Koskinonodon formerly known as Buettneria
Mounted specimen on display at the American Museum of Natural History
Reconstruction by Matt Celeskey
When: Triassic (~228 - 216 million years ago)
Where: North America
What: Koskinonodonis one of the later surviving of the giant amphibians. This beast could read up to 10 feet (~ 3 meters) long and was very common in the ancient American southwest. Koskinonodon was known by the name Buettneria for over 80 years, until a long standing nomenclature problem was resovled. See, the name Buettneria was applied to this animal in honor of W. H. Buettner, a fossil collector in the first part of the 20th century. This was in 1922, however, a living species of katydid was given the genus name of Buettneria decades earlier in 1889. Thus the name was not actually availble to be used for this giant amphibian. The name Koskinonodon was applied in 2007. This name was used because a specimen that was named Koskinonodon in 1929 was later determined to belong to the same genus as the previously known specimens that were then called Buettneria. When a genus is renamed this is typically how it is done, you comb though the past literature and use the oldest available name that has ever been used for any species (or specimens!) now housed in that genus. Sadly sometimes you end up using names that are just not as cool as the original. Sorry W. H. Buettner. At least your namesake fossil lives on in outdated museum exhibits. ;)
Koskinonodon is closely related to another large amphibian I have posted, Metoposaurus. It is likely that these two animals occupied the same habitates in life. What differentiates them? At just the general morphology level Koskinonodon has a much longer skull, a longer tail, and less robust limbs. It is common that when a paleo environment is reconstructed just one example of each ‘type’ of animal is used, but this is not really realistic. Think about the average North American forest today. Multiple species of all sorts of ‘types’ of animals are found there, multiple squirrels, deers, and birds that resemble each other very closely but are distinct species. This is how it was in the Mesozoic world as well!
Indricotherium - The largest terrestrial mammal
Skull on display at the American Museum of History of Natural History, New York City
Reconstruction was part of the traveling Extreme Mammals exhibit, photo from when it was at the AMNH.
When: Eocene and Oligocene (~ 34 to 23 million years ago)
Where: Asia and Eastern Europe
What: Indricotherium is the largest terrestrial mammal known. It is a member of the rhinoceros family. Some material was found earlier in the 20th century, but the first fairly complete skull and skeletal elements were found by Roy Chapman Andrews in 1922 while on an expedition for the American Museum of Natural History in Mongolia. Indricotherium would have stood about 16.5 feet (~5 meters) tall at the shoulder and is estimated to have weighed in excess of 20 tons. There were sauropod dinosaurs that were smaller than Indricotherium! This giant was a herbivore and filled a simular niche to the sauropods and modern giraffes, so much so that it is sometimes referred to as the ‘giraffe rhinoceros’. It stripped tall trees bare of leaves using its large front teeth and mobile lips.
In the family tree of mammals Indricotherium is in the order Perrisodactyla (horses, rhinos, and tapirs). Within this group it in the rhinoceros clade. While rhinos today all look pretty much the same their fossil record shows this group used to be extremely diverse, with two completely extinct major sub groupings. Indricotherium is in the group Hyracodontidae (the running rhinos). This lineage divered from that leading to modern rhinos over 55 million years ago. Not all rhinos in this group were giant sized, the very first ones were no larger than wolves! All members of this group lacked horns like Indricotherium.
There is a bit of controversy and confusion surrounding the topic of what genus name to apply to this animal. Indricotherium has been proposed by some workers to be synonymous with Paraceratherium and Baluchitherium, but this is not universally accepted. I have used the name Indricotherium for this entry as both examples shown above are based upon material that has held the name Indricotherium.
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
Nuralagus rex - The Minorcan Giant Lagomorph
When: Pliocene (~3-5 Million years ago)
Where: Minorca, a small island in the Mediterranean
What: Nuralagus is a giant rabbit. It lived on the island of Minorca and is estimated to have weighed 25 lbs (~11kg) on average, though the largest bones found could be from an animal twice this weight! Nuralagus is an excellent example of the ‘island effect’. This is where species on an island are dramatically increased (or reduced) in size compared to their mainland close relatives. Nuralagus is six times the size of the living common rabbit, but was ten times the size of its contemporary mainland bunny brother.
