Lioharpes ammari, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 58-59

Lioharpes ammari n. sp.

Plates 12G–M , 13A–J

Diagnosis. Glabella is conical, carinate and with tectiform flanks and tubercles along crest. S1 short and shallow. Eye lobes inflated, tall, subcircular and with two eye lenses each. Brim is wide (sag.) and steepens strongly on prolongations. Brim width ratio is around 0.70. In lateral view, internal rim nearly horizontal with slightly wave-like profile. Pleural furrows narrow and well defined.

Etymology. For Ammar Ait Hssain, a trilobite worker and preparator who prepared, together with his brother Hammi, much of the material presented herein.

Material and occurrence. Holotype: NHMUK It 29263, Pl. 12G–M , from an upper Emsian horizon, Tazoulait Formation, north flank of Jbel Ou-Driss ( Fig. 2B, Map 4, site 9), dorsal exoskeleton with pygidium enrolled . Paratype: NHMUK It 29264, Pl. 13A–E , from horizon 2, Section 1 ( Fig. 6 ), Tazoulait Formation , upper Emsian , South flank of Jbel Ou-Driss ( Fig. 2B, Map 4, site 12), dorsal exoskeleton with pygidium missing ; Paratypes: NHMUK It 29265 (1), Pl. 13F–H , and NHMUK It 29265 (2), Pl. 13I–J , from same location and horizon as NHMUK It 29264 (site 13). NHMUK It 29265 (1), dorsal exoskeleton of a partial cephalon, and NHMUK It 29265 (2), a ventral exoskeleton of upper lamella.

Other material: Lioharpes ammari ? (meraspis / early holaspid), NHMUK It 29266, Pl. 53A–F , from the type horizon and location, north flank of Jbel Ou-Driss ( Fig. 2B, Map 4, site 25) .

Description. Cephalon widest at midpoint between eyes and alae, genicranium broad (tr.) with width about 1.4 x length (sag.) and widest at posterior border. Glabella anterior to S0 carinate, with pronounced tubercles along crest and broad with width (tr.) over 75% of length (sag,). S1 slanting posteriorly, not reaching halfway up flank of glabella, no muscle insertion furrows at S2, S3, S4. Axial furrows convex, converging at around 170 to axis and not crossing junction between F1 and ala. Preglabellar furrow shallow and straight (tr.) in anterior view. Occipital furrow deep, straight (tr.) and medially broader (sag.) than posterior border (exsag.). Occipital ring same width (sag.) as posterior border (exsag.), higher than crest of glabella in lateral view and with pronounced tubercles on dorsal surface. Occipital node large and strongly inflated. L1 inflated, alae laterally directed, large at over 30% of width (tr.) of glabella at S1 and over 85% of length (exsag.). Alar furrow shallow and alar depression present. Posterior border short width (tr.), just under 30% of width of occipital ring (tr.) and preglabellar genal area narrow.

Genal area moderately broad with width (tr.) over 60% length (exsag.). Eye lobes strongly inflated, tall, oval in dorsal view, tubercles on dorsal surface and with two eye lenses. Eye lenses of about equal size and elongated, recumbent rectangles with rounded corners in shape ( Pl. 12K ). Eye lobes close to internal margin of fringe; eye location ratio over 0.80. No eye ridge or genal ridge. Anterior boss barely inflated but reaching down to weak girder kink. Genal roll sloping gently, at just under 500 anteriorly and about 550 laterally. Row of large perforations above girder and across anterior boss at internal margin of fringe. Above row of large perforations at girder, perforations smaller than those on brim and decrease in size upwards away from girder. Genal roll without caeca.

Brim sloping moderately at over 100, concave (sag.) straight laterally and width (sag.) over 35% of cephalic length (sag.). Brim width ratio 0.70 and standardised brim perforations moderately fine at around 140μm with larger row of perforations at distal and proximal edges. Light caeca reaching across brim. External rim stout with a few scattered fine tubercles on dorsal surface. Marginal band near vertical and without tubercles. Brim steepens quickly to near vertical on prolongations.

Prolongations moderately short (exsag.), around 80% of cephalic length (sag.). Internal and external rims curving adaxially posteriorly and internal rims with weak wave-like profile in lateral view. Extension of girder meeting internal rim about 45% of way down prolongation. Tubercles on dorsal surface of internal rim and genal spine short, under 10% length (exsag.) of prolongation.

Thorax with 20 segments and axis tapering posteriorly with width (tr.) of last axial ring being under 40% of first.

Remarks. Lioharpes ammari lacks one of the diagnostic characters of its genus as shown in Table 5a: it has two eye lenses per eye lobe, not three.

Lioharpes ammari sister species is L. scopulum and differs in that L. ammari has: a broader genicranium and glabella; axial furrows that converge more strongly; a broader occipital furrow; larger alae (tr. and exsag.); eye lobes that are more strongly inflated and have two lenses each; no caeca on the genal roll; and internal rims on the prolongations that have a weak wave-like profile in lateral view.

