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, DECEMBER 2016, 67, 6, 561 – 571

doi: 10.1515/geoca-2016-0035

Palaeobiology, palaeoecology and stratigraphic significance  

of the Late Miocene cockle Lymnocardium soproniense 

from Lake Pannon














MTA-MTM-ELTE Research Group for Palaeontology, Hungarian Natural History Museum, H-1431 Budapest, POB 137


MOL Hungarian Oil and Gas Company, H-1117 Budapest, Október 23. u. 18;


Department of Geology and Palaeontology, University of Szeged, H-6722 Szeged, Egyetem u. 2-6;


Department of Physical and Applied Geology, Eötvös Loránd University, H-1117 Budapest, Pázmány Péter sétány 1/c;


Department of Mineralogy and Geology, University of Debrecen, H-4032 Debrecen, Egyetem tér 1;


 Department of Geoscience, University of Wisconsin - Madison, 1215 W Dayton St, Madison, WI 53706 USA;

(Manuscript received January 25, 2016; accepted in revised form September 22, 2016)

Abstract: Stratigraphic subdivision of the Upper Miocene deposits in the Pannonian Basin has been traditionally based 

on the endemic mollusc species of Lake Pannon. The cockle species Lymnocardium soproniense Vitális, apparently 

evolving through a sympatric speciation event in the sublittoral zone of Lake Pannon about 10.2–10.3 Ma, attained wide 

geographical distribution in the Pannonian basin and thus may serve as a good stratigraphic marker. Lymnocardium 

soproniense was one of the few large-sized cockles in Lake Pannon, most closely related to its ancestor, L. schedelianum 

(Fuchs)and to another descendant of the latter, L. variocostatum Vitális. According to the δ


O stable isotope record of 

its shells, the large size of L. soproniense was coupled with an extended life time of more than 10 years, probably 

 reflecting a stable lake environment with increased resource availability and decreased predation. The species lived in 

quiet offshore conditions, below the storm wave base, where clay was deposited from suspension and the influence of 

currents was negligible. The base of the Lymnocardium soproniense Zone in the sublittoral deposits of Lake Pannon is 

defined by the first occurrence of the species, whereas the top of the zone is marked 

with the base of the overlying 

 Congeria praerhomboidea Zone, defined by the FAD of C. praerhomboidea.


Key words: Late Miocene, Pannonian Basin, Lake Pannon, molluscs, endemism, palaeoecology, stable isotopes.


Lymnocardium soproniense Vitális, 1934 is one of the ca. 200 

species of non-marine cockles that were described from the 

deposits of Lake Pannon (Müller et al. 1999; Geary et al. 

2000). This lake occupied the Pannonian basin in the Late 

Miocene and Early Pliocene as a relict of the Paratethys Sea 

(Harzhauser & Piller 2007). The stratigraphic subdivision of 

its thick sedimentary pile has been traditionally based on the 

prolific endemic mollusc fauna of the lake (for a summary, see 

Magyar & Geary 2012). Of the many cockle species of Lake 

Pannon, some possess a narrow stratigraphic span coupled 

with a wide geographical distribution; these species are con-

sidered to be good stratigraphic markers. 

Lymnocardium soproniense is one such species, and it is 

used to designate the sublittoral L. soproniense Zone (Magyar 

et al. 1999, 2007; Magyar & Geary 2012). This species, how-

ever, is usually known from poorly preserved and/or fragmen-

tary specimens, it was often confused with other large Lake 

Pannon cockles, and remained poorly documented in the 

palaeontological literature. In this paper we discuss its taxo-

nomic position, geographical distribution, palaeoecology, 

phylogenetic relationships, and stratigraphic significance. 


The palaeoecological and palaeobiological interpretations are 

based  on  sedimentological  facies  analysis  and  δ


O stable  

isotope profiles of shells.

