Blaschkeiceras schoepflini ( Blaschke, 1911 ) (Macroconch)
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publication ID |
https://doi.org/10.1186/s13358-025-00380-7 |
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persistent identifier |
https://treatment.plazi.org/id/03B187E6-FFDF-FF98-FF23-FEB7FAF1F8BF |
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treatment provided by |
Felipe |
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scientific name |
Blaschkeiceras schoepflini ( Blaschke, 1911 ) (Macroconch) |
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Blaschkeiceras schoepflini ( Blaschke, 1911) (Macroconch)
Figure 3 View Fig
1911 Perisphinctes ( Aulacosphinctes) Schöpflini Blaschke , p. 76, pl. 4, Fig. 1 View Fig ( holotype).
2001 Blaschkeiceras schoepflini – Zeiss, p. 42, pl. 9, figs. 1‒4, text-figs. 3‒4.
2017 Blaschkeiceras schoepflini – Vašíček et al., p. 588, Fig. 4C‒E View Fig .
Materials
Two specimens; SJ/JA-RU/1983/3 (M; Fig. 3A‒C View Fig ) and SJ/ JA-RU/1983/4 (M; Fig. 3D‒G View Fig ) from bed Jb7, Bhadasar Section ( 27°06 ′ 07.2"N 70°46 ′ 41.3"E; Jaisalmer , India) ( Fig. 2B View Fig ) GoogleMaps .
Measurements
Description: SJ/JA-RU/1983/3 ( Fig. 3A‒C View Fig ): Shell medium-sized (93.5 mm; maximum estimated shell diameter of 156 mm, assuming the body chamber to be 2/3rd) with part of the body chamber preserved. Shell evolute (U/D = 0.52) and compressed (T/H = 1.0). Biplicate ribbing ends at 83 mm, and then virgatotome (virgatipartite) ribbing starts. Although only a fraction of the spur (the remains of the previous whorl) is preserved in the specimen (see Fig. 3A View Fig ), suggesting that the exposed part is the outermost whorl, nevertheless, it lacks a further ribbing stage (with 4 secondaries with a single rib; see Zeiss, 2001, pl. 9, Figs. 2 View Fig , 3 View Fig ). Te phragmocone measures 73 mm ( Fig. 3A View Fig ).
Te early whorls ( 0‒24 mm; 0‒10 mm not preserved) show radial, sharp, sparsely spaced, and crested biplicate ribbing, with a rare single simple rib in between. Te ribs are straight and slightly forwardly inclined (prorsiradiate). Te rib furcation is at the upper third of the flank, which gradually progresses to the mid-flank in the middle whorls and to the lower third of the flank in the outermost whorl. Umbilicus is wide, shallow and with a rounded umbilical edge; ribbing arises from below the rounded umbilical edge. Te umbilical walls remain vertical throughout ontogeny. Tere are ~ 18 primaries with ~ 2 simple ribs per half whorl. A single constriction is noted that runs parallel to the ribbing.
Te middle whorl ( 25‒60 mm) does not show much change in the ribbing pattern except that the rib spacing becomes more distant, with ~ 17 primaries and~ 4 simple ribs per half whorl. Te ribbing continues to be sharp, crested, and biplicate. Te rib furcation now shifts somewhat lower towards the mid-flank. Te secondaries become more prorsiradiate and cross the broadly rounded venter with a slight curve. Te flanks are slightly arched with a maximum thickness at the mid-flank. A single constriction runs parallel to the ribbing.
Te outer whorl ( 61‒94 mm) is characterized by a distinct change in the ribbing pattern from biplicate via polygyrate ribbing to a virgatipartite arrangement. Te distance between the ribs increases with increasing shell diameter (there are 15 primaries and 52 forwardly inclined secondaries per half whorl). At the end of the outer whorl (where the ribbing is virgatotome), the primaries show a somewhat bullate appearance. Te rib furcation point is now at the lower third of the flank, with the ribs more forwardly inclined than at mid-whorl. Te maximum whorl thickness is at the lower third of the flank. On the ventral side, the ribs are slightly arched but show no interruption or weakening. Te whorl section at the outermost whorl is somewhat subquadrate but wider ventrally (i.e., the lower third of the whorl). A single constriction runs parallel to the ribbing. At the end of the whorl (at 94 mm), a smooth 6 mm-thick band is noted, presumably a macroconchiate adult modification. Te onset of a virgatipartite stage of the ribbing pattern, the virgatipartite ribbing style, and the absence of a spur suggest that the specimen is nearly complete.
