J. Paleon!., 66(2), 1992, pp. 20C-205
Copyright O 1992, The Paleontological Society
0022-3360/92/0066-0200$03.00
MODE OF LIFE OF A NEW ONYCHOCHILID MOLLUSC FROM THE LOWER DEVONIAN OF BOHEMIA JIRI FRYDA ~ s t i e d nbi stav geologick?, MalostranskC namtsti 19, 1 18 2 1 Praha 1, Czechoslovakia ABSTRACT-Anew molluscan genus, Voskopiella, from the Lower Devonian of Bohemia is described and assigned to the Onycho-
chiloidea. The type and only known species is Voskopiella barborae n. sp. from the Nowakia elegans Zone (uppermost Zlichovian,
=Emsian) of the Suchomasty Limestone. Also discussed are its ontogeny, variability,and pathological development of ornamentation,
as well as the mode of life, in order to resolve the problem as to whether onychochiloideans are torted gastropods or untorted
paragastropods. A foliage supported mode of life or life in close association on or within algal mats is suggested for Voskopiella
barborae n. gen. and sp.
INTRODUCTION
has been given during the past 20 years
to the sinistrally coiled gastropods assigned to the families
Onychochilidae Koken and Clisospiridae Miller. The opinions
on the higher taxonomic position of the families and on their
relationships have often changed. Poor knowledge of the majority of species included in the above-mentioned families is the
main reason for the different evaluations of the higher taxonomic position of these families.
New discoveries and descriptions of many new genera and
species in recent years indicated that both families (Onychochilidae and Clisospiridae) are closely related (Horn?, 1964;
Peel, 1975a, 1986; Wangberg-Eriksson, 1979; Dzik, 1983; Linsley and Kier, 1984). However, the higher taxonomic position
of both families is not definitely resolved. Horn? (1964) considered clisospiraceans to be related to the onychochilaceans,
and thus included them in the suborder Macluritina Cox and
Knight. Dzik (1983) studied the larval development of the genus
Mimospira Koken, 1925 (belonging to the family Clisospiridae),
and proposed to separate both families from the suborder Macluritina and erected a new suborder Mimospirina to receive
them. Linsley and Kier (1984) proposed to place the superfamily
Onychochilacea Koken, 1925 (including the families Onychochilidae Koken and Clisospiridae Miller), together with the superfamilies Macluritacea Fischer and possibly Euomphalacea
De Koninck into the new order Hyperstrophina of the new class
Paragastropoda. Interpretations of the results of functional analysis of the shells of some Paleozoic gastropod groups were given
as the reason for their separation from the class Gastropoda.
According to Linsley and Kier (1984), these results show that
these groups of the Paleozoic anisostrophically coiled molluscs
underwent no torsion during ontogeny or did not originate from
torted ancestors and, thus, as untorted molluscs they could not
be gastropods.
Onychochiloideans represent a small group of the Paleozoic
molluscs, which are distributed from the Lower Cambrian to
the Lower Carboniferous. Outside of central Europe they have
been recorded from the Balto-Scandian region, Scotland, Wales,
U.S.S.R., Greenland, U.S.A., Canada, China, Australia, and
Antarctica. Onychochiloideans form a relatively rare component of the Paleozoic marine communities, which is the main
reason for the poor knowledge concerning them. In this paper
a new onychochiloidean genus is described from Bohemia in
order to contribute to the question of whether onychochiloideans are torted gastropods or untorted paragastropods.
The described specimens are deposited in the author's collection, Ustiedni ustav geologick?, Prague, U U G J F 1-49 (i.e.,
G
REAT ATTENTION
U U G J F 1 indicates specimen no. 1 in the collection of J. Frjida
in the Ustiedni ustav geologickl).
SYSTEMATIC PALEONTOLOGY
Superfamily ONYCHOCHILQIDEA
Koken, 1925
Family ONYCHOCHILIDAE
Koken, 1925
Genus VOSKOPIELLA
n. gen.
