Ammonoids of the Middle Devonian family Maenioceratidae in the Anti-Atlas of Morocco

. The ammonoids of the family Maenioceratidae from Givetian sedimentary rocks of the Anti-Atlas (Morocco) are investigated. The study is based on new collections stored in the Museum für Naturkunde, Berlin. The genera Maenioceras Schindewolf, 1933 and Afromaenioceras Göddertz, 1987 are revised; the genus Trimaenioceras is newly described. The species Maenioceras afroterebratum sp. nov., Maenioceras mzerrebense sp. nov., Maenioceras oufranense sp. nov., Maenioceras beckeri sp. nov., Afromaenioceras sulcatostriatum (Bensaïd, 1974), Afromaenioceras hiemale sp. nov., Afromaenioceras bensaidi sp. nov., Afromaenioceras brumale sp. nov., Afromaenioceras crassum (Bensaïd, 1974), Trimaenioceras klugi gen. et sp. nov., Trimaenioceras eculeus gen. et sp. nov., Trimaenioceras fuscina gen. et sp. nov. and Trimaenioceras paucum gen. et sp. nov. are described in detail.


Introduction
Maenioceras Schindewolf, 1933 is a genus of Middle Devonian ammonoids, which early on acquired the status of an important index fossil; Wedekind (1918) used "Goniatites terebratus" to define the "Maenecerasstufe" with "Goniatites terebratus Sandberger & Sandberger, 1851", which according to the interpretation of the time was supposed to characterise the youngest period of the Middle Devonian.At that time, specimens of Maenioceras and related genera were only known from a few regions, namely the Rhenish Slate Mountains (Sandberger & Sandberger 1850-1856;Kayser 1872;Holzapfel 1895;Foord & Crick 1897;Frech 1897Frech -1902)), the Harz Mountains (Roemer 1852), southern England (Phillips 1841;Whidborne 1890;Foord & Crick 1897) and the Montagne Noire (Frech 1902).First reports and descriptions from other regions, such as the Anti-Atlas in Morocco (Termier & Termier  section is particularly important for the Givetian biostratigraphy; it was first described by Bensaïd (1974) and discussed in detail by Becker et al. (2004).According to the latter study, the section consists mainly of shales with thin embedded beds of limestone and marl.The thickness of the layers with maenioceratids exceeds 55 m.According to their study, Bensaidites Korn, 2002 occurs only in the lowest 1.15 m (bed -1; "Bensaidites Bed"), Maenioceras in a 5.00 m thick interval in the middle part (bed 6; "Upper Maenioceras Bed") and Afromaenioceras in the uppermost 6.70 m of this section (beds 10-11a; "Afromaenioceras Beds").One has to note that the representative specimen of "Bensaidites n. sp." of Becker et al. (2004: pl. 1 fig. 22) (Bensaïd, 1974) -25 specimens Trimaenioceras klugi gen.et sp.nov.-24 specimens

Oufrane
The second significant locality is located 20 km south of Tata in the south-western part of the Anti-Atlas (Fig. 1B).Already known to Bensaïd (1974), two sections (Oufrane-W and Oufrane-E) were described by Aboussalam et al. (2004).These authors showed for the Oufrane-W section that the strata containing maenioceratid ammonoids are over 38 m thick in total and consist largely of shales and marls.According to this study, Maenioceras occurs first in the 5 m thick bed 3 ("Upper Maenioceras Bed") and Afromaenioceras occurs in the top 3 m (bed 11; "Afromaenioceras Bed").Fig. 2. Givetian ammonoid "standard zones" (from Becker & House 2000) and zonations for the Anti-Atlas of Morocco (from Becker & House 2000;Aboussalam & Becker 2011;Becker et al. 2018).Interval with the species described here highlighted.

