Distinguishing features

Macrophiothrix species are difficult to distinguish in the field because microscopic examination of characters is necessary. Most species in the genus are large (disc diameter can be more than 20 mm), have very long arms, and live on soft sediment under slabs of rubble.

Macrophiothrix propinqua is one of the smaller species of the genus with maximum known disc diameter only 11 mm. It also has has relatively short arms, 6 to 14 times the disc diameter. The specimen photographed above is a large one for this species, with disc diameter about 10 mm and arms less than ten times that length. Radial shields (five pairs of conspicuous triangular disc plates) are bare and the widest part is near the edge of the disc. The rest of the disc surface can also be bare or it can be armed with low, rough granules as in the photographed specimen. Dorsal arm plates are wide and fan-shaped with a tendency for the distal edge to have three lobes. The arms are banded brown and red and there is also usually a paler or darker longitudinal midline.

Size

Depth range

Synonyms

Distribution

Web resources

References