Table 5. Major causes of error and their effects, which may not be mutually exclusive. An asterisk (*) indicates that effects may overlap among these factors.

Cause of bias	Resulting overestimation	Ref.
Unreasonable assumption of isometry between body and skeletal masses during extrapolation	Up to 100 to 150 tons	Fig. 3B
Use of modern whale regression when pachyostotic animals have more bones for body mass*	About 100 tons	Fig. 3B
Inclusion of whales with unusually light dry bone mass for body mass*	About 10 tons	Fig. 3B
Unexplained exclusion of data points from manatee data	10 to 20 tons	Fig. 3B
Low accuracy of the methods	Varies	Table 4
Use of mysticete tree that is not current	Small	Text
Body to skeletal mass ratio for large whales calculated using estimated rather than measured body mass*	Not quantifiable	Text
Assumption that Perucetus is accurately modeled based on Cynthiacetus	Not quantifiable	Text