A morphometric approach to conch ontogeny of Cymaclymenia and related genera ( Ammonoidea , Late Devonian )

Abstract. Representatives of the Late Devonian ammonoid family Cymaclymeniidae were studied for their conch ontogeny. Two methods were applied: (1) the analysis of classical morphometric conch parameters and (2) an outline analysis of the aperture using elliptic Fourier analysis. Application of both methods leads to similar results, allowing a separation of some of the species by means of their ontogenetic pathways. The new species Procymaclymenia ebbighauseni n. sp., Cymaclymenia subvexa n. sp., Cymaclymenia formosa n. sp., Cymaclymenia lambidia n. sp., Cymaclymenia carnata n. sp., Cymaclymenia aulax n. sp., Cymaclymenia serotina n. sp. and Postclymenia calceola n. sp. are described in the systematic part.


Introduction
The study of ontogeny is becoming more important to biological research, particularly when combined with evolutionary patterns.In this respect, the study of allometric growth (i.e. the deviation from equal proportions during growth) is an important task for the study of life histories and functional properties of many organisms.Huxley (1924Huxley ( , 1932) ) and Huxley and Teissier (1936) outlined the major principles of allometry.The three levels of allometry (static, ontogenetic and phylogenetic allometry) were characterised by Gould (1977), Cheverud (1982) and Klingenberg (1998).Accretionary growth of ammonoids with conservation of juvenile stages allows for the investigation of complete ontogenetic transformations of conch geometry and is particularly suitable for studying ontogenetic allometry (Korn, 2012).
Data for the study of ontogenetic allometry can be classified in two principal groups (Klingenberg, 1998): (1) "crosssectional data", in which individual specimens are measured at a single stage and (2) "longitudinal data", in which each individual is measured multiple times during growth.Only the second class makes it possible to assess the individual variability of ontogenetic allometry.Ammonoids can be regarded as excellent study objects for the acquisition of "longitudinal data" (Korn, 2012).
In the following we present a study on the morphological evolution of the family Cymaclymeniidae based on material from the Anti-Atlas of Morocco.Of the eight discriminated North African species of the family, six were analysed in terms of conch ontogeny using data acquired from conch cross sections.
2 Allometric growth in ammonoids Gould (1966), Klingenberg and Froese (1991) and Klingenberg (1996Klingenberg ( , 1998) ) reviewed the principles of allometry.Allometry in the simplest form can be expressed by the power function where y is a variable (e.g. the width of an ammonoid conch), x the reference parameter (e.g. the diameter of an ammonoid conch), b a constant for the calculation (e.g. the ratio between conch width and conch diameter) and the allometry coefficient a measures the deviation from isometry.Values of a greater than 1 express positive allometry, and values of a lower than 1 indicate negative allometry; they thus document different ontogenetic trajectories of x and y.Isometry occurs where a = 1.
Ammonoids usually possess planispiral conchs with perfect bilateral symmetry.The study of their growth including data acquisition can best be achieved using high-precision cross sections, i.e. cross sections meeting the protoconch (i.e. the initial chamber of the conch that coincides with the centre of coiling) at its largest diameter.From such cross sections, two data sets can be obtained for each volution, meaning that growth increments of the conch spiral with a distance of 180 degrees can be studied.These growth increments are defined by the so-called Raupian conch parameters (Raup and Michelson, 1965;Raup, 1966Raup, , 1967;;Korn andKlug, 2003, 2007;Korn, 2010) as well as by the shape of the aperture (e.g.Simon et al., 2010Simon et al., , 2011)).Palaeozoic ammonoids never show isometric growth.Linear allometry (i.e.growth with an invariable allometry constant a) is also very rare.Instead allometric growth in ammonoid conchs most frequently occurs not only with a dynamic a but also with uncoupled changes of a with respect to the different conch parameters (Fig. 1).Three modes of ontogenetic allometry can be seen in ammonoids: (1) monophasic allometry (which can be linear or non-linear), (2) biphasic allometry and (3) triphasic or polyphasic allometry (Kullmann and Scheuch, 1970;Kant, 1973).Each of the three cardinal conch parameters -conch width index (CWI), umbilical width index (UWI) and whorl expansion rate (WER)may display allometric growth.The combination of the three different modes of allometry expressed in the three conch parameters enables a large variety of ontogenetic trajectories realised within the Ammonoidea.

