Are Birds the Closest Living Relative to Dinosaurs?

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Are birds the closest living relative to dinosaurs? What is the closest living relative to dinosaurs?


Check out this answer from Consensus:


Birds are not just closely related to dinosaurs; they are modern-day avians that directly descended from theropod dinosaurs.

The fossil record, particularly from the Coelurosauria subgroup, provides compelling evidence for this evolutionary lineage. While birds are the closest living descendants of dinosaurs, crocodilians are their closest living relatives, highlighting the diverse and complex tree of life that connects modern species with their ancient ancestors.

Are Birds the Closest Living Relatives to Dinosaurs?

The evolutionary history of birds has been a subject of fascination and debate since the 19th century. The discovery of the fossil bird Archaeopteryx in 1861, with its blend of avian and reptilian features, sparked a quest to understand the origins of birds and their relationship to dinosaurs. Recent paleontological discoveries have shed light on this relationship, revealing intricate details about the transition from ground-living theropods to flying birds.

The Bird-Dinosaur Connection

The connection between birds and dinosaurs has been increasingly supported by fossil evidence. A pivotal discovery was the identification of feathered dinosaurs, which confirmed earlier analyses that placed birds within the Theropoda group of dinosaurs 4. These feathered dinosaurs, such as the Microraptor, have been described as the smallest and most birdlike dinosaurs yet discovered, belonging to the dromaeosaurs, a group considered by many paleontologists to be the closest dinosaurian relatives of birds 1.

Evolutionary Relationships

The evolutionary relationships of birds have been clarified through the study of both morphological and genetic data. Cladistic analyses, which examine shared characteristics among species, strongly support the notion that birds are closely related to a subgroup within the theropod dinosaurs known as Coelurosauria. Within this subgroup, the scansoriopterygids, dromaeosaurs, and troodontids are among the closest relatives of birds. These findings are bolstered by the discovery of fossil coelurosaurs with feathers in China, providing convincing evidence that birds are indeed coelurosaurs and that feathers evolved before the capability of flight 4.

The Closest Living Relatives

While birds are the direct descendants of certain dinosaur groups, it is also important to note their relationship with other living animals. The closest living relatives of birds are the crocodilians, and together they form the group Archosauria 4. This group also includes the extinct dinosaurs and pterosaurs, as well as many fossil relatives of crocodilians.


Are Birds the Closest Living Relatives to Dinosaurs?

Mark N Puttick has answered: Near Certain

An expert from University of Bath in Biology, Palaeobiology

Today virtually all scientists support that fact that birds originated from within dinosaurs. The bird-dinosaur link is so widely accepted that dinosaurs of the popular imagination – Tyrannosaurus rex, Brachiosaurus, Triceratops, etc., – are referred to as ‘non-avian dinosaurs (e.g., dinosaurs that are not birds). These non-avian dinosaurs went extinct 66 million years ago at the end of the Cretaceous period in a mass extinction most likely caused by a meteorite, but one major group of dinosaurs did not go extinct and still prospers today: the birds.

Similarities between dinosaurs and birds led scientists to suggests birds are dinosaur’s close relatives. In 1860, a year after the publication of Charles Darwin’s “Origin of species”, the feathered-fossil Archaeopteryx was discovered with many features to link it both to dinosaurs and birds. For example like birds, it possessed a wishbone and flight feathers, and like dinosaurs, it possessed features and teeth and associated characters. Archaeopteryx is sometimes called Urvogel which roughly means ‘first bird’. However, this is a slight misnomer: Archaeopteryx is undoubtedly a very close relative of the line leading to birds but we cannot with certainty say it was an ancestor in itself, only a close relative of the actual bird ancestor.

Famous scientists have made the bird-dinosaur link, such as ‘Darwin’s bulldog’ Thomas Henry Huxley in the 19th Century and the American ornithologist William Beebe in the early 20th century. However, the idea fell out of fashion for a time, until the 1970s when John Ostrom and others reinterpreted dinosaurs as fast-moving, ‘warm-blooded’ active animals like birds, rather than lumbering ‘terror lizards’. By re-evaluating dinosaurs in this way, scientists re-ignited the idea that birds are indeed dinosaurs.

Further analytical support came in the 1980s. Scientists can build relationships of taxa based upon their shared, derived characteristics, such as bone structures. By making databases of these characters scientists have been able to prove birds are descendants of a group of dinosaurs known as theropods. To do this, researchers construct family trees of organisms using an approach called phylogenetics. These phylogenetic analyses model the relationships of taxa based on their shared characteristics, and since the 1980s phylogenetic analyses have confirmed that birds are related to dinosaurs.

Since the 1980s, numerous fossil finds have strengthened these claims. Most famously, many dinosaur species have been shown to possess feathers with many of these spectacular finds originating from China.


Are Birds the Closest Living Relatives to Dinosaurs?

