Hoploscaphites Nowak, 1911

Landman, Neil H., Kennedy, W. James, Larson, Neal L., Grier, Joyce C., Grier, James W. & Linn, Tom, 2019, Description Of Two Species Of Hoploscaphites (Ammonoidea: Ancyloceratina) From The Upper Cretaceous (Lower Maastrichtian) Of The U. S. Western Interior, Bulletin of the American Museum of Natural History 2019 (427), pp. 1-72 : 22

Genus Hoploscaphites Nowak, 1911

[= Mesoscaphites Atabekian, 1979: 523 (nomen nudum) fide Kennedy, 1986; Wright, 1996; Jeletzkytes Riccardi, 1983: 14 ].

TYPE SPECIES: Ammonites constrictus J. Sowerby (1817: 189 , pl. A, fig. 1), by original designation.

DIAGNOSIS: “Small to large scaphites, strongly dimorphic, with broad variation in degree of whorl compression ranging from slender to robust, with involute phragmocone, short to long shaft, and weakly recurved hook; apertural angle ranging from approximately 35° to 85°; aperture constricted with dorsal projection; ribs straight to flexuous, increasing by branching and intercalation, with weak to strong adoral projection on venter; adult shell with or without umbilicolateral, flank, and ventrolateral tubercles; suture fairly indented, with symmetrically to slightly asymmetrically bifid first lateral lobe” ( Landman et al., 2010: 93).

DISCUSSION: In their monograph on the scaphites of the “ nodosus group,” Landman et al. (2010) treated Jeletzkytes Riccardi, 1983 , as a junior subjective synonym of Hoploscaphites . They argued that the shape of the shell, the pattern of ornamentation, and the complexity of the suture are the same in both genera, the only differences being the degree of compression and, as a result, the flexuosity of the ribs and the size of the tubercles. They noted that such variation already exists within the genus Hoploscaphites , as previously defined, and exemplified by the type species H. constrictus . Wright (1996: 261–262) cited the same reason for synonymizing the two genera: “Separation of the large and inflated species of the nodosus group as Jeletzkytes seems unnecessary, given the great variation within most scaphitid species.” Later, Cooper (1994) erected the new subgenus Karlwaageites for derived members of Jeletzkytes from North America that bear lateral tubercles. However, the number and distribution of lateral tubercles can vary even within a single species, casting doubt on the utility of this character for subgeneric separation. Until a thorough phylogenetic revision of all scaphitid genera and subgenera is undertaken, we prefer to follow a more conservative approach and treat all these species in the genus Hoploscaphites .