Published by Copernicus
The Late Devonian Cymaclymenia is, in its adult conch geometry, a genus with a morphology that repeatedly occurs during the evolutionary history of the Ammonoidea; it represents the average conch morphology with respect to the three cardinal conch parameters.Furthermore, the genus belongs to those Palaeozoic ammonoids with moderately strong ontogenetic changes of the conch.However, just this "mediocrity" makes Cymaclymenia an interesting study object, because in this, some of the main principles of Palaeozoic ammonoid conch ontogeny can be investigated.

The family Cymaclymeniidae
Towards the end of the Devonian and shortly before the extinction of the majority of ammonoid lineages at the Hangenberg event, the clymeniid ammonoids are characterised by occupation of a wide morphological spectrum.The morphological disparity of the clymeniids is expressed by a wide range of conch morphology (from serpenticonic to discoidal and globular shapes), suture lines (from extremely simple with only one wide lateral lobe to rather complex with a number of pointed lobes) and shell ornament (from absence of coarse ornament to ribs and spines).Cymaclymenia shows, in many respects, a morphology within the centre of the clymeniid morphospace.
Cymaclymenia is the geographically most widespread of all clymeniid genera with occurrences in a large number of places in central Europe, Spain, Great Britain, the South Urals, North Africa, Australia, etc.; it usually outnumbers all of the other genera in the late Famennian ammonoid assemblages.The genus Cymaclymenia contains about 20 species (Korn and Ilg, 2007), which are mainly separated be means of conch geometry and suture line  Korn, 1999;Becker et al., 2002) with the approximate stratigraphic occurrences of the cymaclymeniid species in the Anti-Atlas of Morocco (T., Tournaisian; Fr., Frasnian).(Korn, 1981).Cymaclymeniids occur throughout the late Famennian (Fig. 2), and the family provides rich study material.
The evolutionary lineage of the cymaclymeniids was the only one among the clymeniids that survived the global Hangenberg event near the Devonian-Carboniferous boundary (Korn et al., 2004), one of the most severe extinction events for the Ammonoidea.However, these failed survivors became extinct shortly after the event without descendants.
The three genera Cymaclymenia, Procymaclymenia and Postclymenia can be separated on the basis of their suture lines (Fig. 4).Procymaclymenia, as the stratigraphically oldest genus, possesses a small, blunt and nearly symmetric lateral lobe, while the lateral lobe in Cymaclymenia is strongly asymmetric and pointed on the ventral side.The stratigraphically youngest genus Postclymenia possesses a very large, strongly asymmetric lateral lobe.

Origin of the study material
All specimens of Cymaclymenia and related genera, on which this study is based, were collected in the eastern Anti-Atlas of Morocco, which is known as a magnificent source of study material for long timescales (e.g.Petter, 1959Petter, , 1960)).Marvellous outcrop conditions and good preservation of the fossils in this region serve as excellent preconditions for such a study.Furthermore, the palaeogeography (Wendt, 1985(Wendt, , 1988) ) and stratigraphy of the Famennian sedimentary succession (e.g.Korn, 1999;Becker et al., 2000Becker et al., , 2002) ) have been intensely studied and form a framework for further, more detailed investigations.The most important localities (Fig. 5), from which the studied material derived, are as follows (Appendix Table A1): -Ouidane Chebbi (Tafilalt Basin), -Bordj d'Erfoud, Bou Ifarherioun and El Atrous (Tafilalt Platform), -Taourirt, Bou Tlidat, Lambidia and Madène el Mrakib (Ma'der Basin), -Lalla Mimouna (Ma'der Platform).

