Pseudoolenoides dilectus Hintze, 1953

Adrain, Jonathan M. & Karim, Talia S., 2012, 3467, Zootaxa 3467, pp. 1-97 : 22-23

Pseudoolenoides dilectus Hintze, 1953

Plate 11

1951 “ Symphysurus ? goldfussi " Walcott; Ross, p. 64, pl. 15, figs 16–18.

1953 Pseudoolenoides dilectus Hintze , p. 228, pl. 27, figs 1–6.

1973b Pseudoolenoides dilectus Hintze ; Hintze, text-fig. 28.

1974 Pseudoolenoides dilectus Hintze ; Shaw, p. 22.

1991 Pseudoolenoides dilectus Hintze ; Ross and Ethington, p. 160.

1991 Pseudoolenoides dilectus Hintze ; Church, fig. 2.

1996 Pseudoolenoides dilectus Hintze ; Fortey and Droser, p. 87.

2003 Pseudoolenoides dilectus Hintze ; Jell and Adrain, p. 434.

Material. Holotype, AMNH-FI 26492 (Plate 11), from Section J, Locality J-22 of Hintze (1951, 1953), and paratypes AMNH-FI 26490, 26491, 26493–26495, from Section K-South 1.5 T m, Kanosh Formation (Dapingian; Pseudoolenoides dilectus Zone ), southern Confusion Range, Ibex area, Millard County, western Utah, USA.

Diagnosis. Faint raised arc of sculpture on librigenal field but not continued across facial suture onto frontal area; glabella with subdued tuberculate sculpture; thorax of nine segments; pygidium incorporating one unreleased thoracic segment, terminal piece showing distinct segmentation; posteromedian spine very short and nearly ventrally directed.

Discussion. In addition to Hintze's (1953) holotype specimen from Section J, he assigned two large cranidia, a hypostome, and two pygidia from Section K-South 1.5T m. While there is no reason to doubt these assignments, we have not encountered the species in our resampling of this horizon. Instead we have found very common P. ludificatus (which Hintze also found in profusion) and P. pogonipensis (which Hintze did not find). We did encounter three pygidia which are similar in morphology to those of P. dilectus , but they seem clearly to represent a different, related species (see Pseudoolenoides cf. dilectus below). It is difficult to explain this discrepancy, as the fauna we retrieved from K-South 1.5T m in all other respects matches that reported by Hintze, and there is no question that we sampled the same bed in the same place. As explained above, however, the bed is not in outcrop but rather represented by small talus lumps strewn in place along strike. Sclerites of P. dilectus must have been restricted to one or a few small lumps removed by Hintze during the original sampling.

Pseudoolenoides dilectus is the oldest species of the derived group, and is retrieved as the basal member of that group by parsimony analysis ( Fig. 3). It retains only a single unreleased thoracic segment in a pygidium that is otherwise quite comparable to that of P. ludificatus . Pseudoolenoides dilectus is distinguished from all of the other species of the derived group in the lack of a raised line across the frontal area, retention of a standard deep and uninterrupted librigenal lateral border furrow, retention of only one versus four or five unreleased pygidial segments, and retention of a pygidial axis of normal, parallel-sided shape, which is fully circumscribed posteriorly and well elevated above the post-axial region. It shares with this derived group a suite of 11 synapomorphies (see Fig. 3 and Table 1) which serve to distinguish it from the plesiomorphic species P. aspinosus , P. pogonipensis , and P. ludificatus .

Ross (1951, pl. 15, figs 16–18) illustrated three cranidia of a species of Pseudoolenoides from two localities in the Swan Peak Formation in southeastern Idaho and northern Utah. As recognized by Hintze (1953, p. 226), these most likely represent P. dilectus , though more material, particularly of other exoskeletal parts, would be required to be certain.