Vorombe titan – The Biggest Bird That Ever Lived

Scientists writing in the open access journal “Royal Society Open Science” have undertaken the first taxonomic revision for a very long time of the enigmatic family of giant, flightless birds, the “Elephant Birds”, that once roamed Madagascar.  In the first detailed study into the Aepyornithidae for fifty years, the research team concluded that their taxonomy is in fact spread across three genera and at least four distinct species.  Emerging out of this revision is Vorombe titan (meaning ‘big bird’ in Malagasy and Greek), the largest avian described to date.

Vorombe titan

V. titan may have lived as recently as 1,000 years ago and although standing more than three metres high and tipping the scales at an estimated eight hundred kilograms, this giant was relatively harmless, feeding on fruit, nuts and leaves.

At Around 3 Metres Tall and Weighing 800 Kilograms Vorombe titan is the Biggest of the Aepyornithidae

Picture credit: Jaime Chirinos

Researchers at the international conservation charity, the Zoological Society of London’s Institute of Zoology, have used complex statistical analysis to reorder the Aepyornithidae, discovering unexpected diversity in these Madagascan birds.

Complicated Taxonomy

The first scientific assessments of the “Elephant Birds” took place in the 1850s and species and genera assignment was based on comparative analysis, measurements and observed differences between fossils and bone specimens.  It had previously been suggested that up to fifteen different species made up the Aepyornithidae, assigned to two genera (Aepyornis and Mullerornis).  The scientists in this new study, coupled comparative analysis techniques familiar to 19th century anatomists with the latest multivariate cluster analysis and Bayesian statistical processes to re-examine these large-bodied ratites.

Using specimens from museums all over the world, the team identified three genera and at least four distinct species, as well as confirming that Vorombe titan is the biggest bird species known to science.

The World’s Largest Bird

The first species to be described, Aepyornis maximus, had been considered to be the world’s largest avian.  However, in 1894, British scientist C.W. Andrews described an even larger species, Aepyornis titan, but this idea was controversial, the specimen ascribed to this new species – A. titan being thought by many scientists and academics to represent an unusually large example of A. maximus.

This new study establishes enough unique characteristics in the material associated with A. titan to conclude that it is, indeed, a separate species.  The size, morphology and robust nature of its bones are so different from all other members of the Aepyornithidae, that this specimen has been placed in its own genus and named Vorombe titan.

The Robust Femur of V. titan

Picture credit: Royal Society Open Science

Lead author of the study, Dr James Hansford (Zoological Society of London’s Institute of Zoology) explained:

“Elephant birds were the biggest of Madagascar’s megafauna and arguably one of the most important in the islands evolutionary history, even more so than lemurs.  This is because large-bodied animals have an enormous impact on the wider ecosystem they live in via controlling vegetation through eating plants, spreading biomass and dispersing seeds through defecation.  Madagascar is still suffering the effects of the extinction of these birds today.”

Helping to Understand the Evolution of a Unique Island Community

Co-author Professor Samuel Turvey (Zoological Society of London’s Institute of Zoology), added:

“Without an accurate understanding of past species diversity, we can’t properly understand evolution or ecology in unique island systems such as Madagascar or reconstruct exactly what’s been lost since human arrival on these islands.  Knowing the history of biodiversity loss is essential to determine how to conserve today’s threatened species.”

This research links and clarifies the 19th century research with the very latest machine learning and Bayesian clustering statistical techniques, helping to solve a taxonomic muddle.  With a better understanding of these extinct avian megafauna scientists will learn important lessons about the impact extinctions have on island communities.

The revelation that the biggest of these birds was forgotten by history is just one part of the remarkable story of the “Elephant Birds”.

The scientific paper: “Unexpected Diversity within the Extinct Elephant Birds (Aves: Aepyornithidae) and a New Identity for the World’s Largest Bird” by James P. Hansford, Samuel T. Turvey published by the Royal Society Open Science.

Visit the Everything Dinosaur website: Everything Dinosaur.

