Family Trigonoceratidae Hyatt, 1884

Remarks

The extent and content of genera in the family Trigonoceratidae has been repeatedly debated over the past few decades, and several very different views have been expressed (e.g., Flower & Kummel 1950; Shimansky 1957, 1967; Kummel 1964; Dzik 1984; Histon 1999). Differences of opinion are partly related to the treatment and evaluation of the poorly understood family Koninckioceratidae Hyatt in Zittel, 1900. In this context, two genera ( Temnocheilus M‘Coy, 1844 and Endolobus Meek & Worthen, 1865) are particularly problematic and have been assigned to different families by different authors. For example, Temnocheilus has been placed in the families Temnocheilidae Mojsisovics, 1902, Koninckioceratidae, and Tainoceratidae Hyatt, 1883 . However, the great resemblance to Vestinautilus Ryckholt, 1852 and other members of the family Trigonoceratidae suggests that Temnocheilus should also be included in this family.