The ontogeny and systematics of the otarionine trilobite Otarionella from the Devonian of the Montagne Noire, France and the Maider, Morocco

Abstract

A new otarionine trilobite Otarionella rastrum sp. nov., from the late Emsian Mont Peyroux Formation (Montagne Noire, France), is described. Silicified remains, recovered from the underlying Bissounel Formation (early to late Emsian), are also attributed to this new species. These isolated silicified sclerites represent metaprotaspid to young holaspid growth stages, which enables the almost complete ontogeny of an otarionine trilobite with a spinose adult morphology to be described for the first time. Comparison with associated larval and juvenile growth stages of Cyphaspis reveal that the pattern of juvenile cranidial spine distribution in Otarionella rastrum sp. nov. differs from all patterns described so far in the Otarioninae, in particular that characterizing the tribe Otarionini. A second species, Otarionella lkomalii sp. nov., known only from a complete articulated specimen discovered in the early Eifelian of southern Morocco, is also described. Like the middle Eifelian Otarionella chamaeleo (Basse, 1997), this new species has only ten thoracic segments, with the fourth and the sixth segments each bearing a long axial spine. In the light of the new elements provided by the ontogenetic sequence of O. rastrum sp. nov. and the adult specimens of this species and O. lkomalii sp. nov., the putative synonymy of Otarionella and Otarion is rejected and a restricted concept of the genus Otarionella is defined.

Full text

Geol. Mag. 145 (1), 2008, pp. 55–71. c
2007 Cambridge University Press 55
doi:10.1017/S001675680700386X First published online 13 September 2007 Printed in the United Kingdom
The ontogeny and systematics of the otarionine trilobite
Otarionella from the Devonian of the Montagne Noire, France
and the Maider, Morocco
RUDY LEROSEY-AUBRIL∗, RAIMUND FEIST†& BRIAN D. E. CHATTERTON‡
∗Laboratoire Magmas et Volcans, Universit´
e Blaise Pascal, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France
†Laboratoire de Pal´
eontologie, Institut des Sciences de l’Evolution, Universit´
e Montpellier II, Cc 062,
Place E. Bataillon, 34095 Montpellier Cedex 05, France
‡Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
(Received 25 September 2006; accepted 15 February 2007)
Abstract – A new otarionine trilobite Otarionella rastrum sp. nov., from the late Emsian Mont Peyroux
Formation (Montagne Noire, France), is described. Silicified remains, recovered from the underlying
Bissounel Formation (early to late Emsian), are also attributed to this new species. These isolated
silicified sclerites represent metaprotaspid to young holaspid growth stages, which enables the almost
complete ontogeny of an otarionine trilobite with a spinose adult morphology to be described for the
first time. Comparison with associated larval and juvenile growth stages of Cyphaspis reveal that the
pattern of juvenile cranidial spine distribution in Otarionella rastrum sp. nov. differs from all patterns
described so far in the Otarioninae, in particular that characterizing the tribe Otarionini. A second
species, Otarionella lkomalii sp. nov., known only from a complete articulated specimen discovered
in the early Eifelian of southern Morocco, is also described. Like the middle Eifelian Otarionella
chamaeleo (Basse, 1997), this new species has only ten thoracic segments, with the fourth and the
sixth segments each bearing a long axial spine. In the light of the new elements provided by the
ontogenetic sequence of O. rastrum sp. nov. and the adult specimens of this species and O. lkomalii
sp. nov., the putative synonymy of Otarionella and Otarion is rejected and a restricted concept of the
genus Otarionella is defined.
Keywords: Trilobita, Devonian, ontogeny, systematics, evolution.
1. Introduction
Surface sculpture (sensu Whittington & Wilmot, 1997)
on the cuticle of adult trilobites may be composed of
a great variety of structures (e.g. tubercles, spines,
pits, ridges). Pustules alone may be of various sizes,
ranging from tiny tubercles to long spines. They can
vary in internal structure (e.g. Fortey & Clarkson, 1976;
Størmer, 1980), be randomly dispersed or have a well-
organized distribution. This diversity in size, shape,
structure or distribution, along with their common
occurrence, encouraged authors to consider pustules as
fundamental features in long-lasting debates concern-
ing such topics as the segmentation of the trilobite body
(e.g. Whittington, 1956a, p. 182), the sensory organ
apparatus (Fortey & Clarkson, 1976; Wilmot, 1991) or
the mode of life of spiny trilobites (e.g. Whittington &
Evitt, 1954; Whittington, 1956b; Hammann & Rabano,
1987). However, the occurrence and distribution of
dorsal tubercles/spines in adults has proved to be
inconstant within many trilobite clades, which led to
their usefulness being questioned in systematics.
†Author for correspondence: rfeist@isem.univ-montp2.fr
The adults of most Devonian otarionines display
rather simple surface sculpture, composed of more or
less heterogeneously disposed tubercles. In addition,
some species possess spines on the glabella and on the
cephalic border. Whether or not these features should
be regarded as diagnostic at the generic or subgeneric
level remains a matter of debate. With the exception
of Pˇ
ribyl & Vanˇ
ek (1981, p. 173) and Basse (1997,
p. 199), who did not consider cephalic border spines to
have a high taxonomic value, most authors (e.g. Pˇ
ribyl,
1947; Prantl & Pˇ
ribyl, 1950; Erben, 1952; L¨
utke, 1961,
1965; Alberti, 1967, 1969, 1970, 1983; Chatterton,
Johnson & Campbell, 1979; Ellermann, 1992; Schraut,
2000) accepted the concept of Otarionella Weyer,
1965, as including all aulacopleurid species with
border spines in holaspides, regardless of other mor-
phological features. However, it soon became evident
that in characters other than spinosity, Otarionella
comprises some species close to Otarion Zenker,
1833, such as Cyphaspis coronatum Barrande, 1872,
Otarion (Coignouina)stephanum L¨
utke, 1961, Otarion
(Otarionella)tafilaltense Alberti, 1967, and many
others that are nearer to Cyphaspis Burmeister, 1843,
including Otarion (Otarionella)magnificum Alberti,

56 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
1967, Otarion (Otarionella?) sidiarounium Alberti,
1969, Otarion (Otarionella)proavus Alberti, 1970,
and Otarion (Otarionella)longispinosus Ellermann,
1992. Notwithstanding Otarionella being admittedly
polyphyletic (Alberti, 1969, p. 378; Thomas & Owens,
1978; L¨
utke, 1980, p. 115), it has been used as
a convenient ‘basket taxon’ for aulacopleurids with
cephalic border spines.
The early appearance during ontogeny of a sculptural
feature is considered to be a major criterion to suspect
its potential utility for discriminating high taxonomic
levels. If a feature occurs in a constant and precise
location (or in the same relative positions, if several
structures are involved), this precocious appearance
suggests that the structure develops under a strong
genetic control and thus is prone to evolve under
natural selection. In the case of major cephalic dorsal
spines/tubercles, this assumption is reinforced by the
fact that their distribution likely reflects, at least
to some extent, the segmentation of the head (e.g.
Whittington, 1956a). Adrain & Chatterton (1994)
were the first to recognize the potential usefulness
of juvenile cranidial spines in the systematics of
the Otarioninae. Using variations in number and/or
distribution of fixigenal, glabellar, and palpebral spines
in early meraspides, they identified three cephalic spine
patterns in the Otarioninae. One of these appeared to
be restricted to Otarion and Cyphaspis, thus enabling
Adrain & Chatterton (1994) to define a new tribe,
the Otarionini. These authors also showed that early
meraspides of otarionines usually display cephalic
border spines. These progressively reduce during
ontogeny until they can no longer be discriminated in
adult individuals of most species. Accordingly, they
regarded the persistence of such spines in holaspides
as a simple paedomorphic trait, probably acquired
independently in several lineages. This led them to
consider Otarionella a subjective junior synonym of
Otarion.
However, no early development of an otarionine with
a spinose adult morphology was hitherto known. One
such growth sequence is described here for the first
time, belonging to a new taxon, Otarionella rastrum
sp. nov., which belongs to a group of species centred
on the type of Otarionella,O. davidsoni (Barrande,
1852). As such, it is regarded as representative of the
ontogenetic development of this group. In the light
of the new information provided by this ontogenetic
sequence, and by adult specimens of O. rastrum sp.
nov. and O. lkomalii sp. nov., the putative synonymy of
Otarionella and Otarion is reconsidered.
2. Localities, environment and age
This contribution is the fourth describing silicified
trilobites from the early to late Emsian Bissounel Form-
ation, Montagne Noire, Southern France (Feist, 1970a;
R. Feist, unpub. Ph.D. thesis, Univ. Montpellier II,
1977; Lerosey-Aubril, 2007). The new material com-
prises silicified early growth stages (metaprotaspides to
early holaspides) from this formation and calcareous
holaspides from the overlying late Emsian Mont
Peyroux Formation. Associated early growth stages of
Cyphaspis are figured and discussed for comparison.
The silicified growth stages of O. rastrum sp.
nov. were recovered from the type locality of the
Bissounel Formation (Feist, 1985) situated on the
northwestern slope of Bissounel Hill (‘Vissounel’
on topographical maps), 2.8 km NW of Cabri`
eres,
Montagne Noire, southern France (Fig. 1). At this
locality, the lowest of the three members of the 100 m
thick Bissounel Formation is characterized by well-
bedded, grey marly limestones. Faunas comprising
Anetoceras, asteropygine and phacopine trilobites and
the conodonts Polygnathus dehiscens and P. gronbergi
indicate an early Emsian age (Feist, 1970b). The middle
member comprises ochre-brown marls and grey or
grey-brown limestone beds which are sometimes marly
and more often microsparitic. They contain numerous
chert lenses and ribbons as well as large silicified cup-
shaped tabulate or stromatoporoid colonies (‘calcaires
`
a polypiers siliceux’, auct.). Environmental conditions
are interpreted to have been rather clear and shallow
waters, subject to tidal and wave action, rich in
oxygen and nourishment. Among organisms present,
reef-builders form extended biostromal lenses within
dense growths of crinoids and bryozoans. A few
brachiopods, and rugose corals such as Calceola
sandalina, occur. Siliceous diagenetic processes not
only affected macrofaunas but also thin-shelled dacryo-
conarids, ostracods (Feist & Groos-Uffenorde, 1979)
and bryozoans (Bigey & Feist, 1976), as well as
growth stages of chonetid brachiopods, bivalves, and
trilobites. The prevalence of spinose and sculptured
shells is striking. Conodonts are absent and the age
of this interval can be assigned only approximately
to an undifferentiated nothoperbonus–inversus interval
(passage from early to late Emsian). The upper member
consists of grey-brown crinoidal chert-less limestones.
Index conodonts, such as Polygnathus laticostatus,
indicate the inversus Biozone, basal late Emsian.
The Bissounel Formation is overlain by the lower
member of the Mont Peyroux Formation, which
consists of massive, micritic, light-grey and red-
speckled limestone forming the top of Bissounel Hill,
Pic de Bissous and Hill 340 at Col de Mour`
eze (Fig. 1).
Rich accumulations of trilobites of Bohemian type
occur in places. Rare conodonts indicate a serotinus
Zone age, early late Emsian (Feist, Sch¨
onlaub &
Bultynck, 1985).
The silicified growth stages of Otarionella that were
recovered from the middle member of the Bissounel
Formation are uppermost early Emsian through lower-
most late Emsian in age, and as such they are slightly
older than the limestone material of O. rastrum sp.
nov. from the overlying Mont Peyroux Formation (early

