Are dinosaurs extinct?

Dinosaur remains have been found on every continent on earth. They were vertebrate animals that dominated the earthly “ecosystems” for over 160 million years, first appearing 230 million years ago (1, Dinosaur). Dinosaurs lived during the Mesozoic Era, from late in the Triassic period (about 225 million years ago), until the end of the Cretaceous (about 65 million years ago). During the years of their known existence, they evolved in many dissimilar shapes and sizes, with many equal diverse modes of living (1, The Dinosauria). However, a catastrophic extinction event, (also known as the Cretaceous-Tertiary extinction), ended the dominance of dinosaurs on land (1, Dinosaurs).

Many people believe dinosaurs to be extinct. However, it is evident that dinosaurs live on today as birds. The Cretaceous-Tertiary extinction event caused extinction of all dinosaurs except for the line that had already given rise to the first birds (4, Dinosaur). The dinosaurs that gave rise to the first birds are known to be the “theropod” (1, Dinosaur). So rather than to refer dinosaurs and birds as separate groups, it is best to refer to dinosaurs as “non-avian”, and birds as “avian dinosaurs” (1, The Dinosauria). Therefore it is incorrect to say that dinosaurs are extinct because they have left living descendants in unique forms, modern bird’s being one of them.

Many people who study dinosaurs consider birds to be dinosaurs. Like dinosaurs, birds are archosaurs. They are “archosaurs diapsids” that share similar characteristics. Both dinosaurs and birds skull have two holes, called the temporal fenestrae, located where the jaw muscles attach. They both also have teeth that grow from their sockets, rather than as direct extensions of the jaw bones. Such traits establish a clear view that dinosaurs and birds are related. Dinosaurs are divided in two orders of clades depending on the basis of their hip structure, “Saurischia” (lizard-hipped) and “Ornithischia” (bird-hipped).” Saurischians are dinosaurs that originally “retain” the hip structure of their ancestors. They include theropod dinosaurs (4, Dinosaur). Birds evolved from the dinosaurs with “lizard hips” (5, Dinosaur). Not only does this verify that dinosaurs and a birds are related, it also confirms that birds evolved from theropod dinosaurs as well.

Birds share over a hundred distinct animal “anatomical” features with theropod dinosaurs. They share skeletal similarities that include the “neck, pubis, wrist (semi-lunate carpal), arm and pectoral girdle, shoulder blade, clavicle and breast (7, Dinosaur).” Such similarities show that birds and dinosaurs have almost the same bone and body structure make up. It was also recently discovered that birds and Tyrannosaurus share similar reproductive tactics. When laying eggs, female birds grow a “special type of bone in their limbs.” This bone is rich with calcium and forms a layer inside the hard outer bone that is used to make eggshells. The presence of “endosteally-derived” bone tissues lining the interior “marrow cavities” of portions of the Tyrannosaurus rex specimen’s “hind limb”, suggests that Tyrannosaurus rex use similar reproductive strategies. In addition to birds and dinosaurs having similar reproductive systems, a dinosaur embryo was found without teeth, proposing that some parental care was required to feed a young dinosaur; which makes it possible that adult dinosaurs have to regurgitate into a young dinosaur’s mouth to provide nourishment (7, Dinosaur). This is a characteristic of modern birds. Dinosaurs have similar skeleton make up and reproductive systems as birds which allows scientist to relate the two animals.

Birds and dinosaurs also have comparable lung systems. According to the “Natural Science Foundation”, large eating meat dinosaurs had an intricate system of air sacs similar to those found in modern birds. The lungs of theropod dinosaurs, “likely pumped air into hollow sacs in their skeletons, as is the case in birds.” Both dinosaurs and birds have complex four-chamber hearts. It is unique that both have the same type of hearts, there have to be a correlation between the two. It is also evident that dinosaurs slept like certain modern birds; with their heads tucked under their arms to keep their heads warm (7, Dinosaur). Such behaviors and similar heart and lung systems makes it more evitable that birds and dinosaurs have similar ancestors.

Dinosaurs are known to have survived to present day as modern birds, which evolved from theropod dinosaurs. As mention earlier many believe dinosaurs to be extinct, but it is indeed noticeable that they have survived as living birds. With the many data in this paper, we know that birds have similar characteristics as dinosaurs  and vice versa. From this research, questions like “can dinosaurs evolve from birds?” are formed. That question I cannot answer, however I believe it is possible. There are many similarities between birds and dinosaurs living behaviors and body structures. This shocking realization makes one ponder can any specie become extinct? Extinction of any species seems almost impossible. It is often thought that the human species will be extinct. Will humans ever become extinct or will they live on in a different form? If dinosaurs survived the catastrophic extinct event, than why can’t humans! I am convinced that the human species will indeed survive, but in a new form, just as dinosaurs did as birds. Birds and dinosaurs have many characteristics and ways of living in common, which makes it hard for one to believe that dinosaurs are extinct!

Dinosaur-Wikipedia. “Dinosaur”

Nov. 2007

http://www.ucmp.berkeley.edu/diapsids/avians.html

Dinosaur-Wikipedia “The Dinosauria”

Nov. 2007

http://en.wikipedia.org/wiki/Dinosaur#feathered_dinosaurs-the_origin_of_birds.html