--- title: What Is the Largest Animal: This Sea Creature Was Once Seven Feet description: The newly discovered aegirocassis benmoulae looks a bit like both a shrimp and a lobster. But, at 7-feet-long, this animal was no shrimp. canonical: https://time.com/3745687/giant-sea-creature-fossil-ocean/ author: Justin Worland article:opinion: false article:content_tier: free article:published_time: 2015-03-16T14:06:32.000Z article:modified_time: 2026-08-04T08:06:22.617Z article:section: Science og:title: What Is the Largest Animal: This Sea Creature Was Once Seven Feet og:description: The newly discovered aegirocassis benmoulae looks a bit like both a shrimp and a lobster. But, at 7-feet-long, this animal was no shrimp. og:url: https://time.com/3745687/giant-sea-creature-fossil-ocean/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt71af69123f241226/698783a2428a9e28eacc7a14/giant-sea-creature.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2027 og:image:height: 1140 og:image:alt: An artist's rendering of a filter-feeding Aegirocassis benmoulae from the Ordovician Period feeding on a plankton cloud. og:type: article twitter:card: summary_large_image twitter:title: What Is the Largest Animal: This Sea Creature Was Once Seven Feet twitter:description: The newly discovered aegirocassis benmoulae looks a bit like both a shrimp and a lobster. But, at 7-feet-long, this animal was no shrimp. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt71af69123f241226/698783a2428a9e28eacc7a14/giant-sea-creature.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # This Giant Sea Creature Was Once Earth's Largest Animal ## Video: Overstepping Boundaries: The Danger of Invasive Species [Watch (HLS stream): Overstepping Boundaries: The Danger of Invasive Species](https://cdn.jwplayer.com/manifests/zHyAT7e9.m3u8) (2:18)  _Published 2013-12-04. What are invasive species, and why are they dangerous? TIME's Bryan Walsh explains how animals like the Asian carp, lionfish, and Burmese python can be a threat._  by [Justin Worland](https://time.com/author/justin-worland/)  ## Justin Worland Senior Correspondent Mar 16, 2015 2:06 PM UTC  An artist's rendering of a filter-feeding Aegirocassis benmoulae from the Ordovician Period feeding on a plankton cloud. An artist's rendering of a filter-feeding Aegirocassis benmoulae from the Ordovician Period feeding on a plankton cloud.Marianne Collins—ArtofFact/Reuters  by [Justin Worland](https://time.com/author/justin-worland/)  ## Justin Worland Senior Correspondent Mar 16, 2015 2:06 PM UTC The newly pieced together skeleton of _Aegirocassis benmoulae,_ a 480-million-year-old sea creature, looks a bit like a cross between a shrimp and a lobster. But at 7-feet-long, this animal was no shrimp. In fact, it was likely [once the largest animal on earth](http://www.nature.com/articles/nature14256.epdf?referrer%5Faccess%5Ftoken=A9f7MUk0YtIcIz3NpcblftRgN0jAjWel9jnR3ZoTv0PcsBOGlcL6Hrtr0U11H0%5FeXdYWHwdwJRKlhS%5FG13Gs8IDB1SHQHV5ked7GPSnOSaRkFfY%5F1Vdma8HFy8Y7a59l-CtstasmEoMgUHwU7mzr7NVuZn5OBHUxyt%5FytncDYtpaAfbhchnB%5F%5FOdgRicLxDU-ndO-uxZ7YyaQSjtiJUoVOex2w%5FNTbY3S9gtJd5fhJTg1Q1BSq7DFrZkrdl9XCBL&tracking%5Freferrer=news.sciencemag.org). The fossil’s discovery in Morocco, outlined in a _Nature_ article last week, sheds new light on arthropods from the palaeozoic era, or from about 542 million years ago to 251 million years ago. The _Aegirocassis_ has a second set of fins unlike previously thought, and while many similar arthropods would actively seek out prey, the _Aegirocassis_ captured plankton through a net-like appendage_._ But don’t worry: Its method of feeding likely made the _Aegirocassis_ relatively easy going, despite its size, researchers told [Reuters](http://www.reuters.com/article/2015/03/11/us-science-creature-idUSKBN0M725O20150311). “Given the huge size of _Aegirocassis_ and its very alien appearance, I assume most people would probably be terrified if they’d encounter it while swimming,” said Yale University paleontologist Peter Van Roy, a study author. However, contrary to almost all other anomalocaridids which were active predators, our animal would have been a very peaceful guy.” ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/3745687/giant-sea-creature-fossil-ocean/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/3745687/giant-sea-creature-fossil-ocean/"},"headline":"This Giant Sea Creature Was Once Earth's Largest Animal","datePublished":"2015-03-16T14:06:32.000Z","dateModified":"2026-08-04T08:06:22.617Z","description":"This 480-million-year-old Aegirocassis was 7 feet long","url":"https://time.com/3745687/giant-sea-creature-fossil-ocean/","keywords":["animals"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt71af69123f241226/698783a2428a9e28eacc7a14/giant-sea-creature.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Justin Worland","jobTitle":"Senior Correspondent","url":"https://time.com/author/justin-worland/"}],"articleSection":"Science","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt71af69123f241226/698783a2428a9e28eacc7a14/giant-sea-creature.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"An artist's rendering of a filter-feeding Aegirocassis benmoulae from the Ordovician Period feeding on a plankton cloud.","caption":"An artist's rendering of a filter-feeding Aegirocassis benmoulae from the Ordovician Period feeding on a plankton cloud.","creditText":"Marianne Collins—ArtofFact/Reuters","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/science/","name":"Science"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/animals/","name":"animals"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/3745687/giant-sea-creature-fossil-ocean/","name":"This Giant Sea Creature Was Once Earth's Largest Animal"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Overstepping Boundaries: The Danger of Invasive Species","description":"What are invasive species, and why are they dangerous? 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