Question

Evolution

Name of article: New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur–Bird Transition

- Summarize and explain what the article is about! (CAN SOMONE PLEASE HELP ON THIS!!!!)

- What are the authors views?

- What methods were used?

- Most interesting part of article?

- The article is provided below in the web link (copy and paste it will direct you to the article)

http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001957

Answer 1

Summary of the article

It is known that the birds have evolved from early dinosaurs with nine wrist bones through the process of ossification. There has been lot of research that shows that there is no link between the dinosaur and bird linkage but the study of the distal posterior ossification helps that there is a strong connection through the evolution. As the birds evolved from the Novanian dinosaurs one key adaptation was the remodeling of the wrist bones. The embryo and fossil data shows that there is a strong connection between dinosaur and bird. The modern birds that contain four ossifications that are roughly arranged shows that there is an evolutionary relationship between the birds and the Nonavian dinosaur. The transition might have taken place through either fusion or loss or re-evolution of lost bone. On making a comparison the birds have reduced ossification with four bones whereas the dinosaurs had 9.

Authors View

According to the author the birds have evolved from dinosaurs and flight was one of the key adaptation that occurred after remodeling of the bones present in the wrist. Embryology and fossil record of dinosaur and bird helps in finding out the fact that the bird evolved due to ossification of nine wrist bones in dinosaurs into 4 ossifications.

Methods Used

In order to study and identify the homologies, it is important to study the developmental and paleontological data routinely. In this we have studied the development of embryonic wrist skeleton using classic clearing and staining techniques. There are number of species that was used for the study to deduce the phylogenetic relationships. Another technique that was used was whole mounting immunostaining of proteins that is expressed within embryonic cartilages. There are number of paleontological studies done on the carpal bones that study and gives an insight about the evolution of the bird line.

Interesting Part of Article

The results are quite interesting as it shows that the proximal – anterior ossification of the carpal bone develops from composite of radiale + intermedium cartilage. The bone is called as radiale + intermedium cartilages in paleontology. It was also found that the distal – anterior ossification develops from the embryonic cartilage through the expression of two distinct domains of the collagen expression. It was also found as per the evidences that the proximal – posterior carpal of adult wing is a pisiform. With all the developmental hypothesis, it is found that there is a great possibility that the birds have evolved from the dinosaurs.