A new species of Pycnodont, Nursallia tethysensis, is described from the Cenomanian of En Nammoura and Hgula (Lebanon). It is a rarely encountered member of the ichthyofauna in these two localities and represents the smallest-sized species ever described in the genus. The frontal is broad, rounded, with an almost vertical profile. The hypertrophied dermosupraoccipital bears small spines on its median line. The parietal does not contact the frontal. The dermopterotic and the frontal join by only a thin osseous bridge under the dermosupraoccipital and above the orbit. The ventral profile has a characteristic "V"-shape notch at the junction between the head and the abdomen. There are 31 to 33 vertebrae. Nursallia tethysensis shows a closer relationship with N. gutturosum from the Cenomanian of Morocco and Italy than with the other species of the genus. The particularly good state of preservation permits examination of the ultrastructure of the teeth, demonstrating the presence of dentinal canaliculii only in the radicular area of these teeth. The chemical composition of both the eyes (characterized by high sulphur content, presumably derived from the original proteins of this région) and the bones (constituted of hydroxy-apatite almost identical to the bone component of modern fishes) are proof of the complete conservation of the organic remains fossilized in the Lebanese Cenomanian limestones.
Nursallia tethysensis sp. nov., a new pycnodont fish (Neopterygii: †halecostomi) from the Cenomanian of Lebanon
CAPASSO, LUIGI;
2009-01-01
Abstract
A new species of Pycnodont, Nursallia tethysensis, is described from the Cenomanian of En Nammoura and Hgula (Lebanon). It is a rarely encountered member of the ichthyofauna in these two localities and represents the smallest-sized species ever described in the genus. The frontal is broad, rounded, with an almost vertical profile. The hypertrophied dermosupraoccipital bears small spines on its median line. The parietal does not contact the frontal. The dermopterotic and the frontal join by only a thin osseous bridge under the dermosupraoccipital and above the orbit. The ventral profile has a characteristic "V"-shape notch at the junction between the head and the abdomen. There are 31 to 33 vertebrae. Nursallia tethysensis shows a closer relationship with N. gutturosum from the Cenomanian of Morocco and Italy than with the other species of the genus. The particularly good state of preservation permits examination of the ultrastructure of the teeth, demonstrating the presence of dentinal canaliculii only in the radicular area of these teeth. The chemical composition of both the eyes (characterized by high sulphur content, presumably derived from the original proteins of this région) and the bones (constituted of hydroxy-apatite almost identical to the bone component of modern fishes) are proof of the complete conservation of the organic remains fossilized in the Lebanese Cenomanian limestones.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
