The Aspidoceratinae is a subfamily in the perisphictacean

Perisphinctaceae

Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic to Lower Cretaceous ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter....

 ammonite family, Aspidoceratidae

Aspidoceratidae

The Aspidoceratidae comprise a family of middle and upper Jurassic ammonites that make up part of the superfamily Perisphinctaceae, characterized by evolute shells, commonly stocky, that tend to develop tubercles....

 found world wide in middle and upper Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 sediments.

Aspidoceratinae differ from Peltoceratinae in that the early biplicate ribbed stage is lacking, or greatly reduced, and no forms with lappets are known. Aptycus are bivalved and very durable, and in the "lower Kimmeridgian form Aptychus beds, containing few or no ammonites". (Kimmeridgian is middle Upper Jurassic, follows the Oxfordian and predates the Tithonian).

The earliest Aspidoceratinae occur with the first Peltoceratinae, and likewise are probably derived from within the Perisphinctidae

Perisphinctidae

Perisphinctidae is a family of Middle and Upper Jurassic discoidal ammonites in the order Ammonitida. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing...

References

• Arkell, et al, 1957. Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L (Ammonoidea). Geol Soc of America and Univ Kansas Press.