Hildoglochiceras kobelli (Oppel, 1863b) morphotype kobelli Oppel (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 kobelli Oppel (M)

Figs 8A-E, H-L , 9D-F, I

Ammonites kobelli sp. nov., 1863b - Oppel: 273, pl. 76, figs 1a-c, 2a, b.

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

Glochiceras deplanatum (Waagen), 1928 - Spath: 155, pl. 16, fig. 3, pl. 17, figs 9a, b.

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

Hildoglochiceras nudum sp. nov., 1960 - Collignon: pl. 145, fig. 567.

Material.

48 specimens, Hildoglochiceras Bed of Jara Dome ( Lower Tithonian ); KSKV2019 Jara /10-16, 19, 20, 22-25, 27-31, 33-40, 42-44, 47, 52, 53, 56-60, 70-73, 76-78, 81, KSKV2020 Jara /11, 12, 14 .

Description.

Shell moderately large, consting of both phragmocone and body chamber with maximum shell diameter of ca. 95 mm (KSKV2020Jara/14), 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. Lateral surface flat, ornamented with sickle-shaped (falciform) or crescentic ribs, also seen on the juvenile specimens (Fig. 8A-E, H-L ). The beginning of ribs variable, may start at a diameter less than 10 mm or even at diameter less than 4 mm. 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. Spiral groove begins at a diameter less than 10 mm. Lower boundary of spiral groove higher than upper boundary, coinciding with maximum shell thickness. Inner, dorsal one-third of body chamber i.e., area below the spiral groove, flattened with obtusely rounded umbilical shoulder and steep to almost vertical umbilical wall (Fig. 10I ). Suture lines moderately well preserved.

Remarks.

The specimens are moderately preserved and abraded. In some cases, they consist of phragmocone and almost a complete or a part of body chamber, in few cases (e.g., KSKV2019Jara/1, 5) half a whorl of body chamber (180°) with preserved aperture. Several specimens are very small with their body chambers preserved. They are juveniles (e.g., KSKV2019Jara/39-44). The specimens represent internal moulds, i.e., without shell material and ventral keel, even in the smaller specimens. The ornamentation is mostly no longer preserved, similarly, the wide and moderately deep lateral groove in some cases is partially preserved on the body chamber, but unidentifiable in the phragmocone.

The morphological features described above match Hildoglochiceras Spath, 1924. The general absence of population size analyses of species described in the literature impedes their precise interpretation in terms of intra-species variability. Hence, the maintenance of species names is obligatory in the present analysis.

The dimensional proportions of different species of Hildoglochiceras Spath, 1924 described from the Indo-Malagasy faunal province by the earlier workers suggest comparable H/D, T/D and H/T ratios (H/D: 33-45%; T/D: 21-28%; H/T: 1.32 to 1.8). However, U/D ratio is increasing from 29 to 42% (Table 3 ), except for few specimens that should be rechecked for their measurements and/or identification. Interestingly, in the present collection, shell diameter and the diameter of the umbilicus distinctly show two groups; type 1: small shell diameter with large umbilicus (U/D: 40 to 25%) and type 2: large shell diameter with small umbilicus (U/D: 26 to 18%). H/T is smaller (1.3-1.8) in type 1, whereas it is greater (1.35-2.0) in type 2 (Table 4 ). In general, WSG and HSG show a trend of values increasing with shell size. Based on similarity in morphological features type 1 is considered here as microconch (small shell diameter and larger umbilical diameter) with lappets (only their bases are preserved just below the adapertural end of the lateral groove (Figs 6P , 8F ), and type 2 as macroconch (large shell diameter and smaller umbilical diameter) without preserved peristome. However, both types are also represented by juvenile specimens (e.g., KSKV2019Jara/39-44).

Hildoglochiceras latistrigatum (Uhlig, 1903) matches present specimens in having a similar shape including whorl section and a maximum width along the lower lip of the lateral groove, but has a wider umbilical diameter ( Uhlig 1903: 27, pl. 2, fig. 4; pl. 3, fig. 5; Pandey et al. 2016: 146, pl. 1, fig. 2a, b). Lacking data at the population level, no conclusion about the meaning of this difference can be drawn. The species has been reported ornamented with distant sickle-shaped ribs and growth striations, however, the ornamentation is variable and inner whorls are smooth.

Uhlig (1903: 28), while describing his new species Hildoglochiceras latistrigatum , mentioned that the growth striations follow a similar pattern as in H. kobelli . Further he mentioned H. latistrigatum "approximates very closely to H. kobelli " Oppel but the differences between the two species make it impossible to merge them (Table 5 ). In fact, most of the characters mentioned are relative and thus are not tenable when several specimens are compared. Nevertheless, of several differences mentioned by Uhlig, the present specimens are closer to Hildoglochiceras latistrigatum in ornamentation. Unfortunately, Uhlig did not mention a larger diameter of the umbilicus in H. latistrigatum in comparison to H. kobelli , which is one of the distinctive characters.

