Environmental differentiation reflected by vertebrate faunal diversity in the Lower Devonian of the Holy Cross Mountains, Poland

The Lower De vo nian of the Holy Cross Moun tains is well-known in the field of ver te brate palae on tol ogy but re mains un rec og - nized as re gards palaeoenvironmental reconstructions. We therefore analysed the spatial distribution and relative abun-dance of fos sil ver te brates in this area within one time in ter val. The fauna from an Early De vo nian (Emsian) siliciclastic bone-bear ing brec cia (the "Placoderm Sand stone") ex posed in four sec tions of the ysogory pound re gion and five sec tions of the Kielce re gion was ana lysed with re spect to the fre quency of the re mains and their tax o nomic af fin ity. The rel a tive abun - dances of agnathans, ac an tho dians, placoderms, osteichthyans and chondrichthyans sug gest more open ma rine con di tions in the ysogory pound re gion and more ter res trial-in flu enced in the Kielce re gion dur ing the Emsian. The re sults show that the av er - age agnathan and ac an tho dian con tent of the ysogory pound re gion is sig nif i cantly larger than that in the Kielce re gion. On the other hand, there are rel a tively fewer osteichthyans in the ysogory pound re gion and a sig nif i cantly higher pro por tion of bony fishes was re corded in the fauna of the Kielce re gion. Placoderms are char ac ter ized by their gen er ally sim i lar fre quency in both re - gions and from site to site in each of them, though a greater abun dance was noted from the Kielce re gion. Like wise dif fer - ences in the pro por tions of par tic u lar groups in the Kielce region suggest a large variety of marginal-marine environments un der the in flu ence of fac tors that might have in cluded ma rine cur rents and vari able con di tions around a river mouth.