MSGID: 1:317/3 63f98ef2   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    How birds got their wings    
    The origin of a structure in bird wings essential to flight has been   
   found in dinosaurs    
      
     Date:   
         February 24, 2023   
     Source:   
         University of Tokyo   
     Summary:   
         Modern birds capable of flight all have a specialized wing structure   
         called the propatagium without which they could not fly. The   
         evolutionary origin of this structure has remained a mystery,   
         but new research suggests it evolved in nonavian dinosaurs. The   
         finding comes from statistical analyses of arm joints preserved   
         in fossils and helps fill some gaps in knowledge about the origin   
         of bird flight.   
      
      
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   FULL STORY   
   ==========================================================================   
   Modern birds capable of flight all have a specialized wing structure   
   called the propatagium without which they could not fly. The evolutionary   
   origin of this structure has remained a mystery, but new research suggests   
   it evolved in nonavian dinosaurs. The finding comes from statistical   
   analyses of arm joints preserved in fossils and helps fill some gaps in   
   knowledge about the origin of bird flight.   
      
      
   ==========================================================================   
   For a long time now, we have known modern birds evolved from certain   
   lineages of dinosaurs that lived millions of years ago. This has led   
   researchers to look to dinosaurs to explain some of the features unique   
   to birds, for example, feathers, bone structure and so on. But there's   
   something special about the wings of birds in particular that piqued   
   the interest of researchers at the University of Tokyo's Department of   
   Earth and Planetary Science.   
      
   "At the leading edge of a bird's wing is a structure called the   
   propatagium, which contains a muscle connecting the shoulder and   
   wrist that helps the wing flapping and makes bird flight possible,"   
   said Associate Professor Tatsuya Hirasawa. "It's not found in other   
   vertebrates, and it's also found to have disappeared or lost its   
   function in flightless birds, one of the reasons we know it's essential   
   for flight. So, in order to understand how flight evolved in birds,   
   we must know how the propatagium evolved. This is what prompted us to   
   explore some distant ancestors of modern birds, theropod dinosaurs."   
   Theropod dinosaurs, such as Tyrannosaurus rex and Velociraptor, had arms   
   not wings. If the scientists could find evidence of an early example of   
   the propatagium in these dinosaurs, it would help explain how the modern   
   avian branch of the tree of life transitioned from arms to wings. However,   
   it's not so simple, as the propatagium is made up of soft tissues which   
   do not fossilize well, if at all, so direct evidence might not be possible   
   to find. Instead, the researchers had to find an indirect way to identify   
   the presence or lack of a propatagium in a specimen.   
      
   "The solution we came up with to assess the presence of a propatagium   
   was to collect data about the angles of joints along the arm, or   
   wing, of a dinosaur or bird," said Yurika Uno, a graduate student   
   at Hirasawa's lab. "In modern birds, the wings cannot fully extend   
   due to the propatagium, constraining the range of angles possible   
   between connecting sections. If we could find a similarly specific set   
   of angles between joints in dinosaur specimens, we can be fairly sure   
   they too possessed a propatagium. And through quantitative analyses of   
   the fossilized postures of birds and nondinosaurs, we found the telltale   
   ranges of joint angles we hoped to."  Based on this clue, the team found   
   that the propatagium likely evolved in a group of dinosaurs known as   
   the maniraptoran theropods, including the famous Velociraptor. This was   
   backed up when the researchers identified the propatagium in preserved   
   soft tissue fossils, including those of the feathered oviraptorosaurian   
   Caudipteryx and winged dromaeosaurian Microraptor. All the specimens   
   they found it in existed prior to the evolution of flight in that lineage.   
      
   This research means it's now known when the propatagium came into being,   
   and it leads researchers on to the next question of how it came to be. Why   
   these particular theropod species needed such a structure to better adapt   
   to their environment might be a harder question to answer. The team has   
   already begun exploring possible connections between the fossil evidence   
   and embryonic development of modern vertebrates to see if that will   
   shed any light on it. The team also thinks some theropods might have   
   evolved the propatagium not because of any pressure to learn to fly,   
   as their forelimbs were made for grasping objects and not for flying.   
      
   "Dinosaurs portrayed in popular media are becoming more and more   
   accurate," said Hirasawa. "At least now we get to see features like   
   feathers, but I hope we can see an even more up-to-date representation   
   soon where theropods have their propatagium too."   
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Birds # Bird_Flu_Research # Zoology #   
                   Evolutionary_Biology   
             o Earth_&_Climate   
                   # Geology # Weather # Earth_Science   
       * RELATED_TERMS   
             o Feathered_dinosaurs o Whooping_Crane o Convergent_evolution   
             o Archaeopteryx o Fossil o Dinosaur o Bioinformatics o Biology   
      
   ==========================================================================   
   Story Source: Materials provided by University_of_Tokyo. Note: Content   
   may be edited for style and length.   
      
      
   ==========================================================================   
   Related Multimedia:   
       * Wing_evolution_in_birds   
   ==========================================================================   
   Journal Reference:   
      1. Yurika Uno, Tatsuya Hirasawa. Origin of the propatagium in non-avian   
         dinosaurs. Zoological Letters, 2023; 9 (1) DOI:   
         10.1186/s40851-023-00204- x   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230224135058.htm   
      
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