Ethymology :
      - Acantho = spiny; zoon = animal

Ventral characteristics :
      - The cerebral eyes lie in one horseshoe-shaped cluster
      - The pharynx is complexe with highly ruffled folds
      - Male copulatory apparatus single with seminal vesicle and armed penis papilla

Dorsal characteristics :
      - Flatworms of this genus have a papillate dorsal surface and a ruffled margin. The papillae are blunt or oblong pointed and may be contractile
      - The pseudotentacles are small, ear-like and pointed

Ethymology :
      - Phriko = folded, ceros = horns

Ventral characteristics :
      - The cerabral eyespot is round with up to 100 eyes in a clear area
      - The pharynx is small and has a simple fold
      - The male copulatory apparatus is single

Dorsal characteristics :
      - These flatworms have an elongate oval to oval body with a smooth dorsal surface and a margin with few deep ruffles
      - Pseudotentacles are square and rounded of two types : with two deep lateral ruffles or with several lateral ruffles

Ethymology :
      - Pseudo = false, ceros = horns

Ventral characteristics :
      - The cerebral eyes lie in one horseshoe-shaped cluster
      - The pharynx is highly ruffled with deep, complex folds
      - Male copulatory apparatus single with seminal vesicle and armed penis papilla

Feeding behavior :
      - They feed exclusively on colonial ascidians

Dorsal characteristics :
      - They have a smooth dorsal surface and are flat medially.
      - Body oval, blunt or tapering slightly posteriorly and have a few marginal ruffles.
      - Pseudotentacles are simple folds occuring in two forms ; either square (i.e. blunt), simple folds or pointed broad flaps formed from the anterior margin

(a) Pseudotentacle
    (b) Cerebral eyes

Ethymology :
      - Pseudo = false, bi = 2, ceros = horns

Ventral characteristics :
      - The cerebral eyes lie in one horseshoe-shaped cluster
      - The pharynx has simple folds
      - Male copulatory apparatus double each with seminal vesicle and armed penis papilla

Feeding behavior :
      - They feed on a variety of invertebrates such as molluscan gastropods and crustaceans by engulfing the prey whole

Dorsal characteristics :
      - They have a smooth dorsal surface and are deep bodied (raised) medially.
      - Body elongated oval, and have a highly ruffled margin
      - The pseudotentacle are well developed and are either ear-like and pointed or square and slightly ruffled laterally (without simple folds)

(a) Pseudotentacle
    (b) Cerebral eyes

Pseudobiceros includes the biggest and often most colourful of the polyclad flatworms.

This along with flamboyant colouration, is thought to be aposematic or warning behaviour advertising their suspected unpalatability to visual predators such as fish.

They are the only polyclads which actively swim with exaggerated undulations of their ruffled margin.

Pseudobiceros fulgor

Ethymology :
      - Thysa = tassel, a reference to the papillate dorsal surface; zoon = animal

Ventral characteristics :
      - The cerebral eyes lie in one horseshoe-shaped cluster
      - The pharynx is elongated with simple folds
      - Male apparatus double, with seminal vesicle and armed penis papilla

Dorsal characteristics :
      - Flatworms of this genus have a papillate dorsal surface and a very ruffled margin. The papillae are blunt or oblong pointed and may be contractile
      - The pseudotentacles are ear-like and pointed