{"id":77653,"date":"2026-08-20T21:37:48","date_gmt":"2026-08-20T21:37:48","guid":{"rendered":"https:\/\/www.europesays.com\/japan\/77653\/"},"modified":"2026-08-20T21:37:48","modified_gmt":"2026-08-20T21:37:48","slug":"fossil-of-small-duck-billed-dinosaur-relative-found-in-japan","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/japan\/77653\/","title":{"rendered":"Fossil of Small Duck-Billed Dinosaur Relative Found in Japan"},"content":{"rendered":"

A fossilized bone unearthed two decades ago in northeastern Japan belongs to one of the smallest iguanodontian dinosaurs ever found in the country\u2019s Cretaceous marine rocks, according to new research led by the University of Tsukuba<\/a>.<\/p>\n

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

Reconstruction of the iguanodontian dinosaur from the Ashizawa Formation in Japan; the red bone is the right sternal. Image credit: Masato Hattori.<\/p>\n

\u201cIguanodontia<\/a> is a major group of small- to large-bodied ornithopod dinosaurs \u2014 approximately 2 m (6.6 feet) to greater than 10 m (33 feet) in length \u2014 that existed from the Late Jurassic through the latest Cretaceous,\u201d said University of Tsukuba paleontologist Masami Kondo and colleagues from Japan and Canada.<\/p>\n

\u201cIguanodontians attained a worldwide distribution during this time, and their fossils are known from every continent.\u201d<\/p>\n

\u201cAsia was an important region for their diversification across Laurasia, as dispersals occurred both between Asia and North America and between Asia and Europe.\u201d<\/p>\n

\u201cA high diversity of iguanodontian species has been recovered from the Cretaceous of eastern and central Asia.\u201d<\/p>\n

\u201cThe increased number of reports of iguanodontian fossils from Japan over the past two decades is significant, as this region represents an easternmost margin of Cretaceous Laurasia.\u201d<\/p>\n

In the study, Dr. Kondo and co-authors re-examined an isolated right sternal plate excavated in 1999 near Iwaki in Japan\u2019s Fukushima prefecture.<\/p>\n

The fossil comes from the Ashizawa Formation<\/a>, part of the Futaba Group, a roughly 90-million-year-old layer of sandstone and mudstone deposited on an ancient seabed.<\/p>\n

The specimen had sat unstudied for over two decades after being tentatively labeled a hadrosauroid (duck-billed) dinosaur bone.<\/p>\n

The paleontologists determined the hatchet-shaped bone belongs to an indeterminate styracosternan<\/a>, a broad group within Iguanodontia that includes hadrosauroids and their close relatives.<\/p>\n

Its features closely resemble those seen in more derived iguanodontian species rather than in primitive ones.<\/p>\n

Based on comparisons with the sternal bones of related species, the researchers estimate this iguanodontian dinosaur measured only about 3 m (10 feet) in body length, making it small by the standard classification scheme for these dinosaurs.<\/p>\n

\u201cThis is significantly smaller than that of other iguanodontian fossils previously unearthed from the same formation,\u201d they said.<\/p>\n

\u201cBecause larger iguanodontians, including hadrosauroids, are known to have existed in Japan during the Late Cretaceous, the discovery suggests that iguanodontians of varying body sizes inhabited the coastal environments of East Asia.\u201d<\/p>\n

\u201cThe finding provides new insights that further corroborate the diversity of ancient coastal ecosystems.\u201d<\/p>\n

The team\u2019s results<\/a> were published on July 6 in the journal Paleontological Research.<\/p>\n

_____<\/p>\n

Masami Kondo et al. 2026. An iguanodontian sternal plate from the Upper Cretaceous Ashizawa Formation (Futaba Group) of Fukushima Prefecture, Japan. Paleontological Research 30: 122-134; doi: 10.2517\/prpsj.250042<\/p>\n","protected":false},"excerpt":{"rendered":"A fossilized bone unearthed two decades ago in northeastern Japan belongs to one of the smallest iguanodontian dinosaurs…\n","protected":false},"author":2,"featured_media":77654,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[49790,49791,10707,5235,10709,625,49792,8,49793,49794],"class_list":["post-77653","post","type-post","status-publish","format-standard","has-post-thumbnail","category-japan","tag-ashizawa-formation","tag-bone","tag-cretaceous","tag-dinosaur","tag-fossil","tag-fukushima","tag-iguanodontia","tag-japan","tag-sternal-plate","tag-styracosterna"],"_links":{"self":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/77653","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/comments?post=77653"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/77653\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media\/77654"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media?parent=77653"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/categories?post=77653"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/tags?post=77653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}