Floridina antiqua ( Smitt, 1873 )

Martino, Emanuela Di, 2022, Revision of the type species of some cheilostome bryozoan genera in the collection of the Swedish Museum of Natural History, Zootaxa 5125 (2), pp. 157-181 : 160-163

Floridina antiqua ( Smitt, 1873)

( Fig. 2 ; Table 2)

Mollia antiqua Smitt, 1873: 12 , pl. II, fig. 73.

Floridina antiqua: Jullien 1882: 284 .

Material examined. Lectotype (designated here) SMNH-Type-1835a ( Fig. 2 ), and paralectotypes SMNH-Type-1835b, c; three colony fragments encrusting bivalve shells; Florida, United States; depth 53 m. Leg. L.F. Pourtales 1868. Based on the original label, these are the specimens drawn in Smitt (1873, pl. 2, fig. 73).

Description. Colony encrusting, multiserial, uni- to multilaminar due to self-overgrowth, extensive, consisting of hundreds of zooids ( Fig. 2A ).

Autozooids arranged quincuncially, distinct with thin interzooidal furrows between slightly raised edges, hexagonal or pentagonal, distal edge rounded, proximal edge straight to slightly convex if the zooid is budded distally, or pointed acute if budded distolaterally, longer than wide (mean L/ W 1.26) ( Fig. 2B–D ). Gymnocyst vestigial, visible along the zooidal margins only if slightly raised; cryptocyst extensive, occupying about half of zooidal frontal length, depressed and finely granular, outlined by a raised, striated rim, 35–60 µm wide.

Opesia occupying the remaining half of the zooidal length, bell-shaped with straight proximal margin ( Fig. 2D ), or trifoliate with more prominent lateral constrictions and opesiular indentations marked by slightly raised proximal margin, forming a trapezoidal process projecting into the opesia ( Fig. 2E ); an inner cryptocystal rim visible at the distal edge of the opesia in some non-ovicellate zooids ( Fig. 2C ); cryptocyst around the opesia with granules aligned in rows giving a striated appearance as along the zooidal margins.

Ovicellate zooids with distal edge formed either by the cryptocyst of the distal zooid ( Fig. 2C ), or sometimes cormidial and formed by the cryptocyst of the two distolateral, neighbouring autozooids ( Fig. 2E ), or an autozooid and a vicarious avicularium ( Fig. 2B ); opesia usually larger than in non-ovicellate zooids.

Vicarious avicularia infrequent (e.g. three avicularia out of 80 modules counted in a random portion of the colony; Fig. 2A ) but occasionally clustered ( Fig. 2B ), pentagonal with raised, rounded, triangular rostrum showing the lateral, smooth gymnocyst ( Fig. 2B ); cryptocyst finely granular and striated along the margins as in autozooids; opesia elliptical, drop-shaped or ovoidal, centrally placed; an unusual rectangular rostrum observed in one avicularium ( Fig. 2D ), probably a teratology resulting from colony reparation.

Intramural budding observed in autozooids and vicarious avicularia, visible as a double rim of striated cryptocyst ( Fig. 2E ).

Putative kenozooids irregularly polygonal, with narrow cryptocyst having the same texture as autozooids and vicarious avicularia, and large elliptical to subcircular opesia ( Fig. 2F ), likely to be reduced and almost closed later in ontogeny ( Fig. 2G ).

Ancestrula not observed.

Remarks. When describing its specimens from Florida, Smitt (1873) refers to the Madeiran specimens of Membranipora antiqua of Busk (1858) as being very similar, differing only in the more pointed distal margin of some zooids. Busk’s Membranipora antiqua was subsequently placed in Onychocella by Jullien (1882), and since then either considered as a distinct species or put in synonymy with O. angulosa and O. marioni ( Taylor et al. 2018) . Nonetheless, Jullien (1882) chose Smitt’s Mollia antiqua as the type species of his new genus Floridina .

Floridina antiqua is considered a warm-water widespread species. Compared to the type material, the specimen from Ghana illustrated in Taylor et al. (2018, fig. 11a) has avicularia with more pointed rostra and deeper opesiular indentations owing to the more extensive tongue formed by the proximal margin of the orifice and more pronounced lateral constrictions; the specimens from the Florida Oculina -reef also show deeper opesiular indentations, and avicularia with more pointed, sometimes channelled, rostra ( Winston 2016).

Di Martino et al. (2017) distinguished the Miocene Floridina subantiqua from the Chipola Formation of Florida based on two main characters: the lateral constrictions of the avicularium rostrum and the presence of a cryptocystal appendix projecting distally into the opesia. This latter feature was observed also in some zooids of the syntypes of F. antiqua ( Fig. 2B ), although it seems less developed and appears more arched, as a double, inner rim of the distal margin of the opesia.

Several teratologies have been observed in Smitt’s syntypes, such as the vicarious avicularium with an unusual rectangular rostrum ( Fig. 2D ), autozooids and vicarious avicularia with calcification scars and concentric striated rims of cryptocyst ( Fig. 2E ), autozooids irregularly shaped and with reversed polarity ( Fig. 2H ), as well as unusual polymorphs, interpreted as kenozooids, with opesia variable in size from very large, occupying most of the frontal surface ( Fig. 2F ), to extremely reduced ( Fig. 2G ). All these structures seem to be related to colony repair after damage probably due to predation or growth on an irregular substrate, as also seen in other Floridina species ( Di Martino et al. 2019). It is unlikely that the putative kenozooids, with reduced cryptocysts and extensive opesia, are incomplete autozooids given their position not at the growing edge, and with several rows of autozooids surrounding them both proximally and distally.

Floridina antiqua is not among the species re-described and illustrated by Winston (2005), which represents the most comprehensive revision of Smitt’s Floridan bryozoans and is based on the material housed in the collection of the Museum of Comparative Zoology of Harvard University.

Figures

FIGURE 2. Floridina antiqua (Smitt, 1873), Lectotype (designated here) SMNH-Type-1835a, Florida, United States. A. Portion of the colony including about 80 zooids and three vicarious avicularia. B. Group of autozooids, ovicellate zooids (note the ooecium formed by both the vicarious avicularium and the distal zooid, see asterisk), and vicarious avicularia with raised rostrum showing the smooth gymnocyst. C. Group of autozooids, ovicellate zooids (with ooecium formed by the distal zooid, see asterisk), and vicarious avicularia. D. Group of autozooids and vicarious avicularium with an unusual rectangular rostrum. E. Close-up of zooids, those ovicellate with ooecium formed by one (black asterisk) or two (white asterisk) distal zooids, avicularium with undulate, raised, triangular rostrum, and zooid showing signs of intramural budding (arrowed). F. Putative kenozooids. G. Group of zooids, vicarious avicularia and putative kenozooid with reduced opesia (asterisk). H. Group of zooids and vicarious avicularia, one zooid irregularly shaped and with reversed polarity (asterisk). Scale bars: A = 1 mm; B–D, F–H = 500 µm; E = 400 µm.