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Chondracanthus exasperatus is a red alga in the Division Rhodophyta, assigned to all red algae. It is in the diverse Order Gigarinaceae in the Class Rhodophyceae in the Family Chondracanthus. Up until recently it was in the family Gigartinaceae and referred to as Gigartina exasperate. The family Chondracanthus was recently introduced as part of a larger effort to reclassify the Gigartinales.
Chondracanthus exasperatus has one or more large, broad, thick blades that are commonly 30 – 50 cm tall and 10 – 20 cm wide, though they can grow to 1 m tall and 30 cm wide. The blades are purplish-red, but when submerged, they exhibit a striking bluish iridescence. The blade shape usually tapers towards each end. The distinguishing feature of this alga is that both sides of the blades are covered with numerous protuberances, called papillae, which are associated with reproductive structures. These dense papillae give the blade the appearance of a thick bath towel, bestowing the species its common name Turkish Towel. The blades arise from a small stipe that is sometimes branched and the whole plant attaches itself to the substrate by means of a disc shaped holdfast. The holdfast may vary in size from a few millimeters to several centimeters in diameter.
Three varieties of Chondracanthus exasperatus have been identified and distinguished according to blade morphology. In the northern parts of its range, the blades have extremely irregular edges. Central California individuals have very thick blades and are often found in close proximity, even at times overlapping with other specimens. The southern specimens are instead more widely spaced.
Chondracanthus exasperatus can grow to 1 m tall and 30 cm wide, but is more commonly 30 – 50 cm tall and 10 – 20 cm wide.