Xiaotian Dog is the most famous dog in Chinese mythology. In the mythological system of China, this dog, known as "Xi Yao" (Fine Waist), is considered the most outstanding among its canine counterparts. It gained prominence by being associated with Erlang Shen, Yang Jian, a distinguished deity.
The origins of the stories about Xiaotian Dog are now hard to verify. The reason why dogs were incorporated into mythology highlights the importance placed on dogs in ancient China. Of course, dogs did not enjoy as high a status as pigs, since there was even a general who was a pig. Although Zhu Ganglie wasn't originally a pig, he did once transform into one. Therefore, pigs clearly had a higher status than dogs. The reason for this is quite obvious. In ancient times, agriculture was the main industry, and pigs were the primary livestock, whereas dogs were mainly used for guarding homes. In ancient times, the term "dog" was often used pejoratively, although pigs were also used to describe someone as foolish, it didn't diminish the importance people placed on pigs.
Xi Yao was a renowned dog and a pet of Erlang Shen. It's said that his status in heaven was quite high, but no matter how high, he was still just a dog and couldn't achieve greatness. Moreover, I imagine that due to Yang Jian's exceptional abilities, Xi Yao rarely had opportunities to demonstrate his own. Since dogs are primarily used to catch thieves, but Erlang Shen, being from a noble lineage and related to the Jade Emperor, wouldn't have any thieves daring to approach him. Also, Yang Jian seemed to lack a formal occupation, thus correspondingly, as his pet, Xi Yao's status also diminished accordingly.
Speaking of Xi Yao's status, it seems even lower than that of a rabbit. Yutu, as the pet of Chang'e, and Chang'e being the lover of the Jade Emperor, typically, a lover's status would be much higher than that of a nephew. Thus, Xi Yao is quite pitiful. As a mighty divine dog capable of eating the moon (though he has to spit it out later), he still isn't as important as a rabbit.