Monodechenella subtriangularis ( Engel & Morris 1984 )

Vanderlaan, Tegan A. & Ebach, Malte C., 2015, A review of the Carboniferous and Permian trilobites of Australia, Zootaxa 3926 (1), pp. 1-56 : 20-21

Monodechenella subtriangularis ( Engel & Morris 1984)

1847 Phillipsia cf. gemmulifera McCoy, p. 231.

1984 Conophillipsia subtriangularis Engel & Morris; p. 39–41, figs. 10–11.

Holotype. AMF80518 (internal mould of cranidium).

Paratype material. From NU L353: AMF80519 (internal pygidium), AMF80520 (external pygidium), AMF80522 (external pygidium). From MUM: AMF80521 (internal pygidium). From DV: CSMF 10586a/b (internal/external pygidium).

Locality. Type—NU L353. Others—DV, MUM.

Emended diagnosis. Glabella tapers anteriorly; slightly incised at γ; S1 very distinct, S2 less distinct; strongly convex. Pygidium triangular in outline; concave pygidial border; 12+ pleural ribs; 14+ axial rings.

Remarks. There are few specimens of Monodechenella subtriangularis available for study, but they seem to closely resemble M. speciosa . Some of the distinguishing features between the two species noted by Engel & Morris (1984) appear to be dubious. For instance, there are a greater number of pygidiual rings and ribs in M. subtriangularis . The other distinguishing characters between M. subtriangularis and M. speciosa seem more obvious, that is the densely nodose ornament of M. speciosa , the different convexities of the pygidial borders and the more convex axis of the glabella in M. subtriangularis . We consider these differences sufficient to warrant the separation of these species.