Maghroharpes hammii, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 70-72

Maghroharpes hammii n. sp.

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

Plates 18G–N , 19A–O , 20A–P , 27L–O

Diagnosis. Genicranium broad, glabella subcylindrical, rounded anteriorly and preglabellar furrow well defined. Eye lobes with two lenses, and eye and genal ridges well defined. Whole of inner margin of fringe marked by row of bigger perforations. Anterior boss mildly inflated, genal roll steeply inclined (sag. and tr.) and girder kink Σ-shaped. Brim barely concave and width ratio around 0.95. Fine perforations on brim (around 100µm) and finer on genal roll. Internal rims subparallel. Thorax with 20 segments. Blister-like tubercular granulation on dorsal surfaces of external and internal rims, occipital ring and first 5 axial rings of thorax ( Pls 18G , 19L ).

Etymology. For Hammi Ait H’ssainne who prepared the holotype and much of the material presented in this publication.

Material and occurrence. Holotype: NHMUK It 29292, Pl. 18G–N , from 10 m below the “ Dicranurus Couche ”, Ihandar Formation, Pragian, Oued el Atchane, Jbel Oufatene ( Fig. 2B, Map 8, site 21), a partially articulated dorsal exoskeleton, enrolled with pygidium missing or folded under . Paratype: NHMUK It 29296, Pl. 19A–F ; and Paratype NHMUK It 29295, Pl. 19M–O , from main trilobite ‘couche’ ( Johnson & Fortey, 2012, fig. 2, Section 2, horizon 2, 17.5 m above bottom of section), Ihandar Formation, Pragian, southern flank of Jbel el Mrakib ( Fig. 2B, Map 9, sites 16 and 15 respectively), dorsal exoskeletons with pygidium missing or hidden . Paratype: NHMUK It 29294, Pl. 19G–L , from a Ceratonurus horizon, Ihandar Formation, Pragian, Ahware (South), Iferd Nou Haouar ( Fig. 2B, Map 9, site 12) . Paratypes: NHMUK It 29290, Pl. 20A–D ; NHMUK It 29291, Pl. 20J–M , from 12.5metres below the “ Dicranurus Couche ” ( Johnson and Fortey, 2012, fig. 1, Section 1, 14.5 metres above bottom of section, top horizon of range indicated by “ Harpidae sp. 1”), Ihandar Formation, Pragian, Jbel Oufatene ( Fig. 2B, Map 8, sites 8 and 9 respectively); NHMUK It 29290, dorsal exoskeleton cephalon and disarticulated thorax, and NHMUK It 29291, dorsal exoskeleton of cephalon only. Paratype: NHMUK It 29293 Pl. 20N–P , from a horizon between the “ Dicranurus Couche ” and the “ Kolihapeltis Couche ”, Talhadjate, Oufatene South ( Fig. 2B, Map 8, site 22), dorsal exoskeleton of upper lamella only . Paratype: NHMUK It 29300, Pl. 20E–I , Ihandar Formation , North Zireg ( Fig. 2B, Map 13, site1), dorsal exoskeleton with pygidium enrolled, from a Pragian horizon . Paratype: NHMUK It 29297, Pl. 27L–O , from a horizon some 5 metres below the “ Dicranurus Couche ”, 26 metres above base of the Pragian, Ihandar Formation, Iminwasief ( Fig. 2B, Map 4, site 4), dorsal exoskeleton comprising disarticulated thorax and pygidium .

Other material: M. cf. hammii, NHMUK It 29299 ( Fig. 2B, Map 10, site 6), partial dorsal cephalon from a Pragian horizon, Jbel Rheris and NHMUK It 29298 ( Fig. 2B, Map 4, site 19), a crushed dorsal exoskeleton with pygidium enrolled, from a Pragian horizon east of Jbel Ou-Driss. Other material is not figured herein.

