Pinnuloharpes chaperon, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 86-87

Pinnuloharpes chaperon n. sp.

Plate 41A–J

Diagnosis. Cephalon pyriform, strongly vaulted and widest at eye lobes. Glabella inset and joined to anterior boss. S1 not rising out of axial furrow. Genal areas are strongly convex (sag. and exsag.) and genal roll is steeply sloping, over 600 anteriorly and over 700 laterally. Brim wide (sag.), 35% of cephalic length (sag.), barely sloping and brim width ratio very low, at 0.52. Perforations on brim very fine (<80 μm) and even finer on genal roll. Brim steepens quickly to near vertical on prolongations. In dorsal view, genal spine not following curve of exterior rim and curving upwards in lateral view.

Etymology. Similar to the shape of the chaperon hat worn in the Middle Ages.

Material and occurrence. Holotype: NHMUK It 29332, Pl. 41G–J , from “ Basseiarges Couche ”, Eifelian, Fezna ( Fig. 2B, Map 6, site 4), dorsal exoskeleton of cephalon only . Paratypes: NHMUK It 29331 (1 and 2), Pl. 41A–F , from type locality and type horizon ( Fig. 2B, Map 6, site 2) , NHMUK It 29331 (1), dorsal exoskeleton of cephalon only, and NHMUK It 29331 (2), ventral exoskeleton of cephalon only.

Other material: Pinnuloharpes cf. chaperon : NHMUK It 29330, Pl. 41K–N , from P. chaperon type locality and type horizon ( Fig. 2B, Map 6, site 21), dorsal exoskeleton of cephalon only.

Description. Cephalon widest at eye lobes and pyriform in shape. Genicranium narrow, width (tr.) 1.25 times length (sag.), strongly vaulted and widest at alae. Glabella inset, narrow, with rounded crest and tectiform flanks, no sculpture or pitting. S1 barely rising out of axial furrow. Axial furrows convex and weakly convergent anteriorly. Preglabellar furrow indistinct. Occipital furrow is broad, shallow and medially straight in dorsal view. Occipital ring same width (sag.) as posterior border (exsag.), and in lateral view, sloping posteriorly and same height as glabella anterior to S0. No sculpture or pitting on dorsal surface. Occipital node poorly inflated. Alae large (tr.), over 40% of width (tr.) of glabella at S0, just broader (tr.) than long (exsag.) and anterolaterally directed. Alar furrow shallow, well-defined. Posterior border moderately wide (tr.), and no preglabellar field.

Genal area moderately broad and without caeca, pits or tubercles. Eye lobes oval, large (exsag.), barely inflated and located away from inner margin of fringe. Each eye lobe with two lozenge-shaped eye lenses ( Pl. 41D ). No genal ridge, and eye ridge poorly defined. Inner margin of fringe not marked by bigger perforations as it crosses anterior boss. Anterior boss inflated, reaching down to weak girder kink and joined to glabella. Preaxial furrows converge. Genal roll steeply sloping 620 anteriorly, and over 720 laterally, and in lateral view, narrowing strongly posteriorly. Perforations on genal roll are smaller than those on brim and no row of larger perforations above girder. Genal roll without caeca; girder moderately wide and brim wide (sag.), barely sloping and concave anteriorly, straight laterally. Brim width ratio low, at around 0.50. Brim perforations very fine, around 70µm, and no caeca on brim. Rim stout, dorsal surface not tilted outwards and without sculpture. Marginal band near vertical, straight, with tubercles but without ridges. Prolongations moderately short (exsag.), at around 80% of cephalic length (sag.). In lateral view, prolongations strongly tapered and internal rims concave. Internal rims subparallel in dorsal view, external rims curve adaxially posteriorly. Internal and external rims separated by a row of perforations from where they meet to end of prolongation, where they join. Genal spine long and set at an angle to curve of external rim. Tubercles on dorsal surface of internal rim, and extension of girder meeting internal rim 1/3 way down prolongation. Brims quickly steepen to near vertical on prolongations.

Thorax, pygidium and hypostome unknown.

Remarks. Pinnuloharpes chaperon has cephalon that has a pyriform profile, a genicranium that is broadest at the alae rather than the posterior border and the course of the inner margin of the fringe cannot be determined from the material presented here, otherwise it has the other 8 diagnostic characters of the genus shown in Table 5c.

Pinnuloharpes chaperon is quite similar to P. hastatus ( Lütke 1965) but differs in having: a cephalon that is widest opposite eye lobes, not mid-point between the eye lobes and alae, and is more pyriform in shape; its genicranium widest at the alae and not the posterior border; the glabella inset and joined with the anterior boss; the axial furrows convex rather than straight; a wider occipital furrow; the occipital ring in lateral view the same height as the glabella anterior to S0, while that of P. hastatus is lower; a very shallow preglabellar furrow and no preglabellar field; alae with a width (tr.) 1.05 times their length (exsag.), while those of P. hastatus have a width of only around 0.75 times their length; a much broader (tr.) genal area, at 58% of its length (exsag.), rather than 47% as in P. hastatus ; a wider (sag.) brim, being 36% of cephalic length (sag.), rather than 32% in P. hastatus ; a much lower brim width ratio (0.49 rather than 0.76); shorter (exsag.) prolongations, which have a length (exsag.) that is 81% of cephalic length (sag.), compared with 89% in P. hastatus ; the extension of the brim on the prolongations steepening to near vertical, not just along their proximal edge.

Pinnuloharpes chaperon is different to other species of Pinnuloharpes , in having a pyriform cephalon and a low brim width ratio. The pyriform cephalon is similar to the cephala of Stoloharpes species, however, the brims of these species are sloping and convex, whereas that of P. chaperon is almost flat.

Pinnuloharpes cf. chaperon ( Pl. 41K–N ) differs from P. chaperon in that its cephalon is not pyriform and its prolongations are shorter than those of P. chaperon .

Figures

PLATE 41. A–J Pinnuloharpes chaperon n. sp., “Basseiarges Couche”, El Otfal Formation, Eifelian, Fezna. A–F exoskeleton of cephalon only, paratypes, NHMUK It 29331 (1 and 2), (Fig. 2B, Map 6, site 2). A–E NHMUK It 29331 (1). A, dorsal, B, lateral and C, anterior dorsal view. D, lateral view of eye lobe (uncoated) and E, dorsal view of brim perforations. F, NHMUK It 29331 (2), ventral exoskeleton of upper lamella. G–J dorsal exoskeleton of cephalon, holotype, NHMUK It 29332 (Fig. 2B, Map 6, site 4). G, dorsal, H, anterior and I, lateral view. J, dorsal view of brim perforations. K–N Pinnuloharpes cf. chaperon, “Basseiarges Couche”, El Otfal Formation, Eifelian, Fezna. Dorsal exoskeleton of partial cephalon only, NHMUK It 29330 (Map 2B, site 21). K, dorsal, L, anterior and M, lateral view. N, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.