Helioharpes aougili, Johnson, 2024

Johnson, Robert G., 2024, Devonian Harpetidae from the central and eastern Anti-Atlas, Morocco, Zootaxa 5450 (1), pp. 1-185 : 65-68

Helioharpes aougili n. sp.

Plate 17A–K, M–P

Diagnosis. Cephalon mildly piriform. Genicranium moderately vaulted, glabella more strongly vaulted, tectiform and carinate. Occipital ring in lateral view near vertical. Eye lobes long (exsag.), reniform in shape and eye ridge low and broad. Internal rim slanting abaxially over first 2/3 before curving strongly adaxially. In lateral view, prolongations strongly tapered and external and internal borders converge posteriorly to run adjacent to each other along final third of prolongation. External and internal rim very robust. First five thoracic axial rings with axial tubercle. Pleural furrows narrow (exsag.), deepening posteriorly.

Etymology. Named for the trilobite worker, Youssef Aougil, who found the holotype.

Material and occurrence. Holotype: NHMUK It 29254, Pl. 17A–K , from the “ Basseiarges Couche ”, Tamgoute Bulgan, 11.5 km S.W. of the village of El Jorf, Eifelian ( Fig. 2B, Map 6, site 16), articulated dorsal exoskeleton with pygidium folded under . Paratype: NHMUK It 29255, Pl. 17M–P , from the type locality and horizon ( Fig. 2B, Map 6, site 17), dorsal exoskeleton of cephalon only .

Description. Cephalon piriform in outline, length (sag.) around 65% of width (tr.) and length (exsag.) of prolongations just under cephalon length (sag.). Glabella length (sag.) 45% of cephalic length(sag.)and subcylindrical in dorsal view, gently tapered anteriorly. Glabella flanks tectiform, crest carinate and in lateral view, anterior gently sloping. S1 barely rising out of axial furrow, S2, S3 and S4 shallow depressions remaining in axial furrow. Alae reach less than halfway across (tr.) genal area and alar furrows shallow, becoming effaced distally. Occipital ring narrow, not medially broadened and with pronounced occipital node located at edge of occipital furrow. In lateral view, near vertical and higher than glabella anterior to S0. Posterior border furrows are deep and axial furrows moderately deep. No preglabellar field. Genal area gently convex, anteriorly narrow (tr.) but quickly broadening posteriorly. Eye lobe mildly inflated, long (exsag., just under 50% of width (tr.) of glabella at S1), reniform and located away from inner margin of fringe ( Pl. 17A, J ). Eye location ratio 0.73. Each eye lobe with two lenses, one orientated laterally, the other anterior laterally, and ill-defined eye ridge which runs from posterior edge of eye tubercle, slanting adaxially forward into axial furrow. Glabella and genal area covered by very fine disjointed caeca-like sculpture ( Pl. 17I ). Genal area sparsely covered by fine pitting. Posterior border short, just under 40% of occipital ring width (tr.).

Genal roll convex, broad anteriorly (sag., exsag.) but narrowing (tr.) posteriorly to about 50% of its sagittal width at S0. Anterior slope of genal roll about 400 but laterally steeping to about 500. Anterior boss gently convex (sag. and tr.), deflating as it reaches down from preglabellar furrow to girder. Preaxial furrows shallow and subparallel. Perforations on genal roll fine ( Pl. 17E, F ), posteriorly increasing in size as they extend on to prolongations. Short row of larger perforations at inner margin of fringe where it crosses anterior boss. Girder narrow and girder kink barely discernible.

Brim width (sag.) is 33% of cephalic length (sag.). Brim flat, slightly sloping downwards and outwards. Brim width ratio 0.91. Dorsal surface covered with strongly developed caeca in a polygonal net-like structure. Perforations on brim are fine and densely packed in spaces between caeca ( Pl. 17H ). Row of much larger perforations at distal edge of brim but not at proximal edge. Standardised perforation density in central part of brim is around 25 per sq. mm. External rim is robust, dorsal surface slopes outwards and is covered with fine granules. Dorsal rim suture is pronounced and located over two thirds of way across dorsal surface towards distal edge of rim. Marginal band near vertical, with slight lip on dorsal edge and granular sculpture.

