The Goreslingus Rex is mentioned once in "The Complete Book of Dragons", when discussing dragon eggs. This dragon is not written about any further. Though Goreslingus Rex is a rather interesting name, no assumptions can be made from it.

"In the same way, a Common or Garden Dragon egg looks horribly similar to the egg of a Goreslingus Rex dragon. But a baby Common or Garden dragon is likely to lick you and think you are its mama, while a baby Goreslingus Rex dragon will send you straight to Valhalla with one snort of its dear little nostrils. (Don't blame the poor baby Goreslingus Rex. It thinks it's being friendly.)"
The Complete Book of Dragons