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Dinosaurs have been the dominant group of animals on Earth for over 150 million years. Lengthy-necked, plant-eating sauropods akin to Brontosaurus, Diplodocus and Brachiosaurus are most likely among the many most well-known dinosaurs, partly due to their big measurement and unusual physique form (consisting of a protracted neck, lengthy tail, spherical physique and columnar limbs). A number of the largest sauropods measured as much as 37 metres lengthy.
However much less well-known is that they descended from a lot smaller, two-legged, omnivorous or plant-eating creatures known as sauropodomorphs. My colleagues and I just lately recognized a brand new dinosaur species that represents the oldest identified evolutionary step between early sauropodomorphs and sauropods, from about 225 million years in the past.
The sauropodomorphs have been among the many first dinosaurs to exist throughout the late Triassic interval, from about 230 million years in the past. Throughout this time, dinosaurs weren’t but the dominant group of animals on Earth and needed to share the world with, amongst others, crocodile-like reptiles known as phytosaurs and mammal-like reptiles, akin to Morganucodon.
In direction of the top of the Triassic and within the earliest Jurassic, environmental adjustments led to the evolution of bigger, extra fast predecessors of sauropods. These dinosaurs have been bigger, had longer necks, ate solely crops and, extra importantly, walked on all fours on account of their measurement. These transitional species embody Pulanesaura from round 190 million years in the past in what’s now South Africa, and Leonerasaurus from an analogous time in what’s now South America.
Our new dinosaur, which we’ve named Schleitheimia, falls into this class. A few of its bones have been first present in Switzerland as early as 1915. Others had been present in Hallau, close to Zurich, within the 1940s, and others from the identical geological layer had been found in Schleitheim, additionally close to Zurich, within the 1950s. However for years, these fossils have been thought to belong to an earlier, sauropodomorph species.
In 1986, palaeontologist Peter Galton recognized this set of fossilised dinosaur stays, saved on the College of Zurich in Switzerland, as belonging to a typical sauropodomorph often known as Plateosaurus. Plateosaurus had fairly a protracted neck, however didn’t stroll on all fours on a regular basis.
Nevertheless, when Munich palaeontologist Oliver Rauhut examined the bones extra just lately, he observed odd options on them, which made it not possible for them to belong to Plateosaurus. So in 2015, he and I visited the Zurich Palaeontological Museum and examined the bones completely. We found a number of sauropod-like diversifications on the dorsal vertebrae (backbones), the femur (leg bone) and the pelvic or hip space.
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All these diversifications recommend the dinosaur was heavier and primarily walked on all fours, so it couldn’t be a Plateosaurus. It needed to be one thing else, and certainly, it turned out to be one thing new.
We ran a phylogenetic evaluation, which compares anatomical traits between completely different animals and calculates what number of evolutionary steps are essential to make them associated to at least one one other. This urged our new dinosaur, Schleitheimia, was really an intermediate sort between sauropodomorphs akin to Plateosaurus and true sauropods akin to Brontosaurus.
Oldest transitional species
This makes Schleitheimia particular in two methods. First, it’s a lot older than the opposite identified transitional varieties of dinosaur between sauropodomorphs and sauropods. And second, it’s the first transitional type identified from Europe.
What’s much more fascinating, is that a number of the Schleitheimia fossils have been present in the identical quarry as an precise Plateosaurus. Which means each the ancestral sauropodomorphs and the transitional types shared the identical habitat for a time. Finally, nonetheless, the true sauropods took over the atmosphere.
Maybe their measurement and longer necks helped them forage for meals, we aren’t certain. However what we do know is that by the early Jurassic interval, round 170 million years in the past, sauropods have been already residing all over the world from China to Argentina. Schleitheimia offers yet one more piece of the puzzle as to what occurred within the sauropods’ very early historical past on Earth.
The subsequent steps right here shall be to have a look at different materials from roughly the identical age from Switzerland. The unique, historic pit the place Schleitheimia was discovered, has been reopened to see whether or not there may be extra materials.
We need to know if there have been extra intermediate sauropodiforms round, akin to Schleitheimia, or simply extra sauropodomorphs? And the way did the early sauropods diversify and unfold out within the early Jurassic? The truth that we will nonetheless discover new dinosaur species, even in historic museum collections, offers us hope of answering these questions.
Femke Holwerda doesn’t work for, seek the advice of, personal shares in or obtain funding from any firm or organisation that might profit from this text, and has disclosed no related affiliations past their educational appointment.