James Allen Hopson is an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 paleontologist and professor

Professor

A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...

 (now retired) at the University of Chicago

University of Chicago

The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...

. His work has focused on the evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 of the synapsids (a group of amniotes that includes the mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s), and has been focused on the transition from basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 synapsids to mammals, from the late Paleozoic

Paleozoic

The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...

 through the Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 Eras. He received his doctorate

Doctorate

A doctorate is an academic degree or professional degree that in most countries refers to a class of degrees which qualify the holder to teach in a specific field, A doctorate is an academic degree or professional degree that in most countries refers to a class of degrees which qualify the holder...

 at Chicago in 1965, and worked at Yale

Yale University

Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...

 before returning to Chicago in 1967 as a faculty member in Anatomy

Anatomy

Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

, and has also been a research associate at the Field Museum of Natural History

Field Museum of Natural History

The Field Museum of Natural History is located in Chicago, Illinois, USA. It sits on Lake Shore Drive next to Lake Michigan, part of a scenic complex known as the Museum Campus Chicago...

 since 1971. He has also worked on the paleobiology

Paleobiology

Paleobiology is a growing and comparatively new discipline which combines the methods and findings of the natural science biology with the methods and findings of the earth science paleontology...

 of dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s, and his work, along with that of Peter Dodson

Peter Dodson

Peter Dodson is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs and sauropods, and is a co-editor of The Dinosauria, widely considered the...

, has become a foundation piece for the modern understanding of duckbill

Hadrosaurid

Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

crests, social behavior, and variation.

Selected publications

• Clark, J.M. & J.A. Hopson. 1985. Distinctive mammal-like reptile from Mexico and its bearing on the phylogeny of the Tritylodontidae. Nature, 315:398-400.
• Hopson, J.A. & H.R. Barghusen. 1986. An analysis of therapsid relationships. In: The Ecology and Biology of Mammal-like Reptiles (Ed. by N. Hotton III, P. D. MacLean, J. J. Roth, & E. C. Roth), pp. 83–106. Washington DC: Smithsonian Institution Press.
• Hopson, J.A. 1991. Systematics of the non-mammalian Synapsida and implications for patterns of evolution in synapsids. In: Controversial Views on the Origin of Higher Categories of Vertebrates (Ed. by H. P. Schultze & L. Trueb), Ithaca: Cornell University Press.
• Allin, E.F. & J.A. Hopson. 1991. Evolution of the auditory system in Synapsida ("mammal-like reptiles" and primitive mammals) as seen in the fossil record. In: The Evolutionary Biology of Hearing (Ed. by D. B. Webster, A. Popper, and R. Fay), New York: Springer-Verlag.
• Wible, J. R. & J. A. Hopson. 1993. Basicranial evidence for early mammal phylogeny. In: Mammal Phylogeny (Ed. by F. S. Szalay, M. J. Novacek, & M. C. McKenna), New York: Springer-Verlag.
• Hopson, J. A. & G. W. Rougier. 1993. Braincase structure in the oldest known skull of a therian mammal: Implications for mammalian systematics and cranial evolution. American Journal of Science, 293-A: 268-299.
• Hopson, J.A. 1995. Patterns of evolution in the manus and peers of non-mammalian therapsids. Journals of Vertebrate Paleontology, 15:615-639.

External links

• Organismal Biology & Anatomy faculty homepage
• Committee on Evolutionary Biology faculty homepage
• Recent work on the evolution of the mammalian ear