Maghroharpes laatchanensis, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 80-81

Maghroharpes laatchanensis n. sp.

Plate 21A–O

Diagnosis. Genicranium very narrow. Glabella narrow, with mildly carinate crest and convex flanks. Axial furrows do not cross junction of ala and L1, and converge strongly anteriorly. Preglabellar furrow indistinct and preglabellar field absent. Genal area narrow, width (tr.) around half the length (exsag.). Alae also narrow (tr.) and genal roll moderately sloping (sag.). Brim strongly concave and not steepening on prolongations. Thorax with over 21 segments.

Etymology. Named after the type locality Oued el Atchane.

Material and occurrence. Holotype: NHMUK It 29308, Pl. 21A–G , from “ Kolihapeltis Couche ” ( McKellar & Chatterton, 2009, text fig. 5D), Ihandar Formation, Oued el Atchane, west Jbel Oufaten ( Fig. 2B, Map 8, site 15); an articulated dorsal exoskeleton with pygidium, enrolled . Paratypes: NHMUK It 29307 and NHMUK It 29306, Pl. 21H–K, L–O , respectively, type locality and horizon ( Fig. 2B, Map 8, site 13 and site 3, respectively), dorsal exoskeletons of cephala only.

Other material: Maghroharpes cf. 1 laatchanensis : NHMUK It 29311, Pl. 22A–E , from Pragian couche below Tizzinydo, Ihandar Formation, Jbel el Oftal ( Fig. 2B, Map 9, site 8), dorsal exoskeleton of cephalon only; M. cf. 2 laatchanensis, NHMUK It 29310 (1) and NHMUK It 29310 (2), Pl. 25A–G , from Merzâ Akhsai Formation?, Pragian, Foum Zguid ( Fig. 2B, Map 1, site 4), dorsal exoskeleton of cephalon only, and a dorsal exoskeleton of cephalon with disarticulated thorax.

Description. Cephalon sub oval, widest at alae. Genicranium widest at posterior border and very narrow, length (sag.) around 90% of width (tr.). Glabella not inset; narrow, with width (tr.) at S1 of around 65% of glabellar length (sag.) anterior to S0; mildly carinate, with convex flanks; and finely pitted. S1 effaced, before curving forward near crest, and no furrows at S2, S3 or S4. Axial furrow convex, tapering strongly anteriorly (angle of convergence just over 150). Preglabellar furrow shallow, and straight in anterior view. Occipital furrow deep and in dorsal view, medially straight. Occipital ring same width (sag.) as posterior border, without ornamental tubercles and in lateral view, lower than glabella anterior to S0. Occipital node moderately inflated. L1 inflated, alae small (tr. and exsag.) and laterally directed. Alar furrow deep, and axial furrow not crossing junction of ala and L1. Posterior border short (tr.), 20% of occipital ring width (tr.). No preglabellar field.

Genal area narrow (tr.), just under 50% of length (exsag.), finely pitted and with no caeca or tubercles. Eye lobes reniform; inflated and small (exsag.), under 30% of width (tr.) of glabella at S1; located close to internal margin of fringe; each lobe has three lenses, anterior and posterior oval lenses approximately the same size and small central subcircular lens located high up between the two larger lenses. Eye ridge broad, short and not well-defined, and no genal ridge. Inner margin of fringe across anterior of genal areas convex. Anterior boss barely inflated, reaches down to girder. Genal roll gently sloping anteriorly (≈ 450), more steeply laterally (≈ 700). In lateral view, fringe on genal roll narrowing strongly posteriorly. Genal roll with caeca and perforations same size as those on brim, except for row of larger perforations above girder and across anterior boss, where internal margin of fringe crosses it. Girder wide (sag.), ≈ 3% of width (tr.) of genicranium.

Brim concave, moderately wide (sag.), ≈ 34.0% of cephalic length (sag.) and sloping at ≈ 110. Brim width ratio 0.91. Standardised brim perforation very fine, ≈90 μm, and light caeca across brim. Rim stout with no sculpture on dorsal surface and marginal band near vertical, concave with tubercles and ridge at top and bottom. Prolongations (exsag.) 80% of cephalic length. Internal and external rims curving adaxially posteriorly. Internal rim with concave profile in lateral view, extension of girder meets rim nearly halfway down prolongation and it has tubercles on dorsal surface. Brim not steepening on prolongations. Genal spine short.

Thorax with more than 21 segments. Axis tapering quite strongly posteriorly. No pitting or tubercles on axial rings, and pleurae lengthening to compensate for narrowing of axes until 5 th segment. Pleurae strongly tapering, width (tr.) of inner portion of smallest being under 40% of longest. Pleural furrows narrow, deep and V-shaped. Outer portion, set at an angle to inner portion, curves anteriorly, terminating in a point ( Pl. 21F ).

Remarks. Maghroharpes laatchanensis has a slightly wider girder than other Maghroharpes species and its brim does not steepen along the proximal edge of the prolongations. It otherwise has all the diagnostic characters of its genus shown in Table 5b.

