Pyrgopolon (Septenaria) cf. tricostata (GOLDFUSS, 1841)

Kočí, Tomáš & Jäger, Manfred, 2015, Sabellid And Serpulid Worms (Polychaeta, Canalipalpata, Sabellida, Sabellidae, Serpulidae) From The Rocky Coast Facies (Late Cenomanian) At Předboj Near Prague, Acta Musei Nationalis Pragae Series B 71 (1 - 2), pp. 31-50 : 38

Pyrgopolon (Septenaria) cf. tricostata (GOLDFUSS, 1841)

Pl. 2, Fig. 8–9; Pl. 4, Fig. 2

1910 Burtinella (?) Reussi m. – Weinzettl, p. 23–24, pl. 3, fig. 48, 50. (NM-O3536)

non 1910 Burtinella (?) Reussi m. – Weinzettl, p. 23–24, pl. 3, fig. 46–47, 49, and 51.

1984 Ditrupa tricostata (GOLDFUSS), 1841 – Ziegler, p. 239, pl. 6, fig. 8–9. (NM-O5394–5395)

2009a Pyrgopolon cf. tricostata (GOLDFUSS) – Kočí, p. 98–100, fig. 5–6.

2010 Pyrgopolon (Septenaria) cf. tricostata (GOLDFUSS) – Kočí, p. 124–125, fig. 5–6.

2012a Pyrgopolon (Septenaria) cf. tricostata (GOLDFUSS) – Kočí, p. 10–11, pl. 1, fig. 4a–b.

2012c Pyrgopolon (Septenaria) cf. tricostata (GOLDFUSS, 1831) – Kočí, p. 126, fig. 1I–L.

M a t e r i a l: At least four specimens. Two incomplete specimens representing the anterior tube portion with the aperture preserved, one of them with remains of the transitional area between the attached and the free portion.

S u b s t r a t e: Not preserved. One of the tubes is infested by the symbiont Protulophila gestroi ROVERETO, 1901 .

D e s c r i p t i o n. A medium-sized Pyrgopolon . The free tube portion is straight and measures 2.9 mm, respectively 3.4 mm in diameter which stays nearly constant throughout the whole free tube portion. The upper side of the tube bears three strong straight keels of which the median keel is the strongest and highest. In the lower left and right there are two more keels but these are wide and very rounded, in cross-section appearing like lobes. Faint incremental lines protrude slightly on the median keel and cause this keel to protrude a little over the aperture. Apart from the keels and the faint incremental lines, the tube’s surface appears to be relatively smooth. The lumen is circular. The colour is usually brownish.

R e m a r k s a n d r e l a t i o n s h i p s. The tubes from Předboj differ considerably from Pyrgopolon (P. or Triditrupa ) tricostata sensu stricto from the Middle Cenomanian of Essen in which the tube diameter increases rapidly in size, it has three wide rounded keels situated at almost equal distances from each other all around the tube, and its circular inner tube wall is visible from the posterior tube fracture. This latter factor is typical for nearly all subgenera of the genus Pyrgopolon except for the subgenus Pyrgopolon (Septenaria) REGENHARDT, 1961 , see Jäger (2005). Thus, the tubes from Předboj may even belong to a different subgenus than tricostata sensu stricto.

Moreover, the tubes from Předboj also differ from tubes from Saxony described by Jäger (2014) as “ Pyrgopolon (Septenaria) sp. aff. tricostata ” in which the keels, in spite of considerable variation, are more similar to those of tricostata sensu stricto.

Within the BCB, except for its Saxon portion, the tubes from Předboj represent a similar fauna as the tubes described by Kočí (2009a, b, 2010, 2012a) from other rocky coast facies localities (Kaňk, Velim, Nová Ves near Kolín, Chrtníky, Kamajka) which display a wider range of tube diameters. For a more detailed discussion see Kočí (2012a).

The two specimens described and figured by Ziegler (1984) as “ Ditrupa tricostata (GOLDFUSS), 1841 ” may, in spite of some morphological differences, represent the same species as the Předboj tubes. One of these specimens (NM-O5394) possesses a “ Favosites structure” at the transition from the attached to the free tube portion; as a consequence at least this specimen belongs to the subgenus Pyrgopolon (Septenaria) . Moreover, in the collection of Ziegler’s original specimens kept in the National Museum in Prague, there is another but unfigured specimen of P. cf. tricostata labelled with inventory number NM-O5363 instead of the missing “ Ditrupa subtorquata ” specimen with the same registration number figured by Ziegler (1984, pl. 6, fig. 7).