Wiwaxia corrugata

Overview

Wiwaxia is one of the strangest creatures from the Cambrian Explosion, living approximately 508 million years ago. This bizarre armored slug-like animal was covered in overlapping scales and tall defensive spines, making it look like a tiny underwater hedgehog or porcupine. Found primarily in the famous Burgess Shale of Canada, Wiwaxia has puzzled scientists for over a century about where it fits in the tree of life.

---

Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Mollusca (stem group, debated)
• Period: Middle Cambrian (~508 million years ago)
• Diet: Herbivore/Detritivore

Wiwaxia's classification has been hotly debated—it may be an early relative of mollusks (slugs, snails, clams) based on its mouthparts and growth patterns.

---

Physical Characteristics

Size & Shape

• Length: 2 to 5.5 centimeters
• Shape: Oval, bilaterally symmetrical
• Body: Slug-like with flat underside for crawling
• No distinct head or tail visible from above

Armor System

Wiwaxia had an incredible defensive covering:

• Sclerites: Scale-like plates arranged in about 50 rows covering the body
• Dorsal spines: Two rows of 7-11 tall blade-like spines on its back
• Ribbed texture: Each sclerite has striated, ribbed surface
• Sclerites and spines inserted directly into the body wall

Possible Iridescence

The ribbed surface of the sclerites has led scientists to speculate that Wiwaxia may have been iridescent and colorful, shimmering as it moved across the seafloor!

---

Defense Against Predators

Spiny Protection

• The long dorsal spines provided protection against predators
• Fossils show broken spines, suggesting successful defense against attacks
• Probably deterred predators like Anomalocaris
• The sclerite armor protected the soft body underneath

---

Feeding & Lifestyle

How It Ate

• Had a radula-like feeding apparatus (similar to snails)
• Two or three rows of backward-pointing teeth
• Grazed on microbial mats on the seafloor
• Scraped organic material from surfaces

Movement

• Crawled slowly on its flat underside
• Probably similar to how slugs and snails move today
• Lived on the muddy Cambrian seafloor

---

Discovery & History

Finding Wiwaxia

• First described in 1899 by G.F. Matthew from a single spine
• First complete specimen found in 1911 by Charles Walcott
• Named after Wiwaxia Peak in the Canadian Rockies
• Thousands of specimens now known from the Burgess Shale

---

The Classification Debate

Mollusc or Annelid?

Scientists argued for decades:

• Mollusc camp: Mouthparts and body structure suggest slug relatives
• Annelid camp: Scale-like covering resembles certain polychaete worms
• Current consensus: Most evidence now supports mollusc affinity
• Wiwaxia is likely a stem-group mollusc—an early branch before modern molluscs evolved

---

The Cambrian World

Wiwaxia's Environment

The Burgess Shale preserved an incredible ecosystem:

• Lived alongside Anomalocaris, Hallucigenia, Opabinia
• Microbial mats covered the seafloor
• Mudslides occasionally buried and preserved these soft-bodied creatures
• One of the best windows into Cambrian life

---

Cool Facts

• Wiwaxia may have been shimmery and iridescent like a tiny underwater disco ball!
• Its broken spines in fossils prove it survived predator attacks
• Scientists argued for 100+ years about what it was related to
• Named after a mountain peak, not a scientist
• Could have up to 22 tall spines on its back
• One of the most iconic Burgess Shale fossils
• Shows that mollusks once looked very different from today's snails and slugs

---

Wiwaxia reminds us that early animal evolution produced incredible diversity—this spiny, armored slug-creature represents a time when mollusks were experimenting with body plans we can barely imagine today!