Faded Genes: The 7 Most Primitive Living Mammals

Mammals may be Earth’s most highly evolved animals but not all mammals are all that highly evolved. Some, like the 7 featured below, are downright primitive.


(images via: Jen, Experience Yarra Valley and Stanford Neuroblog)

The Platypus (Ornithorhynchus anatinus) is native to riverine regions of the eastern Australian coastline and near hinterland. These extremely odd-looking creatures belong to the Monotreme order, specifically because they lay eggs instead of giving birth to live offspring. Platypuses (Platypi?) have thick brown fur that is not only waterproof, it can carry a layer of insulating air to keep the creature warm when it is swimming.

(image via: AwesomeNauts)

The platypus is venomous, one of very few mammals to possess this attribute. Delivered via sharp ankle spurs possessed only by males, platypus venom is strong enough to kill small dogs while human victims may experience exceptional pain that can last for days. As the Traveling Wilburys say, Handle With Care! Click here to view the awesome infographic poster above in a much larger, more readable size.

Mountain Beaver

(images via: OregonLive.com and USDA Forest Service)

The Mountain Beaver (Aplodontia rufa) isn’t a true beaver at all, though both are members of the Rodent family. Mountain Beavers are the world’s most primitive rodents and have changed little over the past 25 million years, although their once wide range has shrunk to forested areas of the Pacific Northwest and northeastern California.

(image via: ECO-USA.net)

Mountain Beavers are often found in the lower reaches of mountainous areas but as they don’t manage to conserve their body heat as well as other mammals, they tend to avoid regions that may experience extreme temperature swings. Besides being the world’s most primitive rodents, Mountain Beavers are parasitized by the world’s largest fleas.


(images via: Andrew Kantor and Wikipedia/Johnruble)

Opossums (fam. Didelphidae) may be primitive but there’s no denying they’re successful: with at least 103 species in 19 different genera, opossums are by far the most common marsupials in the Western Hemisphere. The opossum most familiar to Americans is the Virginia Opossum, the only such creature found north of the Mexican border.

(image via: foreversouls)

Opossums are perhaps best known for their ability to feign death – “playing possum” (see image above). Zoologists believe the behavior is not voluntary but a spontaneous response to extreme fear. If appearing to be lifeless isn’t enough to convince predators they’re not threatening, opossums in such a state excrete a foul-smelling green liquid that repels most other creatures… even skunks. Full credit to Flickr user foreversouls for the above outstanding image of a playful (and fearful) young opossum.


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