Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco)

. Viséan coiled nautiloids from North Africa are only poorly known. From the Mougoui Ayoun, Zrigat and Hamou-Rhanem formations of the eastern Anti-Atlas, we describe coiled nautiloids, which belong to the genera Rineceras , Stroboceras , Temnocheilus , Vestinautilus , Maccoyoceras , Endolobus , Epidomatoceras , Liroceras , Ephippioceras , and Solenochilus . The new species Temnocheilus imazighenorum sp. nov., Temnocheilus aubrechtovae sp. nov., Vestinautilus kesslerae sp. nov., Endolobus rota sp. nov., Epidomatoceras ebbighausenorum sp. nov., Liroceras vermis sp. nov., Liroceras karaouii sp. nov., Ephippioceras pygops sp. nov., Solenochilus lucynae sp. nov. and Solenochilus pohlei sp. nov. are described; six taxa are kept in open nomenclature. The assemblage is composed of the three superfamilies Trigonoceratoidea, Clydonautiloidea and Aipoceratoidea and shows a wide spectrum of conch morphologies, ranging from widely umbilicate compressed forms to involute compact forms, reflecting a broad ecological variation.

Here, we describe some coiled nautiloids from the eastern Anti-Atlas to contribute to the knowledge about the stratigraphic and geographic distribution of these cephalopods during the Carboniferous. These nautiloids, which amount to only about 50 specimens in total, came from Late Viséan strata and represent only a small part of collections of hundreds of cephalopod specimens. Remarkably, remains of cephalopods with orthoconic conchs are similarly rare, in contrast to the Devonian strata of the area (cf. Pohle & Klug 2018).
We do not claim to provide a complete overview of the diversity of Carboniferous coiled nautiloids of the northern Gondwana Shelf, since outcrops of Carboniferous strata are vast in the greater Sahara region. The experience of the field work in the Tafilalt of Morocco showed that only a very low number of newly discovered specimens lead to a remarkable increase in the number of species exhibiting an impressive morphological disparity. The limiting factor in determining the diversity is the rarity of the specimens of coiled nautiloids. Accordingly, future collections will certainly lead to a further increase in the number of species.
-One specimen of Solenochilus lucynae sp. nov. A small suite of specimens from the area east and south-east of Rissani was purchased from Driss Karaoui (Hassilabied). -One specimen of Rineceras sp. 2, one specimen of Stroboceras sp., one specimen of Temnocheilus aubrechtovae sp. nov.,

KORN D. & KLUG C., Early Carboniferous nautiloids from the Anti-Atlas
one specimen of Temnocheilus sp., one specimen of Liroceras karaouii sp. nov., two specimens of Solenochilus pohlei sp. nov. and two specimens of Solenochilus sp.
The description of the specimens follows the terminology of conch, ornament and suture line proposed by Korn (2010) and Klug et al. (2015) for the description of ammonoids (Fig. 3). The terminology of conch geometry used here largely corresponds to that proposed by Teichert (1964). The only differences are in the following terms: umbilical angle or shoulder (= umbilical margin) and umbilical area (= umbilical width).

Fig. 2.
Stratigraphic position of the fossil sites with the nautiloid assemblages described here.

Remarks
The extent and content of genera in the family Trigonoceratidae has been repeatedly debated over the past few decades, and several very different views have been expressed (e.g., Flower & Kummel 1950;Shimansky 1957Shimansky , 1967Kummel 1964;Dzik 1984;Histon 1999). Differences of opinion are partly related to the treatment and evaluation of the poorly understood family Koninckioceratidae Hyatt in Zittel, 1900. In this context, two genera (Temnocheilus M'Coy, 1844and Endolobus Meek & Worthen, 1865 are particularly problematic and have been assigned to different families by different authors. For example, Temnocheilus has been placed in the families Temnocheilidae Mojsisovics, 1902, Koninckioceratidae, andTainoceratidae Hyatt, 1883. However, the great resemblance to Vestinautilus Ryckholt, 1852 and other members of the family Trigonoceratidae suggests that Temnocheilus should also be included in this family.

Diagnosis
Genus of the family Trigonoceratidae with usually discoidal subevolute to evolute conch; whorls detached or slightly in contact; whorl profile elliptical or rounded triangular with broad venter. Conch moderately to rapidly increasing in height with a high coiling rate (WER usually higher than 2.00). Ornament with coarse growth lines and coarse spiral ridges; coarse granulation at the crossing points of growth lines and spiral ridges. Septa without inflexions, rather deeply concave. Suture line with shallow external and lateral lobes. Siphuncle small with subcentral position (after Kummel 1964;Shimansky 1967;emended). depressed whorl profile (ww/wh ~ 1.25) is rounded-trapezoidal with a flattened venter, a broadly rounded ventrolateral shoulder and a broadly rounded umbilical wall. The whorl overlap zone is very small (IZR ~ 0.10).
The fragment shows the well-preserved shell ornament with 14 spiral ridges on each side from the midventer to the umbilical seam; the ridges are irregularly spaced on the venter but almost equally spaced on the ventrolateral margin and umbilical wall. The growth lines, which extend with a deep, rounded V-shaped sinus across the venter, are much finer than the spiral ridges. They are occasionally strengthened to form a conspicuous granulation; at the crossing with the spiral ridges, they form slightly elongate spines.

