Aepyornis and the Elephant Birds of Madagascar

File:Aepyornis maximus 01 L.D..jpg
A front view reconstruction of Aepyornis.
Image Credit: Acrocynus, https://it.wikipedia.org/wiki/File:Aepyornis_maximus_01_L.D..jpg

While it seems like I already know a bit about prehistoric life, before each of these blog articles I make sure to do my research on the animal that I aim to talk about, as any blog writer should do regardless of their subject area. During my research I not only broaden my knowledge, but also gain an extra appreciation for the animal in question. In the case of todays subject, Aepyornis (Greek for “high bird”), more commonly known as the “Elephant Bird”, my research showed just how little I actually knew about it. Aepyornis was a much more fascinating animal than I had realised (not just “a big ostrich”), and in this blog I aim to put the spotlight on this underrated animal.

For starters there wasn’t just one “Elephant Bird”; there was a whole family of them! “Elephant Bird” is the common name given to a family of flightless, bipedal, ostrich-like herbivorous birds from Madagascar known as the Aepyornithae. The “Elephant Bird” name originates from tales of the “Roc”; a legendary giant bird spoken of by Arab traders and written about by the famous explorers Marco Polo (13th century) and Ibn Battuta (14th century). It was also one of the monsters that the adventurer Sinbad encountered in “The Arabian Nights” tales (first published in the 18th century). It was said to be so big that it could carry an elephant in its talons. Polo in all likelihood based his Roc description on accounts of large, lemur hunting Malagasy Crowned Eagles that lived on Madagascar until the 16th century. However reports from other travellers of massive eggs, which belonged to Aepyornis, became associated with the Roc, and so the Aepyornithae family became collectively known as “Elephant Birds”. The Aepyornithae belonged to a larger order of birds known as the Ratites. This is the same group that contains ostriches, emus and cassowaries. You may think that since the Elephant Birds lived on Madagascar their closest relatives would be African ostriches since Madagascar lies off the East African coast. However this is not the case. Their closest living relatives are actually kiwis; small flightless birds which have long, thin beaks, reduced eyesight and are also ratites. Kiwis live only on New Zealand, which is 7,000 miles east of Madagascar! So how are these two birds so closely related despite living so far apart? Well the theory is that around 60 million years ago the common ancestor of kiwi’s and Elephant Birds still possessed flight and flew to these two separate islands, establishing colonies. Then, over millions of years, the two islands drifted further apart from each other (out of flying range) and the two separated populations both evolved flightlessness, independently of one another.

Another result of living on an isolated island for much of their evolution, and with no large mammalian herbivores to compete with, is that the Elephant Birds could grow to massive sizes. Aepyornis was no different and was thought to have been the largest bird that ever lived until relatively recently. Originally it was believed that Aepyornis maximus could grow to heights of more than 3 metres and weigh up to 800kg. However a study in 2018 by Hansford & Turney showed that there were enough skeletal differences between these largest specimens and other Aepyornis for these large Aepyornis to be re-classified as a new member of the Aepyornithae family (alongside Aepyornis and another Elephant Bird named Mullerornis). It was given the rather striking name of Vorombe titan, which is a combination of Malagasy and Greek and translates to “big bird” (Vorombe = Malagasy for bird, titan = Greek for big). As a result the size estimates of Aepyornis is now considered to be a more modest 2.5 metres tall and 400-500kg in weight on average, which is still larger than any living bird! Another of Aepyornis’ (and other Elephant Birds’) claims to fame is their humongous eggs. At their biggest they measured 34cm long, had a circumference of a metre and weighed 15 kilos. That’s 150 times bigger than a chicken egg, larger than any dinosaur egg and the largest eggs of any animal ever. Imagine the fried egg you would get from that! It wouldn’t just be enough for your breakfast; it would be enough to feed your entire family for the whole day! Such huge eggs would have meant that Elephant Bird chicks would have been more highly developed compared to other birds and the lack of any large egg thieves (before humans arrived) meant that it would have been safer for Elephant Birds to lay these eggs.