Type species. - Voskopiella barborae n. gen. and sp., Lower
Devonian, Zlichovian; Suchomasty Limestone, Barrandian area,
Bohemia (Figure 1).
Etymology. -The genus name alludes to the occurrence and
only known locality of this new taxon in the Voskop quarry.
Diagnosis.-Small, slender, cyrtoconoid, apparently sinistrally coiled shell; whorl profile strongly convex; sutures deeply
impressed; whorls with ornament of thin, prosocline threads
arranged conformable to apertural margin; base of shell concave; initial part of spire smooth, lacking ornamentation; gerontic whorls characterized by moderately expanded outer lip.
Included species.-The new genus is presently known only
from the type species, Voskopiella barborae n. sp., from the
Lower Devonian (Upper Zlichovian) of Bohemia.
Discussion.-The new genus Voskopiella is assigned to the
family Onychochilidae Koken because of the form of the base
of the shell and aperture, as well as the apparent sinistral coiling
of the shell. However, Voskopiella n. gen. deviates by its general
shape from the majority of genera of this family. The majority
of onychochilid genera are characterized in having a shell with
only a few whorls. Only Sinistracirsa Cossmann and three recently described genera from the Balto-Scandian region are exceptions: Bodospira Wangberg-Eriksson, 1979, Angulospira
Wangberg-Eriksson, 1979; and Tapinogyra Wangberg-Eriksson,
1979.
Voskopiella n. gen. is most similar to the genus Tapinogyra
Wangberg-Eriksson, which is represented by only one described
species, Tapinogyra glaphyra Wangberg-Eriksson, 1979, from
the Upper Ordovician of Sweden. Both genera agree in the general shape of their shell, the form of the aperture, and the base
of their shells. Voskopiella n. gen. is characterized by having
deeply impressed sutures, a very convex whorl profile, and prosoclinal threads on the external whorl face, in contrast to Tapinogyra, which has shallow sutures and a uniformly rounded
whorl profile and which lacks ornamentation. The expanded
outer lip of the gerontic aperture is also not found in Tapinogyra
glaphyra Wangberg-Eriksson, in contrast to Voskopiella barborae n. gen. and sp. However, this difference may be due to
the fact that the only hitherto known species of the genus Tapi-
FR YDA- NE w ONYCHOCHILID FROM BOHEMIA
20 1
apparently sinistrally coiled shell and its concave base, the form
of the aperture, and the absence of the basal lamella. This new
genus has the most morphological similarity to the monotypic
genus Tapinogyra Wangberg-Eriksson from the Upper Ordovician of Sweden.
VOSKOPIELLA
BARBORAE n. sp.
Figures 2.1-2.7, 3.1-3.3
Diagnosis. -By monotypy, the same as the genus.
Description. -Small, high-spired, apparently sinistrally coiled,
cyrtoconoid shell; up to seven whorls present; external walls of
whorls considerably convex; sutures deeply impressed; mean
spiral angle approximately 28"; sutural slope angle about 15",
its values changing moderately during later phases of ontogeny;
base of shell concave; lateral, convex wall of final whorl curves
into its basal part, forming a strong curvature in the most abapical portion of the whorl; basal abapical face of final whorl
descends fairly steeply from this curvature on the periphery
towards the shell axis; strong curvature in the most abapical
point of the whorl forms a distinct boundary between the lateral
and basal parts of whorl; adapical end of external lip of aperture
joins the most abapical point of preceding whorl; aperture tangential; external lip of aperture distinctly prosocline; thickness
and structure of shell unknown; outer face of whorl ornamented
by thin, prosocline threads arranged conformably to apertural
margin; threads and sutures intersect at acute angles and their
value ranges from 42" to 58'; each thread runs directly between
sutures on the outer face of the whorls; threads curve from the
FIGURE
I -Location of fossil locality. 1, the Srbsko Formation (Give- lateral face of whorl, forming a smooth, even curvature, to the
tian); 2, the Acanthopyge Limestone (ChoteE Formation, Eifelian); 3, basal face of whorl; curvature of the threads reaches the highest
the Suchomasty Limestone (Daleje-Tiebotov Formation, Upper Zli- value in the most abapical point of the whorl; threads continue
chovian-Lower Eifelian); 4, the KonCprusy Limestone (Praha For- adaxially along the basal surface of whorl into shell axis.
