| Abstract Detail
Paleobotanical Section Kvacek, Jiri [1]. Tritaenia linkii - conifer or ginkgophyte? The narrow leaves of Tritaenia linkii have attracted and puzzled palaeobotanists for a long time. It was originally described as a conifer, subsequently reinterpreted as a ginkgophyte, later classified back as a conifer again. Studies based on sterile foliage probably cannot resolve this issue. Due to this, bulk maceration of a large amount of material was performed. Coal claystone full of leaves and other organic material forming monodominated taphocoenoses provided a number of associated organs: besides leaves, there were shoots, ovuliferous structures, possible male structures and pollen. Based on the monodomination, it is assumed that all the material comes from one fossil plant. Tritaenia linkii (Roemer) Maegdefrau et Rudolf - leaves with resin bodies are very variable in length, and in number of veins per leaf. The leaves are hypostomatic, with very thick cuticle, bearing stomata in two to five stomatal bands; external surface shows papillae, forming star-like structures. Sulcatocladus robustus Watson et Harrison - shoots always associated with leaves T. linkii in the Wealden of Germany and England. The shoots are covered with helically arranged leaf bases, each subtending one or two types of scars. Ovuliferous organs representing ovate seeds of Allicospermum type are born on simple pedicelate collars. Seeds consisting of two membranes are interpreted here as sarcotesta and sclerotesta. Seeds are filled with numerous resin bodies forming large bulging structures, sometimes prominent on the seed surface. Possible male reproductive structures form strobili, consisting of helically arranged bracts subtending microsporangiophores containing monosulcate pollen of Cycadopites type. The pollen is smooth, broadly elongate, monocolpate 30 x 40 µm of Cycadopites type Ovuliferous organs associated with Tritaenia linkii resemble the organs described as female reproductive structures of Cretaceous Ginkgoales, Nehvizdyella J. KvaÄek et al. from the Cenomanian of the Czech Republic, and collars of the genus Nagrenia Nosova from the Jurassic of Uzbekistan. The only difference between Nehvizdyella, Nagrenia and the studied organ is that both of the earlier published organs have bifurcated pedicles, while the studied organ is attached singly. However, the same construction of seeds (Allicospermum type) and characteristic collar clearly argue for ginkgoalean origin of the structure. Monosulcate associated pollen of Cycadopites type, as well as that found in situ underpins this assumption. Coniferous origin of the Tritaenia plant is supported only by presence of needle-like leaves similar to Sciadopitys, and shoots covered by large persistent leaf bases.
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1 - National Museum, Vaclavske nam, Praha, 115 79, Czech Republic
Keywords:
Ginkgoales
ovuliferous organ
microsporangiateorgan
Wealden.
Presentation Type: Oral Paper:Papers for Sections
Session: 24
Location: Salon 5/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 4:30 PM
Number: 24004
Abstract ID:999
Candidate for Awards:None |
