Harpes lentigo, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 47-49

Harpes lentigo n. sp.

Plate. 7A–M

Diagnosis. Cephalon widest (tr.) across anterior of alae. Large ovoid glabella, anteriorly steeply-sloping with prominent tubercles straddling crest. Tubercles on dorsal surface of eye lobe, occipital ring and internal rim. Alae inflated and moderately large. Alar depression deep and alar and preglabellar furrows well defined. Shallow pitting on post ocular genal area. Narrow (sag.) brim, narrowing moderately posterolaterally (brim width ratio 0.64) with moderately large perforations decreasing in size distally. In lateral view, external rim curves slightly upwards and profile of internal rim weakly wave-like.

Etymology. Lentigo, Latin for freckle. The pronounced tubercles of the glabella and eye lobes give an impression of freckles.

Material and occurrence. Holotype: NHMUK It 29236, Pl. 7A–G , from a coral horizon 5 metres below the “ Morocconites Horizon ” ( McKellar & Chatterton 2009, p. 13) (12.2 m down slope), Tazoulait Formation, Emsian, Jbel Oufatene ( Fig. 2B, Map 8, site 4), a dorsal exoskeleton with disarticulated thorax . Paratypes: NHMUK It 29237 (1– 3), Pl. 7H–M , from the type horizon and type locality ( Fig. 2B, Map 8, site 5), a group of 3 disarticulated and slightly crushed exoskeletons .

Other material: H. cf. lentigo, NHMUK It 29239 and NHMUK It 2938 are dorsal cephalic exoskeletons only. NHMUK It 29239, Pl. 8A–H , is from a horizon midway between the “ Lobopyge Couche ” and the “ Phylonix ( Quadrops ) Couche”, El Otfal Formation, Eifelian, Jbel Issoumour ( Fig. 2B, Map 7, site 14). NHMUK It 29238, Pl. 8I–L , is from the “ Lobopyge Couche ” ( McKellar &Chatterton, 2009, p. 12), El Otfal Formation, Eifelian, Jbel Issoumour ( Fig. 2B, Map 7, site 7) and is a specimen with morphological abnormalities. Both “Couches” are close to the Emsian/Eifelian boundary.

Description. Cephalon length (sag.) around 70% of width (tr.). Genicranium widest at posterior border, length (sag.) around 75% of width (tr.). Glabella anterior to S0 broad (width (tr.) 70% of length (sag.)), rounded anteriorly and with pronounced tubercles densely packed along crest. S1 sloping posteriorly before curving anteriorly near crest. No furrows at S2, S3 or S4. Preglabellar furrow distinct and preglabellar genal area length (sag.) 20% of width (tr.). Axial furrows deep, weakly convergent. Occipital furrow deep and broad (sag.) about same width (exsag.) as posterior border. Occipital ring medially broadened and with tubercles. Large moderately inflated occipital node at anterior edge of occipital ring. Posterior border short (tr.), around 30% of width (tr.) of occipital ring. Alae broad, laterally directed and reaching more than 50% of way across (tr.) genal area. Alar furrows deep, well defined. Interalar furrows and alar depressions present.

Genal area width (tr.) around 57% of length (exsag.) and with pits. Eye lobes oval in shape, strongly inflated and with tubercles on dorsal surfaces finer than those on glabella. Eye position ratio about 0.86. Two well separated horizontal oval eye lenses face outwards anterolaterally and posterolaterally respectively ( Pl. 7E, F ). Genal ridge just discernible on genal area, becoming clearer as it extends posteriorly across genal roll. Genal roll moderately steep (sag. 580 and laterally 630). Anterior boss barely inflated, girder kink weak. Perforations on genal roll smaller than on brim except for a row of larger perforations immediately above girder and at inner margin of fringe across anterior of glabella.

Brim narrow (sag.), 27% of cephalic length (sag.), sloping (sag.) at around 160. Brim width ratio around 0.60. Brim perforations become smaller away from girder and average standardised diameter of perforations on central part of brim is around 190 μm ( Pl. 7G, K ) with a row of larger perforations around internal and external margins of brim. Caeca just reaching onto brim. External rim broad with no tubercles on dorsal surface. Marginal band near vertical with tubercles and a ridge top and bottom.

Prolongations around 0.96 times sagittal cephalic length, curving adaxially posteriorly so that distal ends point obliquely adaxially. In lateral view profile of internal rim barely upturned distally. Internal rim broad (tr.) and with tubercles on dorsal surface. Below internal rim row of perforations larger than those on rest of prolongation immediately beneath. Extension of girder meeting internal rim about halfway down prolongation. External rim turning upwards posteriorly to meet internal rim at end of prolongation. Genal spine short and stout.

