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Abstract and Figures

Trilobites are widespread in Early Devonian deposits of north Gondwana; some of the most emblematic ones were collected from the famous latest Emsian (Early Devonian) mudmound locality Hamar Laghdad in south-eastern Morocco. This locality is famous for its trilobites, especially for the conspicuous red-coloured remains of phacopid trilobites with often greenish eyes. Here, we present a taxonomic revision of the previously described trilobites from the so-called Red Fauna of Hamar Laghdad. We introduce the new taxa Harpes hamarlaghdadensis n. sp. and Morocops davidbrutoni n. sp. Phacopids dominate the trilobite assemblage from the Red Cliff at Hamar Laghdad in terms of the number of specimens (represented by Morocops) as a whole. Additionally, we focus on the description of trilobite diversity of this interval compared to Algerian assemblages.
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Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar
Laghdad, Morocco and their biodiversity
Catherine Crônier, Morgane Oudot, Christian Klug, and Kenneth De Baets
With 11 figures and 2 tables
Abstract: Trilobites are widespread in Early Devonian deposits of north Gondwana; some of the most
emblematic ones were collected from the famous latest Emsian (Early Devonian) mudmound locality
Hamar Laghdad in south-eastern Morocco. This locality is famous for its trilobites, especially for the
conspicuous red-coloured remains of phacopid trilobites with often greenish eyes. Here, we present
a taxonomic revision of the previously described trilobites from the so-called Red Fauna of Hamar
Laghdad. We introduce the new taxa Harpes hamarlaghdadensis n. sp. and Morocops davidbrutoni n.
sp. Phacopids dominate the trilobite assemblage from the Red Cliff at Hamar Laghdad in terms of the
number of specimens (represented by Morocops) as a whole. Additionally, we focus on the description
of trilobite diversity of this interval compared to Algerian assemblages.
Keywords: Trilobita, Emsian, Tafilalt, eastern Anti-Atlas, taxonomy, diversity, variability.
1. Introduction
Trilobites are important elements of the Devonian
macrobenthos (Crônier & van viersen 2007). During
the Early Devonian, the basal Pragian eustatic sea level
rise (House 2002) and the climate warming (vaCek
2011) contributed to the development of shallow marine
carbonate realms, which were favourable environments
for trilobites (C
hlupáč
1994). This led to an increase
of their generic diversity and to a continuously high
diversity of families, with some minor changes until
the early Eifelian (Chlupáč 1994; Crônier & Van
viersen 2007). The publications of alberti (1969,
1970, 1981a), M
orzadeC
(1997, 2001), C
Hatterton
et
al. (2006), MCkellar & CHatterton (2009), Gibb &
CHatterton (2010), kHaldi et al. (2016), van viersen
& Holland (2016), Crônier et al. (2018) represent
major contributions to our current knowledge of North
African Early and early Middle Devonian trilobites.
The present paper is a contribution to the systematic
study of Early Devonian trilobites especially from the
famous locality Hamar Laghdad in the eastern Anti-
Atlas (k
luG
et al. 2018). The material described here
has become known because of its peculiar preservation,
where the exoskeleton of some trilobite specimens is
red except for the lenses, which are often greenish in
colour (kluG et al. 2009). Most of the exoskeleton is
silicified and contains elevated concentrations of iron
oxides, which causes the red colour while the lenses
retained more or less their original calcitic composition,
possibly greenish due to Fe- and Mn-impurities (kluG
et al. 2009). Numerous newly collected specimens give
us the opportunity to describe these forms better and to
explore their palaeobiodiversity.
2. Material
All specimens were collected from marls containing
limestone nodules in the Moroccan eastern Anti-
Atlas by us at the ‘Red Cliff’ (k
luG
2002) in Hamar
Laghdad, located about 18 km ESE of the town Erfoud
©2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany www.schweizerbart.de
DOI: 10.1127/njgpa/2018/0781 0077-7749/2018/0781 $ 9.00
N. Jb. Geol. Paläont. Abh. 290/1-3 (2018), 241–276 Article
Stuttgart, November 2018
E
eschweizerbart_xxx
242 Catherine Crônier et al.
(Fig. 1) and are of latest Emsian age (kluG et al. 2009,
2018). They are quite well-preserved owing to a partial
silicification (kluG et al. 2009).
Hamar Laghdad is a locality world-renowned for
its more or less completely exhumed mud-mounds
(hollard 1974; alberti 1982; braChert et al.
1992; Wendt 1993; belka 1998; aitken et al. 2002;
Cavalazzi et al. 2007). This locality is also famous
for its trilobites (e.g., alberti 1969, 1982; Feist &
CHatterton 2015; Feist & belka 2018). Among other
materials, it yielded some red-colored remains of
phacopid trilobites with often greenish eyes (k
luG
et
al. 2009). This locality also yields abundant remains
of other organisms including numerous taxa of, e.g.,
cephalopods (kluG 2002; kluG et al. 2009; PoHle &
k
luG
2018), echinoderms (b
erkoWski
& k
luG
2012;
kluG et al. 2014; Waters & kluG (2018) and corals
(berkoWski 2006, 2008, 2012, 2018; król et al. 2018)
associated with the red-coloured remains of phacopids.
3. Systematic palaeontology (C. Crônier)
Morphological terminology follows Chlupáč (1977) and
C
rônier
et al. (2011) for phacopids and W
HittinGton
et
al. (1997) for proetids. Some abbreviations have been
used: ‘exsag.’ for exsagittal, ‘sag.’ for sagittal, ‘tr.’ for
transverse, ‘L0L1’ for occipital and preoccipital lobes,
Fig. 1. (a) Maps of Morocco and the Tafilalt (eastern Anti-Atlas). (b) Location of the ‘Red Cliff’ at Hamar Laghdad.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 243
‘S0S3’ for glabellar furrows, ‘abax.’ for abaxially,
‘adax.’ for adaxially, and ‘α, γ, δ, ε, ω’ for different
salient points along the course of the facial suture in
proetids.
The trilobite specimens described in the
present paper are housed at the collection of the
Paläontologisches Institut und Museum of the
Universität Zürich (PIMUZ numbers).
Order Phacopida salter, 1864
Family Phacopidae HaWle & Corda, 1847
Subfamily Phacopinae HaWle & Corda, 1847
Genus Morocops basse, 2006
(= Genus Barrandeops MCkellar & CHatterton,
2009)
Type species: Phacops (Phacops) sparsinodosus struvei
sCHraut, 2000b, early Eifelian Timrhanrhart Formation,
Morocco.
Additional species: Morocops chattertoni (kHaldi et
al., 2016), late Emsian, Algeria; M. forteyi (MCkellar &
CHatterton, 2009), late Emsian, Morocco; M. granulops
(CHatterton et al., 2006), late Emsian, Morocco, Algeria;
M. lebesus (CHatterton et al., 2006), Eifelian, Morocco;
M. ovatus (M
C
k
ellar
& C
Hatterton
, 2009), late Emsian,
Morocco; M. torkozensis (sCHraut, 2000a), ? late Emsian,
Morocco; M. spinifer
van
v
iersen
et al., 2017, late Emsian,
Morocco.
Emended diagnosis: See van viersen et al. (2017) but eye
bearing 14-19 dorso-ventral files of lenses with 3-6 lenses
per file.
Remarks: In order to include Morocops chattertoni
(kHaldi et al., 2016) and the new species described here,
an emended diagnosis (above) is proposed. See van viersen
et al. (2017) for a taxonomical consideration. As suggested
by van viersen et al. (2017), potential other species (i.e.,
Phacops (Phacops) tafilaltanus a
lberti
, 1983) of Morocops
have been described especially in Morocco from late Emsian
strata of Hamar Laghdad (e.g., alberti 1983, pl. 2, fig. 12).
Morocops granulops (CHatterton, Fortey, brett,
Gibb & MCkellar, 2006)
Fig. 2a-q
v. non 1952 Phacops cf. turco. – Le Maître, p. 157, pl. 21, fig.
7.
2006 Phacops granulops CHatterton et al., p. 12, pl.
1, figs. 1-10, pl. 2, figs. 1-12, text-fig. 3.4.
2009 Barrandeops granulops. – MCkellar & CHat-
terton, p. 44.
2009 Barrandeops cf. granulops. – k
luG
et al., p. 117,
text-fig. 2a-b.
2016 Barrandeops granulops. – K
Haldi
et al., p. 360-
362, 364, 376, 379, 383-384, text-fig. 3a-m, text-
figs. 9-11.
2017 Morocops granulops. – van viersen et al., p. 7.
2018 Morocops cf. granulops. – beCker et al., p. 193.
Type material: Enrolled exoskeleton UA13295, from the late
Emsian Timrhanrhart Formation, basal part of the section at
Jbel Gara el Zguilma, near Foum Zguid, Morocco.
Material: Nineteen cephala, five cephalothoraces and six
complete mostly enrolled exoskeletons (PIMUZ 35146 to
35151).
Diagnosis: See MCkellar & CHatterton (2009).
Remarks: The Moroccan specimens from the latest Emsian
of Hamar Laghdad show the main morphological features of
the Moroccan specimens formally described from the late
Emsian near Foum Zguid (CHatterton et al. 2006): coarse
conical tubercles, 19 dorso-ventral files of lenses (sometimes
18) with 4-5 lenses per file (exceptionnally 6), no pitting
between tubercles of the palpebral lobe and the palpebral
area, a postocular pad with tubercles concentrated distally,
a subocular area with fine, small, scattered granules, and a
row of small tubercles at the base of the eye. The smallest
specimen is 3.5 mm long (sag.) and has only 17 dorso-
ventral files of lenses with maximum three lenses per file.
The cephalic size and the dorso-ventral file distribution
have been discussed in the next section on inter- and intra-
specific variablity. According to C
Hatterton
et al. (2006),
Morocops granulops is most similar to Phacops (Phacops)
tafilaltanus alberti, 1983. In the impossibility to examine
this last species, it is difficult to say whether this species
could be co-specific or not; apparently not (i.e., visual
surface more rounded in lateral view and postocular pad
smaller in Morocops granulops).
Morocops forteyi (MCkellar & CHatterton, 2009)
Fig. 2r-u
non 1968 Phacops (Phacops) turco praecedens. – Haas, p.
108, pl. 30, fig. 7.
pt. 1977 [Phacops turco aff. praecedens. – Fortey & Mor-
ris, p. 25, pls. 1-2 [non pl. 1, fig. 7; pl. 2, fig. 3].
2009 Barrandeops forteyi MCkellar & CHatterton,
p. 49, pl. 15, figs. 1-12, pl. 16, figs. 1-12, pl. 17, fig.
1-12, text-figs. 16, 17.
2016 Barrandeops forteyi. – kHaldi et al., p. 360, 362.
2017 Morocops forteyi. – van viersen et al., p. 6, text-
fig. 5F-I, L, M.
Type material: Enrolled exoskeleton UA6942 from the late
EmsianPsychopyge’ horizon equivalent, Talawarite section,
near Jbel in the Tafilalt basin, southeastern Morocco.
Material: Five cephala (PIMUZ 35152).
Diagnosis: See MCkellar & CHatterton (2009).
eschweizerbart_xxx
244 Catherine Crônier et al.
Remarks: The Moroccan specimens from the latest Emsian
strata of Hamar Laghdad show the main morphological
features of the Moroccan specimens formely described from
the late Emsian of the Talawarite section, east of Derkaoua
in the Tafilalt (MCkellar & CHatt erton 2009): dense
coarse conical tubercles, 18 dorso-ventral files of lenses
with 4 lenses per file (only one eye with 3 lenses per file), a
pronounced sclera, tuberculate dorsal and ventral margins of
the eye, a deep palpebral furrow, an inflated and tuberculate
postocular pad, and a subocular pad with a little inflation
and few tubercles. The cephalic size and the dorso-ventral
file distribution are discussed in the section on inter- and
intraspecific variablity.
Morocops sp. A
Fig. 2v-y
Material: Two cephala (PIMUZ 35153).
Description: Cephalon: Length/ width ratio about 0.56.
Dorsal view: Glabellar ratio of width at L1/ maximum
width of frontal lobe about 0.52. Glabella bounded by
deep axial furrows that are highly divergent forward (75°),
with anterior portions less divergent forward. Frontal lobe
slightly overhanging a deep preglabellar furrow. S2 and S3
distinct. S1 continuous and curved more strongly forwards
than S0 in its adaxial curvature, and becoming deeper in
its distal portions. L1 shorter (sag.) than L0 (but more than
half L0 length) and with a wide (tr.) median portion relative
to its total width. Median portion of L1 inflated, with few
coarse tubercles. L1 with subcircular, inflated lateral lobes
separated from its median part by a strong exsagittal furrow.
S0 well-marked and transverse in its middle portion. L0
wide (tr.) with lateral lobes hardly defined. Reniform visual
surface with 19 dorso-ventral files of lenses and a maximum
of five lenses per file, with smaller lenses in the anterior
median part. Inter-lensar sclera strongly thickened dorsally
and more thickened than ventrally. Palpebral furrow well
distinct. A row of coarse tubercles with interspaced granules
present at the base of the visual surface. Top of the visual
surface with a thick margin composed of a row of coarse
tubercles. Subocular pad with a row of aligned and coarse
turbercles decreasing anteriorly. Exsagittal length of the
postocular genal field more than half the length (exsag.) of
the posterior border. Postocular pad inflated distally with
coarse tubercles concentrated. Cheek swollen.
Lateral view: Glabella rounded anteriorly, barely arched.
Outline of L1 curved. L0 as high as the glabella at its
maximum convexity. Anterior border short, ridge-like
slightly projecting forwards and sloping posteroventrally.
A strong marginulation extending from the antero-lateral
border up to the genal angle. Posterior border furrow deep
and narrow. Lateral border furrow moderately deep, narrow
behind the posterior branch of the facial suture and wider at
the front of the eye. Posterolateral border furrow continuous
and well-distinct. Posterolateral border widening at the genal
angle.
