On How to Become a Giant on Land and in the Sea: Lessons Learned from Sauropod Dinosaurs, Ichthyosaurs, and Whales
Life will go where it can. Life thus will probe the extremes, and one of those is giant body size. Among animals, truly giant body size (over 20 tonnes body mass) was only reached by the ichthyosaurs of the Triassic, the long-necked sauropod dinosaurs of the Jurassic and Cretaceous, and the whales of today. While the blue whale (mass 200 t, length 30 m) is generally considered to be the largest animal ever, new evidence suggests that Late Triassic ichthyosaurs may have been even larger. As the largest animals on land ever, sauropod dinosaurs “only” reached about 80 tonnes in body mass, but must have exceeded the ocean giants in length due to the sauropod’s extremely long necks and tails. The upper limits of an animal’s size are set by different parameters, including energetics, reproduction, and body design. Fundamental differences exist between terrestrial and marine animals because the latter must cope with gravity. In the ocean, the cost of transport is lower, and no energy is needed for holding up the body, facilitating large body size in the ocean. All giants are bulk feeders, meaning that they subsist on large amounts of small or immobile food such as plankton or plants. At very large body size, active hunting becomes biomechanically impossible because of the decrease of athleticism (relative decrease of muscle strength) with increasing body size. Fast growth is another prerequisite for gigantism because of decreasing survivorship with time. Fast growth, in turn, requires warm-bloodedness. Among the giants, the evolution of gigantism is best understood in sauropod dinosaurs as a unique combination of primitive features such as egg laying and not chewing their food and derived features such as a bird-like lung. The latter two facilitated the iconic long neck, which in turn facilitated the efficient uptake of energy, allowing sauropod gigantism.
Biography of Prof. Dr. Martin Sander
Prof. Dr. P. Martin Sander has held various positions in the Department of Paleontology of the Institute of Geosciences at the University of Bonn since 1990, including more than 10 years as curator of the Goldfoot Museum. Since 2007 he is head of the museum and professor for vertebrate paleontology. Next to this, he is also committed to communicating scientific findings to the public, leading to several media appearances and numerous invited lectures.
Prof. Sander has divided his research interests between more traditional work in paleontology, such as the excavation and study of Triassic marine reptiles around the globe, and a more biological approach in the study of extinct vertebrates. Part of this work has been fundamental studies towards the microstructure of tooth enamel and fossil bones of dinosaurs. One spectacular application was the 2006 publication of evidence that dinosaurs, like the glacial elephants of the Mediterranean islands, were subject to island dwarfing. In 2004, Prof. Sander was able to secure substantial funding from the German Research Foundation (DFG) to study this topic, and for 10 years he led DFG Research Group 533, “Biology of Sauropods: The Evolution of Gigantism.” Following these experiences, Prof. Sander will shed some light towards gigantism and the evolution of the largest animals ever.