Materials and methods

For this study we used the fossil mollusc collections of the 

Geological and Geophysical Institute of Hungary (MFGI, 

Budapest), the Hungarian Natural History Museum (TTM, 

Budapest), the Bakony Natural History Museum (TTM-BTM, 

Zirc), and the Naturhistorisches Museum Wien (NHMW, 

Vienna). Field work was conducted in the brickyard claypit of 

Mályi (northern Hungary, Fig. 1), the only outcrop known  

to us where Lymncoardium soproniense can be studied and 

 collected from the embedding sediments today. We measured 

the outcrop and interpreted the sedimentological features in 

order to assess the palaeoenvironment in which L. soproniense 


Stable isotope data from Lymnocardium soproniense and its 

relatives were gathered as part of a larger study on cardiid 

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, 2016, 67, 6, 561 – 571

bivalves from Lake Pannon (Johnson 2016). Shells were sam-

pled by using a 0.5 mm bit to drill a series of grooves  parallel 

to growth lines and spaced ~1 mm apart along the entire height 

of the shell. Samples were analysed at the  University of Arizona’s 

Environmental Isotope Laboratory using a KIEL-III device 

coupled to a Finnegan MAT 252 gas-ratio mass spectrometer 

at  a  precision  of  ± 0.1  ‰  for  δ


O. The data pertaining to  

L. soproniense and its closest relatives (L. schedelianum,  

L. variocostatum) are summarized and  discussed below.

Systematic palaeontology

Class BIVALVIA Linné, 1758

Family CARDIIDAE Lamarck, 1809

Subfamily LYMNOCARDIINAE Stoliczka, 1870–1871

Genus Lymnocardium Stoliczka, 1870–1871

Type species: Cardium haueri M. Hörnes, 1862 from the 

Upper Miocene of Árpád (Pécs, Hungary) 

Lymnocardium soproniense Vitális, 1934

1915. Limnocardium Penslii Fuchs — Papp S., p. 254, pl. 3, fig. 6. 


*1934a. Limnocardium soproniense n. sp. — Vitális, p. 705, pl. 7, 

figs. 1–4.

1934b.  Limnocardium soproniense n. sp. — Vitális, p. 77, pl. 1,  

figs. 1–4. [redescription]

1971. Limnocardium soproniense Vit. — Bartha, pl. 29, figs. 1,4.
1971. Limnocardium (Pannonicardium) mihaili sp. n. — Mihaila and 

Marinescu, p. 43, fig. 1, pl. 1, figs. 1–3.

2007. Lymnocardium soproniense — Magyar et al., p. 280, fig. 5.

Type specimen.  Lectotype.  MFGI,  Pl. 97  (Fig. 2 a, b),  

left valve. 

Lymnocardium soproniense was first described by I. Vitális 

(1934 a). Although this large bivalve species was very common 

in the brickyard claypits of Sopron/Ödenburg (Fig. 1), full and 

intact specimens were difficult to collect, thus Vitális chose to 

photograph a museum specimen; the depicted individual had 

been collected from the claypit of the Lenk brickyard (MFGI, 

Pl. 97., Fig. 2 a, b). Boda (1964) indicated this specimen as a 

“holotype”, but according to ICZN (1999, Art. 74.1 and 74.5), 

it represents the lectotype of the species.

The pictures published by Vitális (1934 a, b), however, were 

not the first representation of this species in the literature. 

Papp (1915) published the photograph of a L. soproniense 

specimen erroneously identified as “Limnocardium penslii 

Fuchs”  from  Szilágynagyfalu  (today  Nuşfalau,  Romania; 

Fig. 1), from sandy marl exposed in a trench cut into the hill-

side SE of the village.

In 1971, Mihaila and Marinescu described a Pannonian 

mollusc fauna from Sabolciu/Mezőszabolcs, valley of Crisul 

Repede/Sebes-Körös (Fig. 1), containing a new cockle  species 

Limnocardium (Pannonicardium) mihaili sp. n.”. The holo-

type and paratype specimens of the new species, however, 

were collected from the village of Felcheriu/Felkér by 

A. Mihai (after whom Mihaila and Marinescu named the new 

species). The authors regarded the Sabolciu specimens as 

 syntypes. Based on the description, drawing and photographs 

of  L. mihaili, the Felcheriu specimens fully correspond to  

L. soproniense

Subsequent picture representations of L. soproniense 

include a left valve (Bartha 1971) and a right valve of an arti-

culated specimen (Magyar et al. 2007, p. 281), both from 


Fig. 1. Localities of Lymnocardium soproniense in the northern Pannonian Basin. 1 — confirmed occurrence; 2 — uncertain occurrence;  

3 — no occurrence (mistaken identifications in the literature). Inset map shows a zoomed detail of the study area south of Miskolc.

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, 2016, 67, 6, 561 – 571

Fig. 2. Specimens of Lymnocardium soproniense from Sopron (a–i) and Mályi (j–l). a–d — a left valve (a,b; MFGI Pl. 97, lectotype of  

the species) and a right valve (c,d; MFGI Pl. 6361) from Sopron, Lenk brickyard, donated to the Hungarian Royal Geological Institute by  

L. Károlyi in 1914; e, f — a left valve depicted (and probably collected) by Bartha (1971) from Sopron, Balfi út brickyard (MFGI Pl. 2016.1.1); 

g — a right valve of a juvenile specimen from Sopron (TTM-BTM 2014-123-1); h, i — a right valve from Sopron (TTM M57/815);  

j, k — a left valve from Mályi brickyard (collection of I. Cziczer); l — a partial shell and “steinkern” of an articulated specimen from Mályi 

(collection of I. Cziczer). Scale bars 1 cm.