Tiguisselt
The third section in the south-western part of the Anti-Atlas is Tiguisselt, which has a position 4 km southwest of Tata (Fig. 1B).It was mentioned by Bensaïd (1974) and described in detail by Aboussalam & Becker (2004).The following maenioceratid specimens are available:

Jebel Ouaoufilal
The locality south-west of Jebel Ouaoufilal has a position about 6 km north-east of Taouz (Fig. 1C) and 55 km south-southeast of Erfoud in the eastern Anti-Atlas.The fossil site, which only yielded Fig. 3.The morphological terms used in the descriptions of the ammonoid conchs and suture lines.float material, is located on the southern flank of the Amessoui Syncline, which exposes fossiliferous sedimentary rocks from the Ordovician to the Tournaisian in concordant succession (Klug & Pohle 2018).Haematitic fossils occur in a depression between Eifelian and Frasnian limestone beds.The following maenioceratid specimens are available: Afromaenioceras hiemale sp.nov.-26 specimens Afromaenioceras brumale sp.nov.-1 specimen Afromaenioceras crassum (Bensaïd, 1974)

Hassi Nebech
The section is located 20 km east-northeast of Taouz (Fig. 1C).Bensaïd (1974) provided a description of the Givetian part of the section and Bockwinkel et al. (2013)  The description of the material follows, as far as possible, the scheme for Palaeozoic ammonoids outlined by Korn (2010) and Klug et al. (2015) (Fig. 3).However, due to the limitation of ontogenetic data, the descriptions must remain incomplete.

Remarks
The four genera of the family are very easily distinguished on the basis of the suture line, particularly the shape of the external lobe.This shows a small, rounded E 2 lobe in Maenioceras and Afromaenioceras, but deep and pointed in Trimaenioceras gen.nov.Maenioceras and Afromaenioceras differ in the shape of the E 2 lobe, which in the latter genus has a rectangular form.
The stratigraphic distribution of the four genera is only in part well-known.Bensaidites is probably the stratigraphically oldest representative of the family with "B.koeneni" defining the earliest Givetian (Aboussalam & Becker 2011;Becker et al. 2018) in the Moroccan sections.Becker et al. (2004: pl. 1 fig.22) illustrated a specimen from the basal part of the Oued Mzerreb section (bed -1a), which they named "Bensaidites n. sp.".However, due to its suture line with a shallow, rounded E 2 lobe, this specimen belongs to Maenioceras.
It is clear that Maenioceras precedes Afromaenioceras (Fig. 2), but the position of the material assigned here to the new genus Trimaenioceras gen.nov.has been conclusively determined.In Oued Mzerreb, Trimaenioceras klugi gen.et sp.nov.co-occurs with several Afromaenioceras species in the high part of the section ("Afromaenioceras Beds").

Diagnosis
Genus of the family Maenioceratidae with ventrolateral grooves; shell usually without constrictions or internal thickenings.External lobe very wide or extremely wide; E 2 lobe usually very shallow, broadly rounded; ventrolateral saddle narrowly rounded or subangular; lateral lobe V-shaped, angular or blunt.

Remarks
The North African records of Maenioceras needed revision.Increasing knowledge led to the result that the North African species differ from those described from material of the Rhenish Mountains, although there is close resemblance between some of the species.With respect to the morphological differences, new species are described here.

Etymology
Named because of the resemblance with M. terebratum and the origin from North Africa.

Description
Holotype MB.C.31947.1 is a partly corroded limonitic internal mould with 17 mm conch diameter (Fig. 4A).The conch is thinly discoidal and involute (ww/dm = 0.40; uw/dm = 0.13) with a low coiling rate (WER ~ 1.70).The whorl profile is weakly compressed (ww/wh = 0.90); the flanks are slightly flattened and converge towards the pronounced ventrolateral shoulder, which is accompanied by a faint spiral groove, which begins at about 10 mm conch diameter and becomes distinct at 15 mm diameter.The venter is broadly convex and becomes flattened during the last preserved volution.Growth lines are only poorly preserved as imprints on the internal mould, which appears to be smooth.The phragmocone consists of about 18 chambers in the last preserved volution; there is a rather clear trend toward shorter chambers.
Paratype MB.C.31947.2 is a well-preserved specimen with 10.5 mm conch diameter (Fig. 4C).The conch is thickly discoidal and subinvolute (ww/dm = 0.50; uw/dm = 0.24) with moderately high coiling rate (WER ~ 1.82).The whorl profile is weakly depressed (ww/wh = 1.16); it shows very slightly convex flanks that converge towards the subangular ventrolateral shoulder.This is accompanied by a faint spiral groove.Traces of growth lines are visible on the internal mould; they are coarse, lamellar with strongly biconvex course.The suture line has, at approximately 10 mm conch diameter, an extremely wide external lobe with a very shallow, asymmetrically rounded E 2 lobe.On the flank follow a narrowly rounded ventrolateral saddle and a V-shaped, blunt lateral lobe (Fig. 4E).The phragmocone consists of about 14 chambers in the last preserved volution.
Paratype MB.C.31947.3 was used for a cross section (Fig. 4F).It shows, at 12 mm conch diameter, a thickly discoidal and subinvolute conch (ww/dm = 0.51; uw/dm = 0.24) with low coiling rate (WER ~ 1.62).The whorl profile is weakly depressed (ww/dm = 1.11); it is remarkable for its flattened flanks, which are even weakly concave near the umbilicus.The flanks are weakly convergent and the venter is slightly flattened.

