Llallawavis scagliai: a new Mesembriornithinae Terror Bird From Pliocene Neogene Argentina had Good Eyesight, but not as Good Hearing

A new Mesembriornithinae (Aves, Phorusrhacidae) provides new insights into the phylogeny and sensory capabilities of terror birds

Authors:

Degrange et al

Abstract:

Terror birds constitute the most outstanding group of the South American Cenozoic avifauna. Considered as apex predators, their hunting skills have recently been examined, but their diversity is still unresolved. Here we report a new terror bird from the late Pliocene of Argentina, represented by the most complete articulated skeleton of one yet found. Our phylogenetic analysis places this taxon among derived phorusrhacids (Mesembriornithinae). One of the most striking cranial features of the new species is the suppression of intracranial kinesis due to the presence of an independent ossified bone that increases the structural link between the lacrimal and jugal bars, and the absence of both palatal hinges. The new species possesses ossified tracheal rings and a tracheobronchial syrinx, as well as sclerotic ossicles to adjust the shape of the cornea during its diurnal vision, and reveals a mean hearing sensitivity (~2300 Hz) below the average for living species. The discovery of this new species provides new insights for studying the anatomy and phylogeny of phorusrhacids and a better understanding of this group's diversification.

The Giant Flightless Birds of Paleogene Europe

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.

Terror Birds of Eocene Europe Imply Trans-Tethys Disperal

“Terror Birds” (Phorusrhacidae) from the Eocene of Europe Imply Trans-Tethys Dispersal

Authors:

Angst et al.

Abstract:

Background

Phorusrhacidae was a clade including middle-sized to giant terrestrial carnivorous birds, known mainly from the Cenozoic of South America, but also occurring in the Plio-Pleistocene of North America and the Eocene of Africa. Previous reports of small phorusrhacids in the Paleogene of Europe have been dismissed as based on non-phorusrhacid material.

Methodology

we have re-examined specimens of large terrestrial birds from the Eocene (late Lutetian) of France and Switzerland previously referred to gastornithids and ratites and have identified them as belonging to a phorusrhacid for which the name Eleutherornis cotei should be used.

Conclusions/Significance

The occurrence of a phorusrhacid in the late Lutetian of Europe indicates that these flightless birds had a wider geographical distribution than previously recognized. The likeliest interpretation is that they dispersed from Africa, where the group is known in the Eocene, which implies crossing the Tethys Sea. The Early Tertiary distribution of phorusrhacids can be best explained by transoceanic dispersal, across both the South Atlantic and the Tethys.

Terror Bird Bites (and their biomechanics)

The ancient "terror bird" Andalgalornis couldn't fly, but it used its unusually large, rigid skull--coupled with a hawk-like hooked beak--in a fighting strategy reminiscent of boxer Muhammad Ali.

The agile creature repeatedly attacked and retreated, landing well-targeted, hatchet-like jabs to take down its prey, according to results of a new study published this week in the journal PLoS ONE.

The study is the first detailed look at the predatory style of a member of an extinct group of large, flightless birds known scientifically as Phorusrhacids but popularly labeled "terror birds" because of their fearsome skull and often imposing size.

Terror birds evolved about 60 million years ago in isolation in South America, an island continent until the last few million years, radiating into about 18 known species ranging in size up to the 7-foot-tall (2.1 meters) Kelenken.

Because terror birds have no close analogs among modern-day birds, their life habits have been shrouded in mystery, according to William Zamer, acting deputy director of the National Science Foundation (NSF)'s Division of Integrative Organismal Systems, which funded the research.

Now, a multinational team of scientists has performed the most sophisticated study to date of the form, function and predatory behavior of a terror bird, using CT scanning and advanced engineering methods.

"No one has ever attempted such a comprehensive biomechanical analysis of a terror bird," said study lead author Federico Degrange of the Museo de La Plata/CONICET in Argentina.

"We need to figure out the ecological role these amazing birds played if we really want to understand how the unusual ecosystems of South America evolved over the past 60 million years."

The terror bird under study is called Andalgalornis and lived in northwestern Argentina about six million years ago. It was a mid-sized terror bird, standing about 4.5 feet tall (1.4 meters) and weighing in at a fleet-footed 90 pounds (40 kg).

Like all terror birds, its skull was relatively enormous (14.5 inches or 37 centimeters) with a deep narrow bill armed with a powerful, hawk-like hook.

Paper co-author Lawrence Witmer of the Ohio University College of Osteopathic Medicine ran a complete skull of Andalgalornis through a CT scanner, giving the team a glimpse into the skull's inner architecture.

The scans revealed to Witmer, Degrange and article co-author Claudia Tambussi, also from the Museo de La Plata/CONICET, that Andalgalornis was unlike other birds because it had evolved a highly rigid skull.

"Birds generally have skulls with lots of mobility between the bones, which allows them to have light but strong skulls," said Witmer.

"But we found that Andalgalornis had turned these mobile joints into rigid beams. This guy had a strong skull, particularly in the fore-aft direction, despite having a curiously hollow beak."

The evolution of this large and rigid bony weapon was presumably linked to the loss of flight in terror birds, as well as to their sometimes gigantic sizes.

From the CT scans, Stephen Wroe, director of the Computational Biomechanics Research Group at the University of New South Wales, Australia, assembled sophisticated 3-D models of the terror bird and two living species for comparison (an eagle, and the terror bird's closest living relative, the seriema).

Using computers and software supplied by Wroe, Degrange and Karen Moreno of the Université Paul Sabatier in Toulouse, France, applied an approach known as Finite Element Analysis to simulate and compare the biomechanics of biting straight down (as in a killing bite), pulling back with its neck (as in dismembering prey) and shaking the skull from side to side (as in thrashing smaller animals, or when dealing with larger struggling prey).

Color images created by the program show cool-blue areas where stresses are low and white-hot areas where stresses get dangerously high.

The simulations supported the CT-based anatomical results.

"Relative to the other birds considered in the study, the terror bird was well-adapted to drive the beak in and pull back with that wickedly recurved tip of the beak," remarked Wroe, "but when shaking its head from side to side, its skull lights up like a Christmas tree."

A key part of the analysis was determining how hard a bite Andalgalornis could deliver.

To examine bite force in birds in general, Degrange and Tambussi worked with zookeepers at the La Plata Zoo to get a seriema and an eagle to chomp down on their bite meter.

"We discovered that the bite force of Andalgalornis was a little lower than we expected, and weaker than the bite of many carnivorous mammals of about the same size," Degrange said.

"Andalgalornis may have compensated for this weaker bite by using its powerful neck muscles to drive its strong skull into prey like an axe."

The team's results give new insight into the lifestyle of a unique avian predator.

Its skull, though strong vertically, was weak from side to side; its hollow beak was in danger of catastrophic fracture if Andalgalornis grappled too vigorously with large struggling prey.

Instead, the study shows that the terror bird engaged in an elegant style more like that of Muhammad Ali--a repeated attack-and-retreat strategy with well-targeted, hatchet-like jabs.

Once killed, the prey would have been ripped into bite-sized morsels by the powerful neck pulling the head straight back or, if possible, swallowed whole.

Freakin parrot from hell!

Also covered here, here, and here.