A spectacularly preserved assemblage of microbial euendoliths, penetrating into skeletons
of growing scleractinian corals, has been recognized in Early Aptian (Early Cretaceous)
reef limestone of the Rara
̆
u Mountains (East Carpathians, NE Romania). Microboring
euendolithic filaments were found in five coral colonies of the suborder Microsolenina.
They remained in part well-preserved, often impregnated with iron oxides, which made
them visible even in strongly recrystallized parts of coral skeletons. Filaments of a wide
range of sizes (2–40
l
m in diameter) were concentrated within medium parts of coral
septa, oriented along the septa in the direction of the coral growth. The larger filaments
were tubular, occurring in bundles and branched into finer, often tapering branches.
Their behaviour and organization were quite similar to the modern euendolithic
siphonalean chlorophyte
Ostreobium
. Filament diameters exceeded those reported
for the modern species, but covered a similarly wide size range. Narrower frequently
branching filaments, 4–8
l
m in diameter, resemble distal branching patterns of modern
Ostreobium quekettii.
Some very thin filaments (ca. 1–2
l
m) observed within skeleton or
inside the large tubular filaments, sometimes associated with globular swellings, may
represent euendolithic fungi. The recrystallization of coral skeleton had limited effect
on preservation of euendoliths due to their impregnation with iron oxides; microbial
euendoliths were subjected to different taphonomic changes.
keywords in English:
Chlorophytes, Early Cretaceous, fungi, microbial euendoliths, Romania, scleractinian corals
affiliation:
Wydział Biologii i Nauk o Ziemi : Instytut Nauk Geologicznych