Elaborating the fossil history of Banksiinae: a new species of Banksieaephyllum (Proteaceae) from the late paleocene of New South Wales

Abstract

Leaf fragments from Late Paleocene sediments at Cambalong Creek in the Southern Highlands of New South Wales are assigned to a new species ofBanksieaephyllum Cookson & Duigan,B. praefastigatum. A study of leaf form andmicromorphological characters of extant Banksieae was carried out to identify possible affinities for the new taxon, and a compendium of the architecturaland micromorphological characters of leaves of all described species ofBanksieaephyllum andBanksieaeformis Hill & Christophel is presented.Banksieaephyllum praefastigatum has characteristicstomatal and trichome features of both extinct and extant species ofBanksiinae, but is dissimilar in leaf morphology to any extant species ofBanksia L.f., Dryandra R.Br., orthe oldest previously described species ofBanksieaephyllum, B. tayloriiCarpenter, Hill & Jordan, with which it was contemporaneous.Banksieaephyllum praefastigatum, with its stronglydeveloped areolation and superficial stomates, is different from extantspecies of Banksiinae and Musgraveinae, and may represent a now-extinct sistertaxon to these subtribes in Banksieae, one which had not changed substantiallyfrom hypothesised mesophytic ancestral Proteaceae. Leaf morphology ofB. praefastigatum indicates that serrate-, lobed-andentire-margined forms of Banksieaephyllum were coeval in many localities throughout southern Australia during the Tertiary, and that Banksiinae had diversified significantly by the Early Tertiary, reflecting diversification of at least several other subtribes of subfamily Grevilleoideae by that time.