Rhagasostoma, Koschinsky, 1885

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, European Journal of Taxonomy 490, pp. 1-66 : 56-57

Key to species of Rhagasostoma described in this paper

1. Avicularia interzooidal, peripheral caverns usually present ............................................................. 2 – Avicularia vicarious, ovicells immersed, peripheral caverns lacking ............................................... 3

2. Avicularia longer than autozooids, ovicells endozooidal or immersed ............................................ 4 – Avicularia about ½ the autozooid size or less, ovicells endozooidal ................................................ 5

3. Opesia of autozooids with opesiular indentations ..................................... R. rowei ( Brydone, 1906) – Opesia of autozooids with opesiules ...................................................... R. mimosa ( Brydone, 1930)

4. Avicularian rostrum conical in outline, ovicells endozooidal ........................................................... 6 – Avicularian rostrum spade-shaped, ovicells immersed or not observed ........................................... 7 – Avicularian rostrum falciform, ovicells endozooidal ....................................................................... 8

5. Avicularian rostrum short and tilted to the right or left, gymnocyst present .................................... 9 – Avicularian rostrum long and straight, gymnocyst lacking ............ R. tchvanovi ( Favorskaya, 1992)

6. Avicularian rostrum asymmetrical .................................................................................................. 10 – Avicularian rostrum symmetrical .....................................................................................................11

7. Avicularian rostrum narrowed at the base, enlarged centrally and ended with top, ovicells immersed ............................................................................................................. R. brydonei sp. nov.

– Avicularian rostrum almost the same width along the whole of its length and with pointed or rounded top, ovicells not observed ............................................................................. R. operculatum sp. nov.

8. Avicularian rostrum with one side of rostrum almost straight and other side curved near top .......... .................................................................................................................. R. minuens Brydone, 1936

9. Autozooidal cryptocyst with slightly convex border; gymnocyst very rarely observed .................... ............................................................................................................. R. gibbosum ( Marsson, 1887)

– Autozooidal cryptocyst with convex border; gymnocyst well developed .......................................... ............................................................................................................. R. gibbosulum Brydone, 1936

10. Avicularian opesia large, roundish or oval with thickened distolateral edge and with thin articular ridges bearing two short teeth proximally and a short or long, slit-like opesiular indentation between the teeth; opesiules lacking ................................................................. R. inelegans ( Lonsdale, 1850)

– Avicularian opesia distal, small, subcircular; two lateral parallel slit-like opesiules formed by long teeth of articular ridges and a long, slit-like opesiular indentation between the teeth proximally below opesia .............................................................................................. R. angliae Brydone, 1936

11. Avicularian opesia egg-shaped, with thin articular ridges bearing two short teeth proximally and a short or long slit-like opesiular indentation between the teeth; opesiules lacking ............................. ............................................................................................................................. R. aralense sp. nov.