Select the incorrect statement from the following

The correct answer is Ernst Mayr used Systema Naturae as the title of his Publication.

Let us analyze each statement to determine its correctness:

1. ICZN stands for international code of zoological nomenclature:
This statement is correct. The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals.

2. Each statement in key is known as lead:
This statement is correct. In taxonomy, a key is a device used to identify plants and animals based on similarities and differences. The keys are based on contrasting characters, usually in a pair called a couplet. Each statement or choice in the taxonomic key is referred to as a "lead".

3. Taxonomic keys are tools that help in identification based on characteristics:
This statement is correct. Taxonomic keys are indeed identification tools designed to help users identify unknown organisms step-by-step using diagnostic morphological or anatomical characteristics.

4. Ernst Mayr used Systema Naturae as the title of his Publication:
This statement is incorrect. The famous book Systema Naturae was written and published by the Swedish botanist and zoologist Carl Linnaeus (first edition published in 1735), who laid the foundations for modern binomial nomenclature. Ernst Mayr, on the other hand, was an influential evolutionary biologist known for his work on the biological species concept and publications such as Systematics and the Origin of Species (1942).

Therefore, the incorrect statement among the options is the one stating that Ernst Mayr used Systema Naturae as the title of his publication.