I've been messing with comparative anatomy with an interest in doing some of these sorts of works so that tf artists can have a great reference for analogous body parts between humans and other animals.
The first and last frames I used for this sequential animation came from a copy I have of an old Russian comparative anatomy book from the 60s. The book has a ton of side-by-sides of human and nonhuman animals in identical poses, and I thought, wouldn't this make a great tf animation.
I used Fantamorph with 10 layers of simultaneous animations in order to get it this fluid.
I've also attached a looping version and an alt animation I did of more uneven growth.
---------------------
Source: “Урок 12: Анатомия животных и изображение животных в действии”. In Курсы известных художников. Edited by: Andry Alekseev. Famous Artists Schools, Inc. Westport: Connecticut, 1960. 5. https://studfiles.net/preview/5999459/.