Table 2. Hypotheses to explain the need for mineral mobilization in titanosaurs and how they cope with the evidence from Lo Hueco.

Hypothesis short-name	Low-density bone origin hypothesis	Predictions	Evidence-support
Pneumatic hypothesis	The low density bone of the osteoderms would be a by product of a pneumatization of the bone.	Bone similar to camellate bone.	N - the anatomical architecture of both types of bone is different.
Seasonal-changes hypothesis	The large hollow spaces of the osteoderms would result from mineral mobilization as an adaptation to extreme seasonal changes.	If the assemblage occured in an extremely seasonal environment, a majority of osteoderms should present large hollow spaces or signs of mineral mobilization (heavy remodeling and evidence of past hollow spaces)	N - osteoderms with low density bone are <50% of the sample which comes from an extremely seasonal environment. Past hollow spaces have not been identified either.
Aging hypothesis	The low density bone of the osteoderms would appear as a result of decalcification in older individuals.	Osteoderms with large internal hollow spaces associated with senescent individuals.	N - An osteoderm associated with large internal hollow spaces associated with a non senescent adult individual.
Oogenesis hypothesis	The low-density bone of the osteoderms is the result of the need of calcium for the formation of eggshells during oogenesis.	i) Osteoderms would be the only readily source for minerals in a titanosaur. ii) Osteoderms of comparable sizes (attributable to adult reproductive female and male titanosaurs) both compact and hollow. iii) Not a larger number of osteoderms with large hollow spaces (<50%), that is, those belonging to females in reproductive age.	Y - i) Osteoderms of comparable size classes from the same stratigraphic horizon are both hollow and compact. ii) A minority of osteoderms (3/10) have low density bone.

See discussion for a more in depth description of the hypotheses. Y = yes. N = no.