Labelling the Fenestrae in a Diapsid Skull

Recently, Everything Dinosaur posted up a picture of the skull of a large gharial and discussed the teeth located in distinct sockets, an anatomical trait characteristic of that great group of reptiles the archosaurs (Archosauria).  Today, we complete this very brief look at the archosaurs by labelling the fenestrae (holes) in the skull that identify the gharial, all crocodiles and their close relatives, including the dinosaurs, that are classified as diapsid reptiles.

The Skull of the Gharial with the Eye Socket (Orbit) and Fenestrae Labelled

Picture credit: Everything Dinosaur

Studying the Archosaurs

The gharial (a long-snouted, crocodilian), skull is from the Grant Museum of Zoology and Comparative Anatomy (London).  In the photograph (above), we have labelled the holes (fenestrae) in the skull, the left lateral side of the skull is seen and the lower (inferior) temporal fenestra has been labelled.  Behind the large orbits (eye sockets), on the top of the skull, the pair of upper (superior) temporal fenestrae have been labelled.  Please note each of the holes (singular) is termed a fenestra, but the plural is fenestrae.

The diapsid reptiles are an extremely diverse group that contains a number of extinct kinds of reptile as well as snakes, lizards, turtles, the last surviving member of the ancient order Ryhnchocephalia – the tuatara, crocodiles, dinosaurs and birds.  The last three listed, crocodiles, dinosaurs and birds are of course archosaurs, and the Archosauria are characterised by a number of anatomical features including the two pairs of skull fenestrae.

For models and replicas of archosaurs and other prehistoric animals: Prehistoric Animal Models and Figures.

The holes in the skull probably evolved to permit larger muscle attachments for the jaws, giving these animals a stronger bite.  The mouth could also be opened wider, a definite advantage of you are having to bolt down lumps of flesh or to cram into your stomach large amounts of nutritionally poor vegetation.

To read our article about another feature of the Archosauria – tooth sockets: A Feature of the Archosauria (Part 1).

Visit the Everything Dinosaur website: Everything Dinosaur.

Examining Teeth in Sockets – Crocodilians (Archosauria)

Team members at Everything Dinosaur were given the opportunity to examine the skull of a large gharial recently.  The gharial (Gavialis gangeticus), has evolved a long, elongated snout and specialises in catching fish (piscivore).  These once widespread and diverse members of the Gavialidae are extremely rare in the wild.  They are restricted to a few fragmentary populations scattered amongst the river systems of the northern parts of the Indian sub-continent.  It is a member of the Archosauria clade.

Examining the Skull of a Large Gharial

Picture credit: Everything Dinosaur

Crocodilians are Members of the Archosauria Clade

The skull of this crocodilian portrays several characteristics that identifies it as a member of the Archosauria, the same clade of reptiles that includes dinosaurs, pterosaurs and birds.  The skull has a number of holes in it (fenestrae), these holes establish it as a member of the diapsid, one of three main groups of reptiles that can be distinguished from each other by the presence or absence of such fenestrae and their number.

Establishing shared characteristics between different species (synapomorphies), is the standard model for classifying organisms.   These shared characteristics, came from a shared, common ancestor.  Essentially, taxonomists are looking to identify similarities and differences.  The number of holes in the skull is one of the synapomorphies that establishes this gharial as a member of the archosaurs (ruling reptiles).

Teeth in Sockets

Another synapomorphy shared amongst the Archosauria, (although derived members of this group such as the birds have subsequently lost this trait), can be seen in the jaw.  The teeth of the gharial are set in sockets.  These sockets are termed alveoli (singular alveolus).  Being strongly anchored in a bony socket allows the tooth to withstand greater forces.  It is less likely to be lost during predation and feeding.  This enabled many of the early archosaurs to evolve powerful jaws, capable to tacking struggling prey or coping with tough, fibrous vegetation.  This evolutionary trait may help to explain their success.

For models and replicas of archosaurs and other prehistoric animals: Dinosaurs and Other Prehistoric Animal Models.

On the Skull of the Gharial – the Teeth Sockets can be Easily Seen

Picture credit: Everything Dinosaur

Visit the Everything Dinosaur website: Everything Dinosaur.