Frontal view: Glabellar outline subcircular with lateral sides
slightly flattened obliquely. Palpebral area slightly higher
than the palpabral lobe.
Ventral view: Badly preserved. Vincular furrow deep,
wide (sag.), curved and parallel to the preglabellar furrow.
Posterior band of the cephalic doublure eroded.
Sculpture: Cephalon covered with dense, coarse, moderately
high, conical tubercles of rather homogeneous size without
superimposed granules on glabella, palpebral lobe, genal
field, L0, and postero-lateral borders; smaller on preoccipital
lateral lobes. Tubercles becoming smaller on the external
part of the postero-lateral borders with interspaced granules.
Anterior band of the cephalic doublure and marginulation
with scaly ridges and elongated pits.
Remarks: The two specimens with a length about 18 mm
(sag.) show some morphological features of Morocops ovatus
(MCkellar & CHatterton, 2009) from the late Emsian
of Morocco such as coarse conical tubercles with dense
distribution, an eye with 19 dorso-ventral files and maximum
of five (commonly) lenses per file, and a raised intercalating
ring L1. However, our specimens show a subocular pad with
a row of aligned and coarse turbercles decreasing anteriorly;
M. ovatus is characterized by a weak subocular pad with
varying tubercle sculpture. M. ovatus has more elongated (tr.)
tubercles on L0 than in Morocops sp. A. The cephalic size
and the dorso-ventral file distribution have been discussed
in the section inter- and intra-specific variablity.
Morocops sp. A differs from Phacops (Phacops)
tafilaltanus alberti, 1983 in having a more pronounced
and coarse tuberculation and 19 dorso-ventral files of lenses
against 18 files for Phacops (Phacops) tafilaltanus.
Fig. 2. Phacopid trilobites from the late Emsian ‘Red Cliff’ at Hamar Laghdad, Tafilalt, Morocco. (a-e) Morocops granulops
(CHatterton et al., 2006), PIMUZ 35146: (a-d) cephalon in frontal, dorsal, lateral, and ventral views, (e) pygidium in dorsal
view. (f-i) Morocops granulops (CHatterton et al., 2006), PIMUZ 35147: small cephalon in left lateral, frontal, right lateral
and dorsal views. (j-k) Morocops granulops (CHatterton et al., 2006), PIMUZ 35148: cephalon in lateral and dorsal views.
(l-n) Morocops granulops (C
Hatterton
et al., 2006), PIMUZ 35149: (l) complete exoskeleton in lateral view, (m-n) cephalon
in frontal and dorsal views. (o-p) Morocops granulops (C
Hatterton
et al., 2006), PIMUZ 35150: cephalon in dorsal and
lateral views. (q) Morocops granulops? (CHatterton et al., 2006), PIMUZ 35151: detail of a left eye. (r-u) Morocops forteyi
(MCkellar & CHatterton, 2009), PIMUZ 35152: (r-t) partially exfoliated cephalon in lateral, frontal and dorsal views, (u)
detail of the right eye. (v-y) Morocops sp. A, PIMUZ 35153: (v-x) cephalon in frontal, dorsal and lateral views, (y) detail of
the left eye. Scale bars: 5 mm.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 245
Fig. 2.
eschweizerbart_xxx
246 Catherine Crônier et al.
Morocops davidbrutoni n. sp.
Fig. 3a-o
Etymology: In honour of Dr. david bruton, Professor
Emeritus and esteemed specialist on trilobites at the Natural
History Museum, Oslo, Norway.
Holotype: The complete enrolled individual PIMUZ 35159
(Fig. 3l-n).
Paratypes: Cephala PIMUZ 35154 to 35157.
Type locality and horizon: Hamar Laghdad (Anti-Atlas,
south-eastern Morocco); latest Emsian (Early Devonian).
Material: Four enrolled exoskeletons, six cephalothoraces,
59 cephala.
Diagnosis: Cephalon narrow; glabella with a wide base
and a frontal outline slightly pointed anteriorly; S2 and S3
often distinct; L1 moderately swollen with tubercles; visual
complex with 14-15 vertical lens files and maximum three to
four lenses per file; inter-lensar sclera only widened dorsally;
palpebral furrow distinct; postocular pad poorly inflated with
granules concentrated distally. Pygidial axis rather long and
wide, with rather incomplete terminal closure, and composed
of 6 clear rings plus terminal piece; pygidial pleural field
with four well-defined ribs. Dense coarse conical tubercles
on cephalon with superimposed granules.
Description: Cephalon: Length/ width ratio about 0.65.
Dorsal view: Glabellar ratio of width at L1/ maximum width
of frontal lobe about 0.51. Glabella more or less inflated,
bounded by deep axial furrows that are divergent forward
(60°). Frontal outline more or less pointed anteriorly. Frontal
lobe slightly overhanging a deep preglabellar furrow. S2 and
S3 often distinct. S1 continuous and curved more strongly
forwards than S0 in its adaxial curvature, and becoming
deeper in its distal portions. L1 shorter (sag.) than L0 (half
length of L0) and with a wide (tr.) median portion relative
to its total width. Median portion of L1 moderately inflated,
with tubercles. L1 with subcircular, moderately inflated
lateral lobes separated from its median part by a distinct
exsagittal furrow. S0 well-marked and almost transverse
in its middle portion. L0 rather wide (tr.) with lateral lobes
poorly defined. Reniform visual surface with 14-15 dorso-
ventral files of lenses and a maximum of 3-4 lenses per file,
with smaller lenses in the anterior median part. Inter-lensar
sclera widened only dorsally and barely thickened dorsally.
Palpebral furrow distinct. A row of heterogeneous tubercles
present at the base of the visual surface. Exsagittal length
of the postocular genal field longer than half length (exsag.)
of the posterior border. Postocular pad poorly inflated with
granules concentrated distally. Cheek swollen.
Lateral view: Glabella rounded anteriorly. Outline of L1
curved. L0 as high as the glabella at its maximum convexity.
Anterior border short, ridge-like, slightly projecting forwards
and sloping posteroventrally. A marginulation extending
from the antero-lateral border up to about the posterior
end of the eye. Posterior border furrow deep and narrow.
Lateral border furrow moderately deep, narrow and deeper
behind the posterior branch of the facial suture and wider
and shallower at the front of the eye. Posterolateral border
furrow continuous and posterolateral border widening at the
genal angle.
Frontal view: Glabellar outline subcircular with lateral
sides slightly flattened obliquely. Palpebral area higher than
palpebral lobe.
Ventral view: Vincular furrow deep, wide (sag.), curved
and parallel to the preglabellar furrow. Posterior band of
the cephalic doublure long (sag.), with a hypostomal suture
convex backwards medially.
Thorax: The pleural segments are narrower (tr.) posteriorly.
Maximum axial width (tr.) ratio of the last ring/ first ring
about 65%. Axial rings slightly convex with poorly defined
lateral lobes. Axial furrows distinct. Anterior pleural band
narrower (exsag.) than the posterior pleural band. Pleural
furrows deep.
Pygidium: Moderately long with a length/ width ratio about
46% (excluding the half ring), and its maximum width (tr.)
behind its midlength (sag.) in dorsal view. Posterior outline
roughly transverse medially. Pygidial axis rather long, wide,
tapered, with rather incomplete terminal closure (i.e., degree
of closure of axial furrows behind terminus of pygidial axis).
Up to six rings plus the terminal piece compose the pygidial
axis. Pygidial pleural field with four distinct ribs delimited
by deep pleural furrows. Interpleural furrows hardly distinct.
Pseudo-articulating half rings indicated by embayment in the
posterior edge of first rings.
Sculpture: Cephalon covered with dense, coarse conical
Fig. 3. Trilobites from the late Emsian ‘Red Cliff’ at Hamar Laghdad, Tafilalt, Morocco. (a-b) Morocops davidbrutoni n.
sp., PIMUZ 35154: cephalothorax in dorsal and ventral views. (c-e, o) Morocops davidbrutoni n. sp., PIMUZ 35155: (c-e)
cephalon in frontal, dorsal and lateral views, (o) detail of the right eye. (f-h) Morocops davidbrutoni n. sp., PIMUZ 35156:
cephalon in frontal, dorsal and lateral views. (i-k) Morocops davidbrutoni n. sp., PIMUZ 35157: cephalon in frontal, lateral,
and dorsal views. (l-n) Morocops davidbrutoni n. sp., Holotype PIMUZ 35159: complete enrolled exoskeleton, partially
exfoliated, in dorsal, ventral and lateral views. (p) Psychopyge cf. elegans t
erMier
& t
erMier
, 1950, PIMUZ 35158: pygidium
in dorsal view. (q-s) Destombesina cf. tafilaltensis MorzadeC, 2001, PIMUZ 35160: partially exfoliated cephalon in frontal,
dorsal and lateral view. (t) Destombesina cf. tafilaltensis MorzadeC, 2001, PIMUZ 35161: thorax + anterior of pygidium in
dorsal view. (u) Comura? sp., PIMUZ 35162: pygidium in dorsal view. (v) Hollardops cf. mesocristata (le Mtre, 1952),
PIMUZ 35163: pygidium in dorsal view. (w-z) Hollardops cf. mesocristata (l
e
M
aître
, 1952), PIMUZ 35164: cephalothorax
+ anterior of pygidium in lateral, ventral, frontal and dorsal view. Scale bars: 5 mm.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 247
Fig. 3.
eschweizerbart_xxx
248 Catherine Crônier et al.
tubercles of rather heterogeneous size with superimposed
granules. Anterior band of the cephalic doublure with short
ridges and pits, posterior band showing granules medially,
grading laterally into scaly granules. Small tubercles and
superimposed granules developed on the axial rings, the
pleural ribs and the lateral border of thoracic segments, on
the pleural ribs, the border and the pygidial axis.
Remarks: The attribution of some variants is sometimes not
clear due to the varying quality of preservation. A continuum
appears to exist between individuals with a more inflated
glabella (i.e., PIMUZ 35154) to a less inflated glabella (i.e.,
PIMUZ 35155), between individuals with high conical
tubercles (i.e., PIMUZ 35155) to low conical tubercles (i.e.,
PIMUZ 35156). The cephalic size and the dorso-ventral file
distribution are discussed in the next section on inter- and
intra-specific variablity.
The specimens with a size range from 2.5 to 8.2 mm
long (sag.) show some morphological features of Morocops
chattertoni (kHaldi et al., 2016) from the late Emsian
of Algeria such as an eye with 15 dorso-ventral files and
a maximum of three (commonly) lenses per file, and a
poorly pronounced subocular pad. However, our Moroccan
specimens show less coarse tubercles on the glabella (with
superimposed granules), less well-defined S2 and S3, and
a pygidial axis with six clear rings plus a terminal piece
against seven in Morocops chattertoni.
Morocops davidbrutoni shows also some morphological
features of Morocops forteyi (MCkellar & CHatterton,
2009) from the late Emsian of Talawarite (Tafilalt, Morocco)
such as coarse conical tubercles with a dense distribution and
an eye with a maximum of (commonly) three lenses per file.
However, our specimens from Hamar Laghdad show only
14-15 dorso-ventral files compared to 18 files in Morocops
forteyi. Moreover, the subocular pad is poorly pronounced
in Morocops davidbrutoni and more distinct in M. forteyi.
The eye is less reniform in outline, without an extremely
pronounced sclera in Morocops davidbrutoni.
Morocops davidbrutoni differs from Morocops
torkozensis (sCHraut, 2000) from late Emsian strata of
Torkoz (Morocco) in having only 14-15 dorso-ventral files
of lenses against 18 files for M. torkozensis.
M. davidbrutoni shares an eye with 14-15 dorso-ventral
files of lenses with Phacops (Phacops) vogeli s
CHraut
, 2000,
which also occurs in the late Emsian of Torkoz (Morocco),
but it differs in having only maximum 3-4 lenses per file
against 5-6 files for Phacops (P.) vogeli.
M. davidbrutoni differs from M. ovatus (M
C
k
ellar
&
CHatterton, 2009) from the late Emsian (possibly early
Eifelian) of Alnif (Morocco) in having a reduced and non
tubercular subocular pad, a visual surface with 14-15 dorso-
ventral files (maximum 3-4 lenses per file) against 19 files
(maximum 5-6 lenses per file) in M. ovatus.
M. davidbrutoni shares a reduced and non tubercular
subocular pad with M. granulops. Nevertheless, M.
davidbrutoni differs from M. granulops in having a visual
surface that is less reniform in outline, palpebral lobes less
turned inward, 14-15 dorso-ventral files (maximum 3-4
lenses per file) against 19 files (maximum 4-5 lenses per
file) for M. granulops.
M. davidbrutoni differs from Phacops (Phacops)
tafilaltanus in having only 14-15 dorso-ventral files of lenses
(maximum 3-4 lenses per file) against 18 files (maximum 5
lenses per file) for Phacops (Phacops) tafilaltanus.
Occurrence: Late Emsian; south-eastern Morocco (Hamar
Laghdad).
Superfamily Acastacea delo, 1935
Family Acastidae delo, 1935
Subfamily Asteropyginae delo, 1935
Genus Psychopyge terMier & terMier, 1950
Type species: Psychopyge elegans terMier & terMier,
1950, late Emsian, Morocco.
Additional species: Psychopyge angeles basse & Müller,
2016, late Emsian, Morocco; P. hammerorum C
Hatterton
et al., 2006, late Emsian, Morocco; P. praestans MorzadeC,
2001, late Emsian, Morocco; P. psyche basse, 2003, late
Emsian, Germany; P. termierorum MorzadeC, 2001, late
Emsian, Morocco.
Psychopyge cf. elegans terMier & terMier, 1950
Fig. 3p
cf. 1950 Psychopyge elegans terMier & terMier, p. 51, pl.