Nuralagus is not just a common rabbit scaled up greatly, along with this increase in size came many other morphological transformations. It was not much of a hopper, the characteristic anatomy of the spine which makes rabbits ‘springy’ was lost. It also did not have the relatively large eyes and ears that we associate with most rabbits. These features may seem very far removed from one another, but the loss of both large ears and hopping is related to the lack of predators on the island. Nuralagus didn’t need to be constantly observant and able to leap away quickly upon sight of a predator, as there was nothing on the island able to take down a grown individual.
Meganeura - The Giant Dragonfly
When: Carboniferous (~305-299 million years ago)
What: Meganeura is the largest dragonfly, with a wingspan of 2.5 feet (~75 cm) in some specimens. The largest living dragonfly is a comparatively weensy 7.5 inches (~19 cm) across at the wings. A scientific debate had centred upon why Meganeura was able to become so large. It has been suggested that it was only able to reach such a great size due to the relatively higher levels of oxygen in the Carboniferous air. This is based partly upon the way most modern insects respire, they do not truly breathe, but instead simply diffusion oxygen throughout their small bodies. However, more recent studies show that larger insects do breathe via compression and expansion of their trachea. Additionally insects much larger than those today have been found in later rocks which do not show evidence of elevated oxygen levels. More research needs to be done to determine the impact of oxygen levels upon the maximum size of insects.
Only a few fossils have been found of Meganeura, but despite this, almost every scene ever of a Carboniferous forest has one of these animals perched upon a giant club moss tree. I do not blame them, I could not resist either. Other animals in these dense forests with Meganeura were a gaggle of other gigantic insects and arthropods, a great variety of amphibians, and the first reptiles. This was the start of the true colonization of land by vertebrates; it has also been suggested it was the arrival of these predators which limited the size of insects such as Meganeura in later time periods.
Mounted specimen located at the North American Museum of Ancient Life, Utah, USA.
Reconstruction by Jaime Chirinos.
When: Paleocene and Eocene (56-40 million years ago)
Where: Europe and North America
What: Gastornis is a giant flightless bird, one of many which roamed the forests of the early Cenozoic. Gastornis is named after the discoverer of the first specimen. These fossils were found in France by Gaston Planté, who would later go on to become a noted physicist, inventing the lead-acid battery. Gastornis was a very large bird, growing up to 6.5 (~2 meters) tall, slightly shorter than the living ostrich, but much more massive. This robust nature is most evident in the skull; the beak of Gastornis was immense and powerful. These predatory birds are thought to have hunted early mammals, preying on the small horses of the time is one popular reconstruction. Above it is hunting a leptictid, an extinct stem placental mammal. While we do not have transitional avian fossils leading up to Gastornis and its kin, it is known that the group falls within modern birds. They have no close relationship with living terrestrial flightless birds, instead they are allied with the clade Galloanserae, the fowls.
Quetzalcoatlus - the largest pterosaur
Reconstructions by Mark Witton.
When: Late Cretaceous (68-65 million years ago)
Where: North America
What: Quetzalcoatlus is a gigantic pterosaur. Just how gigantic it was has been the subject of some debate, as no 100% complete specimen has been found. While the first estimates put its wingspan at up to 50 feet (16 meters) this has been reduced to 36 feet (11 meters) in the latest studies. The reason for this disparity is due to allometry - the physical properties of bones require that as an animal gets larger its skeletal structure is not just that of a smaller animal made larger. Thus the wing bones of Quetzalcoatlus were relatively thicker than that of a smaller species, and while this was taken into account in the first estimates, it took a better understanding of pterosaur evolution in general for a refined estimate to be generated.
This large size brings with it another debate: could Quetzalcoatlus fly? The answer is yes, this pterosaur sailed over prehistoric Texas. A big mystery was how Quetzalcoatlus could take off, and recent work by functional morphologists has provided a solution to this puzzle. Pterosaurs differed from all other flying vertebrates in that they retained the majority of the digits on their hand outside of the wing itself; this not only allowed these fingers to be used to manipulate their environment, but was critical for terrestrial locomotion. Quetzalcoatlus was quadrupedal on the ground, like all other pterosaurs, but it had a specially developed system of ligaments and tendons in its wrist joint that allowed it to ‘spring’ up and take flight. This can be seen in this video.
Another, more minor, debate is what did Quetzalcoatlus eat? Most pterosaurs are closely associated with large bodies of water and have a fish based diet - but all Quetzalcoatlus remains have been found hundres of miles from ancient shorelines. This, combined with morphology of the skull, has lead to the conclusion that these giants instead fed on smaller vertebrate that they would capture with their large beaks, such as the baby sauropod not having a good day in one of the reconstructions above.