An Aepyornis egg (the large one!) from Museo Capellini in Bologna, Italy.
Image Credit: Ghedoghedo, https://commons.m.wikimedia.org/wiki/File:Aepyornis_egg.JPG

Aepyornis held the ecological niche of “large herbivore” on Madagascar. Its diet consisted of fruit, grasses and leaves and Aepyornis used its strong neck and overall size to reach them, before biting off and swallowing chunks with its beak. Unlike a lot of other large herbivores recent research has suggested that Aepyornis was a mostly nocturnal animal. The evidence comes from another 2018 study (by Torres & Clarke) where Aepyornis braincases were examined with a CT scanner. This produced a 3D model that the researchers could manipulate and examine in detail. Using this they discovered that Aepyornis had enhanced olfactory lobes (the part of the brain that processes smells) and reduced optic lobes (the part of the brain that processes vision). This is a similar, albeit less extreme, version of the brain structure of kiwis; which are nocturnal birds with limited vision and a reliance on smell to sense their environment. Furthermore Torres & Clarke also showed that different Aepyornis species had slightly different sensory lobes. You see there are two recognised species of Aepyornis; Aepyornis maximus (the larger, forest dwelling one) and Aepyornis hildebranti (the smaller, plains dwelling one). In A.maximus the olfactory lobes were proportionally larger, and the optic lobes proportionally smaller, than in A.hildebranti. This is presumably because A.maximus lived in dense rainforests, where eyesight is less useful due to the dense trees, while A.hildebranti lived in the open plains where the lack of dense trees meant they could see greater distances.

Aepyornis shared its Madagascan home with a menagerie of recognisable animals still alive today, such as Ring-tailed lemurs, Fossas and Chameleons. However it also lived alongside some strange animals that are no longer around. These included Archaeoindris, a giant lemur that was the size of a Silverback gorilla, the aforementioned Malagasy crowned eagle which modern lemurs still possess an innate fear of even though it is now extinct, and giant tortoises similar in size and lifestyle to the modern day Galapagos giant tortoise. So once upon a time Madagascar had an even greater diversity of life than it does now. However there are no Elephant Birds, giant lemurs, huge tortoises or giant eagles anymore. This is thought to have been mainly due to change in climate, which lead to changes in food availability. The actions of humans are also commonly linked to the disappearance of many Madagascan animals. However they may not have played as big of a role as previously thought. Yet another 2018 study (2018 should be renamed “Year of the Elephant Bird” due to all the studies carried out that year!) dated Elephant Bird bones that showed distinctive cut marks made by human tools to 10,500 years ago, the end of the Pleistocene period and start of the Holocene period. This was a whole 8,000 years earlier than humans had previously been thought to have reached Madagascar. Since Aepyornis and other Elephant Birds became extinct sometime between the 10th-12th Centuries (though sightings had been reported to as late as the 17th century) this means that humans co-existed with the birds for longer than previously thought. So they couldn’t have quickly hunted them to extinction as had been previously assumed. However this doesn’t mean that Aepyornis wasn’t a target for humans or that human activity wouldn’t have affected their numbers. For one the sheer size of both the animal and especially its eggs (which could be quickly poached from Aepyornis nests) would have been an attractive prospect for human hunters. For another humans were converting the Madagascan forests and plains into farmland, destroying Aepyornis’ habitat, and domesticated chickens and guinea fowl brought to Madagascar may have passed on bird related diseases to Aepyornis, which it had no immunity to.

Aepyornis skull from a skeleton at the Muséum national d’Histoire naturelle in Paris, France
Image Credit: LadyofHats, https://zh.m.wikipedia.org/wiki/File:Aepyornis_skull.JPG

So overall, Aepyornis was a truly splendid animal, with a much more varied and detailed history and lifestyle than at first glance. The Elephant Birds are reminiscent of a time 65 million years ago when the close relatives of birds ruled the world. The dinosaurs were long gone, but in this little corner of the world Aepyornis and its family carried on their legacy.

