J. Nannoplankton Res., 39(1), 2021, pp. 77–87 © 2021 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA

77

Eoconusphaera hallstattensis sp. nov. and a review of the
Rhaetian genus Eoconusphaera
Isaline Demangel*
Institute of Earth Sciences, University of Graz, NAWI Graz Geocenter, Heinrichstraße 26, 8010 Graz, Austria & Department of Geology, Universityof Lund, Sölvegatan 12, 22362 Lund, Sweden; isaline.demangel@geol.lu.se

Richard Howe
Ellington Geological Services, 1414 Lumpkin Road, Houston, TX 77043, USA; richard.howe@ellingtongeo.com

Silvia Gardin
Centre de Recherche en Paléontologie, Sorbonne Université, Paris, France; silvia.gardin@upmc.fr

Sylvain Richoz
Institute of Earth Sciences, University of Graz, NAWI Graz Geocenter, Heinrichstraße 26, 8010 Graz, Austria & Department of Geology, Universityof Lund, Sölvegatan 12, 22362 Lund, Sweden; sylvain.richoz@geol.lu.se
Manuscript received 24th February, 2020; revised manuscript accepted 26th March, 2021

Abstract The genus Eoconusphaera is among the few calcareous nannofossil genera that occur in the Upper
Triassic. The calcareous nannofossil assemblages of three Rhaetian sections––two from the Austrian Northern Calcareous Alps and one from offshore north-western Australia––were studied using scanning electron and/or transmittedlight microscopy. Significant structural differences were observed in the inner structures of conical Rhaetian forms
belonging to Eoconusphaera, which prompted a revision of Eoconusphaera zlambachensis and the description of a
new species, E. hallstattensis sp. nov.

Keywords calcareous nannofossils, Upper Triassic, Rhaetian, nannoliths, coccoliths, Eoconusphaera zlambachensis, Eoconusphaera hallstattensis, taxonomy, Tethys Ocean, Tethyan, Austria, Australia

1. The Upper Triassic genus
Eoconusphaera: State of the art andhistorical background
The first records of the family Eoconusphaeraceae go backto the 1980s, with the original description of Conusphaera
zlambachensis by Moshkovitz (1982) from the Lower
Rhaetian Zlambach Formation of Austria. Conusphaera
zlambachensis was originally described as an elongatedcone, truncated at both ends, with an inner part of inclined
laths and an outer mantle of vertical, non-imbricatingplates. One year later, Jafar (1983) described a new genus
and species, Eoconusphaera tollmanniae, from the same
area and formation. The description and figures (Jafar,
1983, p. 228, figs 1–3) of E. tollmanniae correspond very
closely with the illustrations of C. zlambachensis in Moshkovitz (1982, p1. 1, figs 1–10).
The genus Eoconusphaera was described by Jafar(1983) as differing from the Upper Jurassic–mid-Cretaceous (Tithonian–Aptian) genus Conusphaera in having adome at the broader end and lacking an axial ‘canal’. Numerous published illustrations of Conusphaera mexicana(e.g. Bown & Cooper, 1989, pl. 5.2, fig. 4) show that it canhave a domed shape at its wide end, so this criterion cannot be used to separate the two genera. Conusphaera also
lacks an axial canal, in the sense of an axial cavity running
vertically through the centre of the conical nannofossil.
A dark optical suture, rather than a central canal, can beseen along the axis when viewed under crossed-nicols in
the light-microscope (LM) (e.g. Bown & Cooper, 1989,
pl. 4.16, fig. 3). This optical suture is simply the axis fromwhich the calcite laths that comprise the central core radiate, and it is similar in both Conusphaera and Eoconusphaera zlambachensis. For these reasons, the two genera
cannot be separated in the way intended by Jafar (1983),
but can instead be separated by the inclination of the inner
laths (Moshkovitz, 1982) and their disjunct stratigraphic
occurrence.
Posch & Stradner (1987) discussed the detailed structure of E. zlambachensis and showed that the outer mantle
consists of elongated, smooth, vertically-oriented plates
enclosing an inner core made of seven or eight bundlesof thin calcite laths that are obliquely stacked within eachbundle––an ultrastructure that is unique to E. zlambachensis.

