If you like dinosaurs and ancient reptiles, then this past month has been a real treat with major discoveries from land, sky and sea. On August 13, 2014, the discovery of a rare pterosaur fossil bed in southern Brazil was reported in PLOS One. Two weeks later, Drexel scientists described a fossil of a gargantuan land animal, possibly the largest ever discovered. Even more recently, on September 12, another group reported that the largest carnivorous dinosaur ever, the Spinosaurus, had adaptations that allowed it to swim.
Sky - Pterosaurs
Pterosaurs are an extinct group of flying reptiles which evolved on a separate branch of the reptile family tree from dinosaurs. They evolved over a period of approximately 170 million years, and ultimately became extinct during the Cretaceous period 66 million years ago, around the same time that Tyrannosaurus rex and other large dinosaurs died out. Pterosaurs are thought to be the first, and largest, vertebrates to fly under their own power; they had a wide range in size, from the very small, such as the Nemicolopterus with a 25cm (about 10 inches) wingspan, to the very large, such as the Hatzegopteryx with a 12m (about 39 feet) wingspan (to put that into perspective, that’s a larger wingspan than an F-16 fighter jet, which is around 32 feet!). They flew with their forelimbs, with the wing membrane supported by one digit, which would be the equivalent of our fourth finger.
Pterosaur fossils have been found on nearly every continent, but the fossils are rare, as like bird bones, pterosaur bones were thin and fragile and prone to being scattered or damaged before they could be preserved. The fossil bed found in southern Brazil by Paulo Manzig and colleagues were of a new species of pterosaurs, Caiuajara dobruskiis. These pterosaurs were mid-sized, with estimated wingspans ranging from 0.65-2.35m. This fossil bed is interesting for several reasons. While many pterosaur fossils have been found in northeastern Brazil, this particular fossil bed is the farthest south of any find in the country. Additionally, these fossils were found in a region believed to be around an inland lake in the desert, which is also unusual as pterosaur fossils tend to be found near ancient coastal regions or shallow marine deposits, and fossil records from areas deep inside continents is limited. Furthermore, several pterosaurs were found together, and while it is difficult to determine exactly how many unique individuals there are in this fossil bed, the researchers believe there were at least 47 individuals and possibly hundreds of individuals, ranging in age from juveniles to adults. The close proximity of the fossils suggest that these pterosaurs may have lived in social groups, rather than as solitary creatures.
As an aside, if any readers out there are in New York City before January 4, 2015, I highly recommend visiting the American Museum of Natural History and checking out their pterosaur special exhibit!
Land - Titanosaurs
A team of scientists from Drexel University have reported a new member of the titanosaur family of plant eaters. The Dreadnoughtus schrani, meaning “fears nothing”, was unearthed between 2005-2009 from Argentina, and is “exceptionally complete, with over 70% of the bones, excluding the head, represented.” It is estimated that this particular individual was 26m (85 feet) long, and weighed about 59,300 kg (65 tons); amazingly, based on the bone structure, scientists believe that this individual was still growing, meaning that in its fully matured adult form it would have been even larger! Currently Dreadnoughtus holds the record for largest land animal, breaking the previous record set by Elaltitan, another large titanosaur found in Argentina weighing in at 47 tons (approximately 42,600kg). Today, the largest land animal is the African bush elephant, weighing in at an average of 8,500kg.
Sea - Spinosaurus
Fans of Jurassic Park III might remember the fight scene between Tyrannosaurus rex and Spinosaurus; the two massive carnivores circle and charge at each other, until finally the Spinosaurus gained the upper hand and snapped Tyrannosaurus’s neck, killing it instantly. Indeed, Spinosaurus was an enormous dinosaur, likely measuring in at over 15m (49 feet) long and weighing up to 20,000kg, making it possibly the largest carnivore ever; in comparison, Tyrannosaurus measured around 13m (43 feet) and weighed in around 7,000kg. Fossils of Spinosaurus aegytiacus were first found in Egypt in 1912, but were destroyed during the bombings of World War II. This most recent find is the most complete skeleton of Spinosaurus aegytiacus. Analysis of the size and bone density of the limbs suggested that Spinosaurus was better suited paddling and submersion in water, rather than running on land. Additionally the structure of the snout shows similarities to the pressure sensors in the snouts of modern-day crocodiles, with the teeth being suited for snagging fish. This makes Spinosaurus the first dinosaur known to swim. While a battle between Spinosaurus and Tyrannosaurus makes for good movie scenes, the reality is that Spinosaurus likely hunted for aquatic prey (additionally evidence suggests that Spinosaurus and Tyrannosaurus lived in different time periods and on different continents!)
I find it both amazing and somewhat terrifying that these giants once roamed the earth. Also, it is fascinating how much palaeontologists can deduce by studying rocks and fossils. While a part of me thinks it would be really cool to travel back in time and observe these creatures, another part of me worries about being crushed or eaten, given how miniscule we are in comparison. For now I’ll stick with documentaries and natural history museums.