Description
Specimen PIMUZ 39510 is mostly an internal mould (Fig. 4B), which has a conch diameter of 42.5 mm and is 14 mm wide with an umbilicus 20.5 mm wide (uw/dm ~ 0.40). The body chamber and last three chambers are partly embedded in a sideritic nodule. It has a depressed rounded-triangular whorl profile with flattened venter. Flanks and venter bear longitudinal equidistant ridges (5 on the umbilical wall, 3 to 4 on the flank and 2 between the ventrolateral ridges); a granulation is visible at some places at the crossing points of spiral ridges and growth lines.

Diagnosis
Genus of the family Trigonoceratidae with discoidal, subevolute to evolute conch; whorls slightly embracing, outer whorl may lose contact to the penultimate whorl. Adult conch with a polygonal whorl profile; venter slightly convex, flattened, less often slightly concave, flanks almost flat or irregularly concave, dorsum slightly concave. Conch moderately to rapidly increasing in height with a high coiling rate (WER usually higher than 2.00). Prominent longitudinal keels usually well developed, separated by concave zones. Suture line with small lobes and saddles reflecting keels and longitudinal grooves on the surface of the conch. Siphuncle small with subcentral position between septum centre and venter (after Shimansky 1967;emended).

Included species
A review of the species belonging to Stroboceras has been given by . Species of the genus have been described from the following regions: North America (Dawson 1868;Miller & Garner 1953;Niko & Mapes 2005)

Remarks
For a discussion of the composition and limits of the genus, see .

Description
The single specimen PIMUZ 39512 has a conch diameter of 42 mm and is embedded in a siderite nodule (Fig. 5). Less than a whorl of the evolute conch (uw/dm ~ 0.47 to 0.54) is available for study; this shows an angular and depressed whorl profile (ww/wh ~ 1.40) with flattened, weakly convergent flanks and a flattened, slightly concave venter. The ventrolateral shoulder and umbilical margin are subangular.
There are six longitudinal ridges on the flank, the outer ones forming the umbilical margin and the ventrolateral shoulder, respectively. Additionally, there are two ridges on the outside of each venter, followed by some much finer lines towards the plane of symmetry. A slight granulation is produced on the ridges by the growth lines, which are somewhat reinforced here.

Diagnosis
Genus of the family Trigonoceratidae with discoidal to pachyconic, usually subevolute conch. The first whorl is about 30 mm in diameter with an umbilical foramen about 12 mm wide; the conch is rapidly increasing in height with a high coiling rate (WER usually higher than 2.00). Whorls weakly embracing, their profile triangular with more or less angular umbilical margin. Sculpture with longitudinal tubercles along the ventral margin. Septa usually without inflexions, rather deeply concave. Suture line with shallow ventral and deeper lateral, rounded internal lobe. The siphuncle has a position between the centre of the aperture and the venter (after Shimansky 1967).

Remarks
For a discussion of the composition and limits of the genus, see .

Etymology
Named after the Imazighen, the ethnic group indigenous to the Maghreb region of North Africa.

Description
Holotype MB.C.31291 is a somewhat weathered specimen 105 mm in diameter, allowing the study of two whorls (Fig. 6). The conch is barrel-shaped, thinly pachyconic and subevolute (ww/dm = 0.64; uw/ dm = 0.38) with a very high coiling rate (WER = 2.28) and weakly embracing whorls. The whorl profile is trapezoidal with a flattened venter, an angular ventrolateral shoulder and flattened flanks plus umbilical wall. On the penultimate whorl, the ventrolateral shoulder bears eight longitudinally elongate nodes per half volution; they are much weaker on the last volution. The shell surface appears to be smooth.

Remarks
Temnocheilus imazighenorum sp. nov. is similar to T. coronatus but differs in the more compressed conch (ww/dm ~ 0.65 in T. imazighenorum but ~ 0.75 in T. coronatus), in the less depressed whorl profile (ww/wh ~ 1.85 in T. imazighenorum but ~ 2.25 in T. coronatus) and in the more flattened venter, which is broadly arched in T. coronatus. Temnocheilus coronatiformae differs in the slightly convex venter.

Etymology
Named after Martina Aubrechtová, in honour of her studies on Palaeozoic nautiloids.

