MSGID: 1:317/3 643f6e67   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Swimming secrets of prehistoric reptiles unlocked by new study    
      
     Date:   
         April 18, 2023   
     Source:   
         University of Bristol   
     Summary:   
         The diverse swimming techniques of the ancient reptiles that ruled   
         the Mesozoic seas have been revealed.   
      
      
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   FULL STORY   
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   Some of the most extraordinary body transformations in evolution have   
   occurred in animals that adapted to life in water from land-living   
   ancestors, such as modern whales, turtles and seals. During the Mesozoic,   
   from 252 to 66 million years ago, while the dinosaurs stomped about   
   on land, many groups of reptiles took to the seas, such as the iconic   
   ichthyosaurs, plesiosaurs, crocodiles and mosasaurs.   
      
      
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   In a new paper, published in the journal Palaeontology, a Bristol team of   
   palaeobiologists used state-of-the-art statistical methods to perform a   
   large- scale quantitative study, the first of its kind, on the locomotion   
   of Mesozoic marine reptiles.   
      
   The researchers collected measurements from 125 fossilised skeletons,   
   and used these to explore changes in swimming styles within lineages and   
   through time, discovering that there was no explosive radiation at the   
   beginning of the Mesozoic, but a gradual diversification of locomotory   
   modes, which peaked in the Cretaceous period.   
      
   Lead author Dr Susana Gutarra of Bristol's School of Earth Sciences   
   said: "Changes in anatomy in land-to-sea transitions are intimately   
   linked to the evolution of swimming. For example, sea lions' flippers   
   have relatively short forearm and large hands, very different from the   
   walking legs of their ancestors. The rich fossil record of Mesozoic   
   marine reptiles provided great opportunity to study these transitions   
   at a large scale."  Co-author Beatrice Heighton, said: "We included   
   measurements from living aquatic animals, such as otters, seals and   
   turtles, of which we know their swimming behaviour. This is very important   
   to provide a functional reference for the ancient species, with unknown   
   swimming modes."  In the aftermath of the end-Permian extinction, about   
   250 million years ago, various groups of reptiles became aquatic hunters,   
   populating the early Mesozoic seas.   
      
   Co-author Dr Tom Stubbs said: "After this devastating event, there was   
   a gradual diversification of locomotory modes, which contrasts with the   
   rapid radiation described previously for feeding strategies. This is   
   fascinating because it suggests a 'head-first' pattern of evolution in   
   certain lineages."  This paper sheds light into the swimming of specific   
   groups. Dr Ben Moon explained: "Ichthyosaurs were highly specialised   
   for aquatic locomotion from very early in their evolution. This includes   
   their close relatives, the hupehsuchians, which had a morphology unlike   
   any other known aquatic tetrapod.   
      
   Further, we see overlap between mosasaurs and ichthyosaurs, which is   
   indicative that mosasaurs evolved a swimming mode by oscillating flukes,   
   different from the eel-like body undulation suggested in the past.   
      
   "In contrast, we don't find evidence of convergence between   
   ichthyosaurs and metriorhynchids (the highly aquatic crocodyliform   
   thalattosuchians). This group retained quite primitive-looking hindlimbs,   
   which seems incompatible with swimming by fluke oscillation."  This study   
   also delves into the evolution of size, a feature related to locomotion,   
   animal physiology and ocean productivity. Professor Mike Benton said:   
   "We know that transition to life in water is usually accompanied by an   
   increase in body mass, as seen in cetaceans, and one of our previous   
   studies shows that large sizes benefit aquatic animals in reducing the   
   mass-specific costs of drag. Thus, it was essential to explore this   
   trait in the wider ensemble of Mesozoic marine reptiles."  Dr Gutarra   
   added: "Body size follows a similar trend to the diversification of   
   locomotory modes, and the widest spread of body size also occurred in the   
   Cretaceous, confirming a strong connection between the two. The rate of   
   increase and the maximum limits to body size seems to vary a lot between   
   groups. This is a fascinating observation. We need to explore further what   
   factors influence and limit the increase in body mass in each group."   
   This research was funded by the Natural Environment Research Council   
   (NERC) and the European Research Council (ERC).   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Marine_Biology # Sea_Life # Evolutionary_Biology   
             o Earth_&_Climate   
                   # Ecology # Biodiversity # Water   
             o Fossils_&_Ruins   
                   # Origin_of_Life # Evolution # Early_Mammals   
       * RELATED_TERMS   
             o Ichthyosaur o Mesozoic o Reptile o Turtle o   
             Geology_of_the_Capitol_Reef_area o Egg_(biology) o Pangaea   
             o Mesopotamia   
      
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   Story Source: Materials provided by University_of_Bristol. Note: Content   
   may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Susana Gutarra, Thomas L. Stubbs, Benjamin C. Moon, Beatrice   
      H. Heighton,   
         Michael J. Benton. The locomotor ecomorphology of Mesozoic marine   
         reptiles. Palaeontology, 2023; 66 (2) DOI: 10.1111/pala.12645   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230418101425.htm   
      
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