When going out with peers to a bar or restaurant and the same person never offers to buy a round, hence they have the short arms of a Tyrannosaurus and cannot reach their wallet.
Chris: "have you seen that bird Phil is shagging?"
Dan: "yes, she must be twenty stone easy"
Chris : "yeah, but she has tyrannosaurus tits"
Dan: "fat with no tits? why is he with her ?"
A phrase coined by comedian Johnny Sanchez, relating to an older man of Mexican heritage who, during the process of aging, developed a stomach so large his arms seems to shrink in comparison, making him akin to a tyrannosaurus rex.
The term came to fruition through Sanchez noticing how as Mexican men age, they tend to morph into the description of Tyrannosaurus Mex with larger stomachs and seemingly smaller arms.