Late Cretaceous (Cenomanian–Turonian) macroflora from the Chatham Islands, New Zealand: Bryophytes, lycophytes and pteridophytes

Abstract

Late Cretaceous fossils from the Chatham Islands, New Zealand, represent an important high palaeolatitude (~70–80°S) flora. Located between eastern and western Gondwana, and prior to Late Cretaceous continental break-up, these plants grew during a period of global greenhouse climates. Macrofloral remains of the Tupuangi Formation, Pitt Island, accumulated in a deltaic floodplain setting with plant material occurring on well-developed, hydromorphic soil horizons or entrained in sediments overlying the soils. The macroflora includes a rich angiosperm–conifer–Ginkgo flora with subsidiary ferns, lycophytes and bryophytes. The components of the assemblage described herein include those of probable cryptogam affinity, and comprise one thalloid liverwort, one leafy moss (Muscites gracilis sp. nov.), one lycopod shoot, and three taxa of pteridophytic affinity, including a fern of probable osmundalean affinity (Cladophlebis auriculipilosus sp. nov.). The floral assemblage shares only one element with coeval localities across the Southern Hemisphere (Sphenopteris sp. cf. Sphenopteris warragulensis), and is characterised by relatively low fern diversity. The unique assemblage is attributed, at least in part, to ecological bias associated with local deltaic depositional settings. However, the relatively low osmundalean fern component follows global floristic trends for the Mid-Cretaceous, which saw a decline in diversity and abundance of ferns during the early phases of angiosperm diversification and rise to ecological dominance.