{"id":1548,"date":"2026-08-28T05:53:00","date_gmt":"2026-08-27T20:53:00","guid":{"rendered":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-08-28-chosha-amphibious-stem-insect-en\/"},"modified":"2026-08-28T05:53:00","modified_gmt":"2026-08-27T20:53:00","slug":"2026-08-28-chosha-amphibious-stem-insect-en","status":"publish","type":"briefing","link":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-08-28-chosha-amphibious-stem-insect-en\/","title":{"rendered":"Modern insects have six legs; this 324-million-year-old insect had 18 more paddle-like legs on its abdomen"},"content":{"rendered":"

2026-08-28 05:53 KST<\/strong><\/p>\n

The approximately 324 million-year-old fossil from West Texas, USA, was an early insect with six walking legs on its chest and 18 additional small, oar-like legs on its abdomen. The researchers named the new species ‘Chosha praecursor’ and classified it as an early-diverging insect that traveled between water and land.<\/p>\n

This doesn’t mean we’ve found a single direct ancestor of today’s insects. Based on a few preserved adult female fossils and morphological phylogenetic analysis, it was placed on a nearby branch of the insect stem, and whether the abdominal appendages actually functioned as swimming or gills was inferred from the morphology.<\/p>\n

Why didn’t I see it as an insect at first?<\/h2>\n

This fossil has long been interpreted as a crustacean larva because of its multi-segmented abdominal appendages. The researchers re-examined the ovipositor, tail thread, antennae, and thorax structures using polarized light imaging. Together, these features fit better into early insects than crustaceans.<\/p>\n

how big was your body<\/h2>\n

The body length of the adult female that the researchers looked at in detail was 32.09 mm. Including the center tail thread and tail hairs on both sides, the total length reached 49.66 mm. It looks big in the picture, but in reality it was about the size of a few finger joints.<\/p>\n

\"Modern
This AI-generated image explains the topic; it is not a photograph of the actual event, observation, or experiment.<\/figcaption><\/figure>\n

How do you count 24 legs?<\/h2>\n

Like modern insects, it had three pairs of walking legs on its thorax, or six. Here, a total of 18 small appendages remained, one pair for each of the nine segments of the abdomen. It has been suggested that the abdominal appendages have wide oar-like ends, which may have helped them move underwater or breathe.<\/p>\n

How to change the history of insect landings<\/h2>\n

Molecular clocks date back when hexapods diverged from their marine crustacean relatives, but there are major gaps in the body fossils. Chosha and other early fossils show that fully terrestrial insects did not appear all at once, but likely went through a semi-aquatic stage and lost their belly legs.<\/p>\n

What do you not know yet?<\/h2>\n

No tissue from the abdominal appendages remains, making it impossible to directly examine their exact function. We need to find more fossils from other regions during the same period to know whether this body structure was widespread. The researchers’ phylogenetic position may also change depending on new data, so it should be read as ‘one of the earliest definitive insects.’<\/p>\n

Primary sources and independent checks<\/h2>\n

Nature original paper<\/a><\/p>\n

Chinese Academy of Sciences NIGPAS official release<\/a><\/p>\n

Science News independent report<\/a><\/p>\n

El Pa\u00eds independent report<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

The Texas fossil Chosha praecursor had 18 small paddle-like appendages on its abdomen in addition to six walking legs on its thorax. The researchers interpreted it as an early-diverging insect that lived a semi-aquatic life.<\/p>\n","protected":false},"featured_media":0,"template":"","meta":[],"class_list":["post-1548","briefing","type-briefing","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing\/1548","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing"}],"about":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/types\/briefing"}],"wp:attachment":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/media?parent=1548"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}