GEOLOGICA CARPATHICA, AUGUST 2009, 60, 4, 339—342 doi: 10.2478/v10096-009-0025-0
Apart from rare informal notes of “Lithodomus” in live corals,
Kühnelt (1931) was the first who described and correctly in-
terpreted such an association in the fossil record (Kleemann
1982). Kelly & Bromley (1984) provided an ichnological no-
menclature of clavate borings, covering many domichnia pro-
duced by bivalves, including Lithophaga. Some of the latter
produce Gastrochaenolites torpedo Kelly & Bromley, 1984.
Edinger & Risk (1994) noted the fossil borings of Lithophaga
bisulcata in Oligocene Caribbean corals such as Gastrochaeno-
lites vivus [Lithophaga bisulcata (Orbigny 1853, non 1842) is
a junior synonym of L. (Leiosolenus) appendiculata (Philippi,
1846) (Kleemann 2009)]. However, without a holotype desig-
nation, their new ichnospecies must be regarded as a nomen nu-
dum (see Discussion). This paper describes G. hospitium isp.
nov. from the Eocene and Miocene strata of Austria (Fig. 1).
The types and other material are stored in the collection of the
Institute of Paleontology, University of Vienna (IPUW).
Ichnogenus Gastrochaenolites Leymerie, 1842
D i a g n o s i s : (Kelly & Bromley 1984: p. 797): Clavate bor-
ings in lithic substrates. The apertural region of the boring is
narrower than the main chamber and may be circular, oval, or
dumb-bell shaped. The aperture may be separated from the
main chamber by a neck region which in some cases may be
widely flared. The main chamber may vary from subspherical
to elongate, having a parabolic to rounded truncated base and
a circular to oval cross-section, modified in some forms by a
longitudinal ridge or grooves to produce an almond- or heart-
shaped section. (For the general range in morphology of spe-
cies of Gastrochaenolites see Kelly & Bromley 1984: text-
T y p e i c h n o s p e c i e s : Gastrochaenolites lapidicus Kelly
& Bromley, 1984: 797—798, text-figs. 3A, 4A—B.
Gastrochaenolites hospitium isp. nov.
Gastrochaenolites vivus n.n. – Edinger & Risk, 1994, p. 584, 587, 588,
592, figs. 9 (far left), 14
D e r i v a t i o n o f n a m e : From Latin hospitium, hospitali-
ty, which the trace producers obtain lifelong from their hosts.
T y p e s : Holotype IPUW 200900010001, a sediment-filled
Lithophaga (Leiosolenus) boring within the coral Favia mag-
nifica Reuss, 1871, collected from the Waschberg by H. Zapfe
(pers. comm.). The boring is illustrated in longitudinal section
(Fig. 2; Kleemann 1994: pl. 16, fig. 7). Sixteen false floors,
somewhat semi-circular in midline-section, can be counted in
the extended basal part of the boring (below the shell). The
shell remains are about 30 mm long. The sectioned part of the
boring is about 80 mm long and 10 to 12 mm wide, increasing
very little from the base. Note the slight S-like bending in the
isp. nov., trace fossil by a coral-
associated boring bivalve from the Eocene and Miocene
Paleontology, Centre of Earth Sciences, University of Vienna, Althanstr. 14, A1090 Vienna, Austria; firstname.lastname@example.org
(Manuscript received February 19, 2009; accepted in revised form June 25, 2009)
Abstract: Gastrochaenolites hospitium isp. nov. is a domichnial boring showing the so-called false floors in scleractinian
coral skeletons. The borings are semi-circular in mid-longitudinal section. They are produced by the mytilid Lithophaga
(Leiosolenus) and keep up with further growth of their hosts for years. The false floors, being a retrusive equilibrium
trace, are related to annual events.
Key words: Ichnology, trace fossils, domichnia, lebensspuren, corals, bivalves, Lithophaga, Leiosolenus.
Fig. 1. The locality Waschberg or Seggauberg within a line drawing
Fig. 2. Holotype of Gastrochaeno-
lites hospitium isp. nov., IPUW
200900010001, in skeleton of Favia
magnifica Reuss, 1871, Lower Eocene
(Waschberg Zone, Waschberg lime-
stone), Waschberg, Lower Austria.