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, 2016, 67, 6, 561 – 571

Type locality and type stratum. Sopron/Ödenburg, 

 Hungary, Szák Formation, Upper Miocene, Pannonian Stage. 

The brickyard claypits of Sopron, mentioned by Vitális 

(1934 a, b, 1951), have been closed and re-cultivated by today. 

The only outcrop which was described in some detail in the 

geological literature is the Balfi út claypit. Stratigraphic 

 columns of the outcrop were given by Bartha (1971), Korpás-

Hódi (1994), and most recently by Barna et al. (2010). Accor-

ding to the latter, the lower 4.5 m of the more than 10 m high 

outcrop consisted of greyish-blue bioturbated clay with 

 variable silt content and dispersed molluscan shells. Silt con-

tent gradually increased from 4.5 to 9 m, and this interval con-

sisted of rhythmic depositions of clay, silt, and very fine sand. 

Parallel lamination, cross-lamination, small-scale graded 

 bed ding and plant remains were common in the fine sand and 

silt. The fine-grained sequence was capped by coarse-grained 

silt, sand, and fine-grained gravel layers that displayed 

cross-bedding, cross-lamination, and scour-and-fill structures 

and erosional surfaces. The entire sequence was interpreted as 

reflecting the transition from a sublittoral lacustrine environ-

ment to a distributary channel and mouth bar (Barna et al. 

2010). According to Bartha (1971, p. 100), Lymnocardium 

soproniense occurred in the lower, clayey part of the section 

(Szák Formation).

Comparison.  Lymnocardium soproniense is morphologi-

cally very close to L. schedelianum (Fuchs), and also to  

L. variocostatum Vitális. When they are preserved as internal 

moulds (steinkerns), it is very difficult or sometimes impossible 

to tell the three species apart. The diagnostic difference is in 

their rib architecture (Fig. 3). L. schedelianum has prominent 

radial ribs (Fig. 3a). In L. soproniense, the ribs are not promi-

nent but quite flat, and the intercostal spaces are filled with 

shell material so that they are even with the ribs, giving  

the entire shell a smooth appearance (Fig. 3b). In L. vario­

costatum, the ribs in the central and rear areas of the valve  

are wide and flat, and the intercostal spaces are reduced to  

a shallow groove (Fig. 3c).

Remarks. Prior to the description of Lymnocardium 

soproniense as a new species by Vitális (1934a), its specimens 

were identified as, or were considered to have been related to, 

various other large Lake Pannon cockles. For instance, the 

specimens collected by L. Roth in Balf were first labelled  

as “Cardium schmidti (Hörnes)”. Later the curator of 


the museum of the Hungarian Royal Geological Institute,  

Gy. Halaváts, corrected the labels of these specimens to   

L. dumicici Gorjanovic-Kramberger” (see in Vitális 1934 a, 

p. 707). Papp (1915) described his L. soproniense specimen 

from Szilágynagyfalu as L. penslii (Fuchs). Even after Vitális 

described L. soproniense as a new species, and discussed all 

the morphological traits that distinguish L. soproniense from 

L. schmidtiL. croaticum (Brusina), and L. dumicici, Strausz 

(1942) expressed his opinion that L. soproniense is identical to 

L. variocostatum Vitális, which is, according to him, a sub-

species of L. penslii. Mihaila and Marinescu (1971) assigned 

L. mihailii (= L. soproniense) into Pannonicardium, a   sub genus 

erected by Stevanović (1951) for L. dumicici, L. schmidti, and 

L. penslii. On the other hand, A. Papp (1953) thought that  

L. soproniense is very closely related to L. schedelianum

therefore he regarded Sopron/Ödenburg as a L.  schede lianum-

bearing locality (Papp 1953, p.198). 

Distribution. The localities where Lymnocardium 

soproniense has been found so far are clustered in several 

areas in the northern part of the Pannonian Basin (Fig. 1).  

The most abundant material is from Sopron and its vicinity. 

The second-richest material was collected from the SE margin 

of the Bükk Mts., northern Hungary (in the vicinity of 

 Miskolc). A few specimens have been documented from three 

localities in the northwestern foreland of the Apuseni Mts. in 

Romania (vicinity of Oradea/Nagyvárad). Finally, museum 

materials indicate occurrences of the species in Budapest and 

in the Balaton region, but these are considered uncertain and 

require future confirmation (see Appendix).

