Pinnuloharpes merzaneensis, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 93-94

Pinnuloharpes merzaneensis n. sp.

Plate 45A–L

Diagnosis. Cephalon ovoid, glabella with tectiform flanks. S1 short, sloping backwards. L1 weakly inflated and axial furrows effaced at junction of L1 and alae. Occipital furrow shallow, occipital ring pitted and in lateral view, higher than glabella anterior to S0. Genal area very broad (tr.). Anterior boss joined to glabella and preglabellar furrow effaced. Perforations becoming smaller for a short distance away from girder. Girder kink pronounced. Brim narrowing strongly posterolaterally. Marginal band with ridge top and bottom. Tubercles on dorsal surface of internal rims. Pygidium with four pleurae and tubercles on terminal piece.

Etymology. Named after Merzane, the region of the type locality.

Material and occurrence. Holotype: NHMUK It 20349, Pl. 45A–H , from a horizon 7.5 m below (15 m down slope in a North Easterly direction) the Morocops granulops ? ( Chatterton et al., 2006; van Viersen et al. 2017) horizon at the base of the “Red Cliff” ( Klug et al., 2009.), Hamar Laghdad ( Fig. 2B, Map 11, site 6), articulated dorsal exoskeleton. Paratype: NHMUK It 29348, Pl. 45I–L , from 2.5 m above type horizon ( Fig. 2B, Map 11, site 5), dorsal exoskeleton of a partial cephalon only.

Description. Cephalon ovoid, widest at mid-point between eye lobes and alae. Genicranium broad; glabella not inset, pitted and with tectiform flanks. S1 short, slopping backwards. Axial furrows convex, converging anteriorly at just over 15 o to axis and not crossing junction of alae and L1. L1 mildly inflated, preglabellar furrow almost effaced and occipital furrow shallow. Occipital ring pitted, not medially broadened (sag.), about same width (sag.) as posterior border (exsag.) and in lateral view, higher than glabella anterior to S0. Occipital node moderate in size and weakly inflated. Alae laterally directed, alar furrows shallow and poorly defined. Posterior border is moderately short (tr.), being around 30% of width (tr.) of occipital ring.

Genal area without pitting and very broad (tr.), with width (tr.) over two-thirds its length (exsag.). Eye lobes large (exsag.), and there is no genal ridge or eye ridge. Anterior boss inflated and joined to glabella. Genal roll moderately steep anteriorly (≈ 550 to horizontal), steep laterally (≈ 700 to horizontal). Inner fringe narrowing strongly in lateral view, to nearly 60% of its width (tr.) at eye lobes. Perforations on genal roll smaller than those on brim and becoming smaller for a short distance away from girder. Girder narrow (1.4% of genicranium width (tr.)).

Brim moderately wide, gently concave (sag.), straight laterally, barely sloping but quickly steepening to near vertical on prolongations. Brim width ratio very low for genus, at 0.60. Brim without caeca and brim perforations moderately fine, with a standardised diameter of under 130µm. Dorsal surface of external rim without sculpture; marginal band near vertical, straight with tubercles and ridge at top and bottom.

Length (exsag.) of prolongations 88% of cephalic length (sag.). Internal and external rims curve adaxially in dorsal view, and internal rim straight in lateral view. Genal spine extends curve of external rim. Extension of girder meets internal rim 1/3 way down prolongations. There are two rows of fine tubercles forming subparallel ridges on ventral surface of external rim ( Pl. 45D ).

Thorax with at least 22 segments. Inner portion of pleurae lengthening (tr.) to 5 th segment, then tapering so that at last segment it is 25% of 5 th. Axis tapering moderately, with width (tr.) of last axial ring being just over 40% of width of first. Pleural furrows broad, shallow, almost effaced and barely extend beyond fulcrum. Outer portion of pleurae set at shallow angle to inner portion, slanting slightly posteriorly from fulcrum and running distally for a short distance before bending near vertically downward; finger-like, straight with rounded ends ( Pl. 45E ). Pitting on axial rings and pleurae.

