Dr. Éva Murai szerk.: Miscellanea Zoologica Hungarica 1. 1982 (Budapest, 1982)

Domokos, T.: Morphometrial study of the chronocline of Granaria frumentum (Draparnaud, 1801) (Gastropoda: Chondrinidae)

RESULTS Four illustrations depict and a table summarizes the results. The height data of mature specimens from the 3 localities of different ages can be seen in Fig. 1. The class interval of the height values is 0.3 mm. The most frequent frequency-values are about 25% in the samples. As a comparison, I also took direct measurements on the recent material from Kocsola. I presented the results on the same diagram. As can be seen, there is no difference in the modal values and there is only 0.2 mm difference in the medians. Moreover, it can be seen that the values obtained from the measurements are equalized and skewed towards greater values. The greater sample size of the 3. facies from Szabadhidvég, 180 specimens, made it possible to determine optimal sampling. Sampling is optimal if the parameters (H, W, H/W) from a certain sample of the statistical population agree with the parameters of that population (in this case it could not be more than 30 because of the low number of specimens from the other samples). In the histogram the results concerning the subset of 30 specimens were marked with different symbols. It can be seen from diagram lc

2 and the table that the modes of the subsets are identical, the height-values are little different in median (Me), but decidedly so in the range of measurement (A), and in standard deviation (Ö). Diagrams la-^ and la2 show that the recent specimens are not distributed normally, because the mode is skewed towards the larger specimens. In the case of the larger samples (lb, lc2> the distributions are however, normal (MoRíMe 0.2), though in the diagram based on a sample of 180 individuals the observed values in the class 7.6-7.9 mm are less than the expected values from the theoretical normal distribution. Selective inbedding is one of the possible explanations - this explanation is substantiated by the rough physical character of the deposit, and by the fact that in case of sample number 2., with impregnated fine deposit, there are nearly equal number of specimens in the different classes (IC3). Finally, mention must be made of the growth in shell height which occurred during the last 1 mill, years. A comparison of width data (W) may be seen in Fig. 2. The measurements taken by photographic method are skewed towards higher values. In agreement with the above notes, the width values of the specimens interlocated in clay show normal distribution in spite of the relatively low number of specimens (40). It is known that during evaluation of elongation index (H/W) from height and width data, reproducible results can be obtained with less number of specimens (DOMOKOS, 1979). Here, the difference between the direct and indicrect measurements noted for the former two parameters disappeared. The measure deviation consequent to enlargement was not obvious. The distribution of the population from Siittő was also normalized. In case of the population from Szabadhidvég (30^ - 3O2 - 3O3) I indicated the normal distribution with a dotted line. As it is shown, considerable deviations are found in larger classes. Deviations already appear in the case of subsets (subsets are marked with dots on diagram 30

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). The probable causes for this inadequancy are selective impregnation or redeposition. Probably the specimens with elongftion index of 2.4 and over 7.6 mm in height disappear in greater number during impregnation and redesposition. We can give exact explanation only on completion of actual-paleontological research. SUMMARY During morphometrical examination on Granaria frumentum (Draparnaud, 1801), the following results were obtained: 1) From the Villafranchium to present, changes in shell morphology took place in Granaria frumentum (Fig. 4). Namely, height (H) increases nearly 0.6 mm during about 1 million years. Naturally, the elongation index calculated from the height and width data (H/W) increased to nearly 0.15 value, in accordance with increase in the abovementioned character. Probably, evolution was accelerated during the Riss/Wiirm Interglacial. There was no tendency for increase in shell width. The thermophilous Granaria frumentum was distributed more southernaly during colder periods of the Pleistocene and Holocene. This shift in distribution did not affect its morphological changes and did not divert the direction of changes from its original tendency. 2) The present idea formed of the great variability of the species (SOÓS, 1959) is in need of revision. 3) During impregnation and fresh water redeposition (Szabadhidvég), probably selection occurred. The absence of specimens of certain H/W values are indicative of this. During subsequent examinations it will be necessary to compare the intact with detrital shells, to study