Dinosaurs and their Descendents 3 - Feathered Non-Birds!

` In DatD 1, I explained some of the reasons why birds are considered to be a type of maniraptor. (If you've read it, you'd definitely know what that is.) In DatD 2, I basically explained why artists have been depicting the nonavian (non-bird) dinosaurs with feathers for so long. Here, I'll describe exactly what evolutionary theory has been predicting for decades - fossil specimens of non-avian dinosaurs with feathers!
` (As time goes on, I'll announce new species as they are discovered.)

... ,--=@ + ...............< "Look! We do have feathers!"..........
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............... zz . >>>? 7) 5 ...................................``````` ``` ``...
.................~$j> ^^/%y ..........................................................
................../# ........:4 .............................................................
.................^M..........9 ...........................................................
........................~^JfZ .............................................................

(` In the next part, I will go into how feathers develop and how they could have evolved.)

` I've talked about the reasons why ground-living dinosaurs would need to evolve feathers... and of course we know they did: Due to the increasing amount of well-preserved coelurosaur fossils, there have been many discoveries of skin, muscle, veins, internal organs, eggs, and indeed, feathers (depending on the conditions).
` There is as solid proof of feathers as you can get in science from looking directly at this material. I know that some... uh... interesting scientists say that the structures found are not really feathers, or that they are feathers but that they somehow came from birds, or that the animals in question are birds that just look like other dinosaurs - much of this is because they haven't actually studied the specimens themselves and/or looked at all relevant data.
` It's unanimous among mainstream scientists (who have considered all the evidence) that feathers were evidently common among the smaller coelurosaurs, and possibly all theropods. Several widely-related species have been discovered with such coverings.

` But why? Why think that a lot more dinosaurs were feathered when only a handful were discovered? Think of it this way; if endothermy (warm-bloodedness) was common among dinosaurs, small, featherless forms would usually be at a disadvantage.
` This is evident in the fact that, say, carnivores are all warm-blooded mammals. All felids (cats) have fur. All canids (dogs) have fur. All ursids (bears) have fur. So do all hyenas, weasels, skunks, raccoons, civets, seals, sea lions and otters. Walruses, however, are bald, because in their case, blubber seems to be the optimum type of insulation.
` So, another line of logic is this: If we know that the ocelot, the maned wolf, the palm civet, the spectacled bear, the spotted hyena, the sea otter and the ringed seal all have fur... then it would follow that other carnivores would as well, and not just because they are warm-blooded. Their relatedness tells us this too: If you know that all these carnivores are furred, it is logical to suppose that their common ancestor - the first carnivore - passed this trait down to all its descendents.
` Therefore; if Dilong, Beipiaosaurus, Sinosauropteryx, Caudipteryx, Shuvuuia, Microraptor, Sinornithosaurus, and the dinosaur we'll call Unnamed (for now) all had feathers, they (and their relatives) must have inherited them through a long line of dinosaurs back to possibly the first coelurosaur, or perhaps the first theropod, or the first dinosaur ever.

` We'll look at another copy of Dr. Prum's cladogram from DatD 1 again:

(From other................................................/....Compsognathids
theropods).............,------------------------------|.like *Sinosauropteryx
|.........................|........................................................................
|........................|..............................._______|.Alvarezaurids,
|........................|.............................|.............|....like *Shuvuuia
|......................./............_________|.........................................
`-Coelurosaurs......../...................|...,--------|Ornithomimids
|........................../....................|__|....................................
|........................./...........................|_|..Therizinosaurids,
|......................./................................|.like *Beipiaosaurus
Maniraptors../...................................................................
|...........___________________|Tyrannosaurids,
|........./..................................................like *Dilong
|........|.....................................................................
|.......|..........._______________|.....Oviraptorids,
`-------|.......|................................|.like #Caudipteryx
|......|..............................................................
|......|..............,---------------------|Troodontids
`-----|...........|..................................................
|...........|.............../.Dromaeosaurs, like
|...........|..............|.....*Sinornithosaurus,
|.........,-`-----------|.......*Microraptor, and
`-------|.................|____.......*(Unnamed)
|....................................................
|................,--------#Archaeopteryx
|________|..................................
|....,--#Confuciusornis
|__|............................
|.#Enantiornithines
`--|............................
`------#Euornithes
like modern birds

