Assertion: marsupial | /r/HasProperty | difficult to distinguish
Facets:
Source sentences:
text: Marsupials are difficult to distinguish from other fossils, as they are characterized by aspects of the reproductive system which do not normally fossilize (including pouches) and by subtle changes in the bone and tooth structure that show a metatherian is part of the marsupial crown group (the most exclusive group that contains all living marsupials).