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Demangel, Howe, Gardin, Richoz

Janofske (1987) regarded the genus Eoconusphaera
as superfluous, recombining E. tollmanniae into Conusphaera. She regarded the species zlambachensis andtollmanniae as differing in the orientation of their inner laths––vertical in tollmanniae and inclined in zlambachensis. This distinction between the two species is notclearly shown in any of her illustrations, however, and has
not been followed subsequently. Kristan-Tollmann (1988)
regarded E. tollmanniae as being a junior synonym of C.
zlambachensis, making C. zlambachensis the type speciesof Eoconusphaera when she recombined it into Eoconusphaera.
A new investigation of Upper Triassic sediments fromthe Steinbergkogel and Zlambach sections in the Northern
Calcareous Alps (NCA, Austria) has led to the observationof two different conical forms. To clarify the taxonomy
and descriptions of the species belonging to the genus
Eoconusphaera, we investigated them using both scanning electron and transmitted-light microscopy in orderto observe and describe in detail the ultrastructural characteristics of these species. We added and compared LM
observations made on another section, from the Northern
Carnarvon Basin (NCB) in Australia, to give a more global
perspective to our descriptions.
2. Materials and methods
During the Rhaetian (208.5–201.4 Ma; Ogg & Chen, 2020),
the Austrian sections were located around 25°N (Gallet etal., 1996), on the western margin of the Neo-Tethys Ocean,
whilst the Australian sections from the NCB, were locatedat around 30°S, along the southern margin of the NeoTethys Ocean. Of the two Austrian sections analysed, theSteinbergkogel section (47.5639°N, 13.6261°E) is locatedwest of Lake Hallstatt, at around 1245 masl (Figure 1). It
represents a topographic high, with red condensed limestone in a deep ramp setting (Richoz & Krystyn, 2015;
Demangel et al., 2020; Kovács et al., 2020). The chronologically younger Kleiner Zlambach section (47.6389°N,
13.6593°E) is located 3 km north of Lake Hallstatt, along
the Kleiner Zlambach River, at around 870 masl (Figure1), and represents a toe-of-slope palaeosetting, with limestone and marl deposition (Richoz & Krystyn, 2015; Galbrun et al., 2020; Kovács et al., 2020).
The Australian material is from the Pluto-3 and 4 petroleum exploration wells (Woodside, 2007a, b), drilled in
the NCB, offshore Western Australia. Pluto-3 was drilled

in 584.6 m water depth at -19.9119°S, 115.1613°E, whilst
Pluto-4 was drilled in 970.6 m water depth at -19.8487°S,
115.165°E. The samples studied here came from conventional cores taken from the Brigadier Formation, an
offshore marine marl, deposited in a wide and shallow
epicontinental sea between Australia and Greater India(Marshall & Lang, 2013). The Brigadier Formation is
Rhaetian in age, based on the Ashmoripollis reducta spore/pollen zone and the Dapcodinium priscum and Rhaetogonyaulax rhaetica dinoflagellate zones, correlated to the
Rhaetian by Helby et al. (1987, 2004).
A total of 55 samples were analysed from Austria––24
from the 28-m-thick Steinbergkogel section and 31 fromthe 55-m-thick Zlambach section. Two samples were examined from north-western Australia, from cores takenfrom the petroleum exploration wells, Pluto-3 and 4.
Smear-slides of the Austrian samples were prepared following the description of Bordiga et al. (2015). Fresh rocksurfaces were powdered, and 0.05 g of the rock powder
was mixed with 50 ml of buffered ammonia. With a micropipette, 1.5 ml of the solution were placed on a coverslip
and homogenised by aspiration and release. The coverslip
was dried slowly, below 50°C, to avoid sediment aggregates from forming, then mounted on a slide using Norland
Optical Adhesive before curing using a UV lamp. For theAustralian samples, smear-slides were prepared following
the method of Bown & Young (1998). LM observations
were performed on the Austrian samples using an Olympus BX50 microscope at a magnification of 2500x, and on
the Australian samples using a Leitz Ortholux microscopeat a magnification of 1000x. The scanning electron microscope (SEM) samples were prepared mainly following themethod of Preto et al. (2013a, b). The samples were cut
into 1-cm2 blocks and polished with 600- and 1200-diamond discs using deionised water as a lubricant. These
blocks were etched for 15 s in 0.1% HCl and cleaned for
7 s in an ultrasonic bath with distilled water. The samples
were dried overnight in an oven at 50°C and finally coated with 1 nm of platinum/palladium using a Cressington
Sputter Coater 208HR. The observations were performed
using a TESCAN MIRA 3 electron microscope at Lund
University.
3. Systematic palaeontology
The studied sections contain several calcareous nannofossil species characteristic of the Rhaetian. The sphericalReview of Eoconusphaera