Ontogeny and systematics of Otarionella 57
Figure 1. Location of silicified and calcareous trilobite beds. (a) Location of Cabri`
eres area in the southeastern Montagne Noire,
southern France (vertical hatch lines indicate pre-Mesozoic massifs). (b) Location of sites in the Devonian Pic de Bissous mountain
range north of Cabri`
eres village, 8 km SW of Clermont-l’H ´
erault township. Site 1, western slope of Bissounel peak. Site 2, southwestern
vicinity of hill 340 at Col de Mour`
eze, WNW of Bissous peak. (c) Vertical section through the Bissounel and Mont Peyroux formations
showing silicified faunas (site 1) and calcareous faunas (site 2).
late Emsian). The comparison of early holaspides
from both levels revealed no diagnostically significant
differences. Accordingly, both sets of material are
attributed to the same species.
No articulated specimens have been found in the
Montagne Noire. The first complete carapaces of an
otarionine with anterior border spines were figured
by Basse (1997, plate 11, figs 10, 11), who assigned
them to Cyphaspis chamaeleo Basse, 1997; these are
refigured here for comparison. They come from the
higher part of Ohle Formation (middle Eifelian) of
Endorf, western Sauerland region, eastern Rhenish
Slate Mountains, Germany.
The Moroccan species Otarionella lkomalii sp. nov.
is a rare component of the trilobite fauna in a bed
known locally as the ‘Ceratarges Couche’, which crops
out near the base of a section located close to Jbel
Zireg at the south end of the Maider Basin. It has
been mined commercially for some distance along
strike for its trilobite fauna, which includes species of
Ceratarges,Cornuproetus,Cyphaspis,Gerastos, Ota-
rionella,Phacops, Radiaspis (very rare), Thysanopeltis
and a large styginid. The trilobites from this bed and
those from another also mined for trilobites lying 27 m
above in the same section, the ‘Thysanopeltis Couche’
which contains Cornuproetus, Gerastos, Leonaspis,
Phacops and Thysanopeltis, suggest an Eifelian age.
The strata that form the part of the section at this locality
consist of fairly pure limestone. They are largely
micritic, and contain a fauna suggestive of deposition
on an open marine shelf. Other fossils include crinoids
and the trace fossil Chondrites. Kaufmann (1998, fig. 5)
showed that the Jbel Zireg region was located in a
region of platformal or basin margin neritic facies
(fossiliferous limestones) on the south side of the
Maider Basin during the Eifelian costatus Zone.
Hollard (1974, fig. 4) presented a stratigraphic
column through some of the Devonian strata of Jbel
Zireg. His section is located on the other limb of
the same anticline as the locality that yielded the
species described herein. There is a problem in applying
formation names to the limestone and shale rock units

58 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
Figure 2. Otarionella rastrum sp. nov. (a–m, t–v) Scanning electron micrographs of silicified specimens from the middle member of
the Bissounel Formation (early to late Emsian), Bissounel Peak, Montagne Noire, France. (n–s, w–y) Digital photographs of calcareous

Ontogeny and systematics of Otarionella 59
of Middle Devonian age in this part of Morocco. Many
were defined rather loosely by Hollard (1974) and
vary so much lithologically that they seem to have
been as much based on age as on lithology. In more
recent publications, these names have been applied to
stratigraphic sections in a rather inconsistent fashion,
with formational boundaries sometimes drawn in the
middle of comparatively uniform sequences of strata.
The boundary between the El Otfal Formation and the
Taboumakhloˆ
uf Formation (Hollard, 1974, pp. 46, 49,
fig. 4) is particularly problematic. These are the two
formational names most likely to have been applied to
the strata of Eifelian age in Jbel Zireg that contain O.
lkomalii sp. nov. Some authors seem to have placed
the boundary between these formations on the basis of
age or fossil zone (the change from dm1 to dm2: e.g.
Hollard, 1974; Kaufmann, 1998, fig. 31) rather than at a
distinct, mappable change in lithology. Because of these
problems of correct application of formation names
in this region, some authors illustrating stratigraphic
columns of Lower and Middle Devonian strata from the
Maider basin have chosen to ignore formation names
altogether in favour of labelling their stratigraphic
columns with ages and biostratigraphic zones (usually
conodont or ammonoid zones). The most likely name
to be applied to the strata bearing O. lkomalii sp. nov.
near Jbel Zireg is the El Otfal Formation (see Hollard,
1974, fig. 4; Hollard, 1981, table 3).
Silicified and calcareous specimens of O. rastrum
sp. nov., as well as latex casts of the original material
of O. chamaeleo, are housed in the Collections of
Invertebrate Palaeontology of the University Montpel-
lier II (UMC- IP490–543). The single specimen of O.
lkomalii sp. nov. is deposited in the type collection of
the University of Alberta (UA11821).
3. Systematic palaeontology
Terminology. Morphological terms and abbreviations used
herein follow those defined by Whittington et al. (1997).
Fixigenal, glabellar and palpebral spines in early growth
stages have been abbreviated by respectively Fx, G and P,
as introduced by Adrain & Chatterton (1994). Additional
abbreviations are: Bd – dorsal spine of the librigenal lateral
border; Blm – long marginal spine of the librigenal lateral
border; Bsm – short marginal spine of the librigenal lateral
border; Gd – dorsal spine on the genal spine; Gm – marginal
spine on the genal spine. These are summarized in Figure 5.
Order PROETIDA Fortey & Owens, 1975
Fam ily AULACOPLEURIDAE Angelin, 1854
Subfamily OTARIONINAE Richter & Richter, 1926
Genus Otarionella Weyer, 1965
Type species. Cyphaspis davidsoni Barrande, 1852, Sucho-
masty Limestone (early late Emsian), Prague district, Czech
Republic.
Diagnosis (emend.). Cephalon like in Cyphaspis, but with
two or three evenly spaced pairs of spines on median glabellar
lobe, prominent and large glabellar basal lobes (L1), three
fixigenal spines (Fx1–3) present in early meraspides that
become reduced in holaspides, where only the posterior one
usually remains; single transverse row of tubercles across the
preglabellar field; anterior border of the cranidium carrying
six evenly spaced spines on prominent crest, prolonged on
the librigenal border by four spines, second row of spines
displayed on the lower part of outer margin. Occipital
spine always present. Thorax with ten segments, axial
spines consistently developed on fourth and sixth segments,
sometimes on second segment; pygidium small, axis at least
as large as pleural field, merging with postaxial field, three to
five axial rings.
Assigned species. Cyphaspis davidsoni Barrande, 1852,
early late Emsian, Czech Republic; Otarion spinafrons
Williams in Cooper & Williams, 1935, Givetian, USA;
Otarion (Otarionella)greifensteinensis Schraut, 2000, basal
Eifelian, Germany; Cyphaspis chamaeleo Basse, 1997,
middle Eifelian, Germany; Otarionella lkomalii sp. nov.,
early Eifelian, Morocco; Otarionella rastrum sp. nov.,
early late Emsian, France. Tentatively assigned: ?Cyphaspis
stephanophora Hall in Hall & Clarke, 1888, Eifelian,
USA; ?Otarion (Otarionella)bensaidi Alberti, 1983, basal
Eifelian, Morocco.
Otarionella rastrum sp. nov.
Figures 2a–y, 3a–cc
Remarks. This taxon was informally introduced in the
unpublished thesis of R. Feist (Univ. Montpellier II, 1977)
and incorrectly cited in Basse (1997, p. 122) as ‘C. rastra
t.sp.’ (nom. nud., sic!).
Material. Nine cranidia, 2 librigenae, 1 pygidium in lime-
stone preservation; 3 metaprotaspides and about 50 cranidia,
6 hypostomes, 20 librigenae, 20 transitory pygidia and
pygidia silicified.
Etymology. From latin rastrum, rake, referring to the spiny
margin of the cephalon.
Type locality and horizon. Hill 340 of Col de Mour`
eze,
2.6 km NNW of Cabri`
eres village, H´
erault, France. Lower
member of the Mont Peyroux Formation (Feist, 1985). Un-
bedded pink-white speckled biomicrites. Early late Emsian
(Polygnathus serotinus Biozone).
specimens from the Mont Peyroux Formation (late Emsian), Montagne Noire, France. Scale bars 0.25 mm (a–e) and 0.5 mm (f–y).
(a–e) Metaprotaspides; (a) dorsal view, UMC-IP490; (b) dorsal view, UMC-IP491; (c–e) specimen with anterior border broken, UMC-
IP492; (c) dorsal view; (d) left lateral view; (e) postero-lateral view. (f–r) Cranidia, dorsal views; (f) smallest meraspid specimen,
UMC-IP493; (g) meraspis, UMC-IP494; (h) meraspis, UMC-IP495; (i) meraspis, UMC-IP496; (j) meraspis, UMC-IP497; (k) meraspis
(?), UMC-IP498; (l) meraspis (?), UMC-IP499; (m) meraspis (?), UMC-IP500; (n) holaspis (?), UMC-IP501; (o) holaspis, UMC-IP502;
(p) holaspis, UMC-IP503; (q) holotype, holaspis, UMC-IP504; (r) holaspis, UMC-IP505; (s) holaspis, anterior view, UMC-IP506. (t,
u) Fragments of the anterior region, anterior views; (t) small specimen, UMC-IP507; (u) large specimen, UMC-IP508. (v–x) Right
lateral views; (v) meraspis, UMC-IP496; (w) holaspis (?), UMC-501; (x) holaspis, UMC-IP502; (y) mirrored left lateral view, holaspis,
UMC-IP505.

