Tertiary fossil waterfowl (Aves: anseriformes) of Australia and New Zealand.

Abstract

Anseriformes, or waterfowl, are related to Galliformes (chickens and kin), together forming the most basal sister of Neoaves. The order is generally considered to comprise four families: Presbyornithidae (Late Cretaceous - Eocene); Anseranatidae (Paleocene-present); Anhimidae (Oligocene-present); Anatidae (Oligocene-present), but the giant Tertiary flightless taxa Dromornithidae (Australia), Gastornithidae (Eurasia) and Diatrymidae (North America) have also been referred to the order. Australasia presently has a unique waterfowl fauna characterized by low species diversity but high phylogenetic diversity: the Magpie Goose Anseranas (the sole surviving anseranatid), several monotypic endemic anatid genera of uncertain relationships (Cape Barren Goose Cereopsis, Freckled Duck Stictonetta, Pinkeared Duck Malacorhynchus and Musk Duck Biziura), several relatively primitive taxa (the aforementioned plus whistling ducks Dendrocygna and Blue-billed Duck Oxyura). The evolutionary history of this fauna has, until now, not been examined via the fossil record. In this thesis, the literature for the global fossil record of Anseranatidae and Anatidae is reviewed. The Neogene (Oligocene-Pliocene) fossil record of Anseriformes, exclusive of dromornithids, is studied from both New Zealand and Australia. For New Zealand, all materials derive from the St Bathans Fauna, Early Miocene (19-16 Ma), Otago. Herein, the first description of this fauna is provided, with four anatid genera (Manuherikia, Dunstanetta, Matanas and Miotadorna) established for five species, with a sixth taxon reported (Chapter 2). The phylogenetic affinities of Manuherikia, Dunstanetta and Miotadorna are examined using parsimony analysis of morphological data (133 characters) in Chapter 3. Miotadorna is a shelduck related to tadornines, perhaps sister to Tadorna, and Manuherikia and Dunstanetta are oxyurines related to the Stictonetta, Malacorhynchus, Oxyura and Biziura). A further species of Manuherikia and the existence of definite anserines, probably related to Cereopsis, are described in Chapter 4. The fossil record of Australian anseriforms is described in Chapters 5-8. The Oligo- Miocene record derives principally from the Etadunna and Namba Formations (26-24 Ma) in the Lake Eyre and Frome Basins, respectively, in South Australia. Four taxa are described, with all occurring both in the Namba and Etadunna Formations: a single genus, Pinpanetta, is established for three species and another, Australotadorna, for a tadornine. Phylogenetic analyses (parsimony and Bayesian) of a dataset (150 characters, 61 taxa) show Pinpanetta is an oxyurine and confirm the previously found oxyurine affinity of Manuherikia and Dunstanetta. A monophyletic clade with moderate support is found for an expanded Oxyurinae that has Stictonetta basal, followed successively by Mionetta (Oligo- Miocene of Europe), Malacorhynchus, Pinpanetta, Manuherikia, Dunstanetta, Oxyura and Nomonyx, Biziura and Thalassornis. This same analysis finds anserines the most basal group in Anatidae, so changing position with Dendrocygna, considered by recent authors to be the most basal anatid. A new genus and species of anseranatid is described from a Faunal Zone A (System A, Late Oligocene) deposit at Riversleigh, northwestern Queensland (Chapter 6). This first pre-Pliocene record of the family in Australia is of equivalent age to the youngest European fossil anseranatid, Anserpica from France, but younger than the Eocene Anatalavis of England. Only one of three other waterfowl bones known from Riversleigh deposits is identifiable and is referred to a species of Pinpanetta found in the Etadunna Formation. Mid-Late Miocene deposits containing waterfowl are restricted in Australia to just the Waite Formation (c. 8 Ma) at Alcoota in the Northern Territory. Three bones indicate an undetermined tadornine and an undetermined anatid, different from any known species. The Pliocene record of anseriforms in South Australia is described from the Tirari Formation (Kanunka and Toolapinna Faunas) (Chapter 7). Nine modern species (Anseranas semipalmata, Cereopsis novaehollandiae, Cygnus atratus, Tadorna tadornoides, Biziura lobata, Oxyura australis, Anas cf A. castanea, A. cf A. gracilis and Aythya australis) are represented. A single extinct species, Tirarinetta kanunka, is described and referred to Oxyurinae. From the Parilla Sands, Late Pliocene, at Bookmark Cliffs on the Murray River, a single humerus is described (Chapter 8) and referred to Tadorna cf. T. tadornoides. A total of 11 anatid taxa is described from latest Oligocene-Early Miocene deposits in Australasia, which considerably adds to the global record of seven species previously reported for this period. Considering also the anseranatids, the Late Oligocene – Early Miocene fauna of Australia is thus established as having equivalent diversity to that from similar-aged deposits in Europe, but by the late Early Miocene, the New Zealand fauna was more diverse than any other Oligo-Miocene fauna known. The more limited samples available, compared to those from New Zealand, probably explain the lack of a similar diversity being revealed for Australia from this period. In both Australia and New Zealand, the Oligo-Miocene faunas are dominated by oxyurine taxa, as were those in Europe. The presence of a tadornine in Australia in the latest Oligocene and another in New Zealand in the Early Miocene precede the appearance of this subfamily in the Northern Hemisphere by 10 Ma, implying a southern origin for this group. The Late Oligocene presence of Mionetta in Europe and of Pinpanetta in Australia, and their referral to Oxyurinae, establishes a minimum age for the origin of this subfamily in the latest Oligocene. The establishment of a fauna comprised of modern species by the Pliocene indicates substantial faunal turnover probably in the Late Miocene. This turnover is due in part to immigration of taxa (Cygnus, Anas, Aythya) and in situ evolution (all endemic genera), as occurred in other Australian vertebrates (rodents, snakes, bats). Thus faunal composition in Australia appears to have been more affected by attainment of some threshold in proximity to Asia being breached by the northward continental drift of Australia, than by aridification, which has been ongoing since the Middle Miocene.