Assertion: skeletal system | /r/HasAspect | three types
Facets:
value: commonly
type: TEMPORAL
Source sentences:
text: Skeletal systems are commonly divided into three types—external (an exoskeleton), internal (an endoskeleton), and fluid based (a hydrostatic skeleton), although hydrostatic skeletal systems may be classified separately from the other two, because they lack hardened support structures.