アメリカ自然史博物館のインスタグラム(amnh) - 8月27日 01時10分

Today is #NationalDogDay!
The great diversity of sizes and shapes of domestic dog breeds is paralleled, if not surpassed, by what we see in the fossil record of dogs. Unfortunately for us, both the largest and smallest dog species known to science are extinct.
This is a photo of one of the earliest and smallest dogs, Archaeocyon pavidus, next to the largest and one of the most specialized canids, Epicyon haydeni. Archaeocyon, in the foreground, lived 30-million-years ago, and was a Chihuahua-sized dog that sits near the base of the family tree branch that gave rise to all living dog species. In the background is the skull of Epicyon, a huge, bear-sized dog that has evolutionarily modified their skulls and teeth to adapt to a bone-crushing diet. At more than twice the body mass of living spotted hyenas (the best known bone-crusher and dog-like cat-relative), Epicyon could have crushed and eaten anything in its path during its reign as one of North America’s largest predators during the Age of Mammals.
For more fossil dogs, click: #TsengTakeover

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