---
title: Imperial Pencil Urchin (Phyllacanthus imperialis)
scientific_name: Phyllacanthus imperialis
common_name: Imperial Pencil Urchin
taxon: Sea urchin
published: 2026-08-09T06:00:11.363Z
updated: 2026-08-09T07:02:59.893Z
tags: Imperial Pencil Urchin, Phyllacanthus imperialis, Sea urchin, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/echinoderms/sea-urchin/imperial-pencil-urchin
---

# Imperial Pencil Urchin (*Phyllacanthus imperialis*)

## Quick facts

- **Group:** Sea urchin (*Echinoidea*)
- **Size:** up to 17 cm across
- **Depth:** 3-40 m
- **Diet:** Omnivore
- **Activity:** Nocturnal
- **Rarity:** Uncommon
- **Habitat:** Caves, overhangs and rubble on reef slopes
- **Reproduction:** Broadcast spawner, Gonochoric

## How to recognise it

- thick cylindrical spines like blunt pencils
- spines pale with dark bands, often encrusted
- small test carried on comparatively huge spines
- diameter up to 17 cm including spines

The largest pencil urchin here, reaching about 17 cm (7 in) including the spines, which are thick cylindrical rods, pale with dark banding, radiating from a comparatively small test. They look and feel like blunt pencils - solid, smooth and quite unlike the brittle needles of the urchins that share the same rubble.

It spends daylight jammed into caves and under overhangs, and grazes at night on algae, sponges and encrusting animals. The spines serve as anchors as much as armour: an urchin wedged into a crack braces against the rock with them and is very hard to pull free. Dead spines wash up on beaches and are recognisable by their heft and their ribbed surface - they were used as ornaments and tools in several cultures. The animal itself is harmless, with no venom and no sharp points.

## Also known as

- **English:** imperial urchin, Imperial Lance Urchin, pencil urchin, Imperial Sea Urchin, tiara-urchin
- **French:** Oursin-lance impérial
- **Italian:** Riccio matita imperiale
- **German:** Sputnik-Seeigel
- **Czech:** ježovka císařská
- **Japanese:** バクダンウニ
- **Russian:** Ёж-карандаш императорский

## Scientific synonyms

- *Cidaris (Phyllacanthus) imperialis* (Lamarck, 1816)
- *Cidaris fustigera* (A. Agassiz, 1963)
- *Cidaris imperialis* (Lamarck, 1816)
- *Cidaris imperialis fustigera* (A. Agassiz, 1863)
- *Cidarites imperialis* Lamarck, 1816
- *Leiocidaris imperialis* (Lamarck, 1816)
- *Phyllacanthus fustigera* A. Agassiz, 1863
- *Phyllacanthus fustigerus* A. Agassiz, 1863
- *Rhabdocidaris imperialis* (Lamarck, 1816)

## Range

Eastern Africa & Madagascar, Indian Ocean, Indo-Pacific, Kenya, Madagascar, Mozambique, New Zealand, Nuweiba, Philippines, Red Sea, Seychelles, South Africa, South Andaman Islands, South Pacific Ocean, Tanzania

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*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/echinoderms/sea-urchin/imperial-pencil-urchin)*
*Updated: August 9, 2026*