Birds

add to my other comment. The broad vs. deep aspect can be problematic in skeletons that have been eroded a lot. The keel is less durable at the outer margins and may have been broken or worn off.

Keeled breast bode from a bird. without depth or dimensions I can't speculate on the species other than guess that it is a sea bird. if it is broad and less deep maybe a pelican or cormorant, both in Pelicaniformes. The depth of the keel is most important since it suggests the width of the wing span. Large soaring birds have a much deeper keel than short winged birds.