Lymnocardium soproniense in the Mályi outcrop

The claypit of Mályi brickyard

The only outcrop known to us where Lymnocardium 

soproniense-bearing sediments are exposed today is the 

 brickyard claypit of Mályi in the vicinity of Miskolc, northern 

 Hungary. The outcrop, located in the northern outskirts of the 

village, exposes a 20–25 m thick homogeneous,  bluish-grey, 

fossiliferous clay/argillaceous marl, overlain rather sharply by 

a coarsening upward series of white, fine sand, gravelly sand, 

and conglomerate (Fig. 4). The clay is fully  bioturbated; the 

only indication of bedding is represented by accumulations of 

randomly oriented mollusk shells, first of all dis articulated 

valves of small (juvenile) individuals of  Congeria czjzeki 

Hörnes. Many of these beds are poorly cemented with iron 

oxide-hydroxides, and limonitic concretions also occur with 

shells in their cores. These beds do not contain sand, gravel or 

any other coarse material that would indicate vigorous  currents, 

therefore the varying  abundance of shells is probably related to 

the original living conditions rather than post- mortem transport 

and accumu lation. Scattered shells also occur in the clay; most 

of the large L. soproniense and  

Congeria ungulacaprae 

 Münster specimens were found in such position. The abun-

dance of molluscs apparently decreases upwards. The upper-

most 2 m of the clayey interval is grey- yellow variegated clay, 

overlain by 2 m yellow siltstone. This change in colour is 

related to ground waters percolating in the overlying sand. 

Fig. 3. Rib structure of Lymnocardium schedelianum (A; Wien- 

Hennersdorf, TTM), Lymnocardium soproniense (B; Sopron, MFGI), 

and L. variocostatum (C; Bicske, TTM-BTM). Scale bars represent  

5 mm.

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, 2016, 67, 6, 561 – 571

The transition of silt to sand was covered by debris in the 

outcrop, but morphology of the terraces suggests a sharp tran-

sition. The white, fine-grained sand is moderately to well-

sorted, attaining a total thickness of 20 m. Much of the sand 

lacks structure, mostly due to bioturbation. Plane lamination, 

cross-lamination, decimetre-scale cross-bedding, shallow and 

wide erosional scours rarely occur. The scours and cross- 

bedding are paved by granule to small-grained pebbles. The 

abundance and thickness of these cm-scale pebbly layers 

increase upwards. Some small, v-shaped burrows, large 

 pebble-filled vertical burrows, carbonaceous material (wood 

fragments) and granule-size rip-up mud clasts also can be 

found. The uppermost metres of the outcrop consists of pebbly 

sand and sandy gravel, made up of well-rounded “pearl” gravel.

The clay was deposited from suspension settling in quiet 

offshore conditions (i.e. below storm wave-base). The over-

lying sands and gravels are products of shallow, nearshore 

waters above wave-base. Most of the structures indicate 

 shallow currents, but the swash-zone of breaking waves is also 

clearly demonstrated. We cannot distinguish deposits of a pro-

grading wave-dominated coast from those of a small, coarse-

grained deltaic lobe. No large-scale architecture (i.e. foresets) 

support the latter. The sharp transition reveals a pronounced 

shift of facies from offshore to nearshore (i.e. a regression).  

It points to a drastically increased rate of sediment input, 

which can be the result of either development of a delta entry 

nearby or a lake-level fall (or their combined effect). The clay 

is assigned to the Szák Formation (see Cziczer et al. 2009 and 

references therein), whereas the gravelly white sand belongs 

to the Kálla Formation (see Csillag et al. 2010 and references 


Palaeoecological interpretation

Environment. In the Mályi outcrop, the shells of Lymno­

cardium soproniense are most common in the lower layers 

that were deposited in a distal offshore environment. The 

unstratified, bioturbated clay was deposited from suspension 

in the sublittoral zone of Lake Pannon, which means below the 

storm wave-base. Shells are usually found with articulated 

valves, either in closed or open position (Fig. 4c). There are no 

indications of storm- or gravity-induced currents, a fact that 

may point to a flat depositional surface far away from sedi-

ment input. Water depth is difficult to reconstruct, but studies 

of the Szák Formation elsewhere and comparisons with the 

present-day Caspian Sea as an analogue of Lake Pannon sug-

gest that the sublittoral argillaceous marl was deposited at 

20–30 to ?80 m water depth (Korpás-Hódi 1983; Cziczer et al. 

2009). L. soproniense becomes less common and finally dis-

appears from the record as sediment input increased and water 

depth decreased up to and even above the wave-base.

Accompanying species. The most common accompanying 

mollusc species in Mályi include Congeria czjzekiC. ungula­

caprae,  Lymnocardium brunnense Andrusov,  Caladacna 

steindachneri (Brusina), and Pisidium krambergeri (Brusina) 

Fig. 4. Stratigraphic column of the Mályi outcrop. a — cross- and 

plane lamination with small vertical burrows in fine-grained sand;  

b — trough cross-bedding in sand, pebbly sand points to south-

ward transport; c — articulated valves of Lymnocardium soproniense

embedded into clay in life position; d — shell-bed with Congeria 

czjzeki in the blue clay. Spade is 10 × 22 cm for scale (a, b).