Thorax with at least 23 thoracic segments. Axis strongly vaulted with axial rings becoming narrower (tr.) posteriorly. Anterior and posterior bands of pleura narrow (exsag.) and of equal width (exsag.). Pleural furrow deep and extending onto outer portion of pleura, which slants slightly posteriorly from junction of inner portion before turning down, and has a rounded distal end.

Remarks. Harpes lentigo’s morphology lacks three of the genus’s diagnostic characters shown in Table 5a: the genal area at 57% of its length (exsag.) is wider than the upper limit of 54%, it has a weak girder kink, and caeca reaching onto brim.

Harpes lentigo differs from H. boudibensis ( Pl. 1A–Q ) in having a broader genal area with a width (tr.) 57% of its length (exsag.) and alae reaching only 60% of the way across compared with more than 70% in the case of H. boudibensis . Also, the glabella is narrower, anteriorly steeper and more ovoid. The eye lobes have tubercles on dorsal surface and there is coarse pitting on post ocular genal area, not evident on H. boudibensis . There is a preglabellar field, a well-defined preglabellar furrow, a boss and a weak girder kink. The brim width ratio is some 30% greater and standardised brim 20% larger.

The differences between H cf. lentigo (NHMUK It 29239) ( Pl. 8A–L ), and H. lentigo are that NHMUK It 29239, has a slightly wider (tr.) cephalon with the widest point being across the midpoint of the glabella rather than across the anterior edge of the alae. Also, the eye lobes are set a little closer to the axial furrow and the tubercles on the glabella are fewer and finer and absent on the dorsal surfaces of eye lobes. The brim differs too, having a brim width ratio of about 0.75 rather than 0.65, and the genal area is finely perforated with the cuticle surrounding the perforations being lighter in tone than elsewhere on the genal area (see Pl. 8A, F, G .).

Figures

PLATE 1. A–Q Harpes boudibensis n. sp., El Otfal Formation, Eifelian. A–D, articulated dorsal exoskeleton, paratype, NHMUK It 29226, type locality horizon 1 (site 1). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations. E–J, dorsal exoskeleton, pygidium enrolled, paratype, NHMUK It 29228, type locality, horizon 2 (site 5). E, anterior, F, dorsal and G, lateral view. H, ventral view of anterior part of cephalon, I, hypostome and J, dorsal view of brim perforations. K–Q, enrolled articulated dorsal exoskeleton, holotype, NHMUK It 29227, horizon 1, Section 2 (Fig. 7), Jbel Issoumour (Fig. 2B, Map 7, site 4). K, dorsal, L, anterior, M, lateral view, N, anterior dorsal view of genal roll and brim perforations, O, dorsal view of brim perforations, P, lateral dorsal view of eye lobe and muscle impression areas at S0, S1, S2 and S3, and Q, lateral view of eye lobe. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 7. A–M Harpes lentigo n. sp., from a coral horizon 5 m (12.2 m down slope) below the “Morocconites Couche”, Tazoulait Formation, Emsian, Jbel Oufatene (Fig. 2B, Map 8, site 4). A–G dorsal exoskeleton, thorax disarticulated and partially rolled, holotype, NHMUK It 29236.A, dorsal, B, anterior, C, posterior and D, lateral view. E, lateral view of eye lobe (uncoated), F, laterodorsal view of eye lobe (uncoated) and G, dorsal view of brim perforations. H–M Harpes lentigo n. sp., plate of three disarticulated dorsal exoskeletons, paratypes, NHMUK It 29237 (1 to 3) (Fig. 2B, Map 8, site 5). H, dorsal, I, anterodorsal and J, lateral view. K, dorsal view of brim perforations, L, lateral view of pleurae and M, anterior view of rim. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 8. A–L Harpes cf. lentigo, El Otfal Formation, Eifelian, Jbel Issoumour. A–H from an horizon halfway between “Lobopyge Couche” and “Phylonix Couche”, dorsal exoskeleton of cephalon, NHMUK It 29239 (Fig. 2B, Map 7, site 14). A, dorsal, B, anterior and C, lateral view. D, anterior view of perforations on brim and genal roll, E, dorsal view of perforations on brim, F, lateral view of eye lobe (uncoated), G, lateral view of genal area (uncoated) and H, lateral view of the internal rim. I–L from the “Lobopyge Couche”, dorsal exoskeleton of cephalon, NHMUK It 29238 (Fig. 2B, Map 7, site 7). I, dorsal, J, anterior and K, lateral view. L, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.