The Mysterious 15 Million Year Gap in Our Evolution - Romer’s Gap

the evolution of vertebrate life on our planet contains many incredible and significant events in the history of its development from the time the first backbone creatures made it onto land to the rise and fall of the mighty non-avian dinosaurs and then the numerous mammalian radiations that occurred afterwards in the cenozoic but the limitations of our planet's fossil record means that at some points there are gaps in our understanding of the past millions of years of evolutionary history are missing and we're only able to make educated inferences about what took place in those times and sometimes these gaps occur in frustratingly important places one of these missing pieces of the puzzle is the so-called Romas Gap this stretches from the very end of the devonian period 360 million years ago for 15 million years until about 345 million years ago in the first part of the Carboniferous period annoyingly for those of us interested in the history of vertebrate Evolution our own Evolution this is a key time in life's past Roma's gaps seemingly obscures the transition from the shallow water and swamp tetrapods that were using their limbs to pull themselves along river and Lake beds and maneuver through dense underwater vegetation in the late devonian to the fully land living tetrapods with terrestrial adapted limbs that existed later in the Carboniferous this Gap was first identified by Alfred Roma an American paleontologist who was fascinated by vertebrate Evolution and developed the basis for a modern understanding of the taxonomic relationships of these various backbones groups to one another in his writings about his research into vertebrate's origins in the 1950s he explained how no satisfactory intermediates between the devonian tetrapods and the ones known from later on in the Carboniferous had yet been found a key Gap in our record of vertebrate history that would later come to be named after him by other paleontologists who investigated this problem so why was there a Gap at this point in time well a couple of different ideas were suggested in the past to explain this fascinating mystery the idea that a global decrease in atmospheric oxygen levels towards the end of the devonian caused this Gap was one of these suggestions argued for in a paper published by researchers in 2006. this study explains that by tracking the atmospheric oxygen levels at this time in Earth's past an explanation for the rise disappearance and Resurgence of tetrapods can be obtained the hypothesis goes that high oxygen levels in the mid and late devonian were one of the driving factors in the success of the tetrapods with such a high concentration enabling these animals to breathe the air more easily instead of getting the oxygen from the water as such the tetrapods and also various arthropods were able to start breathing out of the water and could start exploiting the new terrestrial niches available to them but then the argument goes lower levels of atmospheric oxygen at the start of the Carboniferous coincided with Roma's Gap and would have made conditions unfavorable to air-breathing animals resulting in a much lower diversity and abundance of tetrapods during this time then when oxygen levels increased again later on in the Carboniferous The tetrapods Struck back and began filling more terrestrial niches therefore by this argument Roma's Gap is a real phenomenon that represents a bottleneck in the evolution of vertebrate animals and not as the other argument suggests simply the result of poor sampling from this point in time but there are some issues with the oxygen levels idea firstly it turns out that this conflicting evidence with regards to the concentration of oxygen in the atmosphere across Roma's Gap the levels of oxygen were actually not significantly lower during the Gap when compared to particular other times in Earth's history especially in the late devonian when atmospheric oxygen levels were even lower than in the Gap plus there's the fact that Marine Waters would have had lower concentrations of oxygen than the atmosphere so if anything there would have been even more of a reason for organisms such as the tetrapods to exploit terrestrial habitats this means that levels of oxygen in the atmosphere likely does not explain the phenomenon of Roma's Gap and then there's the other even more damning evidence against this argument as it turns out Roma's Gap probably never even existed as I just mentioned the alternative explanation for The Gap was that the missing record is not a true biological signal but instead a result of sampling bias this means that fossils from this point in time simply hadn't been found either because the sedimentary rock record from the environments the tetrapods lived in at that time just wasn't suitable to preserve fossils or or because we hadn't yet looked in the right places well recent discoveries made in the last two decades have completely changed our view of Roma's Gap this missing part of the history of life on Earth is starting to be filled in with all kinds of wonderful new finds showing that tetrapod diversity was not particularly diminished in this time and that really we're just not been looking in the right places the closing of Roma's Gap began with studies such as the 2002 naming and description of the Carboniferous tetrapods pedophies by the hugely influential English paleontologist Jenny clack this was at the time the only fully articulated tetrad skeleton from the first stage of the carnivorous a stage known as the tornation to be described and represented the start of a bridge across the Gap padurepas came from a site in Scotland and was functionally pentodactyl meaning it had five functional digits on each limb as opposed to the tetrapods from the devonian that had more than five functional digits per limb and lived towards the end of the Gap becoming the earliest known tetrapod at a time to show signs of terrestrial Locomotion for a long time only two sites in the world were known to have produced tetrapod remains from the tornation the locality from which padopis was recovered