Have a sea-sloth.
South America was an isolated continent for around 85 million years, up until it became connected to North America about 3 million years ago, and an amazing range of unusual species evolved there during that time. There were all sorts of marsupials, anteaters, armadillos, sloths, strange ungulates… and that’s just some of the mammals. Birds were up to crazy stuff too, with things like giant flightless “terror birds” and the largest ever flying bird.
This critter here is Thalassocnus, a giant marine sloth that lived on the coast of Peru between 10 and 2 million years ago. Their fossil remains show evolution towards a more and more aquatic lifestyle, grazing on sea grasses and seaweed in progressively deeper water — and even starting to develop sealion-like limbs in the youngest known species.
I like to believe these guys went extinct because they were lazy and just eventually all drowned. Either that or they were murdered by otters, because otters are evil and were worried the sloths would steal their niche.
Ancient Pygmy Sea Cow Discovered
A McGill University researcher has discovered a near-complete skull of a primitive “dugong” illuminating a virtually unknown period in Madagascar fossil history.
The discovery of a Middle Eocene (48.6-37.2 million years ago) sea cow fossil by McGill University professor Karen Samonds has culminated in the naming of a new species. This primitive “dugong” is among the world’s first fully-aquatic sea cows, having evolved from terrestrial herbivores that began exploiting coastal waters. Within this ancient genus, the newly discovered species is unusual as it is the first species known from the southern hemisphere (its closest relatives are from Egypt and India), and is extremely primitive in its skull morphology and dental adaptations.
The fossil is a pivotal step in understanding Madagascar’s evolutionary history — as it represents the first fossil mammal ever named from the 80-million-year gap in Madagascar’s fossil record.
The research is to be published in the Journal of Vertebrate Paleontology on December 12…
(read more: Science Daily) (McGill University)
One of my favorite fossils. Too cute.
When: Early Cretaceous (~125 million years)
Where: Liaoning, China
What: Mei is a paravian dinosaur. Paraves is the clade comprised of birds and two families of non-avian dinsaurs; Troodontidae and Dromaeosauridae. As Mei is a fairly basal member of the troodontids, it is not very far removed from the common ancestor of all paravians. Its bird-like heritage can be easily seen in this extraordinary articulated fossil shown above. This specimen was found in a sleeping pose, which is very much like the resting posture of many modern birds, with the legs folded underneath the body and the head folded back and resting on the shoulder. It is this pose that gives the taxon its full name: Mei long, which translates to ‘sleeping dragon’. This animal is a sub-adult, determined via the ends of its bones not yet being fused, and would be roughly 21 inches (~53 cm) long, if it was not curled up as it is.
The find of a basal troodontid in this pose gives us far more information than just when the sleeping posture was adapted by this clade. It has been determined that modern birds commonly sleep like this to preserve their body heat, covering up the areas that are most prone to radiating heat. If Mei long and its kin were not ‘warm blooded’ than there would be no benefit to sleeping in this pose. Thus, this provides another compelling bit of evidence that the ‘warm bloodedness’ of modern birds was present in their mesozoic non-avian relatives.
A primitive xenarthran? Sounds pretty redundant to me. Stick with ‘basal’ and you can’t go wrong.
Peltephilus - The Horned Armadillo
Skull located in the Museo Histórico Nacional, Buenos Aires, Argentina.
When:Oligocene to Miocene (~29 to 15 million years ago)
Where: South America
What: Peltephilus is a primitive armadillo. This is the only known armadillo with horns, and one of only two known horned fossorial (digging) mammals. The other is Ceratogaulus, a gopher that lived somewhat contemporaneously in North America. Like Ceratogaulus, the horns of Peltephilus were for defensive purposes, and were not useful in either digging or for battles between individuals. Peltephilus was once proposed to have been a fast running meat eating armadillo, but more recent and in-depth studies have countered these claims and instead demonstrated that this 3 feet (~1 meter) long armadillo was indeed a digging herbivore like most known armadillos.
Peltephilus is the basal most armadillo known. One of its most obvious primitive features is that it has a full compliment of teeth in the front of its mouth that contact one another. All other armadillos have reduced anterior dentition and thus ‘spouts’ at the front of the mouths. These front teeth were the source for the early ideas of carnivory in this species. Even though Peltephilus was primitive in this, and other cranial and skeletal features, it is still highly derived and, well, already armadillo like in many other aspects, most notably its well developed carapace.
Creationists, eat your hearts out.
When: Eocene (all known fossils from a deposit 52.5 million years old)
Where: Wyoming, USA
What: Onychonycteris is the most basal bat currently known. It differs from living bats in having claws on all five fingers, whereas living bats have lost them. This form also has relatively shorter arms and fingers, as well as longer legs and tail than any other bat, fossil or extant. Onychonycteris was an extremely important find, as allowed us to answer a long standing question about bat evolution: Which came first, flight or echolocation? This taxon was capable of flight, and detailed examination of the cranium revealed that it could not echolocate. Thus, bats took to the skies before they developed a system for seeing with their ears.
This amazing fossil is from the Green River fossil lagerstatten in southwestern Wyoming, and is one of two known complete specimens. This example is not the holotype (the specimen which bears the name) as while it looks absolutely gorgeous, the second specimen was arranged on the rock slab in such a way more of the skull could be studied. Additionally, this specimen was actually in the hands of a private collector, and thus not fully available to science. That is until the specimen was mailed, unannounced, to Dr. Nancy Simmons at the American Museum of Natural History, New York. She was working on publishing this taxon at the time, and the private collector had been informed of this, so the family sent the specimen to allow her the best examination possible. That was one awesome package to open, believe me!
Mammal paleontologists do have a thing for teeth. Look at that sexy thang.
A grinding tooth of Mastodon giganteus of Ohio
A pictorial atlas of fossil remains
London :H.G. Bohn,1850.