Paragigantopora, Martino & Rosso & Taylor & Chiu & Fujita & Kitamura & Yasuhara, 2025

Genus PARAGIGANTOPORA gen. nov. Di Martino, Rosso and Taylor zoobank.org/ A4286261-AE35-4FA4-BC49-48C5B7B52A6F

Type species. Paragigantopora echinata gen. et sp. nov. Di Martino, Rosso and Taylor.

Etymology. Greek prefix ‘ para- ’, meaning next to, referring to its resemblance to Gigantopora Ridley, 1881 .

Diagnosis. Colony erect with rod-like branches and autozooids arranged in alternating longitudinal rows. Frontal shield tubercular, centrally imperforate with only marginal areolar pores, with some extending onto the proximal portion of the shield. Primary orifice surrounded on three sides by a raised, tubular peristome facing upwards and outwards, with peristomial bridge and large spiramen proximally. Spines absent. Avicularia, single or paired, on the sides of the peristome. Ooecium imperforate, opening into the peristome above the primary orifice.

Remarks. A new genus is introduced here to accommodate Paragigantopora echinata sp. nov., a Gigantopora -like species lacking pseudopores and having an imperforate ooecium. Additionally, the new combination Paragigantopora grandis (Gordon and Taylor, 2015) is suggested for an Eocene species, described from the Chatham Islands of New Zealand, sharing these features. Ridley (1881, p. 47) defined Gigantopora as having encrusting colonies, prominent autozooids with nodular frontal shields pierced by pseudopores, upwardly and outwardly directed tubular peristomes, single or paired avicularia flanking the peristome, a distinctive roundish, transversely broad pore visible frontally, and a small, globular, pseudoporous ooecium. While the new species and the fossil from the Chatham Islands are consistent with the diagnosis of Gigantopora in relation to the peristomial characteristics, including placement of the avicularia and the presence of a large spiramen, they differ in colony morphology, being erect rather than encrusting, and in frontal shield features. We agree with Gordon and Taylor (2015) in considering these ‘almost imperforate’ species as a more plesiomorphic form of Gigantopora , yet we propose that these distinctive traits necessitate the creation of a new genus within the Gigantoporidae . Similar actions have been taken previously in analogous situations, such as the introduction of Parkermavella Gordon and d’Hondt, 1997 for Schizomavella -like species with imperforate frontal shields, albeit with an umbonuloid distinction in that case. This pattern is observed in other families as well, like the Smittinidae , where genera such as Smittina are characterized by fully pseudoporous frontal shields, while Smittoidea and Hemismittoidea possess only marginal pores. Several species currently assigned to Gigantopora share certain traits with the new genus but not in its unique combination, simultaneously deviating from the typical diagnosis of Gigantopora . For instance, G. oropiscis Gordon and d’Hondt, 1997 is erect, yet has a proximally pseudoporous frontal shield and numerous marginal pores in the ooecium. Gigantopora foraminosa Hayward and Cook, 1983 , and G. spathula Hayward and Winston, 2011 also have erect colonies but otherwise conform to the standard appearance of Gigantopora . An unusual Gigantopora is G. profunda Harmer, 1957 , which is erect and cylindrical, with an imperforate frontal shield and an ooecium with only marginal pores, differing from species assigned to Paragigantopora gen. nov. in the position of avicularia, which are generally unilaterally placed at the base of the peristome on the marginal furrows outlining the zooidal perimeters. Gigantopora kirkpatricki Hayward, 1988 has an imperforate ooecium but its frontal shield is fully pseudoporous. Two other species, G. proximalis hispida d’Hondt, 1986 and G. verrucosissima Moyano, 2002 , have prominently tubercular frontal shields that are also fully pseudoporous. Among the remaining genera in the family, Cosciniopsis Canu and Bassler, 1927 , and Hemicosciniopsis Vigneaux, 1949 , have pseudoporous frontal shields and lack a peristomial bridge and spiramen, while Barbadiopsis Winston and Woollacott, 2009 , is distinguished by avicularia raised on swollen, pseudoporous cystids, with the rostra surrounding the orifice and meeting over it, small pores in the ooecium that can be obscured by proceeding calcification, and a rounded (not tubular) peristome.