Pinnuloharpes igaouii, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 91-92

Pinnuloharpes igaouii n. sp.

Plate 36A–K

Diagnosis. Cephalon is moderately vaulted, glabella strongly vaulted.Alae are inflated proximally, and alar furrows erased distally. Eye lobes pronounced. Slope of genal roll is moderate, anteriorly continuing anterior slope of glabella. Anterior boss is barely inflated. Perforations on genal roll decrease in size upwards, away from girder. Brim barely sloping; brim perforations widely spaced, decrease rapidly distally to become very fine, before becoming larger again close to rim.

Etymology. For Hssaine Igaoui, a Moroccan trilobite worker who found the holotype.

Material and occurrence. Holotype: NHMUK It 29360, Pl. 36A–H , from a coral horizon 500 m to the N.W. of Jbel Ou-Driss, Boutiskaouine Formation?, lower Emsian ( Fig. 2B, Map 4, site 5), dorsal exoskeleton of cephalon only . Paratype: NHMUK It 29361, Pl. 36 I–K , from lower Emsian coral horizon, “ Ceratocephala Horizon ”, Boutiskaouine Formation?, North Jbel Ou-Driss ( Fig. 2B, Map 4, site 8), dorsal and ventral exoskeleton of damaged cephalon and partial thorax . Paratype: NHMUK It 29267, Pl. 13K–O , from a lower Emsian coral horizon, 20 m below Lioharpes ammari horizon, Boutiskaouine Formation?, north Jbel Ou-Driss ( Fig. 2B, Map 4, site 6), dorsal exoskeleton of cephalon only .

Other material: Pinnuloharpes aff. igaouii, NHMUK It 29362, Pl. 36L–O , from “ Struveaspis Couche ”, Fezna, Eifelian ( Fig. 2B, Map 6, site 1), partial dorsal exoskeleton of cephalon only.

Description. Cephalon ovoid, widest at eye lobes. Genicranium broad, widest at posterior border. Glabella broad, with rounded crest, tectiform flanks and tubercles, but no pitting. S1 short, very shallow and slopes posteriorly. L1 inflated. Axial furrows slightly convex, moderately convergent anteriorly and effaced at junction of alae and L1. Preglabellar furrow indistinct, straight in anterior view. Occipital ring broader (sag.) than posterior border (exsag.); tubercles on dorsal surface; nearly vertical in lateral view and same height as glabella anterior to S0. Occipital node barely inflated most noticeable on paratype. L1 inflated. Alae small (tr.) and laterally directed, alar furrows shallow, almost effaced. Posterior border moderately wide (tr.), just over 40% of occipital ring width (tr.), and preglabellar field narrow.

Genal area moderately broad, very finely pitted and without tubercles. Eye lobes inflated; large (tr.), 35% of width (tr.) of glabella at S1; elongated oval in shape; and located close to inner margin of fringe. Each eye lobe has 2 lenses of approximately equal size. Eye ridge is poorly defined. Inner margin of fringe across anterior of genal areas convex and its course across anterior boss marked by row of large perforations.Anterior boss barely inflated and not connected to glabella. Genal roll sloping gently anteriorly and moderately steeply laterally; internal fringe does not narrow strongly posteriorly in lateral view; perforations smaller than on brim, decreasing in size away from girder over bottom third of genal roll. Girder moderately wide, and girder kink barely present.

Brim wide, 34% of cephalic length (sag.); barely sloping; concave (sag.), becoming straight laterally and steepening quickly on prolongations. Brim width ratio 0.63. Brim perforations moderately fine, decreasing in size away from girder over inner third of brim. No caeca. Dorsal surface of rim lacks sculpture. Marginal band straight and near vertical. Length (exsag.) of prolongations around 87% of cephalic length and, in lateral view, prolongations not strongly tapered, height at midpoint being 55% of height at junction with posterior border. Internal rim concave. In dorsal view, both rims curve adaxially and internal rim has tubercles on dorsal surface. Genal spine short and does not follow curve of external rim. Extension of girder on prolongations meets internal rim halfway down. Thorax with at least 20 segments; not widening anteriorly and not strongly tapered posteriorly. Pleural furrows very shallow and broad. Outer portion of pleurae at an angle to inner portion and curving anteriorly.

Hypostome ( Pl. 36J ) has a large egg-shaped anterior lobe of the middle body, with a very short (sag.) posterior lobe. The lateral border, which is narrow anteriorly, broadens very slightly two-thirds of the way back, before narrowing again. Posterior border narrow; anterior border even narrower. Shoulders broad close to the anterior of the hypostome, lateral distal edge sloping abaxially. Surfaces are tubercle-free, very similar to that of P. haustrum described above, but middle furrow not present. Pygidium not known.

