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The fossil was found mummified in an Oklahoma cave system, and it preserves something paleontologists almost never get to see from this era: not just bones, but also skin, cartilage, and even traces of ancient proteins.<\/p>\n
Together, these tissues reveal the oldest known example of costal respiration in amniotes, the group that includes reptiles, birds, mammals, and their shared ancestors, showing how they breathe.<\/p>\n
Mummified Captorhinus aguti fossil<\/p>\n
Captorhinus aguti came from Richards Spur, a site in Oklahoma famous among paleontologists for its dense record of late Paleozoic land animals<\/a>. The cave system has yielded an unusually diverse snapshot of life from that time.<\/p>\n What made this particular discovery stand out is how the environment preserved the body: conditions such as oxygen-poor mud and hydrocarbons helped keep the tissues from collapsing and rotting away.<\/p>\n So instead of a flattened imprint, researchers found something closer to a natural \u201cmummy\u201d \u2013 a small animal frozen in a lifelike pose, with one arm tucked under its body.<\/p>\n To study it without damaging it, the team used neutron computed tomography (nCT) at a facility in Australia, which let them look through the surrounding rock as if they were performing a medical scan.<\/p>\n Accordion-like skin pattern<\/p>\n When teams began working through the scan data, researchers realized there was far more than bone present.<\/p>\n \u201cI started to see all these structures wrapped around the bones. They were very thin and textured. And, lo and behold, there was a nice wrapping of skin around the torso of this animal,\u201d said Ethan Mooney, who co-led the study while working in Professor Robert R. Reisz\u2019s lab at the University of Toronto<\/a>.<\/p>\n \u201cThe scaly skin has this wonderful accordion-like texture, with these concentric bands covering much of the body from the torso up to the neck.\u201d<\/p>\n That \u201caccordion\u201d pattern is especially interesting because it resembles the flexible, ringed scales seen in modern burrowing reptiles<\/a> like worm lizards. <\/p>\n This kind of body design lets an animal bend and twist without tearing its skin, but the skin wasn\u2019t the main prize.<\/p>\n The researchers examined three Captorhinus aguti specimens, and together they preserved a set of chest structures that are rarely visible in fossils this old.<\/p>\n In one specimen, the team identified a segmented cartilaginous sternum, ribs associated with the sternum, intermediate ribs, and connecting structures that link the rib cage to the shoulder region.<\/p>\n That combination matters because it allows scientists to reconstruct something that\u2019s usually lost to time: how the entire breathing apparatus was assembled in an early amniote<\/a>.<\/p>\n \u201cWe propose that the system found in Captorhinus represents the ancestral condition for the kind of rib-assisted respiration present in living reptiles, birds, and mammals,\u201d Reisz said.<\/p>\n Thus, this little Permian reptile may show the basic layout that was later refined into the breathing mechanics that power everything from a running lizard to a flying bird to a human sprint.<\/p>\n Breathing changed life on land<\/p>\n Before amniotes, the dominant land vertebrates were reptile-like animals that could breathe partly through their skin and used a mouth-and-throat pumping method to move air into their lungs.<\/p>\n That system can work, but it is not well suited for animals that need to be highly active on land.<\/p>\n Costal breathing \u2013 the system in which muscles between the ribs expand and compress the chest cavity \u2013 is more efficient. It can pull in more air, exchange gases more effectively, and support higher activity levels.<\/p>\n \u201cIt was a game changer that allowed these animals to adopt a much more active lifestyle,\u201d Mooney said.<\/p>\n That extra oxygen capacity may help explain a broader historical pattern. Once amniotes \u2013 including early reptile ancestors \u2013 had the tools to live and breathe more powerfully on land, they diversified rapidly and eventually became the dominant land vertebrates<\/a>.<\/p>\n The fossil didn\u2019t just preserve anatomy. Using synchrotron-based infrared spectroscopy, the researchers also detected remnants of original proteins in the fossil\u2019s bone, cartilage, and skin.<\/p>\n \u201cThe protein remnant finding is exceptional, and it dramatically pushes our understanding of what is possible in terms of soft tissue preservation in the fossil record,\u201d Mooney said.<\/p>\n That is a significant finding because Paleozoic fossils are usually far too old to retain anything like original organic molecules.<\/p>\n The study suggests that, under the right conditions, the fossil record may be holding onto biochemical clues from much deeper time than scientists previously assumed.<\/p>\n Lessons from Captorhinus aguti<\/p>\n Captorhinus wasn\u2019t a dinosaur-sized giant or some dramatic \u201cmissing link\u201d skeleton. It was small, common, and probably the kind of animal that once scurried through the undergrowth without much fuss.<\/p>\n But thanks to extraordinary preservation, it is now helping explain something fundamental. It shows how early amniotes turned breathing<\/a> into a powerful engine for life on land \u2013 and how that same basic design still drives the rise and fall of our own ribs every day.<\/p>\n The full study was published in the journal Nature<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Breathing with your ribs feels so normal that it\u2019s easy to forget it\u2019s an invention. The chest expands,…\n","protected":false},"author":2,"featured_media":387534,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[85,46,141],"class_list":{"0":"post-387533","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-il","9":"tag-israel","10":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/387533","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=387533"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/387533\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/387534"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=387533"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=387533"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=387533"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Digital](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/04\/reptile-fossil_Captorhinus-aguti_first-breathing-system_scans_Nature_1s.webp.webp\")
<\/a>Digital recreation of mummified Captorhinus aguti fossil from 289 million years ago showing nCT renderings and skeletal reconstruction in left lateral views. Credit: Nature. Click image to enlarge.Human link to Captorhinus aguti<\/p>\n![\"289-million-year-old](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/04\/reptile-fossil_Captorhinus-aguti_amniote-breathing-system_Michael-DeBraga_1s.webp.webp\")
<\/a>289-million-year-old reptile Captorhinus aguti, first human ancestor to rib breathe, in its death pose in a cave system. Credit: Dr. Michael DeBraga. Click image to enlarge.Ancient proteins still remain<\/p>\n