mation, Pragian); 5, the KotLs Limestone (Lochkov Formation,LochHolotype. -Specimen figured herein as Figure 2.1, 2.6, U U G
kovian); 6 , Silurian strata; 7, the OEkov overthrust; 8, normal faults;
9, boundary of quany; 10, occurrence of Voskopiella barborae n. gen. J F 1.
Paratypes. -Other specimens figured herein as Figure 2.2and sp.
2.5, 2.7 and unfigured specimens; U U G J F 2-49.
Etymology. -The species is named in honor of my wife, Mrs.
nogyra Wangberg-Eriksson is established on only one available Barbora H. Fr9dov6.
specimen, which may represent a juvenile. In the case of VoskoType locality and type horizon. -All the described specimens
piella barborae n. gen. and sp., only a few individuals of the were collected in a new quarry, which is situated on the northern
several dozen studied specimens were found with well-devel- slope of Voskop Hill near Kongprusy (Figure 1). The Kongprusy
oped gerontic whorls.
Limestone of the Praha Formation and the Suchomasty LimeVoskopiella n. gen. also resembles the genera Sinistracirsa stone of the Daleje-Tiebotov Formation are exposed in this
Cossmann (Lower Devonian) and Mimospira Koken (Ordovi- quany (ChlupaE, 198 1). The Suchomasty Limestone (Upper
cian-Silurian) in some characters. Voskopiella n. gen. can be Zlichovian-Lower Eifelian) overlies the reef complex of the Kodistinguished from Sinistracirsa Cossmann by its differing or- n6prusy Limestone (Pragian). The described specimens were
namentation and by the form of the base of the shell. Voskopiella collected in a single layer of reddish biomicritic and biosparitic
n. gen. is similar to Mimospira Koken (family Clisospiridae Suchomasty Limestone together with a relatively rich assemMiller) in the form of the whorl profile and by its type of or- blage, consisting of trilobites (proetids and scutelluids) of the
namentation. However, in Mimospira Koken the surface of the Orbitoproetus-Scabriscutellum assemblage (ChluphE, 1983),
whorls is ornamented by distinct prosocline ribs and by thin brachiopods, goniatites, gastropods (pleurotomariaceans), and
prosocline threads in Voskopiella n. gen. The cyrtoconoid shell rarely monoplacophorans and tentaculitids. The dacryoconarid
of Voskopiella barborae n. gen. and sp. is more slender than in tentaculitids were identified by Pave1 Luke: (Prague) as Nowakia
the shells of previously described species of Mimospira. The elegans (Barrande), which is a zonal species indicating the oldest
mean spiral angle in Voskopiella barborae n. sp. represents ap- biozone of the Suchomasty Limestone (uppermost Zlichovian;
proximately one-half the same value in the type species of Mi- ChlupiE et al., 1979). All shells of Voskopiella barborae n. gen.
mospira, Mimospira helmhackeri (Perner). Perner (19 1 l) de- and sp. were collected only in several hundred cubic centimeters
scribed a small basal lamella on the gerontic whorl in the type of the fossiliferous limestone, where these shells formed a disspecies of Mimospira. However, this morphological character tinct cluster. The layer bearing this cluster of shells was examhas hitherto not been reported in any other species of this genus. ined in great detail, but no shell of this mollusc was found outside
The moderately expanded outer lip of the gerontic aperture in this cluster. The shells of Voskopiella barborae n. gen. and sp.
Voskopiella barborae n. gen. and sp. is not, however, similar in bear no traces of mechanical damage and, thus, the cluster of
general form to that of the poorly known gerontic whorl in shells is autochthonous rather than the result of the accumuMimospira helmhackeri (Perner).
lation of transported shells.
