Holsacella Voigt, 1999

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 : 1681-1682

Genus Holsacella Voigt, 1999

( Figure 13 )

Type species

Holsacella biserialis, 1999 , by original designation. Paleocene, Danian-aged glacial drift, Daerstorf, Niedersachsen, Germany .

Diagnosis

Colony erect, biserial unifoliate with zooids opening on one side of the branch only ( Figure 13 (a)). Autozooids hexagonal; zooidal boundaries grooved. Cryptocyst extensive, granular. Gymnocyst lacking. Opesia terminal, occupying less than one-third of frontal surface; rounded square, proximal and distal edges slightly convex, sides straight, lacking opesiular indentations and constrictions ( Figure 13 (b)). Ovicells unknown. Avicularia interzooidal, symmetrical, small, about half the width of an autozooid and shorter in length, located on edges of branch distolaterally of the autozooids, one per autozooid ( Figure 13 (b,c)); opesia terminal, longitudinally elliptical; rostrum very short.

Remarks

When introducing this monospecific genus, Voigt (1999) declined to assign it to a family but the extensive frontal wall that is entirely cryptocystal, combined with the lack of opesiules, allows its provisional assignment to Onychocellidae . Holsacella may be unique among onychocellid genera in having narrow erect branches with zooids opening only on one side, a colony form sometimes termed unifoliate.

Range

Paleocene (Danian).

Figures

Figure 13. Holsacella biserialis Voigt; holotype, SMF 26223; glacial drift of Paleocene (Danian) age, Daerstorf, Lower Saxony, Germany; (a) Frontal side of branch; (b) Autozooid and avicularium on right-hand branch edge; (c) Autozooids and avicularia. Scale bars = 200 µm.