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, 2016, 67, 6, 561 – 571

(Fig. 5). The first three of these are also common at other 

localities in the vicinity of Miskolc and Sopron. In particular, 

C. czjzeki is known to be a characteristic form of sublittoral 

deposits. In the Sopron area, Balfi út outcrop, dominance of 

candoniid ostracods over cypridiids in the lower layers of the 

section also indicates a deeper water, offshore environment 

(Barna et al. 2010). All these patterns confirm that 


L. soproniense was a sublittoral dweller.

Stable isotope records of Lymnocardium soproniense 

and closely related species

Ontogenetic ages and growth rates


Recent stable isotope work on various Lymnocardium 

 species  including  L. soproniense offers additional palaeoenvi-

ronmental data as well as information about the longevity and 

growth rate of L. soproniense and its relatives (Johnson 2016). 

Stable oxygen isotope profiles in mollusc shells typically 

 consist of quasi-sinusoidal patterns that have been interpreted 

as annual cycles (e.g., Dettman & Lohmann 1993; Dettman et 

al. 1999; Andreasson & Schmitz 2000; Goodwin et al. 2001; 

Schmitz & Andreasson 2001; Ivany et al. 2004; Ivany & 

 Runnegar 2010). Winters are recognized from high δ


O ratios, 

whereas summers produce low δ


O ratios.  

The profile of a large (~ 90 mm in height) Lymnocardium 

soproniense from Sopron (Fig. 6) contains ~ 10 winter- summer 

cycles, indicating at least 10 years of growth (Johnson 2016). 

Shell growth may slow or stop seasonally if temperatures 

exceed the tolerances of the species, or during a reproductive 

event when the animal reallocates resources (Dettman et al. 

1999). The seasonal signal may also be obscured by low 

 seasonality of the ambient temperature — potentially buffered 

by depth — and/or seasonality in the δ


O values of lake water, 

which may destructively interfere with temperature effects. 

Later in ontogeny, the growth rate slows, which makes it more 

difficult to detect annual cycles using isotopes due to 

Fig. 5. Mollusc species accompanying Lymnocardium soproniense in the Mályi outcrop. a,b — Congeria ungulacaprae Münster; c–f — Congeria 

czjzeki Hörnes; g–j — Lymnocardium brunnense Andrusov; k — Caladacna steindachneri (Brusina); l — Pisidium krambergeri (Brusina).  

All specimens are from the collection of I. Cziczer. Scale bars 1 cm.

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, 2016, 67, 6, 561 – 571

time- averaging of samples (Goodwin et al. 2001, 2003). 

High-resolution microsampling can mitigate this time- 

averaging by greatly increasing the sampling density  (Dettman 

et al. 1999; Patterson & Cheatham 1999; Surge et al. 2001; 

Wurster & Patterson 2001; Schöne et al. 2004, 2005; Ivany & 

Runnegar 2010), but these methods require time and resources 

not available in the collection of these data (Johnson 2016). 

Given these considerations, 10 years is a mini mum onto-

genetic age of the Sopron shell. Maximum rate of growth for 

the Sopron shell was 16 mm/yr based on the best-preserved 

year within the shell.

The growth rates and ontogenetic ages of the two most 

closely related cockle species, Lymnocardium schedelianum 

and L. variocostatum, have been estimated and compared to  

L. soproniense using the same method (Fig. 7; Johnson 2016). 

The studied shells of L. schedelianum are smaller (~ 40 mm in 

height) and have a maximum growth rate of 17 mm/yr based 

on the best-resolved year from 5 individuals. The studied  

L. variocostatum is of similar size to L. soproniense, although 

the shell presented here was broken near the umbo. Because  

of this breakage, the initial ~ 30 mm of shell is missing. The 

complete individual should be ~ 80 mm in height. The best- 

preserved year from this specimen indicates a growth rate of 

13 mm/yr. Among these three species, body size and growth 

rate appear unrelated.  

Ontogenetic age and body size do seem to be related among 

Lymnocardium soproniense,  L. schedelianum, and L. vario­

costatum (Johnson 2016). The smaller L. schedelianum have 

the shortest lifespan, with only 2 to 4 years detected by isotope 

analysis. Although the L. variocostatum shell was broken,  

6 years were detected in 53 mm of shell growth; a complete 

specimen would likely contain ~ 8 years. L. soproniense, the 

largest specimen, appears to have the longest lifespan (at least 

10 years).  

Geary et al. (2012) observed that the Pannonian snail 

 Melanopsis also seemed to achieve increased body size 

through increased longevity. They proposed that the repro-

ductive advantage of larger body size coupled with an increase 

in resource availability and/or a decrease in predation drove 

this evolutionary trend in Melanopsis. Perhaps lymnocardiids 

were also able to take advantage of a stable lake environment 

by undergoing more reproductive events and at larger body 

size via longer lifespans (Johnson 2016).