Lioharpes ammari is similar to certain Pinnuloharpes species and in particular P. haustrum . Lioharpes ammari , however, has a number of differences, the most important of which are: a wider (tr.) genicranium and glabella; a glabella that is more tapered anteriorly and has tubercles along the crest; a wider occipital furrow and an occipital ring that is higher than the glabella anterior to S0. Lioharpes ammari also has an axial furrow that does not cross the junction of L1 with ala; deeper alar furrows; taller eye lobes that are set much closer to the inner margin of fringe; there is no genal ridge or eye ridge, both of which are just visible on Pinnuloharpes haustrum ; inner margin of fringe across the anterior of genal area is straight, not concave; and the genal roll is not so steeply-sloping. Brim of Lioharpes ammari is wider (sag.), steeper-sloping and with a higher brim width ratio at 0.70, rather than 0.56 in the case of Pinnuloharpes haustrum . Internal rim and external meet at the end of prolongations, whereas those of P. haustrum meet and run together for a short distance posteriorly before joining. The genal spine of Lioharpes ammari is shorter and there are no larger perforations under the internal rim. The thorax of L. ammari has a more tapered axis, lacks pitting on the axial rings and pleurae, and the distal ends of the pleurae are rounded, not pointed.

The meraspid or perhaps early holaspid ( Pl. 53A–F ), coming as it does from the type horizon, is most likely L. ammari . It has the same brim width ratio and other morphological features. However, the eye lobes are not as tall, the glabella is not carinated and the tubercles on the glabella and eye lobes appear not to be so well developed. It may be that some of these features have been lost in the preparation of such a small specimen (cephalon sag. length = 7.5 mm) or that they may have developed in later instars.

Figures

FIGURE 6. Section 1 Jbel Ou-Driss

PLATE 12. A–F Lioharpes cf. morocconensis, from a lower Emsian horizon, Boutiskaouine Formation, 28.3 km SSW of Rissani (Fig. 2B, Map 14, site 10), dorsal exoskeleton of partial cephalon, NHMUK It 29273. A, dorsal, B, anterior and C and D, lateral view. E, lateral view of eye lobe and F, dorsal view of brim perforation. G–M Lioharpes ammari n. sp., from an upper Emsian horizon, Tazoulait Formation, North flank of Jbel Ou-Driss (Fig. 2B, Map 4, site 9), dorsal exoskeleton with pygidium enrolled, holotype, NHMUK It 29263. G, dorsal, H, anterior and I, lateral view. J and K, dorsal and lateral views, respectively, of eye lobe. L and M, dorsal view of brim perforations and exterior rim, respectively. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 13. A–J Lioharpes ammari n. sp., from horizon 2, Section 1 (Fig. 6), Tazoulait Formation, upper Emisian, South flank of Jbel Ou-Driss (Fig. 2B, Map 4). A–E dorsal exoskeleton, pygidium missing, paratype, NHMUK It 29264 (site 12).A, dorsal, B, lateral and C, anterior view. D, lateral view of eye lobe and E, dorsal view of brim perforations. F–H dorsal exoskeleton of partial cephalon, paratype, NHMUK It 29265 (1) (site 13). F, dorsal, G, lateral and H, anterior view. I–J ventral exoskeleton of a partial upper lamella, paratype, NHMUK It 29265 (2) (site 13). I, ventral view and J, lateral view of ventral surface. K–O Pinnuloharpes igaouii n. sp., from a horizon 20 metres down slope from type horizon of Lioharpes ammari n. sp. Boutiskaouine Formation?, lower Emsian North flank of Jbel Ou-Driss (Fig. 2B Map 4 site 6). Dorsal exoskeleton of cephalon only, paratype NHMUK it 29267. K dorsal, L anterior and M lateral view. N lateral view of eye lobe and O dorsal view of brim perforations. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 53. A–F Lioharpes ammari n. sp. (?), a small holaspid or late meraspid from an upper Emsian horizon, Tazoulait Formation, North flank of Jbel Ou-Driss (Fig. 2B, Map 4, site 25), dorsal exoskeleton of partial cephalon, NHMUK It 29266. A, dorsal view, B anterior view and C and D lateral views. E, dorsal view of brim perforations and F, laterodorsal view of eye lobe. G–L Eoharpes beningensis (Barrande 1872), from Dobrotivá beds, Llandeilo, Lower Ordovician Svatá Dobrovtivá central Bohemia. G–H partial dorsal exoskeleton, Museum of Comparative Zoology Harvard University, IP 173331. G dorsal view and H, lateral view. I–L partial dorsal exoskeleton, Museum of Comparative Zoology Harvard University, IP 173316. I, dorsal view and L, lateral view. J, dorsal view of brim perforations and K, lateral view of eye lobe and caeca on genal area. Scale bars shown represent 1 cm unless otherwise indicated.