The new genus Voskopiella is referred to the family OnychoMaterial. -About 60 undeformed specimens were found at
chilidae Koken, 1925, on the basis of the general shape of the this locality.
202
JOURNAL OF PALEONTOLOGY, V. 66, NO. 2, 1992
Rome 2- Voskopiella barborae n. gen. and sp. from the uppermost Zlichovian (Lower Devonian) of Bohemia. 1, 6, lateral and basal views of
holotype, UUG JF 1; 2,lateral view of paratype A,UUG JF 2;3,lateral view of adult specimen, paratype B, UUG JF 3; 4,oblique basal view
of juvenile specimen, paratype C, UUG JF 4;5. lateral view of specimen with pathological development of ornamentation, paratype D, UUG
JF 5; 7,abapertural view of a gerontic whorl, paratype E, UUG JF 6;all x 15.
Ontogeny.-The outer surface of the first one and a halfwhorls
of the shell is smooth. Initial whorls of the shell are apparently
sinistrally coiled in the same manner as the subsequent whorls
(i.e., homestrophic shell). The maximal diameter of the smooth,
spherical initial shell is about 0.16 mm (only two measured
specimens). The threads appear approximately after the first 1.5
whorl revolutions and their distance ffom one another ranges
from 0.05 to 0.10 mm. The distance between threads continually
FRYDA-NE W ONYCHOCHILID FROM BOHEMIA
increases (Figure 3.2) and the threads become more distinct
during ontogeny. The value of the angle between threads and
sutures is rather constant during ontogeny. Individuals with the
shorter distance between threads have higher values for this
angle. The height/width ratio of initial whorls (technique of
measurement described below) is about 0.5 and this value is
approximately constant during ontogeny up to the end of the
fifth whorl. The height/width ratio continually increases and
becomes more variable during further ontogeny (Figure 3.1).
The sutural slope angle is approximately constant during early
ontogeny and it increases moderately during late ontogeny (Figure 2.3). The aperture is brought close to the shell axis and it
is moved in an abapical direction during growth of the gerontic
whorl (Figure 2.3, 2.7) by an increase of the value of the sutural
slope (up to 22') and a narrowing of the basal, concave part of
the shell. A further character of the gerontic whorl is the moderately expanded outer lip of the aperture (Figure 2.7). The form
of the inner lip of the gerontic whorl is unknown.
Pathology. -An anomalous development of the ornamentation was found in specimen UUG J F 5 (Figure 2.5). This anomalous ornamentation is developed only on the adapical half of
the whorl. The anomaly appears to have been continuous and
the beginning of the anomaly was caused by no ascertainable
damage of the shell. The course of the threads indicates a slower
growth rate of the adapical half of the whorl. The threads run
normally from the lower suture to half-way between the sutures.
Here the threads curve adapically and they have an orthoclinal
direction. Subsequently, close to the upper suture, they are again
normal. The size of the delay in growth increases during ontogeny and reaches a maximal value at three-fourths of a whorl
volution from the beginning of the anomaly. The maximal value
of the delay equals the distance of the threads, because the treads
curve into a normal prosoclinal direction as soon as the threads
reach the place where the preceding thread would have been
developed in the case of normal development (Figure 2.5). The
normal course of the threads is indicated by a very fine groove
that joins the unanomalous abapical part of the thread with the
prosoclinally oriented adapical part of the delayed, subsequent
thread. The threads are also more indistinct in part of their
anomalous development. The anomalous development changes
continually into a normal condition during subsequent ontogeny. The total length of the anomalous development represents
approximately one and one-quarter of a whorl volution. It is
probable that this shell anomaly was caused by the pathological
function of the active, shell-forming part of the mantle edge.
The weakly expressed development of the anomalous threads
supports this interpretation (Boshoff, 1968).
