UTRECHT MICROPALEONTOLOGICAL BUllETINS

Drepanoistodus
inconstans (LINDSTROM), emend. VAN WAMEL, herein
(PI. 3, figs. 11-15)
Paltodus inconstans LINDSTROM, 1955a, p. 583, Pi. 4, figs. 3-8.
Paltodus inconstans LINDSTROM, emend. LINDSTROM, 1971, p. 45, fig. 8.
Oistodus inaequalis LINDSTROM, 1955a, not PANDER 1856. LINDSTROM, 1955a, p. 576, Pi. 3,
figs. 53, 54, 57, not figs. 52, 55, 56.
Dis taco dus peracutus LINDSTROM, 1955a, p. 555, Fig. 5d, not Pi. 3, figs. 1,2.
Remarks: The oistodiform elements (see PI. 3, fig. 11) are very similar to
those of Drepanoistodus inaequalis (PANDER) (see PI. 2, fig. 7). However,
the latter lack the prominently rounded costa at the inner side of the cusp
and the parapet-like extension of the base at this side.
The suberectiform elements of Drepanoistodus inconstans and Drepanoistodus
inaequalis are very much alike as well. The presence of anterolateral
costae on the suberectiform elements of Drepanoistodus inconstans
(see PI. 3, fig. 12) allows differentiation. The suberectiform element of
Drepanoistodus inconstans seems to be identical with the less prominently
costate variant of Distacodus peracutus LINDSTROM, whereas the suberectiform
elements of Drepanoistodus acuminatus are the more prominently
costate variants of Distacodus peracutus LINDSTROM.
The almost symmetrical forms of Paltodus inconstans LINDSTROM have
a carina on one side and a costa on the other, or they carry a costa on every
side (see PI. 3, figs. 13a, b).
There are typical acodiform elements with a costa on one side (see PI. 3,
figs. 15a, b).
Finally there are scandodiform elements which are deflected sidewards and
the basal cavity of which opens to one side (see PI. 3, figs. 14a, b). The
convex outer side can carry up to four costae and the inner side usually has
one.
Regional occurrence: At Kopingsklint this species was found in member
Kk 2. In section 6 and near Horns Udde it was not established with certainty.
Biostratigraphic range: Drepanoistodus inconstans was found from the
Drepanoistodus inconstans Assemblage Zone up to and including the
Triangulodus subtilis/Gothodus microdentatus Assemblage Zone (fig. 15).
Drepanoistodus numarcuatus (LINDSTROM), emend. VAN WAMEL, herein
(PI. 3, figs. 5-10)
Drepanodus numarcuatus LINDSTROM, 1955a, p. 564, Pi. 2, figs. 48, 49; Fig. 31.
Acodus pulcher LINDSTROM, 1955a, p. 546, Pi. 2, fig. 38.
Paroistodus numarcuatus (LINDSTROM) pars, LINDSTROM, 1971, p. 46, fig. 8.