The line of maximum inflation either along the upper or lower margin of the spiral furrow cannot be a distinguishing feature between H. kobelli and H. latistrigatum , because in one of the figures of H. kobelli from Madagascar ( Lemoine 1910: 146, pl. 4, figs 1-4, and apertural view figured at https://science.mnhn.fr/institution/mnhn/collection/f/item/r02008) it is clearly along the lower margin of spiral furrow. In juvenile forms (KSKV2019Jara/30, 40, 42), the elevation of the lower boundary of the spiral groove, whether higher or lower than upper boundary, may not be ascertained.

The morphological characters in the present specimens match Harpoceras kobelli Oppel ( Waagen 1875: 72, pl. 13, fig. 12, non figs 11, 13), from the "Upper Katrol Group", south-west of Nurrha, in having similar proportional dimensions, but differ in having the maximum thickness of the whorl along the upper boundary of spiral groove, instead of along its lower boundary. Spath ( 1928: 159, pl. 13, fig. 17) mentioned the observation of Waagen (1875: 73, pl. 13, figs 11-13) and Lemoine ( 1910: 10 pl. 4, fig. 1-4) that H. kobelli Oppel is a very variable species with respect to the start of crescentic ribs (at a diameter of 25 mm or 30 mm or even later), number and sharpness/thickness of ribs and width of lateral groove, which gradually widens with growth. The present specimens match well with such observation (Fig. 8C-E, H, I, K, L ). According to Lemoine ( 1910: 10), H. kobelliforme (Bonarelli) and H. latistrigatum (Uhlig, 1903) are mere varieties of the same species. In fact, Lemoine ( 1910) was pioneer in highlighting the identification of the great variability within Hildoglochiceras . According to Lemoine, H. kobelliforme has an "abrupt margin of the shell", perhaps he meant an abrupt umbilical edge, H. latistrigatum shows a very wide furrow and H. kobelli has a less abrupt edge of the shell and a narrower furrow.

According to Spath ( 1928), H. kobelli Oppel and H. kobelliforme (Bonarelli) are morphologically similar. Further, Spath synonymised one of the specimens of Waagen (year) assigned to Harpoceras kobelli Oppel ( Waagen 1875: 72, pl. 13, fig. 12) with Hildoglochiceras kobelliforme (Bonarelli). The suture line of this specimen ( Spath 1928: 159, pl. 13, fig. 17) matches the suture lines of the present specimens. The other two specimens figured by Waagen as Harpoceras kobelli (Oppel) ( Waagen 1875: 72, pl. 13, figs 11, 13) show either a lateral groove closer to umblical shoulder or a more transversely ovate whorl section.

Oppelia plana Waagen (1875: 56, pl. 11, fig. 3) from the "Katrol Group" (Kimmeridgian), south-west of Nurrha, is another comparable species with respect to its discoidal shape, proportional dimensions including umbilical diameter, smooth flanks with wide lateral groove and suture lines [see Hildoglochiceras? planum (Waagen) ( Spath 1928: 160-161, pl. 19, fig. 5) at a diameter of 20 mm of Waagen’s holotype (1875: 56, pl. 11, fig. 3) to Hildoglochiceras kobelliforme (Bonarelli)], but it has an oval whorl section with a rounded ventral region. Moreover, the present specimens are sculptured. The possibility of obliteration of ribs of the body chamber prior to final burial or general due to poor preservation due to weathering cannot be ruled out, especially as the matrix is a calcareous coarse-grained sandstone. Moreover, some doubts arise about the type described by Waagen (1875) since this author indicated "specimen with body chamber" in his figure caption, while Spath ( 1928, p. 160) stated that the “… fragmentary example described by Waagen is entirely septate and represents the inner whorls of a larger form, probably of the Hildoglochiceras kobelli group entirely septate there …”. The Madagascan specimens assigned to Hildoglochiceras planum (Waagen) ( Collignon 1960: pl. 144, figs 558-560) are very close to Hildoglochiceras kobelliforme (Bonarelli), if the smooth shells are a result of abrasion or due to preservation like in most of the present specimens. Spath ( 1928: 160) raised doubts about species level separation of Haploceras (Hecticoceras) spira Zwierzycki from Tendaguru, Tanzania ( 1914: 49, pl. 5, figs l l -13) from H. kobelliforme Bonarelli. Based on morphological similarity and dimensional proportions (Table 3 ) including the umbilical diameter, the specimens assigned to Hildoglochiceras kobelli Oppel by Collignon (1960: pl. 143, figs 547-550) are identified as H. kobelliforme Bonarelli herein. Hildoglochiceras nudum Collignon (1960: pl. 145, fig. 567; D: 43, H: 19 (44), T: 12(28), U: 10 (23)) is similar in discoidal shape, presence of a feeble spiral groove and dimensional proportions including umbilical diameter to the present specimens assigned to H. kobelli Oppel, which is a macroconch. From the illustrations ( Collignon 1960: pl. 143, fig. 567) ribs along the periphery can be clearly seen. In all probability Hildoglochiceras nudum Collignon is a junior synonym of H. kobelli Oppel. Similarly, Glochiceras deplanatum (Waagen) ( Spath 1928: 155, pl. 16, fig. 3, pl. 17 figs 9a, b) shows a comparable discoidal shape, lateral spiral groove, peripheral ornamentation and proportional dimensions including a similar umbilical diameter ( Spath 1928: pl. 17, fig. 9; D: 70, H/D: 45 T/D: 24, U/D:·24; pl. 16, fig. 3; D: 67, H/D: 44, T/D: 25, U/D: 24) to the present specimens assigned to H. kobelli Oppel (1863b).

