Hildoglochiceras kobelli (Oppel, 1863b) morphotype kobelliforme (Bonarelli, 1894) (m)

Pandey, Dhirendra Kumar, Fuersich, Franz T., Alberti, Matthias, Das, Ranajit & Saez, Federico Oloriz, 2022, First population-level study of the ammonite genus Hildoglochiceras Spath, and the Lower Tithonian record of the Hildoglochiceras Horizon in the Kachchh Basin, India, Zitteliana 96, pp. 1-49 : 1

Hildoglochiceras kobelli (Oppel, 1863b) morphotype kobelliforme (Bonarelli, 1894) (m)

Figs 6P-T , 8F, G , 9A-C, G, H

Harpoceras kobelli Oppel, 1875 - Waagen: 72, pl. 13, fig. 12a, b (non figs 11, 13 by Bonarelli 1894).

Hecticoceras (Lunuloceras) kobelliforme sp. nov., 1894 - Bonarelli: 95, 96.

Hildoglochiceras kobelliforme (Bonarelli), 1928 - Spath: 159, pl. 13, fig. 17.

Hildoglochiceras kobelli Oppel, 1960 - Collignon: pl. 143, figs 547-550.

Hildoglochiceras sp. aff. kobelliforme (Bonarelli), 2009 - Énay: 84, pl. 1, fig. 6a, b.

Material.

23 specimens, Hildoglochiceras Bed of Jara Dome ( Lower Tithonian ); KSKV2019 Jara /1-9, 21, 26, 32, 41, 45, 46, 48-51, 54, 55, 74, 75, KSKV2020 Jara /15 .

Description.

Shell small consting of both phragmocone and body chamber with maximum shell diameter of ca. 50 mm (KSKV2020Jara/15), nearly complete, discoidal, compressed and evolute. Whorl section narrow subtrigonal to oval with narrow venter. Lateral sulcus at lower one-third of lateral height to mid-lateral height, wide, and terminates just above the base of the ventral branch of the peristome. Lateral surface flat, ornamented with faint sickle-shaped (falciform) ribs on the body chamber (e.g., KSKV2019Jara/1). A shallow spiral groove situated at one-third to one-half of the flank height of both phragmocone and body chamber. Spiral groove gradually changing in width with growth. Lower boundary of spiral groove higher than upper boundary (Fig. 6R, S ), coinciding with maximum shell thickness. Inner, dorsal one-third of body chamber, i.e. area below the spiral groove, sloping towards umbilical seam with broadly arched umbilical shoulder region and steep umbilical wall. Peristome with lappets preserved. Suture lines well preserved, with denticulated lobes and saddles. Lobes slightly narrower than saddles (Fig. 6Q ). First lateral lobe deep, moderately broad, with three short branches at the end. Second lateral lobe much shorter. At least two auxiliary lobes above the umbilical suture. First (external) saddle broad and short, with small secondary lobes. The last two suture lines are very close, almost touching.

Figures

Figure 6. A-G, L-N. Haploceras staszycii (Zeuschner, 1846). A. KSKV 2019 Jara / 63, left side view of phragmocone, note well preserved suture lines; B, C. KSKV 2019 Jara / 64; B. Left side view of phragmocone; C. Apertural view showing broken aperture along a septum; D. KSKV 2019 Jara / 66, apertural view; E. KSKV 2019 Jara / 69, apertural view showing broken surface along a septum; F, G. KSKV 2019 Jara / 62; F. Left side view of phragmocone, note well preserved suture lines; G. Apertural view; L-N. KSKV 2019 Jara / 61; L. Right side view of phragmocone; M. Apertural view; N. Outline of whorl-section; H-K, O. Haploceras sp.; H, O. KSKV 2019 Jara / 65; H. Apertural view along a broken surface of phragmocone; O. Right side view showing phragmocone and a part of body chamber; I-K. KSKV 2019 Jara / 67; I. Vental view; J. Apertural view; K. Left side view of body chamber; P-T. Hildoglochiceras kobelliforme (Bonarelli, 1894) (m); P-S. KSKV 2019 Jara / 1, inner cast with epigenized shell preserved; P. Right side view of moderately evolute specimen (U ≈ H), with subtle uncoiled outer whorl (probable adult), body chamber 180 ° with peristomal vestige (dorsal branch on inner cast?); Q. Suture lines at the end of phragmocone, note increased density at the end of phragmocone; R. Apertural view, note epigenized shell clearly identifiable on the ventral region; S. Oval whorl section with narrow venter, wide lateral groove on the body chamber; T. KSKV 2019 Jara / 2. inner cast, left-side view of nearly complete adult specimen with clear final uncoiling, partial preservation of epigenized shell, ca. 180 ° of preserved body chamber on inner cast of comparatively fine-to-medium sandstone.

