Mounted specimen on display at the Harvard Museum of Natural History
Reconstruction by Roman Uchytel
When: Miocene and Pliocene (~17.5 - 4.5 million years ago, and maybe a couple million years more!)
Where: North America
What: Teleoceras was an aquatic rhinoceros. It was a very common beast in the North American Miocene. Yes, rhinos in North America! I have been eager to share with you all the amazing diversity of North American rhinos. The discovery of a tremendous amount of rhinos, not just in terms of numbers of species but their diversity, is one of the great surprises of North American paleontological expeditions in the 19th and early 20th centuries. This continent was home to rhinos the size of modern pigs, rhinos that could run quickly, and even aquatic rhinos! Teleoceras is one of these aquatic rhinos.
Teleoceras had very short legs for a rhino and a nubby horn. This horn is actually pretty large in the scheme of things. As much as the modern rhinos are famous for their horns the vast majority of fossil rhinos show no evidence of having a horn. We can tell this via the presence or lack of a rough surface on the nasal bones. In life Teleoceras would have probably occupied a niche very simular to the modern hippopotamus.
Skull on display at the American Museum of Natural History, NYC
Reconstruction by Anne Musser
When: Late Oligocene to Miocene (~25 to 12 Million years ago)
What: Obdurodon is a fossil platypus, as is fairly obvious from a look at its skull. Though upon closer inspection there are some very important differences; Obdurodon had a larger bill than the living platypus and retained teeth as an adult. Modern adult platypus are toothless, shedding all their teeth as juveniles. These teeth are important as they help us place monotremes (platypus and the echidna are the modern representatives) into the mammal family tree. It is now the consensus that marsupials and placentals are more closely related to one another than either is to the monotremes, but there are a great deal of extinct groups of mammals that may fall between therians and the monotremes - such as the multituberculates. Fossils such as Obdurodon which are most assuredly related to modern monotremes, but preserve more primitive features, are critically important for this phylogenetic issue. So then why is it still an issue? All we have of Obdurodon is a skull, despite the full body reconstruction above, and while there are fossils of even older monotremes they are even more scrappy - just isolated teeth or jaw fragments (that still enjoy full body reconstructions…).
How did Obdurodon live compared to the modern platypus? Well, the living form uses its bill in the water to help it sense prey, and as Obdurodon had an even larger bill, it seem likely it also was aquatic, though without a postcranial skeleton it is unknown if it had the same swimming and digging adaptions seen in its extant relatives.
Mounted specimen from the National Museum of Natural History in Leiden, the Netherlands.
Reconstruction by Mauricio Anton with a common hedgehog for scale.
When: Miocene (~11 - 5 million years ago)
Where: One island that now is part of Italy
What:Deinogalerix is a comparatively giant relative of the hedgehog. It lived on what is now the Gargano peninsula in Italy, but during the Miocene this region was a separate island. Much of Italy during this time period was a series of isolate islands, owing to the higher water level. Deinogalerix was about five times the size of a common hedgehog, more the size of a small fox. However, with a skull about 1/3rd the total length of its whole body, it was proportioned very differently. An eight inch (~20 cm) skull on a 24 inch (~60cm) body isn’t too out of proportion for many of the Lipotyphla (the order that includes hedgehogs, shrews, moles, and solenodons), and it appears Deinogalerix saw no reason to shrink down its head just because of its growth spurt. I have called this animal a hedgehog, and it is in that grouping, but it did not look much at all like the little spiny animal shown above. Within the hedgehog family, its closet relatives are not true hedgehogs, but rather the gymnures or ‘moon-rats’. These animals have not developed spines as protection and are covered with a coat of long course hairs.
Mounted specimen on display at the America Museum of Natural History, NYC
Reconstruction by Charles Knight.
