Adaptive homoeomorphy in the brachiopods Tetractinella Bittner and Cheirothyris Rollier
- 47 Downloads
The Middle Triassic athyraceanTetractinella and the Upper Jurassic terebratellaceanCheirothyris show a close homoeomorphic resemblance in their external shell form. The homoeomorphy is here interpreted as the result of the parallel evolution of an identical adaptive device. Structurally, the homoeomorphy is due to the development of two pairs of long, narrow radial deflections of the commissure, and consequently of two pairs of marginal projections and radial costae on the shell. Functionally, these projections are interpreted as sensory “antennae”, which carried the sensitive mantle edges outwards beyond the rest of the shell, and hence provided the brachiopods with early warning of the approach of potentially harmful agents in the environment.
KeywordsJurassic Middle Triassic Growth Line Ventral Valve Dorsal Valve
Unable to display preview. Download preview PDF.
- Buckman, S. S. 1901. Homoeomorphy among Jurassic brachiopods. — Proc. Cotteswold Nat. Field Club,13, 231–290.Google Scholar
- Cloud, P. E., 1941. Homeomorphy, and a remarkable illustration. — Amer. J. Sci.,239, 899–904.Google Scholar
- George, T. N., 1962. The concept of homoeomorphy. — Proc. Geol. Assoc.,73, 9–64.Google Scholar
- Rudwick, M. J. S., 1959. The growth and form of brachiopod shells. — Geol. Mag.,96, 1–24.Google Scholar
- —, 1961b. The anchorage of articulate brachiopods on soft substrata. — Palaeontology,4, 475–476.Google Scholar
- Rudwick, M. J. S., 1964a. The function of zigzag deflections in the commissures of fossil brachiopods. Palaeontology,7, 135–171.Google Scholar