Variability. -The individual specimens have a similar value
of the height/width ratio in early ontogeny (Figure 3.1). The
differences in this value among measured specimens are comparable with errors of measurement. The formation of the gerontic whorl begins in different shell sizes. This is the reason for
considerable variability in the height/width ratio of the whorls
during late ontogeny (Figure 3.1). There is high variability in
the distance of the threads (Figure 3.2) and in the size of the
threads on the corresponding whorls. Individuals differ by about
100 percent in these values. Wangberg-Eriksson (1 979) pointed
out the possibility of the occurrence of sexual dimorphism in
the genus Mimospira Koken. The assumed sexual dimorphic
differences are manifested in two respects, the ornamentation
and the size and proportions of the shell (see Wangberg-Eriksson, 1979, p. 3 1). The size and the proportions of the shell are
constant during early ontogeny in Voskopiella barborae n. sp.
On the other hand, the distance between threads (Figure 3.2)
and the height/width ratio of the adult whorls (Figure 3.1) are
variable and their values form no distinct groups as in the case
1.01
0
1
I
I
,
,
,
,
,
,
2
Imm I
FIGURE
3-1, diagram showing relationship of height to width of whorl.
2, diagram showing relationship of distance of threads to width of
whorl: 3, diagramshowing relationship of ratio of widths of two
1
successive whorls to the width of the younger one. The points belonging to a single specimen are connected.
mentioned above. The differences in distance between threads
and the formation of the gerontic whorl in different shell sizes
probably correspond with changes of living conditions, and they
are an individual character of Voskopiella barborae n. sp. rather
than the result of sexual dimorphism.
Shellform analysis. -Raup ( 1 966) provided a method of analysis of molluscan shell coiling. This method provides a good
204
JOURNAL OF PALEONTOLOGY, V. 66, NO. 2, 1992
description of the shell geometry by means of four parameters
(W, T, D, S). The disadvantage of this method is the necessity
of knowing the shape of the whorl cross-section in the plane
containing the shell axis. The measurement of Raup's parameters requires damage to the measured specimens. Raup's method is not used in Voskopiella barborae n. gen. and sp. for this
reason. Only two simple relationships are used for the description of the changes of the shell geometry during ontogeny: 1)
the relationship between the height and the width of whorls
(Figure 3.1), and 2) the relationship between the ratio of the
width of two successive whorls and the width of the younger
one (Figure 3.3). The height of the whorls was measured as the
perpendicular distance of the upper and lower sutures, which
was projected into the plane of the shell axis (Figure 3.1). The
width of the whorls was measured as the maximal width of the
whorl, which is parallel with the sutures (and thus is perpendicular to the height of the whorls). This technique of measurement makes possible the measurement of incomplete specimens. It is impossible, however, to measure the gerontic whorl
(which lacks a lower suture) with this technique. The ratio of
the widths of two successive whorls equals Raup's parameter
W (the whorl expansion rate) if all of Raup's parameters (W, T,
D, S) are constant during ontogeny. It is, however, impossible
to determine the simple relationships between Raup's parameters and the above-mentioned ratio if all of Raup's parameters
are changing during ontogeny.
In Voskopiella barborae n. gen. and sp., the relative height of
the whorls (Figure 3.1) and the sutural slope angle increase from
the end of the fifth whorl and the ratio of the widths of two
successive whorls decreases (Figure 3.3). These facts distinctly
determine the geometrical trend of shell development as a tendency towards a relatively more slender shell and a tendency
towards rapid extension in the direction of the shell axis during
late phases of ontogeny prior to the formation of the gerontic
whorl. The shape of the gerontic whorl is the culmination of
these tendencies.