Maghroharpes laatchanensis differs from M. hammii in having: a genicranium and glabella which are 25% and 15% narrower, respectively; a carinate glabella which is more tapered anteriorly; axial furrows which do not cross the junction of alae and L1; a shallower preglabellar furrow, which in anterior view is straight and not bowed up as is that of M. hammii ; an occipital ring that is not medially broadened and lower in lateral view than glabella anterior to S0, rather than being the same height; no preglabellar field; its genal area around 10% narrower than that of M. hammii ; its eyes lobes reniform rather than oval; its eye ridge shorter (tr.) and not as well defined as that of M. hammii ; its boss less inflated; a genal roll that is less steeply-sloping (sag.); a slightly wider girder (sag.); an inner fringe that in lateral view narrows more strongly posteriorly; a brim which is 12% wider (sag.); and prolongations that are slightly longer (exsag.) relative to the cephalic length (sag.); a thorax with more than 21 thoracic segments ( M. hammii has at least 20); pleural furrows that are narrower (exsag.) and more V-shaped than U-shaped; and pleurae that lengthen (tr.) sufficiently, anteriorly, to compensate for the narrowing of axial ring but not to increase the overall width (tr.) of the thorax.

Maghroharpes cf.2 laatchanensis NHMUK It 29310 (1 and 2) ( Pl. 25A–G ) is very similar to M. laatchanensis but has a broader genicranium, a glabella crest that is rounded and not carinate, a shallower but wider occipital furrow and an occipital ring that is higher than glabella anterior to S0, rather than lower. Also, M. cf. laatchanensis has a shallower alar furrow; a genal roll that is less strongly sloping, anteriorly and laterally; no caeca on the genal roll or the brim; and internal rims that are subparallel in dorsal view, rather than curving adaxially.

Specimen NHMUK It 29311 of M. cf. 1 laatchanensis ( Pl. 22A–E ) differs from M. laatchanensis in having: a broader (sag.) brim and genicranium (tr.); a broader glabella with a more rounded crest; a lower brim width ratio; shorter prolongations; narrow preglabellar field; and a row of seven tubercles across (tr.) occipital ring behind occipital node. There are no other tubercles on the ring.

Figures

PLATE 21. A–O Maghroharpes laatchanensis n. sp., from Ihandar Formation, Pragian. A–G dorsal exoskeleton pygidium enrolled, holotype, NHMUK It 29308, from “Kolihapeltis Couche”,Oued el Atchane Jbel Oufatene (Fig. 2B, Map 8, site 15). A, dorsal, B, anterior, C, posterior and D, lateral view. E, dorsal view of brim perforations and F, lateral view of axial rings and pleurae. H–K dorsal exoskeleton with pygidium missing, paratype, NHMUK It 29307 from type locality (Fig. 2B, Map 8, site 13). H, dorsal, I, anterior and J, lateral view. K, dorsal view of brim perforations. L–O dorsal exoskeleton with pygidium disarticulated, paratype, NHMUK It 29306, from type locality (Fig. 2B, Map 8, site 3). L, dorsal, M, anterior, N, lateral and O, posterior view. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 22. A–E Maghroharpes cf. 1 laatchanensis, Ihandar Formation, Pragian, Jbel el Otfal (Fig. 2B, Map 9, site 8), dorsal exoskeleton of partial cephalon, NHMUK It 29311. A, dorsal, B, anterior and C, lateral view. D and E, dorsal view of brim perforations and occipital node and tubercles, respectively. F–M Maghroharpes aff.1 minutipunctus, Boutiskaoine Formation? lower Emsian. F–J dorsal exoskeleton of partial cephalon, NHMUK It 29322, Jbel Ou-Driss (North) (Fig. 2B, Map 4, site 7). F, dorsal, G, anterior and H, lateral view. I, lateral and J, dorsal view of eye lobe. K–M dorsal exoskeleton of partial cephalon, paratype, NHMUK It 29323, Boutiskaouine Formation, lower Emsian, Ahware (Fig. 2B, Map 9, site 13). K, L and M, dorsal view of cephalon, brim perforations and eye lobe, respectively. N–Q Maghroharpes aff. 2 minutipunctus, Ihandar Formation Jbel Ou-Driss (West) (Fig. 2B, Map 4, site 20), dorsal exoskeleton of partial cephalon, NHMUK It 29324. N, dorsal, O, lateral and P, anterior view. Q, dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 25 A–G Maghroharpes cf. 2 laatchanensis, Merzâ Akhsai Formation?, Pragian, Foum Zguid. A–D dorsal exoskeleton of cephalon only, NHMUK It 29310 (i), from Foum Zguid (Fig. 2A, Map 1, site 4). A, dorsal, B, lateral and C, anterior view. D, dorsal view of brim perforations. E–G dorsal exoskeleton of cephalon and disarticulated thorax, NHMUK It 29310 (ii), on the same plate as NHMUK It 29310 (i). E, dorsal, F, anterior and G, lateral view. H Maghroharpes oufatenensis n. sp., from coral at top of Pragian, Ihandar Formation, Oued el Atchane, Jbel Oufatene (Fig. 2B, Map 8, site 2), 9 cephala only, paratypes, NHMUK It 29318 (1 to 9), dorsal view of cephala. Scale bars shown represent 1 cm unless otherwise indicated.