34 M.K. HOWARTH 



Genus Malbosiceras Grigorieva, 1938 94 



Genus Protacanthodiscus Spath, 1923 95 



Germs Argentiniceras Spath, 1924 95 



Genus Tirnovella Nikolov, 1966 97 



Family Ancyloceraddae Gill. 1871 98 



Genus Crioceratites Leveille, 1837 98 



Order Nautilida Agassiz, 1847 98 



Family Paracenoceratidae Spath, 1927 98 



Genus Paracenoceras Spath, 1927 98 



Biostratigraphy 101 



Comparison with East Africa and India 103 



References 104 



Synopsis. Middle Callovian to UpperAptian ammonites described mainly from Wadi Hajar and Jebel Madbi, southern Yemen, 

 include: Middle Callovian, Coronatum Zone. Eiymoceras from the Shuqra Formation; Oxfordian perisphinctids in the Madbi 

 Formation; Upper Oxfordian, Bimammatum Zone, Orthosphinctes, Larcheria, Paiyphoceras and Epimayaites low in the Billum 

 Member, Naifa Formation; a Lower Kimmeridgian. Divisum Zone, CrussoUccras in the upper half, and Upper Kimmeridgian, 

 Eudoxus/Beckeri Zone, Streblites and ITorquatisphinctes at the top of the Billum Member; Upper Kimmeridgian. Beckeri Zone, 

 Taramelliceras, Sutneria, Idoceras, Aspidoceras, Simaspidoceras, Lithacoceras, Pachysphinctes, Torquatisphinctes naifaensis 

 andldoceras ahwarense spp. nov, from the lower and middle parts of the Kilya Member, Naifa Formation, and additionally Lower 

 Tithonian, Hybonotum Zone, Katroliceras, Subdichotomoceras and Hybonoticeras from the upper part; Upper Tithonian, 

 Microcanthum Zone, Aulacosphinctes, Micracanthoceras, Spiticeras, Berriasella, Blanfordiceras. Riasanites rjasanensis, 

 Pseudoclambites araense and Baeticoceras morrisi spp. nov. from the Arus Member, Hajar Formation; Upper Tithonian, 

 Durangites Zone, Virgatosphmctes, Choicensisphinctes, Berriasella, Substeueroceras and Malbosiceras. higher in the Arus 

 Member and low in the Mintaq Member. Hajar Formation; Substeueroceras striatum sp. nov. higher in the Mintaq Member; 

 Beniasian. OccitanicaZone,/4.s/)(V/ocerai-. Berriasella, Tirnovella. Spiticeras, S. pricei, Haploceras umbilicatum andArgentiniceras 

 mintaqi spp. nov., from the middle part of the Mintaq Member; a single Upper Hauterivian Crioceratites low in the Qishn 

 Formation; and UpperAptian Cheloniceras from the upper half of the Qishn Formation. 



INTRODUCTION 



The ammonites and nautiloids described here come from localities 

 and sequences in Wadi Hajar that are descibed in detail in the 

 preceding paper in this Bulletin (Howarth & Morris, 1998). They 

 range in age from the middle of the Callovian to the Upper Aptian, 

 and come from all the formations that make up the Jurassic and the 

 lower part of the Cretaceous in Wadi Hajar, except for the lowest, the 

 arenaceous Kohlan Formation, which overlies the Precambrian 

 basement and contains no fossils. From Callovian to Hauterivian, 

 most horizons are represented, except for two major disconformities, 

 the first missing out the whole of the LowerTithonian except for part 

 of the basal Hybonotum Zone, and the second excluding the upper 

 part of the Berriasian, the Valanginian and Lower Hauterivian. 



About 710 of the specimens were collected by the author and Dr 

 Noel Morris during two visits to Wadi Hajar in November 1991 and 

 January 1 994. To these were added about 20 ammonites from that area 

 given to us by Dr John Smewing, and 79 ammonites collected by Z.R. 

 Beydoun and E.K. Elliott in the mid-1950s, 70 of which are in the 

 Sedgwick Museum, Cambridge, and 9 in the Natural History Mu- 

 seum. That makes a total of 809 ammonites examined for this paper. 

 Many of those from the Upper Kimmeridgian andTithonian are well- 

 preserved, some exceptionally so, while the Callovian and Oxfordian 

 ammonites are crushed and fragmentary, but regretably many of the 

 topmost Tithonian and Berriasian ammonites are not as well pre- 

 served as might be hoped for, given their considerable interest. 



The ammonites collected by Beydoun and Elliott were identified 

 by Spath and Arkell and listed in Beydoun's (1964) description of 

 the Wadi Hajar area, but none were described or figured. They 

 formed the basis of some of Beydoun's age assessments of the 

 formations in that area, which were used as a starting point for the 

 new work described here. 



Few other ammonites have been described and figured from any 

 part of Yemen. From Wadi Hajar itself, three fragments of Upper 

 Kimmeridgian Pachysphinctes and ILithacoceras were figured by 

 Stefanini (1925: 142-48, pi. 27, figs 1-3), that were the result of 

 Little's (1925) pioneering geological exploration up Wadi Hajar in 

 1 920. These can now be identified as coming from the middle part of 

 the Kilya Member, Naifa Formation, at Naifa Cliff, the type locality 

 of the Naifa Formation. Earlier Crick ( 1 908: 1 1-24. pi. 2, figs 2, 3, 

 pi. 3, figs 1-4) had described five perisphinctids, one oppelid and 

 two nautiloids ilParacenoceras) from near Dihala, about 150 km 

 north of Aden. They are in the collections of the Natural History 

 Museum, but are too poor for more accurate identification, though it 

 is likely that the perisphinctids are of (?Upper) Kimmeridgian age 

 and from rocks that would now be referred to the Naifa Formation or 

 its equivalent in that area. Finally, Tipper (1910: 338, pi. 35, figs 1, 

 2, pi. 36, figs 1, 2) described some perisphinctids from a limestone 

 in the same area north of Aden, which are also poorly preserved, 

 though Pachysphinctes is a possible determination for two of them 

 (pi. 35, figs 1. 2), and they might also be Upper Kimmeridgian in 

 age. No other ammonites have been described from Yemen. 



The Jurassic and Lower Cretaceous ammonite zones and the 

 lithological formafions from which the Wadi Hajar ammonites were 

 collected are shown in Table 1. The ammonite faunas described 

 belong to the 14 biostratigraphical horizons indicated by asterisks in 

 that Table, the age evidence for which is discussed in the final part of 

 the present paper 



SYTEMATIC DESCRIPTIONS 



Specimen register numbers with the prefixes CA or C. (ammonites) 

 and CN (nautiloids) are in the collections of The Natural History 



