Here is the sequential keyframes of the little animation I did.
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.
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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/.