When: Miocene to Pliocene (~12 - 3.5 million years ago)
Where: North America, Europe, Asia, and Africa
What: Gomphotherium is a four tusked extinct proboscidean. Unlike modern elephants which only have enlarged upper incisors as their tusks, Gomphotherium and its kin had enlarged upper and lower incisors. Neither set of tusks grew as large as living elephants, but the lower jaw was heavily modified and elongated to support the lower tusks. If you look at the photograph of the mounted specimen above, you can see that the actual bone of the mandible extends to almost the tip of the upper tusk. Based on the structure of the skull of Gomphotheriumit is thought the animal had a trunk, though again not one as log as the living species of elephants. Gomphotheriumis on the small side compared to the mammoth and mastodon in the photo with it, and also is a bit smaller than the living african elephant, but about the same size as the asian elephant - standing about 10 ft (3.2 meters) tall at the shoulder. These fourtuskers were proportioned very differently from the asian elephant, however. Their legs were much shorter in proportion to their body. The genus Gomphotheriumoriginated in North America, but spread throughout most of the world before going extinct in the Pliocene.
Gomphotheriumin the group Gomphotheriidae (shocking I know). Gomphotheres ranged almost world-wide for over ten million years, and it is possible the last one died less than 10,000 years ago. I say only possible as relationships of gomphotheres, and really proboscideans as a whole, are really not well understood. Gomphotheriidae may be a paraphyletic series of taxa (not a ‘real’ group), with some taxa more closely related to the living species than others. Basically if you are interested in paleontology the study of proboscideans is an area that desperately needs more people in it. You also get to look at other cool extinct forms like Deinotherium!
When: Late Miocene (~ 11 - 6 Million years ago)
What: Shansitherium is a fossil relative of the giraffe. Giraffes are a commonly used example of an easy to see evolutionary transformation, the neck getting longer and longer, and here is some of the evidence used to show that hypothesis. Shansitherium lived in the late Miocene of China, and falls closer to the giraffe line than any other extant clade of artiodactyls. It possesses horns like that of the modern giraffe and okapi, which probably would have been covered with skin in life (these are called ossicones), but over all looks much more like a moose than a giraffe.
Today the Giraffidaehas only two living species, the giraffe (duh) and the okapi, and is only found in sub saharan-Africa. In the Miocene however this group was far more diverse, with Shansitherium just one example of the over a dozen species that roamed all over not just Africa, but Asia and Europe as well. The late Miocene was a time of cooling and drying climates in much of the world, and this is probably what lead to the reduction of species in this clade.
Reconstruction by Willem van der Merwe.
Skeleton on display at the American Musuem of Natural History, NYC.
Reconstruction is part of the traveling exhibit Extreme Mammals which started at the American Museum of Natural History.
When: Late Miocene to Late Pleistocene (7 million to 20,000 years ago)
Where: South America
What: Macrauchenia is a hoofed mammal from South America. This animal has been known to science for a very long time. The first fossils were found by none other than Charles Darwin when he was traveling on the Beagle. He gathered up the fossilized vertebra and limb bones and brought them back to England, where they were studied by Richard Owen, who coined the name Macrauchenia (meaning ‘long neck’), and supposed the whole animal would have resembled a llama. Later fossil finds, including several almost complete specimens, confirmed that Macrauchenia did somewhat resemble a llama, with its slender legs and long neck. However, it was very diffent in some critcal areas, such as having 3 hoofed toes per foot and a mobile trunk. How do we know this animal had a trunk from just the bones? In living mammals with long trunks (such as the elephant and the tapir) the skull is transformed for the musculature that allows such a structure to move, and the skull of Macrauchenia has many features which closely match that of these modern trunked species.
So with this long llama-like neck and the tapir-like trunk, how does Macrauchenia fit into the mammal family tree? That is a subject of much debate, but it is certain that it is not especially closely related to either artiodactyls (llamas) or perissodactyls (tapirs). Macrauchenia is in the order Litopterna, a group of mammals which is only found in South America. Litopterna is assuredly an order of placental mammals, but its exact placement relative to the other major clades is uncertain at this time. It has been suggested they, and other South American ungulate groups, may fall somewhere close to Afrotheria.
South America was isolated from all others for millions of years, in ‘splendid isolation’, during which time the mammals upon it radiated to fill all available niches, and this resulted in dozens of cases of convergent or parallel evolution. There are ungulate fossil froms known from South America that closely resemble not only llamas but also horses, rabbits, and even elephants! Carnivorous forms got in on the act too, such as Thylacosmilus, which looked very simular to the Saber-toothed ‘tigers’ of North America. Many South American natives went extinct during the great faunal interchange, but Macrauchenia survived until the end of the last glacial period. There is hope that one day we might recover some ancient DNA of this animal, which would be very helpful in determining where it falls in the great family tree of placental mammals.
