Apocrinoceratidae is an extinct family of ammonoid cephalopods belonging to the order Ammonitida. These marine molluscs existed during the Late Cretaceous period, approximately 100 to 66 million years ago.
As a family within the diverse group of ammonites, Apocrinoceratidae possessed an external, chambered, and typically coiled shell. The internal structure of these shells, like all ammonoids, included septa dividing the shell into gas-filled chambers and a siphuncle for buoyancy control. The family is often placed within the superfamily Acanthoceratoidea or a closely related group, characterized by certain features in their shell ornamentation and complex suture lines.
Paleontologists recognize members of Apocrinoceratidae by specific characteristics, which can include strong ribbing, tubercles, and distinct patterns in the suture lines—the intricate wavy or fractal lines formed where the septa meet the outer shell wall. These morphological features are crucial for taxonomic classification and provide clues about their lifestyle, environment, and evolutionary relationships. Fossils of Apocrinoceratidae are important for biostratigraphy, helping to date and correlate Late Cretaceous sedimentary rock layers around the world. Their presence in marine fossil records contributes to our understanding of ancient marine biodiversity and the faunal assemblages that existed before the end-Cretaceous extinction event.