Figure 8. A-E, H-L. Hildoglochiceras kobelli (Oppel, 1863 b) (M); A, B. KSKV 2019 Jara / 42. A. Left side view showing phragmocone and part of body chamber; B. Right side view showing phragmocone and part of body chamber, note on both sides spiral grooves are developed even at a diameter less than 10 mm; C, D. KSKV 2019 Jara / 39; C. Left side view; D. Right side view, bothshowing phragmocone and beginning of body chamber, presence of spiral groove even at diameter less than 10 mm and closely spaced crescentic ribs along the periphery towards the end of phragmocone, note beginning of crescentic ribs shown by triangles; E. KSKV 2019 Jara / 40, right side view of a tiny (diameter ca 4 mm) specimen showing phragmocone and a part of body chamber. Note absence of spiral groove but presence of crescentic rib at dimeter less than 4 mm; H, I. KSKV 2020 Jara / 12. H. Left side view; I. Right side view, showing a large part of body chamber perhaps up to peristome. Note on both sides spiral groove on the body chamber closely spaced crescentic ribs. Note remains of the shell at umbilical shoulder and along spiral groove. This suggests present-day erosion. J-L. KSKV 2020 Jara / 11; J. Apertural view; K. Ventral view; L. Right side view showing end of phragmocone and body chamber. Note on spiral groove on the body chamber and closely spaced crescentic ribs. F, G. Hildoglochiceras kobelliforme (Bonarelli, 1894) (m) KSKV 2019 Jara / 32; F. Left side view; G. Right side view, both showing phragmocone and a part of body chamber, presence of a wide spiral groove. Note traces of ribs both near the end of phragmocone and in the beginning of the body chamber; M. Close up view of upper surface of the lower most part of the Hildoglochiceras bed which is coarse grained micritic sandstone showing juvenile Hildoglochiceras and haploceratids.

Figure 9. A-C, G, H. Hildoglochiceras kobelliforme (Bonarelli, 1894) (m); A. KSKV 2019 Jara / 3, inner cast, right side view of abraded, moderately evolute (U ≈ H) adult specimen with clear final uncoiling. Specimen without remains of epigenized shell and showing recrystallized phragmocone with last two suture lines slightly approached. Body-chamber 180 ° with sandy infilling including coarse to very coarse grains. Fading of lateral groove due to abrasion. B, C. KSKV 2019 Jara / 8; B. Inner cast, left-side view of a part of body chamber showing moderately deep lateral groove; C. Oval whorl section with narrow venter and a wide, moderately deep lateral groove; G. KSKV 2019 Jara / 9, internal cast with remains of epigenized shell, right-side view of comparatively evolute (U ≈ H), small specimen showing comparatively long body-chamber (> 180 °) with wide, moderately deep lateral groove unidentifiable on the phragmocone. Note remains of epigenized shell in the anterior body chamber, probable partial preservation of peristome with basal part of broken lappet, and sandy infilling. right side view; H. KSKV 2019 Jara / 4, internal cast, right side view of a part of body chamber (U ≈ H) showing shallow to moderately deep wide lateral groove; D-F, I. Hildoglochiceras kobelli (Oppel, 1863 b) (M); D-E. KSKV 2019 Jara / 11, internal cast; D. Apertural view; E. Anterior and left-side views of fragmented, comparatively involute specimen (U << H) with high-oval outer whorl, showing abraded right-side with wide, shallow spiral groove on the preserved last septum of phragmocone and body chamber, better developed on the latter. Internal cast of outer whorls filled with calcareous fine-grained sandstone, inner whorls recrystallized. Note shell is completely eroded. F. KSKV 2019 Jara / 10, internal cast with remains of epigenized shell, right-side view of comparatively involute specimen (U << H) showing ca. one-third of body chamber with wide, shallow lateral groove that is imperceptible on the phragmocone of the outer whorl. Coarser, sandy infilling occupying the body chamber; I. KSKV 2019 Jara / 81, whorl section of involute specimen of a large size with high-oval to acute outer whorl and extremely narrow venter.