Note: Tehar has a taxonomic system somewhat different from the one in OTL. =otl is used to show what OTL clade is equivalent to that clade on Tehar. If =otl is not used, the clades are the same in two timelines.
Birds (Aves, =otl Theropoda) is the most diverse terrestrial vertebrate clade (typically considered a class) on Tehar, with over 13000 species inhabiting the planet's whole surface, except for deep oceans and some caves/subterranean ecosystems. Birds are a relatively young group of animals, having first evolved in Triassic and being closely related to another living class, gryphons (Gryphi, =otl Ornithischia) and an extinct class Anserotitania (=otl Sauropodomorpha), united together in a clade called dragons (Dracones, =otl Dinosauria). They are also more distantly related to suchians (Suchia, =otl Pseudosuchia).
Some characteristic features of birds are their, at least ancestrally, bipedal gait, light pneumatized skeletons and complex breathing system with air sacs inside their bodies; some traits, such as strict oviparity, feathers and endothermy, are shared with other dragons; finally, a common feature for most but the most basal birds today is complex feathers and ability to fly.
Historically, there were many different ways to classify birds, such as splitting birds into Pterygornithes, incorporating all winged birds, and Apterygornithes, incorporating the archaic wingless lineages; or dividing them into Odontognathae (toothed) and Anodontognathae (toothless). Externally, it was pretty well-understood that birds and gryphons are relatives, but what other groups do they have relations with has been a subject of debates for decades. Still, nowadays it is pretty well-known that birds (and gryphons) are suchian relatives, and internally, bird class has been divided into 6 living and many more extinct clades.
The most basal living avian clade is Euapterygornithes (=otl Ceratosauria). Wingless, toothed and long-tailed, these avians have branched off the whole avian tree all the way in the Triassic. Nowadays they are a very diverse group, including animals of different sizes, diets and anatomy, having underwent most of that evolutionary radiation relatively recently in the Paleogene. They inhabit Motutea, Kadalia, Tanah and Uzun.
Somewhat less basal than the euapterygornitheans are the motunuiavians, found predominately at Motunui but also at Motutea. These birds are also wingless, toothed and long-tailed, but they have much more rigid tails and are, in fact, closer to all other living bird groups than they are to euapterygornitheans. There is a relatively little number of their species nowadays, most of them predatory. The ancient ferocious regiavids of Cretaceous Uzun are their close relatives.
Third group of birds, enantiornitheans, is extraordinarily diverse. They have lost long tails and are typically volant, with feathery wings helping them stay in the air. However, they have teeth. After neognaths they are the most diverse birds on Tehar, though differences in their ontogenesis and social behaviour make them less prone to high diversification of species (most enantiornitheans, unlike most neognaths, grow slowly and occupy multiple niches as they age). Enantiornitheans are found worldwide.
The fourth, relatively small, avian group is Noctiraptora. While historically these toothed, volant birds have been considered a peculiar branch of enantiornitheans, they are nowadays seen to be closer to palaeognaths and neognaths and particularly close to an extinct lineage of aquatic Cretaceous birds, Palaeolari (=otl Ichthyornithes). Noctiraptorans are exclusively predatory and volant, and are more diverse at Libya and Uzun than any other continent.
Fifth bird group is small and includes almost exclusively secondarily flightless forms. The palaeognaths are edentulous, typically large and cursorial avians widespread on all continents, except for Motutea and Sagastan. They have some typical archaic features that have made them associated with enantiornitheans sometimes in the past, though nowadays they are well-understood to be neognath relatives.
Finally, the neognaths, the most common and diverse avian group on Tehar, inhabits the whole planet and includes a vast number of toothless, typically volant, birds of all shapes and sizes. From tiny songbirds of Uzun's temperate forests to giant flocks of seabirds at the shores of Qaria to terrifying bearbirds of Hatunwata, most birds on Tehar are neognaths.
Along with a lot of unusual mammals, Madagascar was also home to some of the largest birds to ever exist: the giant elephant birds.
Despite being located so close to mainland Africa, these enormous flightless ratites weren’t the closest relatives of ostriches as might be expected. Instead their closest living relatives are the kiwis of New Zealand, and they must have descended from flying ancestors that reached Madagascar across the Indian Ocean sometime during the early-to-mid Cenozoic.
Aepyornis maximus was one of the biggest of these big birds, standing around 3m tall (9′10″) and weighing over 500kg (1,100 lbs). Its eggs were equally massive, up to 34cm long (1'1″) and with a circumference of over 1m (3′3), making them the largest known eggs laid by any vertebrate.
Recent studies of the shape of its brain within its skull show that it had a good sense of smell but very poor eyesight -- possibly being near-blind -- suggesting that much like its kiwi relatives it was highly specialized for a nocturnal lifestyle.
There were several other species of elephant bird throughout Madagascar, and at least some of them appear to have successfully survived alongside humans for quite some time. Carbon dating of eggshells suggests they were still alive around 1000 years ago, and based on historical mentions they may have persisted as late as the 1600s before finally disappearing.
The Emu is a modern flightless dinosaur native to Australia. They are primarily herbivores, but also eat insects and other small arthropods for protein. It is the second tallest bird in the world, and they spend their days foraging, preening, and resting!
Time and Place: About 4 million years ago, in the Zanclean of the Pliocene
Heterorhea is known from the Monte Hermoso Formation of Buenos Aires, Argentina
Physical Description: Heterorhea is only known from some isolated foot bones which were very similar to those of the modern Rhea, but in general shorter and wider. This indicates that, if Heterorhea was indeed a Rhea (see below), it would have been similar to the living Rhea but a little thicker in general proportion. This is, of course, conjecture; but it’s the best one we’ve got, as the original fossil of this animal is lost. Like living Rheas, it probably would have been a shaggy, flightless dinosaur; with a long neck, thick legs, and small pointed beak.
Diet: Heterorhea was probably a vegetation, feeding on broad-leafed plants, fruits, seeds, and roots.
Behavior: Heterorhea probably behaved at least somewhat similar to living Rheas, fairly silent birds forming large flocks fleeing in zig-zag motions. They would probably make calls during the mating season, making somewhat loud calls in mating displays and then making soft sounds to chicks when laid. They were also probably polygamous. Other than that, though, we can’t really make a lot of statements about Heterorhea behavior.
Ecosystem: Heterorhea lived in a wet, lush grassland environment, which would occasionally flood with extensive amounts of water and mud based on the turn of the seasons. This was before the onset of the Ice Age, so it was during a time of somewhat warmer climate than what the later Rheas would face. Here, Heterorhea lived alongside many other animals - a variety of frogs, Ungulates, rodents and rabbits, Toxodonts, Macraucheniids, armadillo relatives, anteaters, Glyptodonts, Thylacosmilus, Racoons, opossums, and so many other mammals. As for contemporary dinosaurs, there were a variety of ducks, the other rhea Hinasuri, Tinamus like Nothura and Eudromia, and - of course - birds of prey like seriemas, condors, and the terror bird Mesembriornis. The latter would, of course, have been a major source of danger for Heterorhea.
Other: Heterorhea is, sadly, lost; this means we can’t actually compare the fossil of this dinosaur with other birds known from the region. Thus, though it was originally called a rhea, we can’t be certain that is what it is - since that assignment came before the age of phylogenetics and more objective classification.
~ By Meig Dickson
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