SJ/JA-RU/1983/4 ( Fig. 3D–G View Fig ): Shell small (~ 56 mm shell diameter), evolute (U/D = ~ 0.45), and compressed (T/H = 1.16). Te presence of a spur line ( Fig. 3D‒E View Fig ) suggests that the outer whorl is not preserved; assuming the presence of an outer whorl, the maximum shell diameter is estimated to be 70 mm. Te inner and middle (in part) whorls are not exposed due to the presence of extensive and hard, indurated sediments deposited in the umbilical region; this could not be removed ( Fig. 3D‒E View Fig ). Te ribbing pattern in the outer exposed whorl is the same as that of the middle whorls of the other larger specimen (ribs sharp and crested) with biplicate ribbing (up to 47 mm) that changes to polygyrate (compare Fig. 3A View Fig to D). In the sense of the general ribbing pattern (ribfurcation point at the lower third of the flank with forward inclined ribs) and shell morphology (rounded venter and subquadate whorl section), the present specimen mirrors the above-described macroconch. Additionally, a similar change in the ribbing pattern from biplicate to polygyrate ribbing pattern is also noted in this specimen. A single constriction that runs parallel to the ribbing is noted at a 50 mm shell diameter.
Remarks: Te present specimens ( Fig. 3 View Fig ) match very well with the holotype of Blaschkeiceras schoepflini ( Blaschke, 1911) deposited in the collection of the Naturhistorisches Museum in Vienna (NHMW) (see Vašíček et al., 2017, p. 588, Fig. 4A, B View Fig , who refigured it). Both macroconch specimens possess closely comparable ribbing patterns and measurements: holotype D = 94.5 mm ( Dmax = 96 mm), H = 25.6, U = 47.5 (0.50), T = 30; T/H = 1.13; phragmocone measures ~ 67 mm shell diameter. In the holotype, the ribs bifurcate at ~ lower third of the flank and show characteristic polygyrate ribbing at the outer whorl; the holotype has a somewhat sparser ribbing pattern (see also Vašíček et al., 2017, p. 587). Te holotype shows a worn-out ribbing, with ~ 20 primaries per half whorl, as opposed to 15 in the present specimen (outer preserved whorl; Fig. 3A View Fig ).
Te macroconch specimens figured by Zeiss (2001, pl. 9, Figs. 1 View Fig , 2 View Fig , NHMW 1990/42/3; Fig. 4 View Fig , NHMW 1990/42/36) are also closely comparable in that they possess similar ribbing patterns and dimensional proportions. In the specimen by Zeiss (2001, pl. 9, Figs. 2 View Fig , 3; 3 View Fig : no. SCH 1 + 2), the outer whorl also shows the characteristic change in the ribbing pattern from polygyrate to virgatipartite; however, the outer whorl is more depressed. Te macroconch specimen figured by Vašíček et al., (2017, p. 588, Fig. 4C‒E View Fig ) is also comparable in shell size (D = 104.5 mm), involution (U/D = 0.51), and with similar biplicate ribbing in its inner and middle whorls; the outer whorl is not preserved.
Vašíček et al., (2017, p. 588) noted that “ B. schoepflini was the microconch, whereas Blaschkeiceras kittli (Blaschke) could be considered its macroconchiate counterpart.” Zeiss (2001) noted that both schoepflini and kittli “are similar: with the same umbilical width (4.5 cm), 26 or 27 inner ribs are counted on half the whorl; the virgatipartite rib splitting also clearly begins at the same diameter” and that “It is possible that the species Perisphinctes ( Aulacosphinctes) schoepfilini corresponds to the inner whorls of Perisphinctes ( Pseudovirgatites) kittli . Te genus identified by Blaschke is not comprehensible. Te only thing that speaks against a union of the two species is that the split points in kittli may be thickened”.
