Collection Science 2026.08.14

The Descendants of Dinosaurs That Survived the Mass Extinction and Continue to This Day

Connecting Theropod Dinosaurs and Modern Birds Through Feathers, Skeletons, Breathing, and Nesting Behaviors

#Dinosaurs #Natural History #Paleontology #Dinosaur Ecology #Dinosaur Fossils

While non-avian dinosaurs disappeared during the mass extinction at the end of the Cretaceous period, the entire dinosaur lineage did not come to an end. Today's birds are living dinosaurs that descend from small feathered theropods. Structures once thought to be unique to birds, such as feathers, wishbones, hollow bones, air sac respiration, the posture of sitting on eggs, and folding wrists, are progressively confirmed in the fossils of non-avian dinosaurs.

This list connects dinosaurs and birds not through their external similarities but through shared derived traits and phylogenetic relationships. Not all feathered dinosaurs could fly, and flight was not achieved in one step. Various features, such as the reduction of long tails, changes in forearms and wrists, and the functional adaptations of feathers, combined at different rates. When observing chickens or sparrows, let's look for the remnants of dinosaurs. By comparing various traits in the phylogenetic tree, we can avoid misunderstanding flight capabilities and the origin of birds as a singular event.

Feathers

Feathers have been found in various non-avian theropods, ranging from downy structures to more developed feathers. In this study, the researcher examines the development of flight capabilities in some lineages through insulation, display, and egg protection. However, the discovery of feathers does not mean that all dinosaurs could fly or were covered in the same form. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Furcula

The wishbone, a V-shaped structure created by the fusion of two clavicles, appears in various theropods and modern birds. In this study, the researcher compares the continuity of shoulder structure and skeletal features present before wing flapping. However, the wishbone alone does not determine flight capabilities or the exact phylogenetic relationship with birds. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Hollow Bones

Hollow bones in many theropods have developed internal air spaces that reduce weight. In this study, the researcher explores the air sac-linked respiratory system and the efficient methods of supporting large bodies. However, stating that the bones are hollow does not imply they are weak or easily breakable. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Air Sac Breathing

Air sac respiration is examined by comparing the air spaces around the spine and ribs with birds' air sac systems. In this study, the researcher infers the evolutionary pathways of efficient air movement during inhalation and exhalation. However, soft tissues themselves are not fully preserved, so detailed structures are compared and reconstructed. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Three-Toed Walking

Three-toed locomotion is common in the hind limbs of theropods and many birds, showing a forward-facing arrangement of three toes. In this study, the researcher examines how bipedal locomotion, balance, and changes in toe structure evolved in the bird lineage. However, just because the number of toes is the same, it does not mean we can classify all three-toed animals into the dinosaur lineage. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Sitting on Eggs

Nesting behavior, such as sitting on eggs, is preserved in the Oviraptorosaur adults who are shown spreading their forearms over the nest. In this study, the researcher tracks the origins of behaviors that protect eggs with the body and feathers, similar to birds. However, fossilized positions do not provide information on temperature regulation methods or rearing durations for all species. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Eggs and Nests with Hard Shells

Hard-shelled eggs and nests show that both dinosaurs and birds lay eggs with extra-embryonic membranes and shells and utilize various forms of nests. In this study, the researcher compares the continuity and diversity of nesting strategies through egg arrangements, shell pores, and breeding grounds. However, modern bird nesting behaviors should not be directly applied to all dinosaurs. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Lunar-shaped Bones in the Wrist

The crescent-shaped wrist bones develop in the wrists of theropods like Maniraptora and help facilitate hand folding. In this study, the researcher explores how the movement of folding the forelimbs toward the body connects to modern birds' wing folding. However, this structure did not instantly lead to the completion of active flight. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Tail Reduction and the Pygostyle

The reduction of tails and pygostyles in early bird fossils shows that long tails shortened through subsequent lineages to become the pygostyle structure seen in modern birds. In this study, the researcher compares the gradual changes in balance and feather support methods during flight. However, it cannot be assumed that all early birds reduced their tails at the same rate. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

Reduction of Teeth and Beaks

The reduction of teeth and the development of beaks occurred in theropods close to early birds that had teeth, but teeth disappeared and beaks developed in various bird lineages. In this study, the researcher examines how changes in food, weight, and developmental processes manifest differently across lineages. However, the mere presence of a beak does not simply classify a dinosaur as closely related to modern birds. Dinosaur behavior is reconstructed from bones, footprints, nests, and traces compared to modern animals rather than direct observations, so we must read confirmed structures and possible interpretations separately. It is also important to remember that existing explanations may be adjusted when new bird specimens or analysis methods emerge.

바로가기

If we only refer to birds as the descendants of dinosaurs, it may sound as though they are completely separate groups. In modern phylogenetics, birds are the surviving theropod dinosaurs, and pigeons and eagles represent the current forms of dinosaur diversity. Feathers and nesting behaviors had alternative functions before flight, and the skeletal and respiratory features necessary for flight were also combined over long periods.

We shouldn't judge relationships based solely on one trait; instead, we should examine the order in which various traits appear in the phylogenetic tree. By comparing early birds like Archaeopteryx, feathered theropods, and modern birds side by side, we can see the gradual reduction of long tails, teeth, and fingers, and changes in wings and beaks. Dinosaurs are not relics of the past; they are lineages that continue to exist today in our skies, cities, and forests. Observing the birds around us while walking, foraging, or preening can make it easy to understand the comparative studies of dinosaur behaviors.

한눈에 보기 10개

Eggs and Nests with Hard Shells

Lunar-shaped Bones in the Wrist

Tail Reduction and the Pygostyle

Reduction of Teeth and Beaks