THE OPHIUROID AMPHIURA? PLANA IN BOHEMIAN CRETACEOUS BASIN 37
GEOLOGICA CARPATHICA, 55, 1, BRATISLAVA, FEBRUARY 2004
THE OPHIUROID AMPHIURA? PLANA IN NEARSHORE SETTINGS OF
THE BOHEMIAN CRETACEOUS BASIN
Smetanova 380, CZ-251 64 Mnichovice, Czech Republic
(Manuscript received September 24, 2002; accepted in revised form March 11, 2003)
Abstract: Comparatively common lateral arm plates from Turonian strata in the Czech Republic are assigned to the
amphiurid brittlestar species Amphiura? plana Kutscher et Jagt in Jagt, 2000, which is also known from the Campanian
and Maastrichtian of northern Germany, southern Sweden, Denmark, the Netherlands and Belgium. This species appears
to represent an evolutionarily conservative lineage with extensive paleogeographical and stratigraphic ranges, in excess
of 20 or 25 million years. The abundance of Amphiura? plana, based on lateral arm plates, amounts to about 5 % at
Velim, where three other species are commoner still.
Key words: CretaceousTuronian, Bohemian Cretaceous Basin, nearshore, evolutionary conservatism, Ophiuroidea.
Originally only the lateral arm plates of the present taxon (see
torc 1996) were known, which explains why its systematic
position was not quite clear. Recently, Jagt (2000a) and Kut-
scher & Jagt (in Jagt 2000), have recorded arm fragments pre-
serving spines as well as ventral arm plates, dissociated verte-
brae, dorsal arm plates, radial shields and possibly even other
skeletal elements from arms and disc. Those authors also shed
more light on the taxonomic position of the species. The
present study of the Upper Cretaceous material from the
Czech Republic furnishes additional data.
Stratigraphic and geographical settings
All remains of Amphiura? plana collected come from near-
shore depositional settings in the Bohemian Cretaceous Basin
(Czech Republic), at two localities (see Fig. 1) exposing near-
shore facies (Korycany Member of the Peruc-Korycany For-
mation (KM), Bílá hora Formation (BHF), Lower Turonian),
namely Velim pocket Václav (grey and greenish claystone,
KM, Whiteinella archaeocretacea Zone see Fig. 2), and
Kutná Hora-Kaòk (marls overlying conglomeratic limestone,
BHF). For details of localization and lithology see ítt (1992),
ítt et al. (1997a,b, 2001) and Fig. 2.
Material and methods
The material was collected by Jiøí ítt (Institute of Geology
ASCR, Prague) between the 1970s and 1990s and by the au-
thor in the 1990s. The Bohemian Cretaceous sediments were
washed and dissociated ophiuroid ossicles were handpicked.
On the whole, more than 170 ossicles of the present species
were found. Several dissociated lateral arm plates were co-
loured or photographed with the help of a scanning electron
microscope (SEM) at the Institute of Geology ASCR. The rel-
atively large number of lateral arm plates from Velim locality
also permitted a quantitative evaluation of the abundances of
individual ophiuroid species.
Class: Ophiuroidea Gray, 1840
Subclass: Ophiuridea Gray, 1840
Infraorder: Gnathophiurina Matsumoto, 1915
Superfamily: Gnathophiuridea Matsumoto, 1915
Family: Amphiuridae Ljungman, 1867
Genus: Amphiura Forbes, 1843
Type species: Amphiura chiajii Forbes, 1843
Amphiura? plana Kutscher et Jagt in Jagt, 2000
1996 type R torc, pp. 204210, figs. 84, 137141.
1998 sp. 14 = Amphiura? n. sp. 1 Jagt et Kutscher, fig. 2f.
1999 Amphiura? n.sp. Jagt, p. 200, pl. II, fig. 4.
2000 Amphiura? plana Kutscher et Jagt, sp.nov. Jagt (a), p. 21, pl.
10, fig. 11; pl. 11, fig. 1.
