Wolfartaspis Cooper, 1982

Carvalho, Maria Da Gloria Pires De, Edgecombe, Gregory D. & Smith, Legrand, 2003, New Calmoniid Trilobites (Phacopina: Acastoidea) from the Devonian of Bolivia, American Museum Novitates 3407, pp. 1-18 : 9-13

Wolfartaspis Cooper, 1982

TYPE SPECIES: Metacryphaeus cornutus Wolfart, 1968 , from the lower part of the Upper Member of the Belén Formation (late Emsian), La Paz Department, Bolivia .

Wolfartaspis liebermani , new species

Figures 4A–F, 5A–F

DERIVATION OF NAME: For Bruce S. Lieberman, who has made valuable contributions to systematics and biogeography of calmoniid trilobites.

DIAGNOSIS: Cephalic anterior border weakly pointed medially; ventral view of cephalon triangular in outline. Eyes less than one­third glabella length (Large Eye Index 31%); vi­ sual surface with 25–26 dorsoventral files with a maximum of 10 lenses per file. Occipital ring strongly arched in cross section, wide medially, with pronounced convex anterior margin and robust median spine tapering dorsally.

TYPES: Holotype: MHNC 8132 , external mold of an incomplete cephalon, Icla Formation , equivalent to basal part of Upper Member at Icla type locality (see Discussion below), Kochis Hills (approximately 3 km north of the Rio Grande, on the border between Chuquisaca and Cochabamba Departments), Bolivia . Paratypes: AMNH 47148 , internal mold of thorax and pygidium ; AMNH 47149 , internal mold of a cephalon ; AMNH 47150 , external mold of pygidium ; AMNH 47151 , external mold of an incomplete pygidium ; AMNH 47401 , hypostome in situ beneath cephalon ; AMNH 47403 , internal mold of almost complete cephalon ; MHNC 12749 , internal mold of incomplete pygidium. All type specimens are from the Icla Formation , Kochis, Cochabamba Department .

OTHER MATERIAL: Some additional topotype specimens collected within the same stratigraphic interval as the types are referred to Wolfartaspis liebermani , but they are not well preserved. Most are from broken concretions and include three internal molds and two external molds of pygidia, an internal mold of four or five thoracic segments, an external mold of some pleurae, and two internal molds of cephala. In addition, however, there is a single, well­preserved, small pygidium in part and counterpart. This additional material is housed in the MHNC collection.

DESCRIPTION: The cranidial length (sag.) is about 29.7 mm in AMNH 47403. The anterior cephalic border is narrowest medially, where the upturned doublure nearly contacts the cranidial margin; the anterior cephalic border projects only slightly in front to the glabella medially in dorsal view; the anterior border gently widens abaxially, but remains narrow (exsag.) in dorsal view, and is steep along its entire width. The cephalic anterolateral margin is nearly straight in dorsal view and is rounded medially. The axial furrow is deep, wide, straight, slightly divergent forward. Glabellar length (sag., excluding S0) in AMNH 47403 is 23.4 mm, with the frontal lobe having marked independent convexity from the posterior glabellar region, which has a flat sagittal profile. The frontal glabellar lobe is inflated, about 60% of glabellar length, and gradually expands anteriorly and laterally, with its anteromedian margin rounded. The anterior section of the facial suture circumscribes but does not transect the frontal glabellar lobe. The frontal lobe has a well­ developed circular to slightly elongated posterior median impression (PMI) and auxiliary impression system (AIS) of muscle scars. The latter is most clearly preserved on the left side and the median part of AMNH 47403 (fig. 5A) as small rounded pits on the internal mold, forming divergent rows. Medially, the AIS does not seem to have a defined pattern. The lateral glabellar furrows are well developed. S3 is wide, deep, oblique, straight, with its proximal part weakly bent posteromedially, lengthening abaxially, and distinctly confluent with the axial furrow. S2 is transverse, narrower and shallower than S1 and S3; it becomes abruptly shallow distally and has only faint impression against the axial furrow on the external cuticular surface (fig. 4A). S1 is deeper than S2 and S3; it sharply narrows distally but is distinctly confluent with the axial furrow on the external mold; the posterior margin of S1 is concave. L3 is wedge­shaped; L2 is approximately trapezoidal; L1 is slightly shorter (exsag.) than L2 and L3, with its posterior margin markedly convex backward and then continuing inward, forming a short (sag.) transglabellar lobe that is weakly curved anteriorly; this feature makes the glabella slightly higher at L1 than at L3. S0 is long and relatively shallow (sag.), becoming shorter and deeper as it approaches the axial furrow. Where the cephalic posterior furrow meets S0, both have approximately the same width; the posterior furrow becomes wider (exsag.) toward the fulcrum, and is then gently flexed forward and shallows distally. L0 is strongly arched in its transverse section, wide medially, with a pronounced convex anterior margin, and bearing a robust median spine that tapers dorsally; the median spine is weakly declined posteriorly. The eye is high, less than one­third glabellar length (Large Eye Index 31%). Its anterior edge is opposite the anterolateral corner of L3, and its posterior edge is opposite the posterolateral margin of L2 and at a considerable distance from the posterior cephalic border furrow (approximately 4 mm in the holotype). In anterior view, the visual surface is straight from top to bottom, gradually becoming wid­ er toward its base, with 25–26 dorsoventral lens files, and a maximum of 10 lenses per file. The interocular fixigena slopes upward as it approaches the narrow, C­shaped pal­ pebral lobe; the palpebral furrow is moderately deep. The lateral cephalic border furrow is faint. The posterior cephalic border is narrow proximally, about equal in width (exsag.) to the posterior border furrow at the fulcrum, and widened distally; none of the available specimens preserves the genal angle.

