Glyphopneustes hattaensis
n. sp.
Fig. 3
Material: Six well preserved specimens.
Derivation of name: After the Hatta area where Gebel El Rowdah is
located
Fig.3
Description
of holotype
Shape: Test of medium size, diameter 18.7 mm; low,
height 52 percent of
test diameter; marginal outline rounded; aboral surface slightly
convex; oral
surface almost flat, slightly depressed at peristome.
Apical system: Somewhat large, circular, diameter 33 percent of test
diameter, dicyclic (Fig. 3 D); genital and ocular plates thickened
with knob
slightly rising high above general surface of apical system; suture
depressed
between plates, with deeper pits in corners of plates. Periproct
circular, of
medium size, diameter 10.7 percent of test diameter, almost situated
at center
of systeffi, with slightly elevated rim around it.
Ambulacra: Narrow, greatest width at ambitus, width 13.4 percent of
test
diameter, width of each ambulacrum 30 percent as wide as
interambulacrum;
ambula cral plates trigeminate, with one demipl ate) with primary
tubercle on
every third plate, 16 tubercles in each ambula cral column. Poriferous
zones
narrow, slightly sunken in a furrow; pore pairs in single straight
columns,
slightly arc shaped near peristome; 46- |
|
47 pore pairs
in each zone in a
specimen
18.7 mm in diameter; pores closely spaced and somewhat oblique,
circular,
inner ones slightly larger than outers. Interporiferous zones
relatively wide,
making up 68% ot the ambulacrum.
Interambulacra: Almost 3.4 times as wide as ambulacra, width 45
percent of test diameter, 9-10 plates in each interambulacrum, each
plate
bearing one large primary tubercle. Tubercles crenulate, imperforate: areoles
smooth, not deep; bosses conical; mamelons flattened hemispherical;
scrobicular rings consist of t0-11 small tubercles, rings not
continuous.
Peristome: Circular, slightly sunken, of medium slze, diameter 36.4
percent of test diameter; gill slits well developed, shallow.
Comparison with other species: One species of Glyphopneustes, G.
problematicus (Corrror), has been known from the Cenomanian of Algeria.
This species characteristically has a depressed suture between the
adjacent
areoles in the interambulacral plates. Also, it is distinguished by
the presence
of a spheridial pit placed on the aboral ambula cral plates of each
triad. These
features are absent in the new species. On the other hand, G. hattaensis is
characterrzed by having thickened ocular and genital plates with a
knob rising
slighdy above the surface of the apical system. Deep pits are also
noticed in the
corners of the apical system, and the plates of ambulacra grouped in
triads with
one demiplate.
Occurrence: Late Maestrichtian, Simsima Formation, Gebel El Rowdah,
location (A). |