60 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
Figure 3. Otarionella rastrum sp. nov. (a–g, j–y, aa, bb) Scanning electron micrographs of silicified specimens from the middle
member of the Bissounel Formation (early to late Emsian), Bissounel Peak, Montagne Noire, France. (h, i, z, cc) Digital photographs
of calcareous specimens from the Mont Peyroux Formation (late Emsian), Montagne Noire, France. Scale bars 0.5 mm (a–s) and
0.25 mm (t–cc). (a–g) Librigenae, dorsal views; (a) smallest meraspid specimen, UMC-IP509; (b) meraspis, UMC-IP510; (c) meraspis
(mirrored), UMC-IP511; (d) meraspis, UMC-IP512; (e) meraspis (?), UMC-IP513; (f) meraspis (?) (mirrored), UMC-IP514; (g)
holaspis (?) (mirrored), UMC-IP515. (h, i) Librigenae, dorso-lateral views; (h) holaspis with genal spine broken, UMC-IP516; (i)
holaspis with lateral border broken (mirrored), UMC-IP517. (j) Right librigena, ventral view (mirrored), UMC-IP518. (k) Left librigena
(note the three rows of lateral border spines), lateral view, UMC-IP519. (l–n) Hypostomes, ventral views; (l) UMC-IP520; (m) UMC-
IP521; (n) UMC-IP522. (o–s) Thoracic segments with (o, q, s) or without (p, r) an axial spine; (o) right lateral view, UMC-IP523;

Ontogeny and systematics of Otarionella 61
Holotype. Large holaspid cranidium, UMC-IP504,
Figure 2q.
Diagnosis. Glabella short ovoidal, strongly inflated; pos-
terior pair of glabellar spines lost in late holaspis; large,
inflated L1 lobes; anterior margin transversely furrowed, two
pairs of secondary marginal spinules connected to major
spines by low ridges; short (sag. and exs.) occipital ring
with strong spine; posterior cranidial margin spinose; anterior
facial sutures parallel to axis; long and slender librigena with
seven long spines (Blm1–7) on border margin and inwardly
curved genal spine. Pygidium convex with high axis carrying
5+1 well-defined axial rings.
Description. Glabellar middle lobe egg-shaped (length/
width ratio =1.31, tending to increase with age); widest
(tr.) opposite γ, steadily converging behind, broadly rounded
at base, highly convex in lateral view culminating shortly
behind δ, strongly declining both towards the front and to
the rear, overhanging preglabellar field in lateral view when
occipital ring held in vertical position, provided with three
equidistant and adaxially situated pairs of strong tubercles
(G1–3), with G2 and G3 more prominent than G1, the latter
tending to be lost in late holaspides (Fig. 2o–s, x, y); S1 very
deep in anterior, shallowing towards posterior, as wide (tr.)
as adjacent portion of axial furrow; S2 not discernible; L1
rather prominent, protruding laterally, strongly inflated, pear-
shaped with pointed anterior ends extending as far forward
as the posterior part of the palpebral lobe; axial furrows
broad and deep, slightly divergent rearwards; preglabellar
furrow shallow and overhung by anterior half of glabella,
with a tiny axial pit on some specimens (not visible
on Fig. 2s); preglabellar field narrow (sag.), no longer
than occipital ring, vaulted sagittally, convex adjacent to
preglabellar furrow, merging with broad, steep-sided border
furrow of transversely even breadth, provided with a row of
coarse tubercles that runs transversely in parallel with the
preglabellar furrow (e.g. Fig. 2o); anterior border modestly
curved transversely, evenly arched in frontal view, carrying
prominent crest, semicylindrical in section, sharply raised
against border furrow, provided with strong, evenly spaced
spines of moderate length, horizontally outstretched when
occipital ring in vertical position, separated from outer,
anterior part of border by transverse furrow (Fig. 2s, u);
anterior outer part of anterior border below border furrow
forming sharp, slightly protruding edge provided with two
pairs of small spines, the medial pair being thicker than
the external one, all situated opposite and below main
spines on the crest, adaxial ones being connected to the
latter by a shallow ridge that interrupts the transverse
furrow; occipital furrow forming a shallow transverse
depression that remains of constant length (sag., exs.)
between basal glabellar lobes, behind which it narrows and
deepens considerably before merging with both axial and
posterior border furrows; occipital ring as long (sag.) as
occipital furrow, modestly narrowing laterally, transversely
narrower than basal glabella, moderately vaulted (sag., exs.),
carrying a median spine of length equal (sag.) to L1 (exs.),
and a prominent tubercle on each side at half distance
between medial spine and distal end of occipital ring;
fixigenae between glabella and palpebral lobe moderately
inclined towards axial furrow and as large (tr.) as L1,
arched both transversely and from front to rear, sloping
less posteriorly than anteriorly, carrying a strong tubercle
(Fx1) in middle of posterior fixigenal field (e.g. Fig. 2y);
anterior branches of facial sutures straight, parallel to axis;
posterior branches subparallel in their anterior halves, turning
gently outwards posteriorly; palpebral lobe small, upraised,
carrying a single tubercle; posterior border semicylindrical in
section, slightly flexed backwards and broadening externally,
provided with nodes on its inner third and near to the
suture.
Librigena with base of genal spine inwardly curved
at genal angle, longer (exsag.) than cranidium (Fig. 3h,
i); genal field modestly vaulted carrying strong widely
spaced tubercles; eye ovoid, upraised, sitting on swollen,
unornamented platform that extends forwards and back-
wards; lateral border furrow wide, concave, merging with
librigenal field, more sharply delimited against upturned
lateral border, interrupted before reaching genal angle by
bridge-like swelling that links the librigenal field with border;
posterior border furrow enlarged, without defined groove or
pit; lateral border robust, cylindrical, as wide as abaxial part
of posterior border and base of genal spine, carrying four
thick upraised dorsal spines (Bd1–4) and, below them, seven
downwards directed, long marginal spines (Blm1–7).
No adult thoracic segment known. Pygidium with narrow
parabolic posterior outline (length/width ratio: 0.5, excluding
articulating half-ring); axis high, slightly flat-topped, evenly
arched from front to rear in side view, 1.2 times wider
(tr.) than pleural field, with 5+1 rings, the three anterior
ones inflated and clearly separated by straight inter-ring
furrows that become shallower from front to rear, remnant
articulating half-ring developed on second ring (Fig. 3z, cc);
axial furrows straight, moderately converging, very deep at
second and third ring but shallowing behind to merge with
inflated postaxial field; fulcrum at one-third of way out from
axial furrow; inner, horizontal inner part of pleural field
separated from deeply inclined outer part by sudden break
in slope that corresponds to the fulcral line; three pleurae,
flexed at fulcral line, differentiated into narrower anterior
bands and slightly broader and higher posterior ones, both
separated by deep pleural furrows that suddenly terminate
towards edge of pleural field; interpleural furrows weaker and
narrower than pleural furrows but extending to margin where
they are slightly backwardly-curving; postero-lateral margin
without border. Sculpture: besides spines and prominent
tubercles, smaller drop-like granules are present on glabellar
and occipital lobes, fixigenae, axial rings and pleural
bands (where they are coarser on fulcral line); cephalic
borders with finer granules; anterior preglabellar field,
external part of librigenal field and border furrows densely
pitted.
Comparisons. The new species shares with the approxim-
ately contemporaneous O. davidsoni the general outline and
(p) posterior view, UMC-IP524; (q) anterior view, UMC-IP525; (r) dorsal view (front to the top), UMC-IP526; (s) dorsal view (front
to the top), UMC-IP527. (t–z) Transitory pygidia and pygidia, dorsal views; (t) meraspid degree 2, UMC-IP528; (u) meraspid degree
3, UMC-IP529; (v) large meraspid degree 3, UMC-IP530; (w) meraspid degree 4, UMC-IP531; (x) meraspis, UMC-IP532; (y) small
holaspis (?), UMC-IP533; (z) large holaspis, UMC-IP534. (aa) Small meraspis, ventral view, UMC-IP535; (bb) meraspid degree 2,
lateral view (mirrored), UMC-IP528; (cc) large holaspis, lateral view, UMC-IP534.

