It is the only madtom with heteromorphic sex chromosomes. Diplobiontic green algae include isomorphic and heteromorphic forms. In plants with heteromorphic gametophytes, there are two distinct kinds of gametophytes. Empirical evidence supports a role for heteromorphic sex chromosomes in hybrid sterility and inviability. "Porphyra" displays a heteromorphic alternation of generations. However, not all heteromorphic gametophytes come from heterosporous plants. The thin shelled heteromorphic ammonites probably lived at depths . This type of life cycle is known as a complex heteromorphic life cycle. A distinct SI mechanism exists in heterostylous flowers, termed heteromorphic self-incompatibility. In heteromorphic algae, the morphology and size are different in the gametophyte and sporophyte. They also have a heteromorphic pair of central microtubules in the anterior axoneme. Most Foraminifera undergo a heteromorphic alternation of generations between haploid gamont and diploid agamont forms. Most plants, as well as many groups of animals, lack heteromorphic sex chromosomes. "Macrocystis integrifolia" alternates heteromorphic phases from a macroscopic sporophyte to dioecious microscopic gametophytes. However, heteromorphic sex chromosomes are relatively rare, with only 5 species known as of 2014.