Publi.complète - Musée national d'histoire naturelle

Delsate, Steur, Schneider, Thuy Lower to Middle Emsian flora and fauna from Consthum and Merkholtz
narrower. Many Devonian eurypterids were small
to middle size animals (Pagea reaches 60 cm), although
Lochkovian Pterygotus were still giant like
the Silurian ones.
Preserved positive material EIB147b in the continuation
of this specimen adds some interesting
details: 3 segments are longitudinally striated,
forming many closely adjacent tubercles (strongly
differing from the segment bosses of Willwerathia:
see Anderson et al. 1998). A scorpionid aribution
is discarded, because the distal scorpionid plates
are much longer than wide (Geys 1991).
Ferrantia • 36 / 2003
EIB148 a & b
A 30 mm plate ornamented by tubercles bears
millimetric triangular « thorns » (three are well
preserved) on the smoother distal part, and may
be aributed to a pterygotid claw fragment.
The counterpart EIB148b of this specimen provides
further ornamentation details: triangular
or lozenge shaped scales on the main part of the
claw.
Ostracoda Latreille, 1802
Some plurimillimetric specimens seem aributable
to Aparchitidae and Leperditellidae. Lippert
1939 reported Leperditia klerfia Mauz, from the
Clervaux Schists (E2) of Zweifelscheid (D).
Vertebrata
Subphylum Vertebrata Linnaeus, 1758
Class Pteraspidomorphi Goodrich, 1909
Subclass Heterostraci Lankester, 1868
Order Pteraspidiformes Berg, 1937
Family Psammosteidae Traquair, 1896
Genus indet.
EIB128 (Pl. 7, fig. 3 a,b)
This 75 x 45 mm preserved plate bears eroded tubercles;
it evokes a dorsal or ventral disk fragment
of an “Agnatha” Heterostracan Psammosteidae,
an identification that should be confirmed and
precised by the detailed study of EIB128 by Del-
sate & Blieck (work in progress).
Discussion
Among Psammosteiformes (sensu Benton 1993),
Drepanaspididae and Guerichosteidae are known
from the Emsian. This group is till now unknown
in the Luxembourg and Belgium Lower Devonian,
but the Psammosteiforme Drepanaspis exists
in the Praguian-Emsian of Cornwall-Devon
(UK) and the species Drepanaspis lipperti Gross
is reported (orbital, branchial, cornual, ventral,
dorsal, median and trunk plates, tail scales) from
the Clervaux Schists (Klerfer Schichten, E2) of
Zweifelscheid (Rhineland, D) near to the Grand
Duchy of Luxembourg, by Lippert 1939, together
with the placoderm Phlyctaenaspis sp (skull, spinal,
postero-ventral, postero-lateral, antero-lateral
and trunk plates) and Porolepis scales. It must be
emphasised that Phlyctaenaspis is a synonym of
Phlyctaenius, which is not considered a coccosteid
anymore, and that the Phlyctaenaspis reported by
Gross 1937 : 22-23 and Lippert 1939: 38 revealed
to be an Arthrodire Actinolepina? skull internal
mould (Blieck et al. 1998). Drepanaspis gemuendensis
Schlüter is reported from the Lower Devonian
of Gemünden in Hunsrück (see Bartels & Brassel,
1990).
It also bears some similarity with a ventral plate
of Brachythoraci, possibly Migmatocephala (an
alternative aribution would be a cranial plate of
Brachythoraci Eubrachythoraci : Phlyctaeniina cfr
Holonematidae ?). Antiarcha or Coccosteidae
seem less probable (Coccosteus is not known in the
Lower Devonian), but the Merkholtz discovery
reminds the Asselberghs 1913 and Bordet 1939
report of « Coccosteid plates » from the Schuttbourg
Quartzophyllade at the Schubourg castle,
bearing in mind that isolated bony plates of placoderm
morphology found at the beginning of the
last century were oen aributed to Coccosteus,
which was referred to as a model.
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