Dennis F A E Voeten has answered: Near Certain

An expert from Uppsala University in Evolutionary Biology

The classification of living and extinct animals in itself aims to place the biodiversity around us in a comprehensible framework: we humans like to see things organised. In doing so, biologists and palaeontologists always try to truthfully capture the evolutionary interrelations of lifeforms and update this framework when new information becomes available. This was traditionally achieved by comparing as many morphological traits of known and newly described animals as possible under the assumption that anatomical similarity always reflects underlying evolutionary relationships. Although this works reasonably well, some quite similar animals may look alike because of comparable ecological roles rather than because of close family relationships. Because of this so-called convergent evolution, sharks and dolphins superficially resemble one another, although cartilaginous fishes and secondary aquatic mammals are only remotely related. On the other hand, two very differently looking animals may actually be closely related or even represent the same species. The males and females of some bird species look completely different, and the lion and jaguar are actually sister species within the same genus, underlining their close evolutionary relationship despite their quite different appearances. Biologists now better understand exactly which morphological traits more reliably reflect heritage, and can even draw from comparison of DNA and protein sequences to fingerprint species and calculate when two lineages separated from each other.

Crocodiles superficially resemble lizards such as monitor lizards and iguanas, but actually belong to a different group altogether. Their lung structure, for example, much more closely resembles that of birds than those of their cold-blooded lookalikes. A detailed comparison of their DNA with those of other animals confirms that there is indeed more than meets the eye: crocodiles are actually more closely related to birds than to lizards. Crocodiles and birds are the only living representatives of a larger group named Archosauria, or “ruling lizards”, which also includes the extinct pterosaurs and dinosaurs. Birds actually still have scales that recall their “reptilian” ancestry, although they are now confined to the lower legs and feet.

The wrist of raptorial dinosaurs contains a halve-moon-shaped bone that allowed their hands hand to move sideways rather than engage in the “human-like” up-and-down movement that raptors often erroneously feature in movies. This exact movement is what allows birds to fold their wings over the back when they are not used. The wrist of a bird is made up of bones that have fused to strengthen the wing for flight, but this original halve-moon-shaped bone can still be clearly recognised as part of one of their wrist bones. Furthermore, birds often have small humps on one of their arm bones that evolved to attach the long feathers. Very comparable humps have been identified on corresponding arm bones of some extinct dinosaurs, but are absent in crocodiles. These two features have been demonstrated to truthfully reflect a closer relationships between dinosaurs and birds than between dinosaurs and crocodiles.

The final piece of the puzzle again requires understanding of the way biologists classify different lifeforms and, more specifically, how we delimit groups. Progressive insight has revealed that many groups described quite some time ago actually represent “non-natural” groups. This means that such groups contain animals that may not be closely related after all (such as “pachyderms”, now known to be convergent in their large stature and thick skin rather than close relatives) or groups that were supposed to encompass an evolutionary lineage but were later found to exclude certain members (mammals, for example, evolved from reptiles but are themselves not considered reptiles). This latter scenario also applies to birds. Although it gradually became clear that birds evolved from small feathered dinosaurs, they nevertheless initially remained excluded from dinosaurs. However, because we now increasingly rely on definitions of evolutionary groups as “the last common ancestor of species X and species Y, and all of its descendants”, all species that originated in one specific group, such as birds within dinosaurs, will have to be considered members of that group. This means that birds are therefore not only the closest living relatives to dinosaurs but are, by definition, dinosaurs themselves!

Are Birds the Closest Living Relatives to Dinosaurs?

Jingmai O’Connor has answered: Extremely Likely

An expert from Institute of Vertebrate Paleontology and Paleoanthropology in Evolutionary Biology, Geology

These days its no longer controversial, all data strongly indicates that birds are living dinosaurs. The only controversy now lies in which group of dinosaurs are birds most closely related to (somewhere in the Maniraptora, probably the Troodontidae). Numerous lines of evidence support placement of Aves within the Dinosauria (including molecular and genetic data). From the paleontological aspect, there are skeletal indicators that place birds within the group Theropoda (which includes famous relatives such as T. rex and Velociraptor) such as the morphology of the wrist (in particular the semilunate carpal), the shared presence of a furcula or wishbone (formed by fusion of the clavicles), and even the shape of the brain as indicated from endocasts (that indicate enlargement of the brain associated with living birds began in the Maniraptora). In dinosaurs very closely related to birds it is even hard to distinguish them from primitive birds, which are very different from birds today (not yet having evolved modern bird features such as a pygostyle or toothless rostrum/beak). For example, take Anchiornis and Archaeopteryx: to name a few features, they both lack ossified sternal plates, have similar morphology of the furcula, coracoid and scapula, and have very similar skull morphology. In fact, at the moment there is no clear morphological definition for Aves. Other evidence comes from fossilized behaviors, for example oviraptorosaurs preserved on their nests (not necessarily brooding their eggs but protecting them from predators rather than simply burying them, as in more primitive dinosaurs) or Mei long preserved sleeping with its head tucked under its wing like a modern duck. The strongest evidence comes from the preservation not only of feathers or proto-feathers in a diversity of dinosaurs but of pennaceous feathers (those with a rachis and vane on either side) arranged into wings (although not necessarily yet used for flight) in taxa such as Caudipteryx (a basal oviraptorosaur), Anchiornis (probable troodontid), and the dromaeosaurid Microraptor (this taxon was using its wings for flight, but evolved this ability in parallel to the avian lineage). Today, feathers are only found in birds. But during the Mesozoic, feathers would have been found only in dinosaurs… including birds.

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