76 
Adult V. woodsi are closely similar to V. gamai Choffat (1898: 
54, pl. 7, figs 1-4; pl. 8, fig. 1; pl. 10, fig. 2; pl. 21, figs 1-4; see also 
Berthou et al. 1985 for a revision of the species). The strong 
regular ribbing of the early whorls in V. gamai figured by Choffat 
(1898: pl. 7, figs 3, 4; pl. 8, fig. 4; pl. 10, fig. 2), however, differs 
from the ornament at the same stages in V. woodsi. It should be 
noted that certain juvenile specimens from Portugal show 
similarities with some Nigerian individuals: compare C.91264 
(Fig. 11) with V. silvanense Choffat (1898: pl. 8, fig. 5), and 
C.93351 (Fig. 29) with Berthou et a/. (1985: pl. 3, figs 4, 8, 9). A 
more complete knowledge of the early whorls in V. gamai is 
necessary for full comparison with V. woodsi. 
Closer to the Nigerian juveniles is V. diartianum, particularly 
material from Germany which reaches diameters of over 30 mm 
(see Forster et al. 1983). This collection includes individuals with 
rather rounded umbilical tubercles (Forster et al. 1983: pl. 3, fig. 
1; compare with Zaborski 1990a: fig. 20) and others with highly 
bullate umbilical tubercles similar to those common in V. woodsi 
(compare Forster et al. 1983: pl. 3, figs 2-5 and C.91263, 
C.91257, Figs 28, 30 herein). V. woodsi is a little younger than V. 
diartianum and derivation from the latter can easily be imagined 
by peramorphosis and further simplification of suture pattern. 
The material from Ashaka described by Meister (1989: 11, pl. 
4, figs 2, 3, 5; text-fig. 8) as Plesiovascoceras aff. gr. thomi 
(Reeside) belong in V. woodsi; Vascoceras thomi Reeside (1923) is 
a synonym of Fagesia catinus (Mantell) (see also Wright & 
Kennedy 1981: 88, 97). Those he referred to Paravascoceras gr. 
evolutum Scheegans are partly V. woodsi (Meister 1989: pl. 5, fig. 
4) and probably partly Pseudaspidoceras pseudonodosoides 
(Choffat) (Meister 1989: pl. 5, fig. 2). Paravascoceras cauvini vat. 
evoluta Schneegans (1943: 130, pl. 8, fig. 2) is here considered to 
be a strict synonym of Paravascoceras cauvini. 
Specimens of Vascoceras described by Zaborski (1990a: 5, figs 
9, 10) are further examples of V. woodsi. They were incorrectly 
reported as having come from the Gadeni Zone at Pindiga but 
are from large exotic blocks derived from unit N upstream and 
not from the immediately adjacent unit A. 
Specimens from the Algerian Sahara referred to V. gamai by 
Collignon (1965: 185, figs 5—7) are a very close match for adult V. 
woodsi and may be conspecific. Unfortunately their inner whorls 
are completely unknown. 
Vascoceras bullatum Schneegans, 1943 
Figs 13, 33-35 
1943 Parayvascoceras  crassus  (Furon) var.  bullata 
Schneegans: 131, pl. 8, figs 3, 4. 
1989 Paravascoceras crassum (Furon); Meister: 18, pl. 6, figs 
2, 3; text-fig. 12. 
1989 Paravascoceras carteri (Barber); Meister: 21 (pars), pl. 
9, fig. 1 (only). 
1992 Vascoceras gr. crassum (Furon) ou costellatum 
Collignon; Courville: pl. 5, fig. 2; pl. 6, fig. 1. 
MATERIAL AND OCCURRENCE. Eleven specimens, C.93508-15, 
C.93516a-c, Pindiga Formation, unit O, Ashaka. 
DIMENSIONS. See Fig. 12. 
P.M.P. ZABORSKI 
REMARKS. Members of this species are relatively evolute and 
generally show markedly depressed whorls with a rounded to 
subtriangular outline. Umbilical bullae may or may not be 
present. The evenly frilled sutures are characterized by a broad 
low E/L and a narrow L. 
