Study sizes up dinosaurs
SCIENTISTS at UCT have discovered why dinosaurs grew to ginormous heights following research which showed a new pattern of growth in the prehistoric animals.
Some of the iconic Mesozoic longnecked dinosaurs (officially known as the derived sauropodomorphs or sauropods) reached about 36m in length and weighed about 63kg-503kg.
How these majestic creatures reached these sizes have perplexed scientists and the public for decades.
Analysis of the micro-structure of fossil bones of these creatures have shown that they attained these massive sizes through constant sustained growth until the attainment of skeletal maturity.
Thereafter, growth marks (like growth rings in a tree) develop in the outer regions of the bone.
The research was led by PhD candidate Emil Krupandan from UCT’s Biological Sciences, under the supervision of Professor Anusuya Chinsamy-Turan and Dr Diego Pol from the Museo Paleontológico Egidio Feruglio in Trelew, Argentina.
Krupandan said: “What we’re seeing in Antetonitrus is that these dinosaurs show a mosaic of rapid bone growth, with erratic placement of growth marks and textural shifts in the organisation of fibro-lamellar bone that are not quite as regular as their ancestors. Essentially, we are seeing an intermediate growth strategy with elements of both basal and derived sauropodomorph growth strategies present in these early sauropods.”
In contrast, the ancestors of these dinosaurs (basal sauropodomorphs), were smaller and more bipedal animals, and they exhibited cycles of fast and slow growth – similar to the way a cake would be interrupted by layers of icing.
Research shows that the bone micro-structure of the 235 millionyear-old basal sauropod dinosaur Antetonitrus ingenipes from South Africa tells a different story.
This work indicates that en route to the attainment of gigantism dinosaurs such as Antetonitrus, that lie in between the smaller basal sauropodomorph dinosaurs and giant sauropods, have a unique pattern of growth that is actually intermediate between that of the ancestors (basal sauropodomorphs) and the descendants (the derived sauropodomorphs).
UCT palaeobiologist Professor Chinsamy-Turan said: “These findings of an intermediate growth strategy for the South African Antitonitrus challenges previous ideas that the growth strategies of the small bipedal ancestral dinosaurs and that of the massive quadrupedal sauropods was dichotomous.”