Rhagasostoma (Bryozoa) from the Late Cretaceous of Eurasia: taxonomic revision, stratigraphy and palaeobiogeography Author Koromyslova, Anna V. 852422E7-8592-4209-AE5F-AD0554D11E7D Borissiak Paleontological Institute of the Russian Academy of Science, Profsoyuznaya st. 123, Moscow, 117997, Russian Federation. Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW 7 5 BD, UK. Senckenberg Forschungsinstitute und Naturmuseun, Sektion Marine Evertebraten III (Bryozoologie), Senckenberganlage 25, 60325 Frankfurt am Main, Germany. The Sedgwick Museum of Earth Sciences, Department of Earth Sciences, University of Cambridge, UK. koromyslova.anna@mail.ru Author Taylor, Paul D. 7AFF2929-DF5B-46B2-94E6-B26B396CC2C8 p.taylor@nhm.ac.uk Author Martha, Silviu O. C926B3E7-2C56-450E-9C81-B00793465CE0 silviu.martha@senckenberg.de Author Riley, Matthew 8E9D3DB4-6D14-4895-AD34-77C51022DA05 mlr44@cam.ac.uk text European Journal of Taxonomy 2018 2018-12-26 490 1 66 journal article 22081 10.5852/ejt.2018.490 52356089-4633-4477-99c9-45f18606f5b9 3830845 BE023137-CC5E-4DC5-94F6-B549BB140361 Rhagasostoma tchvanovi ( Favorskaya, 1992 ) Fig. 15 , Table 9 Onychocella tchvanovi Favorskaja, 1992: 126 , pl. 68, figs 6–8. ? Rhagasostoma gibbosum var. weybournensis Brydone, 1930: 48 , pl. 26, fig. 12. non Rhagasostoma gibbosum var. weybournensis – Brydone 1930: 48 , pl. 26, figs 13–14. Fig. 15. Rhagasostoma tchvanovi ( Favorskaya, 1992 ) . A–E . Late Campanian ( Cibicidoides voltzianus Zone ; LS15), southern Aral Sea Region, Republic of Karakalpakstan, Uzbekistan. A–C . Holotype, TsNIGR Museum 33/12582. A . Overview of erect bifoliate colony. B . Ovicellate autozooids and avicularia. C . Non-ovicellate autozooids and avicularia. D–E . TsNIGR Museum 34/12582. D . Overview erect bifoliate of colony. E . Non-ovicellate autozooids and avicularia. F . TsNIGR Museum 32/12582, middle Campanian ( Brotzenella monterelensis Zone ; LS14), southern Aral Sea Region, Republic of Karakalpakstan, Uzbekistan; overview of erect bifoliate colony, cryptocyst of autozooids with proximolateral caverns. Scale bars: A = 500 µm; B, E = 200 µm; С = 250 µm; D, F = 1 mm. Table 9. Summary of measurements of Rhagasostoma tchvanovi ( Favorskaya, 1992 ) . For each parameter the range is given with the number of measurements in brackets. The arithmetic mean is given ± standard deviation. All measurements in µm.

Basin Stratigraphy Locality		North Ust-Yurt–Aral Basin Early to middle late Campanian Southern Aral Sea Region
AzL	340–550 (18) 418.89 ± 50.98
AzW	230–360 (18) 264.44 ± 22.29
Autozooids	CvL OpL OpW	70–100 (4) 80 ± 14.14 110–140 (14) 127.86 ± 9.75 110–140 (14) 120.00 ± 2.96
OoL	140–230 (5) 198.00 ± 35.64
OoW	180–230 (5) 210.00 ± 18.71
AvL	290–530 (11) 381.82 ± 71.25
RL	160–350 (11) 254.55 ± 58.20
Avicularia	RW PrL PrW	80–120 (11) 93.64 ± 13.62 110–190 (10) 137.00 ± 25.84 70–120 (11) 94.55 ± 17.53
OpL	70–100 (8) 77.50 ± 10.35
OpW	30–70 (8) 53.75 ± 11.88

Material studied Holotype UZBEKISTAN • Republic of Karakalpakstan ; late Campanian ( Cibicidoides voltzianus Zone ; LS 15) of the southern Aral Sea Region ; TsNIGR Museum 33/12582 ( Fig. 15 A–C; figured by Favorskaya 1992 : pl. 68, fig. 6). Additional figured material UZBEKISTAN • Same data as for holotype; TsNIGR Museum 34/12582 ( Fig. 15 D–E; figured by Favorskaya 1992 : pl. 68, fig. 7) • Republic of Karakalpakstan ; middle Campanian ( Brotzenella monterelensis Zone ; LS14) of the southern Aral Sea Region ; TsNIGR Museum 32/12582 ( Fig. 15F ) . Description Colony erect with flattened bifoliate branches ( 3–4 mm wide). Ancestrula and early astogeny not observed. Autozooids variable in shape, often broad and subrectangular with rounded distal ends; zooidal boundaries raised. Gymnocyst lacking. Cryptocyst extensive, finely pustulose, slightly depressed centrally, sometimes with proximolateral peripheral caverns ( Fig. 15F ). Opesia terminal, semielliptical, formed by two walls, a thin inner wall forms the distolateral part of the opesia, and a projecting thickened outer wall forms the proximolateral part ( Fig. 15C, E ). Proximal edge of opesia straight, smooth, with outgrowths at the two proximolateral corners which delineate small opesiules; outgrowths often destroyed giving the opesiules the appearance of opesiular indentations. Septula not observed. Ovicells endozooidal, ooecium is formed by the distal zooid, well-recognizable, with cryptocyst-like surface and arch-like proximal edge with elongated proximolateral processes extending along the cryptocyst of the maternal zooid ( Fig. 15 A–B). Avicularia interzooidal, smaller than autozooids, elongate. Rostrum channeled with elevated wing-like walls and pointed tip, narrow, almost straight, asymmetrical, dextral or sinistral. Top of rostrum reaches opesia of distal autozooid. Wedge-like structures not observed. Proximal part rounded, shorter and wider than rostrum, cryptocyst pustulose, concave. Opesia round with short slit proximally, opesiules lacking ( Fig. 15C ). Closure plates, kenozooids, intramural reparative budding of autozooids and avicularia not observed. Remarks Rhagasostoma tchvanovi differs from the closely related species R. gibbosum in the avicularian rostrum being long and almost straight instead of short and tilted to the right or left. The specimen described by Brydone (1930 : pl. 26, fig. 12) as Onychocella gibbosum weybournensis differs from R. gibbosum ( Marsson, 1887 ) in having a long and straight avicularian rostrum and is conspecific with R. tchvanovi . Specimen 32/ 12582 in the collections of the TsNIGR Museum and labelled as “ O. subgibbosum Brydone, 1930 ” is not the one that was depicted by Favorskaya (1992 : pl. 67, fig. 3) and belongs to R. tchvanovi . Distribution Middle to late Campanian Republic of Karakalpakstan, Uzbekistan : six localities between Chimboy/ Shımbay (Чимбой/Шымбай) and the Aral Sea.