FIGURE 1. Multi-view skeletal profiles of both extinct and extant large to gigantic marine mammals in well-nourished condition, including chest cross-sections, are depicted at the same total midline length to facilitate visual comparisons of their absolute and relative dimensions and volumes: A, Perucetus colossus MUSM 3248 with cetacean-like soft tissue; B, same with sirenian-like soft tissue; C, Cynthiacetus peruvianus MNHN.F.PRU10; D, Balaenoptera musculus LML GOGA 1982; E, Balaenoptera physalus MSC Bp.140400; F, Eubalaena glacialis ZMUC-CN2; G, Physeter macrocephalus SCF Pm.141204; H, Hydrodamalis gigas UZMH 710; I, Dugong dugon LDUCZ Z33; J, Trichechus manatus NHMUP C-1442.
FIGURE 2. Profile skeletals of extinct and extant large to gigantic marine mammals, prepared at the same scale and in well-nourished condition, most including chest cross-sections; scale bar equals 4 m. A, Basilosaurus cetoides USNM 4674/4675/12261, 18.35 m, ~15 t; B, Perucetus colossus MUSM 3248 15.7 m, 36.7-40.5 t (sirenian like-type in grey profile); C, Cynthiacetus peruvianus MNHN.F.PRU10, 8.95 m, 4 t; D, Balaenoptera musculus LML GOGA 1982, 27 m, 150 t; E, Balaenoptera physalus MSC Bp.140400, 20 m, 53 t; F, Eubalaena glacialis ZMVC CN2, 14.3 m, 60 t; G, Physter macrocephalus SCF Pm.141204, 16.5 m, 59 t; H, Hydrodamalis gigas UZMH 710, 5.5 m, 3.2 t; scaled up to 8 m fully grown individual in grey, 10 t; I, Dugong dugon LDUCZ Z33 I, 2.7 m, 0.4 t; J, Trichechus manatus NHMUP C-1442, 3.1 m, 0.7 t.
FIGURE 3. Profile-skeletal restorations of Perucetus colossus MUSM 3248 based on minimum (A; 15 m) and maximum (B; 16.4 m) estimated lengths calculated in Appendix 2. Both models restored with cetacean-like (black profile) and sirenian-like tissues (grey profile). Scale bar equals 4 m.
FIGURE 4. Profile-skeletal of Perucetus colossus with sirenian-like soft tissue against the required volumes in the form of cylinders with the same length (in light blue) to match the body mass estimates in Bianucci et al. (2023) and their mass equivalent in numbers to the same length sperm whales (Physeter macrocephalus). A, maximal estimate of 340 tonnes; B, median estimate of 180 tonnes; C, minimum estimate of 85 tonnes.
FIGURE 5. Same scale profile-skeletals, bar equals 4 m, comparing: A, blue whale (includes profile of world record breakers ~190-200 tonne females), in well- nourished condition and rigorously prepared; B, Perucetus colossus holotype (for further details see Figure 1 and Figure 2) to Bianucci et al. (2023) versions (C and D) of differing masses of P. colossus; solid profiles of latter are ~60 t assuming subcircular body cross sections, profile lines are approximations of Bianucci et al.’s median estimate/equivalent (in grey) of large blue whale and maximal estimates (in light grey) either scaled up isometrically (C), or assuming a constant body length (D).
