SOME REPRESENTATIVES OF THE FAMILY PLEROPHYLLIDAE FROM THEPERMIAN-TRIASSIC BEDS OF DZHUL'FA
Title:
SOME REPRESENTATIVES OF THE FAMILY PLEROPHYLLIDAE FROM THEPERMIAN-TRIASSIC BEDS OF DZHUL'FA
Author:
Il'ina, T. G.
Appeared in:
International geology review
Paging:
Volume 6 (1964) nr. 9 pages 1604-1616
Year:
1964-09
Contents:
Essentially continuous marine sedimentation during the transition from Paleozoic to Mesozoic time is known to have occurred at only a few places in the world. At one of these, Dzhul'fa on the Araks River in the Transcaucasus, certain species of corals, brachiopods, and foraminifera persist from the uppermost Permian beds into the lowermost Triassic unit where they are associated with characteristic Early Triassic ammonoids. This study is based on more than 700 specimens of small solitary rugose corals assigned to two plerophyllid genera. The six species (including one with two sub-species) of Plerophyllym are new. Plerophyllum clavatum, P. excentricum, P. breviseptatum, and P. dzhulfense dzhulfense are confined to the Upper Permian; P. dzhulfense differentiatum occurs in both Upper Permian and Lower Triassic beds; and P. armenicum and P. cuneatum are from the Lower Triassic. A single species of Pleramplexus — P. leptoconicus (Abich) — was identified from both Upper Permian and Lower Triassic strata. This is the first time rugose corals have been described from post-Paleozoic rocks. The Late Permian species of Plerophyllum show considerable variation during ontogeny in the length of the cardinal septum, which tends to shorten in ephebic stages. This tendency became more pronounced in the Early Triassic forms, which are characterized also by acceleration of septa in the counter quadrants. Specimens identified as Pleramplexus leptoconicus (Abich) vary widely in form of corallum, orientation of curvature, dilation of septa, and development of the amplexoid stage. Helen Duncan
Journal description