Description
Holotype PIMUZ 93511 is a slightly deformed but otherwise rather well-preserved specimen with a conch diameter of 54 mm (Fig. 7). The last quarter of the last preserved whorl belongs to the body chamber. The conch is thickly pachyconic to cadiconic and subevolute with a high coiling rate (WER = 2.04-2.21). The whorl profile is broadly trapezoidal (ww/wh 1.88 to 2.14) with a very broadly and continuously rounded venter; the ventrolateral shoulder is narrowly rounded. The nodes are about twice as long as they are wide and their spacing is equal to their length. There are ten such nodes on the last whorl, giving the ventrolateral shoulder a conspicuous coronate appearance.

Remarks
Temnocheilus aubrechtovae sp. nov. differs from the other Early Carboniferous species of the genus in the shape of the venter, which is either nearly flat (e.g., T. coronatus, T. imazighenorum sp. nov.) or slightly concave (e.g., T. ventroconcavum). Temnocheilus coronatiformae has a similar conch shape but differs from T. aubrechtovae in the much smaller and more numerous ventrolateral nodes (about 15 per volution).

Diagnosis
Genus of the family Trigonoceratidae with usually thickly discoidal to pachyconic evolute conch; whorls slightly impressed or without contact; whorl profile rounded triangular or trapezoidal with flattened or weakly concave venter and pronounced ventrolateral shoulder. Conch rapidly increasing in height with a high coiling rate (WER usually higher than 2.20). Ornament with fine lines and very coarse spiral ridges around the ventrolateral shoulder, sometimes also on the venter. Septa without inflexions, moderately concave. Suture line slightly sinuous with small external lobes, sometimes with lateral and internal lobes. Siphuncle small with subcentral position (after Kummel 1964;Shimansky 1967;emended).

Included species
Reviews of the species belonging to Vestinautilus have been given by Histon (1999),  and . Species of the genus have been described from the following regions: North America (Winchell 1862 Turner (1954) revised Vestinautilus and specifically restricted the genus "to forms resembling the typespecies in possessing a venter concave or channelled at some stage of growth, a broad, depressed whorlsection, and a conch ornamented with spiral ribs, lirae and sulci." At the same time, he introduced the new genus Subvestinautilus, which he classified in the family Temnocheilidae. He stated that "the genus much resembles Vestinautilus … in shape but lacks a concave or channelled venter at any stage of development." However, since he regarded Vestinautilus as belonging to the family Triboloceratidae, he indirectly saw the close morphological similarity with it as the result of convergent evolution. This opinion was followed by Shimansky (1967) and Histon (1999), albeit with a different family attribution. However, Dzik (1984) rejected this concept, treating Subvestinautilus as a synonym of Vestinautilus.

KORN D. & KLUG C., Early Carboniferous nautiloids from the Anti-Atlas
We do not accept the separation of the two genera. The variable shape of the venter, which changes in some species during ontogeny, can hardly be regarded as a distinguishing criterion for these genera. We therefore assign species with coarse spiral ridges and a broad trapezoidal whorl profile, whether with a concave or convex venter, to Vestinautilus.

Etymology
Named after Birgit Kessler (Berlin), who found the holotype.

Description
Holotype MB.C.31287 is an entirely chambered steinkern specimen with 41 mm phragmocone diameter; it comprises one and a quarter whorl ( Fig. 9). At the largest diameter of the specimen, the conch shape is thinly pachyconic and subevolute (ww/dm ~ 0.68; uw/dm ~ 0.38). The whorl profile is depressed (ww/ wh ~ 1.74) and has the shape of a symmetric oval. The coiling rate is very high (WER ~ 2.72) and the last whorl just touches the preceding one. The umbilical window has a diameter of 11.5 mm. European Journal of Taxonomy 885: 156-194 (2023) The initial chamber is bluntly cone-shaped with a length of 0.6 mm, a height of 2.0 mm and a width of about 4 mm. Very early in ontogeny, the whorl profile becomes depressed and already immediately after the protoconch, an angular ventrolateral shoulder is formed. This angular shoulder becomes more pronounced to form a spiral ridge, which is, at a conch diameter of 25 mm, accompanied by one less well-developed ridge on each side. The outer of these ridges fades out and is only barely visible at a conch diameter of 42 mm. Only some traces of the shell ornament are visible in the dorsal portion. They show coarse growth lines and three of them are arranged at a millimetre distance. They form a broadly arched ventral sinus.
The siphuncle has a subcentral position with a slight shift towards the venter. The suture line forms a wide and shallow external lobe, a very shallow and wide lateral lobe and a small, rounded internal lobe.

Remarks
Vestinautilus kesslerae sp. nov. has a somewhat marginal position in the morphological spectrum of the genus. It differs from the other species because of the combination of a number of conch and sculpture characters: the advolute conch shape even at a conch diameter of 40 mm, the comparatively weak development of only a few longitudinal ridges and the convex venter.

Diagnosis
Genus of the family Trigonoceratidae with discoidal, usually evolute conch; whorls slightly impressed; whorl profile hexagonal or pentagonal with flattened or slightly concave venter and narrowly rounded umbilical margin. Conch moderately increasing in height with a high coiling rate (WER usually higher than 2.00). Ornament in the adult stage with coarse growth lines, in the preadult stage with fine spiral lines. Suture line with shallow external and lateral lobes. Siphuncle small with subcentral position (after Kummel 1964;emended).

