Rhagasostoma brydonei Koromyslova & Taylor & Martha & Riley 2018, sp. nov.
Creators: name: Koromyslova, Anna V.
name: Taylor, Paul D.
name: Martha, Silviu O.
name: Riley, Matthew
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Bryozoa
Gymnolaemata
Cheilostomatida
Onychocellidae
Rhagasostoma
Rhagasostoma brydonei

description: Rhagasostoma brydonei sp. nov.
urn:lsid:zoobank.org:act: B229DB57-799E-494C-95EF-7F117080B3E9
Fig. 5, Table 2
Rhagasostoma inelegans (Lonsdale, 1850) – Brydone 1930 pars: 47, pl. 25, figs 11–12.
non Rhagasostoma inelegans – Brydone 1930 pars: 47, pl. 26, figs 1–3.
Diagnosis
Colony erect, bifoliate. Autozooids rectangular, zooidal boundaries raised; gymnocyst lacking; cryptocyst extensive with peripheral caverns; opesia terminal, rarely subterminal, semielliptical with shelf in the distal part, proximal edge with small roundish opesiules; ovicells immersed, ooecia vestigial. Avicularia interzooidal, longer than autozooids; rostrum channeled with pointed tip, spade-shaped, symmetrical or asymmetrical; proximal part rounded, shorter and wider than rostrum; opesia oval or roundish with thickened articular ridges bearing two very short teeth proximally and a long, slit-like opesiular indentation between the teeth; opesiules lacking. Kenozooids rare, rounded or oval.
Etymology
In honour of Reginald Marr Brydone (1873 – 1943), a prolific author of bryozoan species from the English Chalk and collector of the type material of the new species.
Material studied
Holotype
UNITED KINGDOM • England, Hampshire, south of Alton, Froxfield, Kings Lane; latest Turonian (Sternotaxis plana Zone); SM B36666 (Fig. 5 A–B; figured by Brydone 1930: pl. 25, figs 11–12).
Paratypes
UNITED KINGDOM • Same data as for holotype; SM B36667 (Fig. 5 C–D) • 3 specs; England, Kent; Coniacian of Chatham; SMF 29939 (Fig. 5 F), 29940 (Fig. 5 E), 29941 (Fig. 5 G–H).
Type locality and horizon
United Kingdom, England, Hampshire, south of Alton, Froxfield, Kings Lane; Sternotaxis plana Zone, late Turonian.
Description
Colony usually erect, with flattened bifoliate branches, fragments 3.5–6.0 mm long by 2.0– 6.5 mm wide. Ancestrula and early astogeny not observed. Autozooids variable in shape, often broad and roughly rectangular with rounded distal ends; zooidal boundaries raised. Gymnocyst lacking. Cryptocyst extensive, finely pustulose, depressed or slightly convex centrally, with peripheral caverns surrounding the cryptocyst (Fig. 5B, D, F–H) or rarely developed in proximal or proximolateral part of cryptocyst (Fig. 5E). Opesia terminal, rarely subterminal, semielliptical, with shelf in the distal part, formed by two walls, a thin inner wall delimiting the distolateral part and a salient, thickened outer wall delimiting the proximolateral part (Fig. 5H). Proximal edge of opesia straight, smooth, thickened, with outgrowths near the two proximolateral corners delimiting small, roundish opesiules (outgrowths are often broken thus giving the opesiules the appearance of opesiular indentations or they may be obscured by sediment infills of the opesia). Septula not observed. Ovicells immersed, ooecium formed by the distal zooid, vestigial, vizor-like, brooding
cavity located in the distal part of the maternal zooid and below the colony surface (Fig. 5H). Avicularia interzooidal, elongate, longer than autozooids. Rostrum channelled, with elevated wing-like walls and pointed tip, spade-shaped, symmetrical or asymmetrical, dextral or sinistral. Proximal part rounded, shorter and wider than rostrum. Cryptocyst pustulose, concave, peripheral caverns rare. Opesia large, usually oval, rarely roundish, with thickened articular ridges bearing two very short teeth proximally and a long, slit-like opesiular indentation between teeth; opesiules lacking. Kenozooids rounded or oval, located usually at edges of colony (Fig. 5B). Cryptocyst finely pustulose with proximal peripheral caverns. Opesia roundish, small. Closure plates, intramural reparative budding of zooids not observed.
Remarks
We have restudied Brydone’s examples of Rhagasostoma inelegans in the SM collection. The specimen identified by Brydone as this species (Brydone 1930: pl. 25, figs 11, 12) does not belong to Lonsdale’s species and is here regarded as a new species, R. brydonei sp. nov.
The new species differs from the closely related species Rhagasostoma inelegans, R. minuens, R. angliae and R. aralense sp. nov. in the avicularian rostrum being spade-shaped rather than having a conical outline shape or falciform. Moreover, the ovicells of R. brydonei sp. nov. are immersed. Rhagasostoma brydonei sp. nov. differs from R. angliae in having an avicularian cryptocyst with large oval or roundish opesia lacking opesiules, instead of a small subcircular opesia and two opesiules. The new species differs from R. operculatum sp. nov., which has a similar spade-shaped avicularian rostrum, by the rostrum being narrowed at the base, enlarged centrally and with a pointed tip, instead of being the same width along almost its entire length and having a pointed or rounded tip.
Distribution
Late Turonian United Kingdom: Kings Lane, Froxfield, south of Alton, Hampshire, England. Coniacian United Kingdom: Chatham, Kent, England.
description: Published as part of Koromyslova, Anna V., Taylor, Paul D., Martha, Silviu O. & Riley, Matthew, 2018, Rhagasostoma (Bryozoa) from the Late Cretaceous of Eurasia: taxonomic revision, stratigraphy and palaeobiogeography, pp. 1-66 in European Journal of Taxonomy 490 on pages 13-16, DOI: 10.5852/ejt.2018.490, http://zenodo.org/record/3830845