Remarks
Maenioceras afroterebratum sp.nov. is similar to M. terebratum and M. ornatum from the Rhenish Mountains.However, the lateral lobe is broadly rounded and the ventrolateral saddle is narrowly rounded in the new species, while both are subacute in M. terebratum (Korn & Bockwinkel 2021: text-fig. 4b) and even acute in M. ornatum (Holzapfel 1895: pl. 6 fig.6c).Maenioceras afroterebratum differs by the much stouter conch and the more widely rounded venter from M. oufranense sp.nov.(ww/

Etymology
Named after the type locality Oued Mzerreb.

Description
Holotype MB.C.31950.1 is a well-preserved limonitic internal mould with parts of the body chamber preserved (Fig. 5B).It has, at 10.6 mm conch diameter, a thickly discoidal and subinvolute conch (ww/ dm = 0.53; uw/dm = 0.26) with low coiling rate (WER = 1.67).The whorl profile is weakly depressed (ww/wh = 1.17) with slightly arched flanks that converge towards the narrowly rounded ventrolateral shoulder, which forms a very inconspicuous margin of the rounded venter.The growth lines are impressed as lamellar, strongly biconvex remains on the surface of the internal mould.The last suture line shows, at 3.8 mm whorl height, a very wide external lobe, a very shallow E 2 lobe at the upper flank of the E lobe, a small and low, rounded ventrolateral saddle and a V-shaped lateral lobe with narrowly rounded base.(Fig. 5E).The last half volution of the phragmocone has eight septa, of which the last are more closely spaced.
Paratype MB.C.31950.3 is a well-preserved limonitic internal mould of a fully chambered specimen (Fig. 5C).It has at 8.4 mm diameter a thinly pachyconic and subinvolute conch (ww/dm = 0.62; uw/ dm = 0.29) with low coiling rate (WER = 1.72).The whorl profile is weakly depressed (ww/wh ~ 1.36); the flanks are slightly convex and converge towards the rounded ventrolateral shoulder and the rounded venter.The growth lines appear to be coarse, lamellar and strongly biconvex in their course.The last volution of the phragmocone has 12 chambers.Paratype MB.C.31950.2 is a well-preserved limonitic internal mould (Fig. 5A).It has, at 12.6 mm diameter, a thickly discoidal and subinvolute conch (ww/dm = 0.55; uw/dm ~ 0.25) and shows that the umbilicus starts closing at about 10 mm conch diameter.The flanks are convex and converge towards the ventrolateral shoulder, which appears to be subangular with a weak ventrolateral groove; the venter is nearly flat.

Etymology
Named after the type locality Oufrane.