Length of prolongations (exsag.) nearly same as length of cephalon (sag.). In lateral view, prolongations strongly tapered, their height at midpoint being just half their height at junction with posterior border. In dorsal view, external rim slants adaxially until about two thirds of way down its length (exsag.), where it meets internal rim, narrows and flexes slightly abaxially. Internal rim curves adaxially posteriorly from posterior border, before slanting obliquely abaxially to meet with external rim, and then curves adaxially with external rim to end of prolongation where both rims join. Both rims are robust with granulated dorsal surfaces. Brim on prolongation barely steepens. Girder extends onto prolongations but quickly slopes up to meet internal rim, close to junction with posterior border. Brim sculpture on prolongations similar to that on rest of brim, however, row of larger perforations runs beside the two rims and merges into single line of four perforations where the two rims meet. Prolongations terminate in spine.

Thorax has at least 17 segments. Axial rings narrow (sag.) slightly medially and first five have medial tubercle on anterior edge ( Pl. 17L ), which becomes progressively less inflated posteriorly. Inner portion of pleura of first 7 segments lengthen (tr.) progressively posteriorly slightly more than axial rings narrow (tr.), and on next 10 segments shorten (tr.) progressively posteriorly. Pleural furrows narrow, deepen posteriorly and terminate at start of outer portion of pleurae ( Pl. 17J ). Outer portion of pleurae cylindrical, short and curve sharply downwards ( Pl. 17K ).

Hypostome and pygidium unknown.

Remarks.Unfortunately, the H. perradiatus material presented by Richter & Richter (1943; abb. 2 and taf. 4, figs 12–13) is incomplete, consisting only of a partial cephalon with a damaged brim and the prolongations largely missing. From this, however, it is possible to note that H. perradiatus differs in having smaller eye lobes, a genal area which is broader anteriorly, a longer (tr.) posterior border and an occipital ring that appears not to rise as high as the top of the glabella. Also, the pattern of the caeca on the brim is more radial.

Helioharpes aougili is also quite closely related to H. kayseri , however, H. aougili differs in having: a cephalon widest at eye lobes and not at midpoint between eye lobes and alae; a glabella that has tectiform flanks rather than convex; an occipital ring that is not medially broadened and, in lateral view, near vertical and slightly higher than glabella anterior to S0 (occipital ring of H. kayseri is lower than the glabella anterior to S0); alae anterolaterally rather than laterally directed and alar furrows distally effaced; eye lobes set further from inner margin of fringe; the brim with a straight profile and barely sloping, compared to that of H. kayseri which is convex and sloping at nearly 300; brim width ratio of 0.93 compared with 0.81 for that of H. kayseri ; on the prolongations, the internal rim in dorsal view slanting abaxially from junction of posterior border before curving adaxially, while that of H. kayseri curves adaxially down its entire length (exsag.).

As in the case of H. perradiatus , the H. kayseri material available comprised drawings and a poorly photographed exoskeleton of an incomplete cephalon, so that only the limited number of morphological features compared above could be used.

Genus Declivoharpes (Prantl & Vaněk emend., 1981).

Type species. Harpes dvorcensis praecedens Prantl & Přibyl, 1954 , Lochkovian , from the Radotin Limestones , Černá rokle gorge, Praha-Radotin, Czech Republic. (Refigured Pl. 59A–D )

Emended Diagnosis. Furrow at S1 curves around top of muscle insertion area on glabella. Relatively large and wide (tr.) ala, anterolaterally directed; course of inner margin of fringe across anterior of genal area concave, anterior boss inflated and preaxial furrows converging towards girder. Brim width ratio between 0.66 and 0.75, standardized brim perforations fine (<100µm) and exterior rim with fine granulation

Discussion. Declivoharpes was established in 1981 by Přibyl & Vaněk, as a subgenus of Bohemoharpes and was reduced to a junior synonym by Ebach and McNamara, 2002 when they reassigned B. (Declivoharpes) praecedens , the sole species of the subgenus, to Kielania . The reassignment was on the basis that the strongly raised and gently convex brim and the fineness of brim perforations were more characteristic of Kielania . The brim of Declivoharpes praecedens is in fact slightly concave anteriorly and straight laterally ( Pl. 57 I,H ) and differs from Kielania especially as regards the genal roll which is steeper laterally and inflated anteriorly and has caeca.Also, the inner margin of the fringe is concave across the anterior of the genal areas not convex and the occipital furrow is shallower.

Declivoharpes differs from Harpes , its sister genus, in having: a wider genal area; shallower occipital furrow; an inner margin of the fringe with a course across the anterior of the genal area that is concave rather than convex or straight; has a more inflated anterior boss; a well-defined girder kink; perforations on the genal roll that become gradually smaller away from the girder; and granulation on the outer edge of the exterior rim. The brim width ratio of Harpes is typically lower than that of Declivoharpes species, at between 0.50 and 0.60.

