Rightcania and Kvacekispermum: Early Cretaceous seeds from eastern North America and Portugal provide further evidence of the early chloranthoid diversification
|Klíčová slova||Canrightia, Canrightiopsis, Chloranthaceae, fossil seeds, mesofossil floras, synchrotron radiation X-ray tomographic microscopy (SRXTM)|
|Citace||FRIIS, Else Marie, CRANE, Peter R. a PEDERSEN, Kaj Raunsgaard. Rightcania and Kvacekispermum: Early Cretaceous seeds from eastern North America and Portugal provide further evidence of the early chloranthoid diversification. Fossil Imprint / Acta Musei Nationalis Pragae, Series B – Historia Naturalis. Prague: National Museum, 2018, 74(1-2), 65-76. DOI: https://doi.org/10.2478/if-2018-0006. ISSN 2533-4050 (tisk), 2533-4069 (online). Also available from: https://publikace.nm.cz/periodicals/fiamnpsbhn/74-1-2/rightcania-and-kvacekispermum-early-cretaceous-seeds-from-eastern-north-america-and-portugal-provide-further-evidence-of-the-early-chloranthoid-diversification|
Abundant flowers, fruits, seeds and stamens that are closely related to extant Chloranthaceae have been reported from the Early Cretaceous floras of Portugal. Among these are small berries with endotestal seeds assigned to the extinct genera Canrightia and Canrightiopsis. Here we describe two new genera, each including a single species, based on fossil fruits and seeds from the Early Cretaceous of eastern North America and Portugal. Both genera have pendent, orthotropous, bitegmic and endotestal ovules/seeds, in which the endotesta consists of a layer of cubic to palisade-shaped crystal cells with endoreticulate fibrous infillings, a combination of features that also characterize Canrightia and Canrightiopsis and that among extant angiosperms are known only for members of the Chloranthaceae. Rightcania kvacekii gen. et sp. nov. from the early to middle Albian Puddledock mesofossil flora of Virginia, USA, is the first representative in the Early Cretaceous floras of North America of a chloranthaceous fossil related to Canrightia and Canrightiopsis. It has three- to five-seeded fruits very similar to fruits and seeds of Canrightia, also with a pronounced tegmen that probably functioned as a nutritive tissue for the developing embryo. Fruits and seeds of Rightcania are larger than those of Canrightia, and also differ in details of the seed coat. Kvacekispermum rugosum gen. et sp. nov. is rare in the late Aptian to early Albian Portuguese mesofossil flora from Vale de Água. It differs from Canrightiopsis in the coarsely rugulate outer surface of the endotesta and its larger size, but is closely similar in the general structure of seed coat and nutritive tissue. Together, Rightcania and Kvacekispermum provide further evidence of the early diversity achieved by chloranthoid angiosperms before the end of the Early Cretaceous.