Late Cretaceous ammonites from the Bou Angueur syncline (Middle ...

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0 cc u r re n c e: In central Tunisia Vascoceras durandi occurs in the Pseudaspidoceras flexuosum Zone and Thomasites rollandi Zone of
the early Turonian, with a maximum in the lower part of the latter. It also occurs in Algeria, Israel, Porrugal (e. g. CHANCELLOR et al. 1 994;
MEISTER & ABDALLAH 2005). It is recorded here from Morocco for the first time.
Vascoceras cauvini CHUDEAU, 1909
(Plate 2, figs. A-B, M-N)
1909 Vascoceras cauvini - CHUDEAU, Plate 1, figs. 1-2; Plate 2, figs. 3, 5; Plate 3, figs. 1, 4.
1996 Paravascoceras cauvini (CHUDEAU) - ZABORSKI, p. 65; figs. 2-8 (for full synonymy).
2002 Vascoceras cauvini CHUDEAU - EL-HEDENY, p. 406; text-figs. 4b-c, 7f.
2004 Vascoceras cauvini CHUDEAU - ABDEL-GAWAD et al., Plate 4, figs. 2, 3, 5.
2006 Vascoceras cauvini CHUDEAU - EL QoT, p. 117; Plate 25, figs. 2, 3, 5.
Material: GSUB C2566 and C2571
Description: GSUB C2566 and GSUB C2571 are distorted specimens with a total diameter of 103 and 105
mm. The inner whorls show smooth flanks at the transition from the penultimate to the ultimate whorl (to some
extent freshly revealed in GSUB C2571 and C2566). The final half of the last whorl shows prominent radial
ribbing, long and short alternating in GSUB C2571, on the outer half of the flank. There are about 12 ribs per
half a whorl that cross the venter in a straight line, either slightly less prominent (GSUB C2566) or with the same
strength (GSUB C2571). The inner flanks are smooth, except for a rib at 46 mm whorl height in GSUB C2571
that stems from a bulla close to the umbilical edge. The whorl section is compressed and subrectangular (Text-fig.
7 D; wb/wh ratio 1.09; GSUB C2571 is obliquely distorted). There is an almost angular cross section with
subparallel flanks at the ribs and at the transition from the flank to the ventrolateral shoulder. The section
between ribs is more rounded.
Discussion: Our specimens of Vascoceras are characterised by strong ribbing on the venter, ventrolateral
shoulder and on the uppermost flank, falling within the variability of Vascoceras cauvini sensu MEISTER et al.
(1992). They differ from the material figured by MEISTER et al. (1992) from Niger, however, by a more distant
ribbing that appears more robust. In this aspect our material resembles the strong and robust ornamentation of
Vascoceras figured as Paravascoceras chevalieri (FuRON 1935) by ScHNEEGANS (1943: Plate 4, fig. 7). This type of
ornament is slightly more prominent than in other strongly ornamented specimens of the genus (e. g. Vascoceras
cauvini var. evoluta in SCHNEEGANS 1943: Plate 8, fig. 2; Paravascoceras cauvini in FREUND & RAAB 1969: Plate 3,
figs. 1-3 and in 2ABORSKI 1996: fig. 3; V. obscurum BARBER in 2ABORSKI 1996: figs. 61, 62; V. rumeaui COLLIGNON
in FREUND & RAAB 1969: figs. 4-5 and LuGER & GROSCHKE 1989: Plate 41, figs. 5-6). Strong ribbing as in V. (P.)
chevalieri occurs, however, in the type material of Vascoceras cauvini CHUDEAU, 1909, and more prominently in
specimens subsequently referred to this species (FuRON 1935: Plate 4, fig. 3; Plate 5, fig. la & b). Consequently, we
follow MEISTER et al. (1992) in regarding Vascoceras (Paracanthoceras) chevalieri FuRoN, 1935, as a synonym of a
morphologically variable Vascoceras cauvini CHUDEAU, 1909, based on excellent material. We can support this
particularly by GSUB C2566, that clearly differs from V. (P.) chevalieri by the continously strong ribbing in
contrast to the irregular stronger and less stronger ribs on the phragmocone of the holotype of FuRON (1935, at
wh