Cretaceous; Ammonoidea: Kossmaticeratidae)

N. Jb. Geol. Paläont. Abh. 294/3 (2019), 307–310 Article E Stuttgart, December 2019

On the status of Kaiparaites Matsumoto, 1955 (Cretaceous; Ammonoidea: Kossmaticeratidae)

Michael R. Cooper With 1 figure

Abstract: The kossmaticeratid ammonite Kaiparaites was on its inception synonymized by its au- thor (Matsumoto 1955) with Natalites (Collignon 1954). However, close comparison of the type species of these two genera shows them to be morphologically and stratigraphically distinct. Whereas Santonian Natalites shares the flexed constrictions of late Turonian–Coniacian Kossmaticeras, the straight constrictions of late Campanian – Maastrichtian Kaiparaites are shared with Caledonites, Gunnarites, Grossouvrites and Jacobites. Consequently, Kaiparaites is resurrected from the synonymy of Natalites and demonstrates that, under phylogenetic consideration, characters first thought to be of prime taxonomic significance actually turn out to be secondary. Since treatment of Natalites as a subgenus of Kossmaticeras emphasizes primitive characters, it is returned to generic rank, as is Santonian Karapadites although, for those who find use for subgenera, the latter can be treated as a subgenus of Natalites.

Key words: Ammonoidea, Cretaceous, Kossmaticeratidae, phylogeny, Kaiparaites.

In 1955, Matsumoto described the kossmaticeratid Natalites in the same publication that he introduced it, ammonites from Hokkaido and Saghalien in which both diagnoses placing greatest taxonomic weight on he introduced the new genus Kaiparaites (type spe- the presence of umbilical bullae. This synonymy has cies: Madrasites multicostatus Marshall), diagnosed been upheld by all subsequent workers (Matsumoto as follows: “Similar to Kossmaticeras in shell-form 1956; Henderson 1970; Kennedy & Klinger 1985; and suture line. Small but prominent tubercles at the Matsumoto 1991; Wright 1996). umbilical edge; numerous, slightly flexuous or nearly Madrasites natalensis Spath was revised by Kenne- straight ribs, diverging from and also inserted between dy & Klinger (1985) who included it in the synony- the tubercles; constrictions well marked and prorsir- my of Holcodiscus africanus van Hoepen (1920: 146, adiate, cutting several ribs”. pl. 26, figs. 3–5) and treated it as a subgenus of Koss- Besides the type species, Kaiparaites was held to maticeras. This species is a compressed moderately- include also South African Madrasites natalensis evolute (U = 30–36 %) Santonian ammonite of me- Spath (1922: 134, pl. 5, fig. 3). In a postscript to his pa- dium size (adult at 81 mm diameter), with flattened per, introduced during the editorial stage, Matsumoto flanks thatconverge to a broadly-arched venter, a com- (1955) acknowledged receipt of Collignon’s (1954) pressed (W/H = 0.71–0.86) oval whorl section in later pre-emptive paper on the kossmaticeratids of Menabe, growth (>40 mm diameter), about 20 comma-shaped Madagascar, in which M. natalensis was made type umbilical bullae per whorl which give rise to bun- species of the new genus Natalites. This led Matsu- dles of 1–4 sharp, narrow, flexuous, prorsiradiate ribs moto (1955: 161) to synonymize Kaiparaites with which cross the venter with a broad forward convex-