Stoloharpes capricornus, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 98-100

Stoloharpes capricornus n. sp.

Plate 50A–F, K–O

Diagnosis. Cephalon strongly pyriform and vaulted. Glabella with blister-like tubercles, slopes gently anteriorly at <200. Alae with interalar furrow and alar depression. Pits and faint caeca on genal area. Narrow preglabellar furrow, anterior boss barely inflated and not joined to glabella. Brim very broad and sloping steeply anteriorly at 350, increasing to over 470 laterally and becoming near vertical on prolongations. In lateral view, in line with eye lobe, brim makes up half the height of cephalon. Brim width ratio low, at around 0.60, no row of larger perforations at proximal edge.

Etymology. Named for the goat horn shape of the prolongations.

Material and occurrence. Holotype: NHMUK It 29364, Pl. 50A–F , from the “ Thysanopeltis Couche ” at the top of the Eifelian, in an outcrop 21 km east of Touaz ( Fig. 2B, Map 15, site 1), a dorsal exoskeleton of cephalon only . Paratype: NHMUK It 29365, Pl. 50K–O , from type horizon and locality ( Fig. 2B, Map 15, site 2), a dorsal exoskeleton with thorax and pygidium enrolled .

Other material: Stoloharpes aff. capricornus, NHMUK It 29366, Pl. 50G–J , from a up Eifelian horizon, Hamar Laghdad ( Fig. 2B, Map 11, site 14), dorsal exoskeleton of cephalon only.

Description. Cephalon strongly pyriform and vaulted, its height being nearly 60% of sagittal length. Its width (tr.) is 1.22 times length (sag.), and length (exsag.) of prolongation (excluding genal spine) is just over 80% of cephalic length (sag.). Glabella moderately narrow, with width (tr.) just over 60% of length (sag.); flanks tectiform. Large, flat, blister-like tubercles along crest. L1 inflated, and furrows at S1, S2 and S3 are shallow, being discernible by darker colouring of cuticle ( Pl. 50E ). S1 slopes adaxially backwards. S2 and S3 subcircular, barely rising out of axial furrow. Axial furrows convex, taper slightly anteriorly and cross junction of L1 and ala. L1 is inflated, alae small and alar furrows shallow. Interalar furrow and ridge on each ala, and alar depressions also present. Occipital ring slanting posteriorly in lateral view; narrow, broadens at junction with posterior border and inflates as it curves adaxially. Occipital node broad, barely inflated and appearing as swelling reaching back from occipital furrow to near posterior edge of ring. Posterior border very short (tr.), 23% of occipital ring width (tr.). Preglabellar field narrow, length (sag.) being about 12% of width (tr.). Genal area convex and moderately narrow, with width (tr.) 55% of length (exsag.). Eye tubercle at edge of anterior lateral slope of genal area, just above inner margin of fringe and just posterior to preglabellar furrow. Eye location ratio 0.78. Each eye lobe has two lenses ( Pl. 50D ), anterior lens being the largest and almost bean-shaped, posterior one more oval. Eye ridge indistinct but extends into axial furrow. Genal area covered by faint caeca and fine pitting.

Anterior boss barely inflated, not joined to glabella and deflating before reaching girder. Preaxial furrows converge slightly anteriorly. Genal roll convex, broad at sagittal line and sloping anteriorly at about 400. Laterally, it steepens to over 600 and posteriorly, narrows to about two-thirds its width (sag.). Perforations on genal roll are fine and densely-packed, increasing in size as they extend onto prolongations and becoming more spaced out. Intermittent line of bigger perforations at inner margin of fringe, which is particularly noticeable as it crosses anterior boss. Subparallel caeca strands extend down from inner margin of fringe to girder. Caeca also stretch across brim, in places reaching external rim. Girder moderately narrow (sag.), at 2% of width of genicranium, and girder kink very weak.

Brim broad (sag.), being just over 30% of cephalic length (sag.); convex; and sloping anteriorly at an angle of over 350, increasing laterally to over 470 and to near vertical on prolongations. Brim width ratio just over 0.60. Brim perforations densely-packed and slightly coarser than those covering genal roll. On outside edge of brim, row of coarse pits against rim. External rim is fine, its dorsal surface convex and without tubercles. Extension of genal roll and brim on prolongations quickly steepens posteriorly to near vertical. Girder turns gently upwards on prolongations, to meet internal rim nearly halfway down. Row of larger perforations below internal rim. Viewed dorsally, external rim flexes slightly abaxially as it crosses onto prolongation, straightens, and then curves adaxially to meet internal rim, which points obliquely adaxially. Internal rim is angled about 30° to posterior border, pointing obliquely abaxially, and then curves steadily adaxially posteriorly, to join with external rim at end of prolongation. Prolongation terminated by long genal spine, which extends from lower lamella and points adaxially at an angle of about 50° to exsagittal line. Viewed laterally, internal rim declines steadily posteriorly to meet external rim, which is slightly upturned at its distal end. Dorsal surface of internal rim is initially flat but becomes rounded close to junction with external rim. Intermittent row of fine tubercles runs along outside edge of flat surface.

Only one enrolled thorax, with poorly-preserved surface, has been found ( Pl. 50M ). It is not strongly tapered posteriorly and its pleural furrows are broad and shallow.

Hypostome and pygidium not known.

Remarks. Stoloharpes capricornus is similar to S. calceolus but differs in having: a cephalon that is more pyriform and widest at the eye lobes rather than at the mid-point between the eye lobes and alae; a genicranium widest at mid-point between the eye lobes and the alae not at the alae; a glabella with blister-like tubercles on its dorsal surface, rather than being tubercle free; muscle insertion furrows at S2 and S3 rather than none; interalar furrows; alar depressions; a shorter (tr.) posterior border; a genal area with faint caeca and ill-defined eye ridges, which are lacking in S. calceolus ; a less inflated anterior boss that is not joined to the glabella and does not reach down to the girder; a weak girder kink; a brim width ratio of 0.62, which is 20/% lower than that of S. calceolus ; genal spines that follow the curve of external rim rather than being set at an oblique angle; and a girder extension that meets the internal rim one third of the way down the prolongation, not one quarter as in S. calceolus .

The cephalon of S. capricornus is much the same shape in dorsal view as that of Kielania triabsidata Ormiston, 1971 , but differs from it in having: the glabella 27% longer (sag.) in relation to its width (tr.); no glabellar lobation like that of K. triabsidata ; the alae much less prominent; the genal roll narrower in lateral view in relation to the brim than in K. triabsidata ; longer genal prolongations which in lateral view have an external rim that only starts to curve upwards two-thirds of the way down the prolongation, while that of Kielania triabsidata curves upwards over most of its length and terminates in a longer and more robust genal spine, which is not tilted adaxially; the genal spine carried solely on the lower lamella whereas that of K. triabsidata appears to be at least partly carried on the upper lamella.

Stoloharpes aff. capricornus ( Pl. 50G–J ) differs from S. capricornus by having glabellar flanks that are more convex than tectiform; no tubercles or blisters on the glabella or internal rim; no light caeca on the genal areas or brim; no eye ridges; no preglabellar field; the anterior boss is joined to the glabella but does not reach down to the girder; there is no girder kink and the prolongations are some 12% longer than those of S. capricornus .

Figures

PLATE 50. A–F Stoloharpes capricornus n. sp., El Otfal Formation, upper Eifelian, Taouz East (Fig. 2B, Map 15, site 1), dorsal exoskeleton of cephalon only, holotype, NHMUK It 29364. A, dorsal, B, lateral and C, anterior view. D, lateral view of eye lobe (uncoated) E, lateral view of muscle insertion scars on glabella (uncoated). F, dorsal view of brim perforations. G–J Stoloharpes aff. capricornus, upper Eifelian, Hamar Laghdad (Fig. 2B, Map 11, site 14), dorsal exoskeleton of cephalon only, NHMUK It 29366. G, dorsal, H, lateral and I, anterior view. J, dorsal view of brim perforations. K–O Stoloharpes capricornus n. sp., El Otfal Formation, upper Eifelian, TaouzEast (Fig.2B, Map 15, site 2), dorsal exoskeleton thorax enrolled, paratype, NHMUK It 29365. K, dorsal, L, lateral and M, posterior view. N, dorsal view of brim perforations and O, lateral view of eye lobe. Scale bars shown represent 1 cm unless otherwise indicated.