Pygidium with at least 3 axial rings and terminal piece. There are four pairs of pleural ribs, inner portions of which are at right angles to axis, but outer portion slants posterolaterally from fulcrum, and distal ends are rounded. Interpleural furrows are fully developed, except those defining fourth rib, which are very shallow. Terminal piece short (sag.) and broad (tr.) with slightly rounded distal edge. There are no pleural furrows. Fine tubercles on axial rings and terminal piece.

Hypostome not known.

Remarks. P. m erzaneensis has a slightly inflated L1. Also, from the available material (see Pl. 5 ) it is not possible to determine with any certainty the number of the eye lenses on each eye lobe or the course of the inner margin of the fringe across the anterior of the genal areas. Otherwise, P. merzaneensis complies with the diagnostic characters of the genus shown in Table 5c.

A comparison between Pinnuloharpes merzaneensis and P. haustrum is given in the systematics of P. haustrum above. P. merzaneensis is also similar to P. hamarlaghdadensis but differs in having: a glabella with flanks that are tectiform not rounded; axial furrows that are convex not straight, converge more strongly anteriorly and do not cross at the junction of the ala and L1; an almost effaced preglabellar furrow, whereas that of P. hamarlaghdadensis is well-defined as is the preglabellar field; the occipital ring not medially broadened; its alae laterally directed a shorter (tr.) posterior border; the anterior boss joined to glabella; the genal area 10% wider than that of P. hamarlaghdadensis ; a genal roll that is less steeply-sloping laterally and has perforations which are graduated, becoming smaller away from girder; a narrower (sag.) girder; a brim that is slightly concave (sag.), straight laterally and with a brim width ratio of around 0.60, some 12% lower than that of P. hamarlaghdadensis ; and in dorsal view, the internal rim of P. merzaneensis curves adaxially rather than being subparallel.

Although the cephalic length (sag.) of the holotype of P. hamarlaghdadensis is just under 9 mm, a third smaller than that of P. merzaneensis , it does not seem that any differences are ontogenetic. The genal roll of P. merzaneensis is steeper-sloping anteriorly, and the brim and rim width (sag.) relative to cephalon length (sag.) are the same.

Figures

PLATE 5. A–J Harpes lahceni, dorsal exoskeleton partially enrolled, holotype, NHMUK It 29232, from El Otfal Formation, Eifelian, Horizon 3, Section 2 (Fig. 7), Jbel Issoumour (Fig. 2B, Map 7, site 15). A, dorsal, B, lateraland C, anterior view. D, posterior view, showing dorsal surface partially enrolled thorax and pygidium, and ventral surface of prolongations, E, lateral view of eye lobe, F, ventral view of prolongations, G, dorsal lateral view of eye lobe, H, dorsal view of brim perforations, I, dorsal view of dorsal surface of rim and J, dorsal view of pygidium. K–L Harpes lahceni, dorsal exoskeleton partially enrolled, paratype, NHMUK It 29234, from El Otfal Formation, Eifelian, “Harpes Couche” above Acanthopyge horizon, Timerzit (Fig. 2B, Map 10). K, dorsal view and L, lateral view. M–N Harpes lahceni, dorsal exoskeleton partially enrolled, paratype, NHMUK It 29233, from El Otfal Formation, “Phylonix Couche”, Jbel Oufatene (Fig. 2B, Map 8). M, dorsal and N, lateral view. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 45. A–L Pinnuloharpes merzanensis n. sp., upper Emsian, Hamar Laghdad. A–H dorsal exoskeleton partly enrolled, holotype, NHMUK It 29349 from 7.5 m below P. hamarlaghdadensis horizon (Fig. 2B, Map 11, site 6). A, dorsal, B, anterior, C, lateral, D, posteroventral and E, posterolateral view. F, dorsal view of brim perforation, G, dorsal view of pygidium and H, dorsal view of pitting on genal area. I–L dorsal exoskeleton of a partial cephalon only, paratype, NHMUK It 29348 from 2.5 m above type horizon (Fig. 2B, Map 11, site 5). I, dorsal, J, lateral and K, anterior view. L, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.