in Scotland and another in Nova Scotia Canada where many isolated Bones from tetrapods living in Roma's Gap had been found but not identified with complete certainty but then in 2012 came the announcement that a whole series of other sites in Scotland had been located and were producing many different tetrapods that lived during the tornation the Gap had been bridged all kinds of diverse tetrapod fauna were recovered from these various sites across Scotland with both terrestrial and Aquatic forms being described and several new tags are identified and then later named in another publication a few years after such a diverse assemblage of these animals from the tornation stage clearly show that Roma's Gap was indeed the result of collection failure and not actually a real event that was the result of oxygen level changes additionally this relatively High diversity of early tetrapods found just after the end of the devonian seems to indicate that these earliest ancestors of ours recovered quite quickly from the end of devonian mass extinctions indeed another study that had looked at patent of diversity at and after the end of the devonian had hypothesized that Roma's Gap may have represented a lull in diversity after the devastation of the extinction events but the filling of the Gap also seems to disprove this explanation then in 2015 more work was done on the site in Nova Scotia a locality known as blue Beach that represents a deposit dating back to the early tornation at the base of Roma's Gap more intensive collecting of the locality was done and then a paper was published that described in much more detail many of the isolated tetrapod bones actually managing to broadly classify them by comparing them to more complete remains of early tetrapods known from elsewhere yet again this more thorough analysis of a locality from within Roma's Gap demonstrated that a diverse assemblage of tetrapods was present here with evidence for both a large and small body taxa the paper explains how this once again proves that when localities from the right time are identified and properly analyzed a rich diversity of tetrapods from The Gap will be shown to have been living at this point meaning the Gap didn't really exist Additionally the blue Beach site also preserves some very interesting evidence that certain tetrapods weren't even particularly severely affected by the end's devonian extinctions some fragmentary bone elements show many morphological similarities with taxa that are otherwise only known from the late devonian suggesting that these animals potentially survive the devastation at the end of the period relatively unaffected more research continues to be done on the blue Beach locality with a very interesting study from May of 2021 that examined the microstructure of the tetrable bones from the site finding that many of these animals were actually still fully aquatic despite the presence of trackways at Blue Beach that appeared to have been made by terrestrial organisms the paper found that a highly diverse formal assemblage of aquatic tetrapods was present here and that the trackway is supposedly made by land-living tetrapods were probably instead the result of these aquatic tetrapods using their limbs to pull themselves along the substrate underwater and then this substrate becoming aerially exposed later on though they do also accept the possibility that actual special vertebrates made them the bones of which haven't been found yet studies such as these continue to help to refine the known records of the time represented by Roma's Gap showing that early on in the tornadian tetrapods seemed to have still been primarily aquatic whilst slightly later on in this stage at times represented by the Scottish localities there was a diverse assemblage of both Aquatic and terrestrial tetrapods then by the next stage of the Carboniferous the tetrapods had truly conquered the land Roma's Gap is a fascinating story of scientific discovery here was a problem a gap in a known fossil record at an integral part in the history of Life hypotheses were formed by what could have caused this missing chunk of evolutionary history and then they were tested when new discoveries from the right sequences of rock were made and one of these hypotheses that it was down to poor sampling was proven to be correct plus it's pretty incredible that we can predict where we'll find such organisms it's once again more proof of evolution that we can say here's when there should be fossils from a certain group of animals but we don't have any so let's start looking in the right places and they then you find them it's a brilliant success story for Research into tetrapod Origins and I have no doubt that future remarkable discoveries from these Scottish and Canadian sites and hopefully more yet to be found site will reveal much more about this time in Earth's history Roma's Gap has at last been explained well I really hope you enjoyed watching this video and learned something new thank you again for all the support you've been showing us recently with our new boner heads project we've already been enjoying making them for you and we've got some great videos planned for you this year including the rest of our South Africa series things have been very busy recently as I'm currently in my final year of University but don't worry there are many more videos coming anyway a huge thank you to our patreon supporters especially our dinosaur tier supporters Amanda for Nordic arcientos Clara Middleton Daniel Ingraham Drew srivastava Gary Arrington giotist Greg Silvernail Corey Peterson loxypoo mendicant Friar Mike Pace monitor man Nicole Bueno Persian Boy Ralph Balzac Robert Thomas and Steve Bradshaw if you would like to find out more about our world its history and the wonderful life that 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Channel: Ben G Thomas

Views: 225,033

Keywords: Biology, Science, Paleontology, Palaeontology, Dinosaurs, Animals, Nature, Wildlife, Ben, Thomas, Prehistory, Anatomy, Fossil, Bones, News, 7Daysofscience, Days, of

Id: AlqGthe0ZSQ

Length: 10min 35sec (635 seconds)

Published: Sun Feb 19 2023