Collura 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 : 1671-1672

Genus Collura Jullien, 1882

( Figure 6 )

Type species

Eschara athulia d’ Orbigny, 1851 , by subsequent designation. Cretaceous, Senonian [probably Maastrichtian], Néhou, Manche, Normandy, France . Jullien (1882) listed three species

under Collura but failed to choose a type species. The first of these three species was stated by Bassler (1935, p. 77) to be the type species, which may represent the first designation.

Diagnosis

Colony erect, vincularian ( Figure 6 (a)). Autozooids subhexagonal to diamond shaped; zooidal boundaries broadly grooved due to voids in calcification around the proximal cryptocyst ( Figure 6 (b)), the remaining cryptocyst having an inverted teardrop shape. Opesiae terminal, occupying about half of the frontal surface, longitudinally ovoidal, lacking opesiular indentations or lateral constrictions. Ovicells and avicularia unknown.

Remarks

Prud’ Homme (1968, p. 214, pl. 1, fig. 3) doubted the validity of this genus, commenting that d’ Orbigny’ s type material of the type species was ‘represented by a fragment of colony in which the particular form of the zooids appears to result from an alteration identical to that which often affects colonies of Eschara [ Onychocella ] royana, among others’. She appears to have been referring to the voids in the cryptocyst, to judge from subsequent scanning electron microscopy of this material ( Figure 6 ). The genus Collura has fallen into disuse, although it was listed as a valid genus of Onychocellidae by Gordon and Taylor (2005, table 2). The absence of avicularia in the type material, combined with the lack of conspecific colonies that might have these polymorphs, hampers a clear definition of the genus.

Range

Late Cretaceous [?Maastrichtian].

Figures

Figure 6. Collura athulia (d’Orbigny); lectotype, MNHN R61508; Cretaceous, Senonian (probably Maastrichtian), Néhou, Manche, Normandy, France. (a) Branch fragment; (b) autozooids with grooves around perimeter of the opesiae. Scale bars: a = 500 µm; b = 200 µm.