Palaeoenvironmental interpretation

Environmental conditions are reflected in the stable oxygen 

isotope composition of shell carbonate. The amplitude or 

intrashell range in δ


O values is related to seasonal variations 

in  temperature  and  δ




, although these factors can be 

 difficult to distinguish (Dettman & Lohmann 1993; Ivany et 

al. 2004) especially from a single shell. Mean shell values, 

however, are useful for habitat comparisons. For example, in 

closed  lakes  there  is  a  gradient  in  δ


O values from lower 

 values near-shore (under the influence of freshwater) to higher 

values off-shore (where water is better mixed and more 

evaporated) (Talbot 1990; Goodwin et al. 2003). This contrast 

is  observed  between  high  mean  δ


O values of sublittoral 


ymnocardium schedelianum  (– 1.6  to  – 1.0  ‰)  and  lower 

mean values of littoral L. variocostatum  (– 5.4  to  – 2.8  ‰).   

L. soproniense has a mean δ


O value of – 1.2 ‰, which is very 

similar to that of L. schedelianum, and supports a similar sub-

littoral habitat (Fig. 8).

Phylogeny and stratigraphy

Stratigraphic record of Lymnocardium soproniense and  

its relatives

Of the closely related species of Lymnocardium schedelia­

num, L. soproniense, and L. variocostatumL. schedelianum 

Fig. 6. Stable oxygen isotope profile of Lymnocardium soproniense 

from Sopron (MTM, M.571815) arranged with ontogenetically 

youngest values at left, and oldest values at right (Johnson 2016). 

Arrows indicate local maxima, interpreted as winter signals.

Fig. 7. Stable oxygen isotope profiles of Lymnocardium schedelianum 

from Wien-Vösendorf (NHMW coll.), L. soproniense from Sopron 

(MTM, M. 571815), and L. variocostatum from Dáka (private 

 collection). Profiles are arranged with ontogenetically youngest 

 values at left, and oldest at right. The profile of L. variocostatum is 

incomplete due to missing shell. Modified from Johnson (2016).

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, 2016, 67, 6, 561 – 571

appears first in the stratigraphic record. Its oldest occurrences 

are known from the well-studied outcrops of southern Vienna 

(Vösendorf, Hennersdorf, Laaerberg; Papp 1953), where it 

occurs both in sublittoral clays and in sandy shoreface deposits 

(Papp 1951; Schultz 2003). Based on the evaluation of their 

vertebrate fossils, these layers are correlated with the middle 

part of Zone MN9, and dated about 10.4 Ma (Harzhauser et al. 

2004; Fig. 9). 

Lymnocardium soproniense enters the fossil record some-

what later, and it is restricted to sublittoral clays. 


from the overlying littoral deposits in Sopron and its vicinity 

contain a series of species that are common in younger deposits 

but missing in the Vienna basin, and vertebrates from the same 

deposits indicate uppermost MN9 to lowermost MN10 Zones 

(Harzhauser et al. 2004). Based on the normal magnetic polarity 

measured in the Balfi út claypit, the Sopron occurrence of  

L. soproniense is thus correlated with the upper part of C5n, 

and dated about 10 Ma (Magyar et al. 2007; Fig. 9). 


rently,  L. soproniense replaced L. schedelianum in the sub-

littoral zone of Lake Pannon about 10.2 – 10.3 Ma, and from 

that time the latter became confined to the littoral zone. In 

eastern Austria (Burgenland), L. schedelianum occurs in the 

littoral deposits (e.g., Oggau, Grösshöflein; Magyar et al. 

2000), whereas L. soproniense characterizes the coeval sub-

littoral sediments (Sopron; Fig. 9).

Finally, Lymnocardium variocostatum is known from litto-

ral sands, correlated with Zone MN10, and dated roughly 

9.5 – 9.0 Ma (Lymnocardium ponticum zone; Szilaj et al. 1999; 

Magyar et al. 2000, 2007). This species seems to have replaced 

L. schedelianum in the littoral zone of Lake Pannon at some 

time between 9.7 and 9.5 Ma (Fig. 9).

Evolutionary history of the Lymnocardium soproniense lineage

Based on the stratigraphic and palaeoecological patterns 

discussed above, the following scenario is considered most 

probable for the phylogenetic relationship of the three species. 

A sympatric speciation event in Lymnocardium schedelianum 

led to the appearance of L. soproniense in the sublittoral zone 

of Lake Pannon, and subsequent habitat partitioning between 

L. soproniense and L. schedelianum; the first was confined to 

the sublittoral, whereas the latter was limited to the littoral 

zone of the lake. Later, the now littoral L. schedelianum 

evolved into L. variocostatum, possibly anagenetically, as no 

common occurrence of the two species has been found so far 

(Fig. 9).