Principles of morphometrics
Morphometrics is the quantitative description, analysis and interpretation of form and form modification in the field of biology.Bookstein (1991) characterised morphometrics as the science of covariance of biological form.The objects of morphometric studies are thus not the forms as such, but their interrelationships, origins and causes.
The comparison of anatomical properties of organisms has been a central theme in biology for centuries.In the early 20th century the analysis of morphology became increasingly quantitative (Bookstein, 1998), and the development of statistical methods such as the calculation of a correlation coefficient (Pearson, 1895), variance analysis (Fisher, 1935) and principal component analysis (PCA) (Pearson, 1901;Hotelling, 1933) led to a large number of analytical tools.In the traditional morphometrics, multivariant statistical analyses using quantitative sets of variables (e.g.length, width and height of distinct features) were applied.In the late 1980s and early 1990s, a change began towards "geometric morphometrics", in which geometric structures under interest were used for more complete analyses; these allowed for a regression of statistical results in geometric structures (Rohlf and Marcus, 1993;Adams et al., 2004;Mitteroecker and Gunz, 2009).The most widespread among the methods of geometric morphometrics is the analysis of landmarks and outlines, as achieved in the Fourier analysis (for reviews, see MacLeod, 2002;Adams et al., 2004).

Data acquisition
From digitised drawings of conch cross sections, three of the basic conch dimensions can immediately be obtained for each half volution (for a detailed description of the parameters, see Korn, 2012) (Fig. 6): -conch diameter (dm); for some calculations the log diameter (dm log ) is used here, -whorl width (ww), -whorl height (wh).

Outline tracing and Fourier analysis
In the outline analysis in geometric morphometrics, as used in the Fourier analysis, points along a contour are digitised (Adams et al., 2004).For the analysis of conch cross sections, we therefore produced outline images for each half whorl of all growth stages larger than 1 mm conch diameter; the earliest stages below 1 mm diameter were excluded because of the large impact of minor measurement error.Data collection was done using the program tpsDig (Rohlf, 2006); we used 500 coordinates for each outline (Simon et al., 2010).
Fourier analysis is probably the most frequently used method for outline analyses (Wills, 2001); for the analysis of complex forms, the use of the elliptical Fourier analysis is required (Kuhl and Giardinia, 1982;Ferson et al., 1985;Temple, 1992;Crampton, 1995;Haines and Crampton, 2000).The transformation of the outline data into periodical functions is here achieved by the programs hangle and hmatch, in which 22 Fourier coefficients were calculated (Simon et al., 2010(Simon et al., , 2011)).Using these Fourier coefficients, the curves are analysed by a principal component analysis (Adams et al., 2004).

Ontogenetic trajectories of the analysed species
For the graphic visualisation of the ontogenetic trajectories, we produced diagrams that show the conch diameter on the x axis (as log values according to the logarithmic growth of ammonoid conchs) and the conch parameters (CWI, UWI and WER) on the y axis (Fig. 7 using the example of Cymaclymenia lambidia).These diagrams demonstrate that the conchs of Cymaclymenia and related genera deviate from isometric growth (in which the parameters would always have the same value).Allometric growth is the rule, and the allometry is non-linear with the separation of distinct phases.
The illustration of conch proportions and expansion rates in bivariate plots (with the diameter of the conch on the x axis) allows the detection of the following ontogenetic trends, which are shared by all investigated species of the family Cymaclymeniidae: -All of the three conch parameters CWI, UWI and WER show allometric development; the adult conchs differ more or less significantly from the juveniles.
-Almost none of these parameters show linear allometry; biphasic or triphasic ontogenetic trajectories are   predominant.This means that the allometry coefficient a changes during ontogeny.
-CWI and UWI generally decrease during ontogeny; however, the rates differ between the various species.
-In all species, the largest relative umbilical width (UWI = 0.35-0.50)occurs in the early juvenile stage between 2 and 4 mm conch diameter.Thereafter the UWI decreases in the intermediate stage; the adult stage is often characterised by a stable UWI.
-The WER decreases in early ontogeny (to 1.80 at 2-3 mm conch diameter) and increases later in ontogeny.
In the general ontogenetic trends, Cymaclymenia and its relatives resemble the majority of Palaeozoic ammonoids.The investigated species share some common characters with respect to their conch ontogeny, but they also show differences, which allow for a separation (Table 1).

