amniotes

A subtle point here: this appears to be about when the lineage leading to amniotes diverged from amphibians.

It doesn't mean that, at the time of these fossils, these organisms were as yet amniotes, in the sense of having all the characteristics of that clade.

So there are chances that actually endothermy was developed in the common ancestor of all amniotes.

And dinosaurs are reptiles, mammals and reptiles are amniotes [1], both amniotes and amphibians are tetrapods, tetrapods are actually fish[2], and there's no such thing as a fish[3]!

Compared to egg-laying (first amniotes, approx 340 million years ago), pregnancy hasn't been around that long.

They represent the earliest known occurrence of dunefield-dwelling amniotes―either basal reptiles or basal synapsids...

Non-heterosexual behaviour can be observed in most social amniotes, even those without fingerprints.

So there have been at least 4 groups of amniotes that looked like sharks, cetaceans among mammals and at least 3 groups of diapsids.

If you go a bit farther back, we all ultimately come from the same lizard-like amniotes, newly emerged onto land from amphibious ancestors.

Because there are certain similarities between the homeothermy of birds and that of mammals that seem less likely to be coincidences, there exists an alternative hypothesis, that homeothermy and fast metabolism has already evolved in the ancestor of all amniotes.

The paper Early adaptation to eolian sand dunes by basal amniotes is documented in two Pennsylvanian Grand Canyon trackways [1]: > The narrow width of both trackways indicates that both trackmakers had relatively small femoral abduction angles and correspondingly relatively erect postures.

> Because there are certain similarities between the homeothermy of birds and that of mammals that seem less likely to be coincidences, there exists an alternative hypothesis, that homeothermy and fast metabolism has already evolved in the ancestor of all amniotes.

Among the weird suggestions of this document are that birds show a "parallel evolution of consciousness," implying that our common ancestors (ancient amniotes, lizardy things) were not conscious; also that whole classes of amniotes are not conscious.

> The animals (basal amniotes) from which non-mammalian synapsids evolved were traditionally called "reptiles".

> Among the weird suggestions of this document are that birds show a "parallel evolution of consciousness," implying that our common ancestors (ancient amniotes, lizardy things) were not conscious; also that whole classes of amniotes are not conscious.

Just read the abstract of the article [1]: "It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups.