The Ephippioceratidae, named by Miller and Youngquist,1949, is a family of nautilids that are part of the Clydonautilaceae and which form a early offshoot from the Liroceratidae, having branched off in the Mississippian (Early Carboniferous). Their range is into the Early (Lower) Permian.
In general form the Ephippioceratidae are similar to the Lyroceratidae but are distinguished by deep ventral and dorsal, forward divergent, saddles in the suture.
The Ephippioceratidae has the second longest range of the Clydonautilaceae, exceeded only by the Lyroceratidae. In spite of its long range, the Ephippioceratidae is a rather small family, containing only two genera (Kummel 1964): Ephippioceras and Megaglossoceras
Ephippioceras Hyatt, 1885, has a nautiliconic, subglose, smooth or slightly costate, rapidly expanding shell; whorl section reniform (kidney shaped), venter and sides broadly rounded, umbilicus closed in the adult stage; suture with a V-shaped, narrowly rounded ventral saddle and broadly rounded lateral lobe (per side); siphuncle small, subcentral. Ephippioceras has a stratigraphic range from the Lower Carboniferous (Miss) to the Lower Permian; that of the family. It has been found in North America, Europe, and Asia (China).
Megalossoceras Miller, Dunbar & Condra, 1933, is similar to Ephippioceras except that the ventral saddle is broad adn tongue-shaped and its range is far more limited. Megalossoceras is known only from the Upper Carboniferous (Pennsylvanian) of North America (Kansas, Nebraska, Colorado, Missouri).
- Bernhard Kummel,1964. Nautiloidea- Nautilida. Treatise on Invertebrate Paleontology, Part K, (Nautiloidea,..). Geological Society of America and Univ. Kansas Press.