79

Figure 1: A) Global map of the Late Triassic showing the NCA (red star) and NCB (red circle) (modified after Scotese, 2004; Golonka, 2007;
Nakada et al., 2014). B) Simplified map of Austria showing the studied sections (red stars) and two localities cited in the literature (blue stars)(modified after Gardin et al., 2012). C) Map of north-western Australia, showing the location of Pluto-3 and 4 in the NCB (red circles) (modified
after Marshall & Lang, 2013)

nannolith Prinsiosphaera triassica is abundant, as are thetwo species of Eoconusphaera described here––E. zlambachensis and E. hallstattensis sp. nov. Three species ofcoccolithophorids were also observed––Crucirhabdus
minutus, C. primulus and Archaeozygodiscus koessenensis. Three calcisphere species were also present––Thoracosphaera sp., Obliquipithonella sp. and Orthopithonellasp.
The species belonging to the genus Eoconusphaera
are considered by most workers to be nannoliths of unknown affinity. However, the following evidence suggests
a likely affinity to the coccolithophorids. Their morphol-ogy (conical shape, outer mantle with narrow vertical elements, core comprising complexly arranged elements, andalso size; Figure 2) is similar to the coccolith species Calcivascularis jansae Wiegand, 1984, which occurs in theLower Jurassic (Sinemurian–Lower Toarcian). Although
C. jansae has a similar overall morphology to Eoconusphaera, it is not closely related, as its evolution from theprotolith coccolith genus Mitrolithus is well understood(Young et al., 1986; Bown, 1987). Eoconusphaera andthe coccolithophorids seem to have a similar palaeoenvironmental preference, evolving first in subtropical zones(Jafar, 1983; Gardin et al., 2012; Demangel et al., 2020),

80

Demangel, Howe, Gardin, Richoz

and migrating into the tropical zone only during the latest Rhaetian, while other nannoliths, such as P. triassica,
were present in both zones since the Norian (Jafar, 1983;
Bralower et al., 1991). However, these species cannot be
assigned to either Crucirhabdus or Archaeozygodiscus.
The absence of a proximal cycle in the specimens observed with the LM prevented us from inferring a clear affinity to Crucirhabdus, and the presence of an outer cycleof vertical, non-imbricating elements does not correspondto Archaeozygodiscus. The optical birefringence was investigated under polarised light with a gypsum plate todetermine the crystallographic orientation.
In both species, the outer mantle in the N–S position
appears yellow on the left-hand side and blue on the righthand side (E. hallstattensis––Pl. 1, figs 15d, 17b; E. zlambachensis––Pl. 2, figs 10b, 11b, 13d, 14b), then goes into
extinction at 45° (E. hallstattensis––Pl. 1, figs 15b, 17d; E.
zlambachensis––Pl. 2, figs 10d, 13b, 14d). This information suggests sub-radial orientations with tapering c-axes
for the outer mantle. The inner core elements show minimum birefringence in the N–S and E–W positions, thenyellow at 45°, suggesting sub-vertical c-axes. This set oforientations is common among the Upper Triassic coccoliths (Young et al., 1992), providing new evidence for anaffinity between them and Eoconusphaera.
The formal definition of our new species is presented
below, in accordance with the International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code)(Turland et al., 2018).
Family EOCONUSPHAERACEAE Kristan-Tollmann,
1988

