Exceedingly well-preserved bird fossil specimens dating 50 million years represent a new species that is a previously unknown relative of the modern-day ostrich, according to a new paper co-authored by Sterling Nesbitt of Virginia Tech's College of Science and part of the university's Global Change Center.
The bird fossils were found more than a decade ago, completely intact with bones, feathers, and soft tissues in a former lake bed in Wyoming. Nesbitt cannot hide a grin as he calls the fossil a once-in-a-lifetime discovery for paleontologists.
"This is among one of the earliest well-represented bird species after the age of large dinosaurs," said Nesbitt, an assistant professor in the Department of Geosciences.
"You can definitely appreciate how complete these fossil are," added Nesbitt of the remains, the focus of a research paper co-authored by Nesbitt and newly published in the Bulletin of the American Museum of Natural History.
A new study suggests that the flightless birds named moa were completely extinct by the time New Zealand's human population had grown to two and half thousand people at most.
The new findings, which appear in the prestigious journal Nature Communications, incorporate results of research by international teams involved in two major projects led by Professor Richard Holdaway (Palaecol Research Ltd and University of Canterbury) and Mr Chris Jacomb (University of Otago), respectively.
The researchers calculate that the Polynesians whose activities caused moa extinction in little more than a century had amongst the lowest human population densities on record. They found that during the peak period of moa hunting, there were fewer than 1500 Polynesian settlers in New Zealand, or about 1 person per 100 square kilometres, one of the lowest population densities recorded for any pre-industrial society.
They found that the human population could have reached about 2500 by the time moa went extinct. For several decades before then moa would have been rare luxuries.
Estimates of the human population during the moa hunting period are more sensitive to how long it took to exterminate the birds through hunting and habitat destruction than to the size of the founding population.
The middle Eocene European “ratite” Palaeotis (Aves, Palaeognathae) restudied once more
Author:
Mayr
Abstract:
Palaeotis weigelti is a flightless, “ratite”-like palaeognathous bird, which occurs in the Middle Eocene of the German fossil sites Messel and the Geisel Valley. The species is known from several specimens, most of which are, however, very fragmentary or poorly preserved. Its phylogenetic affinities are controversial, with earlier authors especially considering close affinities to Struthionidae and Rheidae, and some skeletal features were only briefly described. Moreover, recent molecular analyses congruently indicate that a “ratite” morphology evolved multiple times within palaeognathous birds. The skeletal morphology and phylogenetic affinities of Palaeotis are therefore reanalyzed, and the taxon is subjected to a phylogenetic analysis based on one of the most comprehensive published data sets for palaeognathous birds. In addition to the primary analysis, further analyses were run that were constrained to a backbone topology reflecting the results of sequence-based studies. In none of these analyses was a well-supported placement of Palaeotis obtained, and it is concluded that current data do not convincingly resolve the affinities of this taxon. Palatal morphology of Palaeotis most closely resembles that of lithornithids, another group of palaeognathous birds from the Eocene of the Northern Hemisphere, and there remains a possibility that the “ratite” features of Palaeotis evolved independently from those of the extant taxa.