Morphological disparity of the metric conch parameters
The morphometric data of the cardinal conch parameters (CWI, UWI, WER) of the cymaclymeniid conch cross sections were analysed using a principal component analysis (PCA).In this analysis, only growth stages larger than 1 mm  were included.Additionally to the cymaclymeniids, three extreme morphologies of the Devonian ammonoids are included to point at the range and position of the cymaclymeniids in the total morphospace (Fig. 8).The analysis used the correlation mode; of the three resulting PCA axes, PC1 expresses 56.8 % (negative values refer to a reduction of the UWI and increasing WER values) of variation and PC2 expresses 35.6 % (positive values refer to increasing CWI values).
In the triangular morphospace of the Devonian ammonoids (Korn and Klug, 2012), the growth stages of cymaclymeniids cover only a relatively small area (Fig. 8).This means that their juvenile and adult stages show a limited morphological range when compared with extreme morphologies.All investigated specimens show a migration within the morphospace with a loop in early ontogeny and later a migration along the x axes from positive to negative values.The latter reflects a morphological development from widely umbilicate juvenile conchs with a low aperture towards narrowly umbilicate, discoidal or pachyconic conchs with a higher aperture.Differences between the genera and species are mainly expressed in the conch width index (expressed by variations in the y axis) and the timing of developmental events such as changes in allometry.
The occupied areas of the six species display some overlap; a clear separation of the species within the scatter plot is thus not possible (Fig. 9).
The studied species show different ontogenetic pathways in the scatter plot of the PCA diagram, demonstrating the most important differences in conch ontogeny: -Cymaclymenia carnata is the widest form and therefore has a position at the upper margin of the scatter plot with high values in PC2.Cymaclymenia lambidia has an intermediate position, and the four species Cymaclymenia subvexa, www.foss-rec.net/17/1/2014/Foss.Rec., 17, 1-32, 2014 Cymaclymenia formosa, Procymaclymenia ebbighauseni and Postclymenia calceola are, because of their slender conch width, at the lower margin (negative values in PC2).
-Procymaclymenia ebbighauseni, Cymaclymenia subvexa, as well as Cymaclymenia formosa show very similar ontogenetic pathways and cannot be separated from each other.Postclymenia calceola differs from these species in the shortened ontogeny, which does not express the terminal, more narrowly umbilicate stage.Adult specimens of Postclymenia calceola occupy an area in the morphospace, which is typical for intermediate stages of the three species of Cymaclymenia.

Morphological disparity of outline shapes (Fourier analysis)
For a comparison with the results gained in the morphometric analysis, we achieved an alternative method for the depiction of the morphological changes in conch ontogenythe analysis of outline shapes in an elliptic Fourier analysis (Crampton, 1995;Haines and Crampton, 2000;Simon et al., 2010).The analysis used the variation-covariation mode; of the resulting PCA axes, PC1 expresses 44.7 % of variation and PC2 expresses 19.6 %.
We illustrate a second morphospace based on a Fourier analysis of the outline shapes with subsequent PCA (Fig. 10).In this diagram illustrating the first two axes of the PCA, all ontogenetic trajectories migrate along the x axes from positive to negative values.It is striking that in juvenile and adult stages, all species are plotted in similar areas, while the intermediate stages show the largest differences between the species.Another striking fact is that the PCA scatter plots of the morphometric data and the outline data closely resemble each other.Cymaclymenia carnata has a position at the upper margin of the occupied morphospace (e.g. with highest y values), followed downwards by Cymaclymenia lambidia, Cymaclymenia formosa, Cymaclymenia subvexa, Procymaclymenia ebbighauseni and Postclymenia calceola, which have a position at the lower margin of the morphospace (negative PC2 values).17, 1-32, 2014 www.foss-rec.net/17/1/2014/C. Klein and D. Korn: A morphometric approach to conch ontogeny of Cymaclymenia

Characters for the separation of species
The studied conch parameters CWI, WWI, UWI and WER allow for a clear separation of cymaclymeniid species (for the dimensions and conch proportions, see Appendix Table A2).This is confirmed by very similar results gained by the analysis of the metric data and the Fourier data.The analysis of the metric data allows for a separation of five of the species.Procymaclymenia ebbighauseni, Cymaclymenia subvexa and Cymaclymenia formosa are morphologically very similar and therefore hardly separable by morphometric data.A separation of these species is mainly possible by the suture line (Fig. 4).
Cymaclymenia carnata and Cymaclymenia lambidia can be separated from the four species Cymaclymenia formosa, Cymaclymenia subvexa, Procymaclymenia ebbighauseni as well as Postclymenia calceola by the conch width index (CWI or ww / dm).Postclymenia calceola can easily be separated from Cymaclymenia formosa and Cymaclymenia subvexa because Postclymenia calceola is the only one of the analysed species that is widely umbilicate throughout ontogeny.Cymaclymenia formosa and Cymaclymenia subvexa can probably not be separated by means of outline analysis.

