Localities
The specimens derive from several sections in the eastern Anti-Atlas (Supplementary Fig.
1A, B). More information on these localities can be found in Belka et al. (1999), Klug (2001),
Klug et al. (2008) and De Baets et al. (2010). The ammonoid shells are preserved as threedimensional calcareous internal molds. They all come from a restricted stratigraphic interval
about 30 cm thick in the lower part of the Erbenoceras beds sensu Klug (2001). More
precisely, they derive from the upper part of Unit C (not associated with Lenzites gesinae) and
the lower part of Unit D (associated with Lenzites gesinae) of Klug (2001). This peculiar
stratigraphic interval is widely correlated throughout the Tafilalt area in Morocco (Bultynck
and Walliser 2000a, b; Klug 2001; Klug et al. 2008; De Baets et al. 2010).
Taxonomy
Morocco.— We qualitatively distinguished two groups in our Moroccan material based on
ontogeny, characteristics of ribbing (strength, spacing, shape), coiling mode (non-touching to
touching or advolute whorls) and other conch parameters. Twenty-three specimens of group I
and sixty-five specimens of group II with at least one demi-whorl preserved were available
for this study.
The first group (Fig. 2C-I) has thinly discoidal conchs (ww/dm = 0.12-0.18) with openly
coiled, crioconical to quasi-advolute whorls in the early to middle whorls and shows no
marked increase of the whorl interspace (“uncoiling”) or even a decrease in whorl interspace
at the end of ontogeny. They have a very wide umbilicus (uw/dm = 0.60-0.83), very low to
low whorl expansion rate (WER = 1.3-1.7), very low to low whorl height index (WHI = 0.120.24) and a strongly compressed whorl section (WWI = 0.62-0.79). They have coarse,
rectiradiate to moderately rursiradiate, straight to slightly sinuous ribs (RDW = 19-57, ARI40
= 4-26 > 40 mm dm; ARI20 = 8-19 < 40 mm dm).
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The second group (Fig. 2A-B, J-R) has a thinly discoidal conch (ww/dm = 0.15-0.19) with
openly coiled, quasi-advolute to advolute whorls in the early to middle ontogeny and shows a
marked increase of the whorl interspace (uncoiling) at the end of ontogeny. They have a wide
to very wide umbilicus (UWI = 0.54-0.72), moderate whorl expansion rate (WER = 1.5-1.9),
low to moderate whorl height index (WHI =0.18-0.28) and a strongly compressed whorl
section (WWI = 0.65-0.82). They have coarse, rectiradiate to moderately rursiradiate, straight
to slightly sinuous ribs (RDW = 13-38, ARI40 = 4-15 > 40 mm dm; ARI20 = 5-22 < 40 mm
dm).
The first group is more loosely coiled, has a more compressed whorl section, a lower
whorl expansion rate and less coarse, more densely spaced ribs than the second group at
similar diameters, especially in the early ontogeny. Group I largely corresponds to specimens
that would classically be assigned to Ruanites (now synonymized with Anetoceras: see De
Baets et al. 2009, in press for complete synonymies) due to their constantly high whorl
interspace, closely spaced ribs, and lower WHI as well as WER. Group II largely corresponds
with specimens that would be placed in Erbenoceras in the literature (see De Baets et al.
2009, in press for reviews) due to their lower WHI (and WER), more coarsely and less widely
spaced ribs as well as a low WII (Fig. 3C; Supplementary Fig. 2).
Specimens of the Moroccan Anti-Atlas have previously been ascribed to four species of
these two genera, which are all known to co-occur in the same beds (Termier and Termier
1950; Hollard 1963; Klug 2001; De Baets et al. 2010): Anetoceras obliquecostatum Ruan and
He, 1974; Erbenoceras advolvens (Erben, 1960); E. filalense (Termier and Termier 1950) and
E. solitarium (Barrande, 1865). E. filalense has been synonymized with E. advolvens (Hollard
1963; Montesinos and Truyols-Massoni 1987; Korn and Klug 2002). In our large sample of
Group II, we could not qualitatively demarcate multiple Erbenoceras species as they seem to
be part of a continuum (Figs. 2, 3; Supplementary Fig. 3). All the known Moroccan
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Anetoceras specimens were referred to A. obliquecostatum (Klug 2001; De Baets et al. 2010),
but our Group I shows great differences in coiling and ribbing (Figs. 2, 3). No clear separation
between separate taxonomic units could be made within this group as almost every
combination of characters states (e.g., in coiling, rib spacing) can be found (Fig. 5). Some
forms are clearly more tightly coiled than others (Supplementary Fig. 3D compared with 6G),
but have similar rib spacing (compare Supplementary Fig. 3W and 3AB, respectively). In
other cases, forms are similarly openly coiled (Supplementary Fig. 3E and 3F), but have a
markedly different rib spacing (Supplementary Fig. 3AC and 3V, respectively).
In none of the Moroccan specimens is the embryonic shell preserved. In some specimens,
parts of the first or second whorl are preserved judging from the smallest preserved adapical
whorl height and attenuating ornamentation (Fig. 2C-I for Anetoceras and Fig. 2A, B, J-R for
Erbenoceras; compare Bogoslovsky 1969; De Baets et al. in press).