22, fig.2.
cf. 1959 Psychopyge elegans. – s
truve
in M
oore
, p. 483,
text-fig. 379.6.
cf. 1974 Psychopyge elegans. – Hollard, p. 14.
cf. 1988 Psychopyge elegans. – MorzadeC, pl. 1, figs. 1-5, pl.
2, figs. 1-7.
cf. 1982 Psychopyge elegans. – alberti, p. 178.
cf. 1998 Psychopyge elegans. – sCHraut, pl. 1, figs. 5, 6.
cf. 1999 Psychopyge elegans. – PlodoWski et al., p.49.
cf. 2001 Psychopyge elegans. – MorzadeC, p. 75, pl. 13, figs.
2-4.
cf. 2006 Psychopyge elegans. – CHatterton et al., p. 30, pl.
22, fig. 5.
cf. 2014 Psychopyge elegans. – biGnon & Crônier, p. 660.
cf. 2018 Psychopyge elegans. – beCker et al., p. 193.
Type material: A deformed and incomplete pygidium (coll.
roCH), probably lost, but not its plaster cast E-Kql-Di967
(MNHN, Paris), from the late Emsian, Jbel Issoumour,
Morocco.
Material: One fragmented and poorly preserved pygidium
(PIMUZ 35158).
Diagnosis: See MorzadeC (1988).
Remarks: MorzadeC (1988, p. 156-157; 2001, p. 75) provided
a description of the species from Bou Dîb (Maïder). The
assignment of the single pygidium to Psychopyge t
erMier
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 249
& t
erMier
, 1950 is beyond any doubt. This pygidium is close
to Psychopyge elegans t
erMier
& t
erMier
, 1950. It has only
eleven preserved pygidial axial rings with median broken
spines, only three preserved pleural segments with length (tr.)
increasing posteriorly, rounded pleural bands, interpleural
furrow distinct and widening laterally; lateral pygidial spines
are broken.
Occurrence: Late Emsian; Morocco (Maïder, Dra valley,
Tafilalt).
Genus Destombesina MorzadeC, 1997
Type species: Destombesina ougartensis MorzadeC, 1997,
late Emsian, Algeria.
Additional species: Destombesina schumacherorum b
asse
& Müller, 2016, late Emsian, Germany; D. tafilaltensis
MorzadeC, 2001, late Emsian, Morocco.
Destombesina cf. tafilaltensis MorzadeC, 2001
Fig. 3q-t
cf. 1999 Destombesina ougartensis. – PlodoWski et al.,
p.48.
cf. 2001 Destombesina tafilaltensis MorzadeC, p. 69, pl. 6,
figs. 5-7, pl. 7, figs 1-11.
cf. 2014 Destombesina tafilaltensis. – biGnon & Crônier,
p. 644.
cf. 2018 Destombesina tafilaltensis. – b
eCker
et al., p. 193.
Type material: Enrolled exoskeleton (coll. M
orzadeC
), from
the latest Emsian, Bou Tchrafine, Morocco.
Material: Two fragmented cephalo-thoraxes (plus a small
anterolateral part of a pygidium) and one cephalon (PIMUZ
35160, 35161).
Diagnosis: See MorzadeC (2001).
Remarks: M
orzadeC
(2001, p. 70) provided a description of
the species from Bou Tchrafine (Tafilalt). The assignment
of cephala (plus a small anterolateral part of a pygidium)
to Destombesina MorzadeC, 1997 is beyond doubt. These
sclerites are close to D. tafilaltensis M
orzadeC
, 2001 sharing
the anteriormost portion of the palpebral lobe posterior to
intersection of S3 and axial furrow, 19 dorsoventral files
of lenses with 4 lenses per dorsoventral file, a rather large
lateral border, and a pygidium with well-marked pleural
bands and furrows. The figured specimen has 18 files with
52 lenses in its left eye and 19 files with 53 lenses in its right
eye. Unfortunately, the genal and pygidial spines are broken.
This species is encountered commonly in the late Emsian of
the Tafilalt and Maïder (Morocco).
Occurrence: Late Emsian; Morocco (Tafilalt).
Genus Hollardops MorzadeC, 1997
Type species: Asteropyge mesocristata le Maîtr e, 1952,
late Emsian, Algeria.
Additional species: Hollardops aithassainorum CHatterton
et al., 2006, Eifelian, Morocco; H. boudibensis MorzadeC,
2001, late Emsian, Morocco; H. burtandmimiae (l
ieberMan
& kloC, 1997), late Emsian and Eifelian, Morocco; H.
lemaitreae M
orzadeC
, 1997, late Emsian, Algeria; H. struvei
(M
orzadeC
, 1969), late Emsian, France (Armorican Massif).
Hollardops cf. mesocristata (le Maître, 1952)
Fig. 3v-z
cf. v. *1952 Asteropyge mesocristata le Maître, p. 153, pl.
20, figs. 24-26.
cf. 1952 Asteropyge gr. michelini. – le Maître, pl. 21,
fig. 12.
cf. 1952 Asteropyge pectinata. – le Maître, pl. 21, fig.
13.
cf. 1967 Asteropyge mesocristata. – le Maître in le-
Grand, p. 274.
cf. 1997 Hollardops mesocristata. – MorzadeC, p. 149,
pl. 2, fig. 8, pl. 5, fig. 9, pl. 6, figs. 1, 3-6, pl. 7,
figs. 1-7, pl. 8, figs. 5-8.
cf. 1997 Philipsmithiana hyfinkeli. – lieberMan & kloC,
p.65, text-figs. 6.1-6.5, 7.7, 7.9,21.2, 21.5-9, 22.1-
2, 22.5-6, 22.8-9, 22.11.
cf. 2001 Hollardops mesocristata. – MorzadeC, p. 71, pl.
8, figs. 3, 6, 9, pl. 9, figs. 1-4.
cf. 2004 Hollardops mesocristata. – Jansen et al., pl. 2,
figs. 1, 4.
cf. 2006 Hollardops mesocristata. – CHatterton et al.,
p. 26, pl. 14, figs. 1-6, pl. 15, figs. 1-7, pl. 16, figs.
1-6, pl. 20, figs. 8, 12, 15.
cf. 2014 Hollardops mesocristata. – b
iGnon
& C
rônier
,
p. 20.
cf. 2016 Hollardops mesocristata. – kHaldi et al., p. 360,
372, 384, text-figfig. 6m-p.
Type material: A small enrolled exoskeleton GFCL401
(coll. l
e
M
aître
, Faculté libre des Sciences de Lille), late
Emsian, Erg el Djemel.
Material: One fragmented pygidium and one enrolled
cephalo-thorax (plus a small anterolateral part of pygidium)
(PIMUZ 35163, 35164).
Diagnosis: See CHatterton et al. (2006).
Remarks: le Maître (1952, p. 153) and MorzadeC (19 97, p.
149) provided a full description of the type material from the
Erg el Djemel section. Additionally, C
Hatterton
et al. (2006)
provided numerous illustrations of this species from the
best specimens available from Morocco. The assignment of
cephalothorax (plus a small anterolateral part of pygidium)
and the isolated pygidium to Hollardops is beyond doubt.
The enrolled specimen is close to Hollardops mesocristata
eschweizerbart_xxx
250 Catherine Crônier et al.
(l
e
M
aître
, 1952) sharing a rounded frontal lobe, curved
axial furrows between S2 and S3, L2 and L3 more elevated
than L1, 29 dorsoventral files of lenses with 8 lenses per
dorsoventral file (right eye), an anterior tip of palpebral lobes
posterior to intersection of axial furrows and S3, a thorax
with 10 segments, probably 5 pleural segments with very
wide pleural furrows. Unfortunately, the genal and pygidial
spines are broken. This species is encountered commonly in
the late Emsian from North Africa.
Occurrence: Late Emsian; Algeria (Saoura: Erg el Djemel),
Morocco (Dra Valley: Foum Zguid; Tafilalt: Hamar
Laghdad, Bou Tchrafine; Maïder: Jbel Issoumour, Oufatène,
Mrakib).
Genus Comura riCHter & riCHter, 1926
Type species: Cryphaeus cometa riCHter, 1909, Emsian,
Germany.
Additional species: Comura bultyncki MorzadeC, 2001, late
Emsian, Morocco (Ma’der); C. defensor (r
iCHter
& r
iCHter
,
1952), late Emsian, Germany, France, Spain; C. echinata
M
orzadeC
, 1983, late Emsian, France (Armorican massif);
C. joaquini (r
iCHter
& r
iCHter
, 1952), C. philonyx (r
iCHter
& r
iCHter
, 1952), late Emsian, Germany; C.? tuberculata
MorzadeC, 1969, late Emsian, France; C.? kervezensis
M
orzadeC
, 1983, late Emsian, France (Armorican massif);
C.? eos Haas, 1970; C.? inermis Haas, 1970.
Comura? sp.
Fig. 3u
Material: One poorly preserved pygidium (PIMUZ 35162).
Remarks: This Moroccan specimen appears to show a
development of pygidial spines from anterior pleural bands,
wide pleural furrows, and minimum nine pygidial axial
rings. The assignment of this poorly preserved pygidium to
Comura remains doubtful.
Order Proetida Fortey & oWens, 1975
Family Aulacopleuridae anGelin, 1854
Subfamily Otarioninae riCHter & riCHter, 1926
Genus Cyphaspis burMeister, 1843
Type species: Phacops ceratophthalmus G
oldFuss
, 1843,
Eifelian, Gerolstein in Germany.
Remarks: adrain & CHatterton (1996) provided an
emended diagnosis and integrated 20 species in this genus.
Four new species from Morocco were added by CHatterton
et al. (2006) including three from the late Emsian: Cyphaspis
agayuara, C. eberhardiei, and C. hamidi. Subsequently,
van viersen & PresCHer (2014) provided a revised generic
diagnosis and van viersen & Holland (2016) recorded
numerous new species from the Pragian to Givetian from
Moroccan localities and studied their morphological trends.
Occurrence: Wenlock to Givetian; France, England, Czech
Republic, Germany, Austria, Poland, Morocco, NW Canada,
Australia.
Cyphaspis sp. A
Fig. 4a-f, g
Material: Three fragmented cranidia plus probably one
exfoliated cranidium (PIMUZ 35165 to 35167).
Remarks: These Moroccan specimen shows quite dense
medium-sized tubercles (to smaller-sized for lateral
preoccipital lobes) evenly distributed over glabella and
lateral preoccipital lobes. The state of preservation and the
absence of complete individuals prevent us from any specific
attribution. The exfoliated specimen illustrated figure 4g
may be tentatively assigned to Cyphaspis sp. A in having
more scattered tubercles.
Cyphaspis sp. B cf. boutcharafinense (alberti, 1981)
Fig. 4h-i
cf. 1969 Otarion (Otarion) sp. D. – alberti, p.681, pl. 34,
fig. 7.
cf. 1981 Otarion (Otarion) sp. aff. boutcharafinense. – al-
berti, p. 42, pl. 5, fig. 54.
Fig. 4. Trilobites from the late Emsian ‘Red Cliff’ at Hamar Laghdad, Tafilalt, Morocco. (a-c) Cyphaspis sp. A, PIMUZ 35165:
partially exfoliated cranidium in frontal, dorsal and lateral views. (d-f) Cyphaspis sp. A, PIMUZ 35166: partial cranidium
in lateral, frontal, and dorsal, views. (g) Cyphaspis sp. A, PIMUZ 35167: cranidium in dorsal view. (h-i) Cyphaspis sp. B cf.
boutcharafinense (Alberti, 1981), PIMUZ 35168: glabella in lateral and frontal views. (j-l) undetermined proetid, PIMUZ
35169: pygidium in dorsal, lateral, and frontal views. (m-o) Cyphaspides sp., PIMUZ 35170: partially exfoliated cephalon
in dorsal, frontal and lateral views. (p) Cyphaspides sp., PIMUZ 35171: cephalon in frontal view. (q-s) Ceratocephala cf.
vesiculosa (beyriCH, 1846), PIMUZ 35172: exfoliated cephalon in frontal, dorsal and lateral views. (t-v) Ceratocephala cf.
vesiculosa (b
eyriCH
, 1846), PIMUZ 35173: exfoliated cephalon in frontal, dorsal and lateral views. (w) Leonaspis ? sp.,
PIMUZ 35174: pygidium in dorsal view. (x) Acanthopyge sp., PIMUZ 35175: cranidium in posterior view. (y-ab) Acanthopyge
sp., PIMUZ 35176: cranidium in frontal, dorsal, posterior, and lateral views. Scale bars: 5 mm.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 2 51
Fig. 4.
eschweizerbart_xxx
252 Catherine Crônier et al.
Material: One fragmented cranidium (showing glabella and
lateral preoccipital lobes only) (PIMUZ 35168).
Remarks: This specimen shows coarse subequally sized
tubercles evenly distributed over glabella and lateral
preoccipital lobes such as in Cyphaspis agayuara from the
late Emsian of Jbel Gara el Zguilma (southern Morocco). The
state of preservation and the absence of complete individuals
prevent us from any specific attribution. This specimen can
be tentatively assigned to Cyphaspis cf. boutscharafinense
(Alberti, 1981) according to its coarse and slightly finer
glabellar tubercles. Cyphaspis sp. B differs from Cyphaspis
sp. A in having coarser tubercles and more inflated lateral
preoccipital lobes.
Subfamily Cyphaspidinae přibyl, 1947
Genus Cyphaspides novák, 1890
Type species: Cyphaspides scuticauda n
ovák
, 1890, late
Emsian/ Eifelian, Greifenstein in Germany.
Remarks: t
HoMas
& o
Wens
(1978) provided a review of the
Aulacopleuridae comprising the distinct genus Cyphaspides
characterized by a forward-expanding clavate glabella,
a small and inconspicuous L1, 11-12 thoracic segments,
no thoracic axial spine, a pygidium with posterior pleural
bands elevated above the anterior, and a cephalic and
pygidial crenulate margins. Recently, basse & Müller
(2016) described the two additional species C. malbertii
and C. weugi from the Eifelian of Germany and provided a
comparison with all other species of this genus.