Description
Holotype MB.C.31951.1 is a limonitic, dessert-polished internal mould; it is fully septate and, with 20 mm conch diameter, the largest available specimen (Fig. 6A).It is an extremely discoidal and involute conch (ww/dm = 0.33; uw/dm = 0.04) with an apparently low coiling rate.The whorl profile is compressed (ww/wh = 0.58); the flanks stand almost parallel in the umbilical area, but becoming convergent towards the rather narrowly rounded venter.The ventrolateral shoulder shows a pronounced spiral groove.The growth lines, which are visible as impressions, were probably coarse and clustered.They extend with strongly biconvex course.The suture lines are difficult to trace, but it is clear that the last chambers of the phragmocone are very closely spaced.
Paratype MB.C.31951.2 is a well-preserved limonitic internal mould of a phragmocone (Fig. 6B) with 12.5 mm diameter.It is a thinly discoidal and involute conch (ww/dm = 0.41; uw/dm = 0.13) with low coiling rate (WER = 1.61).The whorl profile is weakly compressed (ww/wh = 0.80); the flanks are flatly convex and converge towards the narrowly rounded venter.The ventrolateral shoulder possesses a faint spiral groove.The growth lines are apparently coarse and strongly biconvex.
Paratypes MB.C.31951.4(7.5 mm conch diameter; Fig. 6D) and MB.C.31951.3(13 mm conch diameter; Fig. 6C) demonstrate the transition from the juvenile stage with slow but constant opening of the umbilicus to the intermediate growth stage, in which the umbilicus becomes narrower by increased overlap of the inner flank area upon the umbilicus.
The cross section of paratype MB.C.31951.6 demonstrates the transformation from the juvenile to the preadult conch morphology (Fig. 6F).This ontogenetic transformation shows that the C-shaped whorl profile of the juvenile stage with a ww/wh ratio of about 2.00 is, beginning at a conch diameter of 5 mm, rapidly reduced to a value of 0.77 at 14 mm conch diameter.Parallel to this development, the uw/dm ratio is reduced markedly caused by overlap upon the umbilicus.The conch is thinly discoidal and involute at 14.2 mm dm (ww/dm = 0.40; uw/dm = 0.11); the flanks are almost parallel near the umbilicus and converge towards the narrowly rounded venter.The suture line of paratype MB.C.31951.5 shows a very wide external lobe, a very shallow, asymmetrically rounded E 2 lobe and a narrowly rounded, small ventrolateral saddle; the asymmetric lateral lobe has a convex ventral flank and a steeper dorsal flank (Fig. 6E).

Remarks
Maenioceras oufranense sp.nov. is characterised by the extremely discoidal and involute conch in specimens with about 20 mm conch diameter (ww/dm ~ 0.35; uw/dm ~ 0.05) and the narrowly rounded venter, which is broadly rounded in M. afroterebratum sp.nov.and nearly flat in M. mzerrebense sp.nov.
Maenioceras oufranense sp.nov.shows close similarity to M. tenue in the conch proportions, but differs in the narrowly rounded venter from Maenioceras tenue, which has an almost completely flat venter.

Description
Holotype MB.C.31952.1 is a limonitic internal mould of a fully chambered specimen (Fig, 7A) with 17 mm conch diameter; it is rather well-preserved only on the right side.The conch is thickly discoidal and subinvolute (ww/dm = 0.49; uw/dm = 0.24) with low coiling rate (WER = 1.57).The whorl profile is weakly depressed (ww/wh = 1.18) with slightly convex flanks.The ventrolateral shoulder forms a rather distinct margin separating the flanks and the almost flat, but slightly convex venter.The growth lines are bundled with a strongly biconvex course.The suture line is somewhat unusual for Maenioceras with an extremely wide external lobe and a symmetrically rounded E 2 lobe that is half as deep as the E 1 lobe.On the flank follow a narrowly rounded asymmetrical ventrolateral saddle and a deep, tongue-shaped lateral lobe (Fig, 7C).Paratype MB.C.31952.2shows the same conch proportions as the holotype with a ww/dm ratio of 0.49 and an estimated uw/dm ratio of 0.30 at 15 mm dm.Numerous dense growth lines are visible in this specimen (Fig, 7B).
Paratype MB.C.31952.3is, with a ww/dm ratio of 0.45 and a uw/dm ratio of 0.36 at 14.5 mm conch diameter, slightly more slender and more evolute than the other two type specimens.

Remarks
The deep E 2 lobe in Maenioceras beckeri sp.nov. is the cardinal character to separate the new species from the other species of the genus, which possess a shallow E 2 lobe.

Diagnosis
Genus of the family Maenioceratidae with or without ventrolateral grooves; shell with constrictions or internal thickenings.External lobe wide; E 2 lobe usually rectangular stair-shaped, narrowly rounded; ventrolateral saddle inverted U-shaped; lateral lobe U-shaped or tongue-shaped.