` As you can see, all of these dinosaurs are widely spread in the same area of the 'family tree' of coelurosaurs. As you may remember, the * indicates that a species had a primitive type of feather not found today, lacking the tiny barbules and hooklets found in birds.
` The # means that feathers with the fine details that birds have can be seen (most of them, so far, are actually birds). To read more about these 'modern' feathers, go to DatD 4. However, it is interesting to know that at least some of the larger maniraptors evidently ceased to grow feathers, as large warm-blooded animals typically have trouble getting rid of their body heat.

` So... what are these species from the cladogram like, and what do we know of their feathers? Just keep reading:

Sinosauropteryx prima - (SY-no-sawr-OP-ter-icks* PRY-ma)
[Greek, Latin] (f) 'primitive Chinese wing-lizard'
` Place: Liaoning, China lake bed.
` Time: Early Cretaceous, as determined by radiocarbon dating as well as other animals and pollen from the Early Cretaceous.

` At first, thought to be a primitive bird, Sinosauropteryx is now known to be similar to Compsognathus - which was itself once confused with the primitive bird, Archaeopteryx! Surprisingly, it wasn't even a maniraptor, though many of the differences are subtle.
` In shape, the animal had an amazingly long tail - almost twice as long as the rest of its body - with 64 tail vertebrae!
` Its arms are only about 30% as long as its legs, though its 'thumb' is both thicker than the radius or ulna (bones in the forearm) and is tipped with an enormous claw.
` So far as I know, three of them have been discovered, and between them have been found various structures inside the body, as well as a dark 'halo' around it that clearly shows a covering similar to bird feathers. You don't see that every day!
` Under magnification, the feathers appear to be more primitive than that of modern birds; they have barbs like modern feathers, though they lack the barbules and hooklets of birds. This is why they are referred to as 'protofeathers' - they have no exact modern equivalent.
` They are coarser than the hair of small mammals and range in length from 5 to 40 mm, preserved quite well on the neck, back and tail, as well as patches on the skull, arms, legs, and ribcage. What is most clear about them is that they are not collagen fibers in the skin, but actual filaments that once covered it.
` In addition, the first, smallest specimen also appears to show remains of internal organs, and the third specimen had the remains of a mammal in its gut. Even more remarkable, aside from clear evidence that it had just eaten a small lizard, the second specimen actually had a pair of unlaid eggs in its oviducts!


Shuvuuia deserti - (shu-VOO-ee-a * dee-SER-tie)
[Mongolian] (f) 'bird of the desert'
Place: Mongolia
Time: I don't remember, I'm doing this from memory.

` This maniraptor was a large-eyed, one-fingered wonder like its close relative, Mononykus (mo-NON-i-kus - 'one claw'), and some parts of it have even been mistaken for its cousin. Shuvuuia's skull was only about 3.2 inches long, and had many amazingly birdlike features, including tiny, unserrated teeth both in the front part of the upper jaws and along a continuous groove in the dentary bone of the lower jaw.
` As far as 'feathers' go, it appears to have only small, hollow shaftlike structures coming out of the skin which appear to be similar to known feathers. The remains of these do contain the decay products of beta keratin - which are what feathers are made of - and not alpha keratin, which is found in scales but not feathers.


Ornithomimosaurs ('bird mimic reptiles') are what some call 'ostrich dinosaurs', because they had long legs, and small - usually beaked - heads on the ends of long necks. They probably looked somewhat like an emu with clawed arms and a tail.
` Though none have been found with feathers so far as I know, a primitive, 220-toothed species called Pelicanimimus was found with wrinkled skin on its head - which looked as if it might be some type of unusual feathers at first. It is named for what appears to be a dewlap or pouch like a pelican's on its throat.
` Just so you know, this does not mean it wasn't feathered: Some conditions favor the preservation of some internal organs, some favor the preservation of skin, and others favor the preservation of beta keratin integuments, so even though the animal's skin was preserved, the feathers may have decomposed without a trace.


