transitional fossil

noun

: a fossil that exhibits characteristics of both ancestral and derived forms

During the past 30 years, new discoveries and reinvestigations of long-forgotten specimens have coalesced into a flood of transitional fossils. Paleontologists have unearthed walking whales from Pakistan, feathered dinosaurs from China …

—Courier News (Bridgewater, New Jersey), 27 Feb. 2011

However, although the mammal and bird origins are both documented by numerous transitional fossils, turtles appear abruptly.

—Michael S. Y. Lee, Science, 24 Sept. 1993

Word History

First Known Use

1850, in the meaning defined above

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