2000 Amphiura? plana Kutscher et Jagt in Jagt, pp. 7172, pl. 29,
figs. 15; pl. 33, fig. 3.
2002 Amphiura? plana Kutscher et Jagt in Jagt, 2000 torc, pp.
394397, figs. 196, 206210.
Type: Holotype is a lateral arm plate FGWG 112/17 (Col-
lections of Institut für geologische Wissenschaften, Ernst-
Moritz-Arndt Universität Greifswald, Germany) see Kut-
scher & Jagt (in Jagt 2000, pl. 29, fig. 2).
Type horizon and locality: White chalk facies of
the upper Lower Maastrichtian (Sumensis, Cimbrica and
Fastigata Zones), Rügen, NE Germany.
Material: 172 dissociated lateral arm plates (and proba-
bly also a few rare vertebrae) from Velim pocket Václav
(Nos. O 6329, O 6330, Os 521, Os 522 and Os 523), and a
single lateral arm plate from Kutná Hora-Kaòk (No.
O 6337). All specimens are housed in the National Museum,
Description: Lateral arm plates: Figures 3.1 and 3.2 il-
lustrate the outer surface of a distal (or median) plate (No.
O 6329), while Figures 3.3, 3.4 and 3.5 represent a median (or
proximal) lateral arm plate (No. O 6330). The plates are rela-
tively thin, with an almost flat and smooth outer surface and a
dorsally receded distal margin. Plate thickness is more or less
constant in all places; in cross-section the plate is semicircular.
The ventral side is slightly flattened. The proximal part of the
outer surface shows a fine but poorly developed striation,
which is mostly horizontally or subhorizontally directed, and
articulation elements are not visible here (see Figs. 3.1,3,4).
Very typical is the ornament consisting of a fine granulation.
The small, equal-sized granules are best preserved in sample
O 6329 (see Figs. 3.1 and 3.2), where little pores can be rec-
ognized between the granules. The granules in No. O 6330 are
abraded or otherwise damaged in the distal part of the plate
base (see Fig. 3.5), but the pores between them are easily seen.
The ornament covers the rest of the outer surface (except for
the proximal part, which has fine striation), and runs to the
distal margin between the tubercles. The horseshoe-shaped tu-
bercles are almost of equal size, positioned directly on the dis-
tal margin. Interspaces between the tubercles correspond to tu-
bercle width and are not morphologically separated from the
rest of the outer surface. The inner surface shows only a
curved element for vertebral articulation; no pegs or other
marked articulation elements are visible. Tentacle pore inden-
tation is relatively large and well developed in all plates.
Plates of the present species are relatively small; for example,
in O 6330 the height of the plate is 0.73 mm and its maximum
length is 0.80 mm; in O 6329 it is 0.73 mm and 0.86 mm, re-
The relatively large collection of lateral arm plates of type
R (= Amphiura? plana) in the Bohemian material allows a re-
construction of morphological variation from proximal and
median plates to distal ones. Fig. 3.1 illustrates, for example, a
distal (or median) plate with 4 tubercles, while Fig. 3.3 shows
a median (or proximal) plate with 5 tubercles.
Lateral arm plates of the present species were originally de-
scribed by torc (1996, p. 204210) as type R from the Tu-
ronian strata of the Bohemian Cretaceous Basin. The plates
studied here correspond completely to examples illustrated by
Jagt (1999, 2000a) and by Kutscher & Jagt (in Jagt 2000) and
are assigned to Amphiura? plana without any doubt.
Type R lateral arm plates are fairly small (see above), on av-
erage even more so than those of the Upper Cretaceous Ophio-
coma? senonensis (Valette, 1915) and must have formed com-
paratively narrow arms. These arms were most likely fairly
smooth too. The highly typical lateral arm plates of the present
species are easily distinguished from those of all co-occurring
Fig. 2. The Velim-Václav section, Czech Republic. A, C grey,
echinoderm-rich calcareous claystone matrix of conglomerate, B
light-greenish echinoderm-rich calcareous claystone to clayey lime-
stone matrix of conglomerate. W.a. Whiteinella archaeocretacea
Biozone. Modified after ítt et al. (1997a).
