Syringonautilidae is a family of

Nautiloidea Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded speci ...

from the middle to late

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

. Syringonautilidae comprise the last of the Trigonoceratoidea and are the source for the

Nautilaceae The Nautilaceae form one of five superfamilies that make up the Nautilida according to Bernard Kummel (1964), and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilida ...

which continued the

through the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...

and into the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

right down to the recent. Syringonautilidae is a strictly Triassic family, derived early in the Triassic from the

Grypoceratidae Grypoceratidae is the longest-lived family of the Trigonoceratoidea, or of the near equivalent Centroceratina; members of the Nautilida from the Upper Paleozoic and Triassic.Kummel,B. 1964. Nautiloidea-Nautilida, Treatise on Invertebrate Paleonto ...

.Kummel, 1964, K437-440

Diagnosis

The Syringonautilidae are characterized by generally involute shells - early whorls are in view - with broadly to sharply rounded whorl sections and smooth surfaces, except for growth lines and fine wire-like lirae in some forms. The

siphuncle The siphuncle is a strand of tissue passing longitudinally through the sh