Stratigraphic distribution of large flightless birds in the Palaeogene of Europe and its palaeobiological and palaeogeographical implications
Authors:
Buffetaut et al
Abstract:
The stratigraphic distribution of the three main groups of large flightless birds known from the Palaeogene of Europe, Gastornithidae, Phorusrhacidae and Ratitae, is reviewed. The huge, herbivorous gastornithids, represented by the single genus Gastornis, are known from the Selandian (Middle Palaeocene) to the late Lutetian (Middle Eocene), being recorded from reference levels MP5 to MP13. The carnivorous phorusrhacids are represented by a single species, Eleutherornis cotei, from the late Lutetian (MP14, late Middle Eocene). The ratites have a patchy distribution, being represented by two species of moderate size, Remiornis heberti from the Thanetian (MP6, Late Palaeocene) and Palaeotis weigelti from the Lutetian (MP11 to MP13, Middle Eocene). The stratigraphic distributions of large eggs referred to gastornithids in the Late Palaeocene and Early Eocene of southern Europe and the occurrence of enigmatic large avian footprints in the Late Eocene of France are discussed. Whereas gastornithids and ratites co-existed in both the Palaeocene and the Middle Eocene, phorusrhacids seem to have been the only large ground birds in Europe at the end of the Middle Eocene. The palaeobiogeographical and evolutionary implications of the stratigraphic distributions of those groups of large birds in Europe are discussed. As Gastornis first appears in North America and in Asia in the Early Eocene, it is likely that gastornithids originated in Europe and later spread to other land masses during a dispersal event close to the Palaeocene–Eocene boundary. Prior to that, gastornithids evolved on the European “island continent”, where they were the largest terrestrial tetrapods during the Palaeocene. Gastornithids do not seem to have been significantly affected by the PETM. Ratitae have a more patchy record and relationships between Remiornis and Palaeotis remain unclear. Nevertheless, those European forms are among the earliest known ratites and this should not be overlooked in discussions of ratite evolution and palaeobiogeography. Phorusrhacids appear to have been present in Europe for only a short time and are interpreted as the result of dispersal from Africa followed by local extinction.
Giant moa bird (Dinornis robustus, literally meaning 'robust strange bird') may not have actually had robust bones, according to new research conducted by The University of Manchester. The leg bones of one of the tallest birds that ever existed were actually rather like those of its modern (but distant) relatives, such as ostrich, emu and rhea, the studypublished in PLOS One today (18 December) shows.
The study, led by biomechanics researcher Charlotte Brassey, in collaboration with palaeobiologist Professor Richard Holdaway at the University of Canterbury in New Zealand, has found that the largest of the moa species had leg bones similar to those of modern flightless birds that can run fast, whereas a much smaller species of moa – from a different family - had an extremely robust skeleton.
Ms Brassey said:"Our research suggests that this group of birds came up with several different solutions to deal with the problem of supporting the large body necessary to process a diet of coarse vegetation.
"We know that these species of moa were living together in the same locations, at the same time. So we don't think the differences we're seeing in leg robustness are adaptations to a particular habitat type.
"Instead it seems they were perhaps engaging in different behaviours, although both could deal with extremely rough terrain."
The flighted ancestor of birds such as the Australian emu and cassowary became too heavy to fly after the extinction of dinosaurs made it safer to forage for food, a new study suggests.
The finding by Australian National University (ANU) biologist Dr Matthew Phillips and colleagues at Massey University in New Zealand also answers the mystery of how flightless birds managed to disperse across oceans.
Their work, published in the latest Systematic Biology journal, follows on from recent work that raised uncertainty about the "single ancestor" theory of the group of flightless birds, known as ratites.
Dr Phillips says ratites are a group of flightless birds that include the Australian emu and cassowary, African ostrich, New Zealand's kiwi and now-extinct moa, rhea from South America and the extinct elephant birds of Madagascar.
The study used molecular dating of the mitochondrial DNA from the moa, which stood 2.5 metres tall and weighed up to 250 kilograms, and found its closest relative to be the tinamous - a flighted bird the size of quail, found in South America.
Previously it was thought ratites all shared a common flightless ancestor about 80 million years ago and their worldwide dispersal occurred before the supercontinent of Gondwanaland broke up.
But Dr Phillips says the problem with this theory was that much of the continental break-up occurred well before the proposed common ancestor.
Fewer predators
The study, which also included DNA sequencing of 22 bird species including flightless and flighted birds, shows ratites became flightless around 65 million years ago.
This coincides with the extinction of dinosaurs in the Cretaceous-Tertiary event.
"Our study suggests that the flighted ancestors of ratites appear to have been ground-feeding birds that ran well," Dr Phillips said.
"In the absence of predators and with abundant food resources on the ground, there is a tendency for birds to evolve larger size and become flightless.
"We see this a lot on islands - dodos for example.
"Larger ground-feeding birds can be more efficient at turning food into growth and reproduction, but with size increase, comes the cost of flight becoming less efficient."
Dr Phillips says the study also throws doubt on the widely held view that the ratite's origins lie in the Gondwana supercontinent that included Africa, South America, Australia, New Zealand, India and the Antarctic.
Interesting...