Scale in cm. Previously figured in
Kleemann (1994: pl. 16, fig. 7).
Fig. 3. Paratype of G. hospitium isp.
nov., IPUW 200900010002, in same
host colony as the holotype. Note
seven false floors below obliquely
cut valves. Scale in mm.
the neck of the trace, is narrower than the main chamber, lead-
ing to a dumbel-shaped aperture. In the fossil situation, the
neck part may be inconspicuous or lost. In casts, the false
floors are hidden inside. Nevertheless, their presence may be
indicated by a surface ornamentation through constrictions
and widenings of the boring’s basal part, resembling a dowel
(Kühnelt 1931: pl. 24, fig. 6a—e). The general form of casts is
more or less elongated ellipsoidal to cylindrical. The false
floors result from former positions of the producers (see Dis-
cussion). In longitudinal section through the axis of the bi-
valve borings basal part, the decisive and significant feature is
two to several bow-shaped or semi-circular lines, representing
the “Zwischenböden” or “Kappen” of Kühnelt (1931).
The dimensions of G. hospitium isp. nov. vary according to
the size and longevity of the respective trace maker and to the
growth rate of the respective host. The former influences par-
ticularly the number, the latter the distance between false
floors. The diameters of these trace fossils, as known so far,
range from a few to about 25 mm. Their length may reach a
few millimeters to, in Recent examples, over 150 mm.
O t h e r m a t e r i a l : Several pieces of a big colony of Mont-
astrea from the Miocene (Badenian) in the Tittenbacher quar-
ry at Seggauberg (Fig. 1), near Leibnitz in southern Styria,
Austria (Kleemann 1994: text-fig. 1, pl. 15, fig. 1), were cut to
find more G. hospitium isp. nov., IPUW 4453, 4454. IPUW
4453/1-3, contain this boring, which shows two distinct size-
classes. In a particular case, these borings interfere with each
other (Fig. 4.1—2). The wider one on top of the figure is about
15 mm wide and displays remains of only four false floors
(more may have been present before cutting). It crosses and
terminates two other slender borings belonging to the same
ichnospecies. These are only about 5 mm wide but show eight
to nine false floors below the shell remains or their casts, over
a length of about 25—30 mm (Fig. 4.2). The wider boring was
caused by L. coralliophila Kleemann, 1994, the smaller ones
basal, old part of the boring. It indicates an adaptation of the
boring axis to the change in direction of host coral growth.
Paratype IPUW 200900010002 is observed in an oblique
section of another Lithophaga boring in the same host colony
as in Fig. 2. Filled with fine-grained sediment, the boring is
observed in oblique section as an elongated oval, about
40 mm long and 12 mm wide, depicting seven false floors be-
low the bivalve (Fig. 3).
T y p e h o r i z o n : Waschberg limestone, the only marine
stratigraphic unit within the Waschberg Zone (Wessely 2006:
p. 71). The Waschberg limestone is Early Eocene (Ypresium,
L. Krystyn, pers. comm.) in age.
Type locality: Waschberg, Lower Austria (Fig. 1). No de-
tailed information about the precise locality was provided by H.
Zapfe. The Waschberg (388 m) lies south and next to the village
Wollmannsberg (236 m) in Lower Austria, north of Vienna.
T y p e h o s t c o r a l : Favia magnifica Reuss, 1871.
D i a g n o s i s : Elongated, sub-cylindrical bivalve boring
within a host coral skeleton, with two or more hemi-spherical
bottoms, piled in each other, at the basal end. In casts of the
borings, this is mirrored by ring-shaped constrictions/eleva-
tions near the rounded base, resembling a pile of mini-cups. In
longitudinal section, the boring is an elongated to ribbon-
shaped oval, with semi-circular or bow-shaped lines towards
the basal end (Figs. 2—4).