Genus Eoconusphaera Jafar, 1983
Eoconusphaera hallstattensis sp. nov.
Pl. 1, figs 1–18
1991 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Bown & Cooper, 1989 – Bralower et al.: pl. IX, figs
7–11, ?non fig. 6.
2012 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Kristan-Tollmann, 1988 – Gardin et al.: figs 6 J–I.
2020 Eoconusphaera hallstattensis (Moshkovitz, 1982)
Kristan-Tollmann, 1988 – Demangel et al.: fig. 5A.
Derivation of name: After the Hallstatt Formation, NCA,
Austria, where the first specimens of this new species were
found. Diagnosis: Elliptical (Pl. 1, fig. 3) to subcircular(Pl. 1, fig. 8) conical nannofossil, truncated at both ends,
with a flat to domed distal end (Pl. 1, figs 1, 7, 10–12, 14–
16, 18). The outer mantle of elements is composed of tall,
flat laths, vertically oriented without imbrication or overlap (Pl. 1, figs 1, 3, 4, 7, 9, 10). The number of outer elements observed is at least 12–14, although overgrowth can
obscure this number. The inner core is composed of tall,thin elements that are oriented vertically to sub-vertically,
appearing radial in plan view. No canal is visible, only acentral suture that corresponds to the axis of radiation of
the inner core laths (Pl. 1, figs 3, 8, 16, 18). The inner elements are of different lengths, and irregularly overlap eachother. They end in a flat to domed shape on the wide endof the truncated cone. Under the LM, this species presents
a trapezoid shape, with the flat outer mantle clearly visible, and showing first-order grey birefringence (Pl. 1, figs
2, 11–18). The inner part appears to be composed of sev-

Figure 2: Schematic representations of 1) Eoconusphaera zlambachensis and 2) E. hallstattensis, showing (a) the outer mantle and top view and (b)the inner core, indicating the orientation of the inner laths. Note that the colours aid visualisation of the structure, but have no particular significanceReview of Eoconusphaera

81eral undulating bars of different lengths
or small blocks, which are parallel to theouter mantle elements. The undulating effect is a result of the bundles of overlapping inner elements. At the wide end of
the nannofossil, the core can protrude beyond the outer mantle (Pl. 1, figs 1, 10, 14,
15, 16c, 18a). Differentiation: Eoconusphaera hallstattensis and E. zlambachensis exhibit many similarities in SEM
view, but have distinctly different organisation of the elements in the core, withirregularly overlapping vertical laths in E.
hallstattensis and clearly oblique bundlesof regularly arranged laths in E. zlambachensis. Also, E. hallstattensis does
not show an axial suture under crossed
Figure 3: Rhaetian biozonation based on Tethyan ammonoids and connicols, while E. zlambachensis does. The
odonts (Galbrun et al., 2020; Ogg et al., 2020) along with the ranges of
the Eoconusphaera species discussed here
two species can be easily distinguished in
the LM due to their different inner strucrim of C. minutus, suggesting they could be closely relattures. Finally, the two species are domied. Holotype: Pl. 1, fig. 1 (catalogue number 219913, colnant in distinct stratigraphic intervals––E. hallstattensis islection of the Universalmuseum Joanneum, Department ofabundant in the Lower Rhaetian (Paracochloceras suessi
Geology and Palaeontology, Graz, Austria). Dimensions:to the base of the Vandaites stuerzenbaumi ammonoid
Holotype length = 2.6 µm; holotype widest diameter = 1.6
zones; Epigondolella bidentata–Misikella posthernsteiniµm; holotype narrowest diameter = 1.4 µm. The heightand M. posthernsteini–Misikella hernsteini conodonts
ranges from 2.0 or 2.4 (Pl. 1, fig. 17) to 5.8 µm, while thezones) while E. zlambachensis dominates in the Middle
width at the widest end varies from 1.1 to 3.1 µm and atand Upper Rhaetian (V. stuerzenbaumi and Choristoceras
the narrowest end between 1.0 and 2.4 µm. Paratypes: Pl.
marshi ammonoid zones; Misikella rhaetica and M. ultima
1, figs 2–5 (catalogue numbers 219913 [Sample Zl 6.4202
conodont zones) (Figure 3). Eoconusphaera hallstattensis
for paratype figs 2, 3, 5] and 219915 [Sample Zl 35.9311
differs from C. jansae (Wiegand, 1984), which occurs infor paratype fig. 4], collection of the Universalmuseum
the Sinemurian–Toarcian, by its disjunct stratigraphic levJoanneum, Department of Geology and Palaeontology,
el and distinctly different ultrastructure in the central core.
Graz, Austria). Type locality: Kleiner Zlambach, NCA,
Calcivascularis jansae has vertical laths in the lower part
Austria (section base: 46.6464°N, 13.673°E; section top:of the core, with a complex spine above this, which fills the
46.6457°N, 13.6675°E). Type level: Sample Zl 6.4202,
central area, while E. hallstattensis has irregularly over6.4 m above the base of the Kleiner Zlambach section,
lapping vertical laths filling the core. Remarks: EoconusLower Rhaetian (P. suessi ammonoid zone; E. bidentata–phaera hallstattensis presents a broad range of size, fromM. posthernsteini conodont zone), Upper Triassic. Geoshort and stubby (Pl. 1, figs 4, 17, 18) to tall and narrowgraphical occurrence: The oldest specimens reported so(Pl.1, figs 5, 16), with several medium-sized specimens in
far are from the base of the Rhaetian in the Steinbergkogel
between (Pl 1, figs 1, 6, 7, 9, 11–15). The thickness of thesection (Gardin et al., 2012). This species is rare in the
mantle and the inner laths can vary with preservation, with
Hallstatt Formation of the Steinberkogel section (Demanthe appearance of the inner laths in the LM varying fromgel et al., 2020), but is common in the examined samples
long bars to small blocks. Eoconusphaera hallstattensisof the Zlambach Formation from the Kleiner Zlambach
has a protolith outer wall, with small, low-rimmed specisection (both are located in the open-oceanic Hallstatt Bamens being only slightly taller than the similar protolith82

