ThePentoxylonplant

Abstract

The various dispersed organs belonging to the Pentoxylon plant viz. Pentoxylon (stem), Nipaniophyllum (leaf), Sahnia (male flower) and Carnoconites (female cone) have been studied in detail. Apart from the long shoots (type 1 shoots), the plant bore three different kinds of short shoots: the thick woody short shoots, each with a broadly conical head (type 2 shoots); the slender parenchymatous short shoots (type 3 shoots); and the slightly thicker parenchymatous short shoot (type 4 shoot) terminating in a Sahnia flower. In addition to the well known Nipaniophyllum raoi leaves a second species, N. hobsonii sp. nov., is recognized. In Sahnia the sporangiophores were borne on a collar-like structure formed by the raised margin of the receptacle. The broadly conical head of the thick woody short shoot (type 2 shoot) might be the basis of the cone-bearing branchlets of Carnoconites fruits. The seeds of Carnoconites are spirally arranged rather than being in longitudinal rows as previously suggested. Pentoxylon was probably a shrubby plant which grew beside water. It sent up erect branched leafy shoots which after a few seasons of growth flopped onto the ground or on other stems, making a thicket. Although the stem, Pentoxylon , resembles Medullosa and Rhexoxylon anatomically, the reproductive parts of the plant, Sahnia and Carnoconites , are unlike those of any group of gymnosperms. The Pentoxylon plant is accordingly regarded as an extinct gymnosperm of unknown affinity. Nipanioxylon guptai has previously been regarded as related to Pentoxylon , but its holotype is believed to be a conifer and has nothing to do with the Pentoxylon plant.

The Pollination of Mid Mesozoic Seed Plants and the Early History of Long-proboscid Insects1,2,3

“…Examples are (1) Allicospermum xystum Harris (Harris, 1935) (Yimiaceae); (2) Petriella triangulata Taylor (Taylor et al, 1994) (Petriellaceae); (3) Alvinia bohemica Kvacek (Kvacek, 2000) (Coniferales: Cheirolepidiaceae) (Labandeira et al, 2007a); (4) Leptostrobus cancer Harris (Harris, 1951b) (Czekanowskiaceae); (5) Problematospermum ovale Turutanova-Ketova (?Gnetales) (Wang, pers. comm., 2009;Wang et al, 2009); (6) Carnoconhes compactus Srivastava (Pentoxylaceae) (Bose et al, 1985); (7) Caytonia sewardi Harris (Harris, 1933) (Caytoniaceae); (8) Monimia rotundifolia Thouars (Monimiaceae) (Heywood, 1993); (9) Jerseyanthm calycanthoides Crepet (Crepet et al, 2005) (Calyeanthaceae); (10) Paleorosa similkameensh (Rosaceae) (Stewart & Rothwell, 1993); and (11) Vanilla planifolia Andrews (Orchidaceae). m designed to crush pollen (Jervis & Vilhelmsen, 2000).…”

“…A three-dimensionally preserved, silicified fructification bearing an arc of ca. 12 seeds embedded in fleshy tissue was described by Nishida and Hayashi (1996), which was assigned to the Pentoxylales, most likely a new lineage similar to \Pentoxylon (Bose et al, 1985). In this specimen was an excellently preserved, reflexed larva enclosed in a lined ellipsoidal chamber amid interseminal fleshy tissue, adjacent to seeds (Nishida & Hayashi, 1996).…”

“…PENTOXYLALES Pentoxylales were first described from India (Sahni, 1948), based on Pentoxylon, an anatomically distinctive trunk form-genus that ranged from late Early Jurassic to late Early Cretaceous and with mostly a Gondwanan distribution. The best-known, whole-plant pentoxylalean is a shrub, with affiliated Pentoxylon stems, fNipaniophyllum foliage, 'fCarnoconites ovulate organs, "fSahnia pollen organs, and monocolpate pollen often affiliated with some 'fCycadopites species, which were 17-22 um long (Bose et al, 1985;Osborn et al, 1991b). Micropyles of ovules breaching the surface of conelike organs are very short, from 1 to 3 um deep, presumably requiring the smallest of longproboscid or small nonproboscid insects for pollination.…”

Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

“…Redefined in terms of mature secondary xylem to address the condition in cordaites, where scalariform pitting extended into the early secondary xylem but gave way to circular bordered. Carlquist (1996a) stated that Pentoxylon had scalariform pitting, based on VishnuMittre (1957), but this was refuted by Bose et al (1985). Carlquist (1996a) questioned the previous scoring of cycads as (0/1) because scalariform pitting occurs in the early secondary xylem of Cycas, but because it is lacking in mature secondary xylem I have retained the previous scoring.…”

Generalist flowers and phytophagous beetles in two tropical canopy trees: resources for multitudes

“…• The Bennettitopsida, consisting of the Bennettitales and tentatively, the Pentoxylales, comprised a group, perhaps a clade, readily differentiated from superficially similar cycads by possession in most species of bisexual strobili and a second ovular integument (Bose & al., 1985;Crane, 1988), features which they share with gnetopsids and angiosperms (Crepet & al., 1991). The Bennettitales are known for their flower-like strobili consisting of a robust, central, columnar-to domeshaped receptacle bearing numerous pedunculate ovules interspersed among interseminal scales.…”