Yale professor emeritus John H. Ostrom, a widely influential paleontologist who argued that birds, not lizards, are the most logical descendents of dinosaurs, died at an assisted living facility in Litchfield, Conn. July 16 of complications from Alzheimer’s Disease. He was 77.

Ostrom, professor emeritus of geology and geophysics and curator emeritus of paleontology at the Peabody Museum of Natural History, sparked a renaissance in the study of dinosaurs with his 1964 discovery of Deinonychus. The small carnivorous dinosaur’s remains led Ostrom to suggest dinosaurs might be active and warm-blooded, not cold-blooded as scientists then believed.

“Getting into the mindset of seeing them as active, warm-blooded, bird-like – that’s a tremendous transformation in how we see the world, and John’s work all jump-started that,” said Jacques Gauthier, who took over as curator of Vertebrate Paleontology at the Peabody when Ostrom retired. “John really brought in the dinosaur renaissance.”

Ostrom’s theories that dinosaurs were more anatomically similar to birds than lizards were met with sizeable controversy, and scientists questioned the accuracy of his claims for years. Ostrom’s hypothesis was only recently validated when fossils of a feathered dinosaur were discovered in China.

In addition to revitalizing the field of vertebrate paleontology, which had been largely focused on collecting fossil specimens, Ostrom’s research influenced pop culture as well, Geology and Geophysics Department Chair Leo Hickey said. The Deinonychus was the model for the raptors in the novel and film “Jurassic Park,” he said.

Ostrom first joined the Yale faculty in 1961, only one year after receiving his Ph.D. in geology and vertebrate paleontology from Columbia University, and he remained at the University until his retirement in 1992. Colleagues described Ostrom as a quiet but meticulous scientist who worked diligently to build a body of evidence to convince other paleontologists that dinosaurs were indeed warm-blooded.

“He was not splashy or flashy. He was in a field of course where the material itself lends itself to heroic proportions, but he was very low-key about it,” Hickey said. “What he really brought to the field…was the very, very high quality of the work that he did.”

Alan Brush, professor emeritus of physiology and neurobiology at the University of Connecticut, who worked occasionally with Ostrom since the late 1970s, said Ostrom was incredibly patient and rigorous in accumulating and analyzing data.

“He was wonderful to work with because he was…extremely knowledgeable about all of paleontology, and he always listened carefully to whatever arguments you made, whatever information you had,” Brush said. “He always was gracious, accommodating, answered people’s questions no matter who they were – that was his strength.”

Ostrom’s family will hold a private service this weekend, and a memorial service will be held during the upcoming academic year at Yale.