Associations of corals and boring bivalves since the late cretaceous |
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Authors: | Dr Karl Kleemann |
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Institution: | 1. Institut für Pal?ontologie der Universit?t Wien, Universit?tsstr. 7, A-1010, Wien
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Abstract: | Summary The fossil record of coral and boring mytilid bivalves IS investigated. Middle Miocene associations from Austria, Hungary,
and Turkey are described. As host corals,Montastrea, Porites, Siderastrea, Solenastrea, andTarbellastraea can be noted. Eocene (Waschberg Zone) and Upper Cretaceous (Gosau Formation) examples are presented from Austria only. As
host corals,Favia andMontastrea, respectivelyAstrocoenia and an unidentified branching coral are recorded.
The associated bivalve species are all mytilidLithophaga, includingL. laevigata (Quoy & Gaimard) inTarbellastraea, a new Middle Miocene species inMontastrea, andL. alpina (Zittel) inAstrocoenia, the latter two from Styria, Austria.
Thecharacteristic features of the coral-bivalve relationships include (in massive corals): Boreholes more or less in the direction
of coral growth, radially arranged, elongate boreholes, produced by keeping pace with coral growth. Bivalves were not only
present near the surface, but deep inside the skeleton, representing successive generations in the same host colony. After
the death of borers, their tunnels were closed by coral overgrowth. Cup-shaped false floors in the boreholes are correlated
to reduced coral growth, indicating individual longevity of bivalves. The spacing of the floors mirrors the growth rate of
the host coral (like its density bands), their number representing the minimal age of the respective bivalve.
In branching corals, boreholes of the associated smallsizedLithophaga tended to turn into the axes of branchlets, when space was limited. Elongated boreholes and false floors were usually not
developed, as bivalve growth obviously exceeded lateral growth of branchlets and specimens were rather short-lived.
References to probable associations of coral and mytilid boring bivalves are given. It is quite likely that they have occurred
since Jurassic times and probably since the Upper Triassic. So far, they have been ascertained since the Upper Cretaceous
in massive and branching corals. |
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Keywords: | Coral-bivalveassociations Lithophaga-Boring Latecretaceous Eocene Miocene |
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