Remarks
For a discussion of the composition and limits of the genus, see  and .

Description
Specimen MB.C.31288 is a weathered fragment of about a quarter of a whorl of the body chamber. It belongs to a specimen with a conch diameter of about 100 mm. Shell ornament is not preserved. The conch is evolute (uw/dm is about 0.50); the whorl profile is subquadratic with a slightly concave venter, subangular ventrolateral shoulders, sinuous flanks with a broadly rounded umbilical margin and a convex dorsum (Fig. 10).

Diagnosis
Genus of the family Trigonoceratidae with usually pachyconic, subinvolute or evolute conch; whorls usually slightly impressed, whorl profile compressed with broadly rounded or slightly flattened venter European Journal of Taxonomy 885: 156-194 (2023) and rounded umbilical margin. Conch very rapidly increasing in height with a high coiling rate (WER usually higher than 2.50). Sculpture with broad, rounded nodes on the flanks. Septa without inflexions, moderately concave. Suture line nearly straight with very shallow external lobe and usually with an internal lobe; some species with an annular lobe. Siphuncle with subcentral position.

Remarks
Endolobus is a genus in need of revision both in its definition and possible phylogenetic position. For example, according to Gordon (1965), the annular lobe belongs to the diagnosis of the genus, whereas Shimansky (1967) did not consider this a necessary character. The assignment of the material from the Anti-Atlas can therefore only be tentative. Early Carboniferous species are known mainly from North America (for a species list, see Gordon 1965). Most of them are very large specimens, which makes a comparison with considerably smaller specimens difficult. The material from the Anti-Atlas is not very typical for Endolobus and occupies a marginal position within the genus.

Etymology
From the Latin 'rota', meaning 'wheel', because of the conch shape.

Description
Specimen MB.C.31289 is a fragment of a specimen with about 85 mm conch diameter, consisting of three chambers and a short part of the body chamber with about 63 mm whorl width (Fig. 11A). At a whorl height of 39 mm, it has a ww/wh ratio of 1.60, but this ratio increases markedly during the previous half volution. The whorl profile is rounded-triangular with a broad venter, a broadly rounded ventrolateral shoulder and a nearly semicircular area consisting of flanks and dorsum (Fig. 11A).

KORN D. & KLUG C., Early Carboniferous nautiloids from the Anti-Atlas
A concave dorsal whorl zone does not exist. One large and very low ventrolateral node is visible on the fragment. The suture line extends with a wide and shallow lobe across the venter; it forms a low saddle on the flank and does not possess an internal lobe (Fig. 11B).

Remarks
Endolobus rota differs from the other Early Carboniferous species of the genus mainly in the very low and broad nodes on the ventrolateral margin. Another criterion is the lack of whorl overlap, but this may be due to the relatively small size of the holotype when compared with the North American species of Endolobus.

Description
Specimen MB.C.31290 is a phragmocone fragment of a little less than a quarter of a whorl (Fig. 12) and consisting of seven chambers. It has a whorl height of 15 mm and a ww/wh ratio of 1.90. The venter is broadly rounded and separated from the rounded umbilical wall by a narrowly rounded umbilical margin.
There is a shallow dorsal imprint zone (IZR ~ 0.20). The suture lines are rather densely arranged; they show a very wide and shallow lobe on the flanks and venter and a shallow, broadly rounded internal lobe.

Diagnosis
Genus of the family Trigonoceratidae with discoidal to pachyconic, usually subevolute conch. The first whorl is 12-20 mm in diameter with an umbilical foramen about 4-8 mm wide; the conch is rapidly increasing in height with a high coiling rate (WER usually higher than 2.50). Whorls weakly embracing, their profile is rectangular with more or less angular umbilical margin and ventrolateral shoulder. Sculpture with faint longitudinal ridges around the ventrolateral shoulder. Septa without inflexions, moderately concave. Suture line with moderately deep ventral and lateral lobes. The siphuncle has a position between the centre of the aperture and the venter (after Shimansky 1967).

Remarks
Epidomatoceras belongs to a group of Early Carboniferous nautiloids of which the phylogenetic and taxonomic relationships are far from being solved (Dzik & Korn 1992). Unlike most other late Tournaisian and Viséan evolute nautiloids, it shows the formation of a distinct umbilical margin.
The genus has a wide distribution across facies boundaries; it occurs in both shallow and deep shelf strata. For this reason, it is often found together with ammonoids.

Etymology
Named after Volker Ebbighausen (1941Ebbighausen ( -2011 and Rodion Ebbighausen, who collected the majority of the type material.

