Why no scaled animals with turkey hips?

Factual Questions
1

It sounds like the principal identifying feature of a dinosaur and bird is the shape of the hips and this separates them from the lizards.

So the dinosaurs split off from the lizards, and then later their scales turn into feathers and they shrink to bird size. The shrinkage across the whole group is easily explained, the big ones are destroyed by a comet, climate change, etc. But how does the entire class of animals develop feathers? We seem to be pretty confident that they were not feathered when they split off from the lizards. But by the time they would have developed feathers, there would have been thousands or tens of thousands of different species of dinosaur. If one develops feathers, he’s not mating with any other species than his own. Feathers would have to independently rise across the entire dinosaur line (at least among the small ones), which seems highly improbable.

I could suggest that, because of the shape of the hips, dinosaurs are inherently bipedal and maybe scales are more heavy than they are worth. Having lighter feathers allows you to run on two legs faster and being faster is better than being armored. So, there, we have an evolutionary force that would act similarly across the entire set of animals who are bipedal.

But it seems like we should still see at least a few true dinosaurs, scaled bipedal animals. With all of nature’s diversity, I would think that scales would have won out in at least a few cases? Maybe they exist?

If not, is there any other explanation for the full transfer? Is there sufficient overlap between species that even though A and C can’t make babies, A and B can and B and C can, so eventually the whole set of dinosaurs are able to transfer one mutation (e.g. feathers) across the entire group? A and C are, effectively, mating with each other through a slow process of indirect cross-species mating?

And what about the beak?

2

I’m not sure all of what you said is actually correct.

That aside, keep in mind that the fossil record is woefully incomplete and that the entire group of animals from the period was a nearly complete loss with no extant forms.

You might be interest to know that Birds are Theropods.
Not literally of course, but that is their lineage, they come from the Theropod line.
Which is the “lizard hipped” variety, Saurischia is the main division name

That does not mean it is a lizard of course, just that it has a lizard style hip.
Simply using terms we know to describe something.

Ornithischia is the division described as being “bird hipped” and yet birds do not come from them.

This is not unusual, nature will often come upon a particular design adaptation in different places at different times.
Convergent Evolution i think is the term?

Turkeys, and chickens have very prominent scales, look at their legs.

Sauropods are quadrupeds and yet T-Rex (A Theropod) is bipedal
both are “Lizard Hipped”

As for all “Bird Hippers” being bipedal
Good old Stegosaurus and Ankylosaurus are “Bird Hipped” card carrying Ornithischian’s
So is our favorite Tricerotops.

I would guess rudimentary feathers have been around for a long time and simply changed over time as environment dictated.
I am not sure what you mean about lighter? Lighter than what? Scales?

Scales (Dermal Plates) are not unique to Reptilia.
Mammals can and do posses them, look at Mr Armadillo and Pangolins in extant forms, or some of the ancient mammals.

It’s all just keratin.
Beak, claws, scales, feathers. Reptile or Mammal, Nature used the same erector set.
Not terribly surprising, mammals are reptiles, long removed, so to speak.

As for an extant “True Dinosaur”?
I would say go visit your closest chicken, that is probably about as close as you can get.
They appear to have kept the things needed to survive in the new world and perfected or amplified them over time, and left that which was not useful behind.
Birds are of course Aves, but Aves are theropods and they are the only branch of the family left. Many of their cousins in the theropod family sport feather structures and beaks, it aint all about T-Rex :smiley:
Look at everything branching out of Coelurosauria

Tianyulong is a ornithischian dinosaur who has feathers (or proto feathers if you will), is not related to birds, does not fly, and has a partial beak.
The beak is a wonderful adaptation
Strong, yet very light.
Self maintaining, well suited when chewing is not needed.
It will regrow itself enough to keep ahead of wear and sharpening.

3

The smaller animals that survived likely took to the trees with more frequency. As they jumper from tree to tree to avoid predators those with the best gliding capabilities likely had higher survivor rates. It does seem odd that feathers are so similar and so universal but compared with hair and fur on mammals you would have the same comparison to make. The scale might only have a few directions it can take genetically, feathers and hair. Other mutations were likely unsuccessful.