Description
Specimen MB.C.31953.1 is a partially corroded but otherwise rather well-preserved limonitic internal mould with 12.2 mm conch diameter (Fig. 8A).The conch is thickly discoidal and subinvolute (ww/ dm = 0.52; uw/dm = 0.30) with a low coiling rate (WER = 1.65); the whorl profile is weakly depressed (ww/wh = 1.15).The internal mould shows traces of pronounced, partly bundled growth lines, which produce faint tubercles at the ventrolateral shoulder.On the last volution, there are 13 constrictions of the internal mould; these extend with a low dorsolateral projection, a shallow lateral sinus, an extremely high, subacute ventrolateral projection and a very deep and narrow ventral sinus.These constrictions are deepest in the outer flank area.The specimen possesses a long body chamber and therefore, the suture line not visible.
Specimen MB.C.31953.2 is a well-preserved limonitic internal mould with 8 mm conch diameter, of which half of the last volution belong to the body chamber (Fig. 8C).The conch is thickly discoidal and subevolute (ww/dm = 0.54; uw/dm = 0.36) with a low coiling rate (WER = 1.71); the whorl profile Fig. 8. Afromaenioceras sulcatostriatum (Bensaïd, 1974)  Specimen MB.C.31953.3 was used for the production of a cross section (Fig. 8F), in which three volutions up to a conch diameter of nearly 11 mm can be studied.The cross section shows that the ontogenetic changes in the shape of the whorl profiles do not significantly change between 3.5 and 11 mm conch diameter; there is a trend toward a more slender conch with a narrower umbilicus.During this growth interval, the whorl profile changes from crescent-shaped to C-shaped.
The suture line of the specimen MB.C.31954.1 shows, at 3 mm whorl height, a wide external lobe with parallel flanks in its upper half (Fig. 8E); the stair-shaped E 2 lobe has a position on the flanks of the external lobe.The ventrolateral saddle is asymmetrically rounded and the lateral lobe is U-shaped and slightly asymmetric.The lateral lobe has only one third of the depth of the external lobe.

Remarks
Afromaenioceras sulcatostriatum is more involute and more slender than A. hiemale sp.nov.

Description
Holotype MB.C.31956.1 is a limonitic internal mould with 16 mm conch diameter, of which the left side well-preserved and the right side is somewhat corroded (Fig. 9A).The conch is thinly pachyconic and subevolute (ww/dm = 0.64; uw/dm = 0.39) with a low coiling rate (WER = 1.57); the umbilicus starts closing at 14 mm diameter.The whorl profile is moderately depressed (ww/wh = 1.88) with broadly rounded flanks and a nearly flat venter.The internal mould shows riblet-like traces of bundled growth lines, which extend with a strongly biconvex course; they form small tubercles at the umbilical margin.The suture line has a Y-shaped external lobe with stair-shaped flanks, a rectangular and blunt E 2 lobe, a slightly asymmetric, inverted U-shaped ventrolateral saddle and a deep, broadly rounded U-shaped lateral lobe (Fig. 9D).On the outer flank and the ventrolateral region occurs, on both sides of the conch, a sequence of densely arranged Housean pits (compare De Baets et al. 2011).The last phragmocone volution has only eleven chambers.

Remarks
The conch of Afromaenioceras hiemale sp.nov.is, with a ww/dm ratio of about 0.65 and a uw/dm ratio of about 0.40 at 16 mm conch diameter, significantly stouter and more evolute than the conch of A. sulcatostriatum with the ratios ww/dm ~ 0.50 and uw/dm ~ 0.30 at 12 mm conch diameter.

Etymology
Named after Mohamed Bensaïd, to honour his contribution to Moroccan palaeontology.

Description
Holotype MB.C.31959.1 is a moderately well-preserved, somewhat corroded specimen with 22 mm conch diameter (Fig. 10A).The conch is thinly discoidal and involute (ww/dm = 0.46; uw/dm = 0.06); the whorl profile is weakly compressed (ww/wh = 0.86) and the coiling rate moderately high (WER = 1.83).The flanks are slightly convex and terminated by a striking spiral groove on the ventrolateral shoulder; the venter is flattened.The internal mould shows traces of coarse, lamellar growth lines with strongly biconvex course.The suture line is not well-preserved, but possesses a wide external lobe with stair-shaped flanks, a high asymmetrically rounded ventrolateral saddle and a deep, asymmetrically rounded lateral lobe.Paratype MB.C.31959.3 is an internal mould with a conch diameter of 9.5 mm (Fig. 10D).The conch is thinly pachyconic and subinvolute (ww/dm = 0.62; uw/dm = 0.17) with a weakly depressed whorl profile (ww/wh = 1.29) and a low coiling rate (WER = 1.70).The flanks are convex and the venter broadly rounded.
Paratype MB.C.31959.5 was sectioned and shows the ontogenetic development of the conch geometry between diameters of 4.5 and 10 mm (Fig. 10F).Three volutions can be studied; they show only minor ontogenetic changes in the shape of the whorl profiles.A trend toward a more slender conch with a narrower umbilicus can be observed.During this growth interval, the whorl profile changes from crescent-shaped to C-shaped.