Description
Holotype MB.C.31294.1 is a nearly complete but somewhat corroded specimen with a conch diameter of 67 mm; it allows the study of two whorls (Fig. 13A). The conch is widely wheel-shaped with a moderately wide umbilicus (ww/dm = 0.68; uw/dm = 0.33). The profile of the last whorl is depressed (ww/wh = 1.64) and subtrapezoidal with a nearly flat, steep umbilical wall, a subangular umbilical margin, slightly flattened, weakly converging flanks, a broadly rounded ventrolateral shoulder and a European Journal of Taxonomy 885: 156-194 (2023) flattened venter with a shallow concave depression. Half a volution earlier, at 41 mm dm, the venter is weakly convex and the ventrolateral shoulders are marked by three longitudinal ridges, of which the inner one is the most prominent and separated from the middle one by a distinct groove. The outer of the three ridges is the weakest and located on the venter. The shell surface appears to be smooth. The internal mould of the inner whorls is visible in the umbilicus; they show a pronounced umbilical margin and a rather steep, flattened umbilical wall.
Paratypes MB.C.31294.2 (Fig. 13B) and MB.C.31294.3 (Fig. 13C) have a conch morphology that is very similar to that of the holotype. Specimen MB.C.31294.3 is less well preserved in the outer whorl but provides a good insight of the earlier growth stage. Already at 15 mm diameter, an angular and slightly raised umbilical margin is developed, on which the growth lines are strengthened and form delicate plications.
Paratype MB.C.31294.4 yielded a conch cross section that allows the study of two and a half volutions ranging from 9 mm to 46 mm conch diameter (Fig. 14A). It is not clear from the specimen whether

KORN D. & KLUG C., Early Carboniferous nautiloids from the Anti-Atlas
some parts of the inner whorls are dissolved; the umbilical opening appears to have a width of 3.7 mm. The earliest preserved whorl profile (1.66 mm high, 2.53 mm wide) is rounded triangular with a flattened venter, but half a volution later (9 mm dm), a pronounced, subangular ventrolateral shoulder is developed and the nearly parallel, weakly converging flanks are bordered umbilically by a broadly rounded umbilical margin. From this growth stage, the whorl profile is rounded pentangular. Half a volution later, at 15 mm dm, this whorl profile is still present, but the umbilical margin is sharpened by a longitudinal crest formed by the shell. This whorl does not embrace the preceding one. Another half of a whorl later, at 26 mm dm, the umbilical wall is flattened and steep, while the umbilical margin is rounded. In this stage, the ventrolateral shoulder is characterised by a longitudinal groove accompanied by weak crests on both sides. Finally, at 46 mm dm, the ventrolateral and umbilical shoulders are narrowly rounded; venter, flanks and umbilical wall are flattened. The cross section demonstrates that the conch proportions do not change significantly during ontogeny. There is, between 9 and 46 mm conch diameter, a slight increase of the ww/dm ratio (from 0.58 to 0.66) paralleled by a slight decrease of the uw/dm ratio (from 0.43 to 0.29). The coiling rate increases from about 2.65 to 3.10 ( Fig. 14C-E).
It appears that intraspecific variation ranges within rather narrow limits and ontogenetic changes are small. Specimens between 36 and 67 mm conch diameter, for instance, range in their ww/dm ratio between 0.60 and 0.70 with a weak tendency to become stouter with increasing diameter. In the same growth interval, the umbilical width ratio shows a very weak decrease. Only the coiling rate appears to decrease more significantly from a WER value of about 3.15 at 50 mm dm to 2.70 at 67 mm dm (Fig. 14C-E).
Paratype MB.C.31294.5 is a rather poorly preserved fragment of a large specimen (37 mm whorl width), but it shows the surface of a septum. This is continuously domed; the lobes in the suture line (Fig. 14B) are thus cut-out shapes of the septum and are not caused by septal inflexions. The siphuncle has a subcentral position and is slightly shifted from the centre towards the venter.

Remarks
Epidomatoceras ebbighausenorum sp. nov. differs from the other species of the genus in its stout conch and depressed whorl profile and the narrower umbilicus. The type species of the genus, Epidomatoceras planotergatum, for instance, has a nearly quadratic whorl profile (ww/wh ~ 1.05), while it is depressed in E. ebbighausenorum (ww/wh ~ 1.60). The umbilicus is rather wide in E. planotergatum (uw/dm ~ 0.37) but narrower in E. ebbighausenorum (uw/dm ~ 0.30). Similar differences occur when E. ebbighausenorum is compared with other species of Epidomatoceras, although E. doohylense possesses a slightly depressed whorl profile (ww/wh ~ 1.10).

Diagnosis
Genus of the family Liroceratidae with pachyconic to globular, involute or subinvolute conch; umbilicus closed by a plug in some species. The first whorl is 10-20 mm in diameter with a very small umbilical foramen; the conch is rapidly increasing in height with a high coiling rate (WER usually higher than 2.50). Whorls weakly embracing, their profile ranges from reniform to nearly circular. Juvenile conch with longitudinal ridges; adult ornament with growth lines with a fairly deep ventral sinus and spiral lines around the umbilicus in some species. Septa without inflexions, slightly concave. Suture line simple, nearly straight to straight with a shallow, broadly rounded internal lobe. The siphuncle has a position between the centre of the aperture and the venter (after Gordon 1965;Shimansky 1967).