4

Not quite. Mammalian scales are not hold-overs from some reptile past, but seperately evolved features. I will wait for someone like Colibri to come along, but I believe the current thinking is that mammals and reptiles emerged contemporaneously and one did not evolve from the other. That is, the common ancestor of reptiles and mammals was neither a reptile nor a mammal.

Birds are reptiles, if we take a cladistic approach-- a croc is more closely related to a bird than it is to a snake or a turtle. And they have scales (on their legs), just like reptiles. Feathers evolved from scales, possibly as a mechanism for retaining body heat (like fur in mammals) and/or courtship display. Flight came much, much later. More and more feathered dinosaurs are popping up in the fossil record all the time. These were not necessarily birds, but dinosaurs that also had feathers for whatever reason (not always flight).

5

We always have great threads on evolution, with a scent of honest-to-God professionals in the field–like now.

6

How an entire class of animals develops feathers: it doesn’t. A single species develops feathers, and is successful enough to produce a number of daughter species. (But there are several stages of feather evolution, each involving a single species that developed it, then branching into various daughter species. Google feather evolution to get run-down on feather types and feather prototypes.)

7

I think the OP’s making a bunch of unwarranted assumptions.

First, dinosaurs came in ALL sizes- from huge ones like Diplodocus, Mamenchisaurus, T-Rex, etc… all the way down to dinky little ones like Velociraptor, which contrary to Jurassic Park, was about the size of a turkey. Compsognathus was another small dinosaur. Microraptor was even smaller, and winged.

Second, it’s now thought that feathers were pretty common among dinosaurs. Velociraptor fossils have been found with quill knobs, proving they had feathers. Microraptor (early Cretaceous) had 4 wings and feathers! Others had beaks or beak-like mouth parts.

So more likely than the dinosaurs shrinking and developing feathers, it’s a lot more likely that already small and feathered dinosaurs survived better than their larger cousins. It’s also likely that flight conferred some kind of survival advantage.

Give that 65 million years of evolution, and you have today’s birds, who are essentially dinosaurs in all ways that count.

8

I did not say hold over.
Convergent Evolution.
They both branch out of Amniotes, seemingly around the same time but…
I am not exactly sure if proto mammal has scales
I would guess that early Synapsid’s did, but i could be way wrong since i’d be guessing on a “well it looks like” basis, same i supposed if i had to guess about proto reptile i would guess the same.
(Why cant nature tar wrap some mesozoic meat?)

Reptile and Mammal are like two non identical twins kind of, they start out really similar.
At least by appearances, ive no idea what they looked like internally, organs systems etc. But they look like yea man, we’re on the same path.
If you show someone a proto reptile and proto mammal side by side, 1st thing they say is “Oooh dinosaur” :smiley:

At some point they diverged really wide though, reptilia went on an arms race, and mammalia took an adventure in miniaturization (Kind of) and furballing until they swapped places a few 100 million years later.

Kind of hard to picture dimetrodon as being at the Mammalia family reunion sitting at the old timers table, looks more like he’d be sitting over with B baini at the reptillia reunion
Looks more like we were on the fast track to dino world, king of the hill, only to take a 300 million year detour.

Weird how nature decides these things, be cool to know why, if i could actually live long enough to understand it.

Kind of funny how we have sort of ruined that word over centuries with the Reptile as slow dumb cold blooded primitive bollocks.

Wonder if anyone though slow cold and dumb while being chased by an Ostrich or Cassowary :smiley:

9

Poor Deinonychus, gets to star in a movie, then gets no billing credit

Considering that they died too quickly to “Shrink and Sprout feathers” i myself would say this is about as close to correct as we get.
These little guys just happened to be lucky enough to be able to ride out the storm of what ever exactly happened

Which, as i recall watching my Sebrights* running through the tall grass hunting down
palmetto bugs, squawking back and forth, looking like a scene from Jurassic park, does not visually seem to be a terribly large amount of change.

Unlike mammals, who in the 65 million years, have gone through a large number of models.

Perhaps design perfected?

*Sebrights are small bantam chickens

10

I can’t vouch for its accuracy, but here’s a nice chart of the evolution of birds, highlighting which features (including the various aspects of feathers) evolved when.

11

Do birds all have a common ancestor? My belief had been that there were a number of dinosaur species that independently became bird-like.

