36. Short Notes on the Excavation of the Ossiferous Fissures and Caves in Kuzuü during the Years 1931 to 1936

Abstract

The occurrence of a rich mammalian fauna in some of the limestone fissures and caves of Kuzuii in Aso-gun, Totigi-ken, came to the first time in 1930 to the notice of geologists ; since that time, the author repeated excavations of the ossuaries to the last year, with kind assistance of Mr. O. TANAKA, a resident in Kuzuii, to whom he is much obliged for facilitating the dangerous and difficult task of excavation and fossil collection. The laboratory work of fossils collected. is still in progress under the guidance of Prof. H. YABE in the Institute of Geology and Palaeontology, TOhoku Imperial University, Sendai, where all the materials obtained by excavation are deposited.
The fissure deposits of Kuzuü, the “Kuzuü formation” of the author, is divisible into three parts, lower, middle and upper. The lower Kuzuü formation consists of two fossil beds, the lower, Sus bed and the upper, Stegodon bed; the upper Kuzuü has seven, Geoclemys-, amphibia-, Palaeoloxodon-, Parastegodon-, Microtus-Mels-, carnivora-and Moschus beds in ascending order; and the middle Kuzuü is barren of fossils. In the present article only the Geoclemys-, amphibia-, Micraus-Meles-, carnivora- and Moschus beds of the upper Kuzuü are taken into consideration.
The fossil bones, teeth, antlers and shells procured by the author from Kuzuii during the pas six years amount to 4033 in number; they comprise 36 species of rnammalia, 5 species of ayes, 3 species of reptilia and 3 species of amphibia (anura), altogether representing more than 424 (or more) individuals in total. The actual number of samples and the estimated number of individuals (in parenthesis) of each species are given in Table 1; from this table one can get the general, though faint, idea of the numerical ratio of skeletal parts excavated of each species to the approximate individual numbers by estimation. In Table 2 are given only the estimated numbers of individuals of each species in order to show the relative population among the different species; perhaps this statistical method may serve for palaeoecological analyses of the fossils beds or consideration of the mechanism of the fossil entombment. In strict sense, of course, it is almost impossible to estimate the total number of specimens preserved in one ossuary, especially by intermittent excavaations in small scale as in the author's enterprise; yet his intention lies in knowing, if possible, the proportion in numerical value, though only in approximation, of the skeletal parts of different animals procured from each ossuary.
The specific elements of the fossil fauna under consideration are divided into the following three categories according to their frequency or population.
1. Dominant cements, in which the finds of the skeletal parts correspond to 20 individuals or more, and are found in all or at least in the majority of different ossuaries.
2. Subordinate elements of A type in which the finds of the skeletal parts correspond to less than 20 and more than 5 individuals and are found at least in the majority of the different ossuaries.
3. Subordinate elements of B type in which the finds of the skeletal parts corresponi to less than 5 individuals and are found in only a limited number of the ossuaries.
The dominant elements and subordinate ones of A type are listed in Table 3; most of them are fossorial in habit, and their skeletal parts are rather completely recovered. On the contrary, the subordinate elements of B type are known only of very few and fragmental remains.
The Kuzuiü ossiferous fissures, so far as the 5 fossil beds are concerned, are more or less like the Conard fissures in Arkansas, United States of America, in the constitution of fauna.