John F. Rigby

New evidence of reproductive organs of Glossopteris based on permineralized fossils from Queensland, Australia. I. Ovulate organ Homevaleia gen. nov.

This study describes Homevaleia gouldii H. Nishida, Pigg, Kudo et Rigby gen. et sp. nov., an ovule-bearing glossopterid organ, based on a combination of recently collected permineralized specimens from the Late Permian Homevale Station locality in the Bowen Basin of Queensland, Australia, and on previously studied material from the 1977 Gould and Delevoryas study. Homevaleia, which resembles the compression–impression genus Dictyopteridium, is an inrolled megasporophyll with a distinct keel that bears numerous (over 70) stalked ovules on its adaxial surface. Ovules are small, oval, with an elaborate mesh-like structure that is developed from the outermost integumentary layers. Specimens interpreted as representing different developmental stages show there is an apparent interrelationship between megagametophyte development and the opening of the surrounding fertile structure for pollination. Together, new information provided by this material enables better understanding of glossopterid reproductive structure and its function in one distinctive form.

Swimming sperm in an extinct Gondwanan plant

The now-extinct plant Glossopteris that dominated the Southern Hemisphere (Gondwana) during the Permian period serves as early evidence of continental drift, and may be ancestral to the group of seed plants known as angiosperms. Here we describe a 250-million-year-old fossil from Homevale in Queensland, Australia, of anatomically preserved pollen tubes and swimming male gametes from Glossopteris. The discovery of this simple reproductive system in Glossopteris has implications for its phylogenetic relationships with extant groups of seed plants (conifers and flowering plants, for example) and for the evolution of pollination biology in general.

Palaeobotany: Swimming sperm in an extinct Gondwanan plant

The now-extinct plant Glossopteris that dominated the Southern Hemisphere (Gondwana) during the Permian period serves as early evidence of continental drift, and may be ancestral to the group of seed plants known as angiosperms. Here we describe a 250-million-year-old fossil from Homevale in Queensland, Australia, of anatomically preserved pollen tubes and swimming male gametes from Glossopteris. The discovery of this simple reproductive system in Glossopteris has implications for its phylogenetic relationships with extant groups of seed plants (conifers and flowering plants, for example) and for the evolution of pollination biology in general.

The Mesozoic megafossil genus Linguifolium Arber 1917

Abstract The plant megafossil genus Linguifolium Arber 1917 is chiefly known from the Middle and Upper Triassic of Gondwana. The range of Linguifolium extended beyond Gondwana by the Late Triassic, persisting there through the earliest Jurassic (Hettangian). The parent plants probably grew in a well-watered, canopied environment. Diagnoses of the genus and four of its species - Linguifolium tenison-woodsii (Shirley 1898) Retallack 1980, L. waitakiense Bell in Bell et al. 1956, L. parvum Holmes & Anderson in Holmes et al. 2010, and L. steinmannii (Solms-Laubach 1899) Arber 1917 - are emended with particular reference to venation and leaf morphology; consequently, the stratigraphic ranges of the species have been more precisely defined. Coalescent venation has previously been reported in some species of Linguifolium and is identified in new material described herein. Although the vast majority of specimens assigned to the genus are from the Upper Triassic, none shows coalescent venation. This character is entirely restricted to the Middle Triassic, in particular to two species: L. waitakiense and L. parvum. Linguifolium tenison-woodsii is restricted to the Carnian-lowermost Norian of Australia and South Africa and is recorded here for the first time from the Tarong Basin (upper Carnian), Queensland. Confusion regarding assignment of specimens to this species from the Middle Jurassic of Queensland is resolved.

New evidence of the reproductive organs of Glossopteris based on permineralized fossils from Queensland, Australia. II: pollen-bearing organ Ediea gen. nov

Ediea homevalensis H. Nishida, Kudo, Pigg & Rigby gen. et sp. nov. is proposed for permineralized pollen-bearing structures from the Late Permian Homevale Station locality of the Bowen Basin, Queensland, Australia. The taxon represents unisexual fertile shoots bearing helically arranged leaves on a central axis. The more apical leaves are fertile microsporophylls bearing a pair of multi-branched stalks on their adaxial surfaces that each supports a cluster of terminally borne pollen sacs. Proximal to the fertile leaves there are several rows of sterile scale-like leaves. The pollen sacs (microsporangia) have thickened and dark, striate walls that are typical of the Arberiella type found in most pollen organs presumed to be of glossopterid affinity. An examination of pollen organs at several developmental stages, including those containing in situ pollen of the Protohaploxypinus type, provides the basis for a detailed analysis of these types of structures, which bear similarities to both compression/impression Eretmonia-type glossopterid microsporangiate organs and permineralized Eretmonia macloughlinii from Antarctica. These fossils demonstrate that at least some Late Permian pollen organs were simple microsporophyll-bearing shoot systems and not borne directly on Glossopteris leaves.

Swimming sperm in an extinct Gondwanan plant: Palaeobotany

The now-extinct plant Glossopteris that dominated the Southern Hemisphere (Gondwana) during the Permian period serves as early evidence of continental drift, and may be ancestral to the group of seed plants known as angiosperms. Here we describe a 250-million-year-old fossil from Homevale in Queensland, Australia, of anatomically preserved pollen tubes and swimming male gametes from Glossopteris. The discovery of this simple reproductive system in Glossopteris has implications for its phylogenetic relationships with extant groups of seed plants (conifers and flowering plants, for example) and for the evolution of pollination biology in general.