Although our specimens were collected from two stratigraphical units (Klug 2001), the
two groups and different variants of each group are known to co-occur in the same beds
(compare Klug 2001; De Baets et al. 2010; Supplementary Appendix and Supplementary
Table 1). We even recovered most morphotypes from one single slab of Unit D (see
Supplementary Table 1; marked by asterisk next to the unit). For all these reasons, we suspect
our groups to represent two species, but these assignments need to be further corroborated by
quantitative analysis of variability through ontogeny and a unimodal (Gaussian) distribution
(see Results).
Worldwide.— Coarsely ribbed Anetoceratinae (genera Anetoceras and Erbenoceras) are
not only known from Morocco (see reviews in De Baets et al. 2009, in press), but have been
reported worldwide: China, Czech Republic, France, Germany, Novaya Zemlya, Russia,
Spain, Tajikistan, Turkey, United States, Vietnam, and Uzbekistan (Ruan 1996; Yolkin et al.
2000; Bardashev et al. 2005; De Baets et al. 2009, 2010, in press, and references therein).
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About 24 species have been erected worldwide (see reviews in De Baets et al. 2009, in press).
They have even been dubbed Anetoceras faunas (Chlupáč 1976). They are widely distributed
from subtropical latitudes in the northern hemisphere to subtropical latitudes in the southern
hemisphere during the early Emsian (Supplementary Fig. 1C).
For comparison with our Moroccan specimens, we re-measured specimens of previously
published Erbenoceras specimens (Supplementary Material Table 2) from the northern Urals
(Bogoslovsky 1969), Czech Republic (Chlupáč and Turek 1983), northern France, Turkey,
and the Rhenish Slate Mountains (Erben 1960, 1962) during several museum visits. These
data include the type material of E. advolvens (synonym of E. filalense); E. “fritschi”
(Barrande, 1877; synonym of E. solitarium according Korn and Klug 2002); E. sabolotnense
Yatskov, 1990 and E. solitarium (Barrande, 1865), a senior synonym of E. “barrandei” (de
Verneuil, 1866) according to Korn and Klug (2002).
We also scanned and re-measured well-figured specimens of Anetoceras (Supplementary
Material Table 2) introduced by Ruan (1981, 1996) from southern China, which include the
type material of Anetoceras luofense, A. obliquecostatus, A. serpentinum, and A. subtile. A
specimen similar to the type material of A. arduennense (Kutscher, 1933) from the Rhenish
Slate Mountains was also included (De Baets et al. 2009).
Some taxa (Erbenoceras elegantulum, E. erbeni, E. kimi) reported from China, USA or
Uzbekistan (House 1965; Bogoslovsky 1980; Ruan 1981; Yatskov 1990; Becker et al. 2010)
clearly distinct from our Moroccan specimens due to their smaller size, different whorl cross
section, whorl expansion rate, coiling mode, and/ or differences in ornamentation (see De
Baets et al. 2009, in press) were excluded from our analysis. From all the remaining taxa
(compare De Baets et al. 2009, in press), only fragmentary, distorted, and/ or flattened
material is available, which cannot be adequately compared with our material and is therefore
also excluded.
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Additional Literature Cited
Bardashev, I. A., N. P. Bardasheva, K. Weddige, and W. Ziegler. 2005. Stratigraphy and
facies of the Middle Paleozoic of parts of southern Tien-Shan in Tajikistan and
Uzbekistan. Palaeobiodiversity and Palaeoenvironments 85:319–364.
Becker, R. T., K. De Baets, and S. Nikolaeva. 2010. New ammonoids records from the lower
Emsian of the Kitab Reserve (Uzbekistan) – preliminary results. SDS Newsletter 25:20–
28.
Belka, Z., C. Klug, B. Kaufmann, D. Korn, S. Döring, R. Feist, and J. Wendt. 1999. Devonian
conodont and ammonoid succession of the eastern Tafilalt (Ouidane Chebbi section),
Anti-Atlas, Morocco. Acta Geologica Polonica 49:1–23.
Bogoslovsky, B. I. 1980. Early Devonian ammonoids of the Zeravshan Range.
Paleontological Journal, 1980(4):51–66. [in Russian.]
Bultynck, P., and O. H. Walliser. 2000a. Emsian to Middle Frasnian sections in the northern
Tafilalt. Notes et Mémoires du Service géologique du Maroc 399:11–20.
——. 2000b. Devonian Boundaries in the Moroccan Anti-Atlas. Courier Forschungsinstitut
Senckenberg 225:211–226.
Chlupáč, I. 1976. The oldest goniatite faunas and their stratigraphic significance. Lethaia
9:303–315.
House, M. R. 1965. Devonian goniatites from Nevada. Neues Jahrbuch für Geologie und
Paläontologie, Abhandlungen 122:339–342.
Scotese, C. R. 2001. Atlas of earth history. PALEOMAP Project, Arlington, Texas.
Verneuil, E. de 1866. Appendice à la faune dévonienne du Bosphore. Extraits de l’Asie
Mineure par P. de Tschihatcheff, IV, Paléontologie:425–495.
Yolkin, E. A., N. K. Bakharev, A. A. Alekseenko, N. G. Izokh, A. G. Klets, O. P.
Mezentseva, O. A. Rodina, and Y. V. Udodov. 2000. Emsian (Lower Devonian)
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ammonoids and tentaculites from the Kuvash reference section of the Gorny Altai
(southern West Siberia). News of Paleontology and Stratigraphy 2-3:189–194. [in Russian
with English abs.]
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