Remarks
Liroceras is a genus with a wide stratigraphic range, extending from the Viséan to the latest Permian. Gordon (1965) and Shimansky (1967) compiled species lists; these demonstrate the wide stratigraphic and geographic distribution. In contrast, the morphological range within the genus is small; the conchs of all species are very similar and differ mainly in the width of the umbilicus and in the formation of spiral lines. The most similar genus is Bistrialites Turner, 1954, but in this genus the umbilical margin is more angular, in contrast to Liroceras with a rounded or subangular umbilical margin.

Etymology
From the Latin 'vermis', meaning 'maggot', because of the appearance of the holotype.

Description
Specimen MB.C.31295.1 (Fig. 15C) was chosen as the holotype because it is the only one that shows traces of the shell ornament. It is, with 34 mm conch diameter, thickly pachyconic and subinvolute (ww/ dm ~ 0.82; uw/dm ~ 0.21) with a strongly depressed, reniform whorl profile (ww/wh ~ 1.77), a very small whorl overlap zone (IZR ~ 0.12) and a very high coiling rate (WER ~ 2.85). The whorl profile has a broadly parabolic outline. The venter is broadly arched; the conch is widest at the umbilical margin from where the broadly rounded flanks converge towards the venter. The umbilical margin is continuously rounded and the umbilical wall is convex. The suture line extends almost straight across the umbilical European Journal of Taxonomy 885: 156-194 (2023) wall, flanks and venter. Shell remains on the umbilical wall show that four fine and sharp, wide-standing spiral lines are located on the outer portion of the umbilical wall. These spirals are entirely formed by the shell; they are not visible on the internal mould.
Paratype MB.C.31295.3 (Fig. 15B) is also a desert-corroded specimen, with 42 mm conch diameter, of which the last quarter of a whorl belongs to the body chamber. It has a geometry very similar to that of the holotype (ww/dm ~ 0.81; uw/dm ~ 0.20; ww/wh ~ 1.76; WER ~ 2.89; IZR ~ 0.11) The suture line extends almost straight across the umbilical wall, flanks and venter (Fig. 16A).
The second paratype, MB.C.31295.2 (Fig. 15A), has about 49 mm in conch diameter and is less strongly corroded than the other two specimens. It is an internal mould that appears to be completely smooth without any traces of ornament. Its conch proportions are almost exactly corresponding to those of the other two specimens.
The three specimens show that ontogenetic changes of the conch geometry and variation between the specimens is low (Fig. 16B-D), at least in the examined size-range. Between 20 and 49 mm in conch diameter, the ww/dm ratio ranges between 0.81 and 0.88, the uw/dm ratio between 0.20 and 0.25 and the whorl expansion rate between 2.83 and 2.89.

Remarks
Liroceras vermis sp. nov. belongs to the thickly pachyconic to globular species of the genus like L. excentricum and L. lunense, while the other species possess more compressed conchs. The new species differs from L. lunense and L. concentricus in the wider umbilicus (uw/dm ~ 0.20 in L. vermis and ~ 0.12 in the other two species) and from L. praelunense in the more slender conch (ww/dm ~ 0.82 in contrast to ~ 0.92).  Table 7 Diagnosis Species of Liroceras with thickly pachyconic, subinvolute conch (ww/dm ~ 0.75; uw/dm ~ 0.25), whorl profile moderately depressed (ww/wh ~ 1.65) with broadly rounded venter and subangular umbilical margin. Coiling rate very high (WER ~ 2.65), whorls very weakly embracing (IZR ~ 0.17). Suture line nearly straight.

Etymology
Named after Driss Karaoui (Hassilabied), the collector of the specimen.

Description
Holotype PIMUZ 39515 is a corroded, desert-polished specimen with a phragmocone diameter of about 46 mm (Fig. 17). It is fully septate and has about 22 chambers in the last volution. It is, at 46 mm in conch diameter, thickly pachyconic and subinvolute (ww/dm = 0.77; uw/dm = 0.25) with a strongly depressed, reniform whorl profile (ww/wh = 1.65), a very small whorl overlap zone (IZR = 0.17) and a very high coiling rate (WER ~ 2.65). The whorl profile is crescent-shaped and widest at the subangular umbilical margin. The umbilical wall is flattened and slightly oblique. The suture line extends nearly linearly across the flanks and venter.

Remarks
Liroceras karaouii sp. nov. differs from L. vermis sp. nov. in the subangular umbilical margin and in the slightly wider umbilicus (uw/dm ~ 0.25 in L. karaouii but only uw/dm ~ 0.20 in L. vermis). This shape of the umbilicus is also the most important distinguishing character from the other species of the genus. The pronounced umbilical margin in L. karaouii can be seen as a plesiomorphic character, which transforms from the possible evolutionary lineage from Bistrialites to Liroceras.

