But this feathering has only been found in theropods that are classified as coelurosaurs
, a diverse group including animals like T.
By the close of the Cretaceous, however, Asia sported a large theropod fauna of tyrannosaurids and other large coelurosaurs
that was similar to faunas in North America, but drastically different from those on the southern continents (Africa, South America, India, Madagascar, Australia).
Of course, the presence of "protofeathers" (and "true" feathers) in non-avialan coelurosaurs
(such as Dilong paradoxus, Sinosauropteryx prima, and many others) still puts the origin of feathers before the origin of flight and suggests that the original function of these structures was for thermoregulation.
Now, it appears that tyrannosaurs evolved much earlier than that, from a group of small, meat-eating dinos called coelurosaurs
rex and its cousins evolved much earlier, from a line of small, meat-eating coelurosaurs
. Fossils show that these creatures shared many skeletal features with tyrannosaurs.
* Tyrannosaurs belong to a broader, diverse group of dinosaurs known as the coelurosaurs
. Most paleontologists believe this group gave rise to birds.
Reduction in tail size is first seen in coelurosaurs
such as ornithomimids and dromaeosaurs (Gauthier 1986; Gatesy 1990, 1994), which have tails of smaller diameter and fewer segments [ILLUSTRATION FOR FIGURE 6 OMITTED].
In contrast, small herbivores (ankylosaurs and pachycephalosaurs), carnivorous dinosaurs (tyrannosaurs and coelurosaurs
), and enormous herbivores without advanced chewing abilities (sauropods) remained relatively stable or even slightly increased in biodiversity.
Combined with the elongated forelimbs of coelurosaurs
(these are thought to have allowed them to grab and hold prey), students may come to visualize that a transition to eating flying insects might have favored the evolution of leaping with the aid of feathered forelimbs and, ultimately, to powered flight (Garner et al., 1999).
Many paleontologists speculate that modern-day birds emerged from Coelurosaur
rootstock, an idea bolstered by recent finds in China of early Cretaceous fossils of what were apparently feathered Coelurosaurs
(SN: 4/28/01, p.
Seemingly, the footprints, which range from 10cm (3.9in) to 80cm in length, belong to dinosaur types including tyrannosaurs, coelurosaurs