Beipiaosaurus inexpectus - (bey-pyow-SAWR-us * in-ek-SPEK-tus)
[Chinese, Greek] (m) 'unexpected reptile of Beipiao'
Place: Liaoning, China lake bed.
Time: I'm not sure, probably Early Cretaceous.

` Beipiaosaurus was found with the remains of feathery filaments between 50 and 70mm long near the arms, legs, and shoulders. It would appear that this animal is one of the therizinosaurs - formerly called segnosaurs - a group of huge, bulky maniraptors which used all four toes for walking on, and had huge claws on their hands.
` Though they had the typical maniraptorian type of skull, pelvis and arm bones, such as the semilunate ('half-moon') carpal, therizinosaurs were very unusual for any theropod in that they seem to have been specialized for eating plants. (Similarly, the giant panda, clearly a carnivore, eats mainly giant grass stalks.)
` One can determine this by observing that their skulls, though having the same basic structure as their meat-eating relatives, were quite small with leaf-shaped teeth. This species, however, was only a little longer than seven feet and appeared to be more birdlike and less specialized than later relatives: Its skull was larger, it walked on three toes, it had shorter, more bulbous tooth crowns, a longer hand, an ilium shaped more similar to that of a dromaeosaur's, a crest on the tibia, and compressed foot bones.
` In 1999, Xu et al described the animal's feathers in Nature:

"The filamentous structures in Beipiaosaurus are similar to, but longer than, those of the compsognathid Sinosauropteryx. They are perpendicular to the limb bones, and are unlikely to [be] muscle fibers or frayed collagen. Their presence in both therizinosaurs and compsognathids indicates that there may be a broader distribution of similar structures in theropod dinosaurs... The absence of such structures in most theropod fossils is probably attributable to the lack of such ideal preservation as is found in the Yixian Formation. This again indicates that feathers preceded flight, because both therizinosaurs and compsognathids apparently could not fly and did not descend from flying animals."

Dilong paradoxus - (DEE[4]-long[2] * par-a-DOX-us)
[Chinese, Latin] (m) 'paradoxical Ti-lung' (a type of dragon)
Place: Liaoning, China
Time: Around the beginning of the Cretaceous Period, as I recall.

` Another valuable find, comprised of four separate specimens, Dilong was a much smaller, fuzzier relative of T. rex. While Tyrannosaurus is only known to have scales and scutes, this is probably because it was large enough that it actually had problems losing body heat, not retaining it, much like elephants, hippos and rhinos.
` Dilong, however, was only five feet long, and so the clear impressions of branched filaments (up to 2 cm) found with the skeletal remains are not that surprising. It also had more birdlike features than other tyrannosaurs, and as the earliest tyrannosauroid known, it was the least specialized.
` Its skull was rather like that of other tyrannosaurs, with fused nasal bones - even in the young - as well as teeth characteristic of the group. The rest of the skeleton is more like that of other coelurosaurs - for example, the arms are longer and bear three fingers instead of two, though the third hand-bone is very slender.


