Pinnuloharpes hannabouensis, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 88-89

Pinnuloharpes hannabouensis n. sp.

Plate 40A–N

Diagnosis. Cephalon inverted U in shape, and genicranium strongly vaulted. Occipital ring not medially broadened and in lateral view, nearly upright and lower than glabella anterior to S0. Course of inner fringe across anterior boss not marked by row of large perforations. Anterior boss barely inflated. Brim very narrow, 25% of cephalic length (sag.), and nearly flat. Marginal band with three ridges. Internal and external rims meeting and joining at end of prolongations. Anterior of thorax not broadening posteriorly and pleural furrows effaced.

Etymology. Named after the village of Ksar Hannabou, close to the type locality.

Material and occurrence. Holotype: NHMUK It 29333, Pl. 40E–I , from horizon 5 m down slope of “ Radiaspis Couche ”, Eifelian/Givetian boundary, in an outcrop 3.8 km West of Ksar Hannabou and 8.3 km S.S. W. of El Jorf. ( Fig. 2B, Map 6, site 11), dorsal exoskeleton with pygidium missing . Paratype: NHMUK It 29334, Pl. 40A–D , from type horizon and type locality ( Fig. 2B, Map 6, site 12), dorsal exoskeleton of cephalon only . Paratype: NHMUK It 29335, Pl. 40J–N , from type horizon and type locality ( Fig. 2B, Map 6, site 13), dorsal exoskeleton with pygidium incomplete .

Description. Cephalon inverted U in shape, widest at mid-point between eye lobes and alae. Genicranium broad, widest at posterior border. Glabella anterior to S0 narrow, width (tr.) 65% of length (sag.), and with rounded crest and flanks. Dorsal surface without sculpture. S1 sloping backwards, before curving forwards near crest, and L1 very slightly inflated in some individuals. Axial furrows convex, converging gently anteriorly. Preglabellar furrow distinct and bowed upwards in anterior view. Occipital furrow broad, deep, and medially straight. Occipital ring not medially broadened, same width (tr.) as posterior border and in lateral view, lower than glabella anterior to S0. Alae small (tr.), nearly as wide (tr.) as long (exsag.), and laterally directed. Alar furrow shallow but well-defined. Border moderately short (tr.), just under 40% of occipital ring width (tr.). Narrow preglabellar field, and genal area fairly broad with width (tr.) just under 60% of length (exsag.).

Genal area without sculpture or pits. Eye lobes large (exsag.) (50% of width of glabella at S0), inflated, reniform, without tubercles on dorsal surface and located away from inner margin of fringe. Each eye lobe with two eye lenses of equal size. No eye ridges or genal ridges. Course of inner margin of fringe across anterior boss not marked by larger perforations. Anterior boss not joined to glabella and reaches down to moderately narrow girder, which has weak kink. Genal roll sloping moderately steeply anteriorly (≈ 570), and steeply (≈ 680) laterally. In lateral view, fringe on genal roll narrowing strongly posteriorly. Perforations on genal roll same size as those on brim, and no row of larger perforations above girder.

Brim straight, barely sloping, narrow, with its width (sag.) being 26% of cephalic length (sag.). Brim width ratio around 0.80. Brim perforations moderately fine, with a diameter of just under 150 µm. Light caeca, reaching across brim. Exterior rim is stout and without sculpture on dorsal surface. Marginal band straight, with ridge at top and bottom but no tubercles. Length (exsag.) of prolongation just over 80% of cephalic length (sag.). In dorsal view, internal rims are subparallel, external rims straight, slanting adaxially. In lateral profile, internal rims straight and meeting external rim at end of prolongations. Dorsal surface of internal rim smooth. Genal spine long, following curve of external rim. Extension of girder meeting internal rim one third of way down. Brim steepening quickly to near vertical on prolongations.

Thorax has 17 segments, axis is tapered moderately posteriorly, and axial rings are without sculpture or pitting. Thorax not strongly tapered and maintains its width (tr.) posteriorly to 5 th thoracic segment. Inner portion of pleurae only start to shorten (tr.) significantly posteriorly from 9 th segment. Pleural furrows effaced. Outer portion of pleurae offset slightly to inner portion, curved anteriorly and terminating in a point. Three axial rings on pygidium.

Hypostome unknown.

Remarks. Pinnuloharpes hannabouensis has a deep occipital furrow but otherwise complies with the other 9 diagnostic characters of the genus shown in Table 5c.

Pinnuloharpes hannabouensis differs from the type species P. segaouii , in having: a cephalon which is widest at mid-point between eye lobes and alae, rather than at alae; a genicranium that is 15% narrower, more vaulted and widest at alae, rather than at the posterior border; a glabella that is narrower and has convex rather than tectiform flanks; a shallow preglabellar furrow that is bowed upwards, while that of P. segaouii is nearly effaced; a narrow preglabellar field, which is absent in P. segaouii ; a deep occipital furrow; the occipital ring in lateral view lower than the glabella anterior to S0 and more upright than that of P. segaouii ; alae which are parabolic in shape rather than subtriangular; a posterior border that is 30% shorter (tr.) than that of P. segaouii ; a genal area that is 20% narrower (tr.); eye lobes which are more inflated and reniform rather than oval in dorsal view; no eye ridges; the anterior boss less inflated, and there is no row of larger perforations across the top of the boss to mark the inner margin of the fringe, as there is in the case of P. segaouii ; the genal roll sloping around 20% more steeply anteriorly and laterally; the girder is narrower; the fringe, in lateral view, narrows less posterolaterally; the brim less steeply sloping, with a width (sag.) nearly 40% narrower than that of P. segaouii , light caeca reaching across it, and a marginal band that has three ridges rather than none; slightly shorter prolongations, with the extension of the brim on the prolongations steepening more strongly; the external rims in dorsal view slanting rather than curving adaxially and in lateral view, the internal rims meeting at end of prolongations rather than before; the thoracic pleural furrows erased; and the outer portion of pleurae terminating in a point rather than being rounded, as they are in P. segaouii .

Figures

PLATE 40.A–N Pinnuloharpes hannabouensis n. sp., from an horizon 5 m down slope of “Radiaspis Couche”, upper Eifelian/ Givetian boundary, Ksar Hannabou. A–D dorsal exoskeleton of cephalon only, paratype, NHMUK It 29334 (Fig. 2B, Map 6, site 12). A, dorsal and B, lateral view. C, lateral view of eye lobe (uncoated) and D, dorsal view of brim perforations. E–I dorsal exoskeleton cephalon and thorax only, holotype, NHMUK It 29333 (Fig. 2B, Map 6, site 11). E, dorsal, F, anterior and G, lateral view. H, lateral view of eye lobes, I, dorsal view of brim perforations. J–N dorsal exoskeleton pygidium incomplete, paratype, NHMUK It 29335 (Fig. 2B, Map 6, site 13). J, dorsal, K, anterior and L, lateral view. M, lateral view of eye lobe and N, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.