Scientists have excavated the largest dinosaur steingervingur which would have been the largest terrestrial animal on our reikistjarna.
Hópur vísindamanna frá Suður-Afríka, Bretland og Brasilía undir forystu háskólans í Witwatersrand hafa uppgötvað a steingervingur af nýrri tegund af risaeðla í Suður-Afríku talið vera skyld brontosaurus. Þessi risaeðla snemma úr Jurassic vó risastór 26,000 pund, þ.e. tvöfalt stærri en afrískur fíll, og stendur fjóra metra á mjöðm. Það hefur verið nefnt „Ledumahadi mafube“ sem þýðir „risastór þruma við dögun“ á tungumáli frumbyggja Sesotho á svæðinu þar sem það fannst.
Þróunarfræðileg umskipti
Ledumahadi er náskyld risaeðlunum af sauropod, þar á meðal þekktum tegundum Brontosaurus og Diplodocus. Hann var jurtaæta, hafði þykka útlimi og var ferfætlingur þ.e. hann gekk á öllum fjórum fótum í svipaðri stellingu og fílar í dag. Í samanburði við langa, mjóa súlulaga útlimi sauropods, voru framlimir Ledumahadi krókari, þ.e. hann hafði sveigjanlegri útlimi eins og frumstæðar risaeðlur. Forfeður þeirra gengu aðeins á tveimur fótum og þeir hljóta að hafa aðlagast að ganga á öllum fjórum og þess vegna stækkuðu þeir til að styðja við meltinguna þar sem þeir voru grasbítar.
Researchers compared steingervingur data from dinosaurs, reptiles etc who walked on two or four legs and they measured limb size and thickness. This is how they concluded Ledumahadi’s posture and its way of walking on all four limbs. It is understood that many other dinosaurs must have experimented walking on all four limbs which could optimally balance a bigger body. Based upon these collective observations, researchers say that Ledumahadi was definitely a ‘transitional’ dinosaur, as it had ‘crouched’ yet very thick limbs to support its large body. Their limb bones– both arms and legs – are very robust and similar in shape to giant sauropod dinosaurs but obviously thicker while sauropods had more slender limbs. The evolution of four-legged postures came before their giant bodies. Just sheer size and elephant-like limb posture helped them, example sauropods, to become one of the most dominant dinosaur groups during the Jurassic era. Ledumahadi definitely represents a transitional stage between two major groups of dinosaurs. The group of early dinosaurs were experimenting with various ways of becoming bigger in size during the first tens of millions of years of their evolution. What it means for research is that the evolutionary transition from a small, bipedal creature to a large, quadrupled sauropod is a complex path and this evolution certainly led to survival and achieving dominance.
The discovery published tells us that even more than 200 million years ago, these dinosaurs were the largest vertebrates to be present on the reikistjarna, and this time period was almost 40-50 million years earlier than giant sauropods were first seen. The new dinosaur is closely related to giant dinosaurs who lived in Argentina around that time supporting the idea that all continents that we see today were assembled as Pangea – a supercontinent comprised of world’s land mass during Early Jurassic. And at that time this region of South Africa was not mountainous as we see it today but was flat and semi-arid with shallow streams. Certainly, it was a thriving ecosystem. Like Ledumahadi, many other dinosaurs – both giant and tiny – roamed the place at the time. It is fascinating that South Africa has helped to understand the rise of giant dinosaurs during Jurassic era.
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{Þú getur lesið upprunalegu rannsóknarritgerðina með því að smella á DOI hlekkinn sem gefinn er upp hér að neðan á listanum yfir tilvitnaðar heimildir}
Heimildir)
McPhee BW o.fl. 2018. Risaeðla frá elstu Jurassic í Suður-Afríku og umskipti til ferfætlinga í snemma Sauropodomorphs. Vísindi. 28 (19). https://doi.org/10.1016/j.cub.2018.07.063
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