Cyphaspides sp.
Fig. 4m-p
Material: Five more or less eroded cephala (PIMUZ 35170,
35171).
Remarks: These cephala may be assigned to a cyphaspidine
specimen (Cyphaspides) but their fragmentation prevents an
accurate assignment.
Description: Cephalon semicircular, surrounded by a
distinct, convex and crenulate border. Lateral border with
broken, probably strong spines. Glabella subquadrate,
strongly swollen, frontally vaulted above sloping preglabellar
field, and narrow (tr.); small drop-like, lateral basal lobes.
Preglabellar field apparently narrow (sag.) but this anterior
part is damaged. Lateral border furrows rather shallow and
broad. Posterior border furrows rather deep and narrow.
Occipital ring damaged but apparently convex and narrow
(sag.). Genae strongly vaulted, sloping laterally. Genal
angle with a short genal spine. Eyes and eye-platform not
preserved. Rather small and dense tubercles with few more
prominent tubercles on glabella and genae.
Family Proetidae salter, 1864
Genus Gerastos GoldFuss, 1843
Type species: Proetus cuvieri steininGer, 1831, Eifelian,
Gees, Germany.
Additional species from North Africa only (following
Gibb & CHatterton 2010), Gerastos ainrasifus Gibb &
CHatterton, 2010, Eifelian, southern Morocco (Maider);
G. aintawilus Gibb & CHattert on, 2010, Eifelian,
southern Morocco (Maider); G. akrechanus albert i,
1969, Emsian, northwestern Morocco; G. cuvieri malisus
Gibb & CH atterton, 2010, Eifelian, southern Morocco
(Maider); G. discombobulates G
ibb
& C
Hatterton
, 2010,
Eifelian, southern Morocco (Maider); G. emmetus Gibb &
C
Hatterton
, 2010, Givetian, southern Morocco (Maider); G.
hammii Gibb & CHatterton, 2010, late Emsian or Eifelian,
southern Morocco (Maider); G. izius G
ibb
& C
Hatterton
,
2010, Givetian, southern Morocco (Maider); G. lisanrasus
Gibb & CH atterton, 2010, Eifelian, southern Morocco
(Maider); G. malisjildus G
ibb
& C
Hatterton
, 2010, Eifelian,
southern Morocco (Maider); G. prox umerbianus a
lberti
,
1969, Eifelian or Givetian, Morocco; G. raribus Gibb &
C
Hatterton
, 2010, Givetian, southern Morocco (Maider);
G. rehamnanus alberti, 1969, probably Early Devonian,
Morocco; G. taqus Gibb & CHatterton, 2010, Eifelian,
southern Morocco (Maider); G. tuberculatus marocensis
CHatterton et al., 2006, late Emsian–Eifelian, Morocco
(Tindouf, Tafilalt, Maider), Algeria (Saoura Valley).
Remarks: On the basis of well-preserved material, Gibb &
CHatterton (2010) described and illustrated twelve species
and subspecies of Gerastos from the Early to the Middle
Devonian of Morocco. The validity of the diagnostic features
remains open to debate. The diagnostic features between
Gerastos, Longiproetus and Coniproetus were previously
discussed by oWens (1973) and completed and modified by
lütke (1990), adrain (1997) and CHatterton et al. 2006.
v
an
v
iersen
& P
resCHer
(2008) commented on Gerastos
and Rhenocynproetus b
asse
, 2002 and they find both genera
to be remarkably similar and they place them in synonymy
due to variable and intermediate morphological characters.
The problem with recognising one such group was also
addressed by van viersen & PresCHer (2010) and they
raised the question as to where to set the boundaries for some
intermediate taxa between Gerastos and Rhenocynproetus.
If Gibb & CHatterton (2010) revised the diagnosis for
Gerastos, according to van viersen et al. (2012), none of
the characters or their combination appears to be restricted
to the genus Gerastos. The distinct diagnoses provided
by Gibb & CHatterton (2010) and basse (2010) comprise
common characters (such as a strongly vaulted, usually
tubercular glabella, short or (usually) absent preglabellar
field, and a comparatively small pygidium) rather widespread
in numerous Early Devonian proetine genera. Recently,
basse & Müller (2016) commented again on Gerastos and
Rhenocynproetus and they find both genera to be similar
but with distinctive diagnostic characters and restored the
respective generic status.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 253
Gerastos sp. A vel Rhenocynproetus sp. A
Fig. 5al-an
Material: Seven more or less eroded cranidia (PIMUZ
35191).
Description: Anterior border of cranidium not dorsally
flattened medially and protruding from cephalic outline.
Cephalic border upward curved adaxially in anterior view,
faintly downward curved in lateral view. No terrace ridges
visible dorsally on anterior border, only in frontal view.
Glabella strongly inflated. Outline of glabella anterior to
S0 rounded ‘subquadratical’, parabolic between anterior
margin and toward S0. Glabellar sagittal length anterior
to S0 relative to glabellar maximum width around 1.04.
Axial furrow rather deep and uniformly narrow. S0 hardly
W-shaped, indenting somewhat posteromedial margin
of glabella anterior to S0. Occipital ring width relative to
maximum glabellar around 0.85. Occipital ring with small
granules. Lateral occipital lobes hardly isolated. Glabella
anterior to S0 bears numerous, heterogeneous granules,
denser posteriorly than anteriorly, and showing pits. S1 and
S2 very weakly impressed, indicated by no ornamentation.
S1 curving inward and downward and narrowing gradually.
S3 indiscernible. Preocular sutures slightly divergent and
curved between α and γ. Postocular sutures converging
slightly posteriorly from ε, and then strongly diverging
towards ω. Surface of fixigena with small scattered granules.
Posterior border subtransversally to slightly posterolaterally,
with few granules.
Remarks: Owing to the absence of complete specimens,
the assignment to Gerastos remains somewhat questionable,
although it is probable. These cranidia could be tentatively
assigned to G. akrechanus alberti, 1969, from the Emsian
of northwestern Morocco owing to its relative proportions
and ornamentation of its glabella. Nevertheless, S1 and
S2 are better-impressed and ornamentation is denser in G.
akrechanus.
Gerastos sp. B vel Rhenocynproetus sp. B
Fig. 5ad-ak
Material: Fourteen more or less eroded cranidia, two free
cheeks and two poorly preserved cephala (PIMUZ 35188
to 35190).
Description: Anterior border of cranidium not dorsally
flattened medially, and protruding somewhat from the
cephalic outline. Cephalic border curved upward adaxially
in anterior view, faintly downward in lateral view. No
terrace ridges visible dorsally on anterior border, only in
frontal view. Glabella inflated. Outline of glabella anterior
to S0 rounded ‘subrectangular’, broadly parabolic between
anterior margin and toward S0. Glabellar sagittal length
anterior to S0 relative to glabellar maximum width around
1.12. Axial furrow rather deep and uniformly narrow. S0
hardly w-shaped, indenting somewhat posteromedial margin
of glabella anterior to S0. Occipital ring width relative to
maximum glabellar width around 0.88. Occipital ring with
small granules. Lateral occipital lobes hardly isolated.
Glabella anterior to S0 bears numerous, heterogeneous
granules, denser posteriorly than anteriorly. S1 and S2
very weakly impressed, indicated by no ornamentation. S1
curving inward and downward and narrowing gradually. S3
indiscernible. Palpebral lobes with apparently few small pits
and numerous granules. A row of few granules at the base
of the eye. Margin of eye socle furrow well-incised, more
widened anteriorly than posteriorly. Genal field ornamented
with granules. Three distinct terrace ridges on the lateral
border of free cheeks. Genal angle acuminated. Preocular
sutures slightly divergent and curved between α and γ.
Postocular sutures converging slightly posteriorly from ε.
Surface of fixigena with numerous granules. Posterior border
with few granules.
Remarks: Owing to the absence of complete specimens,
the assignment to Gerastos is uncertain, although it is
probable. These cranidia and cephala could be tentatively
assigned to G. rehammanus albe rti, 1969 from the
Early Devonian of western Morocco owing to its relative
proportions and ornamentation of its glabella. Gerastos
sp. B vel Rhenocynproetus sp. B differs from Gerastos sp.
A vel Rhenocynproetus sp. A by having a less anteriorly
protruding and less inflated glabella.
Gerastos? sp. C
Fig. 5i-k, x-z
Material: Three pygidia (PIMUZ 35183, 35184).
Description: Pygidium rather vaulted (sag., tr.). Sagittal
length (excluding half ring) of pygidium about 0.68 relative
to maximum width. Length (sag.) of axis about 0.82 relative
to sagittal length of pygidium. Maximum width of axis about
0.90 relative to sagittal length of axis and 0.45 relative to
maximum width of pygidium. Posterior margin running
subtransversely medially. Pygidial border gently downward
sloped. Border furrow shallow separating pleural field
from pygidial border. Few distinct terrace ridges present
anterolaterally to posterolaterally on pygidial border;
posteromedially two additional ones developed. Axis
moderately inflated and tapered proportionally backwards.
Axial furrows firmly impressed. Six axial rings plus terminal
axial piece present. Axial rings broadly m-shaped. Inter-
ring furrows rather shallow. Pleural fields with four pairs
of posterolaterally curved pleurae; a fifth, rudimentary pair
may be developed. Pleural furrows more deeply incised than
interpleural furrows. Pygidium covered with few, randomly
scattered granules.
Remarks: These isolated proetid pygidia may be tentatively
assigned to some isolated proetid cranidia, i.e., Gerastos
sp. B vel Rhenocynproetus sp. B or Gerastos sp. A vel
Rhenocynproetus sp. A, which were identified based on
materials from the same outcrop.
eschweizerbart_xxx
254 Catherine Crônier et al.
Genus Orbitoproetus Pillet, 1969
Type species: Trilobites orbitatus barr ande, 1846, late
Emsian, Czech Republic.
Orbitoproetus? sp.
Fig. 5s-u
Material: Only three fragmented cranidia (PIMUZ 35185
to 35187).
Description: Anterior border of cranidium slightly dorsally
flattened medially and protruding from cephalic outline.
No terrace ridges visible on anterior border but apparently
some fine pits. Outline of glabella anterior to S0 rounded
‘subquadratical’/ ’subovoid’, parabolic between anterior
margin and toward S0. Glabellar sagittal length anterior to
S0 relative to glabellar maximum width around 1.03. Axial
furrow rather deep and uniformly narrow. S0 w-shaped,
indenting posteromedial margin of glabella anterior to S0.
Occipital ring width relative to maximum glabellar around
0.97. Occipital ring as glabella with evenly scattered small
granules. Lateral occipital lobes well-isolated. Glabella
anterior to S0 bears scattered, small granules. S1 (and S2?)
weakly impressed. S1 curving inward and downward. S3
indiscernible. Preocular sutures slightly divergent between
α and γ. Postocular sutures converging slightly posteriorly
from ε, and then strongly diverging towards ω. Surface of
fixigena almost smooth, with only few randomly scattered
small granules. Posterior border subtransversally.
Remarks: Owing to the absence of complete specimens,
the assignment to Orbitoproetus is uncertain, although it
appears reasonable. Moreover, a free cheek (Fig. 5v-w) could
be tentatively assigned to these specimens. This free cheek
shows the same pattern of ornamentation (evenly scattered
small granules) and three terrace ridges on the lateral border
with fine pits. Additionally, a pygidium (Fig. 5aa-ac) could
be tentatively assigned to these specimens.
This pygidium shows: a sagittal length (excluding half
ring) of about 0.61 relative to maximum width; a length (sag.)
of the axis about 0.85 relative to sagittal length of pygidium;
a maximum width of axis about 0.97 relative to sagittal
length of axis, and 0.50 relative to maximum width of
pygidium; a subparabolic posterior margin; a border bearing
four parallel marginal terrace ridges, two visible dorsally;
a shallow and narrow border furrow; a gently downward
sloped pygidial border; steeply downwards sloped pleural
fields; a proportionally backwards axis tapered; five distinct
axial rings (one more may be present) plus terminal piece;
axial rings running rather transversally outward and then
flex posterolaterally; lateral axial lobes fused and hardly
inflated; pleural fields with four distinct pairs of smoothly
posterolaterally curved pleurae; a fifth, rudimentary pair
may be developed; anteriormost pleural furrows deep,
especially near halfway (tr.) along pleural fields; distally
distinct where first pleura continues onto lateral border;
interpleural furrows faint but continuous. This pygidium
apparently is smooth.
Our Moroccan cranidium could be related to the late
Emsian Orbitoproetus orbitatus (barrande, 1846) from
Měňany in Czech Republic (Kim 1997) but seems to differ
in having a less globular glabella outline, which is more
elongated (sag.). In the same way, this Moroccan cranidium
resembles the Emsian to Eifelian Orbitoproetus gryphus
(runzhei mer, 1935) from Greifenstein in Germany (kiM
1997) but appears to differ in having a less globular and
more protruding glabella.
Genus Cornuproetus riCHter & riCHter, 1919
Type species: Gerastos cornutus GoldFuss, 1843, Eifelian,
Eifel, Germany.
Additional species (Emsian to Eifelian in North Africa
only): Cornuproetus cornutus marrakechensis (alberti,
1969), ?Eifelian, Morocco; C. cornutus djemelensis a
lberti
,
1981a, probably late Emsian (not Eifelian), Algeria; C. pernix
boutsharafinensis (a
lberti
, 1969), late Emsian, Morocco;
?C. infans (a
lberti
, 1969), ?Middle Devonian, Morocco; ?C.
maidericus (alberti, 1969), late Emsian, Morocco.