62 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
Figure 4. Otarionella chamaeleo (Basse, 1997), middle Eifelian, Ohle Formation, Sauerland, Germany. All figures are digital
photographs. Scale bars 1 mm. (a, b) Holotype; (a) latex cast of the external moult, right lateral view, UMC-IP536; (b) latex
reproduction of the internal moult, dorsal view, UMC-IP537; (c) latex reproduction of an external moult, dorsal view, UMC-IP538.
convexity of the cephalon and the glabella but differs from
it in the larger and more inflated L1 that are closer to each
other, the shorter (sag.) occipital lobe and the much longer
librigenal spines. It is more closely related to the slightly
younger O. greifensteinensis. However, the latter has a more
elongated glabella with a greater length/width ratio, a steeper
frontal slope and the culmination of longitudinal convexity
situated further forwards. O. rastrum sp. nov. resembles O.
spinafrons from the late Middle Devonian from the Tully
Limestone, especially in the distribution of spines on the
glabella and the margins; however, the latter has a less convex
glabella, denser tuberculation and larger, triangular, more
forwardly extended L1. Unfortunately no pygidia are known
from these species. Two entire exoskeletons of O. chamaeleo
(Basse, 1997 and refigured herein, Fig. 4a–c) are known.
Whereas the cephalic features of this species and O. rastrum
sp. nov. are largely identical (excepting the shorter occipital
ring and preglabellar field, the parallel anterior facial sutures
and the longer librigenal spine in the latter), the pygidia are
distinct, mainly in the longer axis with more differentiated
rings, the narrower pleural field and the longer interpleural
furrows that characterize O. rastrum sp. nov.
O. rastrum sp. nov. differs from the early Eifelian O.
lkomalii sp. nov (Fig. 6a–f), also known from an entire
exoskeleton, in the following characteristics: the L1 lobes are
smaller and more triangular (anteriorly pointed) in shape; the
frontal lobe does not overhang the preglabellar furrow and
preglabellar field to such an extent; the occipital furrow is
shorter (sag. and exs.) and does not widen as much adjacent
to the adaxial side of L1; the occipital spine is relatively finer
and perhaps longer; there is a distinct pair of spines on the
posterior margin of the occipital ring, about half-way between
the occipital spine and the axial furrows; the preglabellar field
is longer (sag.); the cephalic border is narrower (sag.); the
palpebral lobe lacks a medial pit, distal to a distinct palpebral
tubercle; Fx1 is distinct; the genal spines are longer and more
curved; the pygidium is more elongate (sag.).
Ontogeny. Anaprotaspis unknown. Three metaprotaspid
specimens (Fig. 2a–e) are confidently assigned to Otarionella
rastrum sp. nov. because of the great similarity of their
protocranidia to the smallest cranidia of this species, in
particular regarding the cephalic spine pattern. These three
specimens may represent a single metaprotaspid stage. It
is slightly elongate, 0.418–0.441 mm in sagittal length and
0.378–0.411 mm in maximum width (tr.); glabella rounded
antero-medially, and reaching anterior border furrow; axial
furrows rather deep except adjacent to the posterior
preoccipital glabella where they shallow; preglabellar furrow
faint; no glabellar furrows discernible; occipital furrow broad
and shallow; occipital ring narrow (tr.); anterior border
furrow faint and backwardly curved abaxially; anterior
border moderately inflated; facial suture slightly diverging
backwards; palpebral lobes poorly differentiated; no eye
ridges and posterior border furrow discernible at this stage;
junction between the protocranidium and the protopygidium
marked by a shallow and broad furrow that strongly curves
backwards abaxially. Protopygidium short (sag. and exs.)
with a medially re-entrant posterior margin; axial furrows
rather deep; axis almost reaching posterior margin and
comprising two rings, well separated by a rather deep
inter-ring furrow; no pleural or interpleural furrows visible.
In lateral view, larvae slightly and almost symmetrically
vaulted; axial lobe moderately inflated (Fig. 2d). Sculpture:
G1–G3 sharp and evenly spaced, decreasing in length from
front to rear (Fig. 2d); median occipital spine robust and
long (Fig. 2d, e); Fx1–3 projecting dorsally, with Fx1, Fx2
and Fx3 located roughly opposite to middle distance between
occipital spine/G1, G1/G2 and G2/G3 respectively; P1 and
another spine are present near lateral margins, with P1
located opposite Fx3 and the other spine roughly opposite
to G1; two additional spines located in postero-lateral corner
of protocranidium; six aligned and evenly spaced anterior
border spines that project dorsally and slightly forwards. The
first protopygidial segment bears a short axial spine and is

Ontogeny and systematics of Otarionella 63
Figure 5. Spine distribution in early meraspid cranidium of Cyphaspis (a), and in early meraspid cranidium (b) and librigena (c) of
Otarionella. Bd – dorsal spine of the librigenal lateral border; Blm – long marginal spine of the librigenal lateral border; Bsm – short
marginal spine of the librigenal lateral border; Fx – fixigenal spine; G – glabellar spine; Gd – dorsal spine on the genal spine; Gm –
marginal spine on the genal spine; P – palpebral spine.
probably represented laterally by a pair of pleural spines; the
second protopygidal segment displays a larger and longer
axial spine but it likely bears a single pleural spine only.
Librigena and hypostome unknown.
The smallest cranidium (Fig. 2f) is only slightly larger than
protocranidia and accordingly may represent the first mer-
aspid stage. Although the two stages are very similar, a few
shape changes can be described: relative overall width (tr.)
slightly increases; axial, occipital and anterior border furrows
deepen and narrow; palpebral lobes widen (tr.); appearance
of faint and backwardly curved S1, faint eye ridges, and pos-
terior border furrows that are straight adaxially, but strongly
curved forwards abaxially; convexity of posterior occipital
margin increases; posterior branch of facial suture becomes
outwardly curved and more divergent backwards; the more
posterior of the two postero-lateral corner spines shortens sig-
nificantly while the other becomes more robust and appears to
be located on the posterior border of the cranidium (Fig. 5b).
From this early meraspid stage to the more advanced
holaspides, the following shape changes can be observed
(Fig. 2g–r): glabella significantly widens (tr.), in particular
posteriorly, where L1 greatly widens (tr.) at the expense
of the posterior fixigenal field; axial furrows remain rather
wide throughout ontogeny but they deepen strongly and
increasingly diverge backwards; preglabellar furrow slightly
deepens, with a tiny axial pit appearing in some holaspid
specimens; S1 significantly deepens in late meraspides,
especially in its anterior two-thirds; occipital furrow remains
rather large but deepens strongly throughout ontogeny;
occipital ring widens (tr.) and shortens (sag.); preglabellar
field rapidly appears and broadens (sag.), only moderately
narrowing in late ontogeny; anterior border furrow deepens
moderately and rapidly straightens along with the anterior
border in earliest meraspides; backward convergence of
anterior sutures first increases then decreases; ε–ω(posterior
suture) initially straightens until the appearance of ζ,then
ε–ζand ζ–ωrespectively decreasingly and increasingly
diverge backwards; palpebral lobes widen (tr.) in early
ontogeny; eye ridges rapidly vanish; posterior border furrow
deepens slightly and narrows. In lateral view (Fig. 2v–y),
glabella significantly inflates dorsally and towards anterior,
becoming bulbous and overhanging the preglabellar field in
late holaspid stages; occipital ring decreases in height while
palpebral lobes elevate. Sculpture evolves as follows: G1–
3 initially increasing (Fig. 2g–l) then decreasing in length
(Fig. 2m–r) until G2 and G3 represented by no more than
strong tubercles while G1 almost completely vanish (Fig.
2r); occipital spine decreases in relative diameter and length;
a sharp but tiny marginal spine appears on either side of
the occipital spine in late meraspid stages (Fig. 2l), at
about middle distance between occipital spine and axial
furrows, then it decreases in length to become no more
than a prominent tubercle (e.g. Fig. 2m, p, r); Fx2 and Fx3
rapidly vanish during early meraspid period (Fig. 2g–j) while
Fx1, though decreasing in length, persists in holaspid stages
in the form of a strong tubercle (e.g. Fig. 2r); likewise,
P1 shortens, representing no more than a tubercle in the
adults; the second lateral marginal spine visible on smallest
specimens rapidly vanishes; posterior border spine decreases
in length but persists in the form of a tubercle in largest
holaspides, and an additional small tubercle appears on the
inner third (tr.) of the posterior border in late ontogeny; the six
anterior border spines shorten and become more forwardly
directed; two small marginal spines appear below the median
pair of major border spines in late meraspid stages (Fig. 2t),
then they shorten while another tiny marginal spine appears
on both sides in largest holaspides (Fig. 2s, u); numerous
coarse tubercles appear on the glabella in late ontogeny while
some rare ones appear on the fixigena near γand along the
preglabellar furrow.
The smallest librigena found (Fig. 3a) exhibits the
following features: large kidney-shaped eye; librigenal field
especially narrow (tr.) and poorly separated from a lateral
border of equal width (tr.) by a break in slope; genal spine
robust, rather long, and curved inwards and backwards;
posterior border short (tr.) but wide (exs.), poorly separated