Demangel, Howe, Gardin, Richoz

sin, NCA, Austria). This species has also been recorded in
the Kössen Formation (intraplatform Eiberg Basin, NCA,
southern Germany: Janofske, 1987) and from ODP Leg
122 (Wombat Plateau, north-western Australia), where thespecies is present in low abundances (rare to few: Bralower et al., 1991; SG, unpublished data, 2017). It is common
in the Lower Rhaetian in the NCB of Western Australia(RH, unpublished data, 2018). Stratigraphical occurrence: This species ranges through the Rhaetian (Upper
Triassic), from the P. suessi to V. stuerzenbaumi ammonoid zones (E. bidentata–M. posthernsteini to M. rhaetica
conodont zones) in Austria and in the Lower Rhaetian (i.e.
in the Rhaetogonyaulax rhaetica dinoflagellate zone) in
Australia. The topmost occurrence of the species observed
so far is in the upper V. stuerzenbaumi ammonoid zone/M.
rhaetica conodont zone in the Zlambach Formation of theNCA, Austria.
Eoconusphaera zlambachensis (Moshkovitz, 1982)
Bown & Cooper, 1989 emend. Demangel, Howe, Gardin& Richoz
Pl. 2, figs 1–17
1982 Conusphaera zlambachensis Moshkovitz: pp. 612–
613, pl. 1, figs 1–10 (holotype = figs 1–3).
1983 Eoconusphaera tollmanniae Jafar: pp. 228–229, figs
1–3, 6.
1987 Conusphaera zlambachensis Moshkovitz, 1982 –Janofske: p. 49, pl. 2, figs 6–8.
1987 Conusphaera tollmanniae (Jafar, 1982) Janofske: p.
49, pl. 2, figs 1–5.
1987 Conusphaera zlambachensis Moshkovitz, 1982 –Bown: p. 72, pl. 11, figs 1–3; pl. 15, figs 13, 14.
1987 Conusphaera zlambachensis Moshkovitz, 1982 –Posch & Stradner: p. 232, text-fig. 6, pl. 1, figs 1–7.
1988 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Kristan-Tollmann: p. 77.
1989 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Kristan-Tollmann, 1988 – Bown & Cooper: p. 104, pl.
5.1, figs 1–8.
1995 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Kristan-Tollmann, 1988 – Kristan-Tollmann: pp. 2–4,
pl. 1, figs 1–6.
2010 Eoconusphaera zlambachensis (Moshkovitz, 1982)
Kristan-Tollmann, 1988 – Clémence et al.: fig. 11c, k.
2016 Eoconusphaera zlambachensis (Moshkovitz, 1982)

