Earliest embryos ever discovered provide clues

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <table border="0" cellpadding="0" cellspacing="0" width="95%" height="1"> <tr> <center> <td valign="top" width="33%" height="33"> <b> <p class="MsoNormal"><font face="Arial" size="5">Scientists study oldest-ever dinosaur embryos</font></p> <p class="MsoNormal"><font size="2" face="Arial" color="#00FF00">Finding would allow scientists to detail cradle-to-adulthood growth of dinosaur for the first time</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">Posted July 28, 2005<br> Courtesy University of Toronto<br> and World Science staff </font> </p> <p class="MsoNormal"><b><font size="2" face="Arial">Newly studied embryos of a long-necked, plant-eating dinosaur are the earliest ever recorded for any terrestrial vertebrate, or backboned animal, researchers say.</font></b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial">The scientists claim the discovery yields new clues to how primitive dinosaurs evolved into the largest animals ever to walk on earth. </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial">It also provides a rare glimpse into the life of the <i> Massospondylus</i>, an early dinosaur that grew to five metres (more than five yards) and was fairly common in South Africa, they said.</font></b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> The 190 million year-old embryos are from the beginning of the Jurassic Period, the middle of an epoch known as the age of dinosaurs.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> While the delicate bones of most dinosaur embryos were destroyed over time these embryos are represented by well preserved skeletons, the researchers said. One is nicely curled up inside the egg.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> The findings, by scientists from the University of Toronto at Mississauga and colleagues, are published in the July 29 issue of the research journal <i>Science</i>.</font></b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> “The work on the embryo, its identification, and the fact we can see the detailed anatomy of the earliest known dinosaur embryo is extremely exciting,” said the university’s Robert Reisz.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> “Most dinosaur embryos are from the Cretaceous period,” a later era lasting from 146 to 65 millions years ago, he added.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> Reisz said the finding is interesting because it enables scientists to put the embryos into a growth series and work out for the first time how these animals grew from a tiny, 15 centimetre embryo into a five metre adult.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> “This has never been done for a dinosaur. Only <i> Massospondylus</i> is represented by embryos as well as by numerous articulated skeletons of juveniles and adults. The results have major implications for our understanding of how these animals grew and evolved.” <br> <br> The Massospondylus hatchling was born four-legged, with a short tail, horizontally held neck, long forelimbs and huge head, the researchers said.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> As the beast matured, the neck grew faster than the rest of the body but the forelimb and head grew more slowly. The end result was a two-legged animal that looked very different from the four-legged embryo.<br> <br> Reisz said the embryos provide insight into the origins of the later four-legged giant sauropods, a group that includes the passenger-jet sized <i> Seismosaurus</i>.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial">Sauropods, a group of dinosaurs that include the largest land animals of all time, were small-headed, long-necked plant-eaters.   </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> “Because the embryo of <i> Massospondylus</i> looks like a tiny sauropod with massive limbs and a quadrupedal gait, we proposed in our paper that the sauropod’s gait probably evolved through a phenomenon called paedomorphosis, the retention of embryonic and juvenile features in the adult,” he said. <br> <br> Another point of interest is the absence of teeth, Reisz said.  </font> </b> </p> <p class="MsoNormal"> <b> <font size="2" face="Arial"> “These embryos, which were clearly ready to hatch, had overall awkward body proportions and no mechanism for feeding themselves, which suggest they required parental care,” said Reisz. “If this interpretation is correct, we have here the oldest known indication of parental care in the fossil record.” <br> <br> While the embryos were discovered in 1978 in South Africa, researchers only now managed to clear surrounding rock and eggshell from the embryo.<br> <br> Experts in the field hailed the study as a major contribution to paleontology. “This discovery is exciting in providing a major piece of the puzzle of how <i> sauropodomorphs</i> grew and reproduced,” said James Clark of George Washington University in Washington, D.C.</font></b> </p> <p class="MsoNormal"><b><font size="2" face="Arial">In particular it helps to show that this animal was four-legged when it first hatched and then gradually grew to be two-legged, he added. </font> </b> </p> <p class="MsoNormal"><b><font size="2" face="Arial">* * * </font> </p> </b> </center> <p align="left"><b><font face="Arial" size="2" color="#FFFFFF">Send us a <a href="mailto:editor@world-science.net">comment</a> on this story, or <a href="mailto:?Body=http://www.world-science.net/othernews/050728_embryofrm.htm">send it to a friend</a></font></b> </p> <center> <p>  </center> </td> </tr> </table> </body>