Remarks
Ephippioceras is a genus of which several of the species are known from only a few specimens; furthermore, the very different sizes of the described specimens make a comparison difficult. Another problem is the often fragmentary preservation of the material.

Etymology
Named after the brachiopod genus Pygope, because of the shape of the septal surface.

Description
Specimen MB.C.31292 (Fig. 18A) is a fragment of a specimen with a phragmocone diameter of about 80 mm. The whorl profile is crescent-shaped with a broadly rounded venter that continues onto the flanks, a rounded umbilical margin and a convex umbilical wall. The whorl section is moderately depressed (ww/wh = 1.60) and the whorl embraces the preceding one to a rather high degree (IZR = 0.37). The septal surface shows the striking bilobate shape with a median ridge that separates the septum in two concave bulges. The suture line forms a narrow, subangular saddle on the venter, a wide, broadly rounded lobe on the flank and another smaller lobe on the umbilical wall (Fig. 18C). 885: 156-194 (2023)

Remarks
Ephippioceras pygops sp. nov. has a far less depressed whorl profile when compared with the other species of the genus. While the ww/wh ratio is only 1.60 in E. pygops, it is close to a value of 2.00 or even higher in E. clitellarium and E. sphaericum (Shimansky 1967). In E. bilobatum, E. ferratum and E. verneuili, the whorl overlap is much lower (IZR ~ 0.20) than in E. pygops (IZR ~ 0.37). Ephippioceras spirale is difficult to compare because of the small size (19 mm dm) of the only one specimen. Fig. 18. Ephippioceras pygops sp. nov.; holotype MB.C.31292 (Korn 1999 Coll.)

Diagnosis
Genus of the family Solenochilidae with pachyconic to globular, involute or subinvolute conch. The conch is very rapidly increasing in height with an extremely high coiling rate (WER usually higher than 4.00). Adult body chamber with long lateral outgrowths. Whorls weakly without contact or embracing, their profile ranges from reniform to nearly circular. Suture line simple, nearly straight with a small annular lobe. The siphuncle has a position adjacent to the venter (after Gordon 1965;Shimansky 1967). Gordon (1965: 152) gave an overview of the previously described species of Solenochilus. He listed 24 species (some with question marks), most of which are known from Late Carboniferous strata of North America.

Remarks
Solenochilus is a genus whose species are mainly known from late Carboniferous strata of North America. Gordon (1965) published an identification key for these species, in which the species described from Europe can also be included. However, it is clear that this key does not represent a phylogenetic scheme and that it contains species with different ontogenetic stages.
Most occurrences of specimens of the genus are in sediments of the shallow shelf; therefore, Solenochilus is usually only rarely found together with ammonoids. For example, the genus is apparently absent from the assemblages of the Dalle à Merocanites of Timimoun ) and Gara el Itima N; both are occurrences characterised by a high number of ammonoid specimens. The comparatively frequent occurrence of the genus in layers with many ammonoids at Rissani is therefore an exception.

Description
Holotype MB.C.31286 is a steinkern specimen with a 72 mm conch diameter, of which the last 120 degrees belong to the body chamber (Fig. 19). The peculiar conch shape with extremely high coiling rate (WER = 3.92) can be described as thickly pachyconic (ww/dm = 0.82); the whorl profile is characterised by the nearly circular, weakly depressed shape (ww/wh ~ 1.25) with venter, flanks, umbilical margin and umbilical wall broadly rounded. The embraced area of the preceding whorl is very small, the imprint zone depth is ~ 0.25. The internal mould is smooth, without traces of ornament. The suture line possesses a very shallow, broadly rounded lateral lobe and a very shallow external lobe.
Paratype PIMUZ 39509 is much smaller at 27 mm dm. The initial chamber is conical with a diameter of ca 4.8 mm. Half of it has broken off, exposing the first septum. The whorl height increase is extreme, while the umbilical width and whorl overlap are very low. The whorl cross section is nearly circular. The first four sutures are nearly straight with a very small and shallow external lobe. Following the fourth septum (ca 14 mm dm), a few weak radial ridges are visible on the flank, which fade out after a few millimetres. Parts of the growth lines are visible on the broadest part of the whorl, where they form a projection (at 15 mm dm).  Table 9. Conch dimensions (in mm) and ratios of Solenochilus lucynae sp. nov.

Remarks
Solenochilus lucynae sp. nov. differs from the other Early Carboniferous species of the genus as follows: S. dorsale and S. hibernicum possess, in contrast to the new species, a slightly opened umbilicus. Solenochilus clausum has an almost closed umbilicus but differs in the more slender conch and hence a narrower whorl profile (ww/wh ~ 0.70) from S. lucynae (ww/wh ~ 1.25).