Fig. 5. Trilobites from the late Emsian ‘Red Cliff’ at Hamar Laghdad, Tafilalt, Morocco. (a-c) Cornuproetus sp., PIMUZ
35177: cephalon in frontal, dorsal and lateral views. (d-e) Cornuproetus sp., PIMUZ 35178: pygidium in dorsal and lateral
views. (f-h) Eremiproetus cf. dufresnoyi saharae a
lberti
, 1967, PIMUZ 35181: cranidium in lateral, frontal, and dorsal
views. (i-k) Gerastos? sp. C, PIMUZ 35183: pygidium in frontal, lateral, and dorsal views. (l-o) Eremiproetus cf. dufresnoyi
saharae a
lberti
, 1967, PIMUZ 35182: cranidium in right lateral, frontal, left lateral, and dorsal views. (p-q) Cornuproetus sp.,
PIMUZ 35179: fragmented cranidium in dorsal and lateral views. (r) Cornuproetus sp., PIMUZ 35180: fragmented cranidium
in dorsal view. (s-u) Orbitoproetus? sp., PIMUZ 35185: cranidium in frontal, lateral, and dorsal views. (v-w) Orbitoproetus?
sp., PIMUZ 35186: free cheek in lateral, and dorsal views. (x-z) Gerastos? sp. C, PIMUZ 35184: pygidium in frontal, dorsal,
and lateral views. (aa-ac) Orbitoproetus? sp., PIMUZ 35187: pygidium in lateral, frontal and dorsal views. (ad-af) Gerastos
sp. B vel Rhenocynproetus sp. B, PIMUZ 35188: cranidium in frontal, dorsal, and lateral views. (ag-ai) Gerastos sp. B vel
Rhenocynproetus sp. B, PIMUZ 35189: fragmented and partially exfoliated cephalon in dorsal, frontal, and dorsal views.
(aj-ak) Gerastos sp. B vel Rhenocynproetus sp. B, PIMUZ 35190: free cheek in lateral and dorsal views. (al-an) Gerastos sp.
A vel Rhenocynproetus sp. A, PIMUZ 35191: cranidium in frontal, lateral and dorsal views. Scale bars: 5 mm.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 255
Fig. 5.
eschweizerbart_xxx
256 Catherine Crônier et al.
Remarks: alberti (1969) published the most extensive
report about the classification of this genus divided into 16
subgenera. Additionally, He described and illustrated several
new species including five from the late Emsian of Morocco
among more than 20 species illustrated mostly according
to their cranidia. Among these five new species, two were
then re-assigned to Cornuproetus (Paralepidoproetus): C.
(P.) fauremuretae and C. (P.) chouberti (see alberti 1981a).
Moreover, alberti (1981a) described and illustrated the new
subspecies C. cornutus djemelensis from probably the late
Emsian (not Eifelian) of the Erg el Djemel, Algeria. More
work is required in order to reevaluate these previously
described species.
Cornuproetus sp.
Fig. 5a-e, p-q, r
Material: Three poorly preserved cranidia, one
cephalothorax and one pygidium (PIMUZ 35177 to 35180).
Remarks: The cephalon is characterized by slightly convex
anterior and lateral cephalic borders, a ‘subquadratical’
slightly inflated glabella, no distinct anteromedian cephalic
projection, no epiborder furrow, apparently no inflated lobes
on genal field adjacent to front and back of a narrow socle,
no preglabellar field (sag.); granules equally-sized and evenly
distributed on the glabella (except in the glabellar furrows,
and slightly denser posteriorly), and on the thoracic rings;
few (three?) terrace ridges on the antero-lateral borders of
the cephalon; one median tubercle on the occipital ring; a
pygidium with at least two distinct axial rings plus a terminal
piece.
The most complete but eroded specimen shares some
morphological characters with Cornuproetus midas
amlanensis from the late Emsian of Jbel Amlane (Tafilalt)
and C. pernix boutsharafinensis (alberti, 1969) from the late
Emsian of Bou Tchrafine (Tafilalt) in having a ‘subquadrate’
slightly inflated glabella but differs in having equally-sized
granules that are evenly distributed on the glabella (coarse
and dense tubercles for C. midas amlanensis and for C.
pernix boutsharafinensis) and narrower (tr.) palpebral lobes.
This Moroccan cephalon differs from ?C. maidericus
(alberti, 1969) represented by a cranidium from the late
Emsian of Jbel Issoumour (Maider) in having no preglabellar
field (sag.) and a more inflated glabella (a very lowered
glabella for ?C. maidericus).
Genus Eremiproetus riChter & riChter, 1919
Type species: Proetus dufresnoyi hawle & Corda, 1847,
late Emsian, Suchomasty Lst, Koněprusy, Czech Republic.
Additional species (late Emsian to Eifelian in North
Africa only): Eremiproetus dufresnoyi australis a
lberti
,
1969, late early Emsian, SE Morocco; E. dufresnoyi saharae
alberti, 1967, latest Emsian, SE Morocco; E. dufresnoyi
australomaurus alberti, 1983, early Eifelian, SE Morocco;
E. frequens alberti, 1967, late early Emsian, SE Morocco.
Eremiproetus cf. dufresnoyi saharae alberti, 1967
Fig. 5f-h, l-o
cf. 1967 Eremiproetus dufresnoyi saharae alberti, p. 493,
pl. 1, fig. 14.
cf. 1969 Eremiproetus dufresnoyi saharae. – alberti, p.
269, pl. 23, fig. 10.
cf. 1983 Eremiproetus dufresnoyi saharae. – alberti, p. 32,
pl. 6, fig. 67.
cf. 2018 Eremiproetus dufresnoyi saharae. – beCker et al.,
p. 192.
Type material: A cranidium (CGMTA 181), latest Emsian,
Hamar Laghdad V.
Material: Six poorly preserved cranidia (PIMUZ 35181,
35182).
Diagnosis: See alberti (1967).
Remarks: These poorly preserved cranidia are close to
Eremiproetus dufresnoyi saharae alberti 1967 from the
latest Emsian, Hamar Laghdad V (according to b
eCker
et
al. 2018) in the general outline of their glabella, the upraised,
backward projected frontal border, the slightly swollen
lateral occipital lobes and the tiny spine on the posterior edge
of occipital ring. These cranidia show the following features:
glabella subquadrangular, with length (sag.) about 96%
width (tr.) across palpebral lobes; prominent anterior border
regularly curved, sharply delimited by a deep border furrow;
preglabellar field of constant sagittal length anteriorly;
anterior border, border furrow and frontal glabella furrow
of equal curvature; glabella furrows shallow but distinct. S1
curved, obliquely backward directed, defining unswollen
L1 lobe that does not protrude onto the occipital furrow;
occipital furrow narrow and deep; occipital lobe with a node
(or tiny spine) on its posterior edge; lateral occipital lobes
hardly defined and slightly swollen; palpebral lobe long
and very narrow; projection δ – δ (tr.) anteriorwards of S1;
projection γ – γ at S3.
These poorly preserved cranidia differ from
Eremiproetus dufresnoyi australis alberti, 1969 and from
E. frequens alberti, 1967 from the late early Emsian,
Hamar Laghdad V (according to beCker et al. 2018) by a
tinier median spine and no clear distinct median node on
the occipital lobe.
Occurrence: Late Emsian; Morocco (Tafilalt).
Order Harpetida WHittinGton, 1959
Family Harpetidae HaWle & Corda, 1847
Remarks: The Harpetida remain a group of unclear
phylogenetic origin even though e
baCH
& M
C
n
aMara
(2002)
revised ten harpetid genera using a cladistic approach. Some
harpetids are known from North Africa such as, e.g., Harpes
perradiatus r
iCHter
& r
iCHter
, 1943 from the Eifelian of
Dechra-aït-Abdallah, Central Morocco, characterized by
a conical glabella, pitting of brim arranged into irregular
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 257
radial ridges and forming a coarse polygonal network,
and small and weakly defined alae; as a second example,
Eskoharpes neogracilis (riCHter & riCHter, 1924) from
the Frasnian of Mrirt, Central Morocco, is characterized
by a gently flat and inclined brim, and small and weakly
defined alae (see MCnaMara et al. 2009). Lioharpes sp.
WHittinGton, 1950 is also encountered in the Pragian from
Ben Zireg, southwestern Algeria (a
lberti
1983, pl. 2, fig. 20)
and Morocco (Fortey 2014, fig. 6).
From the Early and/ or Middle Devonian, two genera
are known: Lioharpes W
HittinGton
, 1950 from the Early
and Middle Devonian, characterized by a flat and elongate
(sag.) brim, large alae, a wide (tr.) and vaulted sub-triangular
glabella, and a prominent genal roll; Harpes G
oldFuss
, 1839
occurs in the Middle Devonian and is characterized by a
flat and pitted brim with a wide rim that is raised along the
whole margin, a semicircular to ovate cephalon, an elongate
to sub-triangular glabella, which is inflated, tuberculate and
long (sag.), a convex and vaulted genal roll, eyes set adaxially
and anterior to preglabellar furrow, weak eye ridges, as well
as transversely elongate alae and larger than Ll.
Genus Harpes GoldFuss, 1839
Type species: Harpes macrocephalus GoldFuss, 1839,
Eifelian, Gerolstein in Germany.
Additional species from Morocco: Harpes perradiatus
riCHter & riCHter, 1943, Eifelian, Central Morocco.
Harpes hamarlaghdadensis n. sp.
Fig. 6a-n
Derivatio nominis: Named after the type locality Hamar
Laghdad.
Holotype: Cephalon PIMUZ 35192.
Paratypes: Three fragmented cephala: PIMUZ 35194,
35195, 35196; one fragmented cephalon: PIMUZ 35193; one
anterolateral part of cephalon: PIMUZ 35197.
Type locality and horizon: Hamar Laghdad, south-eastern
Morocco; late Emsian, Early Devonian.
Material: Thirteen more or less fragmented cephala.
Diagnosis: Cephalon roughly semicircular. Brim gently
inclined anteriorly and laterally, about one-third of cephalic
length. External rim rather wide. Subrectangular elongated
glabella with no tuberculation. Genal roll gently convex,
sloping steeply, and short. Alae as wide as L1. No distinct
eye ridges. No granulation or pits on genal area.
Description: Cephalon: excluding prolongations, roughly
semicircular, with length/ width ratios about 75%; vaulted.
Prolongations quite long, about 50% cephalic length
(sag.); inner margin exsagittal, outer margin directed
posteromedially; broken end. Brim flat, gently inclined
anteriorly and laterally, about one-third cephalic length
(sag.); prolongation with steeper inclination. External rim
(partially preserved) rather wide, prominently raised and
parallel to girder, with a narrow and faint furrow all around
and granulations. Genal roll gently convex, sloping steeply,
short, about 50% brim length (sag.). Girder kink (sag.) due
to an anteriorly convex deflection of girder. Anterior boss
slightly inflated and extended from the preglabellar field
onto the genal roll. Genal area inflated and convex, slightly
concave along adaxial margin. Eye lobe located on anterior
slope of genal area, about 20% glabellar length, behind
anterior margin of glabella and midway between axial
furrow and girder. Eye ridges not distinct. Glabella vaulted,
curved anteriorly, slightly less than half cephalic length
(sag.), sloping anteriorly into shallow preglabellar furrow,
with subparallel fairly deep and wide axial furrrows. L1
subtriangular; S1 distinct, effacing posteromedially. Occipital
furrow fairly shallow and quite narrow. Occipital ring about
10% cephalic length (sag.) and 22% cephalic width (tr.). Ala
small, weakly defined with faint alar furrows, continuous
with occipital furrow and L1. Posterior border furrow wide
(exsag.), somewhat deeper adaxially than distally. Row of
rather large pits beneath steeply sloping inner face of external
rim; another row of large pits demarcating inner margin of
brim; pits slightly smaller in size on brim and genal roll.
Remarks: These cephala may be assigned to a harpetid
species (Harpes) recognizable by their semicircular
cephalon, their flat and pitted brim, their wide and raised
external rim, their elongated and inflated glabella, and their
convex genal roll (according to the emended diagnosis by
ebaCh & mCnamara (2002)).
Our specimens resemble H. reticulatus HaWle &
Corda, 1847 from the late Emsian, Suchomasty Limestone,
Koněprusy, Czech Republic (barrande 1852: pl. 9, figs. 20-
22) and also described from the late Emsian/early Eifelian,
Greifenstein Limestone, Greifenstein, Germany (kiM 1997:
pl. 10, figs. 5-6), in having no granulation on the genal
area but with a less carinated and a narrower (tr.) glabella
(‘subtriangular’ in H. reticulatus and ‘subrectangular’ in H.
hamarlaghdadensis n. sp.), alae as wide (tr.) as L1 (larger
than L1 in H. reticulatus), and with no distinct eye ridges.
Due to the posteriorly rather narrow glabella, our
specimens from Hamar Laghdad resemble Lioharpes
montagnei hawle & Corda, 1847 from the Acanthopyge
Limestone (Eifelian) of Czech Republic (p
řibyl
& V
aněK
1986, text-fig. 1-5) and Lioharpes hastatus lütKe, 1965
from the late Emsian of Germany (lütKe 1965, pl. 20, figs.
7-12). They share also a semicircular cephalon outline, a
long brim (sag.), strongly tapering prolongations, and an
anterior boss but this anterior boss is slightly inflated and
extended from the preglabellar field onto the genal roll in our
moroccan specimens and this anterior boss is more bulbous
in Lioharpes species. In contrast to these Lioharpes species,
Harpes hamarlaghdadensis n. sp. has a more elongated (sag.)
glabella that is larger than L1 (not in Lioharpes), a longer
(sag.) L0, and no sagittal crest on occipital ring (present in
Lioharpes).
Our specimens from Hamar Laghdad differ from
Harpes perradiatus riCHter & riCHter, 1943 from the
eschweizerbart_xxx
258 Catherine Crônier et al.
Eifelian of Central Morocco in its glabella shape (conical
in Harpes perradiatus and ‘subrectangular’ in Harpes
hamarlaghdadensis n. sp.).
