Skip to content

SciTech

Swimming sloths with aquatic adaptations

by JW Dowey 12 Mar 2014
Swimming sloths with aquatic adaptations

This brown throated sloth is not swimming but some of his distant ancestors may have done. This is one of the 4 species of 3-toed sloths remaining, Bradypus variegatus; Brown-throated sloth image; Credit: © Shutterstock

We have always been fascinated with the sloth and its relatives, so a paper investigating the aquatic versions is very welcome. Eli Amson of Sorbonne Universites and her colleagues presents their results in the document - Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru.

All of the marine vertebrates tend to densify their bone in a kind of osteoclerosis that helps adapt to aquatic life. Dugongs do it and even educated cetaceans do it! The result is a ballast-like effect, to counteract the buoyancy of enlarged lungs. The Sirenia and the whales have the most fossil species that clearly adapted in this way at a very early stage in their evolution. Among the data on these animals, the aquatic sloth genus of Thalassocnus has 5 species dating from the Late Miocene to the Late Pliocene.

The sloths' group of xenarthrans include 6 sloths, anteaters and armadillos, but Thalassocnus was unique in specialising in marine vegetation. At 8, 7, 6 and 5 million years old, the oldest species were dated conveniently to test the theory of increasing bone density (measured as an increase in rib compactness) as aquatic life-styles adapted the animals to their niches. It is interesting to compare them to non-aquatic relatives such as the living anteaters and sloths.

Thalassocnus antiquus is confirmed here as a sister group to all the other fossil species that is itself related to the older Hapalops spp.. The increase in bone compactness was proved to go beyond the ribs and include all of the limb bones. The rear limbs had lost the normal bone medullary cavity completely in the last 2 species in the sequence, providing strong evidence of increasing adaptation. The early whales were very similar in their fossil adaptations. But what about living sloths and anteaters?

Several terrestrial sloths have compact bones. This indicates that the aquatic species of sloth may have already had similar bone in an example of "exaption," or being pre-adapted for a special habitat. It's debateable whether the aquatic niches constitute a cause of the bone development or an effect. Whatever happened, the Peruvian coastline in the Neogene Period (20 million years that included the Miocene and the Pliocene) was desertified, leading to a great incentive for species to adapt to marine herbivore niches. Current living sloths are equally well adapted to their apparently wobbly terrestrial situations, hopefully maintained and conserved successfully, unlike one quite recent extinction, several thousand years ago.


Trending Eco-Friendly Clothing

Love My Planet Women's Relaxed Fit Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Love My Planet Women's Relaxed Fit Hoodie
Love My Planet women's eco-friendly relaxed fit hoodieSize Guide Centimeters 8 10 12 14 16 18 Bust 84 88 92 97 103 108 Waist 66 70 75 80 85 91 Hips 91 95 99 104 109 116 Bust: Measure around the fullest part of...
£38.00
£38.00
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Penguins Hate Push-Ups men's eco-friendly pullover HoodieSize Guide Centimeters XS S M L XL XXL Height 171 175 179 183 189 195 Chest 86 93 99 104 116 129 Waist 71 76 81 89 99 112 Chest: Measure all round your chest just below...
£38.00
£38.00
Close
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Earth
Quick Add
Close
Notify me
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Lightning Bolt kids eco-friendly long sleeve t-shirtSize Guide Centimeters 3-4yrs 5-6yrs 7-8yrs 9-10yrs 11-12yrs Height 98 112 125 136 147 Chest 60 66 70 75 84 Chest: Measure all around your chest just below your armpits. Height: Your natural height If you fall between...
£18.00
£18.00
Close
Notify me
Notify me
Notify me
Union Jack Tote Bag
Earth
Quick Add
Close
Notify me
Notify me
Union Jack Tote Bag
Union Jack eco-friendly colour tote bagProduct Specification Organic Cotton Tote Bag. Twill Weave (170gsm). 37 x 42 cm (7cm gusset.) Made in India / Designed on the Isle of Wight. Wash Cool, Hang Dry.
£16.00
£16.00
Close
Notify me
Notify me
Prev Post
Next Post

Eco-Friendly Shop

Women's Clothing

Eco-Friendly Clothing for Women Our online shop offers a wide range of sustainable women’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Men's Clothing

Eco-Friendly Clothing for Men Our online shop offers a wide range of sustainable men’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Kids Clothing

Eco-Friendly Clothes for Kids Our online shop offers a wide range of sustainable kids clothing products, including t-shirts, hoodies and jumpers. Our garments...
Shop Now
Someone recently bought a
[time] ago, from [location]

Thanks for subscribing!

This email has been registered!

Shop the look

Choose Options

Earth Times
Sign up for exclusive updates, new arrivals & insider only discounts

Recently Viewed

Edit Option
Back In Stock Notification
this is just a warning
Login
Shopping Cart
0 items

Before you leave...

Take 20% off your first order

20% off

Enter the code below at checkout to get 20% off your first order

CODESALE20

Continue Shopping