In terms of the Plesiosauria, Trinacromerum is in the Polycotylidae family of short necked plesiosaurs. Its stout little body, in terms of enormous marine reptiles, was designed for quicker movements through the water. Whereas icthyosaurs were streamlined and built for speed, most plesiosaurs appear to have been quite slower and not as often built for anything nearing speed. That said, Trinacromerum was one of the more streamlined and faster of the short necked plesiosaurs. The sagittal crest on the skull allows for more muscle attachment and, most likely, these muscles then attached to the lower haw. This means that the snapping shut of the lower haw was rather quick and violent. A quick, strong jaw closure combined with a faster swimming body plan means that Trinacromerum was capable of chasing down faster moving prey than its slower swimming relatives. Imagine that suddenly chasing you through the ocean!