Our specimens look like Harpes sp. L basse & Müller,
2016 from the late Emsian/ early Eifelian of the Rhenish
Massif but the deformed German specimens prevent an
accurate comparison with Moroccan specimens. Unlike the
German specimens, the genal area of our specimens shows
no granulation.
However, a question remains about the attribution of
a fragmentary cephalon (fig. 6 n) that presents a hardly
vaulted brim with a finer perforation unlike the other
described Moroccan specimens. This would characterise
Kielania convexa hawle & Corda, 1847 encountered in the
late Emsian of Czech Republic (V
aněK
& V
alíčeK
2002).
This latter species is a close relative to Harpes reticulatus.
Kielania convexa differs from Harpes reticulatus by its
more forward inclined, narrower and slightly convex brim
and its finer perforation of the brim and cheek-roll. Only
more material could confirm this assignation.
Order Lichida Moore, 1959
Family Odontopleuridae burMeister, 1843
Genus Ceratocephala Warder, 1838
Type species: Ceratocephala goniata Warder, 1838,
Silurian, Springfield, Ohio.
Additional species from Morocco: Ceratocephala
vesiculosa (beyriCH, 1846), early Eifelian, Rabat, Morocco;
Ceratocephala cf. vesiculosa (beyriCH, 1846), late Emsian,
Hamar Laghdad, Morocco.
Remarks: raMsköld (1991a, b) and raMsköld &
CHatterton (1991) gave a review of the classification of
the Odontopleuridae and showed that Ceratocephala and
Ceratocara constitute unambiguous sister taxa assigned
to the subfamily Ceratocephalinae riCHt er & riCHter,
1925. Additionally, a phylogenetic analysis performed by
C
Hatterton
et al. (1997) supports the monophyly of both
Ceratocephala and Ceratocara. Ceratocephala is long
ranging from the Middle Ordovician to the Middle Devonian
and is widely distributed geographically.
Ceratocephala cf. vesiculosa (beyriCH, 1846)
Fig. 4q-v
cf. 1846 Odontopleura vesiculosa beyriCH, p. 22, pl. 3, fig.
7.
cf. 1968 Ceratocephala vesiculosa. – bruton, p. 46, pl. 8,
figs. 1-4, 13, 14. (for synonymies between 1846 and
1968)
cf. 1969 Ceratocephala (Ceratocephala) vesiculosa. – a
l
-
berti, p. 431.
cf. 1969 Ceratocephala (Ceratocephala) sp. ex. gr. vesicu-
losa. – alberti, p. 489, 459, 501.
cf. 1970 Ceratocephala vesiculosa. – alberti, p. 134, pl. 19,
fig. 10.
cf. 1970 Ceratocephala cf. vesiculosa. – a
lberti
, p. 134, pl.
19, fig. 11.
cf. 1977 Ceratocephala vesiculosa. – k
obayasHi
& H
aMada
,
p. 87.
cf. 2010 Ceratocephala cf. vesiculosa. – o
Wens
et al., p. 215,
239-240, text-fig. 12K.
Material: Three poorly preserved cephala. Unfortunetaly, no
pygidium is available yet (PIMUZ 35172, 35173).
Remarks: These cephala can tentatively be assigned
to Ceratocephala cf. vesiculosa (beyriCH, 1846) due to
their shape and sculpture of the median glabellar lobe.
The absence of complete and better-preserved specimens
prevents unequivocal species assignment. Cephala
apparently sub-rectangular in outline, with width (tr.) about
1.84 in length. Glabella with subparallel sides and spinose
tubercles. Occipital ring strongly convex medially with
a posterior band, two broken probably prominent spines
laterally and a spinose tubercle medially. Fixed and free
cheeks with spinose tubercles. Free cheek with sigmoidal
lateral outline and numerous short marginal spines along
the border. These fragmentary specimens are very similar to
the material described by alberti (1970) from the Eifelian
of SE Rabat (Morocco). Moreover, alberti (1970) assigned
also a pygidium from the late Emsian of Hamar Laghdad VI
to Ceratocephala cf. vesiculosa.
Fig. 6. Trilobites from the late Emsian ‘Red Cliff’ at Hamar Laghdad, Tafilalt, Morocco. (a-c) Harpes hamarlaghdadensis
n. sp., Holotype, PIMUZ 35192: cephalon in frontal, dorsal, and lateral views. (d-f) Harpes hamarlaghdadensis n. sp.,
PIMUZ 35193: partially exfoliated cephalo-thorax in frontal, dorsal, and lateral views. (g-i) Harpes hamarlaghdadensis n.
sp., PIMUZ 35194: partially exfoliated cephalo-thorax in frontal, dorsal, and lateral views. (j-l) Harpes hamarlaghdadensis
n. sp., PIMUZ 35195: (j) cephalon in dorsal view, (k-l) detail of respectively glabella and anterolateral border. (m) Harpes
hamarlaghdadensis n. sp., PIMUZ 35196: partially exfoliated cephalon in dorsal view. (n) Harpes hamarlaghdadensis n. sp.,
PIMUZ 35197: cephalon in dorsal view. (o) Scabriscutellum sp., PIMUZ 35199: pygidium in dorsal view. (p) Scabriscutellum
sp., PIMUZ 35198: fragment of pygidium in dorsal view. Scale bars: 5 mm.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 259
Fig. 6.
eschweizerbart_xxx
260 Catherine Crônier et al.
Genus Leonaspis riCHter & riCHter, 1917
Type species: Odontopleura leonhardi barra nde, 1846,
Ludlow, Bohemia, Czech Republic.
Additional species from Morocco: Leonaspis hastata
albert i, 1967, Pragian, Ghtira Valley, northwestern
Morocco; L. grouensis alberti, 1970, early Ludlow,
Ghtira Valley, SE Rabat, northwestern Morocco; L. maura
a
lberti
, 1969, late Emsian, Ain Targa, western Morocco;
L. issoumourensis alberti, 1970, unknown age, maybe late
Emsian, Jbel Issoumour, southern Morocco; L. haddanei
CHatterton et al. 2006, late Emsian and Eifelian, south of
Foum Zguid, southern Morocco; L. spinicurva CHatterton
et al. 2006, late Emsian, south of Foum Zguid, southern
Morocco.
Remarks: raMsköld & CHatterton (1991) reviewed the
classification of the Odontopleuridae and placed Leonaspis
in the subfamily Odontopleurinae burMeister, 1843 and
they excluded numerous species previously assigned to
this genus. They included most of them in Kettneraspis
p
rantl
& p
řibyl
, 1949, a cosmopolitan genus with only two
interior pygidial border spines. Later, adrain & raMsköld
(1997) reassigned a number of Kettneraspis species to
Edgecombeaspis a
drain
& r
aMsköld
, 1997 and underlined
the need for a comprehensive analysis. Leonaspis is an
odontopleurin with two pairs of spines between the major
pygidial border spines. These two pairs of spines between the
major pygidial border spines are also present in Exallaspis,
an acidaspidin (cf. raMsköld & CHatterton 1991).
Leonaspis ? sp.
Fig. 4w
Material: Only one poorly preserved pygidium (PIMUZ
35174), but unfortunately no cephalon.
Remarks: This pygidium can be tentatively assigned to
Leonaspis ? sp. due to the number of pairs of border spines:
a single pair of anterolateral minor border spines, two pairs
of interior minor border spines and one pair of major border
spines. Pygidial length (not including marginal spines)
is about 0.33 of pygidial width. Minor border spines are
about half the length of major border spines. Median part
of terminal piece of axis is not separated from posterior
border by a distinct furrow. Only a single pair of prominent
tubercles between the border and the rib at the opposite of
the major marginal spines.
The absence of complete and better-preserved specimens
prevents an accurate assignment. This partially preserved
pygidium is similar to the material assigned to Leonaspis
issoumourensis described by alberti (1970) from the
southern slope of Jbel Issoumour from the late Emsian?
(Maider, Morocco) by the presence of a single pair of
prominent tubercles between the border and the rib opposite
of the major border spines. Our pygidium differs in having a
less elevated postaxial band (more inflated posterior border
in Leonaspis issoumourensis).
Our pygidium shares a shape similar to Leonaspis
haddanei CHatterton et al., 2006 from the Emsian of
southern Morocco. It differs in having shorter major pygidial
border spines. van viersen (2007) discussed the origine of
the pygidial spine pattern and postulated that Leonaspis
haddanei would best have been assigned to Kettneraspis
with a Leonaspis-type pygidial spine pattern.
Family Lichidae HaWle & Corda, 1847
Subfamily Trochurinae PHleGer, 1936
Genus Acanthopyge HaWle & Corda, 1847
Type species: Lichas haueri barrande, 1846, Eifelian,
Czech Republic.
Remarks: ebaCH & aHyonG (2001) proposed a detailed
phylogeny for Acanthopyge (Lobopyge) but they excluded
the Moroccan species. Nevertheless, in southern Morocco,
lichid taxa occur in the Early and Middle Devonian (Pragian
to Eifelian). Thus, CHatterton & Gibb (2010) described
the new species Acanthopyge (Lobopyge) bassei from the
Erbenochile Bed of the latest Emsian or early Eifelian from
Jbel Issoumour near Alnif (southeastern Morocco). However,
the trilobite genus Lobopyge is a junior homonym of the
millipede genus Lobopyge atteMs, 1951. özdikMen (2009)
proposed the trilobite genus Belenopyge peK & VaněK, 1991
to replace Lobopyge. More recently, CorbaCHo & kier (2013)
described the new species Acantopyge (Belenopyge) estuvei
from the Pragian of Jbel Oufatene and Jbel El Mrakib.
Nevertheless, a taxonomic reappraisal needs to be carried
out and a revision of the genus Acanthopyge is in progress
by budil et al. (Czech Republic).
Acanthopyge sp.
Fig. 4x-ab
Material: Three incomplete cranidia (PIMUZ 35175, 35176).
Unfortunately no diagnostic pygidia.
Remarks: These cranidia may be assigned to a trochurine
specimen (Acanthopyge) but their alteration prevents an
accurate assignment. Our specimens appear to differ from
Acanthopyge (Lobopyge) bassei CHatterton & Gibb, 2010
in having less coarse tubercles, a less protruding median
glabellar lobe, shallower and narrower longitudinal glabellar
and axial furrows. See CHatterton & Gibb (2010) for a
detailed description of their new species.
Description: Specimens with curved convex forward
anterior margin of cranidium. Anterior margin convex
medially and slightly protuberant into subangular extensions
where facial sutures meet the anterior margin. Preglabellar
furrow fairly shallow. Width (tr.) of frontal lobe of glabella
opposite eyes about 55% of maximum width of lobe near
preglabellar furrow. Median glabellar lobe not overhanging
anterior border. Longitudinal glabellar furrows extend
back to S0, faintly impressed across L1, deeply impressed
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 261
and divergent forward curving outward and backward
anteriorly to meet axial furrow. S1 rather deep and curved
back to merge with S0 medially, curved sharply anteriorly
to meet axial furrow. S0 rather deep. Preoccipital glabellar
lobes with a single enlarged tubercle. Eyes not preserved,
but located just behind midlength of anterolateral glabellar
lobes. Glabellar lobes as fixigenae with numerous moderate
size to large tubercles. Occipital lobe narrow (sag.). Axial
furrows inconspicuous across L1. Free cheek and genal spine
not preserved.
Order Corynexochida kobayasHi, 1935
Family Scutelluidae riCHter & riCHter, 1955
Remarks: For HolloWay & lane (2012), the concept of the
Scutelluidae matches with Scutelluinae sensu WHittinGton
(1999, p. 421) and they regard the taxon as a family rather
than a subfamily because of its wide range of morphological
diversity, possibly including several phylogenetic lineages.
Genus Scabriscutellum riCHter & riCHter, 1956
Type species: Bronteus scaber GoldFuss, 1843, Eifelian,
Germany.
Additional species from Morocco: Scabriscutellum
(Rheiscutellum) hammadi (CHatterton et al. 2006), late
Emsian, near Foum Zguid, southern Morocco; S. (R.) lahceni
(C
Hatterton
et al. 2006), late Emsian, near Foum Zguid,
southern Morocco; S. georgei a
lberti
, 1981b, early Emsian,
Hamar Laghdad, southeastern Morocco.
Remarks: ŠnaJdr (1960) gave a list of species assigned to
this genus. C
Hatterton
et al. (2006) followed Š
naJdr
(1960)
and provided a diagnosis for the genus Scabriscutellum.
This genus has a pygidium with seven paired pleural ribs,
like all other Devonian scutelluids, and a distally bifurcated
posterior median rib; pleural furrows flat bottomed or
convex upward, and distally about width of (or wider than)
pleural ribs; pygidial axis subdivided into at least three lobes
by slightly posteriorly convergent furrows; pygidial margin
entire or with a fringe of numerous very fine marginal spines.
basse & Müller (2016) redefined this genus and provided an
emended diagnosis for the genus Scabriscutellum in order to
recognize two subgenera: Scabriscutellum (Scabriscutellum)
is characterized by a quite broad (tr.) pygidial axis, pleural
ribs wide and mostly flattened, pleural furrows generally
convex bottomed; Scabriscutellum (Rheiscutellum) is
characterized by a rarther narrow (tr.) pygidial axis, pleural
ribs predominantly like a strip, and generally flat bottomed
pleural furrows.
In southern Morocco, scutelluid taxa occur in the Early
Devonian (Emsian). From Jbel Gara el Zguilma, near
Foum Zguid, CHattterton et al. (2006) thus described the
species Scabriscutellum (Rheiscutellum) hammadi with a
more semi-ovate than sub-pentagonal pygidium outline and
numerous very small spinules projecting from the margin
of the pygidium and to the second species, Scabriscutellum
(Rheiscutellum) lahceni, with a rounded sub-pentagonal
pygidium outline and an entire pygidial margin.
