Peromelissa Haeckel 1881

Genus Peromelissa Haeckel, 1881, emend. Petrushevskaya, 1971, sensu Matsuzaki et al., 2015

(= Psilomelissa Haeckel, 1881; = Micromelissa Haeckel, 1887; = Dimelissa Campbell, 1951)

Type species: Peromelissa phalacra Haeckel, 1887

Description. Lophophaenidae with two segments, and constriction between cephalis and thorax, above the median bar. The apical spine runs along the outside of the cephalis rather than existing free within it (as in Lithomelissa). The cephalis may have similar pore structure to the thorax, or be hyaline toward the top (as in Peromelissa phalacra Haeckel 1887). The apical spine may protrude out the top of the cephalis, or end on along the cephalic wall. The dorsal, left lateral, and right lateral spines extend outside the shell at approximately the same angle. These spines are typically as strong, or stronger, than the apical spine.

Remarks. This genus was first described vaguely by Haeckel (1882) as a two-segmented skeleton with a smooth cephalis, and a rounded thorax with three lateral spines. No species were placed into this genus until Haeckel (1887). In 1887, Haeckel added that Peromelissa does not have a cephalic horn; however, subsequent observations (i.e., Petrushevskaya 1971) have shown that Peromelissa does indeed have a cephalic horn, though it can vary greatly in size and strength. The type species was designated as Peromelissa phalacra Haeckel, 1887 by Campbell (1954). In Petrushevskaya (1971) ’s analysis of the internal skeletal structure of the type species, she observed that Peromelissa phalacra Haeckel, 1887 does have an apical horn, and also emended the genus definition to include forms with an open thorax, which were originally excluded from Haeckel’s 1882 and 1887 diagnoses. Petrushevskaya’s emendation thus nullified the differences between Peromelissa Haeckel, 1881, Psilomelissa Haeckel, 1881, Micromelissa Haeckel, 1887, and Dimelissa Campbell, 1951. She suggested that all of these names should be united under Peromelissa Haeckel 1881, which was adopted and further clarified by Matsuzaki et al. (2015). Here we follow Matsuzaki et al. (2015) ’s description, and agree with these authors’ statement that Peromelissa differs from Lithomelissa in that the apical spine is not free within the cephalis. However, neither Petrushevskaya (1971) nor Matsuzaki et al. (2015) explicitly state why Peromelissa conflicts with Lophophaena. It is our opinion that the species currently in Peromelissa are as similar to Lophophaena species as they are to each other, and there is no specific characteristic that separates them. For the sake of avoiding further confusion, we retain the genus Peromelissa for the described species observed during this study, but do not place any of our new species in this problematic genus.

In this study we observed the following valid species of Peromelissa: Peromelissa phalacra Haeckel, 1887 and Peromelissa thoracites (Haeckel) Matsuzaki et al., 2015. Although it was not observed in this study, Micromelissa apis Haeckel, 1887 should likely be transferred to Peromelissa, due to the genus-level synonymizations of Petrushevskaya (1971) and Matsuzaki et al. (2015). We do not include Peromelissa crassa Tan, 1927, because the illustration does not appear to depict a lophophaenid. Peromelissa psilocrana Haeckel, 1887 was only briefly described but not illustrated, and to our knowledge has never been subsequently used by other authors, making it likely a nomen oblitum. Peromelissa capito (Ehrenberg) Haeckel, 1887 was transferred from Lithomelissa, but as no justification was given by the author and the existing illustrations are vague, we do not follow this transfer here.

Range. ?Late Miocene–Recent