Description: Boring of an adult mytilid Lithophaga (Leio-
solenus), which kept up with the growth of its host for one or
more years, resulting in an elongated basal part of the boring
with at least two so-called false floors (Kühnelt 1931: text-
fig. 2; Kleemann 1980: fig. 37; Kleemann 1982: pl. 2, fig. 6,
pl. 3, fig. 8). This characteristic feature, being an equilibrium
structure (Frey & Pemberton 1985), easily distinguishes G.
hospitium isp. nov. from all other Gastrochaenolites ispp.,
which lack them (Kelly & Bromley 1984; Edinger & Risk
1994: fig. 9). The short siphonal part of the boring, becoming
GASTROCHAENOLITES HOSPITIUM ISP. NOV., TRACE FOSSIL FROM THE EOCENE AND MIOCENE (AUSTRIA)
Fig. 4. Gastrochaenolites hospitium isp. nov., in Miocene (Badenian) Mont-
astrea from Seggauberg, Styria. 1 – A wide boring, in the left upper corner,
crosses and terminates a slender one, coming up almost straight. 2 – Frac-
ture area, of the specimen shown in Fig. 4.1, which exhibits a second slender
boring, almost parallel to the first. Both borings have eight to nine false
floors in the cut or split open basal part (see Discussion).
by a different species (Fig. 4.1—2, see Discussion). The slab
IPUW 4454 contains a fragment of a single, small boring,
whose remaining part is in the counterpart slab. The shell is
approximately 8 mm long. It lies above five false floors that
occur over a distance of 18 mm. This boring shows a widening
from three to five millimeters. Two slab pieces, IPUW 4467/1-2,
of an unidentified coral of unrecorded age are riddled with
L. (Leiosolenus) borings; they contain borings with shell re-
mains, some of them accompanied by false floors (Fig. 5).
Gastrochaenolites, not mentioned in the 2
edition of Trace
Fossils (Bromley 1996), is a member of domichnia (Bromley
1996: p. 192). Edinger & Risk (1994: pp. 584—585) noted:
“Coral associates showed no evidence for host specificity with
the exception of Gastrochaenolites vivus n. isp., the boring
made by Lithophaga bisulcata in live corals, producing false
floors in the borehole (figs. 9, 14). This bivalve boring oc-
curred in Oligocene Diploastrea crassolamellata and Montas-
trea tampaensis, and Miocene Psammocora trinitatis. Modern
L. bisulcata in the Caribbean bore into many species of dead
corals, but their primary habitat is in live Siderastrea siderea
and Stephanocoenia intersepta (Scott 1988). This limited spe-
cies specificity apparently had no effect on the bivalve’s sur-
vival.”. The legend of their fig. 14 reads: “Gastrochaenolites
vivus n. isp. in the Miocene coral Psammocora trinitatis. Bri-
zas del Caribe site” (Edinger & Risk 1994: p. 592). Nothing
else, particularly no holotype designation was provid-
ed, resulting in a nomen nudum for their ichnospecies.
G. hospitium isp. nov. is a trace fossil, produced
by mytilid bivalves belonging to small to middle-
sized Lithophaga (Leiosolenus) species associated
with various living host corals. Like all members of
this subgenus, they can line their borings, including
voids in the dwelled substrate, with calcareous de-
posits. Adults that live in living corals keep pace
with the host’s growth by stepwise moving up in
their borings. Thus, G. hospitium isp. nov. belongs
to domichnia as well as equilibrichnia.
Most likely, a new false floor is produced once an-
nually by depositing calcareous secretions that then
consolidate, mainly in front of the shell and laterally
at the boring margins. The floors mirror the some-
what hemi-spherical anterior end of the shell (Klee-
mann 1982: pl. 2, fig. 6, pl. 3, fig. 8; Scott 1988:
fig. 4C). Because of the longevity of more or less
fully grown individuals, the borehole diameters ap-
parently remain the same for longer trace fossils. At
the same time, the number of false floors may attain
over 15 (Fig. 2) or even more in a Recent sample
(Kleemann 1982: pl. 2, fig. 6). In the latter, some
floors appear to be merely detrital accumulations and
not solid linings. Borings of L. (Leiosolenus) in a Re-
cent head-sized Astreopora from the northern Red
Sea, show very long (twice the shell length) basal
parts with relatively few false floors, probably indicat-
ing fast coral growth and little detrital influx (Fig. 6).
