Tarphyceratida Flower, 1950

Order Tarphyceratida Flower, 1950

Diagnosis (compiled after Furnish & Glenister 1964; Frey 1995; emended)

Multiceratoid cephalopods with coiled to gyroconic conchs of various whorl profile and simple transverse or slightly curved suture lines. Coiling planispiral, rarely torticonic; body chambers usually long, extending from a half to more than one complete whorl in length. Last whorl commonly slightly to greatly divergent from preceding coiled portions; terminal aperture commonly modified. Siphuncle varies in position; siphuncular segments more or less tubular, nautilosiphonate, with orthochoanitic or loxochoanitic septal necks and thick connecting rings in stratigraphically earlier forms, and cyrtochoanitic septal necks and thin homogeneous rings in stratigraphically later forms. Muscle attachment scars ventromyarian or sometimes pleuromyarian. Thin cameral deposits present in some taxa. Shell surface smooth or ornamented with transverse lirae, ribs or annuli, or spiral ornament elements.

Families included

Barrandeoceratidae Foerste, 1925 ; Estonioceratidae Hyatt in Zittel, 1900; Ophioceratidae Hyatt, 1894 ; Plectoceratidae Hyatt in Zittel, 1900; Tarphyceratidae Hyatt, 1894 ; Trocholitidae Chapman, 1857 .

Remarks

The combined diagnosis of Furnish & Glenister (1964) and Frey (1995) is expanded here to include the presence of pleuromyarian muscle attachment scars (e.g., Dzik 1984; King & Evans 2019) and cameral deposits ( Ulrich et al. 1942; Manda & Turek 2018) and the character of shell ornament.