Eskoharpes sicarius, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 68-70

Eskoharpes sicarius n. sp.

Plates 33A–K , 34A–I

Diagnosis. Cephalon ovoid with widest point across or just anterior to alae. Brim strongly convex, less steeply-sloping than genal roll; S1 furrow narrow and deeply incised.Alae anterolaterally directed, eyes lobes small (exsag.) and reniform. Course of inner margin of fringe across anterior of genal area concave. Brim not steepening on prolongations and inner rims subparallel. Prolongations long, pointed, dagger-like in shape, with long terminal spine carried unusually on upper lamella ( Pl. 34G ).

Etymology. Named after sicarius, a “dagger-man” (a zealot assassin who used a dagger (sica)), for the species’ long, pointed, dagger-like prolongations and genal spines.

Material and occurrence. Material comprises 7 dorsal exoskeletons and one lower lamella ( Pl. 33G ), from the horizon where ammonoids (gephuroceratid family ( Frech, 1897)) are mined, lower Frasnian, Achguig Group, Bouia, 7 km S.E. of Jorf ( Fig. 2B, Map 6, site 5). Holotype: NHMUK It 29256 (1), Pl. 33D–F, a partially articulated exoskeleton . Paratypes: NHMUK It 29256 (6), Pl. 33A–C, a partial cephalon ; NHMUK It 29256 (8), Pl. 33H, a partial cephalon and thorax; NHMUK It 29256 (2), Pl. 34A–E , dorsal exoskeleton of partial cephalon; NHMUK It 29256 (5), Pl. 34F–G , partial cephalon; NHMUK It 29256 (4), Pl. 34H , partial cephalon and thorax; NHMUK It 29256 (7), Pl. 34I , partial cephalon; NHMUK It 29256 (3), Pl. 33I–K, a partial lower lamella.

Description. Cephalon ovoid, and genicranium narrow and moderately vaulted. Both widest at alae. Glabella narrow, width (tr.) around 60% of cephalic length (sag.). L1 not inflated and S1 furrow deep, narrow and slanting posteriorly to reach two thirds of way up flank of glabella, curving slightly anteriorly and becoming effaced. Muscle insertion furrows at S2, S3 and S4 not visible. Axial furrows straight and converging weakly anteriorly. Preglabellar furrow well defined and straight in anterior view. Occipital ring broadened medially and in lateral view, lower than glabella anterior to S0. Presence or absence of occipital node not known.Alae, well defined by shallow alar furrows, are close to subcircular, small (tr.) and anterolaterally directed, to reach a third of way across genal area.

Genal area broad to very broad, gently convex and covered by dense faint caeca and fine pitting. Eye lobes are reniform, large (exsag.) and located longitudinally just behind preglabellar furrow and laterally, halfway between inner margin of fringe and axial furrow. Each eye lobe has two lenses. Eye ridges not well defined, moderately wide (ex., sag.) and reaching into axial furrow. Preglabellar field wide (sag.) and course of inner margin of fringe across anterior of genal areas mildly concave. Anterior boss barely inflated, reaching down to very weak girder kink. Genal roll gently sloping anteriorly, moderately steep laterally and in lateral view, narrows very strongly posterolaterally. Perforations on genal roll are smaller than on brim and of uniform size except for row of slightly larger perforations above girder. Genal roll lacks caeca. Girder moderately narrow.

Brim strongly convex, moderately wide (sag.) (32% of cephalic length (sag.)) and steeply sloping at 300. Brim width ratio is just over 0.85. Perforations on standardized brim are moderately large, between 160 μm and 190 μm in diameter, and at density of around 18 per sq. mm. Both perforation size and density vary considerably between individuals. No caeca on brim and external rim fine and slightly raised with inside edge sloping, dorsal surface rounded and dorsal rim suture close to outside edge. Marginal band narrow and sloping downwards and slightly inwards.