Definition of the Lymnocardium soproniense Interval Zone

Although Lymnocardium soproniense is not a very common 

species, it appears in widespread localities of the Pannonian 

Basin, apparently with very similar accompanying fauna. This 

feature makes it a valuable biostratigraphic marker, therefore 

its first occurrence is used to define the base of the 


L. soproniense mollusc zone in the sublittoral sediments of Lake 

Pannon (Magyar et al. 1999, 2007; Magyar & Geary 2012). 

The last occurrence of Lymnocardium soproniense in the 

stratigraphic record is more difficult to establish. The age of 

the  uncertain  Budapest  occurrences  is  estimated  at  8 – 9  Ma 

(Magyar et al. 2006). For practical reasons we suggest  marking 

the top of the L. soproniense Zone with the base of the over-

lying  Congeria praer

homboidea Zone, defined by the first 

appearance datum of C. praerhomboidea at ca. 8.9 Ma 

Fig. 8. Mean and range of within-shell δ


O values of Lymnocardium 

schedelianum (NHMW coll.), L. soproniense (MTM, M. 571815), 

and L. variocostatum (private coll.). Data are arranged by species (at 

bottom) and locality (at top), and do not necessarily indicate relative 

stratigraphic positions. Both L. variocostatum shells were incomplete, 

potentially affecting within-shell range. Data from Johnson (2016).

Fig. 9. Stratigraphic correlation of the Lymnocardium soproniense 

Interval Zone to the Geomagnetic Polarity Time Scale and the 

 European mammal zonation (Hilgen et al. 2012). L sch — L. schede­

lianumL sop — L. sopronienseL var — L. variocostatum.

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, 2016, 67, 6, 561 – 571

 (Magyar et al. 1999; Magyar & Geary 2012), regardless of 

whether L. soproniense itself occurs in younger deposits or not 

(Fig. 9). 


Lymnocardium soproniense was a Late Miocene brackish- 

water cockle living in the quiet offshore environment of Lake 

Pannon. It evolved from L. schedelianum  some  10.2 – 10.3 

million years ago by attaining larger size and increased 

 longevity (>10 years). The species was widely distributed in 

the northern part of the Pannonian basin, and it is well repre-

sented in museum collections. Although full and intact speci-

mens of this fossil are rare, it can be distinguished from other 

species even when found in small fragments. Consequently, it 

is a good biostratigraphic marker in the sublittoral deposits of 

Lake Pannon. 

Acknowledgements: Lajos Katona (TTM-BTM) is thanked 

for photographs of specimens from the collections of MFGI 

and TTM. Tímea Szlepák (MFGI Library) helped the authors 

to identifiy the first original description of L. soproniense

Reviews by Oleg Mandic (NHMW) and an anonymous 

reviewer have substantially improved the original version of 

the manuscript. Mathias Harzhauser (NHMW) and Alfred 

Dulai (TTM) are thanked for permitting destructive sampling 

on fossil bivalve shells. This research was supported by the 

Hungarian Research Fund 81530 and National Research, 

Development and Innovation Office — NKFIH 116618. This 

is MTA-MTM-ELTE Paleo contribution No 227.


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, 2016, 67, 6, 561 – 571

Review of collection and literature data on the 

 distribution  of  Lymnocardium soproniense

Sopron / Ödenburg and Vicinity

There are many specimens of Lymnocardium soproniense from 

various claypits of Sopron and from a well in Balf (17 m depth 

from the surface) in the collection of the MFGI, obtained between 

1872 and 1971. This material includes a beautiful pair of valves 

from Sopron, Lenk brickyard, donated to the institute by 


L. Károlyi in 1914 (the original label of these  specimens was 

 written and signed by L. Roth). The left valve is the type of the 

species  (Pl.  97;  Fig.  2 a, b),  photographed  by Vitális  (1934 a, b), 

whereas the right valve is slightly damaged and partly filled with 

sediment (or glue?) in the inner part (Pl. 6361; Fig. 2 c,d).  

The relatively large collection of F. Bartha from the Balfi út 


claypit contains an outstandingly well-preserved left valve 

 (Bartha 1971; Pl. 2016.1.1; Fig. 2 e, f), along with some large and 

quite complete but sediment-filled specimens (Pl. 6336, 6337, 

6354, 6355, 6359) and many shell fragments (Pl. 6332, 6341, 

6344, 6345, 6347). 

