Dictuonia 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 : 1672-1673

Genus Dictuonia Jullien, 1882

( Figure 7 )

Type species

Eschara aceste d’ Orbigny, 1851 , by subsequent designation. Late Cretaceous, France. Jullien (1882) listed nine Cretaceous species, all named by d’ Orbigny, in his new genus Dictuonia but did not chose a type species. This appears to have been left to Bassler (1935, p. 93). Unfortunately, d’ Orbigny’ s type material of Dictuonia aceste is missing ( Gordon and Taylor 2005, table 2). According to Prud’ Homme (1968, p. 216), D. aceste is synonymous with Eschara danae d’ Orbigny, 1851 , the type material of which is in existence and which is one of the nine species listed by Jullien (1882) in Dictuonia . Therefore, the diagnosis of Dictuonia given below is based on the type material of Dictuonia danae (d’ Orbigny, 1851) from the ‘Senonian’ of Tours, Indre-et-Loire, France.

Diagnosis

Colony erect, bifoliate, branches palmate (‘adeoniform’) ( Figure 7 (a,e)). Autozooids hexagonal or diamond shaped; zooidal boundaries raised ( Figure 7 (b)). Cryptocyst extensive, depressed. Gymnocyst lacking. Opesia subterminal, occupying about half of the frontal surface; subcircular or longitudinally elliptical, lacking opesiular indentations and lateral constrictions. Ovicells unknown. Avicularia vicarious, asymmetrical ( Figure 7 (c)), about half the width of an autozooid; opesia longitudinally elliptical; rostrum acutely triangular, floor smooth, deep.

Remarks

Like Collura , the genus Dictuonia has been neglected. Notwithstanding the loss of d’ Orbigny’ s type material of the type species, based on the characters of the putative synonym D. danae there is utility in resurrecting the genus for onychocellids with rounded autozooidal opesiae that contrast with those of other onychocellids – such as Onychocella , Aechmella and Smittipora – in which the opesiae have a distinct proximal edge that is straight or gently curved.

Range

Late Cretaceous.

Figures

Figure 7. Dictuonia danae (d’Orbigny); Syntypes, MNHN R61520; Late Cretaceous, ‘Senonian’, Tours, Indre-et-Loire, France. (a) Bifoliate branch; (b) autozooids; (c) avicularium. (d) autozooids from another branch; (e) overall view of the same branch. Scale bars: a, e = 1 mm; b, c = 200 µm; d = 500 µm.