Rhebasia Jullien, 1882

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 : 1700-1701

Genus Rhebasia Jullien, 1882

( Figure 27 )

Type species

Eschara dorilas d’ Orbigny, 1851 [not Eschara doris d’ Orbigny, 1851, cf. Bassler 1953; Prud’ homme 1968], by subsequent designation ( Canu and Bassler 1927, p. 37). Cretaceous, Senonian [?Santonian], Vendôme, Loir-et-Cher, France.

Diagnosis

Colony erect, vincularian ( Figure 27 (a)), dichotomously branching. Autozooids subhexagonal, rounded laterally; zooidal boundaries raised. Cryptocyst extensive, sunken, granular. Gymnocyst lacking. Opesia terminal, occupying about half frontal surface, longitudinally elliptical, the proximal edge straighter, lacking opesiular indentations and lateral constrictions. Ovicells unknown. Avicularia vicarious, large ( Figure 27 (c)), larger than an autozooid; opesia longitudinally elliptical; rostrum broad, gothic arch shaped, pustulose distolaterally.

Remarks

Four Cretaceous species described by d’ Orbigny (1851–1854) were assigned to Rhebasia by Jullien (1882) when introducing the genus. Canu and Bassler (1927, p. 37) chose Eschara dorilas from these as the type species. Jullien (1882) characterised his genus by the elliptical opesiae of the autozooids and the presence of avicularia that are usually larger in size than the autozooids. Of the four species placed in this genus by Jullien (1882), avicularia were figured by d’ Orbigny only in the type species and Vincularia disparilis d’ Orbigny, 1852 , in which they are about the same size as the autozooids but similar in morphology to those of the type species, supporting placement of this species in Rhebasia .

Both Rhebasia and Ogiva were proposed by Jullien (1882) in the same publication. The differences between these two genera are slight, and the greater usage of Ogiva favours retention of this genus over its subjective synonym Rhebasia .

Range

Late Cretaceous.

Figures

Figure 27. Rhebasia dorilas (d’Orbigny); syntype, MNHN R61513; Cretaceous, Senonian [?Santonian], Vendôme, Loir-et-Cher, France; (a) branch; (b) autozooids and an avicularium; (c) avicularium. Scale bars: a = 1 mm; b, c = 200 µm.