Contextually, the Madagascan taxa H. planum (Waagen) ( Collignon 1960) (m), Haploceras (Hecticoceras) spira Zwierzycki (1914) (m), H. nudum Collignon (1960) (M), and Glochiceras deplanatum (Waagen) (Spath1928) (M) may be individuals of the dimorphic pair of the species discussed here, based on the assumption of a wide intra-species variability affecting mainly, but not exclusively, the lateral and ventral sculpture. This is in accord with the interpretation made by Collignon (1960) of the species Hildoglochiceras kobelli Oppel, including his new var. madagascariensis , and contrasts with his generally typological approach resulting in species-rich ammonite assemblages.

Hildoglochiceras sp. aff. kobelliforme (Bonarelli) ( Énay 2009: 84, pl. 1, fig. 6a, b) shows similar dimensional proportions, and occlusion of the lateral groove in the umbilicus, but the sculpture is well developed.

Data from Pakistan are difficult to evaluate due to their poor preservation ( Hildoglochiceras sp. ind. group of Hildoglochiceras propinquum Waagen sp.; Spath 1939, pl. 18, fig. 8a, b) and the lack of body chamber ( Hildoglochiceras cheemaensis Fatmi, 1973, pl. 3, figs 10-12). The latter is a large, septate form that, at equivalent shell size, shows a similar whorl height, but a lower degree of coiling in comparatively flattish, narrower shells with smooth phragmocone, a wide lateral groove below the line of whorl overlapping showing an inner, crescentic edge, and decreasing depth adaperturally, and a low arched, wide venter without keel.

Concerning the species under study, scanning through descriptions and figures of the species mentioned above given by earlier workers ( Oppel 1863b; Waagen 1875; Bonarelli 1894; Uhlig 1903; Lemoine 1910; Spath 1928; Collignon 1960; Énay 2009: pl. 1, fig. 6a, b), it is evident that H. kobelli (Oppel), H. kobelliforme (Bonarelli), and H. latistrigatum (Uhlig) are morphologically very close. In view of the larger umbilical diameter of H. latistrigatum (Uhlig), the present specimens have been assigned to the H. kobelli (Oppel) (M) and H. kobelliforme (Bonarelli) (m) group. It may be mentioned here that Énay (2009: 84, pl. 1, fig. 6a, b), in the description of Hildoglochiceras sp. aff. kobelliforme (Bonarelli), mentioned it as Hildoglochiceras cf. kobelliforme (Bonarelli) in the caption on page 248. The statistical analysis of Hildoglochiceras is given in chapter 5 (see below).

Biostratigraphy.

Uhlig (1903, 1910) described the species of Hildoglochiceras from the Spiti Shales at Chidamu in the Himalayas of northern India. According to Spath ( 1933: p. 673), Hildoglochiceras latistrigatum ( Uhlig 1903) from Spiti may be associated with the Aulacosphinctoides fauna (for the Natricoides Subzone see Pandey and Krishna 2002; Pandey et al. 2010), which had almost disappeared when Virgatosphinctes became dominant in the Early Tithonian.

Data from Spath (1939) and Fatmi (1972, 1973) indicate a generalized context of unconclusively known reworking in Pakistan. Limitations of the precise biostratigraphic interpretation of the Hildoglochiceras -rich horizon relates to the near-absence of precise information on Hildoglochiceras in particular sections and stratigraphic horizons elsewhere. In fact, despite usual correlations (since Uhlig 1903), the stratigraphic range of Hildoglochiceras ( H. kobelli Oppel and related species) is inconclusively known, as rightly pointed out repeatedly by previous authors (e.g., Arkell 1956; Zeiss 1968; Énay 2009), or it is given as tentative in the most recent interpretation ( Krishna 2017).

