Harpes supercilium, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 53-54

Harpes supercilium n. sp.

Plates 3A–P , 4A–D

Diagnosis. Narrow cephalon, widest (tr.) midway between eyes and alae, width (tr.) is just over 1.1 times sagittal length. Glabella anteriorly rounded cone. Eye lobe with short transverse eye ridge on posterior edge. Alar furrows becoming shallower distally. Prolongations are about same length (exsag.) as cephalon (sag.). In lateral view, internal rim has subdued wave-shaped profile and is terminated by short genal spine. Twenty thoracic segments.

Etymology. Eyebrow in Latin is “ Supercilium ”. The short eye ridges of this species resemble small eyebrows.

Material and occurrence. Holotype: NHMUK It 29252, Pl. 3G–K , from horizon 5, Section 2 ( Fig. 7 ), El Otfal Formation, Eifelian, Jbel Issoumour ( Fig. 2B, Map 7, site 10) . Paratype: NHMUK It 29251, Pl. 3A–F , from type horizon, site 3; paratype : NHMUK It 29250, Pl. 3L–P , from horizon 10, Section 1 ( Fig. 6 ), El Otfal Formation, Eifelian, Jbel Ou-Driss ( Fig. 2B, Map 4, site 24); paratype : NHMUK It 29248, Pl. 4A–D , from horizon 8, Section 1 ( Fig. 6 ), El Otfal Formation, Eifelian, Jbel Ou-Driss ( Fig. 2B, Map 4, site 14) .

Harpes supercilium ’s range overlaps the top of that of H. boudibensis at Jbel Issoumour, extending to at least one later horizon ( Fig. 7 ). It is also present at Jbel Ou-Driss in horizons 8 and 10, as is H. oudris in horizon 5 and H. cf. boudibensis in horizon 7 ( Fig. 6 ).

Description. Cephalon ovoid with widest point midway between eye lobes and alae. Genicranium narrow widest at posterior border. Glabella not inset and fairly broad (tr.), width (tr.) 70% of length (sag.). Glabella crest rounded without tubercles but with fine pitting. S1 rising out of axial furrow, sloping backwards and curving around top of muscle insertion area, which is tulip-shaped with vertical intermittent striations ( Pl. 3O ). Furrows at S2, S3 and S4 barely rising out of axial furrow. S2 and S3 muscle insertion areas oval and just over 25% of size of S1. S4 smaller still and joined with preglabellar furrow and muscle insertion area crossing anterior of glabella. S0 muscle insertion area oval, covering about 75% of area of S1 and spreading into occipital furrow. Axial furrows converging weakly anteriorly at around 13° to axis. Preglabellar furrow distinct and bowed upwards in anterior view. Occipital furrow broad (sag.), deep and medially straight in dorsal view. Occipital ring broad (sag.), not medially broadened, carrying transverse row of fine tubercles posterior to occipital node, and in lateral view, same height as glabella anterior to S0. Occipital node small and preglabellar field narrow, length (sag.) about 20% of width (tr.). L1 inflated and axial furrow crossing junction of L1 and ala.Alae inflated, anterolaterally directed, wider (tr.) than long (exsag.), large (tr.), just under 40% of width (tr.) of glabella at S0 and stretching over 60% of way across genal area. Alar furrow deep, interalar ridge and furrow and alar depression present. Posterior border short, about 25% of width (tr.) of occipital ring.

Genal area narrow, width 52% (tr.) of length (exsag.) and with faint caeca, pits and tubercles. Eye lobes oval to cone-shaped, strongly inflated, very large (exsag., 47% of width (tr.) of glabella at S0) and with tubercles on dorsal surfaces. Visual surface close to inner margin of fringe and eye lobe nearly extending to edge of axial furrow. Each eye lobe with two oval lenses, anterior lenses the largest. Genal and eye ridges present. Eye ridge well defined, short and straight. Course of inner margin of fringe across anterior of genal areas straight and marked by large perforations across anterior of boss only. Anterior boss barely inflated and not reaching down to girder. Genal roll sloping gently anteriorly at around 420, laterally more steeply at around 620. Brim perforations becoming smaller for short distance away from girder to become smaller than on brim. Genal roll without caeca. Girder moderately narrow and without kink.

