UPPER CRETACEOUS AMMONITE 
C.93547-51, C.93904-8, Pindiga Formation, unit T2, Ashaka. 
The subspecies also occurs in unit T1 at Ashaka. 
DIMENSIONS 
D Wb Wh U 
C.93365 64 48 (75) 32 (50) 13 (20) 
93550 49 45 (92) 21 (43) = 
C.93549 46 30 (65) 21 (46) = 
C.93551 4) 34 (83) AL (SIV) 10.5 (26) 
93548 37 23 (62) 17 (46) 6 (16) 
REMARKS. V. globosum proprium is generally a distinctive form 
on account of its narrow umbilicus, representing 15-28% of the 
total diameter, its deeply incised sutures often showing elongate 
saddles (Fig. 49), and its juvenile ornament of sharp ribbing, 
almost always confined to the outer flanks and venter. 
Associated with the juvenile ribs there may be pronounced 
onstrictions which persist until diameters of about 25 mm (Figs 
53, 64). Umbilical bullae may or may not be present in the early 
2rowth stages. The material from unit T2 at Ashaka varies from 
oderately compressed (Fig. 45) to highly depressed forms (Fig. 
7). The latter resemble the stratigraphically younger V. 
zlobosum globosum. Their juvenile ribbing style is closer to that 
n Ke globosum proprium, however, and they are here treated as 
*nd members of that subspecies; similar variants occur in an 
issemblage of V. globosum proprium from Texas (Kennedy et al. 
987). 
Some individuals have subdued ornamentation. The holotype 
f Gombeoceras? bulbosum Reyment (C.47295, Reyment 1954b: 
1. 4, figs 2a, b) isa smooth V. globosum proprium. 
The holotype of Vascoceras ellipticum Barber (C.47679, 
3arber 1957: pl. 6, figs la, b; pl. 26, fig. 11) is probably a further 
xample of V. globosum proprium. Other individuals referred to 
‘ ellipticum by Barber (C.47680-4) are of uncertain affinities. 
whe example from Dukul (C.47633, Barber 1957: pl. 14, figs la, 
); pl. 26, figs 3, 4) is an involute abraded specimen difficult to 
Jentify with certainty. After dissection many such forms found 
dose at Dukul prove to be Thomasites gongilensis. 
Courville (1992: 424, pl. 10, fig. 2) reported a specimen of V. 
Vobosum proprium (his V. gr. obscurum Barber) from unit U (his 
iveau 32) at Ashaka. The associated fauna described therein, 
owever, is that typical of unit T2 (= upper part of his Niveau 30 
at Ashaka. In the present work V. globosum proprium has been 
und only in unit T. 
In its complex sutures and constricted inner whorls V. 
lobosum proprium resembles V. venezolanum Renz (1982: 80, pl. 
3, figs S—11; pl. 24, figs 1-10; pl. 25, figs 1-8; text-fig. 61). The 
itter, highly variable species, however, generally shows denser, 
1ore persistent ribs which cross the flanks, although certain 
idividuals may have subdued ribbing. V. venezolanum is known 
om southern Nigeria (Zaborski 1990b) but from beds 
Intaining Mammites nodosoides (Schliiter) which are younger 
1an unit T at Ashaka. 
Jascoceras obscurum Barber, 1957 
Figs 53, 54, 59, 61, 62 
57 Vascoceras obscurum Barber: 19, pl. 6, figs 3, 9; pl. 27, 
figs 16-18. 
289 Vascoceras obscurum Barber; Meister: 28, pl. 12, fig. 2; 
text-fig. 20. 
81 
MATERIAL AND OCCURRENCE. Five specimens, C.93552-3, 
C.93909-10, Pindiga Formation, unit T2, Ashaka; C.93326, 
Pindiga Formation, unit X, Ashaka. 
DIMENSIONS. 
D Wb Wh U 
C.93909 64 29 (45) 31 (48) 6(9) 
C.93553 48 24 (50) 26 (54) 4 (8) 
C.93326 44 21 (48) 24 (54.5) 4 (9) 
C.93552 38 19 (50) 20 (53) 4 (10.5) 
REMARKS. V. obscurum is a highly involute compressed species 
with a flattened to tabulate venter in its early stages which 
becomes rather more rounded during growth. The juvenile 
whorls bear strong regular ribs, some of which reach the 
umbilicus but which are mainly confined to the ventral region. 
The sutures are complex for the genus with fairly elongated 
highly frilled saddles (Fig. 59). 
V. obscurum appears in unit T2 at Ashaka, occurring there 
alongside V. globosum proprium. A similar style of ribbing and 
complex suture pattern is present in these two forms. V. 
obscurum could be considered as an end member of V. globosum 
proprium. The consistently high degree of involution, the 
compressed whorls and the flattened venter, however, set V. 
obscurum apart while it has a different stratigraphical range than 
the latter form, being found in unit X at Ashaka. For these 
reasons V. obscurumis here treated as a discrete species, though it 
is clearly very closely related to V. globosum proprium from which 
it is probably derived. 
The early whorls in V. obscurum resemble those in V. pioti 
(Peron & Fourtau) (see Freund & Raab 1969: 28, pl. 4, figs 1-9; 
text-figs 6d—g). The later growth stages, however, are unknown in 
the former, precluding comparison with the Neoptychites-like 
body-chamber in V. pioti. 
In what is known of its morphology V. obscurum shows a close 
similarity to Neoptychites. Pronounced constrictions have not 
been seen in the available material but are found in the related V. 
globosum proprium. The V. globosum proprium-V. obscurum 
lineage may contain the root stock of Neoptychites. 
Very similar to V. obscurum are the Neoptychites sp. juv. of 
Freund & Raab (1969: 47, pl. 8, figs 3-6) from Israel which occur 
well below the main stratigraphical range of the genus there. 
Material from unit O at Ashaka referred to Neoptychites by 
Meister (1989: 12, pl. 14, text-fig. 4) is, as mentioned above, an 
early Thomasites. That described by Courville (1992: 421, pl. 12, 
fig. 2) from unit R as Neoptychites aff. cephalotus (Couttiller) is 
probably a member of the V. globosum group. 
Vascoceras harttii (Hyatt, 1870) Figs 58, 60 
1870 Ceratites harttii Hyatt; 386. 
1875 Buchiceras hartti (Hyatt) Hyatt: 370. 
1887 Ammonites (Buchiceras) harttii (Hyatt); White: 226, 
pl. 19, figs 1, 2; pl. 20, fig. 3. 
1903 Vascoceras hartti (Hyatt) Hyatt: 103, pl. 14, fig. 16. 
1936 Vascoceras hartti (Hyatt); Maury: 247, pl. 22, figs 1, 2. 
1978  Paravascoceras hartti (Hyatt) Chancellor, Reyment & 
Tait: 96, fig. 20. 
1982 Paravascoceras hartti (Hyatt); Chancellor: 98, figs 28C, 
29-33. 
1985 Vascoceras ( Paravascoceras ) harttii (Hyatt); Howarth: 