Caudipteryx zoui - (kaw-DIP-ter-icks # DZOH-eye)
[Latin, Greek] (f) '(Vice Premier) Zou's tail-feather'
Place: Liaoning, China (Chaomidianzi Formation)
Time: Early Cretaceous

` This dinosaur may be recognized as a distant relative of Oviraptor ('egg stealer') - a dinosaur which has since been found caught dead while clearly incubating the type of eggs it was once thought to have been eating!
` Caudipteryx is named for its fan of large, symmetrical contour feathers on the end of its short tail (which was only a quarter of its body length), rather like a turkey, which it resembled in size.
` It also had the same type of feathers on its arms - these weren't flight feathers, mind you, although the arm probably looked like some kind of wing. Unlike protofeathers, these did have barbules, creating their distinctive weblike vane as you see in birds. As for the rest of its body, Caudipteryx was down-covered.
` These feathers are so much like those of birds, in fact, that Drs. Feducci and Martin, (who are vehemently against the very idea that dinosaurs like Oviraptor could have had feathers), actually admit that Caudipteryx undeniably does have feathers exactly like those of birds! However, they also say that Caudipteryx is an actual bird, and of course, have not been able to present relevant data to back this up.
` In fact, the evidence is very much against this - many small details tell us that it is not a bird: Its pelvis lacks a posterodorsal process; its orbit (eye-opening) has a bar of bone behind it; its foot-bones are not fused; its first toe is not turned around backwards - as well as a bunch of other small things - way too many of them. It was not like a flightless Archaeopteryx - it was an oviraptorosaur!
` Also of note, Caudipteryx was originally assigned to Protarchaeopteryx, though now multiple specimens are known and it is clear that they are not the same. The fact that it had but two teeth at the tip of its upper jaw (probably covered partly in beak), a fairly short tail (only 22 vertebrae), shorter arms with large feathers attached to the second finger, and the fact that it apparently had a gizzard (probably for grinding up plants) are some of the major differences.


(Bonus species!)

Protarchaeopteryx robusta - (PRO-tar-kee-OP-ter-icks # ro-BUST-a)
[Greek] (f) 'robust first ancient-wing'
Place: China
Time: Early Cretaceous

` Protarchaeopteryx, I suppose, may not have been placed in Prum's cladogram because it is difficult to place it in the 'family tree', though it so far seems to be another Oviraptor-like dinosaur. The name implies this animal was 'the first Archaeopteryx,' though it actually lived afterward.
` It was, however, less birdlike, with strong back legs for running, unfused foot bones, a non-reversed first toe, and a long, 28-vertebra tail.
` However, like Archaeopteryx, it had other features such as a wishbone, and its teeth were shaped similarly, though serrated. And of course, I mention this animal because it also had feathers.
` In Nature, Qiang et al describes them in detail:

` "A clump of at least six plumulaceous [down] feathers is preserved anterior to the chest, with some showing well-developed vanes. Evenly distributed plumulaceous feathers up to 27mm long are associated with[]ten proximal caudal vertebrae. Tw[en]ty-millimetre plumulaceous feathers are preserved along the lateral side of the right femur and the proximal end of the left femur.
` "Parts of more than 12 retrices are preserved attached to the distal caudals. [O]ne of the symmetrical tail feathers extends 132mm from the closest tail vertebrae, and has a long tapering rachis with a basal diameter of 1.5mm. The well-formed pennaceous vanes of Protarchaeopteryx show that barbules were present.
` "The vane is 5.3mm wide on either side of the rachis. At midshaft, 5 barbs come off the rachis every 5mm (compared with 6 in Archaeopteryx), and individual barbs are 15mm long."

Troodontids ('wounding teeth') were similar to deinonychosaurs, yet were more delicately built with larger brains and smaller killing claws. So far, none have been found with feathers, though there are specimens of 'sleeping' troodontids like Mei long ('soundly-sleeping-dragon') which have been found in the same pose as a duck roosting with its head under its wing, the tail curling around the body.
` This shows the animals huddled, probably burying their noses in any feathers they may have had, to keep their body heat from leaking out. It seems they had been killed by poisonous gases from a nearby volcano (before they could wake up) and buried in ash. Also of interest, one troodontid has been found with a pair of birdlike, hard-shelled eggs unlaid in its oviducts.