The biostratigraphic interpretation of the described Hildoglochiceras horizon is supported by the combination of local and region-wide observations (see above): (1) the absence of physical, stratigraphic features compatible with a wide stratigraphic gap in the section studied, but it could be inconclusive; (2) the local occurrence of transient forms between Neochetoceras and the Semiformiceras darwini Neumayr group in Nepal, the combined record of Hildoglochiceras and Paraboliceras in Himachal Pradesh (Spiti region, Himalaya), as well as by its rare record and tentative assignment to the lower part of the Virgatosphinctoides Zone at the Lakhapar section, Kachchh ( Krishna et al. 1996); and (3) the common relationship between Hildoglochiceras horizons and transgressive pulses on epicontinental shelves across opposite palaeomargins of the Trans-Erythraean Through (India and Madagascar versus Tanzania). In this context, the present interpretation is compatible with the possibility of imprecisely known biostratigraphic differences between horizons of Hildoglochiceras from separate areas of the Tethyan embayment corresponding to the proto-Indian Ocean. An example of this can be the early report made by Waagen (1875) on his Haploceras propinquum Waagen - later interpreted as Hildoglochiceras (from Spath 1933 to Énay 2009) - as coming from the lowest beds of the Katrol Group, just above "oolitic deposits with Asp. perarmatum at the Keera Hill near Charee". At first, this record would refer to the Kimmeridgian Group he correlated with Europe. This report would point to the Middle Kimmeridgian i.e., to the Eudoxus-Steraspis stratigraphic interval, according to Spath ( 1928), hence indicating records of the genus Hildoglochiceras older than usually interpreted, just above the stratigraphic gap envisaged by Spath ( 1933: table 1) for Kachchh. In addition, it may be noted that Paralingulaticeras -like forms resembling the groups of P. nodosum Berckhemer- P. parcevali Fontannes (subtly sculptured forms without and with lateral groove, respectively) and P. lithographicum Oppel (coarsely sculptured forms) are west Tethyan equivalents of comparatively stout shells of Paraglochiceras described and illustrated by Collignon (1960) from Kobelli Zone in Madagascar. These stouter forms are typical Madagascan “species”, when compared to west Tethyan equivalents.

In accordance with the biostratigraphic interpretation of the taramelliceratin phragmocone described herein and the review of interpretations of Hildoglochiceras records by paying attention to palaeoenvironmental and stratigraphic contexts, two Lower Tithonian intervals related to transgressive pulses are considered. These correlate with the upper to uppermost Hybonotum-lowermost Albertinum/Darwini Zone, and with the lower Semiforme/Verruciferum Zone in the European Standard Scale, respectively. The former would agree with the record of forms intermediate between Neochetoceras and early Semiformiceras , and it would be compatible with the occurrence of Parastreblites during a regression before the subsequent lowstand characterizing deposits corresponding to the Albertinum/Darwini Zone interval. The second would point to an increasing sea level after Albertinum/Darwini times during the younger range of Parastreblites . Older (latest Kimmeridgian) and younger (post-Semiforme/Verruciferum Zone) time intervals are discounted due to the lack of evidence of a wide stratigraphical gap below the Hildoglochiceras horizon in the section studied.

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.

Figure 10. Sketch diagrams of four types (Type 1 to 4) of specimens assigned to Hildoglochiceras kobelliforme (Bonarelli) (m) and Hildoglochiceras kobelli (Oppel) (M). Type 1 - with large umbilicus, compressed whorl section and acute venter (m). Type 2 - with small umbilicus and compressed whorl-section with acute venter (M). Type 3 - small-sized specimens, juvenile of types 1 & 2. Type 4 - are same as Type 2 but with preserved crescentic ribs on flanks.

Figure 14. Principal Component Analysis (PCA). Based on their morphological similarities all specimens at the author's disposal were manually grouped into four types, Type 1 to Type 4; a. PCA for non-imputed dataset (N = 59) using ' prcomp ' command in R employing the normalized data; b. PCA for the imputed data set (N = 105). Note Type 1 (Circle) - with large umbilicus (U / D: 40 to 25 %), compressed whorl section (H / T: 1.3 - 1.8) and acute ventral region. They are microconch (m); Type 2 (Triangle) - with small umbilicus and (U / D: 26 to 18 %), compressed whorl-section (H / T: 1.35 - 2.0) and acute ventral region. They are macroconch (M); Type 3 (Diamond) - small-sized specimens, juvenile of types 1 & 2. The overlap of types 3 and 1 & 2 in the plot suggests that they belong to same taxonomic group. Type 4 (Square) - they are same as Type 2 but with preserved crescentic ribs on flanks.