Mode of life. -The laws of gastropod shell form formulated
by Linsley (1 977), together with further information about functional morphology of gastropod shells (Vermeij, 197 1; Linsley,
1978; McNair et al., 198 I), make more exact determination of
the life position of fossil gastropod shells possible. The reconstruction of the life position of the shell of Onychochilus physa
Cossmann suggested by Linsley (1978) shows some "ungastropod" characters of the family Onychochilidae Koken. Linsley
and Kier (1 984) assumed that this molluscan group underwent
no torsion and, thus, must be separated from the class Gastropoda. A very unusual character of onychochilids is the steep
inclination of the shell axis to the substrate (high value of angle
E of Vermeij, 197 I) during locomotion. Linsley and Kier (1984)
considered this character to be an adaptation to hyperstrophy.
The shell was projected anteriorly above the head of the mollusc
as a result of presumed hyperstrophy regardless of reconstruction of Onychochilus as a torted gastropod or untorted paragastropod (see Linsley and Kier, 1984, figs. 1, 2). According to
Linsley and Kier (1984), an anteriorly projected shell has to be
lifted high off the substrate to accommodate inhalant currents.
Linsley (1978) considered onychochilids to be mobile but quite
slow animals carrying the shell dorsally and suspected them to
be predominantly algal-grazers or deposit feeders adapted to a
hard substrate.
The form of the aperture and the base of the shell (Figure 2.4)
in juvenile individuals of Voskopiella barborae n. gen. and sp.
are very similar to those in Onychochilus Lindstrom; thus there
is no reason for differing interpretation of the mode of life.
Nevertheless, during later phases of ontogeny the tendency to
develop a more slender shell and the tendency towards rapid
extension in the direction of the shell axis took place in Voskopiella barborae n. gen. and sp. These tendencies manifest
themselves by the increase of the relative height of the whorls
(Figure 3.1) and the sutural slope angle and in the decrease of
the W,+,/W, ratio (Figure 3.3), and they support elevating the
center of gravity of the shell in Voskopiella barborae n. gen. and
sp. A very high center of gravity has a disadvantage in balancing
the shell over the cephalopedal mass and it is a characteristic
feature of the slowest gastropods (Linsley, 1978). On the other
hand, the change of the form of the gerontic whorl could bring
about a reorientation of the mantle cavity relative to the earlier
whorls (Peel, 1975b). This reorientation could displace the center of gravity of the shell above the midline of the cephalopedal
mass (the law of shell balance; Linsley, 1977) from the former,
disadvantageous position (see Linsley and Kier, 1984, figs. 1,
2). The moderately expanded outer lip of the gerontic aperture
in Voskopiella barborae n. gen. and sp. could also help balance
the shell. However, the interpretation of the life position of the
high-spired shell, which would have projected anteriorly over
the head, appears to be very unusual. In addition, Voskopiella
barborae n. gen. and sp. is known from the Suchomasty Limestone, which was interpreted by ChlupaE (1983) as a high-energy,
shallow-water environment of Benthic Assemblage 3 of Boucot's (1975) classification.
If Voskopiella barborae n. gen. and sp. was a mobile mollusc
as an adult, then it belonged most likely to a group of infaunal
or epifaunal shell-draggers. According to Linsley (1979), infaunal, high-spired shell-draggers tend to have smooth or modestly ornamented shells and an unmodified tangential aperture.
Voskopiella barborae n. gen. and sp. has a modestly ornamented
shell and a tangential aperture, but the shape of its shell differs
in some characters from Recent, infaunal high-spired shell-draggers. The Recent, infaunal living terebrids and mitrids have the
the sides of the whorls nearly flat, conformable to the sides of
the spire and the relatively low value of Vermeij's angle E.
However, Voskopiella barborae n. gen. and sp. has considerably
convex whorls (Figure 2.1, 2.3), high value of the angle E (i.e.,
the aperture is open in the direction of probable movement),
concave base of the shell, and a moderately expanded outer lip
of the gerontic aperture. All these characters provide higher
resistance of the shell during movement through the sediment
and, thus, they are disadvantageous for an infaunal mode of
life. Epifaunal shell-draggers that are high-spired tend to modify
the aperture so that the plane of the aperture is parallel to the
axis of coiling of the shell (Linsley, 1979). This condition occurs
in the high-spired onychochilid genus Sinistracirsa Cossmann,
which was interpreted, for this reason, as an epifaunal shelldragger by Linsley (1979). Voskopiella n. gen. differs from Sinistracirsa Cossmann by a higher value of Vermeij's angle E. In
the case of Voskopiella barborae n. gen. and sp., this angle reaches approximately 50' and this value is not considerably changed
during ontogeny. It is evident that the interpretation of Voskopiella barborae n. gen. and sp. as an infaunal or epifaunal shelldragger is not without problems.