Sinornithosaurus millenii - (SINE-or-nith-o-SAWR-us * mi-LEN-ee-eye)
[Greek] (m) 'Chinese bird-lizard of the millenium'
Place: Liaoning, China (Yixian Formation)
Time: Early Cretaceous

` This small dinosaur is well-known for such features as its extremely long arms (80% the length of the legs) which were capable of a similar range of motion used by birds; it could rotate its forelimbs upward and to the sides.
` Its hindlimbs had a slashing claw like that of other dromaeosaurs, and a reversed pubis similar in shape to Archaeopteryx's. Also birdlike were the costal facets on the sternum, which suggest that the ribs had hinged sternocostal joints: This means it may have breathed in a similar way to birds.
` Of course, Sinornithosaurus is also known for its feathery coat, as one was preserved in a Yixian Formation lake bed. These structures were quite primitive 'protofeathers' up to about 40 mm long around parts of the skeleton, similar to that of other dinosaurs preserved in this area. The abstract of Xu and team's article in Nature reads:

` "...Here we report the best represented and probably the earliest dromaeosaurid yet discovered, Sinornithosaurus millenii gen. et. sp. nov., from Sihetun, the famous Mesozoic fish-dinosaur-bird locality in China.... Phylogenetic analysis indicates that, among known theropods with integumentary filaments or feathers, Dromaeosauridae is the most bird-like, and is more closely related to birds than is Troodontidae."

` Xu et al describe the animal's fuzzy covering:

` "The integumental structures of Sinornithosaurus are compound structures composed of multiple filaments with two types of branched structure. First, the tufts of filaments joined at their bases are identical in structure to avian natal down feathers in which multiple filamentous barbs are basally fused to a single calamus..."

` In other words, yes, down feathers, which have barbs coming out of a quill (or calamus).

` "Second, the serial branching of filaments along a central shaft is identical in structure to the barbs and rachis of a pennaceous feather, and is also unique to avian feathers. The integumental structures of Sinornithosaurus are different from most modern avian feathers in their apparent lack of barbules. Thus, Sinornithosaurus appendages could not have formed a closed, pennaceous vane."

` In other words, it clearly had what can be called both down and contour ('adult') versions of 'protofeathers.'


Microraptor zhaoianus - (MY-cro-rap-tor * JOW-ee-ae-nus)
[Greek, Latin] (m) 'Zhou (Xijin)'s small robber' = ?Cryptovolans pauli
Place: Liaoning, China
Time: Early Cretaceous

` Microraptor (as well as another find also called Cryptovolans) is what could be called a 'tiny, biplane terror', as this 15-inch long dinosaur had flight feathers on both its arms and legs.
` Being a relatively primitive dromaeosaur, it is less specialized than later ones and more birdlike: The rear teeth are constricted ('waisted'), and, unlike in its later relatives, are largely unserrated. The front teeth, as in birds, are not serrated at all. As for the tail, it is shorter than that of other dromaeosaurs, with larger fused vertebrae where the pelvis connects, and an ischium (pelvic-bone) more similar to that of the primitive bird Rahonavis.
` Even before the flight feathers were found, it was known to have patches of feather-like integument and thought to have climbed trees, which its curved, gripping claws and more backwards-pointing first toe seemed to be more suited for.
` The type specimen of this animal was actually the tail of 'Archaeoraptor', which was actually two fossils of similar size that a poor Chinese villager had glued together in the desparate hope of selling a 'complete' specimen of something on the black market - something he could have gotten killed for!
` Scientists didn't realize this at first, as they had never seen bones exactly like these before, and the press went to town before they could even scan the thing. It turned out, at least, to be a 'happy accident', as two new animals - Microraptor and Yanornis, a bird - were discovered from that incident.
` Today, the best of six more recent specimens show the wing-feathers. Xu et al wrote in Nature:

` "Large patches of integuments are preserved in situ around the skeleton, and the pattern of preservation is similar to that of early birds from the same locality. Integumentary structures are best preserved near the femur, where they run almost perpendicular to the bone. They are long (average 25-30mm) narrow, and have a feather-like contour, whereas those along the tibia and in the hip area are shorter. Some impressions of the integuments contain a structure similar to that of a rachis, suggesting that true feathers may have been present..."

