1988  Nandanoceras Ruan (nom.nud.)
     1990  Ruanites Yatskov, p.28.
     1994  Ruanites.-Becker & House: 92.
     1996  Ruanites.-Ruan: 104.
     2001  Ruanites.-Klug: 487.
     2002  Ruanites.-Korn & Klug: 58.

Type species: Anetoceras obliquecostatum Ruan & He, 1974, p.238 [OD].

Serpenticonic shell, no touching whorls, separated coarse ribs and wide umbilicus (U/D> or = 2/3).

Klug, 2001, p.487: Conch of moderate to moderately large size, gyroconical and thinly discoidal, whorls loosely coiled. Very wide umbilicus with large umbilical window. Low to moderate whorl expansion rate (1.5 to 1.8) and whorl interspace rate of 1.1 to 1.4. Sculpture with coarse rursiradiate ribs and coarse growth lines. Suture line with a small external lobe, a widely rounded lateral lobe, and a shallow internal saddle.

Comparisons (Klug, 2001, p.487): Ruanites is used in the same sense as suggested by BECKER & HOUSE (1994). The conch is loosely coiled but with a moderate increase of the whorl interspace rate. From a phylogenetic point of view, Ruanites occupies an intermediate position between Anetoceras and Erbenoceras: Especially the distance between the whorls is characteristic; in contrast to the gyroconical Ruanites (WIR = 1.1-1.4), the whorls of Erbenoceras, on the one hand, are advolute (WIR = 1) except for the initial and the terminal whorl. Conchs of Anetoceras and Metabactrites, on the other hand, are more loosely coiled and at one stage, the distance between the whorls begins to grow more rapidly (WIR > 1.6). Additionally, most species of Erbenoceras have a lower number of ribs per whorl (mostly below 50). The majority of the Anetoceras and Metabactrites species have at least one growth stage with more than 100 ribs per whorl. This character also displays an intermediate state in Ruanites. Most species of this genus have 50 to 100 ribs per whorl.

A:   Conch gyroconic.
C:   50 - 100 ribs/whorl