It happened from time to time that fish died with a full stomach at Miguasha and their last meal became fossilized with the rest of their remains.(100 kb)
These uncommon discoveries not only tell us about a predators preferred prey, they also provide valuable information about the anatomy of its digestive system.
Some predatory fish have been found with whole prey in their abdominal cavity, the most astounding example being a 19-cm long Homalacanthus
in the belly of a 46-cm long Eusthenopteron
. Swallowed head first, the Homalacanthus
accounts for 40% of the predators body length, indicating the great extent to which its digestive tract could expand. Although impossible to know for certain, the death of this predator may have been due to the enormous size of its meal!
Some species apparently did not hesitate to eat smaller members of their own kind. For example, a Cheirolepis
was found within the abdomen of another Cheirolepis
, and two Eusthenopteron
were observed inside two larger individuals. These are undoubtedly among the oldest cases of vertebrate cannibalism.
Stomach contents in the dipnoan fish Scaumenacia
are also quite telling. It fed primarily on small invertebrates, with up to thousands of the small crustacean Asmusia
apparently the only species ever ingested in its digestive tube.
Even in the absence of stomach contents, the outlines of digestive systems are sometimes visible in the agnathans Euphanerops
, and the sediment-filled digestive system has been preserved in the form of a cast in several specimens of Bothriolepis
. With a ventrally positioned mouth, Bothriolepis
fed itself by filtering mud at the bottom of the estuary, and a belly full of sediment helped fossilize its intestinal system. Internal casts, observable in some Bothriolepis
specimens once cut into sections, display a concentric spiral like that observed in the intestines of modern day sharks, and is considered to be primitive gnathostome (jawed fish) morphology. Plant fragments in the cololite of a Bothriolepis
specimen suggest that plants may have been part of its diet. Cololites are petrified intestinal contents, and the word comes from the Greek kolon
for intestine, and lithos for rock.