Tyloporella Voigt, 1989

Taylor, Paul D., Martha, Silviu O. & Gordon, Dennis P., 2018, Synopsis of ‘ onychocellid’ cheilostome bryozoan genera, Journal of Natural History (J. Nat. Hist.) 52 (25 - 26), pp. 1657-1721 : 1706-1708

Genus Tyloporella Voigt, 1989

( Figure 33 )

Type species

Tyloporella reussi Voigt, 1989 , by original designation. Cretaceous, late Cenomanian ( Actinocamax plenus ammonite Zone), Hoher Stein quarry, Dresden-Plauen, Saxony, Germany .

Diagnosis

Colony encrusting, unilamellar ( Figure 33 (a,b)). Autozooids pyriform to subhexagonal ( Figure 33 (c,d)); zooidal boundaries grooved. Cryptocyst extensive, granular. Gymnocyst, when visible, narrow, surrounding cryptocyst proximally and proximolaterally. Opesia terminal, occupying about one-third of the frontal surface, semielliptical; two or three pairs of minute oral spine bases in a few autozooids; closure plates often bearing impressions of opercular occlusor muscles present in some zooids ( Figure 33 (c,d)). Ovicells hyperstomial ( Figure 33 (a)). Avicularia interzooidal, small, irregularly interspersed among autozooids ( Figure 33 (a,c)), located distally or laterodistally of autozooidal opesiae.

Remarks

Voigt (1989, p. 59) introduced the genus Tyloporella for a new species – Tyloporella reussi – that had been misidentified by Reuss (1872) as ‘ Membranipora tenuisulca ’ ( Reuss, 1846) , the latter being a possible candidate for assignment to Aechmellina gen. nov. The name alludes to similarities with Tylopora Lang, 1917 , which, however, has pauciserial, ribbon-like encrusting branches. The most recent redescription of T. reussi is by Martha et al. (2017). Apart from the frequent, small avicularia interspersed among the autozooids, a proximal, smooth gymnocyst is characteristic for this genus according to Voigt (1989) and was taken as justification to assign the genus to Calloporidae rather than Onychocellidae by some subsequent taxonomists (e.g. Taylor and McKinney 2006). A gymnocyst is visible only in some better preserved specimens from the type locality, but not in the holotype, which is poorly preserved. Possible minute spine bases were observed in few autozooids of the holotype colony ( Voigt 1989, p. 8, fig. 4), while other, better preserved, colonies show no evidence for spine bases (see Martha et al. 2017).

The North American Maastrichtian species Tyloporella cretacea ( Canu and Bassler, 1926) has opesiae that occupy about half of the zooidal frontal surface and ovicells with a smooth gymnocystal ooecium ( Taylor and McKinney 2006). A third species, Tyloporella smithi Di Martino and Taylor, 2013 , from the Campanian of the United Arab Emirates, is bifoliate and can only be placed in this genus with some reservation, as is true for the specimen of Amphiblestrum elegans ( von Hagenow, 1851) figured from the Danian of Denmark by Berthelsen ( Berthelsen 1962, p. 9, fig. 3).

Range

Cretaceous (Cenomanian to Maastrichtian),?Paleocene (Danian).

Figures

Figure 33. Tyloporella reussi Voigt. (a,b) Upper Cenomanian (Actinocamax plenus zone), Hoher Stein Quarry in Dresden-Plauen, Saxony, Germany; (a) holotype, MMG SaK 1617; part of colony with two broken ovicells indicated by arrows. (b) MMG SaK 15777a; autozooids and avicularia at growing edge. (c) NMP, Novak Collection (figured Novak 1877, pl. 1, fig. 19, 20 as Membranipora irregularis (von Hagenow)); Late Cretaceous,?Turonian, Kamajka, Bohemia, Czech Republic; autozooids and avicularia; an autozooid with the opesia covered by a closure plate is arrowed. (d) NHMUK BZ 8221; Cretaceous. Late Cenomanian or early Turonian, Kaňk, Central Bohemian Region, Czech Republic; autozooids (some with closure plates) and avicularia. Scale bars = 500 µm.