What dinosaur looks like a bird with feathers?

Many dinosaurs had feathers, but one dinosaur group in particular resembled modern birds in both appearance and anatomy. This group is known as the theropod dinosaurs. Theropods were a diverse group of bipedal, mostly carnivorous dinosaurs that included fearsome giants like Tyrannosaurus rex as well as smaller bird-like dinosaurs. Of all the theropods, the ones that bore the closest resemblance to modern birds were from an advanced subgroup called the maniraptoran theropods.

Maniraptoran Theropods

Maniraptoran theropods flourished during the Jurassic and Cretaceous periods. They were characterized by feathers, hollow bones, wishbones, and three-fingered hands. Many maniraptorans also had long arms, large brains, and elaborate respiratory systems similar to birds. Well-known examples of maniraptorans include Velociraptor, Deinonychus, Troodon, and Oviraptor.

Within the maniraptorans, the subgroup called the paravians included the dinosaurs most similar to modern birds. Paravians possessed asymmetrical flight feathers, fused wrist bones, and a wide range of avian traits. Paravians included famous dinosaurs like Archaeopteryx as well as the smaller microraptorine and troodontid dinosaurs.

Archaeopteryx

Perhaps the most iconic dinosaur that resembled a modern bird was Archaeopteryx. Archaeopteryx lived around 150 million years ago during the late Jurassic period in what is now Germany. It is renowned as the first clear example of a transitional fossil between dinosaurs and birds.

Archaeopteryx was about the size of a raven, with broad wings, feathers, and a long bony tail. Its skull, teeth, clawed fingers, and other anatomical traits confirm its theropod dinosaur ancestry. But it also had feathers on its wings, legs, and tail that were nearly identical to those of modern birds.

The feathers of Archaeopteryx were asymmetrical flight feathers, meaning the leading edge was narrower than the trailing edge. This shape provides lift, allowing modern birds to fly. The presence of these specialized feathers on Archaeopteryx shows it was likely capable of aerial maneuvering or gliding.

Key bird-like features of Archaeopteryx:

• Feathers nearly identical in structure to modern flight feathers
• Fused wrist bone (semilunate carpal) creating a stable wrist joint
• Wing-like forelimbs with long primary feathers for flight
• Hollow bones and large sternum, indicating strong flight muscles
• Lack of teeth in adult specimens, similar to modern birds

Overall, Archaeopteryx provides some of the strongest evidence that birds evolved from theropod dinosaurs. It displays a clear blend of ancestral dinosaur features and bird-like specializations suited for flight.

Microraptor

Another paravian dinosaur with remarkable similarities to birds was Microraptor. Microraptor lived 125 million years ago during the early Cretaceous period in what is now China. It was a small, four-winged dinosaur that likely glided between trees hunting for mammals, lizards, fish, and insects.

Microraptor had two pairs of elongated wings formed by long flight feathers attached to both the forelimbs and hindlimbs. The hindwing feathers were also asymmetrical like modern bird feathers and could provide lift. Aerodynamic analyses show Microraptor was capable of gliding efficiently, swooping between trees and ambushing prey.

In addition to its gliding adaptations, Microraptor had many anatomical similarities to birds, including:

• Feathers cover the body and wings
• Unified, wedge-shaped tail with long feathers (like birds)
• Enlarged breastbone for flight muscle attachment
• Digitigrade foot posture like modern birds
• Short and high-crested skull
• Large brain and keen sense of vision

The discovery of Microraptor has provided insight into the early origins of flight in theropods before the appearance of Archaeopteryx and modern birds.

Troodontids

The troodontids were a specialized group of bird-like, small predatory dinosaurs related to birds. Troodontids had unusually large brains, excellent vision and hearing, and razor-sharp sickle-claws on their feet for hunting small prey. Well-known examples include Troodon and Saurornithoides.

Troodontids were covered in pennaceous feathers, which are the vaned feathers of birds that allow flight. They also had wishbones and some of the most bird-like skulls of any dinosaurs. In many ways, they would have behaved much like the predatory birds that exist today.

Notable bird-like features of troodontids include:

• Sickle-clawed feet adapted for grasping prey
• Large brains with keen sensory abilities (vision, hearing, balance)
• Feathered bodies with elongated wing feathers
• Wishbones and fused clavicles (collar bones)
• Lightweight skulls with expanded areas for vision and olfaction

Troodontids represent an example of dinosaurs converging on a very avian-like profile and ecology, filling niche roles similar to modern predatory birds.

Avian Ancestors

In addition to the iconic Archaeopteryx and other feathered dinosaurs like Microraptor and troodontids, there are many other theropods with bird-like traits. This includes oviraptorosaurs, alvarezsaurs, and primitive avialans in addition to dromaeosaurs and troodontids.

Characteristics that these theropods share with modern birds include:

• Feathers, especially asymmetrical flight feathers
• Wishbones (furculae)
• Wing-like forelimbs with elongated feathers
• Lightweight and fused bones
• Grasping hands with opposable digits
• Egg brooding and nesting behaviors
• Enlarged sternal plates supporting flight muscles
• Increased brain size and vision regions
• Perching feet with digits that oppose the hallux (back toe)

The presence of so many bird-like characteristics in advanced theropods provides compelling evidence that birds evolved within this dinosaur lineage. Birds inherited many unique features from their theropod ancestors over tens of millions of years.

Visual Comparison

Here is a visual comparison of some key bird-like theropod dinosaurs:

This table summarizes some of the most bird-like anatomical traits and adaptations that evolved in theropods on the lineage leading to birds.

Conclusion

Many theropod dinosaurs developed bird-like features over the course of the Mesozoic Era. This includes the presence of feathers, wing-like forelimbs, fused and lightweight bones, keeled breastbones, wishbones, enlarged brains, and graspy perching feet. Of all the dinosaur groups, maniraptoran theropods like Archaeopteryx, Microraptor, troodontids, and their close relatives most closely resembled the birds we see today.

The incremental acquisition of avian traits across theropod evolution provides some of the best evidence that birds descended from dinosaurs. Theropods like Archaeopteryx and Microraptor especially provide a snapshot into how flight evolved through the modification of feathered forelimbs inherited from earlier bipedal dinosaurs. As dinosaur-bird intermediates, they represent the transition taking place between two major classes of vertebrates, from fearsome dinosaurs to soaring birds.

In summary, among all dinosaurs, maniraptoran theropods were covered in feathers, could glide and fly, occupied avian ecological roles, and possessed anatomy most closely approaching that of modern birds. More than any other dinosaurs, these bird-like theropods illustrate the connection between dinosaurs and birds, bridging the gap between two remarkably different yet closely related groups of animals.