Fig. 1. Location of Velim and Kutná Hora-Kaòk within the Bohemian
THE OPHIUROID AMPHIURA? PLANA IN BOHEMIAN CRETACEOUS BASIN 39
brittle stars. Only Ophiothrix? bongaertsi Kutscher et Jagt in
Jagt, 2000 has comparable lateral arm plates, which are also
present in the material from Kutná Hora-Kaòk. Lateral arm
plates of Ophiothrix? bongaertsi (also see Jagt (2000a, p. 25);
and Kutscher & Jagt (in Jagt 2000, p. 72) are reminiscent of
Amphiura? plana, from which it differs in having even more
clearly scythe-shaped lateral arm plates (thin dorsal portion),
and more numerous and more close-set spine tubercles at the
distal margin (911 in number).
Kutscher & Jagt (in Jagt 2000, p. 71) noted that, Higher
magnification reveals a fine granulation of the outer surface
which, however, may be nothing more than a rather coarse
Fig. 3. Scanning electron micrographs of lateral arm plates of Amphiura? plana. Velim pocket Václav locality. 1 Outer surface of dis-
tal (or median) lateral arm plate (No. O 6329), distal left. Scale bar = 100
m. 2 Detail of distal part of the same plate. Scale bar =
m. 3 Outer surface of median (or proximal) lateral arm plate (No. O 6330), distal right. 4 Outer surface of same plate in proxi-
mal-ventral view, distal right. Scale bar for figures 3 and 4 = 100
m. 5 Ventral portion of distal end of the same plate, distal right. Scale
bar = 100
stereom structure since the same structure is seen at the proxi-
mal margin and in the tubercles. The present author, howev-
er, assumes that the fine granulation is a highly typical orna-
ment, not just a coarse stereom structure. This is demonstrated
by the fact that among various lateral arm plates of this spe-
cies, the size of the granules is basically the same. The size of
the granules is also an important taxonomic feature in the
present species. It is also important that this granulation is re-
placed by a weak striation in the proximal part on the outer
A few vertebral ossicles in the Bohemian material also re-
semble the vertebra illustrated by Kutscher & Jagt (in Jagt
2000, pl. 33, fig. 3). In the present material, no dorsal or ven-
tral arm plates or other skeletal elements other than lateral arm
plates and vertebrae have been identified. Arm fragments with
preserved spines and ventral arm plates as well as dissociated
vertebrae, dorsal arm plates, radial shields and possibly even
other skeletal elements from arms and disc have previously
been recorded in material from the type area of the Maastrich-
tian Stage, as well as from Rügen and Møn (see Jagt 2000a;
Kutscher & Jagt in Jagt 2000).
Kutscher & Jagt (in Jagt 2000, p. 72) provisionally assigned
this species to the extant genus Amphiura (Amphiuridae),
mainly on the basis of the structure of the radial shields, verte-
brae and on the presence of large tentacle pore indentations,
as well as on lateral arm plate structure.
Regarding the paleoecology of the present species, Jagt
(1999, p. 200; 2000b, p. 530) noted that Most amphiurids
live buried at depths of ca.10 cm, with only the tips of arms
protruding through mucus-lined channels, catching detritus,
but also small animals such as worms and juvenile molluscs.
Burrows are ventilated by undulations of the arms. Sometimes
many individuals may form webs across the seafloor. Most
extant forms live on muddy bottoms, some also under rocks in
low water, but, unlike other ophiuroids, they do not move
about freely.. This mode of life is illustrated by Fig. 4.