Prolongation (excluding genal spine) nearly same length (exsag.) as cephalon and strongly tapered in lateral view. Girder extending almost horizontally onto prolongations to meet internal rim about one third of way down its length (exsag.). Internal rim slightly concave in lateral view; declining at an angle of around 20°, before flattening out slightly just before meeting with external rim and running short distance with it until the two join at end of prolongation. Terminal spine carried on upper lamella, very long and curved slightly adaxially ( Pl. 34G ). In dorsal view, internal borders run subparallel to each other until near their distal ends, where they curve slightly adaxially. External rims curving gently adaxially.

Thorax with at least 15 segments, with width (tr.) of axial rings and inner portion of pleurae reducing progressively posteriorly, by two thirds and 70%, respectively. Pleural furrow shallow and continuing a little way onto outer portion of pleurae. Outer portion of pleura short, slanting slightly posteriorly from fulcrum and on 8 posterior pleurae, terminating in a rounded end. Outer portion of anterior pleurae terminate in short spine, curving posteriorly.

Pygidium ( Pl. 33F ) short, axis consisting of two segments and a terminal piece. Second axial ring comprises four small tubercles arranged across (tr.) axis. Terminal piece comprises a pair of large tubercles close to, but not at, the margin. On pleural field, first pleural furrow is deep, second much shallower and shorter.

Hypostome not known.

Remarks The glabella of Eskoharpes sicarius is not inset but otherwise the species complies with the other 7 diagnostic characters of its genus as set out in Table 5b. The inter-species variations in key morphological ratios of the paratypes is limited and are shown in Table 6.

Eskoharpes sicarius is similar to Eskoharpes wanndjiana but differs in having: a slightly narrower genicranium; a glabella that is not inset and which has no granulation or pitting anterior to S0; a wider (sag.) and deeper occipital furrow; alar furrows that are well defined, not partially effaced; a genal area with faint fine caeca and pitting but no granulation; more inflated and larger (exsag.) eye lobes; an inner margin of the fringe that is concave across the anterior of the genal area either side of the glabella and not convex; a fringe that, in lateral view, narrows more strongly posteriorly; a brim that is wider (sag.) and has a profile that is convex rather than straight; a finer external rim; longer and broader (tr.) prolongations that, in lateral view, do not curve as strongly adaxially as those of E. wanndjiana and an extension to the girder that meets the internal rim half of the way down the prolongation rather than a third of the way down. Also, the brim of E. sicarius does not steepen on the prolongations while that of E. wanndjiana steepens along its proximal edge.

Eskoharpes sicarius is also similar to the type species Eskoharpes palanasus but differs from it in having: the widest point of the cephalon a little further back at the alae rather than at the midpoint between alae and eye lobes; a slightly narrower genicranium; a glabella that is not inset and which has no granulation or pitting anterior to S0; a narrower and deeper occipital furrow; L1 not inflated; alae narrower and anterolaterally directed and no alar depression present, as there is in, E. palanasus a posterior border that is nearly half the length of that of E. palanasus ; a wider (sag.) preglabellar field; a narrower genal area is narrower with faint fine caeca and pitting, while that of E. palanasus is granulated; larger (exsag.), more elongated eye lobes with 2 eye lenses on their outside flanks, while those of E. palanasus are located more on the dorsal surface of the eye lobe; the inner margin of the fringe concave across the anterior of the genal area either side of the glabella and not straight as in the case of E. palanasus ; no shallow furrow marking the inner margin of the fringe; a wider girder whose brim is more steeply-sloping and convex rather than straight; a finer external rim that lacks sculpture; and internal rims that also lack sculpture and curve adaxially over the whole of their length (exsag.) in dorsal view, rather than being subparallel over the first two thirds.

Genus Maghroharpes n. gen.

Type Species: Maghroharpes hammii n. sp.

