84 
Fig. 60 Vascoceras harttii (Hyatt). Pindiga Formation, unit X, Ashaka. C.93555, x1. 
Figs 61,62 Vascoceras obscurum Barber. Fig. 61a, b, Pindiga Formation, unit X, Ashaka. C.93326, x1. Fig. 62a, b, Pindiga Formation, unit T2, 
Ashaka. C.93909, x1. 
Figs 63,64 Vascoceras globosum proprium (Reyment). Pindiga Formation, unit T2, Ashaka. Fig. 63a, b, C.93904, x1. Fig. 64a—-c, C.93905, x1. 
lack equivalents in south-western New Mexico. Unit O at 
Ashaka, which contains the youngest Paravascoceras cauvini, 
Pseudovascoceras nigeriense, Vascoceras bullatum, V. globosum 
costatum and V. globosum globosum is probably at least partially 
equivalent to beds with Nigericeras scotti in south-eastern 
Colorado. 
Unit T2 at Ashaka contains an ammonite assemblage 
including Pseudaspidoceras flexuosum and Vascoceras globosum 
proprium. These forms occur together in the basal Turonian 
Flexuosum Zone in west Texas (Kennedy et al. 1987), 
Thomasites and Wrightoceras munieri (Pervinquiére) also being 
associated in both places. V. globosum proprium is further 
recorded from New Mexico and Hancock (1991) suggested that 
it may serve as a better marker for the base of the Turonian than 
Pseudaspidoceras flexuosum. In the Ashaka section, however, it 
actually appears in unit T1 just below the first occurrence of P 
flexuosum. A minor discontinuity representing a marine 
P.M.P. ZABORSKI 
flooding surface separates units T1 and T2. The fauna of unit T2— 
seems to have in large part been introduced during this flooding 
event which may complicate the order of occurrence of these 
taxa at Ashaka. 
Vascoceras obscurum ranges from the basal Turonian unit T2 
into unit X at Ashaka. Units U to X at Ashaka, which also 
represent the known range of V. harttii, are of Early Turonian 
age. They cannot, however, be dated more precisely on the basis” 
of their ammonite faunas which are almost entirely composed 
of Pseudotissotia nigeriensis (Woods) and Eotissotia simplex 
Barber. V. harttii has been assigned to the Lower Turonian in 
Angola (Howarth 1985), Brazil (Bengtson 1983) and Mexico 
(Chancellor 1982) but material from the Upper Cenomanian of 
New Mexico has also been referred to the species (Cobban et al. 
1989: 49, figs 49, 91A—D, G—K). 
With the exception of a few taxa ‘vascoceratid’ ammonites | 
have not proved to be of great value in detailed correlation, 