 The Hungarian Natural History Museum (TTM) also has  

a relatively large collection of L. soproniense from Sopron, 

including specimens that were purchased from the legacy of  

I. Vitális (M57/807-817, M64/1200). In this material, however, 

there is only one right valve which is a complete and fully cleaned 

specimen (M57/815; Fig. 2 h,i). The Bakony Natural History 

Museum (TTM-BTM) in Zirc also houses a few nice though not 

fully intact specimens (Fig. 2 g). 

Vicinity of Miskolc 

While mapping the southwestern hilly region of the Bükk Mts. 

between 1932 and 1934, Z. Schréter, geologist of the Hungarian 

Royal Geological Institute, collected fossils from shallow test 

holes (Schréter 1939) and deposited them in the MFGI collection. 

The best-preserved specimens are from Bükkaranyos (MFGI  

Pl. 4535, Pl. 4613, Pl. 4614); although the shells are broken and 

dissolved, the diagnostic rib pattern of Lymnocardium soproniense 

can be recognized in some of them. However, specimens from 

Borsodgeszt (Pl. 4627), Harsány (without inventory number), 

Sály (Pl. 4569), and Mályi (Pl. 4602) are poorly preserved; the 

shells are usually partly or entirely dissolved. They are identified 

as L. cf. soproniense (Schréter 1939, p. 520; Fig. 1).

Better-preserved specimens in the area were collected after the 

brickyard claypit in Mályi was opened. Apart from a stein kern  

(L.  cf.  soproniense, Pl. 4603), the museums have shelly speci-

mens from this outcrop (Pl. 6438 and a specimen without inven-

tory number in the collection of the MFGI; M. 68.32 in the  

collection of the TTM; and several specimens in the  private 


collection of I. Cziczer, including an intact left valve 


(Fig. 2 j, k).

Bartha (1971) mentioned the occurrence of L. soproniense from 

Alsódobsza, but these specimens, deposited in the collection of 

the MFGI, belong to L. schedelianum (Fig. 1).

Vicinity of Oradea/Nagyvárad

We have no information on the whereabouts of Papp’s (1915) 

specimen  from  Nuşfalau.  Mihaila  and  Marinescu  (1971)  claim 

that the holotype of Lymnocardium mihaili from Felcheriu is 

reposited in the Geological Institute in Bucharest, but no  mention 

is made of the whereabouts of fossils collected by Mihaila and 

determined by Marinescu from Sabolciu (Mihaila and Marinescu 

1971). As the latter material has not been depicted, we cannot 

confirm the presence of L. soproniense in Sabolciu (Fig. 1).


In the TTM collection, there is a beautiful specimen of 

 Lymnocardium soproniense (M57/38) preserved in clay with 

 double and open valves. According to the label and the  original 

sticker on the specimen, it was collected by Ferenc Kubinyi in 

1849 from Budapest-Rákos. This locality and the immediately 

neighbouring  Kőbánya  outcrops  are  well-known  from  the 

 palaeontological literature (see Magyar et al. 2006 and refe rences 

therein), but no mention is made of fossils that could be identified 

with L. soproniense

In the collection of the MFGI, however, there are two speci-

mens  from  Budapest-Kőbánya  (Pl. 2864),  determined  as 

 “Limnocardium cfr. schmidti” by Bartha, that might be related to 

L. soproniense. Both specimens are articulated valves; one is a 

steinkern, the other with shells but compressed and  broken.  

The latter has 18 ribs, the structure of which resembles that of  

L. soproniense.  

This scarce material indicates that L. soproniense might have 

lived in the area, but further data are needed to strengthen that 

claim (Fig. 1).


Bartha (1971, p. 101) reported Lymnocardium soproniense 

from  the  Kisapáti-2  borehole  at  18 – 35  m  depth  (Fig.  1).  

The core sample (18.50 – 18.70 m) is deposited in the  collection of 

the MFGI (Pl. 6327). It contains Congeria czjzeki  specimens and 

a poorly preserved fragment of a large Lymnocardium  species in 

fine-grained sediments. The sediment and the accompanying 


species make it probable that the large species is indeed 


L. soproniense, but its rib architecture is not visible, thus the 

determination remains highly uncertain.  

Magyar (1988) depicted large Lymnocardium moulds (stein-

kerns) from Mindszentkálla as “Lymnocardium cf. soproniense” 

(Fig. 1). Although the preservation of these fossils, deposited in 

the TTM, does not allow distinction between L. soproniense and 

the closely related species L. variocostatum and L. schedelianum

the accompanying species — such as Congeria pancici Pavlović, 

Unio atavus Partschand   Mela nopsis  fossilis  (Martini-Gmelin) — 

as well as the shoreface depositional environment of the embed-

ding pebbly sandstone – suggest that these large cockles probably 

belong to L. schedelianum. The entire association is typical of  

a littoral “Burgenland fauna” (Magyar et al. 2000; Csillag et  

al. 2010).