Melanthalioideae Gurgel, J.N.Norris et Fredericq, 2018

Gurgel, Carlos Frederico D., Norris, James N., Schmidt, William E., Le, Hau Nhu & Fredericq, Suzanne, 2018, Systematics of the Gracilariales (Rhodophyta) including new subfamilies, tribes, subgenera, and two new genera, Agarophyton gen. nov. and Crassa gen. nov., Phytotaxa 374 (1), pp. 1-23 : 12

Gracilariaceae subfam. Melanthalioideae Gurgel, J.N.Norris et Fredericq , subfam. nov.

TYPE SPECIES: Melanthalia obtusata (Labillardière) J. Agardh 1852: 614 , basionym: Fucus obtusatus Labillardière 1805: 111 .

DIAGNOSIS: Algae free-living, with compressed to flattened, foliose thalli; tetrasporangia and superficial spermatangia in nemathecia; gonimoblasts small, gonimoblast mass expanded and amorphous, filling the entire cystocarp cavity; gradual and wide transition between gonimoblasts and carposporangia at different stages of maturity, carposporangia formed in long straight, largely unbranched chains; mature carposporangia similar in size with later stages of gonimoblast differentiation; tubular nutritive cells absent. New filaments interpolated by gonimoblast cells deep inside fertile region. Inner pericarp is well differentiated, and gonimoblast cells fuse directly with cells of the inner pericarp without the formation of secondary pit connections. An extensive fusion network is produced in the inner pericarp in Curdiea in which fusion takes place alongside the broadened pit connections. Spermatangia of cortical origin, spermatangial parent cells distributed superficially, along the thallus surface. Spermatangia of Melanthalia have not yet been reported; but have been described in Curdiea ( Nelson & Knight 1997).

REMARKS: The geographic distribution of this subfamily is so far restricted to Antarctica, Australia, New Zealand and New Caledonia (e.g., Fredericq & Hommersand 1989c, 1990a, b; Nelson et al. 2013).

GENERA IN GRACILARIACEAE SUBFAM. MELANTHALIOIDEAE : Melanthalia , and Curdiea .