UPPER CRETACEOUS AMMONITE 
_ SYSTEMATIC DESCRIPTIONS 
Repositories. Unless otherwise stated all the specimens referred 
to below are housed in the Department of Palaeontology, The 
Natural History Museum, London, their register numbers being 
prefixed with the letter C. In addition to those specifically listed, 
large numbers of Paravascoceras cauvini, Vascoceras woodsi, V. 
bullatum, V. globosum costatum, V. globosum globosum and 
Pseudovascoceras nigeriense have also been studied. 
Provenance of material. The ammonite-bearing horizons at the 
/ two main localities in north-eastern Nigeria, Ashaka and 
Pindiga, are shown in Fig. 1. A fuller description of these 
sections and lists of their ammonite faunas were given by 
Wozny & Kogbe (1983), Popoff et a/. (1986), Meister (1989) and 
' Courville (1992). The Pindiga section has been described by 
_ Barber (1957), Carter et al. (1963), Wozny & Kogbe (1983) and 
Popoff et al. (1986). The whereabouts of other ammonite 
localities mentioned in the text were shown by Zaborski (1990a: 
fig. 1). 
Dimensions (in mm). D, diameter; Wb, whorl breadth; Wh, 
whorl height; U, umbilical diameter. Figures in parentheses are 
dimensions as a percentage of the total diameter. 
Family ACANTHOCERATIDAE Grossouvre, 1894 
Subfamily ACANTHOCERATINAE Grossouvre, 1894 
| Genus PARAVASCOCERAS Furon, 1935 
Me Pardcanthoceras Furon, 1935; Pachyvascoceras Furon, 1935; 
| Broggiiceras Benavides-Caceres, 1956) 
| 
i 
| 
| Superfamily ACANTHOCERATACEAE Grossouvre, 1894 
TYPE SPECIES. Vascoceras cauvini Chudeau, 1909; by the 
subsequent designation of Reyment, 1955. 
REMARKS. Furon (1935: 60) proposed Paravascoceras as a 
subgenus of Vascoceras and it has subsequently been treated as 
such by, for example, Schneegans (1943), Cooper (1978), 
Howarth (1985) and Meister er al. (1992). Others, for example 
Reyment (1955), Barber (1957), Wright (1957), Freund & Raab 
| (1969), Schobel (1975) and Meister (1989), have regarded it as a 
|distinct genus while recently it has been widely listed as a 
_}synonym of Vascoceras (see, for example, Berthou er al. 1985, 
| Kennedy et al. 1987, Luger & Gréschke 1989, Cobban et al. 
1989). 
| Furon’s original diagnosis of Paravascoceras specified 
non-globular forms characterized by a simple suture pattern 
which was said to distinguish it from Paracanthoceras Furon 
(1935: 59) (type species, by monotypy, Vascoceras 
(Paracanthoceras) chevalieri Furon, 1935). Both these forms 
_ show strong ventral ribbing in their later growth stages. Furon 
included V. (P.) cauvini, V. (P.) cauvini var. semiglabra Furon 
(1935) and V. (P.) chudeaui Furon (1935) in Paravascoceras. The 
last two are here regarded as synonyms of P. cauvini. Schneegans 
(1943: 127-128) showed that sutural differences between 
Paravascoceras and Paracanthoceras were insignificant and 
demonstrated the latter to be a synonym of the former. Indeed, 
V. (Paracanthoceras) chevalieri itself is a synonym of 
Paravascoceras cauvini. Schneegans gave a revised diagnosis of 
Paravascoceras stressing its vascoceratid suture pattern, ovoid to 
globular whorl section, lack of tubercles and possession of 
simple ventral ribs or folds in the adult stages. The absence of 
63 
umbilical tubercles has since been cited as a chief distinguishing 
feature of Paravascoceras (see, for example, Freund & Raab 
1969, Sch6bel 1975, Meister 1989, Meister et al, 1992). Berthou 
et al. (1985), however, regarded the presence or absence of 
umbilical tubercles in Vascoceras as an inadequate basis for 
generic and subgeneric diagnosis, a conclusion accepted by 
Kennedy ef al. (1987) and Cobban et al. (1989). This view is 
supported here. There is great inconsistency in this feature even 
within individual species of Vascoceras. Meister et al. (1992: 70: 
see also below) further showed that P cauvini may itself show 
umbilical tubercles at certain growth stages. 
As pointed out by Schneegans (1943: 127), the juvenile stages 
are often of greater value in taxonomic subdivision of 
Vascoceras than the often highly variable middle and adult 
whorls. Morphological and stratigraphical evidence from 
north-eastern Nigeria indicates that Paravascoceras was derived 
from Nigericeras (type species Nigericeras gignouxi Schneegans, 
1943: 119, pl. 5, figs 10-15 = N gadeni (Chudeau); by the 
subsequent designation of Reyment 1955: 62), an origin 
separate from that of Vascoceras (see below). In recognition of 
this probability Paravascoceras is here treated as a distinct genus. 
In view of its ornament and suture pattern Nigericeras should be 
included in the subfamily Acanthoceratinae (see also Kennedy et 
al. 1989, Cobban et al. 1989, Kennedy & Wright in press). 
Paravascoceras, therefore, cannot be maintained within the 
Vascoceratidae but should be transferred to the 
Acanthoceratinae also. 
There remain problems in providing a reliable and 
unambiguous morphological diagnosis of Paravascoceras. Its 
members are generally compressed, moderately involute, 
without umbilical tubercles and with strong regular ribbing on 
the outer flanks and venter in the later growth stages. The last 
two features are not, however, consistent while certain rather 
depressed forms may belong in the genus. 
Vascoceras (Pachyvascoceras ) Furon (1935: 58) (type species 
Vascoceras ( Pachyvascoceras ) crassus Furon 1935: 58, pl. 3, figs 
2a, b; by the subsequent designation of Reyment 1954b: 257) 
was proposed on the basis of its globular shape, deep narrow 
umbilicus and lack of adult ornament. None of these 
morphological features is sufficient to distinguish 
Pachyvascoceras from Vascoceras. Whorl breadth is often 
particularly variable within individual species of that genus. The 
phylogenetic affinities of V. (P.) crassum, however, may lie with 
Paravascoceras rather than Vascoceras. Meister et al. (1992) 
described topotype material which they regarded as variants of 
Paravascoceras cauvini with which they are transitional (see also 
Schneegans 1943). Pachyvascoceras is accordingly treated here 
as a probable synonym of Paravascoceras (see also below under 
Vascoceras bullatum and V. globosum). 
The genus Broggiiceras Benavides-Caceres (1956: 469-470) 
was proposed for the Peruvian forms B.  olssoni 
Benavides-Caceres (1956: 471, pl. 55, figs 1-4), the type species, 
and B. humboldti Benavides-Caceres (1956: 471, pl. 56, figs 3-6). 
These forms have smooth inner whorls and an adult ornament 
of strong ventral ribs matching that in P. cauvini. B. olssoni has 
whorls a little broader than high. While the opposite condition 
may prevail on the body-chamber of B. humboldti, the two are 
probably synonyms. In the absence of any significant recorded 
differences from Paravascoceras, Broggiiceras is best regarded as 
a synonym. Schébel (1975) and Meister et al. (1992), indeed, 
considered both B. olssoni and B. humboldti as synonyms of P. 
cauvini. 