Declivoharpes , a former subgenus of Bohemoharpes , differs from it Bohemoharpes in having a narrower genicranium, wider alae which are anterolaterally directed, a more inflated anterior boss, preaxial furrows that converge towards the girder and a brim that is not concave laterally. Also, the brim width ratio of between 0.65 and 0.75 is lower than that of Bohemoharpes species, which are typically over 0.80 and can be greater than 1.

The type species Declivoharpes praecedens was described clearly by Prantl & Přibyl, 1954, and the author would only make the comment that the cephalon is more ovoid than oval.

The relationship between Declivoharpes and other genera is shown in Figs 9 , 10b . The range of the genus is Lochkovian to Pragian.

Genus Eskoharpes McNamara, Feist & Ebach, 2009

Type species. Eskoharpes palanasus McNamara, Feist & Ebach, 2009 , from linguiformis conodont zone (Frasnian), Calyx Corner, Mc Whae Ridge, Lawford Range , Canning Basin , Western Australia

Emended diagnosis. Glabella inset and narrow, width (tr.) being less than 67% of length (sag.). Preglabellar furrow straight in anterior view. Alae small, posterior border wide (tr.). Fine granulation on glabella, occipital ring and genal area. Inner margin of fringe marked by narrow, faint furrow. Genal roll sloping gently anteriorly, at under 500, more steeply laterally at over 550. Perforations on genal roll smaller than brim perforations. On brim, spaces between perforations strongly inflated. In lateral view, prolongations are strongly tapered, with internal and external rims joining to form long genal spines.

Discussion. The original diagnosis included morphological characters that are widely shared with other genera. The emended diagnosis focuses on features that are less widely shared so as to provide a practical guide for identifications to be made. Apart from the reduction in the number of characters included, the original diagnosis stated “…genal roll steep and convex”. Many of the species do have strongly convex genal rolls, which are steeply sloping where they reach the girder, however, if the average slope is measured by drawing a straight line between inner margin of the fringe and the girder, the slope is gentle.

Based on the results of the cladistic study shown in cladogram ( Fig. 9 ) Globoharpes is made a junior synonym of Eskoharpes . As can be seen E. friendi and E. teicherti , formerly assigned to Globoharpes , are shown at the end of the Eskoharpes tree and if Globoharpes continued to stand Eskoharpes would be paraphyletic. Harpes pruniformis ( Alberti, 1969) and Harpes socialis ( Holzapfel, 1895) are in monophylic relationship with the Eskoharpes species but they there are a significant number of characters that could not be coded from the figures available. Because of the uncertainty that this creates and the fact that H. pruniformis ( Alberti, 1969) and H. socialis ( Holzapfel, 1895) are from the upper Eifelian and Givetian respectively, rather than the Frasnian where all Eskoharpes species come from, H. pruniformis ( Alberti, 1969) and H. socialis ( Holzapfel, 1895) are designated Eskoharpes s. l..

McNamara et al. (2009) observed that the former two Globoharpes species, had a steeply sloping brim a strongly vaulted cephalon similar Kielania and in particular the type species K. waagoni . The brims of K. waagoni and Eskoharpes teichertiI, the former Globoharpes slope at an angle of ≈ 500, the steepest brim angle of any harpetid described so far. Apart from the angle of slope the brims have little else in common. Kielania waagenii ’s brim is barely convex anteriorly and straight laterally, whereas Eskoharpes teicherti is strongly convex anteriorly and convex laterally. Also, Kielania waageni has smaller brim perforations and no caeca whereas the spaces between the brim perforations of Eskoharpes teicherti are inflated. Apart from the steep brims and vaulting E. teicherti , and Kielania wagonii are very dissimilar. McNamara et al. (2009), comparing Globoharpes with Kielania wagonii , stated that “ Globoharpes possess a much smaller glabella, well developed, more incised S1, more pronounced alae a much wider genal roll, eye lobes more anteriorly positioned, the absence of a median glabellar tubercle, the lack of a pronounced occipital spine, and longer prolongations.” The strong cephalic vaulting and steep incline of brim are perhaps good examples of convergent evolution. It may have been that a tall feeding chamber, inferred by the strongly vaulted cephalon and steep brim, proved a useful for Kielania species in the Early Devonian of what is now Czech Republic and Morocco and once again for Globoharpes species in the Late Devonian of the Canning basin, Western Australia.

