Jebel 

 Billum; Durangites Zone, Upper Tithonian. 



Malbosiceras sp. indet. 



PI. 21, fig. 2 



Material. CA686 from bed 36 in the Mintaq Member, Mintaq 

 Salt Dome. 



Remarks. This is a large quarter whorl fragment of a body- 

 chamber at about 1 60 mm diameter, that has been crushed obliquely 

 so that the umbilical wall is prominent and the venter mostly 

 missing. The widely spaced ribs have umbilical and lateral tuber- 

 cles, the latter being on the ventral half of the whorl side. Intercalated 

 ribs are feeble or mostly absent. Large fragments of body-chambers 

 of Malbosiceras are not specifically determinable when isolated 

 from their inner whorls. Several have been figured by Mazenot 

 (1939: pi. 11, fig. 3; pi. 12, fig. 5), Le Hegarat (1973: pi. 12, 17, 19) 

 and Nikolov (1982: pi. 54, fig. 2; pi. 58, fig. l).They occur in the top 

 of the Tithonian and especially in the mid to upper parts of the 

 Berriasian according to Le Hegarat's (1973: 83, 1 15) and Nikolov's 

 (1982) stratigraphical records. 



Occurrence. Mintaq Member, Hajar Formation, Mintaq Salt 

 Dome; Occitanica Zone, Berriasian. 



Genus PROTACANTHODISCUS Spath, 1923a 

 Type species. Hoplites andreae Kalian, 1889. 



Protacanthodiscus sp. indet. 



Material. CA687 from bed 149 in the Mintaq Member, Mintaq 

 Salt Dome, and four specimens, CAS 1 1-8 14, from a limestone 55 m 

 above the base of the Mintaq Member in the gorge at the southern 

 end of Wadi Arus. 



Remarks. It is worth recording that ammonites with ventro- 

 lateral tubercles and ribs looped to them in some places accompany 

 Substeueroceras striatum sp. nov. in the shell-bed in the Mintaq 

 Member in Wadi Arus. The ribs are fine and similar to those of S. 



95 



striatum, and there appear to be no umbilical or lateral tubercles. The 

 crushed preservaton is not sufficiently good from them to be 

 illustrated or identified, but Protacathodiscus seems to be the genus 

 to which they should belong, because ventro-lateral tubercles with 

 ribs looped to them do not occur in either Berriasella or 

 Substeueroceras. The example from the Mintaq Salt Dome is a 

 poorly preserved, similarly tuberculate specimen. 



Occurrence. Mintaq Member, Hajar Formation, Wadi Arus and 

 Mintaq Salt Dome; Durangites Zone, Upper Tithonian, or Euxinus 

 Zone (see p. 103), Berriasian, and Occitanica Zone, Berriasian. 



Subfamily NEOCOMITINAE Salfeld, 1921 

 Gtnui ARGENTINICERAS S^?i\h, 1924b 



Type species. Odontoceras malarguense Steuer. 1897. 



Synonyms. Andesites Gerth, 1925 (type species, Perisphinctes 

 loncochensis Steuer, 1897); Boncheviceras Nikolov, 1966 (type 

 species, Berriasella ardescensis Mazenot, 1939). 



Remarks. Argentiniceras is essentially a genus from the Lower 

 Berriasian of the Andean Province, and all the figured material 

 comes from western Argentina, XhonghArgentiniceras also occurs in 

 Colombia, Peru, and the Antarctic Peninsula according to 

 Wiedmann's (1980: 5L fig- 8) map. Records from outside the 

 Andean Province are few. One of them is the type (and only) 

 specimen of Berriasella ardescensis Mazenot, 1939, from the 

 Berriasian of SE France, which was made the type of Boncheviceras 

 Nikolov, 1 966, and is a coarse-ribbed species similar toArgentiniceras 

 malarguense. The only other occurrence is Krishna's (1991) more 

 recent record of two specimens from western India, where they were 

 given a Berriasian date to agree with the date of the genus in South 

 America. Krishna's (1991: pi. l,figs 1,2) figured specimen is a close 

 match for the holotypes of A. malarguense and A. loncochense, 

 having similar coarse secondary ribs and small umbilical tubercles. 

 The six Yemen specimens described here include a new species that 

 has widely spaced primary ribs, as well as an example of the more 

 finely ribbed Argentinian species A. mutatum (Steuer). 



Argentiniceras mutatum (Steuer, 1897) PL 23, fig. 1 



1897 Reineckeia mutata Steuer: 27, pi. 13, figs 1, 2. 



Material. CA693 from bed 57 in the Mintaq Member, Mintaq 

 Salt Dome. 



Description. The specimen consists of a complete body-cham- 

 ber, 210° long, ending in a plain aperture at 106 mm diameter; inner 

 whorls are not exposed, being filled with recrystallized calcite and 

 covered with limestone matrix that cannot be removed. Whorl 

 measurements at the mouth-border are: at 106 mm: 34.2 (0.32). 36.0 

 (0.34), 42.5 (0.40). The whorl section is quadrate, with flat sides and 

 venter. Widely spaced primary ribs divide irregularly into secondar- 

 ies on the upper half of the whorl side, and other secondaries are 

 intercalated. The ribs are continuous across the venter. There are 14 

 primary ribs and about 40 secondaries per half whorl at 105 mm 

 diameter. There are no true tubercles at the umbilical edge, the 

 slightly greater prominence of the ribs here being mainly due to their 

 diminution in the middle of the whorl side. 



Remarks. This ammonite is closely similar to the inner whorl of 

 the 210 mm diameter holotype of A. mutatum, from the Lower 

 Berriasian of NW Agentina. The type species oi Argentiniceras, A. 

 malarguense (Steuer, 1897: 55, pi. 20, figs 1-3), has fewer, coarser 

 ribs and small or incipient umbilical tubercles. The latter are slightly 



