It may be a wolf spider, or even a brown recluse. The brown recluse spider can be deadly to pets and also humans under the right circumstances. Do a search on the internet for brown recluse spiders, and there should be a picture of one with a full description of the poison they produce and the damage they cause to the skin. Can you see the area where your dog may have been bitten? Possibly your dog got bit on his mouth area. Wolf spiders usually don't produce a deadly bite. I'm sorry to hear about you dog.