References/Further Reading

Torres & Clarke 2018: a study of the braincases of the Elephant Bird, and what it tells us about their noctournalism

Christopher R. Torres and Julia A. Clarke 2018, Nocturnal giants: evolution of the sensory ecology in elephant birds and other palaeognaths inferred from digital brain reconstructions, Proc. R. Soc. B.28520181540, http://doi.org/10.1098/rspb.2018.1540

Hansford & Turney 2018: a study on the diversity of the Elephant Bird (Aepyornithae) family, showing that the largest Aepyornis were actually a different species of Elephant Bird: Vorombe Titan

James P. Hansford and Samuel T. Turvey 2018, Unexpected diversity within the extinct elephant birds (Aves: Aepyornithidae) and a new identity for the world’s largest bird, R. Soc. open sci.5181295, http://doi.org/10.1098/rsos.181295

Hansford et. al. 2018: a study on Elephant Bird bones with human made cut marks dating from as far back as 10,500 years ago

James Hansford, Patricia C. Wright, Armand Rasoamiaramanana, Ventura R. Pérez, Laurie R. Godfrey, David Errickson, Tim Thompson, Samuel T. Turvey. Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna. Science Advances, 2018; 4 (9): eaat6925 DOI: 10.1126/sciadv.aat6925

An American Museum of Natural History page about the association of the Roc and Aepyornis, part of their “Mythic Creatures” exhibition

“Strike from the Sky”, Mythic Creatures Exhibition, American Museum of Natural History, https://www.amnh.org/exhibitions/mythic-creatures/air/strike-from-the-sky

A Smithsonian magazine article about the giant eggs of the Elephant Birds

Katz, Bridget, “Giant, Intact Egg of the Extinct Elephant Bird Found in Buffalo Museum”, Smithsonian Magazine, April 23rd, 2018, https://www.smithsonianmag.com/smart-news/giant-intact-egg-extinct-elephant-bird-found-buffalo-museum-180968850/

Bolton, Houston & Monaghan 1992: A study on the link between large eggs and survivability of baby birds

Bolton, M., Houston, D., & Monaghan, P. (1992). Nutritional Constraints on Egg Formation in the Lesser Black-Backed Gull: An Experimental Study. Journal of Animal Ecology, 61(3), 521-532. doi:10.2307/5607

Yutyrannus: The Feathered Tyrant

Image result for yutyrannus
Reconstruction of Yutyrannus huali, Feathers and all!
Image Credit: Tomopteryx, https://commons.wikimedia.org/wiki/File:Yutyrannus_huali.png

Tyrannosaurs are arguably the most famous members of the great dinosaur pantheon. Their traditional look has been set in stone in the public eye for decades, being immortalised in various media, of a giant scaly lizard with tiny arms and a massive head full of sharp, banana shaped teeth. However what if I were to tell you that this picture isn’t completely accurate, and that at least some tyrannosaurs were in fact a lot more on the soft and fluffy side! While it’s still being debated to this day whether the mighty Tyrannosaurus Rex had feathers (a story for another blog!), there was another tyrannosaur that not only possessed feathers, but was completely covered in them! Revealed to the world in 2012 Yutyrannus huali (meaning “Beautiful Feathered Tyrant” in a mix of Mandarin and Latin) shaked pre-existing ideas about Tyrannosaurs to the core.

Yutyrannus was discovered in the Yixian formation, in the Liaoning Province of China by a Chinese palaeontologist named professor Xing Xu. This particular corner of the world is extremely rich in dinosaur fossils, mostly dating to the Early Cretaceous period (125 million years ago). A large majority of the feathered dinosaur finds in the last few decades originated from this area. Xu is a big name in the world of contemporary palaeontology as described and named a lot of these feathered dinos, such as the “four winged” Microraptor and another feathered tyrannosaur called Dilong. The Yutyrannus fossils discovered by Xu and his team consisted of an adult and two juveniles, all of them almost complete. This is remarkable as tyrannosaurs are often only known from incomplete fossils. So in this case we have a vividly detailed picture of this particular animal.