Remarks
Afromaenioceras bensaidi sp.nov. is characterised by the involute conch in the adult stage and is thus clearly separate from the other species of the genus.

Description
Holotype MB.C.31960 is a very well-preserved limonitic internal mould with 16 mm conch diameter (Fig. 11A).It is a thickly discoidal, subinvolute conch (ww/dm = 0.55; uw/dm = 0.18) with a weakly depressed whorl profile (ww/wh = 1.16) and a low coiling rate (WER = 1.53); flanks and venter are broadly rounded.The ventrolateral shoulder has a faint spiral groove.Traces of coarse growth lines are visible on the flanks.The last volution of the phragmocone has only ten chambers.
Paratype MB.C.31961 is a thickly discoidal, subinvolute conch with 16 mm conch diameter and shows, like the two specimens described above, rows of Housean Pits in the outer flank region (Fig. 11B).Paratype MB.C.31962.4 was sectioned (Fig. 11F) and shows two volutions up to a conch diameter of 8.2 mm.Between 5 and 8 mm conch diameter, the whorl profile changes from crescent-shaped to C-shaped and the conch becomes more slender and narrowly umbilicate.
Paratypes MB.C.31962.2(Fig. 11D) and MB.C.31962.3(Fig. 11E) Suture lines were drawn from those at wh = 4.5 and wh = 3.8 mm, respectively.Both show the Y-shaped external lobe with stair-shape flanks.However, they differ in the shape of the ventrolateral saddle, which is narrower in paratype MB.C.31962.2, and in the shape of the lateral lobe, which is blunt V-shaped in paratype MB.C.31962.2,but nearly U-shaped in paratype MB.C.31962.3.

Description
Specimen MB.C.31965.1 is a limonitic internal mould with 15.5 mm conch diameter, which is well preserved on the left side (Fig. 12A).The conch is thinly pachyconic and subinvolute (ww/dm = 0.64; uw/dm = 0.26); the umbilicus starts closing at 12 mm conch diameter.The whorl profile is weakly depressed (ww/wh = 1.46) and the coiling rate is low (WER = 1.62).The flanks are broadly convex and the venter is slightly flattened.A faint spiral groove marks the ventrolateral shoulder.Traces of coarse growth lines on the internal mould show a strongly biconvex course.The suture line has a Y-shaped external lobe with stair-shaped flank, and inverted U-shaped ventrolateral saddle and a deep, U-shaped lateral lobe (Fig. 12D).Housean pits are present on the outer flank.The last phragmocone volution has only eleven chambers.Specimen MB.C.31965.2 is a limonitic internal mould with 10 mm conch diameter, which is wellpreserved on the left side (Fig. 12B).It is a thinly pachyconic, subevolute conch (ww/dm = 0.67; uw/dm = 0.33) with a moderately depressed whorl profile (ww/wh 1.79) and a low coiling rate (WER = 1.65).The ventrolateral shoulder shows a poorly developed spiral groove.The suture line has an external lobe with strongly pouched, divergent flanks and a broad and deep lateral lobe (Fig. 12E).The last phragmocone volution has only ten chambers.Specimen MB.C.31965.3ss a well-preserved small limonitic internal mould with 5 mm conch diameter (Fig. 12C).It is thickly pachyconic and subevolute (ww/dm = 0.81; uw/dm = 0.34) with a strongly depressed whorl profile (ww/wh = 2.11) and a moderately high coiling rate (WER = 1.78).The umbilical wall is steep, flanks and venter are broadly convex.The suture line of the juvenile specimen shows a V-shaped external lobe with gently convex flanks and a wide, broadly rounded lateral lobe (Fig. 12F).(Bensaïd, 1974)

Diagnosis
Genus of the family Maenioceratidae with or without ventrolateral grooves; shell without constrictions or internal thickenings.External lobe very wide or extremely wide; E 2 lobe deep, cuneiform; ventrolateral saddle symmetrically rounded; lateral lobe V-shaped, angular.

Etymology
Named after the trident shape of the external lobe and the close relationship to Maenioceras.

