Dutta and Bardhan—Jurassic ammonite taxonomic corrections
Subgrossouvria aberrans. This specimen is actually the holotype of Waagen’s Perisphinctes spirorbis (non Neumayr), which Spath (1931) described as Indosphinctes indicus (Siemiradzki, 1899). Arkell et al. (1957, p. L319) were so influenced that they provided the generic diagnosis of Subgrossouvria (Spath, 1924) based on the holotype of Indosphinctes indicus (Siemiradzki, 1899). Subsequently many workers of the twentieth century and
recent, reported Subgrossouvria from other regions, and they perhaps compared their forms with the incorrect figure of the holotype of P. aberrans Waagen, 1875. For example, Gerard and Contaut (1936), Callomon (1963), and Bonnot et al. (2014) treated Subgrossouvria as a distinct genus. Elmi (1962) con- sidered Subgrossouvria as a macroconch subgenus within Choffatia (Siemiradzki, 1898). Mangold (1971) also included Subgrossouvria as a subgenus of Choffatia and described several species from the late Bathonian and early Callovian of France. Both Elmi (1962) and Mangold (1971) included the Bathonian genus Loboplanulites Buckman, 1925 as a junior synonym of Subgrossouvria. In Kutch, species of Subgrossouvria come only from the Callovian (Spath, 1931). Cox (1988) synonymized Subgrossouvria with Choffatia. The different taxonomic assignments of Subgrossouvria may be attributed to confusing ideas based on the incorrect figures of Waagen (1875) and Arkell et al. (1957).
Materials and methods
Wehave recently revisited Waagen’s original specimens of both true Subgrossouvria aberrans and Indosphinctes indicus, which are archived in Geological Survey of India (GSI), Kolkata, India. These are illustrated here (Fig. 1). Waagen’s figures were actually drawings made by an artist, and Spath (1931), while introducing the new genus Subgrossouvria, did not illustrate the holotype of the type species. Therefore, this is the first time the photographs of the holotype of Waagen’s P. aberrans have been made available (Fig. 1.1–1.3). We have also provided the original photographs of Indosphinctes indicus for comparison (Fig. 1.4–1.6). The descriptions of the type specimens and diagnoses for the two genera are also given below.Weare aware that the Treatise of Jurassic ammonites is undergoing revision by the coordinating editor M.K. Howarth and his colleagues. We bring to their attention this historical error.
Systematic paleontology
Phylum Mollusca Linnaeus, 1758 Class Cephalopoda Cuvier, 1795 Order Ammonoidea Zittel, 1884
Family Perisphinctidae Steinmenn, 1890 Genus Subgrossouvria Spath, 1924
Type species.—Perisphinctes aberrans Waagen, 1875.
Diagnosis.—Macroconch large (maximum adult phragmocone diameter 165 mm); strongly evolute and generally depressed. Inner whorls with rounded flanks, which are finely and densely ribbed and have constrictions; ribs later become coarser and
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distant; mostly bifurcating secondaries with furcation taking place at the outer flank; ribs prorsiradiate, may be rursiradiate; secondaries unlike Choffatia are stronger than primaries. Species mostly represented by phragmocones; in adult phragmocone, secondaries may disappear and primaries are present as bullae-like ridges. Microconchs replicate inner whorls of macroconchs in degree of involution, inflation, and style of ornamentation and lappeted.
Occurrence.—England, France, Poland, Somalia, Kenya, Tanzania, Madagascar, Iran, Kutch (India), and Mexico.
Subgrossouvria aberrans (Waagen, 1875) Figures 1.1–1.3, 2.1
1875 Perisphinctes aberrans Waagen, pars, p. 175, pl. 41, figs. 1a–c.
1899 Perisphinctes aberrans Waagen; Siemiradzki, p. 305. 1924 Subgrossouvria aberrans (Waagen); Spath, p. 13. 1930 Subgrossouvria aberrans (Waagen); Spath, p. 40. 1931 Subgrossouvria aberrans (Waagen); Spath, p. 374, pl. 64, fig. 8.
Lectotype.—Geological Survey of India (GSI) type no. 2045. The genotype is the species S. aberrans, to be interpreted by its syntype, which were the examples figured by Waagen (1875, pl. 41, figs. 1 and 2), from which the larger specimen (Fig. 1.1–1.3) has been chosen as the lectotype.
Occurrence.—Upper Callovian; Keera in the mainland of Kutch.
Description.—The lectotype is represented by mostly internal mold. Specimen is large, septate (maximum preserved diameter is 165mm), strongly evolute (the ratio between the umbilical diameter and the shell diameter of the specimen, U/D, is 0.58) and depressed (the ratio between the whorl width and the whorl height, W/H, is 1.1). Inner whorls are missing. In the middle whorls, flanks are curved with numerous strong and dense primary ribs (P = 19 per half whorl at ~ 83mmdiameter), which are prorsiradiate in nature. At this stage, primaries are long and secondary ribs are not visible. Shell is characterized by deep, prorsiradiate constriction at ~91mm diameter. Primaries become strong with sharp crest and distant after the constriction. At 137mm diameter, primaries are 11 per half whorl and
reduce to 9 at the outer half whorl at diameter 165mm. Secondary ribs, which are first exposed at ~ 140mm diameter, are short, two in number, and originate from the outer flank. There are short intercalatory ribs between two primary ribs. Both secondary and intercalatory ribs are feeble on the internal mold and disappear soon, rendering the venter smooth. Primary ribs become stronger during ontogeny and are present throughout the preserved end. Towards the end, primary ribs become obsolete near the umbilical margin and form elongated bullae-like ridges at the mid-flank. Body chamber missing, but from the trace of the umbilical seam, it appears to be short and occupies less than half of the outer whorl.
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