Aegirocassis benmoulai

Overview

Aegirocassis was NOT a sea scorpion—it was something even more amazing! This 2-meter giant was an anomalocaridid, part of a bizarre group of ancient predators that ruled the seas over 480 million years ago during the Ordovician period. But unlike its predatory relatives, Aegirocassis was a gentle giant that filter-fed like a whale!

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Taxonomy & Classification

• Phylum: Arthropoda (probably)
• Family: Hurdiidae
• Diet: Filter feeder (plankton)
• Lifestyle: Swimming marine animal

Aegirocassis was related to Anomalocaris—but with a very different lifestyle!

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Physical Characteristics

Giant Filter Feeder

• Length: About 2 meters (6.5 feet)
• Weight: Approximately 40 kg (88 lbs)
• Body: Segmented with swimming flaps
• Size: One of the largest animals of its time!

Body Features

• Two pairs of swimming flaps per body segment (unique!)
• Large, net-like appendages for filtering plankton
• Compound eyes for detecting food
• Segmented body with multiple swimming lobes
• No fearsome grabbing claws like its relatives!

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Ancient Whale of the Ordovician

Filter Feeding Pioneer

Aegirocassis was like an ancient whale:

• Swept water through net-like appendages
• Caught plankton and small organisms
• Didn't chase or grab prey
• Cruised slowly, filtering the seas
• First known giant filter feeder!

Animal	Feeding Style	Era
Aegirocassis	Filter feeding	480 million years ago
Whale sharks	Filter feeding	Today
Baleen whales	Filter feeding	Today

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The Anomalocaridids

Aegirocassis's Terrifying Relatives

Most anomalocaridids were predators:

• Anomalocaris—grabbed prey with spiny appendages
• Hurdia—had a large frontal shield
• Laggania—another fearsome hunter

Aegirocassis evolved filter feeding from these predatory ancestors!

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Revolutionary Discovery

Changing What We Knew

Before Aegirocassis, scientists thought:

• Anomalocaridids were only predators
• Giant filter feeders evolved much later
• Early ecosystems were simpler

Aegirocassis proved:

• Filter feeding evolved very early
• Ecosystems were more complex than thought
• Ecological niches appeared sooner

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Two Pairs of Flaps!

Unique Body Design

Aegirocassis had something special:

• Two pairs of swimming flaps per segment
• Most arthropods have one pair per segment
• Showed how early arthropod bodies could be more complex
• Helped scientists understand limb evolution!

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Discovery

Found in Morocco

• Discovered in the Fezouata Formation, Morocco
• Described in 2015
• Named for Moroccan fossil hunter Mohamed Ben Moula
• Exceptionally preserved with soft tissues
• One of the most important finds of the decade!

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Ordovician Oceans

Aegirocassis's World

480 million years ago:

• No life on land yet
• Oceans full of trilobites and early fish
• Plankton blooms provided food
• Morocco was underwater and tropical
• Very different from today's world!

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Size Comparison

Giant of Its Time

Ordovician Animal	Size
Aegirocassis	2 meters
Large trilobites	30-70 cm
Orthocone nautiloids	up to 6m
Early fish	10-30 cm

One of the largest animals swimming in Ordovician seas!

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Cool Facts

• Aegirocassis was the first known giant filter feeder!
• Its filtering appendages were like fine mesh nets
• Had two pairs of flaps per segment—unique!
• Related to scary predators but ate tiny plankton
• Named after a Moroccan fossil hunter
• Preserved so well scientists could see internal organs
• Proved complex food webs existed 480 million years ago
• Sometimes called the "whale of the Ordovician"

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Aegirocassis was proof that nature invented the gentle giant early on—a 2-meter filter feeder cruising ancient seas long before whales or whale sharks ever evolved!