Remarks. P. igaouii has an inflated L1, an anterior eye lens that is the same size as the posterior lens rather than being bigger and an inner margin of the fringe the course of which across the anterior of the genal areas is convex rather than concave. Otherwise P. igaouii has the other eight diagnostic characters of the genus shown in Table 5c.

P.igaouii is similar to P. segaouii but differs by having: a cephalon that is widest (tr.) at the level of the eye lobes rather at the alae; a narrower (tr.) genicranium, genal area and posterior border; tubercles on the glabella including the occipital ring, on the eye tubercles and on the internal rim; a broader (sag.) occipital ring; an LI and ala that are inflated with the axial furrow not crossing the junction of the two; a narrow preglabellar field that is absent in the case of P. segaouii ; an inner margin of the fringe the course of which across the anterior of the genal area is convex rather than concave; eye lobes that are more inflated and have two equal sized lenses rather than two different sized lenses; an anterior boss that is not joined to glabella; perforations on the genal roll and the brim that decrease in size away from the girder; a brim that has a lower brim width ratio, is less steeply sloping and in lateral view has a profile that is slightly concave (sag.) rather than being straight. Also, P. igaouii has genal spines that do not follow the curve of the exterior rims and internal rims that in lateral view have a concave profile unlike the weak wave profile of those of P. segaouii .

P. aff. igaouii ( Pl.36L–O ) has affinities to P. igaouii but has: a much more strongly sloping brim, which does not steepen to the same degree on prolongations; a 20% higher brim width ratio, and an occipital ring that, in lateral view, slopes more strongly posteriorly.

The genus of P. igaouii has proven to be one of the hardest of the new species to determine. During the development of the cladogram ( Fig. 9 ) P. igaouii has been in a paraphyletic relationship with Pinnuloharpes and more recently allocated to the harpid genus. Coming from a lower Emsian horizon P. igaouii fits into the beginning of the harpid range whereas the earliest Pinnuloharpes species described herein is from an upper Emsian horizon. While on the bases of information currently available P. igaouii is correctly allocated to Pinnuloharpes , it maybe that if new data is added to the cladogram P. igaouii may be reallocated once again to Harpes .

Figures

FIGURE 9. Cladogram consensus of 636 trees with a 31 node collapse and each tree L = 1968, Ci = 12 and Ri =48

PLATE 13. A–J Lioharpes ammari n. sp., from horizon 2, Section 1 (Fig. 6), Tazoulait Formation, upper Emisian, South flank of Jbel Ou-Driss (Fig. 2B, Map 4). A–E dorsal exoskeleton, pygidium missing, paratype, NHMUK It 29264 (site 12).A, dorsal, B, lateral and C, anterior view. D, lateral view of eye lobe and E, dorsal view of brim perforations. F–H dorsal exoskeleton of partial cephalon, paratype, NHMUK It 29265 (1) (site 13). F, dorsal, G, lateral and H, anterior view. I–J ventral exoskeleton of a partial upper lamella, paratype, NHMUK It 29265 (2) (site 13). I, ventral view and J, lateral view of ventral surface. K–O Pinnuloharpes igaouii n. sp., from a horizon 20 metres down slope from type horizon of Lioharpes ammari n. sp. Boutiskaouine Formation?, lower Emsian North flank of Jbel Ou-Driss (Fig. 2B Map 4 site 6). Dorsal exoskeleton of cephalon only, paratype NHMUK it 29267. K dorsal, L anterior and M lateral view. N lateral view of eye lobe and O dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 36. A–K Harpes igaouii n. sp., Ihandar Formation, Pragian-Emsian boundary. A–H dorsal exoskeleton of cephalon only, holotype, NHMUK It 29360, from coral NW of Jbel Ou-Driss (Fig. 2B, Map 4, site 5). A, dorsal, B, anterior and C, lateral view. D, dorsal anterior view of perforations on genal roll and brim. E, dorsal view of glabellar tubercles, F, dorsal view of brim perforations, G, lateral view of glabellar muscle insertion scars (uncoated) and H, lateral view of eye lobe (uncoated). I–K dorsal exoskeleton of cephalon and partial thorax, paratype, NHMUK It 29361, from Ceratocephala horizon, North Jbel Ou-Driss (Fig. 2B, Map 4, site 8). I, dorsal anterior lateral view (uncoated). J, ventral view of hypostome and K, lateral view of eye lobe (uncoated). L–O Harpes aff. igaouii, dorsal exoskeleton of cephalon only, NHMUK It 29362, from Fezna, “Struveaspis Couche”, El Otfal Formation, Eifelian.(Fig. 2B, Map 6, site 1). L, dorsal, M, lateral and N, anterior view. O, dorsal view of brim perforations. P–R Kielania aff. tumula, Ihandar Formation, upper Pragian (Fig. 2B, Map 10, Site 5) dorsal exoskeleton of a partial cephalon, NHMUK It 29262. P, dorsal, Q, anterior and R, lateral view. Scale bars shown represent 1 cm unless otherwise indicated.