{"id":580565,"date":"2026-04-02T10:42:26","date_gmt":"2026-04-02T10:42:26","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/580565\/"},"modified":"2026-04-02T10:42:26","modified_gmt":"2026-04-02T10:42:26","slug":"500-million-year-old-spider-relative-has-claws-where-it-shouldnt","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/580565\/","title":{"rendered":"500-million-year-old spider relative has claws where it shouldn\u2019t"},"content":{"rendered":"

The fossil was completely unremarkable. That\u2019s what Harvard University paleontologist Rudy Lerosey-Aubril initially thought while examining an arthropod fossil dating back to the Cambrian period<\/a> (538.8 million to 485.4 million years ago).<\/p>\n

\u201cAs I prepared it, however, it unexpectedly revealed exquisitely preserved limbs\u2014including a pair of frontal claws projecting from the head,\u201d Lerosey-Aubril<\/a> tells Popular Science.<\/p>\n

Early arthropod specimens don\u2019t have claws like these. Instead, Cambrian arthropods usually have an antenna in that position. In other words, the claws Lerosey-Aubril was seeing were not supposed to be there.<\/p>\n

This unassuming fossil belongs to Megachelicerax cousteaui, a 500-million-year-old sea predator. The fossil was first dug up over 40 years ago in a desert in western Utah and is the oldest known chelicerate\u2014the arthropod group that includes modern spiders, scorpions, horseshoe crabs, and sea spiders. This single strange specimen pushes the evolutionary history of chelicerates back by 20 million years and helps explain the evolution of claws. The findings are detailed in a study published today in the journal Nature<\/a>.<\/p>\n

Here come the claws<\/p>\n

A co-author of the new study, Lerosey-Aubril spent over 50 hours cleaning the M. cousteaui fossil with a needle underneath a microscope to study its surprising anatomy. Its body is just over three-inches-long and has an exoskeleton made up of one head shield on top and nine separate body segments.<\/p>\n

\u201cAppendages beneath the head are adapted for feeding and sensory functions, while those along the trunk are used for respiration and swimming,\u201d Lerosey-Aubril explains. \u201cThis degree of anatomical specialization is surprisingly advanced for an arthropod of this age.\u201d<\/p>\n

Chelicerate arthropods<\/a> have a body divided into a cephalothorax on top and abdomen on bottom, four pairs of walking legs, and two front chelicerae and pedipalps to grab things. Before this discovery, the oldest known chelicerate arthropods dated back roughly 480 million years ago. M. cousteaui lived 20 million years earlier, making it the earliest known offshoot of the chelicerate family tree. Today, there are more than 120,000 living chelicerate species, including spiders and horseshoe crabs.<\/p>\n

\"an<\/p>\n

Megachelicerax cousteaui was an aquatic predator that lived 500 million years ago. Image: Artistic reconstruction by Masato Hattori (\u00a9 Harvard University).<\/p>\n

Just keep digging<\/p>\n

Despite the fossil\u2019s age, Lerosey-Aubril\u00a0 was surprised by just how much more modern M. cousteaui looks compared to animals living around the same time, including trident-wielding trilobites<\/a>.<\/p>\n

\u201cApart from a few telltale features of its antiquity, this half-a-billion-year-old chelicerate would look right at home in today\u2019s oceans,\u201d he says.<\/p>\n

M. cousteaui is also a key transitional species that bridges Cambrian arthropods that don\u2019t have these front claw-likes with the much younger horseshoe crab-like chelicerates who did have claws.<\/p>\n

\"a<\/p>\n

Modern day spider next to the Megachelicerax cousteaui fossil. Image: Rudy Lerosey-Aubril.<\/p>\n

Previously, scientists were not sure about the order in which claws and a body with two regions that perform specific functions first evolved. M. cousteaui shows that they evolved before these head appendages disappeared and became more similar to the legs on today\u2019s spiders.<\/p>\n

\u201cIt reconciles several competing hypotheses; in a way, everybody was partly right,\u201d study co-author Javier Ortega-Hern\u00e1ndez<\/a>, Curator of Invertebrate Paleontology at Harvard\u2019s Museum of Comparative Zoology, explained in a statement<\/a>.<\/p>\n

Megachelicerax cousteaui is named in honor of famed French explorer Jacques-Yves Cousteau whose documentaries and environmental advocacy inspired generations to keep exploring. Lerosey-Aubril says that the fossil itself is also a reminder to keep digging.<\/p>\n

\u201cThis particular fossil was discovered by a dedicated avocational paleontologist [Lloyd Gunther] and later donated to a museum, where it was carefully curated for decades before we were fortunate enough to reveal its scientific significance,\u201d he says. \u201cFossils are found across much of the United States, so get out, explore, and see what stories might be hidden in the rocks around you.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"The fossil was completely unremarkable. That\u2019s what Harvard University paleontologist Rudy Lerosey-Aubril initially thought while examining an arthropod…\n","protected":false},"author":2,"featured_media":580566,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[64,63,284540,284541,284539,284538,284537,128,338],"class_list":{"0":"post-580565","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-wildlife","8":"tag-au","9":"tag-australia","10":"tag-cambrian-period","11":"tag-claws","12":"tag-horseshoe-crabs","13":"tag-lerosey-aubril","14":"tag-rudy-lerosey-aubril","15":"tag-science","16":"tag-wildlife"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/580565","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=580565"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/580565\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/580566"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=580565"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=580565"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=580565"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}