Ontogenetic and phylogenetic implications
The three analysed cymaclymeniid genera have a successive stratigraphic occurrence, but this criterion alone does not mean that they represent a phyletic lineage.According to the increasing complexity of the suture lines, however, it may be postulated that a general lineage from Procymaclymenia over Cymaclymenia and finally Postclymenia is most plausible.However, closer relationships between the analysed species cannot be solved here.As we analysed material from the Anti-Atlas of Morocco only, possible immigrations from other regions may have contributed to the evolution of the lineage.
All investigated species are characterised by very similar ontogenetic trajectories; differences can be seen mainly in the conch width index (CWI) of the three species Cymaclymenia carnata, Cymaclymenia lambidia and Cymaclymenia subvexa.The latter, Cymaclymenia formosa and Procymaclymenia ebbighauseni, do not differ in this respect.This means that, if Cymaclymenia is derived from Procymaclymenia, changes in the ontogenetic trajectories are not traceable and thus not valuable for phylogeny.The two genera are separated by their suture line, which in Cymaclymenia is more derived with a strongly asymmetric, pointed lateral lobe.
Postclymenia calceola, the stratigraphically youngest species, shows a similar CWI like Cymaclymenia formosa and Procymaclymenia ebbighauseni, but does not reach the narrowly umbilicate adult stage like the genera Cymaclymenia and Procymaclymenia; instead it remains in the widely umbilicate stage characteristic of specimens of intermediate size of the other two genera.This shortening of morphological development by the loss of the adult stage, but by maintenance of size, can be regarded as a heterochronic process leading to neoteny (McNamara, 1986).An ontogenetic recapitulation of phylogeny is thus not present in this case.

