Minor bone change made June 16, 2015 on a note sent minutes ago (see below) and June 19, 2015 with the addition of taxa to the Theropoda (Fig. 2).
As readers know, I have avoided
doing the large well-known dinosaurs in favor of the lesser-known basal dinosauroids like PVL 4597, Trialestes and Herrerasaurus. I wanted to know the evolutionary relationships dinosaurs had with other prehistoric reptiles while others concentrate their efforts on the more popular dinosaurs.
But now and then
you have to add some more popular forms, like T-rex, Gallus the chicken and, on another branch of the large reptile tree, humans (Homo sapiens). Whenever any taxon is added to the large reptile tree, its complete ancestry back to Devonian basal tetrapods can be traced. With that list of intervening taxa, you can see, more or less, the direct lineage of any included taxon (up to 556 at last count). You can see where traits were enlarged or added while others were reduced or eliminated.
Paleontologists know quite a bit
about the lineage of T-rex. Many of its closest relations are known. The majority of these are not included in the large reptile tree taxon list. So, with this in mind, the closest known sister on the present taxon list is Sinocalliopteryx and both nest on the branch leading to birds.
Did T-rex have feathers?
Earlier I suggested that the evolution of feathers in basal naked dinosaurs was associated with their adoption of a bipedal gait among basal archosaurs. Later larger dinos often developed scales, which quite possibly were derived from primitive feathers, just as chicken leg scales are derived from feathers. The fossil and extant evidence for feathers has its advent with Sinocalliopteryx in the taxon list of the large reptile tree and most taxa that follow also preserve feathers.