Description. Cephalon sub oval, widest at alae, genicranium broad, width (tr.) 1.4 X length (sag.) and glabella anterior to S0 broad (width at S0 0.70 x length), crest rounded and with fine pitting. L1 inflated and muscle attachment scars S0 and S1 tulip-shaped, reaching over 40% and 60% of way up occipital furrow and flank of glabella, respectively. S2 and S3 appear as dark oval areas rising from axial furrow and S4 as dark line at preglabellar furrow ( Pls 18N , 19F ). Posterior and top of S1 is delineated by very faint hook-like furrow. There are no furrows associated with S2, S3 and S4. Occipital furrow broad and occipital ring medially broadened (sag.). Occipital node on anterior edge of occipital ring, moderately inflated. Occipital ring same height as glabella and carries blister-like tubercles. Alae small (tr.), narrow (width (tr.) 77% of length (exsag.), well defined, parabolic in shape, and are anterolaterally directed to reach nearly 40% across (tr.) genal areas. Alar furrows deep. Connecting L1 to occipital ring small, rounded ridge that crosses S0 where occipital ring begins to broaden (sag. and exsag.). Posterior border short (tr.) and with tubercles.

Dorsal surface of genal area barely convex, with faint caeca and fine pits. Eye location ratio is around 0.90, with eye lobe located on anterolateral slope of genal area at a level one fifth from anterior of glabella. Eye lobe small (exsag.), subcircular, inflated and with two ovoid eye lenses ( Pl. 18K ), latero-anteriorly and latero-posteriorly orientated, respectively. Low transverse eye ridge runs from eye tubercle to meet axial furrow at right angles and, on well preserved specimens, a genal ridge that crosses obliquely onto fringe ( Pl. 18J ). In dorsal view, inner margin of fringe is convex where it crosses (tr.) anterior of genal areas. Anterior boss mildly inflated, extends from preglabellar furrow to Σ-shaped girder kink. Girder moderately wide (sag. and exsag.). Genal roll sloping moderately steeply anteriorly and steeply laterally. Perforations on genal roll are fine, with row of bigger perforations above girder and along inner margin of fringe, which are slightly bigger than those below, becoming much bigger where they cross anterior boss. Caeca well-spaced, forming narrow, subparallel ribbon-like strips, which run down from inner margin of fringe to girder. In lateral view, inner fringe narrows only moderately posteriorly.

Brim slightly concave, sloping gently downwards, width (sag.) around 30% of cephalic length (sag.). Brim width ratio 0.95 +/- 6%. At proximal edge of brim, row of large perforations separated by light caeca, which stretches down from girder and across brim. Standardised perforations on brim, at 100µm, are a little larger than those on central part of genal roll and are moderately densely packed, at around 25 per sq. mm ( Pl. 18G, L ). Row of coarse perforations runs along outside edge of brim. External rim raised and robust, with slightly rounded dorsal surface and dorsal rim suture located at about mid-point on rim. Outside edge of marginal band close to vertical, slightly concave with a ridge top and bottom and fine tubercles.

Prolongations short (exsag.), at around 70% of sagittal cephalic length. External rims on prolongations curve strongly adaxially, while internal rims are subparallel. Internal rim thicker (tr.) in dorsal view than exterior rim. Brim steepens slightly on prolongations, and girder extension meets internal rim about halfway along prolongation. Terminal spine carried on lower lamella, short and slanted slightly adaxially. Perforations on brim and extension of genal roll increase in size posteriorly. Row of pits below girder extend from where girder meets internal rim to near end of prolongation, becoming smaller posteriorly and running just below row of larger pits immediately below internal rim. Small blister-like tubercles present on dorsal surface of internal rim.

Thorax consists of 20 or more segments, widening (tr.) to 5 th segment. Axis strongly tapering. Shortest pleurae (inner portion) one third length (tr.) of longest. Pleural furrows narrow, well defined and shallow. Outer portion of pleurae straight and not offset to inner portion. Fine blister-like tubercles on first four axial rings ( Pl. 19L ).

Hypostome and pygidium not known.

