90 



M.K. HOWARTH 



Tithonian in Argentina] . This is a major discrepancy between the age 

 of Choicensisphinctes in South America and Yemen, where C. 

 limitis cannot be older than Durangites Zone, from the presence of 

 Spiticeras, Berriasella, Substeueroceras, Blarifordiceras, and 

 Malbosiceras at the same horizon. 



Occurrence. Ams and basal Mintaq Members, Hajar Forma- 

 tion, eastern Jebel Billum; Durangites Zones, Upper Tithonian. 



Family NEOCOMITIDAE Salfeld, 1921 



Subfamily BERRIASELLINAE Spath, 1922 



Genu?, BERRIASELLA Uhlig, 1905 



Type SPECIES. Anunonites privasensis Piciet, 1867, subsequently 

 designated by Roman (1938). 



Synonyms. Stenoceras Uhlig, 1911 (type species, Hoplites storrsi 

 Stanton, 1 &96), Parodontoceras Spath, 1923a (type species: Hoplites 

 callistoides Behrendsen, 1891); Hegaratella Nikolov & Sapunov, 

 1977 (type species, Berriasella paramacilenta Mazenot, 1939). 



Subgenus BERRIASELLA Uhlig, 1905 



Berriasella (Berriasella) oppeli (Kilian, 1889) 



PI. 19, figs 3, 4 



1868 Ammonites callisto d'Orbigny; Zittel: 100, pi. 20, figs 1-4. 



1889 Perisphinctes oppeli Kilian: 662. 



1939 Berriasella oppeli (Kilian); Mazenot: 49, pi. 3, figs 1-3, 6- 



8. 

 1960 Berriasella oppeli (Kilian); Drushchits & Kudriavtseva: 



275, pi. 20, figs 2. 3. 

 1973 Berriasella (B.) oppeli (Kilian); Le Hegarat: 58, pi. 5, figs 



1, 2; pi. 38, figs 4, 5 (see for synonymy). 



Material. 18 specimens, CA9 14-31, from the shell bed 26 m 

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



Description. These are all crushed fragments of whorls up to 

 about 28 mm whorl height and 75 mm diameter. Prior to crushing the 

 whorl section appears to have been moderately compressed and with 

 a narrow flat venter. Sharp, straight primary ribs mostly bifurcate on 

 the ventral half of the whorl side, but occasional ribs trifurcate or 

 remain single; the secondaries bend gently forwards near the venter, 

 and a marked interruption can be seen on most specimens in the 

 middle of the venter. 



Remarks. This crushed material from a shell bed represents a 

 species of Berriasella closely similar to the type species, B. 

 privasensis (Pictet). It differs from the latter mainly in having 

 straight, rather than flexuous, ribs, and a flat, rather than arched, 

 venter. No mouth-borders, lappets or suture-lines are preserved on 

 any of the specimens, but some of the larger ones are probably 

 fragments of body-chambers . B. oppeli first appears in the Durangites 

 Zone at the top of the Tithonian and persists into at least the lower 

 half of the overlying Euxinus Zone, according to the records of Le 

 Hegarat ( 1973: 5 1 , 60) and Nikolov ( 1982: 56), and it is an important 

 occurrence for the dating of the lower part of the Arus Member in 

 eastern Jebel Billum. 



Occurrence. Arus Member, Hajar Formation, eastern Jebel 

 Billum; Durangites Zone, Upper Tithonian. 



Berriasella (Berriasella) cf. oxycostata Mazenot, 1 939 



PI. 19, figs 7, 9 



1939 Berriasella oxycostata [Jacob MS, 1904; Breistroffer, 1 937, 



nom. nud.] Mazenot: 51, pi. 3, fig. 9. 

 1973 Berriasella (Picteticeras) oxycostata (Jacob); Le Hegarat: 



78, pi. 8, figs 4-6; pi. 40, figs 2-4. 



Material. Seven specimens, CA776-82, from the microbialite 

 boulders in the Arus Member in Wadi Arus. 



Remarks. These are small specimens and fragments of up to 50 

 mm diameter. All have fairly evolute whorls, single primary ribs 

 bifurcating at ventro-lateral tubercles, and ventral tubercles border- 

 ing a mid- ventral interruption. Two of the better preserved specimens 

 have whorl measurements and sharp ribs very similar to those in 

 Berriasella oxycostata as figured by Mazenot, though their frag- 

 mentary nature hardly allows a determination more definite than 'cf." 

 to be made. Mazenot's species occurs in the top of the Tithonian and 

 the bottom of the Berriasian, according to the stratigraphical data of 

 Le Hegarat (1973: 52). 



Occurrence. Lower part of Arus Member, Hajar Formation, 

 Wadi Arus; Microcanthum Zone, Upper Tithonian. 



Berriasella (Berriasella) aff. chomeracensis (Toucas) 



PL 19, fig. 8 



1890 Hoplites callisto var. chomeracensis Toucas: 601, pi. 17, 



figs 8, 9. 

 1939 Berriasella chomeracensis (Toucas); Mazenot: 62. pi. 6. 



figs 1-7. 

 1973 Berriasella (Picteticeras) chomeracensis (Toucas); Le 



Hegarat: 70, pi. 7, figs 3-5, pi. 39, fig. 12. 

 1 982 Berriasella (Picteticeras) chomeracensis (Toucas); Nikolov: 



65, pi. 14, figs 1-5. 



Material. CA672 from bed 29 and CA673 from bed 60 in the 

 Mintaq Member, Mintaq Salt Dome. 



Description. CA673 is a complete adult microconch with long 

 lappets at 35 mm diameter; CA672 is a half-whorl fragment, slightly 

 larger and incomplete. The whorls are evolute, not compressed, and 

 have a broad rounded venter. The primary ribs are slightly flexuous 

 on the side of the whorl; a few remain single, others bifurcate about 

 the middle of the whorl side, and there are a few intercalated 

 secondaries; they pass across the rounded venter, where there is a 

 mid-ventral interruption. On the last part of the whorl of CA673 

 there are 12 primary ribs and 24 secondaries. 



Remarks. These small specimens resemble Berriasella 

 chomacerensis in whorl shape, rib style (ie. slightly flexuous) and 

 small adult size (one is a complete microconch at 35 mm diameter), 

 but they have fewer single ribs. In SE France, B. chomacerensis 

 occurs in the Euxinus Zone (Le Hegarat, 1971: 51). but Nikolov 

 (1982: 65) recorded it at higher levels up to the Boissieri Zone in 

 Bulgaria. Its date in the Occitanica Zone in Yemen is the same as that 

 of fi. privasensis. which is more involute, has more ribs and attains 

 considerably larger sizes (complete microconchs are 65-75 mm 

 diameter). 



Occurrence. Mintaq Member. Mintaq Salt Dome: Occitanica 

 Zone, BeiTiasian. 



Subgenus ELENAELLA Nikolov, 1966 



Type species. Berriasella cularensis Mazenot, 1939. 



Synonym. Delphinella Le Hegarat, 1971 (type species, Hoplites 

 delphinensis Kilian, 1889). 



