The discovery of a dinosaur clutch in Upper Cretaceous tidal flat deposits
in the Tremp Formation in Biscarri, Isona (Lleida, Spain), provides insight
into the mode of life of some dinosaurs. The clutch occurs in grey marls t
hat were originally waterlogged, muddy sediments. The seven elongated eggs
are parallel to each other and with their long axis almost vertically orien
ted. A mound-nest is inferred in contrast to hole-nest described so far for
similar eggshell types. The permeability of the eggshell (oospecies Megalo
olithus siruguei) was highly enhanced by a braided network of multicanalicu
late pore canals. The nest style, eggshell porosity and tidal flat environm
ent point to a periaquatic habitat for these dinosaurs. A modern analogue o
ccurs in crocodiles, alligators and some birds living in periaquatic enviro
nments, with nesting on plant-mounds above waterlogged soils or even on flo
ating vegetation. (C) 2000 Elsevier Science B.V. All rights reserved.