Bull. nat. Hist. Mus. Lond. (Geol.)52(1): 61-89 Issued 27 June 1996 
The Upper Cretaceous ammonite Vascoceras 
Choffat, 1898 in north-eastern Nigeria 
P.M.P. ZABORSKI 
Department of Geology and Mining, University of Jos, P M.B. 2084, Jos, Nigeria 
CONTENTS 
Introd UC On mmew ss Sete. cece hie: Mon bee ante Rages os) idea Sd OL OD See et tee 
SV Stehlatic descnptlonspeeis-e-sees ee eee eee 
Family Acanthoceratidae Grossouvre ............. 
Subfamily Acanthoceratinae Grossouvre .... 
Genus Paravascoceras Furon. ............20000020+ 
Paravascoceras cauvini(Chudeau)_ ........... 
(CEIUIS JANA DNERATRAIES IMSINON'E cosncocceseeqacncocncconasee see sc0ce caccceecevoconcceakeouseecnoosconeeboreoceoonen: 
Pseudovascoceras nigeriense (Woods) 
RamilvavascoccratidaciD ouvillevenss..tusteee set. ets, .aciesiobc donates Saas SOE SP en peo: RE ot ole oe 
Subfamily Vascoceratinae Douvillé 
Gonusmyascocerasl @lio tit tae memento nce ccc cre, Rea eee eae oe ER RO ic Ee 
Vas GOGEN ASV OOASIS DMIOW Maree cere tree eeen cee ore scan 2 soe Reyer te ere oe RN 72 
Vascoceras bullatum Schneegans 
Vascoceras globosum (Reyment) 
Vascoceras globosum costatum (Reyment) 
Vascoceras globosum globosum (Reyment) 
Vascoceras globosum proprium (Reyment) 
Vascoceras obscurum Barber 
VOScOcerasiiaricii (Gay Att ieee trace anette ne Mecca ae occa econ wks cose Ge nade ore en nen 
Stratigraphical and phylogenetic discussion 
Acknowledgements 
INGTSRSNEES socrsscosaeeoonsc 
Appendix 
Synopsis. Large collections of ammonites that have been referred at one time or another to Vascoceras Choffat, can be 
made under tight stratigraphical control in north-eastern Nigeria. The following forms are present, in order of 
stratigraphical appearance: Paravascoceras cauvini (Chudeau); Vascoceras woodsi sp. nov.; V. bullatum Schneegans, V. 
globosum costatum (Reyment), V. globosum globosum (Reyment) and Pseudovascoceras nigeriense (Woods); V. globosum 
proprium (Reyment); V. obscurum Barber; and V. harttii (Hyatt). Only the last three occur in the Lower Turonian; the 
remainder are restricted to the Upper Cenomanian, the earliest appearing above the level of the European Metoicoceras 
geslinianum Zone. 
Paravascoceras Furon (type species Vascoceras cauvini Chudeau) is retained as a separate genus for forms derived from 
Nigericeras Schneegans. Pseudovascoceras gen. nov. (type species Vascoceras nigeriense Woods) is proposed for ribbed and 
multituberculated forms thought to have arisen from Cunningtoniceras Collignon. Paravascoceras and Pseudovascoceras 
are most properly referred to the subfamily Acanthoceratinae since they have an origin separate from that of Vascoceras. 
Several of the taxa present show a high degree of individual variation. Palaeoecological factors played an important 
role in their geographical distribution and probably also in their potential for polymorphism. Separate lineages converged 
on a ‘Vascoceras morphology’ in north-eastern Nigeria as a response to the particular environmental conditions 
prevailing there during Late Cenomanian and Early Turonian times. 
Its ammonites have been described by Woods (1911), Reyment 
INTRODUCTION 
In Tethyan regions ammonites referred to the genus Vascoceras 
Choffat, 1898, are often present in large numbers in the Upper 
\Cenomanian and Lower Turonian. The upper Benue Trough 
a in north-eastern Nigeria is a classic region for such faunas. 
© The Natural History Museum, 1996 
(19546), Barber (1957, 1960), Meister (1989), Zaborski (1990a, 
1993, 1995) and Courville (1992). Species of Vascoceras have 
been widely employed in biostratigraphical analysis in Nigeria 
but the taxonomic treatment applied to them has varied widely 
from author to author. The north-eastern Nigerian faunas are of 
particular interest since large collections can be made under 
