68 



M.K. HOWARTH 



Remarks. Aspidoceras apenninicum is one of the most evolute 

 species of Aspidoceras. Its evolute, massive whorls, with rudimen- 

 tary ribbing, two rows of large tubercles and raised mid-venter are 

 distinctively different from the more involute, globose and smoother 

 whorls of most other species. The outer whorls of Pseudowaagenia 

 acanthomphala (Zittel, 1869; 1870: 79, pi. 5, fig. 4; Checa, 1985: 

 127) bear some resemblance, but they are smaller and less massive, 

 and the inner whorls are compressed, more involute and have many 

 more, smaller umbilical tubercles. Inner whorls are not preserved in 

 the present collection, but these large massive body-chambers are 

 unlikely to belong to Pseudowaagenia. Zittel's (1870) originals and 

 Canavari's (1901) figured specimens are from the Apennines of 

 central Italy where they occur in the top Kimmeridgian or bottom 

 Tithonian, but are not well-dated in terms of modem zones. Checa 

 (1985:85, lll)had better evidence from south-east Spain where the 

 species occurs mainly in the Beckeri Zone and less commonly in the 

 upper part of the Eudoxus Zone below. A large well-preserved 

 specimen from Ethiopia, which is possibly still septate at its maxi- 

 mum size of 166 mm diameter, was figured as Aspidoceras evolutum 

 by Scott (1943: pi. 17, figs 1, 4); its age was not accurately 

 determined, but could be Beckeri Zone, like many of the other 

 ammonites described by Scott, Together with Collignon's (1959) 

 specimen from a similar horizon in Madagascar and Verma & 

 Westermann's (1984) example from the Beckeri Zone at Mombasa, 

 these are the only previous records of this species in the east African 

 - Indian Ocean area. 



Occurrence. Middle part of the Kilya Member, Wadi Kilya; 

 Beckeri Zone, Upper Kimmeridgian. 



Genus ORTH ASPIDOCERAS Spath, 1925 



Type species. Ammonites orthocera d'Orbigny, 1850. 



Synonyms. Glabrophysodoceras Scott, 1943: 82 (type species, 

 G. abyssinianum Scott, 1943); Shaireria Checa, 1985: 184 (type 

 species, Aspidoceras avellanum Zittel, 1870). 



Orthaspidoceras gortanii (Venzo, 1959) PI. 12, figs 1, 2 



Aspidoceras liparum (Oppel); Venzo: 160, pi. 9, figs ?4, 5; 



pi. 13, fig. 2. 



Physodoceras altenense d.''Ovh\gny\'WQnzo: 168, pi. 14, fig. 



5. ' 



Physodoceras gortanii Wenzo: 173, pi. 11, fig. 1. 



Ortliaspidoceras gortanii (Venzo); Checa: 171, fig. II.3.42B; 



pi. 33, fig. 2. 



1959 



1959 



1959 

 1985 



Material. Five specimens, CA 1039^3, 19.7 m above the base 

 of the Kilya Member in Naifa Cliff. 



Description. All five specimens are body-chambers; three are 

 complete and adult at 140, 147 and 154 mm diameter, with body- 

 chambers 200°-2 1 5° long; one is complete but immature at 1 30 mm 

 diameter; one has the final quarter whorl missing. The final septum 

 at the end of the crushed phragmocone is present in all five, but no 

 earlier whorls are preserved. The whorls are involute and globose, 

 though the umbilicus widens markedly towards the final mouth- 



border. The whorl secfion is elliptical, slightly depressed, with 

 vertical umbilical walls, and evenly rounded whorl sides and venter. 

 Large spiny umbilical tubercles project mainly normal to the shell 

 surface, though a few are directed inwards over the umbilicus. Many 

 tubercles tend to be clavate, and they are widely spaced, at a density 

 of only 2 or 3 on the final half whorl of the body-chamber (ie. 4-6 per 

 whorl at 150 mm diameter). Irregular fold-like ribs of very low relief 

 are present on most specimens, and in one they become more 

 prominent in the ventro-lateral region. Striae of similar shape are 

 present where the shell is preserved. 