64 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
from genal field by faint and shallow posterior border
furrow. Doublure bearing a single terrace ridge that separates
horizontal abaxial third from almost vertical, adaxial two-
thirds. In lateral view, eye high and lateral border slightly
inflated representing respectively about 50 % and 40 % of
the maximum height of the librigena. Sculpture: two rows
of spines occur on the lateral border. First row composed of
four robust and long spines (numbered Bd 1–4 forwards),
projecting dorsally and laterally. Second row composed of
seven long (numbered Blm1–7 forwards) and four short
(numbered Bsm1–4 forwards) marginal spines, projecting
ventrally and laterally; Blm1 and Blm2 located between
respectively genal spine/Bd1 and Bd1/Bd2 in dorsal view;
Blm3, Blm4, and Blm5 located opposite respectively Bd2,
Bd3 and Bd4 ventrally; Bsm1, Bsm2, Bsm3 and Bsm4
intercalated between respectively Blm1/Blm2, Blm2/Blm3,
Blm3/Blm4 and Blm4/Blm5; Blm6 and slightly shorter Blm7
located near respectively βand αturning points of the facial
suture. First and second rows are prolonged on the genal spine
by respectively two dorsal (numbered Gd1–2 backwards) and
one marginal (Gm1) spines.
The following ontogenetic changes can be described in
subsequent stages (Fig. 3b–k): eye widens (tr.), becoming
hemi-discoid in dorsal view (Fig. 3e); librigenal field
significantly broadens, representing about 50 % of the
maximum width (tr.) of the librigena in adults; lateral border
furrow rapidly differentiates, then deepens, remaining large
throughout ontogeny; genal spine significantly increases in
length until early holaspid period (Fig. 3b, e), somewhat
shortens thereafter (Fig. 3i); posterior border furrow deepens
moderately and widens; posterior border slightly widens
(exs.). In lateral view (Fig. 3k), eye becomes higher than
wide; librigenal field strongly elevates, reaching about 40 %
of the maximum height of the librigena in holaspides; lateral
border moderately inflates. Changes affecting sculpture are:
Bd1 migrates backwards (e.g. Figs 3b, c, 5c), thus being
located opposite Blm1 dorsally and separated from Bd2 by a
distance almost equal to twice the distance between Bd2/Bd3
or Bd3/Bd4 (Figs 3g, 5c); Blm2 located opposite middle
distance between Bd1/Bd2, having no corresponding spine
on the dorsal side of the border (e.g. Figs 3c, 5c); Bd1–4
and Blm1–7 initially lengthen in early ontogeny (Figs 3b–
d, 5c) and shorten thereafter (Fig. 3e–g); Bsm1–4 shorten
in late ontogeny; a third row composed of numerous tiny
spines appears in late growth stages below the second row
(Fig. 3j, k); Gd1 and Gd2 rapidly shorten, representing no
more than large tubercles when two additional tubercles
(Gd3–4) appear behind Gd2, then Gd1–4 regress until they
cannot be distinguished from the numerous small tubercles
that appear on the genal spine in late ontogeny; likewise,
Gm2 rapidly appears behind Gm1 (Fig. 5c), both shorten in
late growth stages until they can no more be differentiated
from the newly formed tubercles, which cover the holaspid
genal spine; coarse tubercles appear on the librigenal field
in late ontogeny, initially around the eye only, subsequently
spreading more and more outwards until covering the
entire librigenal field, with the exception of a narrow
area along the lateral border furrow where diverticulae
appear.
Otarionine hypostomes closely resemble each other in our
sample. However, some of them seem to display relatively
longer posterior spines for a given size-class (Fig. 3l–
n). This morphotype is tentatively assigned to Otarionella
rastrum sp. nov. because its relative abundance corresponds
to that of other sclerites of this species. Shape changes
affecting this hypostome during ontogeny are: anterior
part significantly widens (tr.), narrow lateral notches and
shoulders differentiate, posterior spines approach each other,
and posterior border broadens (sag. and exs.) at the expense
of the posterior lobe of the middle body.
Our sample also contains many juvenile thoracic segments
of otarionines. Some of them consistently bear a pair of
short spines near the posterior margin of the axial ring and
a pair of longer spines on the pleurae (Fig. 3o–s), whereas
others never display such structures. A similar spine/tubercle
pattern can be observed both on the occipital segment and on
segments of late meraspid to holaspid pygidia of O. rastrum
sp. nov. (e.g. Fig. 3y). Consequently, we consider that the
spiny thoracic segments belong to this species, whereas
the others probably belong to an undetermined species of
Cyphaspis. This assignment is also supported by the fact that
these spines are retained in the form of small tubercles on the
holaspid thorax of O. chamaeleo (see Fig. 4c). As the size
of thoracic segments varies along the antero-posterior axis
of a single individual, it is difficult to determine whether a
size difference between two isolated segments results from
a different position within the transitory thorax or from the
fact that they represent two distinct growth stages. In all
cases, shape changes affecting thoracic segments seem to be
minor.
No transitory pygidium corresponding to meraspid de-
grees 0 and 1 can be identified in our sample. However,
meraspid degrees 2, 3 and 4 are represented by specimens
that we confidently assign to Otarionella rastrum sp. nov.,
with regards to spine patterns. These meraspid degrees are
identified using axial spines on the second, fourth and sixth
future thoracic segments as markers. No transitory pygidium
corresponding to meraspid degree 5 (a specimen with a
single axial spine on the anteriormost segment) has been
found in our sample. Larger specimens, lacking axial spines,
cannot be attributed to particular meraspid degrees and, as a
consequence, are not described individually. The transitory
pygidium of meraspid degree 2 is slightly larger than the
protopygidium (Fig. 3t). It can be identified by the fact
that the first axial ring is smooth while the second and the
fourth bear axial spines. Accordingly, its four axial rings
may represent future thoracic segments 3 to 6. Four pairs of
pleural spines, corresponding to these segments, occur on
both sides, followed by a single pleural spine that probably
represents a fifth segment undifferentiated on the axis. The
transitory pygidium of meraspid degree 3 is slightly larger but
displays only three axial rings (Fig. 3u). The two axial spines
are located on the first and the third segments, indicating that
one segment has been released into the thorax. Consequently,
the axial rings may represent future thoracic segments 4 to
6. Three pairs of spines are present on the corresponding
pleurae. These are followed rearwards by an additional pair
of pleural spines, and further by a single spine, which
indicates that two additional segments are present at this
stage, though undifferentiated on the axis. A similar spine
pattern can be observed in slightly larger specimens with
more developed pleural spines (Fig. 3v), which indicates that
a certain variation already exists among the transitory pygidia
representing meraspid degree 3. The transitory pygidium of
meraspid degree 4 (Fig. 3w) is characterized by a single
axial spine located on the second of five axial rings (future
thoracic segments 5 to 9). Five corresponding pairs of pleural
spines occur on both sides, followed by a single additional
spine.
From meraspid degree 4 transitory pygidia to holaspid
pygidia (Fig. 3w–z), the axis shortens (sag.) and significantly
widens (tr.). The outer two-thirds of the pleural field flex
strongly downwards, which leads to an important heightening
of the pleural field and consequently of the entire pygidium

Ontogeny and systematics of Otarionella 65
Figure 6. Otarionella lkomalii sp. nov., early Eifelian, El Otfal Formation, Jbel Zireg region, south side of Ma’der basin, Anti-Atlas,
Morocco. All figures are digital photographs. Scale bars 2.5 mm. (a–f) holotype, UA11821; (a) dorsal view; (b) left lateral view; (c)
right lateral view; (d) posterior view; (e) antero-dorsal view; (f) anterior view.
in lateral view (Fig. 3cc). Sculpture: axial rings of newly
formed segments bear a pair of tubercles that progressively
reduce in late ontogeny; likewise, paired pleural spines are
progressively replaced by paired tubercles that regress in
latest stages; small tubercles appear along the posterior
margin of the posteriormost axial rings and on the outer
pleural fields of the largest specimens.
Otarionella lkomalii sp. nov.
Figure 6a–f

66 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
Material. A single complete articulated specimen. Other
specimens of this rare species from the same locality have
been seen by one of the authors (BDEC) in the hands of
commercial dealers in Morocco, but were unavailable for
study.
Etymology. This species is named for Adi Lkomali, a Berber
trilobite collector of southern Morocco.
Type locality and horizon. The type locality is located near
Jbel Zireg (N 30◦36′41.6; W 04◦32′22.7) at the southern
end of the Maider Basin, in the Anti-Atlas of southeastern
Morocco. The trilobite was collected from a bed that is 28 cm
thick, composed of limestone (moderately resistant micritic
mudstone to wackestone). This bed is early Eifelian in age,
and should probably be assigned to the El Otfal Formation
of Hollard (1974).
Holotype. Complete, articulated specimen UA11821, Figure
6a–f.
Diagnosis. Glabella short, ovoid, moderately inflated, with
two pairs of prominent spinose tubercles in anterior half of
median lobe (G2–3); occipital spine comparatively stout and
prominent, very slightly curved back distally; preglabellar
field short, only about as long (sag.) as anterior border; L1
lobes are comparatively large, strongly inflated and rounded
anteriorly so as to be bluntly ovoid or rounded orthogonal in
outline; eyes are small and slightly stalked dorsolaterally
so as to overhang upper parts of genal fields; librigenae
with genal spines only very slightly curved, and distinctly
shorter than genal fields, and with four prominent distally
directed marginal spines (Bd1–4), several secondary spines
(number not certain but two most posterior ones are most
prominent; Blm); pygidium moderately convex, with axis
with four to five rings plus terminal piece; sculpture on thorax
and pygidium of comparatively low, suppressed tubercles,
mainly on axis; sculpture on cephalon of numerous small- to
medium-sized tubercles, and fine caeca-related pits on genal
regions; prominent slightly backward curved axial spines
present on fourth and sixth thoracic segments, with more
posterior spine being 50 % longer than more anterior form,
which in turn is distinctly longer than occipital spine.
Description. Glabella middle lobe egg-shaped (length/width
ratio of holotype: 1.17 in dorsal view); widest opposite or
just behind γ, steadily converging behind, broadly rounded
at back, moderately convex dorsally in lateral view, with
maximum height slightly behind δ, curving down forward
and backward, overhanging preglabellar field when back of
occipital ring in vertical orientation, provided with two pairs
of prominent tubercles (G2–3), G2 located near maximum
height of lobe (opposite or in front of δ, depending on
orientation of specimen) and G3 some distance further
forward on anterior slope of lobe; front part of S1 very
deep, back half firmly impressed, but shallower and wider
(tr.); S2 not discernible; axial furrows broad and deep,
slightly divergent rearwards, overhung by glabella in most
regions except for opposite anterior ends of S1 and opposite
occipital ring; preglabellar field narrow (sag.), about same
width as anterior border, and slightly shorter than occipital
ring, appears convex in lateral profile, with broadly anteriorly
convex row of tubercles; border furrow distinct but not deep,
width appears altered adjacent to some of large marginal
spines on anterior border of cranidium; anterior border
of cranidium subhorizontal in profile, moderately convex
forward, with six large marginal spines projecting forward,
evenly arched in anterior view, sharply raised against border
furrow medially but not laterally; lower part of anterior border
with small ridge and some subdued ventrodistally directed
tubercles; occipital furrow comparatively wide (sag., exs.),
wider distally (adjacent to inner margin of L1) than medially,
narrower and deeper behind L1, and merging with axial and
equally deep, transverse posterior border furrows; occipital
ring about as wide (sag.) as occipital furrow medially but
narrowing slightly laterally, extending laterally out to behind
about half width (tr.) of L1 lobes, moderately vaulted (sag.,
exs.), carrying a stout posterodorsally and very slightly
backward curved occipital spine that is shorter (sag.) than
L1, and sculpture of variable sized tubercles on rest of ring;
fixigenae between glabella and palpebral lobe curve down
toward axial furrow, and slightly wider (tr.) than L1 lobes,
arched both transversely and front to back, with sculpture
of variable sized tubercles, and without any of tubercles
being particularly prominent (no Fx1 discernible); anterior
portions of facial suture straight and run approximately
exsagittally; posterior branches of facial suture subparallel
to slightly posteriorly divergent in anterior half and more
posterolaterally directed further back; palpebral lobe small,
upraised with a proximal tubercle and more distal pit;
posterior border semicylindrical in section, slightly flexed
backward and slightly wider (exs.) distally.
Librigena with only very slightly inward curved genal
spine that is distinctly shorter (exs.) than the rest of the
cheek; librigenal field only slightly convex, and steeply
inclined, carrying variable sized tubercles on raised areas,
with small, shallow pits between, subtle caecal pattern may
be discerned among pits and tubercles, tubercles not arranged
in rows parallel with border; eye ovoid, upraised, extends
forwards and outwards relative to librigenal field; moderately
impressed lateral border furrow at angular junction between
librigenal field and border, more impressed in anterior half
of cheek than near anterior portion of facial suture, only
very slightly shallower across bridge-like swelling in front
of genal field; posterior border furrow distinctly shallower
across sutural ridge near genal angle, moderately to firmly
impressed elsewhere; lateral border robust, carrying four
prominent outward directed major spines (Bd1–4), and below
them several more ventrally directed spines (Blm), with the
more posterior of these spines being distinctly larger than
those further forward.
Thorax with ten segments. Prominent axial spines occur
on fourth and sixth thoracic segments, with that on the fourth
segment being about same diameter and twice the length of
occipital spine, and two-thirds length and diameter of that on
sixth segment, with both spines posterodorsally directed and
slightly curved backward distally; in dorsal view, thorax is
slightly barrel shaped, with maximum width across fourth
or fifth segments, and posteriormost segments distinctly
narrower (tr.) than anteriormost segments; sculpture of
subdued tubercles on axial rings and posterior pleural ribs;
distinct, firmly impressed pleural furrows run outward near
middle length of pleural regions of each segment to die out
a short distance from the distal tips of the segments; axial
rings form about 0.41–0.43 of width of thorax.
Pygidium with broad, parabolic posterior outline, and
length width ratio of about 0.435 (articulating half-ring not
included), and width of pygidial axis over width of pygidium
about 0.42; pygidial axis is high, slightly flat-topped, evenly
arched from front to rear in side view, with 5+1axial
rings, with the anterior two to three rings being distinctly
more inflated and clearly separated by transverse, complete
inter-ring furrows that become distinctly shallower from
front to rear, remnant of articulating half ring developed