From the mudmounds of Hamar Laghdad, southeastern
Morocco, alberti (1981b) described two scutelluid species
from the Emsian assigned respectively to Scabriscutellum
georgei and Cavetia furciferum hamlagdadianum based on
incomplete material. Feist & CHatterton (2015) described
a new species assigned to Sagittapeltis belkai Feist &
Chatterton, 2015 from the latest early Emsian. alberti
(1970, 1981a) included specimens from the Pragian in
Platyscutellum? tafilaltense that could belong to a species of
Scabriscutellum, which is knownfrom incomplete cranidia
(see CHatterton et al. 2006 for discussion). alberti (1970)
described one scutelluid species from the early late Emsian
(see b
eCker
et al. 2018: p. 201, fig. 18e-f) of Hamar Laghdad
assigned to Scabriscutellum furciferum furciferum (=
Cavetia furcifera hamlagdadiana (Alberti, 1981b)) based
on an incomplete pygidium that could alternatively belong
to a species of Cavetia.
Scabriscutellum sp.
Fig. 6o-p
Material: Four poorly preserved pygidia (PIMUZ 35198,
35199). Unfortunately, no cephalon is available.
Remarks: These pygidia can be tentatively assigned to
Scabriscutellum due to its tiny spinose pygidial border. The
absence of complete and better-preserved specimens prevents
an accurate assignment. Pygidium apparently rounded sub-
pentagonal, with width (tr.) about 1.21 of length. Axis not
preserved. Interpleural furrows wider (tr.) than pleural ribs
distally. Pygidium apparently lacks any sculpture.
4. Interspecific and intraspecific variability
in phacopids
4.1. Method
The terminology used herein to describe the eye of
Phacopina is based on the work of Clarkson (1966).
The dimensions, especially the length and the width
of cephala in dorsal view have been obtained using
an optical image analyzer (TPSdig v.2.17; roHlF
2013). The discontinuous postembryonic growth by
successive molts results in size distributions often
clustered into stage groupings (dodd & stanton
1990). These size distributions allow growth to be
described using relatively simple numerical models. A
univariate or bivariate plot of size distribution within
a sample would be expected to show a discontinuous
growth curve, individuals being pooled in distinct
dimensional classes. Certain distribution sizes show
no evidence of stage peaks because of growth rates,
eschweizerbart_xxx
262 Catherine Crônier et al.
recruitment rates, and overlap in size between instars
(sHeldon 1988). In order to establish such a size series
in the studied species of phacopids we have constructed
a bivariate plot using the width as a function of the
length of cephala (Fig. 7a). Moreover, in order to follow
the morphological evolution of the eye, the number
of dorso-ventral files as a function of the cephalic
length has been recorded on bivariate diagrams for
cephala (Fig. 7b), and, in the same way the number of
lenses as a function of the cephalic length (Fig. 7d).
Additionally, the maximum number of lenses in one file
and the number of lenses have been plotted on bivariate
diagrams as a function of the number of files (Figs.
7c, 7e). Dimensions, especially the length and width of
cephala in dorsal view, were obtained using an optical
image analyzer (TPSdig v.2.17; rohlf 2013).
4.2. Results
Size distribution during ontogeny: The length/ width
plot of cephala (Fig. 7a) shows no distinct grouping,
i.e. no distinct instars. The growth series is essentially
represented by the holaspid period where no feature
allows distinguishing instars.
In addition, the relative proportions of each taxon
represented by sufficient material remain constant
(linear regression: y = ax + b; cephala: correlation
coefficient r = 0.905, probability value p<0.001***
significant at p<0.05 – for M. davidbrutoni n. sp.; r =
0.924, p<0.05* for M. forteyi; r = 0.962, p<0.001***
for M. granulops) whatever the degree of development
of individuals (Fig. 7a). Moreover, the correlation
is positive with width varying proportionally with
length. Overall, the studied phacopids present the
same evolution in size. Morocops davidbrutoni n. sp. is
represented mostly by small to medium-sized cephala,
whereas M. forteyi has medium-sized cephala. The
specimens assigned to Morocops sp. A are represented
by only two large-sized individuals. Of Morocops
granulops, only small to large-sized individuals
covering the entire size-range are available.
Dorso-ventral file distribution: The scatter diagram
of the number of files or lenses versus the cephalic
length shows that during growth, there is a trend to
increase the number of files (Fig. 7b) and lenses
(Fig. 7d). This is obvious in Morocops davidbrutoni
n. sp. and M. granulops, for which there are enough
specimens with a relatively important size range.
Additionally, some species are recognizable
according to their own file number: Morocops
davidbrutoni n. sp. is characterized by a reduced
number of dorso-ventral files, from 14 to 15, only the
three youngest individuals have 13 dorso-ventral files;
M. granulops is characterized by a higher number of
files, from 18 to 19, only the youngest individual has
17 dorso-ventral files; M. forteyi also shows 18 dorso-
ventral files, even if it is represented by only five
medium-sized cephala (Figs. 7b-c, e).
For comparison, in Morocops davidbrutoni n. sp.,
the minimum number of lenses is 17, the maximum
number is 49, and at the maximum height of the
eye, vertical files of three or four lenses alternate.
In Morocops granulops, the minimum number of
lenses is 33, the maximum number is 87, and at the
maximum height of the eye, vertical files of five lenses
alternate (six for the biggest specimens). In M. forteyi,
the minimum number of lenses is 45, the maximum
number is 53, and at the maximum height of the eye,
vertical files of four lenses alternate.
To sum up, during ontogeny, there is an addition
of lenses (less evident with files) in phacopine taxa.
Taxa with more files have also more lenses. To some
degree, phacopine taxa can be distinguished according
to their number of files and lenses, independently of
their variability.
5. Biodiversity analysis
5.1. Method
As in a previous study on Early Devonian (Emsian)
trilobites from Algeria (see kHaldi et al. 2016), the
Fig. 7. Bivariate plot using (a) the width (in mm) as a function of the length (in mm), (b) the number of files as a function
of the cephalic length (in mm), (c) the maximum of lenses in one file as a function of the number of files, (d) the number of
lenses as a function of the cephalic length (in mm), and (e) the maximum of lenses as a function of the number of files of
69 cephala of Morocops davidbrutoni n. sp., five cephala of M. forteyi (MCkellar & CHatterton, 2009), 30 M. granulops
(C
Hatterton
et al., 2006), two cephala of M. sp. A, 29 cephala of M. granulops (C
Hatterton
et al., 2006) from Algeria (data
from kHaldi et al. 2016).
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 263
Fig. 7.
eschweizerbart_xxx
264 Catherine Crônier et al.
current palaeobiodiversity study is based on counts
of specimens for each taxon identified in each studied
sample and their relative abundance. Additionally, to
evaluate the palaeobiodiversity components, several
ecological indices (HarPer 1999; HaMMer & HarPer
2006) have been used.
In order to evaluate the taxonomic diversity in
trilobites from the Hamar Laghdad outcrop, all the
complete and disarticulated sclerites were identified
and numbered from our sampling. Neverthelesscounts
of relative abundance may be biased due to physical
constraints such as segregation and/ or accumulation
of sclerites of different sizes and shapes by transport,
or simply by preferential collecting (sampling) and
preparation. To prevent that, we tried to limit the
counting number. For species represented either
by cranidia, cephala or complete exoskeletons,
and few pygidia (i.e., for phacopids), the counting
number concerns only cranidia, cephala or complete
exoskeletons (without pygidia) so as not to overestimate
the number of specimens. For species represented only
by pygidia or complete exoskeletons, the counting
number concerns only these sclerites. No hypostomes,
no free checks have been counted.
Moreover, in order to have a complete view of
the taxonomic diversity in trilobites from the Hamar
Laghdad, we compared our data with previously
published data from the same time-slice and locality,
i.e., the late Emsian of Hamar Laghdad, based on the
recently published list by beCker et al. (2018; Table
1) but with some emendations. We also compared our
data with previously published data from Jbel Gara
el Zguilma (Tindouf basin, Morocco) described by
C
Hatterton
et al. (2006; Table 2) from the late Emsian
of the lowermost part of the Timrhanrhart Formation,
and from Ouarourout (Saoura Valley, Algéria) from the
late Emsian of the ‘Chefar el Ahmar’ Formation (see
kHaldi et al. 2016).
Additionally, the following indices were then
used: Species richness (Dtot), Diversity (MR-index),
Dominance (D-index) and Equitability (E-index).
Species richness corresponds to the number of taxa,
i.e. species: Dtot = S. The reliability of this index being
highly dependent on the sample size, this index can
be completed by a rarefaction analysis (krebs 1989).
This last method compares the taxonomic diversity
in samples of different sizes, estimates the number
of expected taxa for any smaller sample size (adrain
et al. 2000; H
aMMer
& H
arPer
2006; b
alseiro
et al.
2010), and allows comparison of the curve slopes for a
reduced amount of individuals identical for all samples,
putting thus forward the relative biodiversity between
Table 1. Compilation of the Hamar Laghdad (Morocco) trilobite record from the upper Emsian extracted and emended
from beCker et al. 2008 (extracted from alberti papers and basse 2012).
Taxa Time-slice Number of specimens
Eremiproetus dufresnoyi saharae alberti, 1967b latest Emsian 1 specimen
Ignoproetus erfoudanus (alberti, 1981a) early late Emsian 11 specimens
Otarion (Otarionella) talaltense alberti, 1967b late Emsian 1 specimen
Phaetonella planicauda africanus alberti, 1981a early late Emsian 12 specimens
Scharyia hamlagdadica (alberti, 1981a) early late Emsian 7 specimens
Scharyia talaltensis alberti, 1970 late Emsian 1 specimen
Sculptoproetus sculptus posterior (alberti, 1970) early late Emsian 7 specimens
Tropidocoryphe memnon nepos alberti, 1970 late Emsian 3 specimens
Barrandeops cf. granulops (CHatterton et al. 2006; see kluG 2002) early late Emsian 7 specimens
Barrandeops granulops (CHatterton et al. 2006) early late Emsian 1 specimen in beCker et al. 2018
Barrandeops talaltanus (alberti, 1983) early late Emsian 3 specimens
Destombesina talaltensis MorzadeC, 2001 early late Emsian 1 specimen in beCker et al. 2018
Psychopyge elegans terMier & terMier, 1950 early late Emsian 5 specimens in MorzadeC 1988
Cavetia furcifera hamlagdadiana (Alberti, 1981b) early late Emsian 1 specimen in alberti 1981b, 1
specimen in beCker et al. 2018
Cyphaspis cf. boutscharanense (alberti, 1981a) late Emsian 1 specimen
Koneprusia cf. subterarmata (barrande, 1846) latest Emsian 1 specimen in alberti 1970
64 specimens
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 265
them. Moreover, another component of the biodiversity
has been used in this study, i.e. the rank abundance
curve (W
Hittaker
1965) with relative abundance vs.
abundance rank. This rank abundance curve is used
by ecologists to display the relative abundance and to
depict both richness and evenness (MaGurran 2004).
Diversity measures are usually standardized
against the sample size. The Shannon-Weaver index H
(sHannon & Weaver 1949) takes the individual number
as well as the number of taxa into account, it considers
the relative abundance of each taxon and gives weight
to rare species. This index varies from 0 for samples
with only one single taxon to high values for samples
with many taxa.
H = -Σ(ni/n) ln(ni/n)
with ni being the number of individuals of the taxon i.
Margalef’s richness index MR (MarGaleF 1958)
minimizes the sample size effect on estimating
biodiversity. The higher the Margalef value, the greater
the sample is diverse.
MR = (S-1)/ln(n)
Table 2. Summarized of the Jbel Gara el Zguilma trilobites described by Chatterton et al. 2008 from the upper Emsian
from the lowermost part of the Timrhanrhart Formation, Tindouf basin, Morocco.
Taxa Time-slice Number of specimens
Morocops granulops (CHatterton et al. 2006) late Emsian 9 specimens
Austerops menchikof (le Maître, 1952) late Emsian 11 specimens
Acastoides zguilmensis CHatterton et al. 2006 late Emsian 19 specimens
Acastoides haddadi CHatterton et al. 2006 late Emsian 1 specimen
Coltraneia effelesa CHatterton et al. 2006 late Emsian 3 specimens
Erbenochile erbeni alberti, 1981 late Emsian 1 specimen
Hollardops mesocristata (le Maître, 1952) late Emsian 7 specimens
Kayserops tamnrherta CHatterton et al. 2006 late Emsian 8 specimens
Psychopyge elegans terMier & terMier, 1950 late Emsian 1 specimen
Psychopyge praestans MorzadeC, 2001 late Emsian 5 specimens
Psychopyge hammerorum CHatterton et al. 2006 late Emsian 1 specimen
Walliserops hammii CHatterton et al. 2006 late Emsian 3 specimens
Walliserops tridens CHatterton et al. 2006 late Emsian 1 specimen
Walliserops trifurcatus MorzadeC, 2001 late Emsian 2 specimens
Parahomalonotus calvus CHatterton et al. 2006 late Emsian 6 specimens
Diademaproetus praecursor alberti, 1969 late Emsian 10 specimens
Diademaproetus cf. praecursor alberti, 1969 late Emsian 1 specimen
Gerastos tuberculatus marocensis CHatterton et al. 2006 late Emsian 7 specimens
Sculptoproetus sp. A CHatterton et al. 2006 late Emsian 2 specimens
Sculptoproetus cf. sp. A CHatterton et al. 2006 late Emsian 1 specimen
Tropidocoryphe amuri CHatterton et al. 2006 late Emsian 1 specimen
Cyphaspis agayuara CHatterton et al. 2006 late Emsian 1 specimen
Cyphaspis eberhardiei CHatterton et al. 2006 late Emsian 4 specimens
Cyphaspis hamidi CHatterton et al. 2006 late Emsian 11 specimens
Scabriscutellum lahceni CHatterton et al. 2006 late Emsian 1 specimen
Scabriscutellum hammadi CHatterton et al. 2006 late Emsian 2 specimens
Koneprusia dahmani CHatterton et al. 2006 late Emsian 4 specimens
Leonaspis haddanei CHatterton et al. 2006 late Emsian 3 specimens
Leonaspis spinicurva CHatterton et al. 2006 late Emsian 4 specimens
130 specimens
eschweizerbart_xxx
266 Catherine Crônier et al.
with S being the number of species and n the number
of individuals.
