Protosuchus sp. z dolnej jury północnego obrzeżenia Gór Świętokrzyskich

Abstract

PROTOSUCHUS SP. FROM THE LOWER JURASSIC AT NORTHERN MARGIN OF THE HOLY CROSS MTS Summary The paper presents results of studies on skeleton of Protosuchus sp. from Hettangian rocks exposed at Gliniany Las near Końskie, at the easternmost margin of the Lower Liassic basin of Europe. This finding still remains unique in the Jurassic of Poland. The material was found in lower part of lagoon deposits (Pieńkowski, 1981, unpubl., 1983, 1984), representing upper part of the Przysucha Ore-bearing Formation - Upper Hettangian (Pieńkowski, oral inf.). It comprises eight skeletal elements preserved in a sandstone slab (Figs. 1, 2). The elements A, B, C, D, E, and F represent traces of the Protosuchus skeleton, the element H - a difficult to identify backbone fragment with shoulder blade, and the element G - probably an unidentifiable bone fragment. The elements A and B clearly display deformations, directions of which are shown in Fig. 5. The elements A and B represent an internal mold of skull (Figs. 3 - 5); the element A is a mold of muzzle with visible palatal structure. The palatal surface displays vomers, traces of long back premaxillary teeth. First maxillary teeth, separated from the back premaxillary ones by a long diastema, may be noted at the side of the trace, whereas the remaining teeth seem to be missing. The muzzle in narrow and bluntly ended. The element B represents internal mold of back part of the skull, longer and two and a half times wider than the muzzle, and the elements C and D - probably rectangular dorsal scutes pressed into vertebrae. The element E represents flattened tail vertebrae, and badly preserved element F - probably trace of left hind leg. The whole specimen is 54.3 cm long. Proportions of all the elements, shape of the skull (elements A and B), and position of teeth make possible assignation of the specimen to Protosuchus sp. but the preservation of the material renders specific identification hazardous. The genus Protosuchus was hitherto known from the Triassic only so its record at this locality gives further support for the Karaszewski (1975) hypothesis of existence of a separate paleozoogeographic province in this region in the Early Liassic. In that province there could survive groups of reptiles extinct in most parts of the world. Attention should be paid to the possibility to analyse structure of the palate in the specimen from the Gliniany Las locality as the structure in Protosuchia was unknown up to the present (see Steel, 1973). In the studied specimen, vomers separating internal naves are not shifted back and visible and secondary palate is lacking. According to Romer (1956), in the course of evolution of reptiles the internal naves have been shifted back and secondary palate appeared. Therefore, the lack of secondary palate in this genus seems to confirm the assumption that Protosuchia may be treated as evolutionary side-branch of Crocodylia. At the same time this type of palatal structure makes it possible to assume that these reptiles led a terrestial existence .in contrary to the general evolutionary trend of crocodiles.