Contribution | Notable Findings:

Aristotle debunked interest in fossiles that  Xenophanes first recognized.

His books "Historia Animalium" (9 books), "De Partibus Animalium", and "De Generatione Animalium" set the zoological stage for centuries. He emphasized the value of direst observation, recognized law and order in biological phenomena, and derived conclusions inductively from observed facts. He believed that there was a natural scale that ran from simple to complex. He made advances in the area of marine biology, basing his writings on keen observation and rational interpretation as well as conversations with local Lesbos fishermen for two years, beginning in 344 BC. His account of male protection of eggs by the barking catfish was scorned for centuries until Louis Agassiz confirmed Aristotle's description.

Contribution | Notable Findings:

He wrote "Historia Naturalis" in 37 volumes. This work is a catch-all of zoological folklore, superstitions, and some good observations.

Contribution | Notable Findings:

He is the physician of Roman Emperor Marcus Aurelius, wrote on human anatomy from dissections of animals. His texts were used for hundreds of years, gaining the reputation of infallibility.

Contribution | Notable Findings:

Xenophanes first recognized fossils as animal remains. He also inferred that their presence on mountains indicated the latter had once been beneath the sea.

The latter scientists interest in fossils that had been rejected by Aristotle, and the speculations of Xenophanes were again viewed with favor.

Contribution | Notable Findings:

He made dissections of many animals and humans. He was the first Greek philosopher-scientist to propose a classification of animals, dividing them into blooded animals (Vertebrata) and bloodless animals (Evertebrata). He also held that lower animals had perfected organs and that the brain was the seat of thought.

Notable Findings/ Events:

Various compilers in post-classical and medieval times added to the "Physiologus" (or, more popularly, the "Bestiary"), the major book on animals for hundreds of years. Animals were believed to exist in order to serve man, if not as food or slaves then as moral examples.

The fossil record contains evidence of the first tetrapods, which are now extinct amphibian species that lived about 400 million years ago.

The first main species of amphibians appeared some 360 million years ago, from fishes whose fins had developed into legs. At the time, amphibians were far larger than what we know of today's amphibians.

Only in the late Carboniferous period, between 310 and 300 million years ago, can we confidently identify the first real amphibians.

Frogs, toads, salamanders, newts, and a group of rare earthworm-like amphibians known as "caecilians" are likely to have descended from a single ancestor who lived in the middle Permian or early Triassic periods.

The first known frog (Triadobatrachus) lived approximately 250 million years ago which is in early Triassic.

The Nasikabatrachidae family contains only two species of purple frogs. This family is native to India's Western Ghats and has evolved independently for roughly 100 million years.