Ordovician (Whiterock) calymenid and encrinurid trilobites from the Precordillera of Argentina

Journal of Paleontology, Jul 1998 by Edgecombe, Gregory D, Chatterton, Brian D E, Waisfeld, Beatriz G, Vaccari, Norberto E

The large degree of ambiguity in the present results (Fig. 5) indicates that some of the phylogenetic conclusions and taxonomic revisions of Lesperance and Desbiens (1995) require additional character support if they are to be upheld. The monophyly of Walencrinuroides and Frencrinuroides is ambiguous. Both genera were supported basally by a single synapomorphy in the Lesperance and Desbiens analysis, this being a homoplastic character in the case of Frencrinuroides. A core group of F. capitonis, F. edseli, and F. torulatus is present in a majority (67 percent) of, but not all, shortest cladograms, and is resolved in the Adams consensus tree. Also ambiguous is the proposal that Prophysemataspis (the clade of neuter and uncatus) is especially closely related to Physemataspis (here restricted to the clade of insularis and coopi). With the addition of new characters, Prophysemataspis is more closely related to lapworthi (here removed from Walencrinuroides) and Erratencrinurus than to Physemataspis.

FRENCRINUROIDES EDSELI new species Figures 6, 7.1-7.21, 8.1, 9, 10.1-10.10

Diagnosis.-labella densely covered with moderate sized tubercles; L1 strongly subdued abaxially; eye ridge absent; genal spine moderately long, fairly stout, directed outwards at about 40 degrees from exsagittal line; posterior fixigenal spine strongly divergent in juvenile growth stages; torulus weakly inflated; hypostome bearing two pairs of denticulations on posterolateral margin; 62 pygidial pleural ribs.

Description.-Glabellar length and width approximately equal; axial furrow narrow, deep, nearly bridged by L2-L4 lateral lobes in some specimens; glabella moderately convex (sag., tr.); longitudinal median glabellar furrow of moderate length and depth, barely discernible in dorsal orientation due to steep inclination of anterior part of frontal lobe; glabellar tubercles densely arranged mix of small and moderate size, symmetrical arrangement obscure; SI directed posteromedially, merging with SO, Li short (exsag.), depressed ridge; anterior margin of SO ranging from gently convex forward to weakly concave; S 1 apodeme large, SO and S2 slightly smaller, S3 apodeme lacking; LO slightly shortened medially, bearing a row of coarse granules along its anterior edge, lacking tubercles in mature growth stages; preglabellar furrow narrow, deep, without significant shallowing medially; anterior cranidial border strongly narrowing medially in dorsal orientation, bearing a few very weak tubercles most distinct abaxially; palpebral lobe moderately large, midlength opposite posterior part of L2; fixigenal field densely tuberculate, including a few irregularly displaced tubercles against axial furrow; fixigenal field equal in length (exsag.) to posterior border immediately behind eye; posterior border furrow short, deep; border strongly lengthening distal to fulcrum, generally lacking tubercles except for large, low swelling near base of genal spine; full length of genal spine not known in largest specimens, but moderately long, evenly stout, with distal part curved inwards in moderate sized holaspides.