Spike (a Triceratops, whom the Marshalls have already encountered and named), Big Alice (an Allosaurus), the Lost City, the Sleestak, and the Sleestak god (heard and smelled but as of yet unseen) all make their first of many appearances.
The Marshalls have been in the Land of the Lost for at least a month, maybe longer. This is evident because Will says that Cha-Ka's broken leg must have healed by now, and that process takes at least six weeks in humans. (Will wouldn't have any way of knowing the specifics of Pakuni physiology.)