Cloacaspis ceryx ( Fortey, 1974 )

Hopkins, Melanie J., 2019, Phylogenetic analysis and revision of the trilobite subfamily Balnibarbiinae (Olenidae), American Museum Novitates 2019 (3928), pp. 1-1 : 1-

Cloacaspis ceryx ( Fortey, 1974)

Figure 4B–F

Balnibarbi ceryx Fortey, 1974: 29 .

HOLOTYPE: Cranidium, SMA 84034 (figured in Fortey, 1974: pl. 8, fig. 1).

TYPE LOCALITY: Profilstranda, Olenidsletta Member, Valhallfonna Formation, Ny Friesland, Spitsbergen, Svalbard.

EMENDED DIAGNOSIS: Cloacaspis species with greater (sag., exsag.) preglabellar length than other species of the genus; anterior border comes to a point on midline. Moderately sized pygidium with three axial rings.

DISCUSSION: Fortey (1974) distinguished Cloacaspis ceryx ceryx and Cloacaspis ceryx anataphra by the latter having a shorter (sag.) preglabellar field relative to the glabella, no visible pits in the anterior border furrow, and a smooth exoskeletal surface. Examination of new and old specimens suggests that the mean preglabellar/glabella ratio is on average shorter in C. ceryx anataphra , but there is overlap in variation in this variable. In addition, while pits are not visible in the anterior border furrow, they are present and visible on the internal mold (fig. 4B, C). On the few specimens where it was possible to estimate the number of anterior pits, the number is slightly smaller (25–30) compared to C. ceryx ceryx (>30). Although granulation is very fine on C. ceryx ceryx and its preservation is very sensitive to any erosion of the surface (fig. 4D–F), it does appear that some specimens truly lack surface granulation. Based on this evidence, the two taxa are retained as subspecies, but the species complex is reassigned to the genus Cloacaspis based on the results of the phylogenetic analysis. The species complex is united with other Cloacaspis species by having advanced genal spines (char. 34), relatively large palpebral lobes (char. 19), and forward curvature of the palpebral lobe (char. 20). However, Cloacaspis ceryx shares some characters with some Balnibarbi species , including greater divergence of the anterior dorsal suture (char. 9), relatively wide palpebral lobes (char. 21), relatively short 3P (char. 25) larger number of axial rings (char. 37), and medial indent on posterior margin of pygidium (char. 44). The latter three characters are also shared with Cloacaspis dejecta .

Figures

FIGURE 4. Cloacaspis spp. A. Cloacaspis ekphymosa Fortey, 1974, USNM 144232. Collected from the Lost River Area on Seward Peninsula, Alaska, and previously identified as Triarthrus sp. (Ross, 1965). Arrow pointing to postpalpebral furrow. B. Anterior border of Cloacaspis ceryx anataphra (Fortey, 1974), AMNH- FI-101655. Black arrows pointing to faint anterior border pits on internal mold. C. Cloacaspis ceryx anataphra (Fortey, 1974), AMNH-FI-101655. Collected from PO-18 of the Olenidsletta Member of the Valhallfonna Formation (Kröger et al., 2017). D) Cloacaspis ceryx ceryx (Fortey, 1974), AMNH-FI-101657. Close-up of E, anterior glabellar lobe and F,posterior wing, showing presence of fine granulation of recently prepared surface (white arrow) and lack of granulation on exposed and slightly eroded surface (black arrow). Collected from bed PO-18 of the Olenidsletta Member of the Valhallfonna Formation (Kröger et al., 2017). Scale bars = 1 mm except A and D, where scale bar = 5 mm.