Assertion: dugong's calf | /r/HasProperty | twin
Facets:
value: rarely
type: DEGREE
Source sentences:
text: A single calf, rarely twins, is born after a gestation of 11 to 14 months and remains with its mother for another 18 to 24 months.
text: After a long gestation period of about 13.5 months the female will give birth to only one calf (very rarely twins).