Brim concave (sag.), straight laterally, sloping anteriorly at 120, moderately wide (sag.), 32% of cephalic length (sag.). Brim width ratio 0.51. For short distance, brim perforations decrease in size away from girder and standardised width of brim perforations in centre of brim is moderately fine, at just over 125μm. Row of larger perforations around inner and outer edges of brim, and brim and light caeca reaching across the whole brim. External rim stout and without tubercles on dorsal surface. Marginal band near vertical, straight with ridges top and bottom, and without tubercles. Prolongations are long (exsag.), 98% of cephalic length (sag.). In dorsal view, internal and external rims curving adaxially and internal rim with weak wave-like profile in lateral view. Tubercles on dorsal surface of internal rim; genal spine short, under 10% length (exsag.) of prolongation. Extension to girder meeting internal rim 1/3 way down prolongation. Brim steepens quickly to near vertical on prolongations.

Thorax with 20 segments. Width (tr.) of axial ring on last segment 30% of that of first segment. No tubercles or pitting on axial rings. Thoracic segments widening (tr.) posteriorly to 7 th segment. Shortest pleura (inner portion only) 55% of longest. Pleural furrows narrow deep and U-shaped. No pitting.

Thorax only partly known, hypostome and pygidium not known.

Remarks. Harpes supercilium has light caeca crossing its brim but otherwise complies with the Harpes diagnostics shown in Table 5a.

Harpes supercilium is very similar to H. oudris but differs in having no tubercles on the glabella, the eye lobe or genal area, and ala which reaches about 60% of the way across the genal area, compared with 70% in case of H. oudris . Harpes supercilium has more pronounced pitting on the genal area, a short (tr.) eye ridge, and genal roll perforations are smaller than those on the brim rather than being the same size. Also, its brim slopes anteriorly more steeply and it has a brim width ratio of around 0.55, compared to 0.80 for H. oudris . In lateral view, its internal rim has a much less strong wave-like profile and the distal ends of the prolongation are not so strongly upturned.

H. supercilium is also similar to H. boudibensis but differs by having glabellar furrows at S2-S4, a distinct preglabellar furrow, a well-defined eye ridge, a genal area with faint caeca and a brim with light caeca reaching across it. Also, the thorax of H. supercilium has around 20 segements, 5 fewer than that of H. boudibensis . H. boudibensis has no furrows at S2-S4, a very shallow preglabellar furrow with the anterior boss joined to the glabella, no eye ridge and no caeca on the genal area or the brim.

Genus Lioharpes Whittington, 1950a

Type species. Harpes venulosusus Hawle & Corda, 1847 , Pragian , from the Koněprusy Limestones, Koněprusy, Czech Republic

Emended diagnosis. Cephalon ovoid. Occipital furrow broad (sag.), equal to or wider (exsag.) than posterior border. Width (tr.) of posterior border between 31% to 40% of occipital ring width (tr.). Genal area moderately broad, inner margin of fringe across anterior of genal area straight and Eye lobes with three lenses each. Tubercles on occipital ring, palpebral lobes and dorsal surface of internal rim. Girder narrow (sag. And exsag.), 1.5% to 2.2% of genicranium width (tr.). Brim width ratio between 0.70 and 0.85. Extension of girder meeting internal rim halfway down prolongation. Thorax with 20 to 24 thoracic segments. Pleural furrows shallow and narrow, and distal ends of pleurae rounded.

Discussion. Lioharpes species are similar to Harpes but differ in having smaller (tr.) alae, broader genal areas with faint caeca, less inflated eye lobes set away from inner margin of the fringe. In addition, brims are concave to straight and do not steepen so strongly on the prolongations. Their brim width ratio is distinctly higher.