Most individuals are readily recognizable due to the 
development of regular ribbing on the flanks and venter during | 
their middle ontogenetic stages. The ribs may be coarse and — 
rounded but vary to finer, denser structures in other individuals. 
Although this ribbing may be developed at diameters of less — 
than 20 mm, some specimens remain smooth throughout | 
ontogeny (see Fig. 13; Meister 1989: pl. 9, fig. 1). Regularly | 
developed ribbing may be a transient feature which disappears | 
or weakens greatly on the later septate whorls. The more involute — 
members of the species overlap in shell proportions with certain — 
Vascoceras globosum costatum and Pseudovascoceras nigeriense 
(see Fig. 12) and such individuals may be difficult to differentiate 
if they lack ribbing. 
The juvenile whorls are not distinctive. They are often only 
moderately depressed and are smooth or ornamented with 
umbilical bullae alone (Fig. 34). 
The adult body-chamber makes up between two-thirds and 
three-quarters of the final whorl. It may be smooth but generally © 
shows an irregularly developed ornament of coarse, rounded 
fold-like to denser, sharper, narrow crease-like ribbing on the 
venter and outer flanks. Meister (1989: 18) pointed out that the 
body-chamber becomes constricted but the adult aperture itself 
is flared (Fig. 35). This modification occurs at diameters between 
73 mm and 110 mm. There is no clear evidence of size 
dimorphism, however; other individuals showing a flared 
aperture do so at diameters of 80, 82, 82, 85, 85, 85, 86, 88, 95, 
97, 98, 100 and 104 mm. Cobban & Hook (1983) described a 
large population sample of Neoptychites cephalotus (Courtiller) 
from New Mexico which shows similar adult body-chamber 
modifications. They too found that adult sizes were highly 
variable with no discernible bimodal pattern. 
Paravascoceras crassus var. bullata Schneegans (1943: 131, pl. 
8, figs 3, 4) has depressed whorls and ribbing of a closely similar 
style to that in the present material. Its umbilicus, representing 
about 25% of the overall diameter, is narrower than the average 
in the Nigerian forms described here but in this respect there is 
an overlap with the more involute individuals (see Fig. 12). 
Schneegans (1943) regarded his material as a variety of 
Vascoceras ( Pachyvascoceras ) crassus Furon (1935: 58, pl. 3, figs 
2a, b; text-fig. 17), a slightly less depressed and less evolute form. 
V. (P.) crassum shows only a very weak ornament of fine riblets 
though its suture pattern is close to that in the present material. 
As mentioned above, V. (P.) crassum may be most properly 
referred to Paravascoceras. In view of the clear similarities 
between the present material and Pachyvascoceras crassum vat. 
bullatum, however, the name Vascoceras bullatum Schneegans is | 
applied to it. The Nigerian material is distinct from coeval 
Paravascoceras cauvini and is therefore referred to Vascoceras 
rather than Paravascoceras, although with some uncertainty. 
Paravascoceras costatum multicostatum Barber (1960: 60, pl. 
13, fig. 3; pl. 14, figs 1, 2) combines the relatively open umbilicus 
Figs 38-40 Vascoceras globosum costatum (Reyment). Pindiga Formation, unit O, Ashaka. Fig. 38a, b, C.93527, x1. Fig. 39a, b, C.93536b, x1. Fig. 
40a, b, C.93536c, x1. 
Figs 41-44 Thomasites gongilensis (Woods). Pindiga Formation, unit O, Ashaka. Fig. 41, C.93582, x1. Fig. 42, C.93579, x1. Fig. 43, C.93580, x1. 
Fig. 44a, b, C.93583, x1. 
Figs 45-47 Vascoceras globosum proprium (Reyment). Pindiga Formation, unit T2, Ashaka. Fig. 45a, b, C.93548, x1. Fig. 46a, b, C.93551, x1. Fig. 
47a, b, C.93547, x1. 
