Monodechenella breviceps ( Mitchell 1918 )

Vanderlaan, Tegan A. & Ebach, Malte C., 2015, A review of the Carboniferous and Permian trilobites of Australia, Zootaxa 3926 (1), pp. 1-56 : 19-20

Monodechenella breviceps ( Mitchell 1918)

Figs.. 4.7–4.9

1892a Phillipsia sp. indet.(b); Etheridge Jr., p. 129, pl. 22, fig. 14. 1918 Phillipsia dungogensis Mitchell ; p. 474, pl. 47, figs. 6–7.

1918 Phillipsia breviceps Mitchell ; p. 449, pl. 46, figs. 11–12, pl. 51, figs. 2–3. 1963 Conophillipisa brevicaudata Roberts; p. 25, pl. 6, figs. 13–20. 1965 P. cf. Phillipsia dungogensis ; Roberts, p. 56.

1965 Conophillipsia brevicaudata; Roberts, p. 57.

1967 Conophillipsia brevicaudata; Hahn & Hahn, p. 327, text-fig. 2e. 1969 Proetus (Pudoproetus) breviceps ; Hahn & Hahn, p. 60.

1970 Conophillipsia brevicaudata; Osmólska, p. 26, tab. 1.

1972 Phillipsia ? ( Phillipsia ?) dungogensis ; Hahn & Hahn, p. 392. 1972 Conophillipsia brevicaudata; Hahn & Hahn, p. 382.

1984 Conophillipsia breviceps breviceps Engel & Morris; p. 31–35, figs. 4–5. 1984 Conophillipsia breviceps dungogensis Engel & Morris; p. 35–36, figs. 6–7. 1994 Monodechenella breviceps ; Lieberman, p. 141–143.

Lectotype. AMF28383 (part external mould of cranidium).

Paralectotype material. Unknown locality: AMF28371 (internal pygidium). From NU L372: AMF35851a/b (external/internal pygidium).

Locality. Type—unknown. Others—NU L372.

Emended diagnosis. Cephalon flat with a semicircular outline; glabella tapers anteriorly; S1 very distinct, S2 faint. Anterior border concave, glabella just touches border furrow; genal spines short. Pygidial border concave; 11+ pleural ribs, 12+ axial rings.

Remarks. Engel & Morris (1984) separated Monodechenella breviceps into two sub-species based on the larger number of ribs and rings in M. breviceps dungogensis . However, there are few preserved cranidial features for this second sub-species, and the pygidia are almost identical. It is also apparent that not all rings in many of the M. breviceps breviceps specimens are preserved, so they may in fact consist of more. The specimens identified as M. breviceps dungogensis have therefore been synonymised with M. breviceps breviceps , removing the need for subspecies names. The pygidial axial ring and rib pair counts in the emended diagnosis has been changed to reflect this.