Valentin Krassilov

The origin of angiosperms

The claim of monophyletic origin of angiosperms arose from the confusion of phylogenetic and taxonomic concepts. Unpreconceived studies of extant angiosperms point to more than one archetype. Several lines of angiosperms have simultaneously entered the fossil record; the monocotyledons, proto-Hamamelidales, proto-Laurales and “proteophylls” (possibly ancestral to the Rosidae) are recognized among them. Three groups of Mesozoic seed plants — the Caytoniales, Czekanowskiales and Dirhopalostachyaceae — are distinguished as major sources of angiosperm characters (proangiosperms). Other Mesozoic lineages probably also contributed to the angiosperm character pool. Angiospermization is related to Mammalization and other processes involved in development of the Cenozoic lithosphere and biosphere.РЕФЕРАТПредставление о моно филетическом происх ождении покрытосеменных сло жилось в результате смешения филогенети ческих и таксономиче ских принципов. Непредвзя тый анализ современн ых цветковых указывет н а более чем один архетип. Несколь ко линий покрытосеме нных одновремено появили сь в палеонтологичес кой летописи, среди них на иболее важны однодольные, прото-га мамелидовые, протола вровые и “протеофиллы” (возм ожно, предки розоцветных). Главным источником ангиоспе рмных признаков могли быть три группы мезозойск их семенных растений — к ейтониевые. чекановс киевые и диропалостахиевые (проангиоспермы). Другие группы также, в озможно внесли свой вклад в “фонд при знаков”. Ангиосперми зация сопряжена с маммализ ацией и другими процессами, ведущими к формированию литос феры и биосферы.

Cretaceous flowers from Kazakhstan

Hyrcantha gen. nov. from the Middle Albian is a paniculate inflorescence. The flowers are bisexual with persistent calyx and apocarpous gynoecium. The carpels are ascidial with broad sessile stigma. The genus is related to the Ranunculaceae and Paeoniaceae. The Late Cretaceous Sarysua gen. nov. has cymoid inflorescences of many actinomorphic pentamerous flowers with syncarpous five-lobed ovaries and free styles. A geranialean affinity is suggested. In Taldysaja of the same age much reduced pistillate flowers are born in spikelets or solitary on branches of the fasciculate inflorescence. These findings evidence the important role to be of the ranunculoid—paeonioid complex among ancestral angiosperm and the considerable diversity of the Late Cretaceous flowering structures.

CLIMATIC CHANGES IN EASTERN ASIA AS INDICATED BY FOSSIL FLORAS. II. LATE CRETACEOUS AND DANIAN

Abstract Four Late Cretaceous phytoclimatic zones — subtropical, warm-temperature, temparature and boreal — are recognized in the Northern Hemisphere. Warm-temperature vegetation terminates at North Sakhalin and Vancouver Island. Floras of various phytoclimatic zones display parallel evolution in response to climatic changes, i.e., a temperature rise up to the Campanian interrupted by minor Coniacian cooling, and subsequent deterioration of climate culminating in the Late Danian. Cooling episodes were accompanied by expansions of dicotyledons with platanoid leaves, whereas the entire-margined leaf proportion increased during climatic optima. The floristic succession was also influenced by tectonic events, such as orogenic and volcanic activity which commenced in Late Cenomanian-Turonian times. Major replacements of ecological dominants occurred at the Maastrichtian/Danian and Early/Late Danian boundaries.

Contributions to the knowledge of the Caytoniales

Some additional features of the caytonialean capsule are described and the conventional interpretation of the “mouth” is challenged. The Caytonanthus pollen grains examined in the light and scanning electron microscope show a bilobed equatorial saccus sculptured with endosexinous ridges. The caytonialean seeds and androclads (Caytonanthus tyrmensis sp. nov.) from the uppermost Jurassic—lowermost Cretaceous Tyrma locality (Far East of the U.S.S.R.) are closely comparable with the corresponding organs of their Middle Jurassic predecessors showing striking evolutionary conservatism. However, the evolutionary potentials of the Caytoniales must not be understood. The caytonialean monandra and monogyna are considered as the nearest approach to angiosperm stamens and pistils.

New platanoid staminate heads from the mid-Cretaceous of Kazakhstan

Abstract Staminate heads described from the Late Cretaceous of Kazakhstan as Sarbaya Krassilov et Shilin, gen. nov. have individual flowers of four stamens and a much reduced perianth. Pollen grains are tricolporate with cingulate endoapertures. Both staminate heads and associated leaves with distinctive stomatal structures add to the morphological diversity of the Cretaceous platanoid complex.

