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A new type of colony in Silurian (upper Wenlock) retiolitid graptolite Spinograptus from Poland

100%

Kozlowska A., Dobrowolska K., Bates D. E. B.

Acta Palaeontologica Polonica

2013

tom 58

nr 1

The new retiolitid species, Spinograptus tubothecalis, is described from the Colonograptus praedeubeli and C. deubeli biozones from two localities in Poland: a borehole on the East European Platform and the Holy Cross Mountains. This was a recovery phase after the severe Silurian Cyrtograptus lundgreni Event. The new species has a unique, previously undescribed form of finite rhabdosome. Unlike the species Spinograptus reticulolawsoni and S. lawsoni, in which the fi− nite rhabdosomes taper distally, its rhabdosome is parallel−sided with the two distal thecae developed as isolated tubes without genicular processes, with a small appendix between them. The new species also has preserved membranes of the sicula, thecae and ancora sleeve, similar to a few species of Spinograptus from the lower Homerian. Spinograptus tubothecalis, like Spinograptus clathrospinosus and S. spinosus, has paired reticulofusellar genicular processes on the pre−thecal ventral orifices, similar to but shorter than thecal processes. Transverse rods, a rare character in post−Cyrto− graptus lundgreni Event retiolitids occur in the new species in rudimentary form.

Retiolitid graptolite Spinograptus from Poland and its membrane structures

100%

Kozlowska-Dawidziuk A.

Acta Palaeontologica Polonica

1997

tom 42

nr 3

391-412

Spinograptus reticulolawsoni sp. n., S. latespinosus sp. n., S. cf. latespinosus, and S. sp. are described from borecore samples of the late Wenlock (Colonograptus? praedeubeli Zone), of the Bartoszyce borehole, NE Poland. They represent an early diversification phase of retiolitids, which followed the Cyrtograptus lundgreni Event. Some species display a combination of primitive and advanced characters, implying a mosaic paffern of Spinograptus evolution. Most of the material studied contains continuous peridermal membranes, suggesting that they may have been universally present in the retiolitids. Long (2 mm) siculae found in two species of Spinograplus contrast with short siculae, known for Retiolites and Paraplectograptus.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Bates D. E. B.

1 Dobrowolska K.

1 Kozlowska A.

1 Kozlowska-Dawidziuk A.

1 2013

1 1997

Wyniki wyszukiwania

A new type of colony in Silurian (upper Wenlock) retiolitid graptolite Spinograptus from Poland

Retiolitid graptolite Spinograptus from Poland and its membrane structures