The cladogram for Lioharpes is shown in Figs 9 and 10a . and shows that Lioharpes species are divided into two groups which are separate from the type species. The type species is from Czech Republic then partial covered by northern part of the Rheic Ocean, and two groups from the south part of the Rheic Ocean, now North Africa and in particular Morocco. The first group includes L. ammari n. sp., L. saredrar , n. sp. and L. scopulum n. sp., and the second group, L. galea n. sp., L. cf. galea , L. morocconensis n. sp. and L. cf. morocconensis . The type species and Group 1 species have brim extensions that steepen along the proximal edges of the prolongations only, while the whole of the brim extensions steepen on Group 2 species. Also, the eye lobes of Group 1 have three lenses while those of Group 3 have only two. The number of eye lenses of the type species is not known. Group 1 species are upper Pragian and Group 2 are Emsian.

On the basis of the cladistic study, L hastatus has been reassigned to Pinnuloharpes n. gen; and L. vectori Doubrava, 1991 , from the Silurian, to Bohemoharpes s. l.. Lioharpes montagnei ( Hawle & Corda, 1847) , L. wendti Feist, 2018 and L. perneri ( Prantl & Přibyl, 1954) are transferred to Fritchaspis , and Lioharpes sculptus ( Hawle & Corda, 1847) and L. venetus ( Gortani, 1915) to Maghroharpes n. gen.

Harpes polaris ( Maksimova, 1977) and Kielania superna ( Maksimova, 1979) have been reassigned to Lioharpes . s.l.. In the case of Kielania superna , the illustrated material provides little data, so its reassignment should be treated with caution, especially as its age is upper Eifelian rather than middle Pragian to upper Emsian, from which the other Lioharpes species date.

Lioharpes crasimargo ( Novák, 1890) is in a sister relationship with Lioharpes and Maghroharpes, Its position, however, is not well enough supported to justify the erection of a new genus and as a result the species is designated Gen. Indet..

Lioharpes species included in the study and are shown together with their interspecies relationships in Fig. 10a. L . bischofi ( Roemer, 1852), not included in the study remains pro tem in the genus. The range of the Lioharpes is from middle Pragian to upper Eifelian and “ Lioharpes ” from upper Pragian to Emsian.

Figures

PLATE 3. A–K Harpes supercilium n. sp., from horizon 5, Section 2 (Fig. 7), El Otfal Formation, Eifelian, Jbel Issoumour (Fig. 2B, Map 7). A–F, articulated dorsal exoskeleton, paratype, NHMUK It 29251 (site 3). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations, E, lateral view of glabella muscle insertion scars and F, lateral view of eye lobe. G–K, dorsal exoskeleton thorax enrolled, holotype, NHMUK It 29252 (site 10). G, dorsal view, H, anterior view, I, lateral view, J, dorsal view of brim perforations, K, lateral view of eye lobe. L–P Harpes supercilium n. sp., from horizon 8, Section 1 (Fig. 6), El Otfal Formation, Eifelian, Jbel Ou-Driss (Fig. 2B, Map 4, site 24), dorsal exoskeleton of cephalon, paratype, NHMUK It 29250. L, dorsal, M, anterior and N, lateral view. O, lateral view of muscle insertion scars on glabella, P, lateral view of eye lobe. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 4. A–D Harpes supercilium n. sp., partial dorsal exoskeleton, paratype, NHMUK It 29248, horizon 10, Section 1 (Fig. 6), El Otfal Formation, Eifelian, Jbel Ou-Driss (Fig. 2B, Map 4, site 14). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations. E–K Harpes sphenocephalus n. sp., dorsal exoskeleton and partial thorax enrolled, holotype, NHMUK It 29246, horizon 1, Section 1 (Fig. 6), Er Remlia Formation, lower Emsian, Jbel Ou-Driss (Fig. 2B, Map 4, site 15). E, dorsal, F, anterior and G, lateral view. H, dorsal view of brim perforations, I, anterior view of genal roll, J, anterior-dorsal view of perforations across brim, exsag. K, lateral view of eye lenses. L–O Harpes cf. sphenocephalus, partial dorsal exoskeleton, NHMUK It 29247, “Cherurid Couche”, Er Remlia Formation, lower Emsian Jbel Issoumour (Fig. 2B, Map 7, site 18). L, dorsal, M, anterior and N, lateral view. O, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.

FIGURE 6. Section 1 Jbel Ou-Driss

FIGURE 7. Section 2 Jbel Issoumour

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

FIGURE 10a. Lioharpes and Maghroharpes from tree 1 of 60 found using seed 7