Geinitzia reichenbachii (Geinitz, 1842) Hollick and Jeffrey, 1909 and Sedites rabenhorstii Geinitz, 1842 (Pinopsida; Late Cretaceous) reconsidered and redescribed
by Kunzmann L. (2010)
in Review of Palaeobotany and Palynology 159(1-2): 123-140 – DOI10.1016/j.revpalbo.2009.11.006 –
Two conifer species from the Upper Turonian of the Saxonian and North Bohemian parts of the Bohemian Cretaceous Basin are redescribed using the type specimens and additional material from the type horizon. In both cases characters of the gross-morphology of foliage shoots and leaf epidermal cell structure observed by LM and SEM are studied.
Geinitzia reichenbachii is characterized by uniform falcate leaves that spread abruptly from the axis. They are 4-sided in cross section and have slightly decurrent leaf bases and a single central resin canal. The amphistomatic leaves show adaxially two properly developed stomatal bands with densely arranged stomata and abaxially two stomatal bands repeatedly interrupted.
The apertures of the usually incomplete amphicyclic stomatal apparati are randomly orientated relative to the long leaf axis, but oblique and transversal orientation prevails. G. reichenbachii is typified by a neotype and an emended diagnosis is given. Based on detailed comparison to Geinitzia formosa from the Santonian of Quedlinburg, Germany, G. reichenbachii is assigned to Geinitzia Endlicher, 1847 which is considered a natural genus of extinct conifers and type of the Geinitziaceae.
This application becomes legitimate because the conservation of the name Geinitzia has been proposed recently by Zijlstra et al. (2010).
Sedites rabenhorstii is only known from two small specimens representing ultimate shoots. It is proved that it is a fossil conifer completely distinct from G. reichenbachii. S. rabenhorstii shows epidermal cell characters that have been hitherto described from the genus Glenrosa, a putative Cheirolepidiaceae. S. rabenhorstii differs from Glenrosa in leaf phyllotaxis.
The leaves are arranged in four rows, probably in opposite pairs in decussate phyllotaxis. The free leaf part is spreading, straight, triangular in cross section and has an obtuse apex. The leaf base is decurrent. The leaves are amphistomatic with stomata deeply sunken in communal stomatal chambers containing finger-like processes or trichome papillae across the opening.
In conclusion, Sedites is maintained as a morpho-genus for fossil conifers and an emended generic diagnosis is given.