{"id":621667,"date":"2026-09-11T18:22:10","date_gmt":"2026-09-11T18:22:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/ie\/621667\/"},"modified":"2026-09-11T18:22:10","modified_gmt":"2026-09-11T18:22:10","slug":"ichthyosaurs-had-surprisingly-dense-ribs-new-study-finds","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ie\/621667\/","title":{"rendered":"Ichthyosaurs Had Surprisingly Dense Ribs, New Study Finds"},"content":{"rendered":"

Long before whales ruled the oceans, dolphin-shaped marine reptiles called ichthyosaurs patrolled the same waters. New research from the Natural History Museum at the University of Oslo suggests their rib cages may have done a job modern whale ribs don\u2019t: acting as ballast to help them dive. The findings<\/a> appear in the journal PeerJ.<\/p>\n

\"Cryopterygius<\/a><\/p>\n

Cryopterygius kristiansenae, a species of ophthalmosaurid ichthyosaur from the Jurassic of Svalbard. Image credit: Esther van Hulsen.<\/p>\n

\u201cIchthyosaurs were secondarily aquatic reptiles that dominated the world\u2019s oceans through much of the Mesozoic Era, with a fossil record spanning from the Early Triassic (250 million years ago) to their final demise in the early Late Cretaceous (93 million years ago),\u201d said senior author Dr. Lene Liebe Delsett and and colleagues.<\/p>\n

\u201cThey are among the few aquatic amniotes to acquire a fully aquatic lifestyle in the open ocean, matched only by that of modern cetaceans.\u201d<\/p>\n

\u201cIn both groups, the skeleton underwent extreme modifications compared to their land-dwelling ancestors, and consequently, these groups are important for understanding convergent evolution of secondarily aquatic adaptations.\u201d<\/p>\n

\u201cWe investigate physiological data recorded in the microstructure of ribs and gastralia to answer two questions,\u201d they added.<\/p>\n

\u201cFirst, did ichthyosaurs have a high and consistent growth rate?\u201d<\/p>\n

\u201cSecond, as cetaceans are commonly seen as the modern analogues of ichthyosaurs, do their rib microanatomy and histology converge?\u201d<\/p>\n

In their study, the authors examined the internal microstructure of ribs from two ichthyosaur fossils unearthed on the Norwegian archipelago of Svalbard, comparing them to the ribs of two living toothed whales, the beluga and the harbor porpoise.<\/p>\n

These ichthyosaur individuals, belonging to the genera Keilhauia<\/a> and Palvennia<\/a>, lived roughly 150 million years ago during the Late Jurassic period.<\/p>\n

They had body shapes and predatory lifestyles that closely mirror those of today\u2019s dolphins and porpoises, a phenomenon scientists call convergent evolution.<\/p>\n

Despite the outward resemblance, the researchers found a clear difference beneath the surface.<\/p>\n

They determined that the ichthyosaur ribs were considerably denser and more compact than those of the beluga and porpoise, which have a more open, spongy structure inside.<\/p>\n

\u201cIchthyosaur skeletons are in general quite light, but the ribs are not,\u201d said Dr. J\u00f8rgen Kr\u00f8glid, first author of the study.<\/p>\n

\u201cThis was a bit surprising to us. Compact bones are typically found in animals that move slowly, such as manatees,\u201d Dr. Liebe Delsett said.<\/p>\n

The scientists propose that the added weight in the ichthyosaurs\u2019 ribs may have helped counteract the buoyancy created by their air-filled lungs, making it easier for the animals to descend and stay submerged.<\/p>\n

\u201cIchthyosaurs descend from land-living reptiles, and their spine has a sideways movement, like in lizards. Their tail is vertical, like in sharks and fish,\u201d Dr. Kr\u00f8glid said.<\/p>\n

\u201cTherefore, ichthyosaurs need a bit of help to get the right angle when they dive. A little extra weight around the air-filled lungs may not be such a bad idea.\u201d<\/p>\n

\u201cI imagine that the slightly heavier ribs can counteract this buoyancy and help ichthyosaurs initiate their dive. A bit like divers use weight belts. Once they get that downward angle, they can just keep swimming.\u201d<\/p>\n

\u201cIn the big picture, ichthyosaurs and toothed whales are a very good example of convergent evolution, first and foremost when it comes to body shape.\u201d<\/p>\n

\u201cBut when we study microanatomy and cell structure, it\u2019s obvious that there are differences.\u201d<\/p>\n

The authors also looked for signs of the animals\u2019 growth rates and ages by examining bands and lines within the bone tissue itself.<\/p>\n

The ichthyosaur ribs showed alternating layers reflecting periods of faster and slower growth, consistent with earlier evidence that ichthyosaurs grew quickly and may have had an elevated, warm-blooded-like metabolism.<\/p>\n

_____<\/p>\n

J. Kr\u00f8glid et al. 2026. Rib microstructure in thunniform ichthyosaurs and toothed whales. PeerJ 14: e21486; doi: 10.7717\/peerj.21486<\/p>\n","protected":false},"excerpt":{"rendered":"Long before whales ruled the oceans, dolphin-shaped marine reptiles called ichthyosaurs patrolled the same waters. New research from…\n","protected":false},"author":2,"featured_media":621668,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[10554,239178,263961,51439,263962,263963,68944,47194,73844,85,9155,958,48456,61,60,51441,263964,496,298,263965,263966,69376,61539,82,86940,263967,1976],"class_list":["post-621667","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-bone","tag-buoyancy","tag-cetacea","tag-convergent-evolution","tag-cryopterygius","tag-cryopterygius-kristiansenae","tag-density","tag-diving","tag-dolphin","tag-evolution","tag-fossil","tag-growth","tag-ichthyosaur","tag-ie","tag-ireland","tag-jurassic","tag-keilhauia","tag-metabolism","tag-norway","tag-palvennia","tag-porpoise","tag-reptile","tag-ribs","tag-science","tag-svalbard","tag-toothed-whale","tag-whale"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/621667","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=621667"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/621667\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/621668"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=621667"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=621667"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=621667"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}