Dominance measures based on relative abundance
show high values for assemblages with a few common
elements, and low values when species are more or less
evenly represented. Dominance D = Σ(ni/n)²
The index varies from 0 (taxa equally represented)
to 1 (one dominant taxon).
Measures of equitability are usually the opposite of
dominance.
Equitability J = (-Σ(ni/n) ln(ni/n)) / lnS)
considers the uniformity of the distribution of
individuals among the present taxa. This index varies
from 0 to 1, reaching its maximum value when taxa
are fairly well represented with a similar number of
individuals.
Analyses were performed using the software PAST
v2.17 (HaMMer et al. 2001).
5.2. Results
Biodiversity. In Hamar Laghdad (Morocco), the
palaeobiodiversity of late Emsian trilobites is
particularly high, characterized by all five orders
recognized in the global record: Phacopida, Proetida,
Harpetida, Lichida and Corynexochida (Fig. 8a). In
our collection, eight families occur: Phacopidae and
Acastidae (Phacopida), which are well-represented
with five genera and eight species; Proetidae and
Aulacopleuridae (Proetida), which are also well-
represented with six genera and nine species;
Harpetidae (Harpetida), Odontopleuridae and Lichidae
(Lichida), as well as Scutelluidae (Corynexochida),
which are represented by only a few taxa. For
comparison, trilobite palaeobiodiversity from the
Emsian at the global and regional scales (Tafilalt
and Tindouf basin for Morocco vs Saoura Valley for
Algeria) is given in Figure 8a. The trilobite record
from our collection appears to complete previous data
from Hamar Laghdad with eleven additional genera
and sixteen other species (Figs. 8-10). Trilobites occur
in a high diversity as macrofaunal constituents in the
Emsian of the Tafilalt (Fig. 8a, ‘HL_tot’) and Tindouf
basin (Fig. 8a, ‘JeZ’), more than in the Saoura Valley
(Fig. 8a, ‘SV’). Nevertheless, the studied sample of
Algerian trilobites (kHaldi et al. 2016) is smaller than
those from Moroccan localities. At a global scale,
the basal Pragian eustatic sea level rise (House 2002)
and the climate warming (v
aCek
2011) has probably
contributed to the widening of shallow marine
carbonate realms, which are considered favourable
for the development of trilobite communities. This has
led to a stability of family level diversity, which lasted
with some minor changes until the early Eifelian. At
a regional scale, the marine transgression affected the
entire occidental Saharan platform at the beginning of
the late Emsian causing a switch from clay to carbonate
sedimentation (ouali MeHadJi et al. 2004, 2011).
New samples from the Tafilalt complete previous
collections and corroborate the occurrence of some
genera previously encountered in this area (Figs. 8b,
10) such as Cyphaspis, an aulacopleurid as mentioned
by alberti (1981a); Eremiproetus, a proetid as
mentioned by a
lberti
(1967); Morocops, a phacopid,
as mentioned by k
luG
(2002) and b
eCker
et al. (2018);
Destombesina, as mentioned by beCker et al. (2018);
and Psychopyge, an acastid, as mentioned by alberti
(1982).
Samples from the Tafilalt (new and old collections)
appear to complete our knowledge of the occurrence
of genera encountered in the Tindouf basin (Fig. 9a-
b, ‘JeZ’) or in the Saoura Valley (Fig. 9a, ‘SV’) and
corroborate some occurences of common genera such
as Cyphapis, Gerastos, Hollardops, and Morocops, in
these three areas (Fig. 9).
Phacopidae are represented in the studied outcrop
(Figs. 9-10) by only one genus, i.e., Morocops, against
two in the Jbel Gara el Zguilma section of the Tindouf
basin, in Morocco (data from CHatterton et al. 2006),
i.e., Austerops and Morocops, and five genera in the
Ouarourout outcrop of the Saoura Valley, Algeria
(data from see kHaldi et al. 2016), i.e., Austerops,
Boeckops, Adrisiops, Morocops and Phacops s.l.
Among these genera, only Morocops is encountered
in the late Emsian of Hamar Laghdad and Jbel Gara el
Zguilma (Morocco), and Ouarourout (Algeria), while
Austerops is encountered both in Jbel Gara el Zguilma
and Ouarourout, and the other phacopid genera are
encountered only in Ouarourout (Algeria). Acastidae
are represented by the four genera Destombesina,
Psychopyge, Hollardops and Comura; only Hollardops
is encountered in the late Emsian of Hamar Laghdad
(from our collection), Jbel Gara el Zguilma (see
C
Hatterton
et al. 2006) and Ouarourout (k
Haldi
et
al. 2016). Proetidae are represented by Cornuproetus,
Eremiproetus, Orbitoproetus and Gerastos at Hamar
Laghdad (Figs. 8b, 9). Of those genera, only Gerastos
is encountered in the late Emsian of Hamar Laghdad,
Jbel Gara el Zguilma in Morocco (CHatterton et
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 267
al. 2006), and Ouarourout in Algeria (kHaldi et al.
2016). Aulacopleuridae are represented by Cyphaspis
and Cyphaspides in our collection (plus Otarion and
Sharyia in earlier collections), Harpetidae by Harpes,
Odontopleuridae by Ceratocephala and Leonaspis in
our collection (plus Koneprusia in previous collections),
Lichidae by Acanthopyge, and Scutelluidae by
Scabriscutellum in our studied collection (plus Cavetia
Fig. 8. (a) Total occurrences of trilobite orders, families, genera and species from the Emsian at the global scale (modified
from F
eist
, 1991; C
hlupáč
, 1994), from the late Emsian of the Saoura Valley (‘SV’) in Algeria (data from k
Haldi
et al.
2016), from the late Emsian of the Tafilalt (‘HL’) in Morocco (our collection ‘HL_n’, previous collections ‘HL_o’, and all
collections ‘HL_tot’), and from the late Emsian of the Jbel Gara el Zguilma (‘JeZ’) in the Tindouf basin in Morocco (data
from C
Hatterton
et al. 2006); (b) number of individuals for each genus from the late Emsian of the Tafilalt in Morocco (our
collection ‘HL_n’, previous collections ‘HL_o’, see Table 1).
eschweizerbart_xxx
268 Catherine Crônier et al.
in previous collections) (Figs. 9, 10). Except Cyphaspis,
Cornuproetus, Gerastos, Hollardops, and Morocops,
none of these genera have been documented from the
late Emsian of Algeria yet (kHaldi et al. 2016). It has
to be noted, though, that some of the taxa known from
Ouarourout in Algeria and absent in Hamar Laghdad
may well occur in other localities in Morocco, such as
Erbenochile, Walliserops, and Austerops in Jbel Gara
el Zguilma section in the Tindouf basin.
In some details, diversity at genus and species levels
appears to be inequal (Fig. 8) between Hamar Laghdad,
Jbel Gara el Zguilma (Morocco), and Ouarourout
(Algeria), and taxa are not all equally well-represented
(Figs. 10-11). Genera and species appear to be better
represented in the Hamar Laghdad outcrop, and
especially with the combination of previous and new
data (‘HL_tot’) compared to the Ouarourout section
(‘SV’) in Algeria (Fig. 8). Moreover, the rarefaction
analysis shows that previous collections from Hamar
Laghdad (‘HL_o’) are under-sampled (see arrow, Fig.
11a-b) and seem to be more similar in diversity to our
data from Hamar Laghdad (‘HL_n’), especially at
species level (Fig. 11a). New data from Hamar Laghdad
(‘HL_n’) are better-sampled than previous ones
(‘HL_o’). If the Ouarourout section (‘SV’) is the section
with the lowest trilobite diversity, Hamar Laghdad
(with previous and new data ‘HL_tot’) and Jbel Gara el
Zguilma (‘JeZ’) are the sections with the highest species
Fig. 9. (a) Number of individuals for each genus from the late Emsian of the Saoura Valley (‘SV’) in Algeria (data from k
Haldi
et al. 2016), from the late Emsian of the Tafilalt (‘HL’) in Morocco (our collection ‘HL_n’, previous collections ‘HL_o’, see
Table 1), and from the late Emsian of the Jbel Gara el Zguilma (‘JeZ’) in the Tindouf basin in Morocco (data from CHatterton
et al. 2006); (b) number of individuals for each genus from the late Emsian of the Tafilalt (‘HL’) in Morocco (our collection
‘HL_n’, previous collections ‘HL_o’, see Table 1), and from the late Emsian of the Jbel Gara el Zguilma (‘JeZ’) in the Tindouf
basin in Morocco (data from CHatterton et al. 2006).
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 269
level trilobite diversity (Fig. 11a). At genus level, the
Hamar Laghdad curve (Fig. 11b, ‘HL_tot’) intersects
the Jbel Gara el Zguilma curve (Fig. 11b, ‘JeZ’) and
they do not allow comparisons. The main problem here
lies in the comparison of diversity between three areas
including different stratigraphical levels. Additional
studies and a bed by bed sampling are required to revise
and complete the list of Early Devonian trilobites in
North Africa. Moreover, the Hamar Laghdad area with
its mud mounds was probably ecologically controlled
by the paleohigh, unidirectional currents and repeated
storm events (b
raCHert
et al. 1992; see also k
luG
et al.
2018) leading to mixed faunas with autochtonous and
allochtonous components.
Ecological structure: On the basis of the relative
abundance and diversity of the trilobite macrofauna
(Figs. 8a, 11c-d), the Hamar Laghdad biota (‘HL_tot’) is
characterized by a high diversity (31 species, 24 genera
for 246 individuals) like the Jbel Gara el Zguilma biota
‘JeZ’ (27 species, 18 genera for 130 individuals). The
Hamar Laghdad biota from our collection (‘HL_n’) is
characterized by a moderate diversity (21 species, 16
genera for 182 individuals). It is thus higher than in the
Ouarourout biota from the Saoura Valley in Algeria
Fig. 10. Number of individuals in percent for each genus from the late Emsian of the Saoura Valley (‘SV’) in Algeria (data
from k
Haldi
et al. 2016), from the late Emsian of the Tafilalt (‘HL’) in Morocco (our collection ‘HL_n’, previous collections
‘HL_o’, all collections ‘HL_tot’), and from the late Emsian of the Jbel Gara el Zguilma (‘JeZ’) in the Tindouf basin in
Morocco (data from CHatterton et al. 2006).
eschweizerbart_xxx
270 Catherine Crônier et al.
Fig.11.
eschweizerbart_xxx
Trilobites from the Red Fauna (latest Emsian, Devonian) of Hamar Laghdad 271
(17 species, 11 genera for 182 individuals). The Hamar
Laghdad biota from our collection (‘HL_n’) is also
characterized by a moderate evenness (lower than in
Saoura Valley), with some better represented genera/
species (barely dominant genera/ species in the Saoura
Valley). The Hamar Lagdhad biota from our collection
(‘HL_n’) tends towards an ‘equilibrium’ community,
while the Ouarourout biota represents an ‘equilibrium
community’ (Fig. 11c-d). The Jbel Gara el Zguilma
biota (‘JeZ’) is the best ‘equilibrium’ community (Fig.
11c-d).
In addition, the rank-abundance curves confirms
that a small number of taxa are dominant (i.e.,
abundant), and the remaining taxa are rare in the
Hamar Lagdhad biota (Figs. 10, 11e-f). The steep slope
indicates a low evenness as the high-ranking taxa have
much higher abundances than the low-ranking taxa.
While a low slope indicates high evenness as the
abundances of different taxa are similar as seen in the
Jbel Gara el Zguilma biota (data from CHatterton
et al. 2016) that are almost in equal proportions with
a greater richness underlined by a higher number of
ranked taxa (Fig. 11e-f).
Trilobites are found in nodular limestones of late
Emsian age with a rich and diverse benthic fauna,
accumulated around the mounds (of latest early
Emsian age; see braCHert et al. 1992) because of
more favourable ecological conditions. These mounds
developed in an epicontinental basin below the
wave base but probably within the range of storms
(braCHert et al. 1992). Even if the diversity proxies
are representative of communities from which they are
sampled, at a low sample size, these diversity proxies
may suggest an incorrect ordering of relative diversity
among the total community comprising others groups.
Furthermore, the taxa abundance may change over time
because of abiotic (currents, storm events) or biotic
(predation, resource availability) factors. Additionally,
the studied area is represented by several levels.
Faunal mixing and some time-averaging likely has
occurred due to the mode of sampling (mostly surface
collected; kluG et al. 2018). The Red Fauna thus does
not represent an in-situ assemblage sensu stricto, i.e.
a palaeocommunity, where taxa are associated partly
because they have similar environmental tolerance and
partly because they interact with each other (brenCHley
& HarPer, 1998).
6. Conclusions
On the basis of our material, it has been possible to
identify new oculated species among the numerous
ones already known from Morocco. At both generic and
specific levels, the Moroccan faunule may be regarded
as diversified without marked original features and
closely related to other Moroccan areas of the same age.
The biometric analysis of phacopids is
complementary to their systematic and descriptive
study because it enables us to quantify and understand
their variability. More particularly, it allowed us to
discriminate a new species, Morocops davidbrutoni
n. sp., based on the number of lenses in the visual
complex.
New samples from the Red Cliff of Hamar Laghdad
corroborate the occurrence of Phacopida, Proetida,
Corynexochida or Odontopleurida in Northern Africa
as already mentioned by a
lberti
(1969, 1970, 1981a)
or CHatterton et al. (2006). Early Devonian strata are