` Today, it is thought that Microraptor could have glided with these 'four wings', which appear to employ asymmetrical feathers for flying. As the legs could not have sprawled out to the sides, it appears that the feet were positioned below the arms and the feathers sprouting from them formed a sort of 'slanted airfoil' below the wings.


(Unnamed in cladogram) I am assuming this refers to BPM 1 3-13 and/or possibly at that point NGMC 91.

` These animals were both dromaeosaurs, with teeth similar to those of Sinornithosaurus. Ji Qiang et al describe the animals in Nature:

` "In NGMC 91 integumentary filaments are distributed across the entire skull, body, limbs and tail, except for the distal hindlimbs. Unlike Sinosauropteryx, the structure and distribution of filaments are heterogenous. [Meaning more than one kind.] There are three basic types... single fibers, long 'sprays' of fibres that resemble the plumulaceous [downy] feathers of Protarchaeopteryx, and the fibers oriented around a central axis in a herringbone pattern that resembles the remiges [tail feathers] of Caudipteryx."
` "BPM 1 3-13 can be unequivocally referred to the Dromaeosauridae on the basis of derived characters, including elongate prezygapophyses and chevrons that span several vertebrae in the tail [which are what make it especially stiff], a retroverted [backwards-pointing] pubis, and a modified second pedal digit [the 'slashing' claw].... The feathers of BPM 1 3-13 are structurally identical to those of modern birds, indicating not only that modern feathers must have evolved in dinosaurs before the emergence of birds and flight, but also that the feather-like structures present in many other non-avian theropods are homologous [meaning the same thing, not just appearing to be] with feathers."

` An April 2001 press release from the American Museum of Natural History said of BPM,

'Its head and tail are covered with downy fibers. Other parts of its body sprout tufts or sprays of filaments resembling primitive feathers, and the backs of its arms are adorned with branched structures like the barbs of a modern bird feather...' 'The detail on the newly discovered dromaeosaur is so fine that it allows scientists to see how the primitive feathers were attached to the dinosaur's body.'

` At the AMNH's website, you can see lots of closeups of the feathers! Just click on the various images at the bottom of that page to view them.


Arcaheopteryx lithographica - (ark-ee-OP-ter-icks # lith-o-GRAF-i-ka)
[Greek] (f) 'ancient wing of the lithographic slate'
Place: Southern Germany
Time: Late Jurassic, 150 my ago.

` This primitive, crow-sized bird was found pressed between slabs of Jurassic-aged slate. The name Archaeopteryx actually comes from a feather first mentioned by Von Meyer in a letter in August, 1861. He did not apply this name, however, until September, at which time a 'feather-bearing animal' had been found in the same quarry. His German colleague J. A. Wagner described the animal also in 1861, proposing the name Griphosaurus ('enigma reptile'), although he had only seen a very detailed drawing and not the specimen itself.
` In 1863, Sir Richard Owen bought the feathered fossil skeleton and identified it as a toothed, long-tailed bird, adopting Von Meyer's name for the genus, Archaeopteryx. He proposed macrura (mak-ROO-ra - 'long tail') for a new species name, which, in time, was discarded. Today, this original Archaeopteryx is referred to as the 'London specimen', and there are six more to date!
` As for the creature itself, the 'true' feathers on Archaeopteryx's wings and tail were asymmetrical - just like those of modern flying birds - and with its large wishbone, it was obviously built for some level of powered flight. It would appear that the animal could fly rather like today's birds, although probably clumsily, as it did not have the alula ('bastard wing') of later-evolved birds.
` Interestingly, the Berlin specimen, the only one known to have body contour feathers, shows faint impressions of long wing-like feathers 2-3 cm long on the legs as well. They were quite faint before, but are quite visible with sensitive microscopic equipment. This suggests that Archaeopteryx may have evolved through a four-winged stage somewhat along the lines of Microraptor.
` Also suited for flight was Archaeopteryx's brain, which wasn't quite as big as that of modern birds, though it had a large visual cortex. The structure of its inner ears actually fits perfectly within the normal range of size and shape of modern birds, which tells us that it probably had a comparable sense of orienting itself.
` The feathered tail was rather more reduced than in most other maniraptors, having only 22 vertebrae, and its teeth were conspicuously unserrated like those of other birds. Archaeopteryx also had a hyperextendable second toe like the dromaeosaurs (to which it is most closely related). The first toe was turned backwards, and - though a bit too high on the foot to be optimal - was probably prehensile. Also, while other dinosaurs had movable skull-bones, Archaeopteryx also seems to have been able to move its top jaw up and down like modern birds do, though not as extensively.