Ontogeny and systematics of Otarionella 67
on second ring (in back of first ring); axial furrows curve
inward slightly backward and are distinctly deeper near
front of pygidium than where they become inconspicuous
at back of axis; fulcrum along anterior margin appears to be
almost half distance from axial furrow to lateral margin of
pygidium; but sharp change in slope, corresponding to fulcral
line only about one-third way across pleurae; three pleurae
are differentiated into narrower anterior bands and broader
and higher posterior bands by distinct pleural furrows that
disappear about two-thirds way across pleurae; interpleural
furrows are weaker and narrower than pleural furrows, and
anterior ones may be discernible slightly more distally than
pleural furrows; border only apparent through absence of
distinct furrows; sculpture is not preserved on holotype
(perhaps because of abrasive mode of preparation?).
Comparisons. This species is contrasted with Otarionella
rastrum sp. nov. above, under that species. None of the three
species from Morocco assigned to Otarionella by Alberti
(1967, 1969), Otarion (Otarionella) magnificum Alberti,
1967, O. (Otarionella) sidiarounium Alberti, 1969, and O.
(Otarionella) tafilaltense Alberti, 1967, are assigned to this
genus herein. All of these species, known only from cephalic
material (largely cranidia), can be readily distinguished from
Otarionella lkomalii sp. nov. on the basis of numerous
characteristics, involving the sculpture, size and shape of the
glabellar lobes; details of the fixigenae, patterns and numbers
of coarse tubercles, size and shape of the occipital spine, and
size and orientation of the preglabellar field. Otarionella
bensaidi Alberti, 1983, from beds containing Nowakia
sulcata at Hamar Laghdad in southeastern Morocco, is only
assigned with question to Otarionella herein. This species
is known only from its cranidium. However, even with so
little material available, O.?bensaidi can be distinguished
from O. lkomalii by numerous features, including: a much
less inflated frontal glabellar lobe, less distinct G2, smaller,
more ovate L1, greater number of tubercles along the anterior
margin, and a narrower (sag.) occipital furrow. Thus, these
two species do not appear to be closely related.
4. Discussion
According to Adrain & Chatterton (1994), two lines of
arguments suggest that Otarionella should be regarded
as a subjective junior synonym of Otarion: (1) the
original concept of Otarionella Weyer, 1965, including
any otarionines with prominent cephalic border spines,
cannot be regarded as a monophyletic unit, and (2)
the spinose adult morphology, diagnostic of the genus
Otarionella, represents no more than a paedomorphic
variant of the typical morphology of Otarion. While we
agree with those authors concerning the polyphyletic
status of the original concept of Otarionella,we
reject their assumption that most species formerly
grouped within this genus, especially the type species
Otarionella davidsoni (Barrande, 1852), are simple
paedomorphic forms of Otarion. By contrast, we
believe that not only Otarionella (as redefined in
Section 3) is distinct from Otarion but also that it has
probably not evolved from this latter genus. This view
is supported by both juvenile and adult characteristics
that are discussed separately below.
4.a. Cranidial spine patterns in the early growth stages
The pattern of cranidial spine distribution in mer-
aspides of Otarion comprises a single pair of palpebral
spines (P1), predominant fixigenal spines Fx1 and Fx4
(Fx2 and Fx3, when present, are smaller and rapidly
vanish during early meraspid period), crowded and
anteriorly placed glabellar pairs of spines G2 and G3,
and two rows of cephalic border spines (Adrain &
Chatterton, 1994). A virtually identical cephalic spine
pattern can be observed in meraspides of Cyphaspis
(Adrain & Chatterton, 1994, 1995; see Figs 5a and 7b,
herein), which led Adrain & Chatterton (1994) to group
Cyphaspis,Otarion and two younger genera (Namuro-
pyge Richter & Richter, 1939 and ?Dixiphopyge
Brezinski, 1988) within the tribe Otarionini Richter
& Richter, 1926. The distribution of cephalic spines in
early growth stages of Otarionella, as exemplified by
Otarionella rastrum sp. nov., differs in several major
aspects from that of Otarion (Figs 2f, g, 5b). Although
three pairs of spines occur on the juvenile glabella, they
are evenly spaced and G1 is positioned far posterior to
glabellar middle length (sag.). Moreover, Fx2 and Fx3,
though shorter than Fx1, are strong in early meraspid
stages, whereas Fx4 never develops during ontogeny
(Fig. 5b). On the other hand, cephalic spine patterns in
Otarionella and Otarion have two features in common:
a single prominent palpebral spine (P1) and two rows of
cephalic border spines. This latter similarity, however,
proves to be somewhat superficial when examined in
detail. In Otarion and Cyphaspis, the dorsal row is
probably composed of six spines in the earliest growth
stages (Fig. 7b), but a seventh spine rapidly appears
sagittally (e.g. Fig. 7c, herein; figs 1.3, 7.1 in Adrain
& Chatterton, 1994; fig. 2.1–3 in Adrain & Chatterton,
1996), sometimes leading to a rapprochement of the
two most abaxially located spines (e.g. figs 1.40, 1.47,
2.1, 2.11 in Adrain & Chatterton, 1996). In Otarionella,
a seventh spine never develops and the dorsal row
is comprised of six strong and evenly spaced spines
throughout ontogeny. Moreover, the second row is
composed of only two small spines in early meraspides
of Otarionella (Fig. 2t), and it is only later that an
additional small spine develops on both sides (Fig. 2s).
Each of these four small spines corresponds anteriorly
to one of the four adaxial spines of the first row. In
Otarion and Cyphaspis, this second row comprises
more spines (up to seven on our specimens; Fig. 7d),
with some of them corresponding to spines of the first
row and others being somewhat intercalated between
them (Fig. 6b–d; see also figs 7.1, 9.3, 9.4 in Adrain
& Chatterton, 1994). In addition, this organization into
two rows tends to disappear in Otarion (e.g. figs 9.1,
9.2, 9.5 in Adrain & Chatterton, 1994) and Cyphaspis
(e.g. figs 1.40, 2.9, 2.10 or 5.8 in Adrain & Chatterton,
1996), while border spines shorten during ontogeny,
whereas it remains unchanged probably as late as the
holaspid period in Otarionella (e.g. Fig. 2s).

68 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
Figure 7. Cyphaspis sp., early to late Emsian, middle member of the Bissounel Formation, Bissounel Peak, Montagne Noire, France.
All figures are scanning electron micrographs of silicified specimens in dorsal views. Scale bars 0.25 mm. (a) Metaprotaspis (note
the four fixigenal tubercles), UMC-IP539. (b–d) Meraspid cranidia; (b) small specimen with six major border spines, strong Fx4, and
grouped G2/G3, UMC-IP540; (c) small specimen with seven major border spines, UMC-IP541; (d) large specimen with Fx2 and Fx3
lost and numerous glabellar tubercles, UMC-IP542.
To summarize, Otarionella and Otarion–Cyphaspis
show significant differences in patterns of juvenile
cranidial spine distribution. These dissimilarities are so
important that Otarionella fails to display three of the
five diagnostic characters of the tribe Otarionini (Fx2
and Fx3 suppressed, G2 and G3 crowded and toward
anterior glabella, and G1 positioned just posterior to
glabellar sagittal middle length in early meraspides). In
addition, the two rows of cephalic border spines differ
in the two groups (number of spines involved, spine
distributions, ontogenetic changes) and accordingly
their occurrence cannot reasonably be considered as
a shared character. Thus, it seems difficult to consider
Otarionella a simple paedomorphic form of Otarion,
since it implies that three, possibly four, of the
five juvenile features, so far considered sufficiently
constant to be diagnostic of the tribe Otarionini,
have evolved to such a degree that they can no
more be observed in this taxon. Moreover, even if
a spinose morphology in adults may be generally
regarded as a paedomorphic trait in the Otarioninae,
the differences between cephalic spine patterns suggest
that an origin of Otarionella from Otarion would have
implied complex evolutionary processes rather than
simple paedomorphosis. This is also indicated by the
differences between the metaprotaspides of Otarionella
and Cyphaspis.InOtarionella rastrum sp. nov., the
protocranidium displays a complex pattern of strong
spines, which is already very similar to that of the
subsequent meraspid stages (Fig. 2a–e). By contrast,
the metaprotaspis of Cyphaspis possesses low tubercles
that, however, seem to already display an organized
distribution (Fig. 7a). The occurrence of four fixigenal
tubercles (Fx1–4) and the absence of cephalic border
spines in this latter metaprotaspis demonstrate that the
cephalic spine patterns of Cyphaspis and Otarionella
differ as early as the protaspid period. If Cyphaspis is
considered as having had a paedomorphic origin from
Otarion, it seems unlikely that this latter would display
stronger and differently distributed cephalic tubercles
in metaprotaspid stages.
Lastly, considering patterns of meraspid cranidial
spine distribution alone, there are no indications of
Otarionella being phylogenetically closer to Otarion,
and more generally to the tribe Otarionini, than to other
otarionines such as Harpidella M’Coy, 1849 and Maur-
otarion Alberti, 1969. Indeed, Adrain & Chatterton
(1994) pointed out that these latter genera show a
similar cephalic spine pattern in early meraspides that
can be described as follows: two palpebral spines (P1–
2), four major fixigenal spines (Fx1–4), three evenly
spaced pairs of glabellar spines (G1–3) and a single row
of cephalic border spines. To facilitate comparisons, the
characteristics of the juvenile cephalic spine pattern of
Otarionella rastrum sp. nov. and those of the three
patterns identified by Adrain & Chatterton (1994) are
summarized in Table 1. Features such as three pairs of
evenly spaced glabellar spines, with G1 far posterior
to middle length (sag.) of the glabella, are shared by
Otarionella, Harpidella and Maurotarion. On the other
hand, Otarionella and the Otarionini possess a single
palpebral spine and two rows of cephalic border spines,
whereas Harpidella and Maurotarion have two palpeb-
ral spines and a single row of cephalic border spines.
As shown above, the two rows of cephalic border spines
in Otarionella and the Otarionini differ significantly in
terms of number of spines, organization and ontogen-
etic evolution, and accordingly, they cannot reasonably
be considered as homologous in the two groups. At
this stage of comparison, it could be stated that the
Otarionella pattern is somewhat intermediate between
the Harpidella–Maurotarion and the Otarionini
patterns. The absence of Fx4, however, demonstrates
that the Otarionella pattern also possesses its own char-
acteristics, suggesting that it might have undergone, to
some extent, independent evolution.
It follows from these comparisons that it is very
unlikely that the cephalic spine pattern observed in