Etymology
Named after Alexander Pohle, in honour of his studies on Palaeozoic nautiloids.

Description
Holotype PIMUZ 39513 is an almost completely septate fragment of a conch with a constructed diameter of about 78 mm (Fig. 20A-B). It has an oval, slightly depressed whorl profile (ww/wh ~ 1.40) with a broadly rounded area consisting of flanks and venter. The whorl profile is widest near the rounded umbilical margin. The umbilical wall shows a rapid change from a simple convex shape to a biconcave shape in the segment of the last third volution. This is produced by the rapid protrusion of a narrowly rounded ridge, which would probably develop into a longer umbilical spine at a later ontogenetic stage. The dorsum is flattened and slightly incurved, but there is no sign of a preceding whorl; the coiling rate is extremely high (WER ~ 5.60). The specimen shows an oval, slightly depressed whorl profile in the penultimate half volution (Fig. 20A). The specimen does not provide evidence of the size of the protoconch. Areas of the shell surface are preserved on the umbilical wall and the inner flanks, although heavily corroded. They show fine growth lines that are already strongly curved backwards from the umbilical ridge, show a weak projection on the umbilical margin and extend backwards on the inner flank. European Journal of Taxonomy 885: 156-194 (2023) Paratype PIMUZ 39508 is also corroded and measures 73 mm in diameter (Fig. 20C). It exposes two thirds of the last whorl including parts of the body chamber. This specimen shows no whorl overlap and an extreme whorl expansion rate of over 6.00. The umbilicus is opened (uw/dm = 0.16); the umbilicus is oblique and convex. It displays the characteristic bulge, which rises from the umbilical seam and climbs toward the umbilical shoulder over the last half volution. The terminal spine is not preserved, since the terminal aperture is missing. It shows the nearly straight suture line. It shows that the siphuncle has a nearly ventral position but does not affect the suture line. A very similar specimen was illustrated by Sturgeon & Miller (1948) as Solenochilus greenensis; however, it has a Moscovian age. According to the authors, is has a "relatively narrow" impressed zone and differs thus from S. pohlei sp. nov., without an impressed zone.

Description
Specimen PIMUZ 39509 is a phragmocone fragment of a quarter of a whorl (Fig. 21A). It has a whorl height of 49 mm and has a weakly depressed whorl profile (ww/wh = 1.32). The fragment suggests that the whorls were growing very rapidly; the imprint zone is very small. It is likely that the umbilicus is  156-194 (2023) slightly opened. The suture line is almost straight with a small external lobe and a V-shaped internal lobe (Fig. 21B) created by a funnel-like indentation of the septum.
Specimen PIMUZ 39514 is a juvenile specimen with 25 mm conch diameter; it consists of less than one whorl. It is pachyconic with an umbilical window of about 6 mm diameter. The preserved protoconch is 3 mm long and 3.5 mm wide.

Remarks
It is not certain that the two specimens described here belong to the same species. The fragment of the larger specimen shows a slightly open navel in contrast to Solenochilus lucynae sp. nov. The difference to S. pohlei sp. nov. lies in the configuration of the umbilical wall, which forms a longitudinal ridge in S. pohlei.

Discussion
We describe 16 taxa of coiled nautiloids, of which six are kept in open nomenclature. All come from two regions, namely the Gara el Itima northeast of Taouz and the great plain between Dar Kaoua, Hassilabied, Merzouga and the Oued Ziz (Fig. 1). The specimens were loosely collected from mostly fine clastic successions of the Mougoui Ayoun, Zrigat and Hamou-Rhanem formations. As listed in the Material section, these nautiloids are usually significantly scarcer than contemporaneous ammonoids. Nevertheless, the diversity and disparity are remarkably high in comparison to the co-occurring ammonoids (Korn et al. 1999(Korn et al. , 2002(Korn et al. , 2003(Korn et al. , 2007Klug & Korn 2001;Bockwinkel & Ebbighausen 2006;Klug et al. 2006Klug et al. , 2016. Conch forms of the Viséan nautiloids from the Anti-Atlas range from very involute with closed umbilicus to advolute, from moderate to extremely high whorl expansion rates and from smooth to strongly ornamented. Following Tendler et al. (2015), this disparity in conch forms reflects specializations for certain tasks. While some of the Viséan nautiloid species have rather compact conchs, they were not optimized for hydrodynamics (see also Klug et al. 2016). It appears like compactness and manoeuvrability (e.g., Peterman & Ritterbush 2022) were the main tasks these nautiloids were positively selected for, while ammonoids occupied other archetypes with mostly more streamlined conchs, although some overlap in conch morphology occurs.
This raises the question of niches occupied by the various species of ammonoids and nautiloids.
Overall, abundances of ammonoid species are higher. This might indicate that the nautiloids were either primarily less common or that their main habitat was situated elsewhere. One ecological factor could be water depth. In any case, in order to draw conclusions on these palaeoecological factors, many more collections from different palaeoenvironments are needed.