Nordenskioldia and Trochodendron (Trochodendraceae) from the Miocene of Northwestern North America

Botanical Gazette 09/1991; 152(3). DOI: 10.1086/337898

ABSTRACT The extinct trochodendraceous genus Nordenskioldia, well represented in the Paleocene of the Northern Hemisphere, is documented for the first time from the Neogene, based upon infructescences, fruits, associated twigs, and foliage from the Miocene of Idaho, Washington, and southern British Columbia. The infructescences and fruits, assigned to Nordenskioldia interglacialis (Hollick) comb. nov., are very similar to Paleocene N. borealis, but differ in ranging to a higher number of carpels per fruit and in being less regularly dehiscent. The leaves, Zizyphoides auriculata (Heer) comb. nov., formerly attributed to Populus and Cocculus, are clearly congeneric with the leaves associated with Nordenskioldia in Paleocene deposits. Zizyphoides auriculata leaves differ from Paleocene Z. flabellum in having generally more prominent dentations along the margin and a broader divergence of the lateral primary veins. Excellent preservation of the Miocene material reveals features not preserved in the Paleocene specimens, and in particular, lignified fruitlets clearly show aborted ovules in addition to the single mature seed. Infructescences of Trochodendron are also documented from the same Miocene localities at which N. interglacialis occurs. The close similarities between Paleocene and Miocene species of Nordenskioldia, and also between the Miocene and extant species of Trochodendron, suggest relative stasis in the morphological evolution of the Trochodendraceae over intervals of up to 45 million years.

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    ABSTRACT: Most angiosperms have gynoecia with two to five carpels. However, more than five carpels (here termed ‘multicarpellate condition’) are present in some representatives of all larger subclades of angiosperms. In such multicarpellate gynoecia, the carpels are in either one or more than one whorl (or series). I focus especially on gynoecia in which the carpels are in a single whorl (or series). In such multicarpellate syncarpous gynoecia, the closure in the centre of the gynoecium is imprecise as a result of slightly irregular development of the carpel flanks. Irregular bumps appear to stuff the remaining holes. In multicarpellate gynoecia, the centre of the remaining floral apex is not involved in carpel morphogenesis, so that this unspent part of the floral apex remains morphologically undifferentiated. It usually becomes enclosed within the gynoecium, but, in some cases, remains exposed and may or may not form simple excrescences. The area within the remaining floral apex is histologically characterized by a parenchyma of simple longitudinal cell rows. In highly multicarpellate gynoecia with the carpels in a whorl, the whorl tends to be deformed into an H-shaped or star-shaped structure by differential growth of the floral sectors, so that carpels become aligned in parallel rows, in which they face each other with the ventral sides. In this way, a fractionated compitum may still be functional. Multicarpellate gynoecia (with the carpels in one whorl or series) occur in at least one species in 37 of the 63 angiosperm orders. In contrast, non-multicarpellate gynoecia are present in at least one species of all 63 orders. The basal condition in angiosperms is more likely non-multicarpellate. Multicarpellate gynoecia are restricted to flowers that are not highly synorganized. In groups with synorganized androecium and gynoecium and in groups with elaborate monosymmetric flowers, multicarpellate gynoecia are lacking. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 1–43.
    Botanical Journal of the Linnean Society 01/2014; 174(1). · 2.70 Impact Factor
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    ABSTRACT: Trochodendron aralioides is the sole member of the family Trochodendraceae, which belongs to the basal eudicots, has vesselless wood, and lacks a distinct perianth. Our observations confirmed that there are numerous perianth-like structures and that the number of these structures differs between protandrous and protogynous flowers and among the positions within an inflorescence. The epidermal cells on many floral parts of T. aralioides are papillate or conical, similar to the ones of ordinary showy petals of other species. The data in this article support the hypothesis that the perianth of Trochodendron has been secondarily lost and suggest that some aspects of petal identity, e.g., papillate cells, have been retained that might be important for pollinator attraction. We have identified 11 homologues of floral organ identity genes—two A-class, three B-class, two C-class, and four E-class homologous genes—from T. aralioides. Phylogenetic analysis shows that all of the genes arose before a major duplication of MADS-box genes at the base of the core eudicots. Expression patterns for those floral organ identity gene homologues was determined by reverse transcriptase PCR, which showed variations that do not conform well to the current floral ABCDE model. In addition, all paralogous genes have distinct expression patterns, suggesting that they had undergone functional divergence.
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