The hypostome is preserved in situ beneath the cephalon in one specimen (fig. 4F). Its anterior margin is largely missing, but its course against the moderately wide anterior wings suggests a transverse hypostomal suture. The middle body is roughly circular and gently convex (tr., sag.). The maculae are strong, forming a pair of ovoid protuberances positioned abaxially, near to the junction of the faint middle furrow and the lateral border furrow, anterior to the midlength of the middle body. The border furrow is obscure anterolaterally (against the wings), becoming moderately impressed at the macula, maintaining moderate depth and width posterolaterally and posteromedially. The lateral bor­ der is narrow, with the lateral margins gently converging between the anterior wing and first of two pairs of short, sharp posterolateral marginal spines; the inner pair of spines (on posterior border) is separated by slightly greater than the distance between the two spine pairs. The posterior border is fairly long and gently convex (sag.); the posteromedian margin is faintly convex backward between the inner pair of marginal spines.

The thorax consists of 11 segments. The relative width of the axial rings and thorax cannot be determined, as the distal ends of the pleurae are not preserved in any specimens, but in AMNH 47148 (fig. 4D) the axial rings appear to be wider than the pleural fields. The axial furrow is shallow and narrow, weakly diverging back to the sixth ring, then gently converging. In lateral view, the axial rings are faintly convex, raised well above the pleurae. The anteriormost axial rings are spatulate distally, but this is less marked in the more posterior rings. Small but distinct apodemal pits lie between the axial rings abaxially. The pleural furrows are narrow and moderately impressed adjacent to the axial furrow, becoming wider distally, with a straight, oblique course across the rib; the anterior margin of the pleural furrows is gently convex anteriorly, while the posterior margin of the furrows is straight.

The pygidium is triangular, moderately arched in lateral view, wider than long, with a pointed posterior tip. The axial furrow is narrow and moderately deep. The axis is slightly waisted, the axial furrow moderately convergent against the first five axial rings, weakly converging posterior to this; the axial terminus is blunt, lacking impression of the axial furrow, lying well in advance of the pygidial posterior margin. There are 10–11 axial rings, but the last few are indistinct; the first five rings are gently arched anteriorly, but the subsequent ones are transverse or weakly bowed backward. The axial rings are separated by wide ring furrows that become progressively narrower posteriorly; the first five ring furrows have narrow, groovelike apodemal pits distally. The pleural field includes six pairs of strongly furrowed ribs plus a small seventh pair that parallels the axis. The pleural furrows are deep and wide, though gradually narrowing on more posterior segments; they are moderately curved. The interpleural furrows are narrow, moderately deep proximal to the fulcrum between the anterior few ribs, progressively shallow between more posterior ribs such that fifth interpleural furrow is last distinct one on external mold. The lateral margin of the pygidium is not well preserved in any of the material (fig.4E); the fifth lappet is small, flat, and wide (fig.4B), with a curved anterior margin and straight posterior margin. The posteromedian margin of the pygidium is an elongate, tapering, upturned spine (its basal part is preserved in AMNH 47150; fig. 4B, C).

DISCUSSION: The monotypic Wolfartaspis was erected by Cooper (1982) as a subgenus of Metacryphaeus , but recent usage ( Lieberman, 1993) recognizes it at the generic rank. According to Lieberman, Wolfartaspis differs from Metacryphaeus in having an enlarged occipital spine and an upwardly curved pygidial spine. The material described here includes both of these features, and it is therefore assigned to the genus Wolfartaspis . We place our material in a new species, based on the following differences from W. cornutus : (1) the ventral view of the cephalon has a rounded shape in W. cornutus , but is more pointed in our form; (2) the Large Eye Index in W. cornutus is 34%, but is less in our material (31%); (3) the occipital spine in W. cornutus ( Lieberman, 1993: fig. 2.8) is stouter than in our material (fig. 5E, F) and does not taper from its base. Differences are also noted in the stratigraphic levels of the two forms. Wolfartaspis cornutus occurs in the basal part of the Upper Member of the Belén Formation, in strata overlying the layer of Francovichia branisi (= layer of Odontochile branisi sensu Wolfart, 1968 , in the upper part of Lower Member of Belén Formation). At Kochis, Francovichia occurs stratigraphically above the beds with Wolfartaspis liebermani .