Etymology
Named after Christian Klug, who discovered the ammonoid assemblage.
Paratype MB.C.31967.2has, at 18.5 mm diameter, a conch with very similar proportions like the holotype (Fig. 13B).The suture line has an extremely wide external lobe, which is subdivided in three almost identical prongs.The E 1 lobe is lanceolate and separated from the asymmetric, cuneiform E 2 lobe by a nearly symmetric median saddle that reaches three quarters of the depth of the external lobe.The ventrolateral saddle is inverted U-shaped and nearly symmetric; the lateral lobe is slightly asymmetric V-shaped with convex ventral flank and nearly straight dorsal flank (Fig. 13E).The last phragmocone volution has 14 chambers.Paratype MB.C.31967.4 was sectioned, but shows that the inner whorls are not preserved (Fig. 13G).However, it shows clearly that the whorl profile is, at 12 mm conch diameter, horseshoe-shaped.It is widest in the midflank area, from where the flanks converge towards the umbilicus and the continuously rounded venter.The umbilical wall is very low and strongly convex.

Remarks
Trimaenioceras klugi gen.et sp.nov. is similar to T. eculeus gen.et sp.nov., but differs in the more slender and narrowly umbilicate conch in comparative growth stages.At around 15 mm conch diameter, ~ 0. 50 and ~ 0.05 in T. klugi, but ww/dm ~ 0.60 and uw/dm ~ 0.25 in T. eculeus.Growth lines very fine.Suture line with wide external lobe, moderately deep, cuneiform, strongly asymmetric E 2 lobe, rounded ventrolateral saddle and V-shaped, symmetric, acute lateral lobe.

Etymology
From the Latin nomen 'eculeus' = 'a little horse', because of the horseshoe-shaped whorl profile.

Description
Holotype MB.C.31969.1 is a well-preserved limonitic, fully chambered specimen with 28 mm conch diameter (Fig. 14A).It is thinly discoidal and involute (ww/dm = 0.41; uw/dm = 0.11) and shows that the umbilicus starts closing at about 25 mm conch diameter by overlap of the flanks.The whorl profile is weakly compressed (ww/wh = 0.84) and the coiling rate is low (WER = 1.64).The suture line shows a very wide external lobe that is subdivided into three parts, of which the E 1 lobe is wider and deeper than the asymmetric, cuneiform E 2 lobes.The median saddle reaches about two thirds of the depth of the external lobe.The ventrolateral saddle is nearly symmetric and rounded; the lateral lobe is V-shaped with gently convex flanks (Fig. 14D).The last phragmocone volution has 16 chambers.
Paratypes MB.C.31969.2(20.5 mm conch diameter; Fig. 14B) and MB.C.31969.3(15 mm conch diameter; Fig. 14C) demonstrate the ontogenetic transformation of the conch shape.Together with the holotype, they show that the conch width decreases, between 15 and 28 mm conch diameter, from a ww/ dm ratio of about 0.60 to about 0.40; parallel to this, the uw/dm ratio decreases from 0.25 to about 0.10.The last phragmocone volution of paratype MB.C.31969.2 has 13 chambers.
The suture line of paratype MB.C.31969.4shows, at a whorl height of 9.5 mm, a very wide external lobe; the E 2 lobe is nearly V-shaped and blunt.The ventrolateral saddle is inverted U-shaped and the lateral lobe is V-shaped with a convex ventral flank (Fig. 14E).

Remarks
Trimaenioceras eculeus gen.et sp.nov. is similar to T. klugi gen.et sp.nov., but differs in the stouter and more widely umbilicate conch in comparative growth stages.At around 15 mm conch diameter, ww/ dm ~ 0.60 and uw/dm ~ 0.25 in T. eculeus, but ~ 0. 50 and ~ 0.05 in T. klugi.

Etymology
After the Latin nomen 'fuscina' = 'trident', because of the shape of the external lobe.

Description
Holotype MB.C.31970.1 is a fully septate internal mould of a specimen with 21 mm conch diameter (Fig. 15B).The conch is thinly discoidal with a rather small umbilicus (ww/dm = 0.42; uw/dm = 0.15); a weakly compressed whorl profile (ww/wh = 0.89) and a low coiling rate (WER = 1.71).The specimen shows that the umbilicus is being narrowed, caused by increased overlap of the flanks upon the umbilicus, during the last preserved volution.
Paratype MB.C.31970.2 is a specimen with 21.5 mm conch diameter (Fig. 15A), which in size and proportions of the conch closely resembles the holotype (ww/dm = 0.40; uw/dm = 0.14).The suture line shows a very wide external lobe that is subdivided into three almost equally wide and deep prongs, of which the E 2 lobes are asymmetric and cuneiform.The median saddle reaches about two thirds of the depth of the external lobe.The ventrolateral saddle is nearly symmetric and inclined towards the venter; the lateral lobe is V-shaped with gently convex flanks (Fig. 15C).The last phragmocone volution has about 16 chambers.

