Figure 4. Comparative analysis in whales.

(A) Forelimb bones of the minke whale Balaenoptera acutorostrata. (B) Comparative anatomy of bony and cartilaginous epiphyses in the distal portion of the forelimbs of various cetacean whales: B1-B2 – early cetaceans; B3-B4 – baleen whales; B5-B10 – toothed whales. (B1) Maiacetus inuus, semi-aquatic from Eocene era (56–33.9 Mya), (B2) Dorudon atrox, fully-aquatic from Eocene era (B3) minke whale Balaenoptera acutorostrata from Miocene era (23–5.3 Mya) (B4) North Atlantic right whale Eubalaena glacialis, (B5) pilot whale Globicephala melas (B6) boto river dolphin Inia geoffrensis, (B7) narwhal Monodon monoceros, (B8) killer whale Orcinus orca, (B9) juvenile and (B10) subadult sperm whale Physeter catodon. (C) Sample image of an adult killer whale Orcinus orca (same species as B8) with X-ray images of the highlighted areas (C1 and C2) from the corresponding image on their left. (D) Sample (left) and X-ray (right) images of an adult beluga whale Delphinapterus leucas. (D1) Micro-CT reconstruction of the highlighted phalange joint. (E) CT image of an adult killer whale Orcinus orca and a virtual sagittal section of the metacarpal II demonstrating the absence of the SOC.

Figure 4—video 1. CT scan of the manus of a killer whale Orcinus orca.

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