Rhynchozoon krouzkovensis, ZÁGORŠEK, 2010

ZÁGORŠEK, KAMIL, 2010, BRYOZOA FROM THE LANGHIAN (MIOCENE) OF THE CZECH REPUBLIC PART II: SYSTEMATIC DESCRIPTION OF THE SUBORDER ASCOPHORA LEVINSEN, 1909 AND PALEOECOLOGICAL RECONSTRUCTION OF THE STUDIED PALEOENVIRONMENT, Acta Musei Nationalis Pragae Series B 66 (3 - 4), pp. 139-255 : 139-255

Rhynchozoon krouzkovensis sp. n.

Pl. 141, Fig. 3-4

D i a g n o s i s: Autozooecia oval to hexagonal, with very large marginal areolar pores. Aperture semilunar to oval. Peristomes short forming an asymmetrical pseudo-spiramen. Small but prominent umbo situated on the proximal margin of the peristome. Suboral avicularia small, drop-like. Oral spines present, 2-4 on distal margin. Adventitious avicularia absent. Ovicell unknown.

H o l o t y p e: The specimen illustrated in Pl. 141, Fig. 4, from the section Rousínov – Kroužek, deposited in the National Museum Prague under the number PM2 – P 01810.

P a r a t y p e s: Specimen from the section Rousínov – Kroužek, deposited in the National Museum Prague under the number PM2 – P 01809.

D e r i v a t i o n o m i n i s: Due to the occurrence in the section at Rousínov – Kroužek.

L o c u s t y p i c u s: Kroužek, sample Kr-3.

S t r a t u m t y p i c u m: Langhian – Lower Badenian.

M e a s u r e m e n t s: (in micro meters = µm; x = = average):

length of autozooecia: 282-388; x = 318

width of autozooecia: 152-260; x = 211

length of autozooecial aperture: 58-80; x = 69

width of autozooecial aperture: 92-116; x = 108

diameter of avicularium chamber: 54-88; x = 74

diameter of marginal areolar pore: 20-34; x = 27

D e s c r i p t i o n: Autozooecia oval to hexagonal, with a flat, smooth frontal wall, separated by very narrow grooves. Marginal areolar pores very large but rare, only 2- 4 pores on the border of each autozooecium, arranged chaotically. Apertures semilunar to oval with dentition on the distal margin. Peristomes short forming an asymmetrical pseudo-spiramen. Small but prominent umbo situated on the proximal margin of the peristome, opposite to the pseudo-spiramen. Suboral avicularia small, drop-like without a pivotal bar. Oral spines sometimes developed, 2-4 on the distal margin. Adventitious avicularia absent. Ovicell unknown.

C o m p a r i s o n: This species differs from Rhynchozoon monoceros ( REUSS, 1847) in having a much smaller umbo with a suboral avicularium and asymmetrical pseudo-spiramen. Rhynchozoon oslavanensis sp. n. differs in having much deeper grooves and by the peristomes which do not form a pseudo-spiramen.

Rhynchozoon krouzkovensis sp. n. differs from any other Rhynchozoon species in having very large and rare areolar pores, shorter peristomes forming an asymmetrical pseudo-spiramen and by its small avicularia.