As can be seen in Fig. 9 the cladistic study shows that the reinstated genus of Fritchaspis is a sister genus to Eskoharpes and has more in common with Eskoharpes than does Kielania . Eskoharpes is quite similar to the genus Fritchaspis but differs from it in having: genicranium widest at alae or between alae and eye lobes, not at posterior border; preglabellar furrow is straight in anterior view and not bowed upwards; granulation on the occipital ring; L1 inflated; no alar depression; the inner margin of fringe marked by a shallow furrow and its course across anterior of genal field either side of glabella is concave, not straight as in the case of Fritchaspis ; higher brim width ratios at above 0.85, rather than below 0.75 in the case of Fritchaspis ; and prolongations around 10% shorter (exsag.).

All species of Eskoharpes have been included in the study and are shown in their interspecies relationships in Figs 9 , 10d . Eskoharpes species are all of Frasnian age except for “E ” pruniformis ( Alberti, 1969) and “ E ” socialis ( Holzapfel, 1895) are from the upper Eifelian and Givetian respectively.

The node between E. teicherti and E. friendi has Jackknife support of 72% and the node between E. guthae and E bolotoni 52%.

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 17. A–K and M–P Helioharpes aougili n. sp., from an Eifelian horizon, El Otfal Formation, Tamgoute Bulgan, 11.6 km SWt of El Jorf (Fig. 2B, Map 6). A–K dorsal exoskeleton, pygidium missing, holotype, NHMUK It 29254 (site 16). A, dorsal, B, anterior and C, lateral view. D, dorsal view of brim proximal to girder across the anterior of genicranium, E, anterior view of perforations on brim and genal roll, F, dorsal view of brim perforations. G and H, lateral and dorsal view of eye lobe, respectively. I, dorsal view of cuticle on glabella and genal area. J and K, lateral and dorsal view of pleurae, respectively. M–P dorsal exoskeleton of cephalon only, paratype, NHMUK It 29255 (site 17). M, dorsal, N, lateral and O, anterior view. P, dorsal view of brim perforation. L, H. perradiatus, dorsal view of brim proximal to girder across the anterior of genicranium (reprint), Richter & Richter, 1943, abb 2. Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 57.A–F Fritchaspis montagnei (Hawle and Corda, 1847) type horizon and locality Acanthopyge Limestones (Eifelian), Koněprusy area, Czech Republic, five dorsal exoskeleton of partial cephala, Museum of Natural History, Prague, syntype Nos L 2996 (one of four syntypes) and L 2990. A–C, L 2996, a partial cephalon, A dorsal view, B anterior view and C lateral view. L 2990, D–F a plate with four partial cephala, D dorsal view, E lateral view of largest cephalon and F dorsal vie of brim perforations. G–J Declivoharpes praecedens by (Prantl and Přibyl 1954,) type horizon and locality Radotín Limestones (Lochkovian), praharadotín (Černá rokle gorge) dorsal exoskeleton of partial cephalon, Museum of Natural History, Prague holotype No. L19103. G dorsal view, H anterior view, I lateral view and J dorsal view of brim perforations. This specimen was illustrated by Prantl and Přibyl (1954, pl. 8 fig.2). Scale bars shown represent 1 cm unless otherwise indicated.

PLATE 59. A–D Helioharpes dvorcensis (Prantl and Přibyl, 1954), type horizon and locality Dvorce Limestones (Pragian), Praha-Podoli (formerly Dvorce), Czech Republic, dorsal exoskeleton of a partial cephalon from the Natural History Museum Prague No. L19105 holotype. A dorsal view, B lateral view, C anterior,view and D dorsal view of brim perforations. This specimen was illustrated by Prantl and Přibyl (1954, pl.8 fig. 5). E –G Declivoharpes novaki (Prantl and Přibyl 1954). Type horizon Prokop Limestone (Pragian), St. Prokop quarry, Praha- Hlubocepy, Czech Republic, dorsal exoskeleton of a partial cephalon from the Natural History Museum Prague holotype No. L6120, E dorsal view of exoskeleton, F anterior view and G lateral view. This specimen was illustrated by Prantl and Přibyl (1954, pl.9 fig. 1). H–L Stoloharpes convexus. (Hawle and Corda 1847) Suchomasty Limestones (Eifelian), Měňany, Czech Republic, dorsal exoskeletons of two partial cephalon from the Natural History Museum Prague Nos L 6138 and L 6139. H, L 6139, dorsal view of exoskeleton. I–L, L 6138, J dorsal view of exoskeleton, K lateral view, L anterior view and I dorsal view of brim perforations. L 6138 and L 6139 were illustrated by Prantl and Přibyl (1954, pl. 9 figs 3 and 4 respectively). Scale bars shown represent 1 cm unless otherwise indicated.