From the Ihandar Formation, Pragian,10metres below the “ Dicranurus Couche ”, Oued el Atchane, Jbel Oufatene near Fezzou, Errachidia, Morocco

Diagnosis. Cephalon sub oval, widest (tr.) at alae. Genicranium widest (tr.) at posterior border. Glabella anterior to S0 moderately broad (width (tr.) 0.66 to 0.75 of length (sag.)) and with no furrows at S2, S3 or S4. Alae small (tr.) and well defined, and no alar depression. Eye lobes set close to internal margin of fringe. Inner margin of fringe across anterior of genal area convex. Girder broad (sag.) (>2.3% of width (tr.) of genicranium), meeting internal rim one half or little over one half of way down prolongation. Brim concave, gently sloping with proximal edge steepening slightly on prolongations. Brim width ratio between 0.77 and 0.95. Marginal band concave with ridges top and bottom. 20 to 24 thoracic segments with inner and outer portions of pleurae aligned (tr.).

Etymology. el Maghreb (Arabic meaning “place where the sun sets”) is the name given in pre-modern times by Arab writers to the northern part of Africa, particularly Morocco.

Remarks. Maghroharpes species are very similar to those of its sister genus Lioharpes , but differ in having: cephala that are sub oval and widest at alae, or just anterior thereto, rather than ovoid and widest at the eyes; glabellae anterior to S0 lacking the granulation or tubercles typical of Lioharpes ; genal areas lacking faint caeca; the course of inner margin of fringe across anterior of genal areas convex rather than straight; the anterior boss more inflated; girder kink more pronounced; marginal band concave rather than straight; finer brim perforations; and distal ends of pleurae rounded rather than pointed.

M. rouvillei ( Frech 1887) and M. sculptus ( Hawle & Corda, 1847) have been assigned from Harpes and Lioharpes respectively. All species are included in the study ( Figs 9 , 10a ) and the genus range is from the Pragian to upper Emsian.

The cladogram for Maghroharpes has been partially collapsed in the formation of a consensus ( Fig. 9 ). There is, however, two sister groups, one five species supported by a character state that is a unique unreversed synapomorphy: tubercles and pitting on the palpebral lobes.

Figures

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

PLATE 33. A–K Eskoharpes sicarius n. sp., from the ammonoid mining horizon, Achguig Formation Group, lower Frasnian, Bouia, 7 km SE of Jorf (Fig., 2B, Map 6, site 5). A–C paratype, NHMUK It 29256 (6), dorsal exoskeleton of cephalon. A, dorsal view, B, anterior view and C, lateral view. D–F holotype, NHMUK It 29256 (1), dorsal exoskeleton partial cephalon and thorax, and a complete pygidium. D, dorsal view of whole exoskeleton, E, dorsal view of thorax and pygidium and F, dorsal posterior view of pygidium. G assemblage of partial dorsal exoskeletons of material shown in Figs 43 and 44. H paratype, NHMUK It 29256 (8), partial dorsal exoskeleton of cephalon and thorax, dorsal view. I–K paratype, NHMUK It 29256 (3), dorsal exoskeleton of lower lamella. I, dorsal, J, lateral and K, anterior view. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 34. A–I Eskoharpes sicarius n. sp., from Type horizon, lower Frasnian, Bouia, 7 km SE of Jorf (Fig. 2B, Map 6, site 5). A–E paratype, NHMUK it 29256 (2), dorsal exoskeleton of partial cephalon only. A, dorsal view, B, lateral view, C, anterior view, D, dorsal view of eye lobe and eye ridge and E, anterior dorsal view of brim perforations. F–G paratype, NHMUK it 29256 (5), dorsal exoskeleton partial cephalon. F, dorsal, G, lateral view of posterior of prolongation including genal spine. H paratype, NHMUK it 29256 (4), dorsal exoskeleton of partial cephalon and disarticulated thorax, dorsal view. I paratype, NHMUK it 29256 (1&7), dorsal exoskeleton of partial concealed cephalon, dorsal view. Scale bars shown represent 1 cm unless otherwise indicated.