Dorsoserpula bipartita ( REUSS , 1845)

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 : 36

Dorsoserpula bipartita ( REUSS, 1845)

Pl. 1, Fig. 3, 4, 5, 9, 10; Pl. 3, Fig. 2

1845 Serpula bipartita REUSS – Reuss, p. 19, pl. 13, fig. 95a–b.

1875 Serpula Gamigensis GEINITZ – Geinitz, p. 286–287, pl. 63, fig. 19–21.

1984 Sarcinella minor nov. spec. – Ziegler, p. 220–221, pl. 2, fig. 4.

non 1984 Sarcinella minor nov. spec. – Ziegler, p. 220–221, pl. 2, fig. 5.

1984 Martina parva nov. spec. – Ziegler, p. 227–228, pl. 3, fig. 9.

1984 Spirorbis asper (VON HAGENOW), 1840 – Ziegler, p. 242, pl. 7, fig. 6. (NM-O5400)

1984 Spirorbis subrugosus (MÜNSTER), 1831 – Ziegler, p. 244, pl. 8, fig. 2. (NM-O5401)

1984 Spirorbis superminor nov. sp. – Ziegler, p. 244– 245, pl. 8, fig. 3. (NM-O5159)

2005 Dorsoserpula bipartita ( REUSS, 1845) , syn. gamingensis [sic!] (GEINITZ, 1873 [sic!]) – Jäger, p. 162.

2007a Dorsoserpula gamigensis ( GEINITZ, 1875) – Kočí, p. 109–110, fig. 5.

non 2009a Dorsoserpula gamigensis ( GEINITZ, 1875) – Kočí, p. 98, fig. 7.

2009b Dorsoserpula gamigensis (GEINITZ) – Kočí, p. 209, 214, 218–220, fig. 3.

non 2012a Dorsoserpula gamigensis (GEINITZ) – Kočí, p. 10, pl. 1, fig. 6.

2012b Dorsoserpula gamigensis ( GEINITZ, 1875) – Kočí, p. 122, fig. 1C, D.

2012b Dorsoserpula wegneri ( JÄGER, 1983) – Kočí,

p. 122, fig. 1E, I, O. 2012b Cementula sp. – Kočí, p. 120, fig. 1J–K. non 2012b Cementula sp. – Kočí, p. 123, fig. 1L–M.

2014 Dorsoserpula bipartita ( REUSS, 1845) – Jäger,

p. 70, fig. 2g 1–5.

M a t e r i a l: Six complete or nearly complete tubes, one damaged coil, two juvenile tubes and two fragments.

S u b s t r a t e: Two tubes are attached to oyster valves. Two other tubes are attached to dorsal valves of the brachiopod Phaseolina phaseolina (VALENCIENNES in LAMARCK, 1819). Three tubes are attached to, and one of these is coiled around, separate tubes of Placostegus rigidus . Another specimen had originally been attached to an unknown substrate which is no longer present, maybe a crinoid stem or a stem of an alga. A small circular tube, maybe the additional tube characteristic for the genus Dorsoserpula (“Nebenröhre”; see Jäger 1983, p. 39), a juvenile serpulid tube or an overgrown stem of an alga, is laterally attached to the anterior portion of this specimen.

D e s c r i p t i o n. Usually the tube is almost planispirally coiled and consists of two to three whorls. However, a few tubes, especially in the posterior tube portion, are nearly straight or curved or low trochospiral. Tube diameter ranges from 0.9 to 2.5 mm, and coil diameter ranges from 2.7 to 5.5 mm. There is a delicate but sharp and distinct keel which may be slightly undulating on top of the tube, respectively at the periphery of the coil, and some of the larger tubes possess two additional but less distinct lateral keels which start only in the posterior part of the coil, but don’t extend to the aperture of the tube. A smaller specimen has only one lateral keel. Apart from the keels, the surfaces of most tubes appear to be relatively smooth, but under the microscope very delicate, almost indistinct transverse wrinkles are visible. In one specimen, transverse ornamentation is curved forward, similar to the letter “ V ” turned upside down. The cross-section of the tube and the lumen are circular .

R e m a r k s a n d r e l a t i o n s h i p s. Jäger (2005) previously considered D. gamigensis ( GEINITZ, 1875) a junior subjective synonym of D. bipartita , but, however, did not decide if these Late Cenomanian to Early Turonian forms should be synonymized or not with D. wegneri ( JÄGER, 1983) which is wide-spread mainly in the younger portion of the Late Cretaceous. After studying specimens from the BCB, Jäger (2014) concluded that D. bipartita and D. wegneri were two closely related but separate species, differing by size ( D. bipartita remains smaller), by the rarity (but not total absence!) of a keel in subspecies D. wegneri wegneri , whereas D. bipartita usually (but not in every specimen!) has a keel, and by geological age ( D. wegneri wegneri is now considered to exist only from the Middle Turonian onwards). Some specimens from Předboj earlier ( Kočí 2012b) determined as Dorsoserpula wegneri are affiliated to D. bipartita here due to their small size, presence of a keel and relatively old geological age.

After a long gap in geological time, keeled forms became common again in the Maastrichtian and were considered by Jäger (2005) to be a separate subspecies, D. wegneri maastrichtensis JÄGER, 2005 , differing from D. bipartita mainly by possession of cellular tubulae.