Considering (1) the type locality, where the Waschberg
limestone is the only marine stratigraphic unit within the
Waschberg Zone (Wessely 2006: p. 71), and (2) that voids in
the host coral and its borings are filled by a light coloured, car-
bonate and bioclastic sediment, the fossil material is probably
related to this unit (L. Krystyn, pers. comm.).
In the rather crumbly to chalky substrate of Badenian age at
Müllendorf in Burgenland, bivalve borings are mainly pre-
served as casts (Kühnelt 1931: pl. 24). When fragmented, the
basal part alone is sufficient to indicate G. hospitium isp. nov.,
whereas the bivalve part alone belongs to G. torpedo. The lat-
Fig. 5. IPUW 4467/1, a fossil coral piece of unknown locality and
age, exhibits mainly G. torpedo Kelly & Bromley, 1984, and a few
G. hospitium isp. nov. Scale in cm.
ter is the case in all fossils, in which the individual bivalve has
not (yet) produced false floors (Fig. 5) as in Recent examples
figured in Kleemann (1980: fig. 41; 2008: fig. 1 middle).
The interior of a big colony of Badenian Montastrea exhib-
its many borings produced by bivalves, not only of the domi-
nant Lithophaga coralliophila (Kleemann 1994: text-fig. 1,
pl. 15, fig. 1). In IPUW 4453, the wide boring of L. corallio-
phila obliquely crosses and terminates two slender G. hospi-
tium isp. nov. of a different, probably new species. As their
diameters do not noticeably widen, they indicate adult-sized
producers, distinctly smaller than the L. coralliophila crossing
above. The small bivalves have to be regarded as being adult,
because their size remained more or less stable for at least 8—9
years. They most likely died due to interspecific space compe-
tition. Parts of the bivalve shells and their casts are also visi-
ble. Their size, compared with the shell in the larger boring,
also indicates that two species of Lithophaga (Leiosolenus)
bored in the host simultaneously (Fig. 4.1—2). In IPUW 4467/
1-2, most borings have to be determined as G. torpedo Kelly
& Bromley, 1984, and only a few as G. hospitium isp. nov.,
although most likely produced by members of the same Litho-
phaga (Leiosolenus) species (Fig. 5).
Co-existing bivalve species can be observed occasionally in
Recent corals, but this generally seems to be avoided (Klee-
mann 2008). Nevertheless, intraspecific competition for space
and food may become a problem for individual borers under
crowded situations. The advantage of dense settlement in
hosts is assumed to be a substantially increased reproductive
success because simultaneous spawning can occur in close
range. Many bivalve specimens in living corals do not live
long enough to create false floors. In the fossil record, only the
latter can be determined as G. hospitium isp. nov., while the
former must be attributed to G. torpedo (Kelly & Bromley
1984). Thus, the decisive feature of G. hospitium isp. nov., is
the presence of false floors.
During the life time of associated bivalves, boring apertures
open onto the living coral surface. After a bivalve’s death, the
host closes the opening by further growth. Examples of G. hos-
pitium isp. nov. can be found not only in adjacent positions but
also in different depths or even above each other within the
same host skeleton, indicating successive generations of dwell-
ers (Fig. 4.1—2; cf. Kleemann 1994: text-fig. 1, pl. 15, fig. 1).
Fig. 6. Elongated borings of living Lithophaga (Leiosolenus) sim-
plex Iredale, 1939, in split-open host coral Astreopora sp., Safaga,
northern Red Sea. Frame about 13
As shown by Goreau et al. (1972: pl. 2), the mytilid Fungia-
cava eilatensis Goreau et al., 1968, exclusively associated
with fungiid corals (Hoeksema & Kleemann 2002), may also
produce aragonitic deposits indicating the pathway within its
boring. Nonetheless, no obvious false floors are developed in
the Fungiacava borings. Their shape is not cylindrical, but
rather changes from ovoid to a dorso-ventrally flattened heart-
shape (Goreau et al. 1972: p. 59). Thus, even if this Recent
form was found in the fossil record, its traces could not be as-
cribed to G. hospitium isp. nov.
Acknowledgments: Helpful criticism and comments on the
first draft by two reviewers, Á. Dávid and particularly A. Uch-
man, improved the paper substantially. Michael Stachowitsch
kindly improved the English of the second version.
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