Remarks. Maghroharpes hammii is similar to M. minutipunctus but differs in having: a cephalon that is sub oval rather than ovoid; a slightly broader (tr.) genicranium; a glabella that lacks granules on its dorsal surface; anS1 furrow that slopes backwards but does not curve forward around the top of the muscle insertion area; no muscle insertion furrows at S2, S3, or S4, as there are on the glabella of M. minutipunctus ; a deeper occipital furrow; narrower (tr.) alae; deeper and better-defined alar furrows; a preglabellar field that is only visible in dorsal view and is much narrower than that of M. minutipunctus ; eye lobes with small blister-like tubercles on their dorsal surface and two lenses per eye lobe. not three, an anterior boss that is more strongly inflated, reaching down to a well-defined girder kink, while M. minutipunctus is without a kink although the girder is slightly bowed in anterior view; a genal roll that slopes more steeply; an internal fringe that narrows more posterolaterally in lateral view; perforations on the genal roll that are smaller and more densely packed, except immediately above the girder where there is a row of larger perforations, absent on the genal roll of M. minutipunctus ; a narrower brim (sag.) with slightly larger brim perforations and a brim width ratio (0.88) that is 10% higher than that of M. minutipunctus ; a concave marginal band that has a ridge at the top and bottom and fine tubercles in between, while the marginal band of M. minutipunctus is straight and lacks ridges and tubercles; and internal rims that are much more concave in lateral view.

Maghroharpes hammii is reminiscent of some Bohemoharpes species from the Silurian and, in particular, B. (B.) ungula ( H. ungula Sternberg,1833 ; Pl. 54G ) from the Kopanina Limestone (Ludlow stage), Mt. Dlouhá Hora, Králův Dvůr, Central Bohemia. The cephalic outline and shape of the genicranium and glabella are similar, albeit the cephalon and genicranium of B. (B.) ungula are around 10% wider. Other differences include B. (B.) ungula having an inner margin of the fringe that, in dorsal view, is concave across the anterior of the genicranium rather than convex; thinner rims and posterior border which lack tubercles on their dorsal surfaces. Bohemoharpes ungula has an eye location ratio of 0.65, some 30% less than that of Maghroharpes hammii , and finer and more densely packed perforations on the brim and genal roll.

Variation in the morphological ratios of the M. hammii material figured herein is shown in Table 7. Brim perforation size and density show the greatest variability. There are also other variations, for instance, specimens from Jbel Mrakib (south) have larger muscle insertion scars at S2, S3 and S4 on the glabella. (see Pl. 19F ) compared with those of M. hammi (see Pl. 18N ).