Kristan-Tollmann, 1988 – Bottini et al.: figs 5–8.
Derivation of name: After the Zlambach Marl (now renamed the Zlambach Formation), where the first specimens were found. Original diagnosis: “Elongated cone,
truncated at both ends, composed of some 35–40 calcitic
lamellae, closely packed and radiating from the center ofthe cone. When viewed from the narrower base, the lamellae are seen to be inclined and arranged in a sinistrally
turning spindle (Pl. 1, Fig. 3, 4, 6 [in Moshkovitz, 1982;
herein, Pl. 2, figs 2, 3, 5, 8]). The outer surface of the cone
is covered by elongated, smooth plates, each one separated
from the other [herein, Pl.2, figs 2, 5, 7]. In LM, the form
is too small to reveal the fine details of the lamellae andonly the general conical shape and the cover plates, which
in many speciments [sic.] have fallen out (Pl. 1, Fig. 4, 5
[in Moshkovitz, 1982]) could be discerned (Pl. 1, Fig. 7,
8 [in Moshkovitz, 1982]).” Emended description: In addition to the presence of a core comprising approximately
eight radially arranged bundles (Posch & Stradner, 1987),
our observations highlighted additional characteristics, including the inclination of the calcite laths (between 150
and 159º; Pl. 2, figs 2, 5, 8). Similarly to Eoconusphaera
hallstattensis, specimens have been observed with adomed shape at the widest extremity, formed by an extension of the inner laths (Pl. 2, figs 3, 5, 11, 14, 16), which
can be enclosed by the outer mantle of elements, if theseare preserved (Pl. 2, figs 3, 11, 12, 14). Less frequently,
and only observed in the SEM, E. zlambachensis canalso present a domed structure on the narrow extremity,
formed by the outer mantle laths joining at the end, moreor less enclosing the extremity, depending on preservation (Pl. 2, fig. 2). Under the LM, E. zlambachensis has amore trapezoid shape than E. hallstattensis. Because thelaths of the inner core in E. zlambachensis are very thin(<0.5 µm thick), they cannot be distinguished from eachother optically. Hence, the inner core appears as a homogenous, birefringent block at all angles to the polariser. A
thin, dark line, reflecting the central axis, from which thelaths of the inner core radiate, is visible in some orientations. Differentiation: Eoconusphaera zlambachensis differs from E. hallstattensis in the inclination of the laths in
the inner core, its appearance in the LM (see description
above), its more circular extremities and its dominance inthe V. stuerzenbaumi and Choristoceras marshi ammonoid
zones (M. rhaetica and M. ultima conodont zones). Di-

Review of Eoconusphaera

mensions of observed specimens: The length of our specimens varied between 2.2 and 4.8 µm, with the width of
the wide end varying between 1.4 and 3 µm, and the widthof the narrow end varying from 1 to 2.5 µm. Holotype
dimensions: Length = 8 µm; width of wide end = 5 µm;
width of narrow end = 3.5 µm (Moshkovitz, 1982). Geographical occurrence: According to Moshkovitz (1982),
E. zlambachensis was common in the Zlambach Formation (open-oceanic Hallstatt Basin) in the Fischerwiese
and Roßmoosgraben sections and less frequent in the Kössen Formation (intraplatform Eiberg Basin) in the Kendlbachgraben section. According to Jafar (1983), it was
only frequent (not common) in the Fischerwiese section(Zlambach Formation) and rare in the Ampelsbach section(Kössen Formation). Bown & Cooper (1989) reported ahigh abundance (i.e. 10–20 specimens per field of viewat 1000x magnification, equivalent to 50% of the assemblage) in the Weißloferbach section (Kössen Formation).
According to Kristan-Tollmann (1995), the species was ascommon as Prinsiosphaera triassica in the Grünbachgraben section (Zlambach Formation). Clémence et al. (2010)
reported its high relative abundance in the Eiberg section(i.e. 20–40% of the assemblages), but less abundant in Tiefengraben (i.e. 10–15%) (both in the Kössen Formation).
All these localities are in the NCA, Austria. Bralower etal. (1991) recorded this species as being common in theUpper Triassic of the Wombat Plateau, offshore Western
Australia. It was very common (up to 100–150 specimens
per field of view at 1000x magnification) in the BrigadierFormation in the NCB, offshore Western Australia (RH,
unpublished data, 2018). Stratigraphical occurrence:
Upper Triassic, Rhaetian (lower V. stuerzenbaumi–C.
marshi ammonoid zones, M. posthernsteini–M. hernsteini
to M. ultima conodont zones). Remarks: The specimens
called E. zlambachensis by Bralower et al. (1991) do not
closely resemble the holotype of this species. The innercore of their specimens, figured in LM photomicrographs(Bralower et al., 1991, pl. IX, figs 7–11), do not have thetypical continuous birefringence pattern of E. zlambachensis, so they are considered here to belong to E. hallstattensis. The specimens illustrated by Bottini et al. (2016, pl. 1,
figs 5–8) are poorly preserved, but in the LM, they show
continuous laths in the core, suggesting they are closer toE. zlambachensis than E. hallstattensis, which has discontinuous laths in the core.