12

There were related dinosaur species that were more birdlike than more distantly related species, but there is only one species that is the common ancestor of all birds.

13

It was confusing since you said mammals are reptiles, which you are now seeming to back away from.

All have a common ancestor.

14

It certainly seems unlikely that the characteristics of modern birds developed independently. A lot of new information has been uncovered in just recent years, one of the most important is the growing (settled?) consensus that feathers are not adaptions of scales, but I do wonder how far back that common ancestor goes. For example, did all modern birds have a single very bird like ancestor or did feathers develop and spread diversely among different animals that independently developed flight. It seems most likely not but I don’t know where the evidence now points.

15

There’s a bit of confusion here about the sequence of events in vertebrate evolution.

The earliest fully terrestrial vertebrates, those with an “amniote” egg that could survive on land, probably had scales.

The earliest branch off this line were the ancestors of the mammals. They probably had scales initially but later developed hair for insulation. They lost their scales. The “scales” of modern mammals such as armadillos and pangolins are independently evolved and have nothing to do with the scales of reptiles.

The other branch of amniotes we call the “Reptilia” in a broad sense. This includes turtles, snakes, lizards, crocodiles, dinosaurs, and birds. All of these have retained scales on at least part of the body.

The turtles, and snakes and lizards combined, represent separate branches of the Reptilia. Another major branch of the Reptilia is a group called the archosaurs, which includes crocodiles, pterosaurs, dinosaurs, and birds.

Dinosaurs have traditionally been considered to belong to two major groups, the “Lizard-hipped” group, which contains horned and armored dinosaurs and hadrosaurs, and the “bird-hipped” group, which includes carnivorous dinosaurs (theropods) and sauropods. It now appears that both groups had a common ancestor.

It has been thought that feathers first evolved among the theropods. However, there is evidence that primitive feather-like filaments may have been present in the ancestor of all dinosaurs. In particular, some horned dinosaur relatives had such filaments on the tail.

It is now known that most theropods had feathers or featherlike filaments. True feathers seem to have evolved in some early branch of the theropods. One species would have evolved feathers, and that species gave rise to all subsequent species that had feathers.

Modern birds represent the survivors of one small branch of the theropods. The ancestor of modern birds had feathers.

16

How certain is it that the (most recent common) ancestor of all living birds could fly?

17

100% certain. Birds acquired flight long before the ancestor of all living birds evolved.

18

In addition to “true birds”, one of which was the common ancestor to modern birds, several other “birds in the general sense” evolved. These lines became extinct.

Aviale- flying dinosaurs; birds in the general sense.

Modern birds are not a bunch of disparate dinosaurs that developed similar bird-like features. They are the descendants of the few dinosaurian survivors of the KT event. As was said by other posters.

Similar bird-like creatures (“birds, in the general sense”) did not make it. Maybe they weren’t as well adapted for the disaster, maybe they were unlucky.

Enantiornithes- “anti-birds”- these looked superficially like modern birds.

Hesperornithes- these looked like penguins or loons.

I think it is cool that several other “bird-forms” were vying for ascendancy (along with pterosaurs). Things probably coulda gone in lots of different ways.

19

I recall a * Science* article a few years back describing dinosaur feather evolution. Turns out we already had many samples stuck in amber; we just didn’t know what we were looking at.

20

Is this not backwards?
Saurischian > Theropod > Aves correct?

Which is traditionally referred to as the “Lizard Hipped” bunch
which comically contains Birds.
least wise, i always found it amusing.

Well they are from reptile kind of, synapsids are classed as reptilian, they have not gone full on mammal, they look like Dimetrodon for a bit.

My point was simply, that the animal family had something once, it moved on to something else, then one type of said animal later reintroduces a former feature and specializes it, does not seem surprising to me. Especially if the genetic code was never lost per se. It already has the contruction material on hand.

i suspect the development feathers (and that of hair) to maybe be tied to endothermy.
I could be horribly wrong :smiley:

The need to insulate the body to maintain heat levels.
Protect it from external over heating, and from excessive heat loss.

An exotherm does not need a fur or down blanket, at least that is my thinking.
It would interfere with their ability to exotherm, cant absorb sun heat and if heated can’t get rid of it.