Remarks
Trimaenioceras fuscina gen.et sp.nov. is the species of the genus with the most slender conch.At about 20 mm conch diameter, its ww/dm ratio is ~ 0.40, while it is ~ 0.50 in T. klugi gen.et sp.nov.and T. eculeus gen.et sp.nov.Trimaenioceras fuscina differs from T. klugi in the less deep sutural elements of the external lobe.A suture line very similar to T. fuscina can be seen in T. eculeus, but this species differs in the wider umbilicus (uw/dm ~ 0.20) at 20 mm conch diameter (uw/dm is only ~ 0.15 in T. fuscina).

Etymology
From the Latin adjective 'paucus, -um' = 'poor', because of the rarity of specimens.

Description
Holotype MB.C.31971.1 is an incomplete internal mould with a conch diameter of 14 mm (Fig. 16A).It is thickly discoidal and involute (ww/dm = 0.58; uw/dm = 0.14) with a weakly depressed whorl profile (ww/wh = 1.25) and a low coiling rate (WER = 1.60).The flanks are weakly rounded and converge toward the broadly rounded venter; the ventrolateral shoulder shows a shallow spiral groove.The suture line has a wide external lobe, a moderately deep, asymmetric E 2 lobe, a slightly asymmetric rounded ventrolateral saddle and a wide, pointed L lobe (Fig. 16C).

Remarks
Trimaenioceras paucum gen.et sp.nov. is the only one Trimaenioceras gen.nov.with ventrolateral grooves and thus easily distinguishable from the other species.

Discussion
Ammonoids of the Givetian family Maenioceratidae are important index fossils in the Devonian sedimentary rocks of the Anti-Atlas (Morocco).Our study shows that the diversity of the family is  rather high in this region with three genera and thirteen species occurring in at least two successive stratigraphic units.

Fig. 1 .
Fig. 1.Geographic position of the fossil sites that yielded the material described here.A. Overview on the north-western part of Africa with the locations of Tata and Taouz.B. Geological map of the area south of Tata with the fossil localities at Oued Mzerreb, Oufrane and Tiguisselt.C. Geological map of the area of Taouz with the fossil localities at Jebel Ouaoufilal and Hassi Nebech.
Paratypes MB.C.31968.1 (14 mm conch diameter; Fig. 13C) and MB.C.31967.3(11 mm conch diameter; Fig. 13D) show the morphology of the intermediate growth stage, in which the umbilicus is being closed by increasing overlap of the inner flank upon the umbilicus.The suture line of paratype MB.C.31968.1 is similar to that of paratype MB.C.31967.2,but possesses less deep lobes (Fig. 13F).The ventrolateral saddle is narrowly rounded.The last phragmocone volution of paratype MB.C.31968.1 has 12 chambers.

Table 3 .
Conch dimensions (in mm) and ratios of Maenioceras oufranense sp.nov.faint groove in adult specimens.Growth lines coarse, strongly biconvex.Suture line with extremely wide external lobe, deep, U-shaped E 2 lobe, inverted U-shaped ventrolateral saddle and blunt, tongue-shaped lateral lobe.

Table 10 .
Conch dimensions (in mm) and ratios of Trimaenioceras klugi gen.et sp.nov.

Table 11 .
Conch dimensions (in mm) and ratios of Trimaenioceras eculeus gen.et sp.nov.Whorl profile at 20 mm conch diameter horseshoe-shaped with flattened subparallel flanks, rounded ventrolateral shoulder and rounded venter.Ventrolateral shoulder without spiral groove.Growth lines very fine.Suture line with wide external lobe, moderately deep, cuneiform E 2 lobe, rounded ventrolateral saddle and V-shaped, acute lateral lobe.

Table 13 .
Conch dimensions (in mm) and ratios of Trimaenioceras paucum gen.et sp.nov.