Kyouryuu-Chan To Kaseki-Kun

Rinko Shinobu may seem like a normal high school girl, but she is actually a hybrid between human and dinosaur. Although she usually stays in human form, sometimes her T-rex bits will pop out when she's distracted. The only person who knows her secret is the dinosaur nerd Kazuya Kobake, who tries his hardest to help hide her dinosaur form. But his distracting antics are drawing strange stares from their classmates and stressing him out…
(Source: Natalie.mu, translated)