Confuciusornis sanctus - (kon-FYOO-shus-OR-nis # SANG-tus)
[Greek, Latin](m) 'Confucius' sacred bird')
Place: Liaoning, China.
Time: Early Cretaceous, 120 my ago

` Many tens of specimens (I believe over a hundred so far) of this bird have been found in Liaoning, so it is an understatement to say that this genus is well-known. Apparently, they were a shore bird that frequently fell into the water, the females having a rather short, rounded fan of tail feathers, while two of the male's were very long and spoon-shaped, much like the ones some modern birds have. What really sets this bird apart from others is that it is the earliest bird known to have a toothless, horn-sheathed beak like modern birds!
` And yet... it is not thought to have evolved into modern birds! It was just similar.

` There are also many other species of primitive birds, such as Jeholornis prima - of the Jiufotang Formation in China, was a toothed bird with a dromaeosaur-like tail (w/27 vertebrae), a strong flying ability, and two fused fingers.
` Its feathers were not preserved, but 50 fossilized seeds were found where its stomach once was. It seems to fit somewhere in between the evolution of Archaeopteryx and Confuciusornis.
` For a partial cladogram of some of the other primitive birds and drawings of their skeletons (including enantiornithes - below), check this page out!


Enantiornithes ('opposite birds'), were a varied clade of primitive birds that apparently did not evolve into today's birds, but were rather a sister group that evolved from the same primitive flying ancestors as modern birds. The well-feathered Protopteryx fengnensis was one of them, which has many advanced characteristics of birds, though its hands and alular digits were long like those of Archaeopteryx and Confuciusornis.
` Though it lived in the Late Cretaceous period, in Madagascar, Rahona ostromi was an enantiornithine which had apparently retained many primitive characteristics, including unfused foot-bones, which had bore, as Forster et al wrote:

` "The most striking feature of the nearly complete left foot... is the structure of digit II. It is extremely robust relative to other digits... and distinctive in morphology... The digit ends in an enlarged sickle-shaped claw. [D]igit II was found in hyperextension, whereas digits III and IV were flexed. This distinctive morphology of an enlarged digit II is found only in dromaeosaurid and troodontid maniraptors..."

` In other words, it had retained an early characteristic, the slashing 'killer claw' until near the end of the 'Age of Dinosaurs'.
` As far as advanced characteristics go, Eoalulavis hoyasi ('dawn alula bird from Las Hoyas'), which lived 115 million years ago in Early Cretaceous Spain, is known to have had an especially advanced characteristic - the alula. Like the leading-edge wing-slats of a plane, the alula is needed to prevent stalling at slow speeds/high angles of attack, and so its presence shows that Eoalulavis would probably have been able to take off, land, and maneuver among tree branches as well as a modern bird can.


Euornithes ('true birds') - as I am too tired to describe one of these, so I'll just mention first names: Struthio, Haliaeetus, Erithacus, Ciconia, Aix, etc. If these seem to be unfamiliar species, put them into a search engine to jog your memory. ; )


` Anyhow, these are some of the first feathered nonavian dinosaurs described. When more species are uncovered, I will list their names in this post and write about them somewhere else. To learn a bit about feather development, go to Dinosaurs and their Descendents 4.