83

4. Conclusions
This study clarifies the taxonomy of the two species in
the genus Eoconusphaera in the Late Triassic. A new species––Eoconusphaera hallstattensis––has been describedas having two differentiating characteristics––the absenceof an axial suture under crossed nicols and the presenceof numerous overlapping, vertical inner laths, which appear as undulating bars in the LM. Eoconusphaera zlambachensis has been emended to include specimens where
the inner, inclined (~154°) laths are arranged in bundles;
it also sometimes has a domed shape at the wider end, likeE. hallstattensis, but also, less frequently, at the narrowend. In addition to the different structural characteristics(inner lath shape and orientation), these two species dominate in different stratigraphic intervals. Eoconusphaera
hallstattensis first occurs in the Paracochloceras suessi
ammonoid zone, dominating from there up to the base of
the Vandaites stuerzenbaumi ammonoid zone. Eoconusphaera zlambachensis first appears at the base of the V.
stuerzenbaumi zone and dominates during that and theChoristoceras marshi zone. We suggest that these two
species might be useful biostratigraphic markers for thelatest Triassic in the Western Tethys.
Acknowledgements
This research was supported by the Austrian Science Foundation (Project P 29497-P29 to SR). The SEM observations were
supported by the Royal Physiographic Society of Lund (grant toID). We thank Werner E. Piller for his advice on the taxonomic
description and his help in improving the English in the earlystages of the manuscript. We very much thank Dr Jeremy Youngfor his careful review, his suggestions, and his help in integrating
the crystallographic orientation analyses to improve the manuscript. We also thank Matt Hampton for his critical comments
and interesting interpretations.

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Demangel, Howe, Gardin, Richoz

Plate 1
Eoconusphaera hallstattensis SEM & LM images. 1–15: Zlambach, Austria; 16–18: Australia
short specimen, side view

XPL, side view

dome

vertical outermantle laths

outer mantle
vertical innerlaths
top view ofradially
vertical outerarranged inner mantle laths
laths

mid-sized specimen, side viewelongated specimen, side view

vertical inner
lathsvertical outermantle lathsside view ofradially
arranged inner
laths

dome
side view

radially
arranged inner
laths

radially
arranged
inner laths

vertical outermantle laths

vertical outermantle laths
dome
top view

side view

2 µm

2 µm

11–15: side views,
cross-polarised light (XPL)
11: sample Zl 5.5164; 12: Zl
5.5164; 13: Zl 8.6847; 14: Zl
8.6847; 15: Zl 14.9960

16: side view, XPL (a, c), phase contrast(PC) (b, d), specimen with different rotation patterns, sample 1502
17: side view, XPL (a), PC (b), sample
3134

18: side view, XPL (a, c), PC (b, d), specimen with different rotation
patterns, sample 3140
2 µm

Review of Eoconusphaera

85

Plate 2
Eoconusphaera zlambachensis SEM & LM images. 1–12: Zlambach, Austria; 13–17: Australia
extension of mantle laths from side to dome

side view ofinclined inner
laths & central
axisside view of oblique
inner laths
top view ofradially arranged inner laths

thick, domed mantle
at narrow end

dome at wide end

side view ofcentral axis &oblique, radial
inner lathsside view ofcentral axis &inner lathsside view of stacks of oblique inner laths &vertical outer laths

XPL

XPL

2 µm
XPL
side view of elongated& short specimens
showing vertical mantle laths

XPL

XPL

PC

PC

XPL

side view of stacks of oblique inner laths

XPL

XPL

PC

PC

XPL

XPL

PC

XPL

PC

XPL

PC

9–12: side views of four specimens with a dome shape at the wide end, mantle visible as pale lateral bars, central axis dark, sample Zl 51. 8659. 13:
side view of specimen with different rotation patterns, sample 1499. 14: side view, sample 3143. 15: side view of three specimens, sample 3150. 16:
side view of specimen with different rotation patterns, sample 3146. 17: side view of specimen with different rotation patterns, sample 1501

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