Achene-like fossils from the lower cretaceous of the Lake Baikal area

Abstract Achene-like disseminules with a pappus of hypogynous hairs are described from the Lower Cretaceous lacustrine deposits of the Vitim River, Lake Baikal area. They are interpreted as uniovulate cupules with persistent receptacles bearing clusters of very long hairs. The receptacles can be occasionally detached from the cupules. Stone cells and tracheids of the cupule and the seed cuticles are described. In a single specimen, pollen grains are preserved at the top of the nucellus. They are monosulcate, showing alveolar exinal structure. These fossils are compared with bennettitalean strobili and cyperaceous achenes. The accompanying plants are mostly gymnosperms common in the Early Cretaceous Siberian province.

Diversity of Mesozoic gnetophytes and the first angiosperms

A provisionary system of gnetophytes is proposed, including recently discovered Mesozoic members. The following principal characters are used, in descending order of significance: strobilar structure of ovulate organs (eugnetophytes) as opposed to flowerlike cupules and their aggregates (anthognetophytes), radial vs. bilateral symmetry of seed cupules, and morphological distinctions in the pollen organs, pollen micromorphology and exine ultrastructure. The fossil members show mosaic associations of morphological traits, which attests to different evolution rates of their ovulate and pollinate structures. The system includes two superorders and eight orders, several of which are new. A dichotomous key is provided to differentiate between genera of fossil gnetophytes based on ovulate structures. Two stages in evolution of gnetophyte morphological diversity are recognized: first in the Triassic and then in the Early Cretaceous, the latter was associated with the origin of new type herbaceous wetland communities. Angiosperms or some of them might have originated as elements of gnetophyte diversity in such communities.

Pleuromeia from the lower triassic of the far east of the U.S.S.R.

Abstract Pleuromeia obrutschewii Elias from Russian Island (Russkiy Ostrov, near Vladivostok) is hardly distinguishable from the European P. sternbergii (Muenster) Corda. The sporangia are adaxial, filling spoon-like depressions of the megasporophylls which have sterile tips. P. olenekensis sp. nov. from the Olenek River (northeastern Siberia) has larger sporangia and much larger megaspores with three-layered walls. The outer layer (ectexosporium) is reticulate. It is assumed that in other species this layer is lacking due to imperfect preservation. Mature megasporophylls, when shed, have a buoy-like shape and are often deposited together with cephalopod shells. This suggests a special mechanism of propagation by means of megasporophylls dispersed by water currents. The cosmopolitan distribution of Pleuromeia points to weakened climatic zonation in the Early Triassic.

Pollen morphotypes from the intestine of a Permian booklouse

Abstract Two morphotypes of disaccate taeniate pollen grains Lunatisporites and Protohaploxypinus , and two types of monosaccate pollen grains, Florinites and Potonieisporites are recognized in the organic gut content of a primitive booklouse Parapsocidium uralicum G. Zalessky (Psocidiidae, Psocida) from the Tshekarda locality in the Urals. Details of infrastructure are described for Lunatisporites . Lamellate nexine was not observed in sectioned pollen grain of Protohaploxypinus perfecta . Pollen grains with several to many taeniae are abundant in the gut, whereas other morphotypes are represented by a single grain each. Such proportions are typical for pollinivorous insects from Tshekarda. Parapsocidium has shared its foraging habitat with another pollinivorous insect, Idelopsocus diradiatus Rasnitsyn (Hypoperlida). The latter is considered as a representative of an extinct group ancestral to booklice.

New hamamelid infructescences from the Paleocene of western Kamchatka, Russia

Hamamelid inflorescences and infructescences from Late Paleocene deposits of Kamchatka, Russian Far East, are assigned to a new genus Evacarpa N. Maslova et Krassilov, gen. nov. The inflorescences are similar to the respective extant and fossil platanoid structures (Platanaceae) in general form of pistillate heads and their arrangement on reproductive axes, unsealed carpels and their diachronous ripening, but differ in having fewer florets per head, paired carpels, intrafloral phyllomes, numerous ovules and the absence of a perianth. The latter characters are shared with Liquidambar and Altingia. These fossils contribute to knowledge of early hamamelid diversity but may also be relevant to current concepts of primitiveness in floral morphology.