Systematic descriptions (D. Korn)
Cymaclymenia is one of the most widespread clymeniid genera and often occurs in large numbers of individuals.It is thus an important genus for the investigation of provincialism and cosmopolitism.However, before detailed global comparison can be made, it is important to answer the following questions: -How many species of Cymaclymenia (and closely related genera) are possibly represented in existing collections?-What are the geographic ranges of the various species?-Does provincialism or cosmopolitism dominate the geographic distribution?-Are trends in the morphological evolution within the Cymaclymeniidae parallel in the various occurrences?
In the course of a revision of the cymaclymeniid ammonoids from Morocco, it became obvious that there is general similarity with species from other regions, but that a detailed investigation with the increase of the number of characters revealed morphological differences.These differences are used here to separate the North African material with the consequence of describing new species.
A total of 1100 specimens of Cymaclymenia and related genera from various localities in the Anti-Atlas of Morocco form the basis for the systematic description below.The entire material is stored in the collection of the Museum für Naturkunde Berlin (MB.C. number prefixes).The description follows the scheme proposed by Korn (2010) for Carboniferous ammonoids.
Genus definition: Genus of the Cymaclymeniidae with blunt, slightly asymmetric lateral lobe.
Discussion: Procymaclymenia is a genus that closely resembles Cymaclymenia in conch shape, but differs in the less developed lateral lobe.While this lobe in Cymaclymenia is strongly asymmetric and pointed at the ventral side, it is less asymmetric in Procymaclymenia and does not show the acute ventral side.The genus has thus an intermediate position be-tween Genuclymenia (with widely rounded lateral lobe) and Cymaclymenia (with acute lateral lobe).
The genus has a much more restricted geographic occurrence than Cymaclymenia.Records are so far only known from the Holy Cross Mountains (Czarnocki, 1989), the South Urals (Nikolaeva and Bogoslovsky, 2005) and North Africa.
The new species was utilised by Becker et al. (2002) as an index for the "Cymaclymenia pudica Zone", which has a position between the "Platyclymenia annulata Zone" and the "Sporadoceras orbiculare Zone".The authors provide a list of co-occurring species, predominantly platyclymeniids and prionoceratids.Recent bed-by-bed research, however, has demonstrated that Procymaclymenia ebbighauseni occurs higher in the section than postulated by Becker et al. (2002); a co-occurrence of typical species of the Platyclymenia annulata Zone and P. ebbighauseni does not exist.In the section at Madène el Mrakib, P. ebbighauseni has its lowest occurrences immediately below the oldest horizon with "Sporadoceras orbiculare".
Genus definition: Genus of the Cymaclymeniidae with pointed, strongly asymmetric lateral lobe.Course of the growth-lines biconvex.
Discussion: Cymaclymenia is one of the most species-rich Devonian ammonoid genera; Korn and Klug (2002) listed 40 species within the genus, of which several were regarded as synonymous.A further seven new species were added by Nikolaeva and Bogoslovsky (2005) to Cymaclymenia, but three of these can be regarded as probably belonging to Procymaclymenia, a genus ignored by these authors.This large amount of morphologically similar forms is an obstacle for a clear separation of species, of which only few have been described including the conch ontogeny.Furthermore, the precise stratigraphic occurrence is not known for many species for which, if at all, only the stage is known.
The material of Cymaclymenia from Morocco and Algeria has traditionally (e.g.Petter, 1960;Korn, 1999;Becker et al., 2002) been assigned to species previously described from central Europe (e.g.Franconia, Rhenish Mountains).In fact there is some resemblance, but at the same time there are differences when well-preserved material is studied and compared.Generally it appears that the material from the Anti-Atlas has a weaker shell ornament when compared with the European species, while differences in conch geometry and suture lines are only minor.The differences in shell ornament are used here as a criterion for the separation of new species within the genus, giving the cymaclymeniid faunas from North Africa an exotic character containing endemic species.
A concept of largely endemic faunas has been used by Nikolaeva and Bogoslovsky (2005), who besides using names from central European species, named four new species from the South Urals and central Kazakhstan.
C. formosa differs from C. subvexa from the Anti-Atlas in the nearly parallel flanks in the adult stage, which in C. subvexa converge more strongly towards the narrow venter.
Discussion: Cymaclymenia lambidia belongs to the stouter species of the genus and is by this character separated from most of the other species such as the co-occurring C. lam-bidia.Only few of the described species reach the adult ww / dm ratio of 0.35.Specimens belonging to this new species have usually been assigned to Cymaclymenia involvens Lange, 1929.Indeed this species is very similar in conch shape (Fig. 22), and differences are mainly expressed in shell ornament.Two specimens from Wocklum are available from the type material of C. involvens: (1) the smaller holotype MB.C.3695 (27 mm dm), which is fairly well preserved with a rather coarse shell ornament, and (2) the larger paratype  MB.C.3695 (42 mm dm), which is a poorly preserved, rather strongly corroded internal mould providing insight into the adult conch morphology.It is not certain that the two specimens belong to only one species.However the stratigraphic restriction of the type locality, in which almost exclusively the topmost Wocklum Limestone (Wocklumeria denckmanni Zone) yields ammonoids, suggests that the material is conspecific.The most probable stratigraphic position of the topotypes allows for the designation of time-equivalent specimens for a more precise characterisation of the species.C. involvens differs from the other central European species of the genus in the stouter conch, which only in C. nephroides Korn, 1981 is even wider.Like the other two very common species C. striata (Münster, 1832) and C. costellata (Münster, 1832), it possesses a rather coarse shell ornament with bundled growth lines and weak riblets around the umbilicus.C. lambidia differs from the European and Uralian species in the much weaker ornament, which particularly in subadult specimens (about 20 mm conch diameter) appears to be absent and thus suggesting a smooth shell surface.Another difference of the new species from C. involvens is the slightly stouter conch in the juvenile stage of 8 mm conch diameter (ww / dm = 0.45-0.50 in C. lambidia; ww / dm = 0.53 in C. involvens) (Fig. 23).This criterion, however, probably does not allow for a clear separation of the two species.Becker et al. (2002, p. 165, 173) introduced a "Cymaclymenia involvens Zone" for specimens of this species.This zone should occur between sandstone members near the top of Late Devonian succession at Lambidia (Aguelmous, Ma'der Basin); the zone was placed above the "Hangenberg Black Shale event".However, the authors did not recognise a major fault in the outcrop, which causes duplication of the higher beds; the so-called Cymaclymenia involvens Zone is thus not justified.The beds assigned to this zone (unit R in figure 4 of Becker et al., 2002) are a repetition of unit J1 (i.e. a rock unit below the "Hangenberg Black Shale event").
Type locality and horizon: Erfoud (Anti-Atlas), immediately east of the Muslim cemetery on the eastern side of the Ziz Valley; bed 55 of Korn (1999), Parawocklumeria paradoxa Assemblage (late Famennian).
Material: 10 specimens with a maximum conch diameter of 45 mm.
Discussion: C. serotina differs from nearly all other species of the genus in the very faint conch ornament.The species differs from Cymaclymenia formosa and the other Moroccan species with slender conchs by the extremely fine ornament,  Material: 3 specimens with a maximum conch diameter of 60 mm.
Umbilical wall steep in the adult stage, flanks weakly converging, venter rounded.Ornament with rather coarse biconvex growth lines, without riblets; steinkern with curved constrictions on the flanks.
Discussion: C. aulax belongs to the few species of the genus with coarse steinkern constrictions.Münster (1832) described the species "Planulites semistriatus" from Franconia, which also belongs to Cymaclymenia.This species also possesses steinkern constrictions on the flanks and venter.
The new species differs from the other species of Cymaclymenia from the Anti-Atlas by the presence of conspicuous steinkern constrictions.C. formosa is the most similar of the other species, but C. aulax also differs in the increasing umbilical width index in the adult stage.
Material: 2 specimens with a maximum conch diameter of 55 mm.
Genus definition: Genus of the Cymaclymeniidae with thinly discoidal, weakly ornamented conch.Suture line with large, extremely asymmetric and ventrally elongated lateral lobe.Umbilical lobe widely rounded.
The genus consists only of two species: the type species and a new species described here.For a discussion of the genus, see Korn et al. (2004) and Korn et al. (2007).
Discussion: Postclymenia evoluta has a very similar or nearly identical conch but differs from the new species in the suture line, which possesses a smaller adventive lobe with a vertical ventral side of the adventive lobe, as figured by Schmidt (1924, pl. 8, fig. 19) and Price and Korn (1989, fig. 11A).For a detailed description and discussion of the new species, see Korn et al. (2004) and Korn et al. (2007).