Measurements 











D 



Wh 



Wb 



U 



CA1039 



138 



53.5 (0.39) 



56.5 (0.41) 



43.0(0.31) 



CA1041 



149 



51.0(0.34) 



54.0 (0.36) 



54.5(0.37) 



CA1040 



132 



48.5 (0.37) 



50.0 (0.38) 



42.5(0.32) 



CA1042 



126 



48.5 (0.38) 



50.5 (0.40) 



31.5(0.25) 



C A 1043 



120 



53.0(0.44) 



54.5 (0.45) 



32.0(0.27) 



Remarks. The evenly rounded globose whorls, and the single 

 row of tubercles, here placed near the umbilical edge rather than 

 mid-laterally, are characteristic of Orthaspidoceras. Although 

 there are several closely similar species to which these Yemen 

 specimens might belong, there is no doubt that they are the same 

 as three specimens from Ethiopia figured by Venzo. one of which 

 (Venzo, 1959: pi. 11, fig. 1) is the holotype of O. gortanii; they 

 have widely spaced tubercles, only 4-6 per whorl, on the body- 

 chamber. The Beckeri Zone date of O. gortanii in Yemen suggests 

 that this might also be the date of the Ethiopian specimens, though 

 Zeiss (1971: 537, table 1) placed them slightly lower, in the 

 Eudoxus Zone. Other species that are similar to O. gortanii are O. 

 liparum (Oppel; holotype figured by Checa, 1985: pi. 33, fig. I), 

 and O. lallierianum (d'Orbigny, 1850: 542, pi. 208; type speci- 

 mens figured by Hantzpergue, in Fischer, 1994: 178, pi. 80, figs 1, 

 2), which have slightly more umbilical tubercles and occur in the 

 Eudoxus Zone. 



Occurrence. The lower marly part of the Kilya Member. Naifa 

 Formation, Naifa Cliff; Beckeri Zone, Upper Kimmeridgian. 



Orthaspidoceras avellanum (Zittel, 1 870) 



PI. 10, figs 2, 4; PI. 11, fig. 2 



1870 Aspidoceras avellanum Zittel: 86, pi. 7 (31 ), figs 2, 3. 

 1872a Aspidoceras avellanum Zittel; Gemmellaro: 151, pi. 18, 



fig. 3 [p. 51, pi. 10, fig. 3 in reprint]. 

 1905 Aspidoceras altenense (d'Orbigny); Dacque: 150, pi. 17, 



fig- 2. 

 71930 Acanthosphaerites deaki (Herbich); Spath: 60, pi. 8, figs 3, 



5,6. 

 71943 Physodoceras altenense (d'Orbigny); Scott: 80, pi. 17, figs 



2,3. 

 71943 Physodoceras gregoryi (Spath); Scott: 81, pi. 16, figs 2, 4. 

 1943 Glabrophysodoceras ganamense Scott: 83, pi. 19, figs 2, 3. 

 1960 Physodoceras avellanum (Zittel); Collignon: pi. 160, figs 



635, 636. 

 1984 Aspidoceras (Physodoceras) cf. avellanum Zittel; Verma & 



Westermann: 70, pi. 17, fig. 2. 



PLATE 12 



Figs L 2 Orthaspidoceras gortanii (Venzo), 19.7 m above the base of the Kilya Member (fauna 7), Naifa Cliff, la, lb, CA1039, xO.( 



xO.68. 

 Fig. 3 Simaspidnceras argobbae (Dacque), Breadloaf Concretions, Kilya Member (fauna 7), east cliff, Wadi Arus. 3a, 3b, CA742. 

 Fig. 4 Aspidoceras apeninnicum Zittel, upper part of middle limestone part of Kilya Member (fauna 7), Wadi Kilya. 4a, 4b, CAl 191 

 Fig. 5 Laevaptychus, lower marly part of Kilya Member (fauna 7), Wadi Kilya. 5a, 5b, matching pair of aptychi, C A 1 230, 1 23 1 . 



B; 2a, 2b, CAl 040, 



xO.69. 



J 