The mode of life of some Recent, high-spired prosobranch
gastropods, which live in a high-energy shallow-water environment, could help to explain the mode of life of Voskopiella
barborae n. gen. and sp. Some representatives of the caenogastropod families Cerithiidae Fleming, Cerithiopsidae Adam, and
Triphoridae Jousseaume live in this environment. The large
cerithiids often live in close association on or within algal mats
that cover different types of substrates. Some small cerithiids
live on large tree-like algae (i.e., foliage-supported mode of life).
The typical feature of both groups is the formation of mass
populations (Bandel and Wedler, 1987). A very interesting mode
of life was described by Bandel and Wedler (1987) in Triphora
F R YDA-NE W ONYCHOCHILID F R O M BOHEMIA
turristhomae(Holton~.
,,which lives in shallow-water o n the tissue
of sponges with only the uppermost part of the apex of its high
spire exposed above the sponge colony. Some species of the
genera Triphora Blainville and Cerithiopsis Forbes and Hanley
live inside the hollow bases of coral colonies, which originated
a s the result of bioerosion of these corals by boring organisms
(Bandel and Wedler, 1987). T h e above-mentioned examples
show the modes of life of some Recent, high-spired prosobranch
gastropods that live in high-energy, shallow-water environments. These high-spired gastropods are connected with a specific type of environment probably not only for their feeding
pattern, but also for protection against the dynamic effects of
this high-energy environment.
A foliage supported mode of life was also suggested by Peel
(1 977) for two small onychochilaceans (Onychochilus(?) reversa
(Hall) a n d Mimospira abbae Peel) from the Silurian of Nova
Scotia. T h e interpretation of Voskopiella barborae n. gen. and
sp. as a mollusc that lived amongst the foliage of algae o r in
close association o n o r within the algal mats is not in conflict
with the results of consideration about the functional morphology of the shell of Voskopiella barborae n. gen. a n d sp.,
which suggest that this mollusc belonged most likely t o very
slow o r immobile animals. In addition, this interpretation could
also explain a very interesting circumstance of occurrence of
Voskopiella barborae n. gen. and sp. in the cluster of about 60
undamaged shells. T h e considerations about the mode of life of
onychochiloideans are, however, complicated by absence of
knowledge about their anatomy a n d by little knowledge about
the relation between the shape of the shells and their mode of
life. F o r this reason, the interpretation of Voskopiella barborae
n. gen. a n d sp. as a very slow o r immobile mollusc that lived
amongst the foliage of marine algae o r in close association o n
o r within algal mats is not without problems.
ACKNOWLEDGMENTS
I a m especially indebted t o Robert B. Blodgett (Reston, Virginia) for critically reading the manuscript and providing many
helpful suggestions for improvement of this work; t o John S.
Peel (Copenhagen) for critically reading the manuscript, offering
valuable suggestions, a n d discussing some of the paleoecological
problems. T h e manuscript also benefited from the thoughtful
reviews of Robert M. Linsley (Hamilton, New York), David M.
Rohr (Alpine, Texas), a n d D o n C. Steinker (Bowling Green,
Ohio). I also thank Jiii K i i i (Prague) for his helpful discussion
a n d language correction, Ivo Chlupai: and Pave1 LukeS (both of
Prague) for their helpful information, Michal Mergl (Plzeii), who
collected the first specimens of the above-described mollusc and
loaned these specimens, a n d m y wife, Barbora, for her capable
assistance in the field.
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