Mounted specimen on display at the American Museum of Natural History, NYC. I could find no reconstruction I liked so have a picture of Barnum Brown next to the specimen for scale.
When: Miocene and Pliocene ( ~11 to 3 million years ago)
Where: India, Pakistan, and Indonesia
What: Colossochelys is a very large land turtle. It mostly roamed in what is now India, but fossils have been found in Pakistan and parts of Indonesia as well. It reached almost 9 feet (~3 meters) long with an estimated weight of about 1 ton. For comparasen the living Galapagos tortoise is about 6 feet (~2 meters) long, and weighs 880 lb (~400kg). Colossochelys is the largest land turtle ever known, but larger turtles swam though the prehistoric seas, such as Archelon. It is thought that this extinct turtle lived much the same way as giant turtles today do, eating plants and drawing into its shell for protection from predators. They vanish from the fossil record at the dawning of the modern Ice House climate, about 2-3 or so million years ago.
This giant turtle has been known by other names in the scientific literature, and some museum displays have not been updated. So do not get confused! It has been labeled both Geochelone atlas and Testudo atlas in the past. Why the change? Turtle systematics have been in a state of confusion for a while, and both of these genera were found to be massively polyphyletic. This means that they were essentially random groupings of taxa that did not share a close relationship to one another to the exclusion of all other turtles. Colossochelys altas is not at risk for a name change again (due to this reason at least!) as it is the only member of this genus.
Also man, isn’t that just the happiest looking fossil you have ever seen?
When: Miocene (~12 - 13 million years ago)
What: Livyatan is a gigantic toothed whale. It is fairly closely related to the living sperm whale, and is thought to have been about the same size, at 45 feet (~14 meters) long. This is an estimate as the whole body was not found, but its head was fairly well preserved, and its skull alone is 10 feet (~3 meters long) Unlike the modern sperm whales, it had a full set of teeth in both its upper and lower jaws, and its lower jaw was not reduced compared to its skull. Inside these giant jaws were giant teeth, the largest of which are 1.2 feet (~36 cm) long. What did they eat with these massive jaws and gigantic teeth? Well, living sperm whales eat very large prey, such as giant squids and megamouth sharks with their comparatively small jaws and teeth. It has been suggested that Livyatan was feeding upon other whales at the time! Such as the reconstruction above where a Livyatan dramatically ruins the day of a Cetotherium (an extinct baleen whale).
The name ‘Livyatan melvillei’ is meant to bring to mind Melville and his famous white sperm whale Moby Dick. Originally the name published was Leviathan melvillei, but it had to be changed, as the genus name of Leviathan was already taken! It belongs to a poorly known species of mastodon named by a researcher in the mid 1800s. Thus, the spelling of this giant whale’s name had to be altered, as once a name is applied to something it is there forever! Let this be a lesson to carefully check your species names before you publish them, as there are a few cases of something like this happening. Mostly it seems species of theropod dinosaurs are accidentally given names that have already been applied to beetles. Whoops!
The area of Peru where Livyatan was found is today a harsh desert, but geologists think that during the Miocene this area was an ocean paradise; a warm shallow lagoon. Dozens of marine species have been found in this desert, not only a variety of toothed and baleen whales, but also sharks and pinnipeds.
Reconstruction by C. Letenneur, Muséum National d’Histoire Naturelle, Paris, France
When: Late Miocene (~6 million years ago)
What: Argentavis is the largest flighted bird there ever was. Its wingspan has been estimated at 23 feet (~7 meters), almost double that of the largest flying bird that soars today’s skys, the wandering albatross (Diomedea exulans). All specimens of this avaian have been found in Argentina, hence its name, which means ‘magnificent Argentine bird’. Recent studies looking at the biomechanics of flight in Argentavis have determined that it was a soaring bird, like today’s condors and vultures. It would have easily glided upon the strong thermals above the Argentine pampas, but getting up to those winds was a bit more of a challenge. It was too large to just flap its wings and take off, even when it was standing in a strong headwind. Instead Argentavis would have had to run down a steep hill or jumped from a high perch in order to take to the skies. Once it was up there, however, it is estimated it could have soared for hours, hunting for prey as it rode the late afternoon thermals.
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.