In the Sibley-Ahlquist taxonomy, the tubenoses were included in a greatly enlarged order "Ciconiiformes". This taxonomic treatment was almost certainly erroneous, but its assumption of a close evolutionary relationship with other "higher waterbirds" – such as loons (Gaviiformes) and penguins (Sphenisciformes) – appears to be correct. The procellariiforms are most closely related to penguins, having diverged from them about 60 million years ago.
In the Sibley-Ahlquist taxonomy, the tubenoses were included in a greatly enlarged order "Ciconiiformes". This taxonomic treatment was almost certainly erroneous, but its assumption of a close evolutionary relationship with other "higher waterbirds" – such as loons (Gaviiformes) and penguins (Sphenisciformes) – appears to be correct. The procellariiforms are most closely related to penguins, having diverged from them about 60 million years ago