One of the most surprising observations about Yutyrannus is not only that it had feathers, but that this was a big animal. Previously other known feathered tyrannosaurs, such as Dilong and Guanlong (both also discovered in China), were relatively small; ranging around the sizes as modern big cats. However Yutyrannus bucked this trend by growing up to 9 metres long, 3 metres tall and weighing up to 1 and a half tonnes. This makes Yutyrannus the largest animal with direct definitive evidence of feathers ever discovered. While other dinosaurs like Therizinosaurus and Gigantoraptor are likely to have had feathers, there’s been no direct evidence found yet, so Yutyrannus keeps the crown for now. Unlike other large tyrannosaurs Yutyrannus shares many features with other early tyrannosaurs, such as possessing three fingers instead of two and a lack of a specialised weight-bearing middle toe (used by later tyrannosaurs to support their weight). By comparing its anatomy with other tyrannosaurs it was also deduced that Yutyrannus was not a direct ancestor to T-Rex, but instead belonged to a family of tyrannosaurs that split off during the Early Cretaceous, meaning that Yutyrannus was essentially T-Rexs great great uncle. Unlike later Tyrannosaurs Yutyrannus also possessed a small, midline crest at the end of its snout. This could have been used to attract a mate or to signal other individuals, saying for example “I’m the biggest and baddest of the Yutyrannus! Keep away!”. As the fossils were of an adult and two juveniles this could potentially be a family group. It has been theorised that tyrannosaurs may have lived in groups, so perhaps this find represents the sad end of a mum or dad raising its offspring.

Size comparison between a full grown Yutyrannus and a fully grown human. As you can see this was certainly a large feathered animal!
Image Credit: Conty, https://en.m.wikipedia.org/wiki/File:Yutyrannus_SIZE.png

The feathers themselves have been found preserved in patches across the whole body of all 3 fossils. In life they were relatively simple “proto-feathers”, consisting of long simple filament like structures. These filaments would have intertwined to produce a fluffy down; somewhere between the down on a baby chicken and the longer, fibrous feathers of an emu. The primary function is likely to have been to keep Yutyrannus warm. A study by Amiot et. al. in 2011 looked at oxygen isotope compositions found in reptile fossils from East Asia. These seem to indicate that at the place and time where Yutyrannus lived was a relatively cold, compared to the hothouse that was the rest of the Mesozoic, so a feathery coat would have helped to keep an active hunter like Yutyrannus at the right temperature. Other possible usages of this coat of feathers could have been to assist with attracting mates, as has been speculated to have been the case in other feathered dinosaurs (e.g. Caudipteryx), and any shed feathers could have been used to line their nests, as it is employed by modern birds. It has even been suggested that the colour of the feathered coat would have helped Yutyrannus camouflage itself against its surroundings, a trick that is employed by most predators today. Some reconstructions have given Yutyrannus a fully white coat to blend in with a snowy background (like a polar bear). While this is a neat bit of speculation, it can’t be proven until any melanosomes that may be preserved are examined. If so then palaeontologists would be able to discover the colour of a tyrannosaur for the first time!

An illustration showing a group of Yutyrannus hunting a juvenile Dongbeititan
Image Credit: PaleoEquii, https://commons.m.wikimedia.org/wiki/File:Dongbeititan_and_Yutyrannus.jpg

A lot of criticism of these feathered dinosaurs, and particularly with ideas about feathers existing on dinosaurs that were previously thought to be scaly, is that it makes dinosaurs “less cool looking” and more like giant turkeys. However I think that Yutyrannus is an excellent example of how feathers can enhance the interest in dinosaurs, providing another side to how we see these great lizards. An animal like this would certainly make a cute pet when it’s young. However, like pet owners who buy young tiger cubs, it’ll grow up over the years into a giant unmanageable carnivore, leaving the owner thinking “I REALLY didn’t think this through!”

References/Further Reading

Xu et. al. 2012 paper describing the 3 complete skeletons of Yutyrannus, including the description of its feathers

Xu, X., Wang, K., Zhang, K. et al. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature 484, 92–95 (2012). https://doi.org/10.1038/nature10906

American Museum of Natural History blog on getting to know Yutyrannus

AMNH, “Get to Know a Dino: Yutyrannus huali”, American Museum of Natural History, Apr. 11, 2016, amnh.org/explore/news-blogs/on-exhibit-posts/get-to-know-a-dino-yutyrannus-huali

Amiot et. al. 2011 paper on oxygen isotope compositions in fossils from the Early Cretaceous East Asia

Amiot, Romain et al. “Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates.” Proceedings of the National Academy of Sciences of the United States of America vol. 108,13 (2011): 5179-83. doi:10.1073/pnas.1011369108

A National Geographic article, written by Cliff Tarpy, about the fossils of Liaoning

Tarpy, Cliff, “Liaoning Province—China’s Extraordinary Fossil Site”, National Geographic, nationalgeographic.com/science/prehistoric-world/china-fossils/