English: Gerhard Heilmann's comparative illustration of the skulls of Aetosaurus (A), Euparkeria (B), Archaeopteryx (C), a pigeon (D), the upper jaw of a juvenile duckling (E), and the sclerotic ring of Thalattosaurus (F).
Date
Source
The Danish book Vor Nuvaerende Viden om Fuglenes Afstamming
The author died in 1946, so this work is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 75 years or fewer.
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|Description = Gerhard Heilmann's comparative illustration of the skulls of ''Aetosaurus'' (A), ''Euparkeria'' (B), ''Archaeopteryx'' (C), a pigeon (D), the upper jaw of a juvenile duckling (E), and the sclerotic ring of ''Thalattosaurus
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