Figure 5 .
Figure 5. Geological map of the eastern Anti-Atlas of Morocco with the most important localities of cymaclymeniid ammonoids.

Figure 6 .
Figure 6.Conch dimensions, conch proportions and expansion rates (growth rates) obtained from ammonoid conch cross sections.

Figure 8 .
Figure 8. Morphospace of cymaclymeniid specimens (grey dots) in the scatter plot of the first two PCA axes.Three examples of Devonian ammonoids ranging in the corners of the triangular total morphospace are shown: (A) Carinoceras as a slender, involute ammonoid with high aperture, (B) Prolobites as a globular, involute ammonoid with low aperture and (C) Phenacoceras as a slender, evolute ammonoid with low aperture.
Furthermore C. subvexa has a more slender juvenile conch at 4 mm diameter (ww / dm ∼ 0.34 in C. formosa but ∼ 0.30 in C. subvexa).The best criterion for the separation of the species is the form of the umbilical wall, which in C. formosa is steep, but oblique in C. subvexa (about 45 • ).C. serotina differs from C. formosa in the almost smooth shell surface.C. subcompressa Nikolaeva and Bogoslovsky, 2005 and C. pseudocompressa Nikolaeva and Bogoslovsky, 2005 have a similar shape, but the first species has an almost smooth shell and the second has lamellar growth lines, much coarser than in C. formosa.

Table 1 .
Ontogenetic trajectories of the analysed species.

Table 2 .
Conch ontogeny of Procymaclymenia ebbighauseni n. sp.from the Anti-Atlas of Morocco.

Table 3 .
Conch ontogeny of Cymaclymenia subvexa n. sp.from the Anti-Atlas of Morocco.

Table 4 .
Conch ontogeny of Cymaclymenia formosa n. sp.from the Anti-Atlas of Morocco.

Table 6 .
Conch ontogeny of Cymaclymenia serotina n. sp.from the Anti-Atlas of Morocco.

Table 7 .
Conch ontogeny of Cymaclymenia carnata n. sp.from the Anti-Atlas of Morocco.

Table 8 .
Conch ontogeny of Postclymenia calceola n. sp.from the Anti-Atlas of Morocco.

Table A2 .
Conch measurements and ratios of selected specimens of Cymaclymenia and related genera.