Nordenskioldia and Trochodendron (Trochodendraceae) from the Miocene of Northwestern North America
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.
- SourceAvailable from: onlinelibrary.wiley.com[Show abstract] [Hide abstract]
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). · 2.59 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Megafossils and pollen data are used to compare the flora found at the McAbee site, located near the town of Cache Creek, British Columbia, to six other well-collected Eocene lacustrine floras of Washington and western British Columbia. A diverse flora is found at McAbee consisting of at least 87 taxa. Gymnosperms are common, including sixteen separate species, 14 conifers and two ginkgos. A minimum of 67 angiosperm genera are represented in the flora, many yet to be described. The dominant dicotyledonous elements of the leaf assemblage at McAbee include Fagus (also represented by nuts and cupules) with Ulmus and representatives of the Betulaceae, especially Betula and Alnus. The confirmation of Fagus, also rarely found from sites at Princeton, British Columbia, and Republic, Washington, provides the oldest well-documented occurrence of the genus, predating the Early Oligocene records of Fagus previously reported for North America, Asia, and Europe. Data provided by pollen analysis broadens our knowledge of the McAbee flora. Angiosperm pollen typically predominates over gymnosperms with the Ulmoideae and Betulaceae being the most common angiosperm pollen types. Members of the Pinaceae dominate the gymnosperm pollen record. Paleoclimatic estimates for McAbee are slightly cooler than for the Republic and Princeton localities and thermophilic elements, such as Sabal found at Princeton or Ensete and Zamiaceae found at Republic are not known from McAbee. Résumé : Les données provenant de mégafossiles et de pollens sont utilisées pour comparer la flore trouvée au site McAbee, à proximité de la ville de Cache Creek en Colombie-Britannique, à celles de six autres bonnes collections de flores lacustres éocènes de l'État de Washington et de l'ouest de la Colombie-Britannique. McAbee présente une flore diversifiée comprenant au moins quatre-vingt-sept taxons. Les gymnospermes y sont fréquemment trouvées, incluant seize espèces distinctes, quatorze conifères et deux ginkgos. Au moins soixante-sept genres d'angiospermes sont représentés dans la flore, dont plusieurs restent à décrire. Les éléments dicotylédones dominants de l'assemblage des feuilles à McAbee comprennent Fagus (aussi représenté par des noix et des cupules) et Ulmus et des représentants des Bétulacées, surtout Betula et Alnus. La confirmation de Fagus, aussi rarement trouvé à des sites à Princeton, Colombie-Britannique et Republic, Washington, fournit les plus anciennes occurrences bien documentées du genre, précédant les premiers enregistrements oligocènes de Fagus antérieurement rapportés pour l'Amérique du Nord, l'Asie et l'Europe. Les données fournies par les données d'analyse de pollen élargissent nos connaissances de la flore McAbee. Le pollen d'angiosperme prédomine typiquement sur les gymnospermes, les Ulmoidées et les Bétulacées étant les types de pollens angiospermes les plus fréquents. Les membres des Pinacées dominent les pollens de gymnospermes. Les estimés paléoclimatiques pour McAbee sont légèrement plus froids que pour les localités de Republic et de Princeton et les éléments thermophiles tels que Sabal, trouvé à Princeton, ou Ensete et les Zamiacées, trouvés à Republic, ne sont pas connus à McAbee.Canadian Journal of Earth Sciences 01/2005; 42(2):151-166. · 1.37 Impact Factor
- [Show abstract] [Hide abstract]
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.