The large number (3739 in total) of lateral arm plates from
Velim allows a quantitative evaluation to be carried out (see
Table 1). The locality Kaòk yielded fewer specimens (see
above). The abundance of individual species as based on lat-
eral arm plates are expressed in %. 3721 lateral arm plates
(representing about 20 ophiuroid species) from samples A, B,
and C of the Velim-Václav section (see Fig. 2 and right-hand
column in Table 1), identified to species, were evaluated. This
large statistical set offers relatively exact abundances of the
individual species. The abundance of Amphiura? plana
based on lateral arm plates in this set is 4.62 % (172 speci-
mens). The most exact data on the abundance of this species
were, however, obtained by a study of bulk samples (1.5 litre
of rock) from horizon C (Fig. 2). This sample contains 2561
lateral arm plates which were identified to species, in which
lateral arm plates of the present species constitute 5.19 % (133
specimens; see the left-hand column in Table 1).
With about 5 % at Velim, Amphiura? plana seems to be the
fourth most common ophiuroid species there. It is necessary
to mention, that the quantitative ratios of the sceletal elements
could be considerably changed by taphonomical processes
(such as selective transport).
Paleogeographical and stratigraphic distribution
The present species is currently known from the Lower
Maastrichtian of the isles of Rügen (formerly Rujana, Germa-
ny) and Møn (Denmark), the Lower Campanian of southern
Sweden, as well as the Upper Campanian and Lower and Up-
per Maastrichtian of the Netherlands and Belgium (the type
area of the Maastrichtian Stage) and the Lower Turonian (Bílá
hora Formation) of the Czech Republic. In material from the
Upper Cretaceous (Cenomanian, Turonian, Coniacian and
Santonian) deposits of Tunisia Amphiura? plana is absent
The paleogeographical and stratigraphic distribution of the
present species, as shown in Fig. 5, shows that Amphiura?
plana is a widely distributed taxon ranging from the Lower
Fig. 4. Cross-section through seafloor showing individuals of the extant species Amphiura filiformis buried at depths of ca. 10 cm, with
only the tips of arms protruding through mucus-lined channels. Modified after Blegvad (1915).
Table 1: Abundance of Amphiura? plana based on lateral arm
plates from Velim.
SAMPLES FROM VELIM-VÁCLAV
The bulk sample (C)
Samples A, B, C (including the bulk sample)
lateral arm plates %
lateral arm plates
THE OPHIUROID AMPHIURA? PLANA IN BOHEMIAN CRETACEOUS BASIN 41
Turonian (?and Upper Cenomanian) to the Upper Maastrich-
tian. This species appears to represent an evolutionarily con-
servative lineage which existed for more than 25 million years
(for geochronology see Gradstein & Ogg 1996).
In the course of detailed studies of the enormously rich Bohe-
mian material (Turonian nearshore deposits, Korycany Member
of the Peruc-Korycany Formation and Bílá hora Formation, Bo-
hemian Cretaceous Basin), over 170 lateral arm plates of Amph-
iura? plana have been collected (torc 2002). The fine granula-
tion and granule size of outer lateral arm plate surfaces seem to
be important taxonomic features. The lateral arm plates of this
species are quite small and light in construction and must have
formed fairly narrow arms of circular or oval cross-section. The
arms of Amphiura? plana were, moreover, most likely fairly
smooth. The abundance of Amphiura? plana is, according to
the lateral arm plates, about 5 % at Velim, with this species the
fourth most common ophiuroid. This species appears to repre-
sent an evolutionarily conservative lineage with extensive pa-
leogeographical and stratigraphical ranges.
Fig. 5. Geographical distribution of Amphiura? plana in the Upper
Cretaceous of Europe. 1 Bohemian Cretaceous Basin (Czech Re-
public, Lower Turonian); 2 type area of the Maastrichtian Stage
(southeast Netherlands and northeast Belgium, Upper Campanian,
Maastrichtian); 3 Rügen (Lower Maastrichtian); 4 Møn (Low-
er Maastrichtian); 5 southern Sweden (Lower Campanian).
Acknowledgments: I wish to thank Dr. Jiøí ítt (Institute of
Geology ASCR, Prague), Bc. Jason R. Kucker (Farmingdale,
New York), Dr. Francis Raschka (New Jersey), Dr. Vilém
Danìk (Prague), and Dr. John Jagt (Maastricht), for their kind
help and many valuable suggestions concerning this article.
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