Dinosaurian, the Evolution of Birds, and the Origin of Flight

Anglický jazyk

Dinosaurian, the Evolution of Birds, and the Origin of Flight

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O knihe

Scientific Essay from the year 2015 in the subject Earth Science / Geography - Palaeo-Ontology, , language: English, abstract: This paper deals with the evolution of flight in dinosaurs and describes the physical characteristics of cretaceous feathered dinosaurs. The author also deals with the hypothesis that the fossil record is probably not complete at present and that an animal very similar to Deinonychus gave rise to birds and then later to dromaeosaurs, including Deinonychus and Velociraptor.

The animals which dominated the earth for over 150 million years are called dinosaurs. In them, you can see forms of every major group that ever lived, including birds. In a phylogenetic chart that further describes the evolutionary relations between organisms(e.g., dinosaurs), it's apparent to identify these animals in detail, step by step using physical features, that are evident in the anatomy of the closely related groups that exist among the Dinosauria.

Those features that define larger groups are called primitive because they are thought to have evolved earlier, whereas features shared by smaller groups are called derived or advanced. Used in this way, the terms primitive and advanced are relative and do not imply that one feature is better than another. In our chart and cladogram, the character "hole in the hip socket" defines the group dinosaurian, which contains all dinosaurs including birds. Within all vertebrates, having a hole in the hip socket is unique to the dinosaurian, and we say its derived with respect to all vertebrates.

Cladistic analysis indicates that the fossil record is probably not complete and that an animal very similar to Deinonychus gave rise to birds and then later to dromaeosaurs, including Deinonychus and Velociraptor. Analyses show that birds evolved from small carnivorous dinosaurs like Deinonychus and Velociraptor which belong to a group called dromaeosaurs, which lived in the Cretaceous, between 107 and 72 million years ago. Yet, the oldest known bird Archaeopteryx, lived in the late Jurassic about 140 million years ago( Gaffney, 1995).