Ontogeny and systematics of Otarionella 69
Table 1. Characteristics of cranidial spine patterns in otarionine meraspides
Character Beggaspis pattern
Harpidella–Maurotarion
pattern Otarionella pattern Otarionini pattern
Glabellar spines Not paired 3 pairs 3 pairs 3 pairs
Evenly spaced Evenly spaced G2 and G3 crowded,
anteriorly positioned
G1 posterior to glabellar
midlength (sag.)
G1 posterior to glabellar
midlength (sag.)
G1 near glabellar
midlength (sag.)
Palpebral spine(s) 2 2 1 1
Fixigenal spines Fx1–4 Fx1–4 Fx1–3 Fx1 and Fx4
Border spines 1 row 1 row 2 rows 2 rows∗
Abbreviations used: Fx – major fixigenal spine; G – glabellar spine; sag. – sagittally.
∗Number of spines composing these two rows and their location, however, differ from that of Otarionella (see text).
Otarionella is derived from that of the Otarionini
and, all the more, that representatives of Otarionella
represent simple paedomorphic forms of Otarion.
Indeed, this would imply complex, unparsimonious
evolution, involving the secondary loss of the peculiar
organization of glabellar spines of the Otarionini, the
reappearance of well-developed Fx2 and Fx3, and
the disappearance of the fourth fixigenal spine (Fx4),
which is steadily predominant in meraspid cranidia of
Otarionini. In our opinion, it seems more parsimonious
to infer that the shared characters of the cephalic spine
patterns of Otarionella and the Otarionini result from
a common origin of the two clades (that is, they are
plesiomorphic). Indeed, it can be speculated that both
groups differentiated from an unknown ancestor with
four fixigenal spines and three pairs of evenly spaced
glabellar spines as in Harpidella and Maurotarion,but
with one palpebral spine already lost and possibly a
second row of border spines already acquired. Later,
Fx4 might have been lost in the Otarionella lineage,
while the primitive Otarionini acquired a different
distribution of the glabellar spines, and lost Fx2 and
Fx3, the two rows of cephalic border spines evolving
independently in the two lineages.
4.b. Evidence from adult morphology
Besides its particular pattern of cranidial spine dis-
tribution in meraspides, Otarionella is characterized
by a unique association of adult features that clearly
differentiates this taxon from both Otarion and
Cyphaspis. This unique combination of adult characters
comprises two, sometimes three, evenly spaced pairs
of glabellar spines, an occipital median spine, a strong
posterior fixigenal tubercle (Fx4) (which is not visible
on the unique specimen of Otarionella lkomalii sp.
nov.), a single row of tubercles around the front of the
glabella, and six strong and evenly spaced cranidial
border spines on a prominent crest. In addition, four
strong spines (Bd) are initially inserted dorsally on
the librigenal border. As exemplified by O. chamaeleo
(Basse, 1997; Fig. 4a–c) and Otarionella lkomalii sp.
nov. (Fig. 6a–f), Otarionella also differs from all other
otarionines by a restricted number (10) of thoracic
segments, among which the fourth and the sixth bear a
sharp and long axial spine (a shorter spine also occurs
on the second thoracic segment in O. chamaeleo).
Lastly, the pygidium of Otarionella is small, with an
axis composed of three to five axial rings, at least
as large (tr.) as the pleural fields, and merging with
the postaxial field. Many of these characteristic traits
concern sculptural features. However, most of them
develop as early as the metaprotaspid period in O.
rastrum sp. nov. (see Section 3) and accordingly, they
may represent genetically fixed characters. Also, we
consider that their persistence in the adults of several
species justifies their use as diagnostic characters.
Besides adult spinosity, the morphology of Otari-
onella differs significantly from that of Otarion. This
is particularly obvious when the type species of the
two genera, Otarionella davidsoni (Barrande, 1852)
and Otarion diffractum Zenker, 1833, are compared. In
many aspects, Otarionella and particularly Otarionella
davidsoni is morphologically much closer to Cyphaspis
and its type species Cyphaspis ceratophthalma
(Goldfuss, 1843) than to Otarion diffractum. Unlike
this latter, it indeed displays a strongly inflated glabellar
middle lobe overhanging the short preglabellar field in
life position, strongly protruding and somewhat stalked
eyes, a reduced number of thoracic segments, and a
relatively narrow (tr.) pygidium with few axial rings.
This gross similarity could be attributed to the fact
that both genera are supposed to have a paedomorphic
origin (Adrain & Chatterton, 1994, 1996). However, the
inflated glabella, overhanging the preglabellar field, is
a typical peramorphic trait not only in the Otarioninae
but also in the Proetida as a whole. This suggests that if
similar heterochronic processes have been involved in
the origin of these two genera, they were not restricted
to paedomorphosis. In all cases, differences between
patterns of juvenile cranidial spine distribution (see
Section 4.a) demonstrate that the similarities between
Otarionella and Cyphaspis are more likely the result of
a parallel evolution than that of a common origin of the
two taxa from Otarion. Thus, the adult morphology, like
ontogenetic data, is not consistent with a close relation-
ship between Otarionella and Otarion and a fortiori,
with a proposed synonymy between the two genera.

