Pteroparia ziegleri maroccanica, Feist, 2002

Feist, Raimund, 2002, Trilobites from the latest Frasnian Kellwasser Crisis in North Africa (Mrirt, central Moroccan Meseta), Acta Palaeontologica Polonica 47 (2), pp. 203-210 : 206

Pteroparia ziegleri maroccanica subsp. nov.

Fig. 3L–P .

Derivation of name: After Morocco.

Holotype: Cranidium UM2 − RF 252, fig. 3L, M, Q.

Type locality: Section 1, lower trilobite association at Bou Ounabdou (section II in Lazreq 1992), north of track, Sof Al Gara hill (see location map Fig. 1C ).

Type horizon: Grey−beige limestone bed immediately above prominent dark grey Lower Kellwasser bed.

Age: According to Lazreq (1992): Late Palmatolepis rhenana Zone.

Material.— Figured specimens: 1 cranidium ( UM2 − RF 252), 1 librigena ( UM2 − RF 253), 1 pygidium ( UM2 − RF 254); additional material all from type locality: 3 cranidia ( UM2 − RF 255–257), 1 pygidium ( UM2 − RF 258) .

Diagnosis.—Anterior outline of glabella semicircular; fixigenae without ocular ridges or swellings. Librigena with rather broad, stout genal spine. Axis of pygidium narrower than pleural field; postaxial area shorter than half length of axis.

Comparison.—The Moroccan material is very near to Pteroparia ziegleri from Sessacker in the general outline and vault of the cephalon, the presence of a small, flat ocular field with lenses and the dense granulation of the exoskeleton. There are a few morphological differences that distinguish the new material that is considered here as a contemporaneous geographic subspecies of P. ziegleri . The most important feature is the absence of ocular ridges on the fixigenae opposite to the eye: this area remains virtually flush with the general curvature of the anterior enlarged fixigenal field whereas, in the nominate subspecies, it is differentiated from the latter by the swollen palpebral area. Though subject to considerable variation, the anterior outline of the glabella is broader in P. ziegleri maroccanica : it is semicircular with a slight incurvature of the antero−lateral dorsal furrows. By contrast, in the nominate subspecies, the front of the glabella is more conical with straight diverging dorsal furrows. In P. ziegleri maroccanica the pygidial axis is narrower; however, the dimensional relations between axis and pleural field varies with ontogenetic growth and additional material of various growth stages must be recovered in order to confirm whether the two subspecies differ in this feature.

Figures

Fig. 3. A–I. Acuticryphops acuticeps (Kayser, 1889). A, H, I. Cephalon from section “2”, upper trilobite association, UM2−RF 220, partially external mould, in dorsal view (A), × 6.9; in lateral view (H), eye lobe with more than 6 lenses, × 6.5; in frontal view (I), slightly tilted backward showing vincular furrow and ventral doublure, × 7.1. B, C. Cephalon from section “1”, upper trilobite association, UM2−RF 221, external mould; in lateral view (B), eye lobe with 4 lenses, × 7.8; in dorsal view (C), × 8.2. D–F. Pygidium from section “2”, upper trilobite association, UM2−RF 222, external mould; lateral view (D), × 14.5; in poste− rior view (E), × 10.7; in dorsal view (F), × 12.2. J–K. Otarion stigmatophthalmus (Richter, 1914), cranidium from section „2“, upper trilobite association, UM2−RF 248, internal mould in dorsal view (J), × 14.1; in lateral view (K), × 14.8. L–Q. Pteroparia ziegleri maroccanica subsp. nov.from section “1”, lower +

Fig. 1. A. Devonian outcrops in Morocco with location of the Mrirt area in the central Meseta east of Rabat. B. Measured section “1” showing the Lower (LKW) and Upper (UKW) Kellwasser horizons and the intervening limestone beds. The levels of the lower and upper trilobite associations are marked with a star. C. Location of the studied sections “1” and “2” at Bou Ounabdou, 4 km to the SE of Mrirt township (after Becker and House 1999 and Walliser et al. 1999). Section “1” is the same as Bou Ounabdou, section II of Lasreq (1992).