Te holotype of Blaschkeiceras kittli (Blaschke) is a moderately large form with a shell diameter of 159.5 mm (phragmocone: 80 mm), but it is equally evolute (U/D = 0.50) and compressed (T/H = 1.08). Although it shows a similar ribbing pattern in its early whorls, there is a difference in the ribbing of its outer whorls. Te ribbing pattern is not only sparser but also coarser; the typical polygyrate ribbing pattern is also missing (see Vašíček et al., 2017, Fig. 5A, B View Fig , who refigured the holotype). Zeiss (2001) figured two specimens of Blaschkeiceras cf. kittli (Blaschke) (pl. 18, Figs. 1 View Fig and 3 View Fig ) and noted that in the larger specimen of the two ( 155 mm; pl. 18, Fig. 3 View Fig ), polygyrate ribs appear at 80 mm, “then the ribs move far apart and the splitting is, as far as seen, dichotomous or Katroliceras -like polygyrate” ( Zeiss, 2001). Compared with the present specimen, the ribbing is distinctly sparser and wider in the outer whorl. Te smaller specimen ( Zeiss, 2001, pl. 18, Fig. 1 View Fig ) shows a biplicate ribbing but with much denser and less sharp ribs than those noted in the Jaisalmer specimens. It is quite plausible that Blaschkeiceras kittli (Blaschke) and Blaschkeiceras schoepflini (Blaschke) are extreme ends of the same paleobiospecies. However, more samples are needed to corroborate this assumption.
Te present specimens also resemble with the late Tithonian specimen of Parapallasiceras spitiensis ( Uhlig, 1910) recorded from the highly ferruginous Umia Ammonite Beds of Kachchh (western India) by Pandey et al., (2016, p. 164, pl. 10, Fig. 3a–c View Fig ). However, in the Kachchh specimen the ribbing is much more irregular, and in the outer whorl, it is fascipartite, not virgatipartite as in the Jaisalmer specimen. Additionally, the Kachchh specimen also differs from the typical P. spitiensis as illustrated by Uhlig (1910, p. 351, pl. 33, Figs. 1 View Fig , 3 View Fig ; pl. 41, Fig. 1 View Fig ; see also Olóriz & Tintori, 1991, p. 475, pl. 24, Figs. 1a, b View Fig , 2 View Fig ), as in the former, the rib bifurcation point in the inner, biplicate stage is much higher and fully covered by the next-succeeding whorl (see Pandey et al., 2016, pl. 10, Fig. 3a; D View Fig = 81.5 mm).
In the Kachchh specimen of Pandey et al., (2016, pl. 10, Fig. 3a View Fig ), the furcation point is much higher in the outer whorl, as compared to the Jaisalmer specimen ( Fig. 3A View Fig ). Another point of difference is that in the Kachchh specimen, in the outer whorl, the primaries are much longer and subdued; they always arise below the umbilical edge (i.e., from the umbilical wall), whereas in the Jaisalmer specimen ( Fig. 3A View Fig ), the furcation point is somewhat bullate, if not nodate, and the primaries arise much above the umbilical margin, and with increasing shell diameter, arise consistently from below the umbilical margin. Tis is also the case in the holotype of Blaschkeiceras schoepflini (Blaschke) ( Vašíček et al., 2017, p. 588, Fig. 5A View Fig ). Also, the Kachchh specimen ( Pandey et al., 2016) opens more, and with increasing shell diameter, the preceding whorl is increasingly more exposed as compared to the Jaisalmer specimen ( Fig. 3A View Fig ). Additionally, Parapallasiceras is a Submediterranean microconchiate genus and its macroconchiate partner is Danubisphinctes Zeiss (see Schweigert & Scherzinger, 2004). Tere are no other comparable forms.
Contextually, Fürsich et al. (2021) recently noted that the ammonites from Lakhapar (i.e., of Pandey et al., 2016) “had not been collected with sufficient stratigraphic acuity so that the precise ammonite succession could not be established at that locality. Renewed sampling in 2020 showed that GAB I represents the Denseplicatus Zone and GAB II the Microcanthum Zone , whereas GAB III contains in its lower part Substeueroceras alticostatum Imlay of the latest Tithonian Frequens Zone (pers. obs.), but also Argentiniceras loncochensis (Steuer) and Spiticeras cf. ducale (Matheron) of the earliest Berriasian ( Krishna, 1991; Krishna et al., 1994).” Te GAB I–III forms the Umia Ammonite Beds of Kachchh (western India) of Pandey et al. (2016).
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