Figures

PLATE 18. A–F Fritchaspis edgecombei n. sp., dorsal exoskeleton of cephalon only, NHMUK It 29224, from “Cherurid Couche”, Er Remlia Formation, lower Emsian, Jbel Issoumour (Fig. 2B, Map 7, site 19). A, dorsal, B, antero-dorsal, C, anterior and D, lateral view. E, dorsal view of brim perforation and F, lateral view of eye lobe. G–N Maghroharpes hammii n. sp., dorsal exoskeleton, thorax enrolled, holotype, NHMUK It 29292, from an horizon below the “Dicranurus Couche”, Ihandar Formation, Pragian, Jbel Oufatene (Fig. 2B, map 8, site 21). G, dorsal, H, anterior, J, lateral and I, posterior view. L, dorsal view of brim perforation, N, lateral view of glabella and muscle insertion scars and M, dorsal view of cuticle on glabella, genal area, ala, occipital ring and posterior border. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 19. A–O Maghroharpes hammii n. sp. A–F dorsal exoskeleton with pygidium enrolled, paratype, NHMUK It 29296, from main trilobite ‘couche’ Ihandar Formation, Pragian, southern flank of Jbel el Mrakib (Fig. 2B, Map 9, site 16). A, dorsal, B, anterior, C, lateral and D, posterior view. E, dorsal view of brim perforations and F, lateral view of muscle insertion scars on glabella (uncoated). G–L dorsal exoskeleton with pygidium enrolled, paratype, NHMUK It 29294, from a Ceratonurus horizon, Ihandar Formation, Pragian, Jbel Remlia (Fig. 2B, Map 9, site 12). G, dorsal, H, anterior and I, lateral view. J, lateral view of eye lobe (uncoated), K, dorsal view of brim perforations, dorsal view of tubercles on axial rings. M–O dorsal exoskeleton with pygidium missing, paratype, NHMUK It 29295, from main trilobite ‘couche’, Ihandar Formation, Pragian, southern flank of Jbel el Mrakib (Fig. 2B, Map 9, site 15). M, dorsal, N, anterior and O, lateral view. P, dorsal view of tubercles on rim. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 20. A–O Maghroharpes hammii n. sp., from Ihandar Formation, Pragian. A–D dorsal exoskeleton, cephalon and disarticulated thorax, paratype, NHMUK It 29290, from Jbel Oufatene (Fig. 2B, Map 8, site 8). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations and F, lateral view of muscle insertion scars on glabella (uncoated). E–I dorsal exoskeleton with pygidium enrolled, paratype, NHMUK It 29300, from North Zireg (Fig. 2B, Map 13, site 1). E, dorsal, F, lateral and G, anterior view. H, dorsal view of brim perforations, I, lateral view of eye lobe. J–M dorsal exoskeleton of cephalon, paratype, NHMUK It 29291, from Jbel Oufatene (Fig. 2B, Map 8, site 9). J, dorsal, K, anterior and L, lateral view. M, dorsal view of brim perforations. N–P upper lamella only, paratype, NHMUK It 29293, from an horizon between the “Dicranurus Couche” and the “Kolihapeltis Couche”, Talhadjate, Jbel Oufatene (Fig. 2B, Map 8, site 22). N, dorsal, O, anterior and P, lateral view. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 27. A–D Maghroharpes ihmadii n. sp., dorsal exoskeleton of cephalon and disarticulated thorax, paratype, NHMUK It 29303, from type horizon and locality, Ihandar Formation, Pragian. Jbel Ou-Driss (Fig. 2B, Map 4, site 18). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations. E–K Maghroharpes cf. ihamadii, dorsal exoskeleton pygidium enrolled, NHMUK It 29304, from “Kolihapeltis Couche”, Ihandar Formation, Pragian, Jbel Oufatene (Fig. 2B, Map 8, site 14). E, dorsal, F, anterior and G, lateral view. H, dorsal and I, lateral view of eye lobe. J and K, dorsal view of brim perforations and pleurae, respectively. L–O Magroharpes hammii, dorsal exoskeleton, thorax and disarticulated pygidium, NHMUK It 29297, from Ihandar Formation, Iminwasief (Fig. 2B, Map 4, site 4). L, dorsaI, M, anterior, N, lateral view. O, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 54. A–D Lioharpes venulosus (Hawle & Corda, 1847); type locality Upper Koněprusy Limestones, (Pragian) Koněprusy, Czech Republic, a dorsal exoskeleton of a partial cephalon, Museum of Natural History, Prague L12545. A dorsal view, B lateral view, C anterior view and D dorsal view of brim perforations. E–H Bohemoharpes buphthalmus (Bouček, 1935). Type locality the horizon with Ananaspis fecunda (Ludlow stage), Dlouhá hora near Beroun, Czech Republic, a dorsal exoskeleton of a partial cephalon, Museum of Natural History, Prague L17145. E, dorsal view, F lateral view, G anterior view and H dorsal view of brim perforations. I–L Bohemoharpes naumanni (Barrande 1852); type horizon and zone Cyrtograptus lundgreni zone (Upper Wenlock) Lodenice near Beroun, Czech Republic; dorsal exoskeleton of a partial cephalon, Museum of Natural History, Prague, lectotype (subsequent designation, Prantl and Přibyl, 1954) L6127, IT 48. I dorsal view, J anterior view, K lateral view and L dorsal view of brim perforations. This specimen was illustrated by Prantl and Přibyl,1954 pl. iv fig. 1 and Ebach and McNamara, 2002 Fig 2A. Scale bars shown represent 1 cm unless otherwise indicated.