What do the four ancient animals "non-dragon, non-thorn, non-tiger and non-scorpion" in China mean respectively?

Go here and have a look. I found it on Baidu. The following is a paragraph I intercepted:

The first two paragraphs of "Six First Division" record:

Wen Wangli Tian, the historian Bu Bu said, "The field is in the middle of nowhere, and it will be big. It's not a dragon, it's not a thorn, it's not a tiger, it's not a squat, it's a good omen, it's your master's legacy, so you can help the three kings. "

King Wen said, "What's the sign?"

Translation:

Zhou Wenwang is going hunting, and historians are ordered to do divination, which is a good sign. He said to King Wen, "You will gain a lot by going to the north bank of Weihe River this hunting. What you get is not a dragon, a tiger or a tiger, but a very talented person. God sent him to be your teacher to help you succeed in your career and benefit future generations. "

Zhou Wenwang asked, "Is the omen of divination so good?"