70 R. LEROSEY-AUBRIL, R. FEIST & B. D. E. CHATTERTON
5. Conclusion
A precocious development, a well-organized distri-
bution, and a relative scarcity within clades are all
criteria indicating that a sculptural feature may be worth
considering for systematic purposes. These criteria,
to which we can add visibility for practical reasons,
represent no more than the criteria typically used to
test the potential utility of any morphological character
in systematics. Thus, there are no convincing reasons to
preclude the use of sculptural features in systematics,
especially when they represent abundant discrete
characters like the cephalic tubercles of Otarioninae.
Data currently available on the ontogeny of the
Otarioninae are still too scarce to depict, even grossly,
the evolution of cephalic spine patterns in the clade
as a whole. However, they appear already sufficient
to definitively reject a synonymy of Otarionella and
Otarion.
Acknowledgements. The authors are indebted to Martin
Basse, Bochum, who sent latex casts of the original
material of O. chamaeleo (Basse, 1997), including the so-
far undescribed external mould of the holotype that shows
thoracic axial spines. R. M. Owens and an anonymous
referee are thanked for their helpful suggestions. Chatterton
acknowledges financial support from a Natural Sciences
and Engineering Research Council of Canada discovery
grant. This is a contribution of the Institut des Sciences de
l’Evolution, UMR 5554 CNRS (ISEM 2006–071) and of the
Laboratoire Magmas et Volcans, UMR 6524 CNRS.
References
ADRAIN,J.M.&CHATTERTON, B. D. E. 1994. The
aulacopleurid trilobite Otarion, with new species from
the Silurian of Northwestern Canada. Journal of
Paleontology 68, 305–23.
ADRAIN,J.M.&CHATTERTON, B. D. E. 1995. The otarionine
trilobites Harpidella and Maurotarion, with species
from Northwestern Canada, the United States, and
Australia. Journal of Paleontology 69, 307–26.
ADRAIN,J.M.&CHATTERTON, B. D. E. 1996. The otarionine
trilobite Cyphaspis, with new species from the Silurian
of Northwestern Canada. Journal of Paleontology 70,
100–10.
ALBERTI, G. K. B. 1967. Neue obersilurische sowie unter-
und mitteldevonische Trilobiten aus Marokko, Deutsch-
land und einigen anderen europ¨
aischen Gebieten. 2.
Senckenbergiana lethaea 48, 481–509.
ALBERTI, G. K. B. 1969. Trilobiten des j¨
ungeren Siluriums
sowie des Unter- und Mitteldevons. I. Mit Beitr¨
agen zur
Silur-Devon-Stratigraphie einiger Gebiete Marokkos
und Oberfrankens. Abhandlungen der Senckenbergis-
chen naturforschenden Gesellschaft 520, 1–692.
ALBERTI, G. K. B. 1970. Trilobiten des j¨
ungeren Siluriums
sowie des Unter- und Mitteldevons. II. Abhandlungen
der Senckenbergischen naturforschenden Gesellschaft
525, 1–233.
ALBERTI, G. K. B. 1983. Trilobiten des j¨
ungeren Siluriums
sowie des Unter- und Mitteldevons. IV. Senckenbergi-
ana lethaea 64, 1–87.
ANGELIN, N. P. 1854. Palaeontologia Scandinavica. I.
Crustacea formationis transitionis. Fasc. 2, I–IX, 21–
92, Lund.
BARRANDE, J. 1852. Syst`
emeSilurienducentredelaBohˆ
eme.
Recherches pal´
eontologiques. I. Crustac´
es, Trilobites.
Prague and Paris: 935 pp.
BARRANDE, J. 1872. Syst`
eme Silurien du centre de la
Bohˆ
eme. I `
ere partie. Recherches pal´
eontologiques. I.
Suppl´
ements, Trilobites. Prague and Paris: 647 pp.
BASSE, M. 1997. Trilobiten aus mittlerem Devon des
Rhenohercynicums: II. Proetida (2), Ptychopariida,
Phacopida (1). Palaeontographica (A) 246, 53–142.
BIGEY,F.&FEIST, R. 1976. Cryptostomata (Bryozoaires)
des ‘Calcaires `
a polypiers siliceux’ (D´
evonien inf´
erieur
de la Montagne Noire, France m´
eridionale): note
pr´
eliminaire. Documents du Laboratoire de Geologie
de la Facult´
e des Sciences de Lyon, ‘Bryozoa 1974’ 2,
257–71.
BREZINSKI, D. K. 1988. Revision and redescription of
some Lower Mississippian trilobites from the Chouteau
Formation (Kinderhookian) of central Missouri. Journal
of Paleontology 62, 103–10.
BURMEISTER, H. 1843. Die Organisation der Trilobiten,
aus ihren lebenden Verwandten entwickelt; nebst einer
systematischen ¨
Ubersicht aller seither beschriebenen
Arten. Berlin: Reimer, 147 pp.
CHATTERTON,B.D.E.,JOHNSON,B.D.&CAMPBELL,
K. S. W. 1979. Silicified Lower Devonian trilobites from
New South Wales. Palaeontology 22, 799–837.
COOPER,G.A.&WILLIAMS, J. S. 1935. Tully Formation of
New York. Bulletin of the Geological Society of America
46, 781–868.
ELLERMANN, I. 1992. Trilobiten aus dem Unterdevon der
Karnischen Alpen. Palaeontographica (A) 221, 1–62.
ERBEN, H. K. 1952. Trilobiten aus dem ¨
Alteren Hercyn
(Unterdevon) des Unterharzes. Neues Jahrbuch f¨
ur
Geologie und Pal¨
aontologie, Abhandlungen 94, 150–
362.
FEIST, R. 1970a.Breviscutellum (Meridioscutellum)n.sg.et
son d´
eveloppement larvaire. Geobios 4(3), 41–73.
FEIST, R. 1970b.Miseen´
evidence de l’Emsien inf´
erieur
(D´
evonien inf´
erieur) dans la Montagne Noire. Compte
Rendu Sommaire de la Soci´
et´
eG
´
eologique de France 6,
199.
FEIST, R. 1985. Devonian stratigraphy of the southeastern
Montagne Noire (France). Courier Forschungs-Institut
Senckenberg 75, 331–52.
FEIST,R.&GROOS-UFFENORDE, H. 1979. Die ‘Calcaires `
a
polypiers siliceux’ und ihre Ostracoden-Faunen (Oberes
Unter-Devon; Montagne Noire, S-Frankreich). Sencken-
bergiana lethaea 60, 83–187.
FEIST,R.,SCH ¨
ONLAUB,H.-P.&BULTYNCK, P. 1985. Faci`
es
et biostratigraphie (Conodontes) du passage D´
evonien
inf´
erieur-moyen dans la Montagne Noire (France).
Hercynica 1(2), 81–97.
FORTEY,R.A.&CLARKSON, E. N. K. 1976. The function
of the glabellar “tubercle” in Nileus and other trilobites.
Lethaia 9, 101–6.
FORTEY,R.A.&OWENS, R. M. 1975. Proetida – a new order
of trilobites. Fossils and Strata 4, 227–39.
GOLDFUSS, A. 1843. Systematische ¨
Ubersicht der Trilobiten
und Beschreibung einiger neuen Arten derselben. Neues
Jahrbuch fur Mineralogie (for 1843), 537–76.
HALL,J.&CLARKE, J. M. 1888. Trilobites and other
Crustacea of the Oriskany, Upper Helderberg, Hamilton,
Portage, Chemung and Catskill Groups. Geological

Ontogeny and systematics of Otarionella 71
Survey of the State of New York, Paleontology 7, I–LXIV,
1–236.
HAMMANN,W.&RABANO, I. 1987. Morphologie und
Lebensweise der Gattung Selenopeltis (Trilobita) und
ihre Vorkommen im Ordovizium von Spanien. Sencken-
bergiana lethaea 68, 91–137.
HOLLARD, H. 1974. Recherches sur la stratigraphie des
formations du D´
evonien moyen, de l’Emsien sup´
erieur
au Frasnien, dans le Sud du Tafilalt et dans le Ma’der
(Anti-Atlas oriental). Notes du Service G´
eologique du
Maroc 36 (264), 7–68.
HOLLARD, H. 1981. Tableaux de corr´
elations du Silurien et du
D´
evonien de l’Anti-Atlas. Notes du Service G´
eologique
du Maroc 42 (308), 1–23.
KAUFMANN, B. 1998. Facies, stratigraphy and diagenesis of
Middle Devonian reef- and mud-mounds in the Mader
(eastern Anti-Atlas, Morocco). Acta Geologica Polonica
48, 43–106.
LEROSEY-AUBRIL, R. 2007. Early Devonian calymenid larvae
(Trilobita) from the Bissounel Formation (Montagne
Noire, France). Bulletin de la Soci´
et´
eG
´
eologique de
France 178, 197–200.
L¨
UTKE, F. 1961. Das Alter des Lauterberger (Sch ¨
onauer)
Kalkes (Unterdevon) der Roth¨
auser Klippe bei Bad
Lauterberg (Harz). Neues Jahrbuch f¨
ur Geologie und
Pal ¨
aontologie, Monatshefte, 124–40.
L¨
UTKE, F. 1965. Zur Kenntnis herzynischer Trilobiten aus
dem Unter- und Mitteldevon des Harzes. Palaeonto-
graphica (A) 124, 151–236.
L¨
UTKE, F. 1980. Zur Evolution der altpal¨
aozoischen Proetina
(Trilobita). Senckenbergiana lethaea 61, 73–144.
M’COY, F. 1849. On the classification of some British fossil
Crustacea, with notices of new forms in the University
collection at Cambridge. Annals and Magazine of
Natural History,series2,4, 161–79, 330–5, 392–414.
PRANTL,F.&P
ˇ
RIBYL, A. 1950. Revise ˇ
celedi Otarionidae
R. & E. Richter, 1926 z ˇ
cesk´
eho siluru et devonu
(Trilobitae). Sborn´
ık ´
Ustredni ´
ustavu geologick´
y15,
353–512.
Pˇ
RIBYL, A. 1947. Two new Otarionidae from the Devonian
of Bohemia. Vˇ
estn´
ık kr´
alovsk´
eˇ
cesk´
e spoleˇ
cnosti nauk
1946, 1–12.
Pˇ
RIBYL,A.&VANˇ
EK, J. 1981. Studie zur Morphologie und
Phylogenie der Familie Otarionidae R. & E. Richter,
1926 (Trilobita). Palaeontographica (A) 173, 160–
208.
RICHTER,R.&RICHTER, E. 1926. Die Trilobiten des Ober-
devon. Beitr¨
age zur Kenntnis devonischer Trilobiten. IV.
Abhandlungen der preussischen geologischen Landes-
Anstalt 99, 1–314.
RICHTER,R.&RICHTER, E. 1939. ¨
Uber Namuropyge n. g.
und die Basisolution der Trilobiten-Glatze. Bulletin du
Mus´
ee Royal d’Histoire Naturelle de Belgique 15, 1–19.
SCHRAUT, G. 2000. Eine neue Otarion-Art (Trilobita, Arth-
ropoda) aus dem Greifensteiner Kalk (unteres Mittel-
Devon, Unter-Eifelium) von Greifenstein bei Herborn
(Hessen, Deutschland). Pal ¨
aontologische Zeitschrift 74,
305–16.
STØRMER, L. 1980. Sculpture and microstructure of the
exoskeleton in chasmopinid and phacopid trilobites.
Palaeontology 23, 237–71.
THOMAS,A.T.&OWENS, R. M. 1978. A review of the
trilobite family Aulacopleuridae. Palaeontology 21, 65–
81.
WEYER, D. 1965. Etroeungt im Morvan (Zentralfrankreich).
Mitteilungen des Zentralen Geologischen Instituts 1,
289–302.
WHITTINGTON, H. B. 1956a. Silicified Middle Ordovician
trilobites: the Odontopleuridae. Bulletin of the Museum
of Comparative Zoology at Harvard College 114 (5),
155–288.
WHITTINGTON, H. B. 1956b. Type and other species of
Odontopleuridae (Trilobita). Journal of Paleontology
30, 504–20.
WHITTINGTON,H.B.,CHATTERTON,B.D.E.,SPEYER,S.
E., FORTEY,R.A.,OWENS, R. M., CHANG,W.T.,DEAN,
W. T. , F ORTEY,R.A.,JELL,P.A.,LAURIE,J.R.,PALMER,
A. R., REPINA,L.N.,RUSHTON,A.W.A.,SHERGOLD,
J. H. , CLARKSON,E.N.K.,WILMOT,N.V.&KELLY,
S. R. A. 1997. Treatise on Invertebrate Paleontology,
Part O, Arthropoda 1, Trilobita, Revised (ed. R. L.
Kaessler). Boulder, Colorado: Geological Society of
America and University of Kansas Press.
WHITTINGTON,H.B.&EVITT, W. R. 1954. Silicified Middle
Ordovician trilobites. Geological Society of America,
Memoirs 59, 1–137.
WHITTINGTON,H.B.&WILMOT, N. V. 1997. Microstructure
and sculpture of the exoskeletal cuticle. In Treatise
on Invertebrate Paleontology, Part O, Arthropoda 1,
Trilobita, Revised (ed. R. L. Kaessler), pp. 74–84.
Boulder, Colorado: Geological Society of America and
University of Kansas Press.
WILMOT, N. V. 1991. Sensory field maps of proetide trilob-
ites. Transactions of the Royal Society of Edinburgh:
Earth Sciences 82, 183–93.
ZENKER, J. C. 1833. Beitr¨
age zur Naturgeschichte der
Urwelt. Organische Reste (Petrefacten) aus der Al-
tenburger Braunkohlen-Formation des Blankenburger
Quadersandstein, Jenaischen bunten Sandstein und
B¨
ohmischen ¨
Ubergangsgebirges. Jena: 67 pp.