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New Records of Marine Gastropods from the Lower Cretaceous of West-Central Argentina

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Eleven new records of marine gastropods from several localities in west-central Argentina are hereby presented, including the following new species: Proconulus kotrus, Calliotropis (Riselloidea) ligosta, Lyosoma truquicoensis, Exelissa crassicostata, Cirsocerithium agriorivensis, Cataldia? binodosa, Vanikoropsis? leviplicata and Tornatellaea neuquina. These records were recovered from two Early Cretaceous units of the Neuquén Basin, the Mulichinco (Valanginian) and the Agrio (upper Valanginian–upper Hauterivian/lowermost Barremian) formations. The families Proconulidae, Calliotropidae, Neritidae, Cryptaulacidae, ?Pseudomelaniidae, Vanikoridae, Epitoniidae and Acteonidae are represented whilst one record is yet to be assigned at the family level.
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Instituto de Estudios Andinos Don Pablo Groeber, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, Departamento de Ciencias
Geológicas, Facultad de Ciencias Exactas y Na turales, Intendente Güiraldes 2160, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina.
Submitted: September 22nd , 2016 - Accepted: December 14th, 2016
To cite this article: Cecilia S. Cataldo (2017). New records of marine gastropods from the Lower Cretaceous of
west-central Argentina. Ameghiniana 54: 405–440.
To link to this article:
Also appearing in this issue:
New records of aquatic sloths from
the Pliocene of Chile and the southern
distribution of subtropical coastal
New species from the
Berriasian–Barremian of Patagonia
reveal a gastropod fauna with
strong Tethyan influence.
Palynology of La Veteada Formation
with a abundant lycopsid tetrads as
in extra-Gondwanan records of
Lopingian–Triassic age.
Instituto de Estudios Andinos Don Pablo Groeber, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad de Buenos Aires, Departamento de Ciencias
Geológicas, Facultad de Ciencias Exactas y Naturales, Intendente Güiraldes 2160, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina.
Abstract. Eleven new records of marine gastropods from several localities in west-central Argentina are hereby presented, including the
following new species: Proconulus kotrus, Calliotropis (Riselloidea) ligosta, Lyosoma truquicoensis, Exelissa crassicostata, Cirsocerithium agrioriven-
sis, Cataldia? binodosa, Vanikoropsis? leviplicata and Tornatellaea neuquina. These records were recovered from two Early Cretaceous units of the
Neuquén Basin, the Mulichinco (Valanginian) and the Agrio (upper Valanginian–upper Hauterivian/lowermost Barremian) formations. The
families Proconulidae, Calliotropidae, Neritidae, Cryptaulacidae, ?Pseudomelaniidae, Vanikoridae, Epitoniidae and Acteonidae are represented
whilst one record is yet to be assigned at the family level.
Key words. Gastropoda. Neuquén Basin. Argentina. Valanginian. Hauterivian.
conocer 11 nuevos registros de gastrópodos marinos procedentes de numerosas localidades en el centro-oeste de Argentina. Entre ellos se
encuentran las siguientes especies nuevas: Proconulus kotrus, Calliotropis (Riselloidea) ligosta, Lyosoma truquicoensis, Exelissa crassicostata,
Cirsocerithium agriorivensis, Cataldia? binodosa, Vanikoropsis? leviplicata y Tornatellaea neuquina. Estos registros proceden de dos unidades de edad
cretácica temprana de la Cuenca Neuquina: las formaciones Mulichinco (Valanginiano) y Agrio (Valanginiano superior–Hauteriviano supe-
rior/Barremiano basal). En esta fauna se encuentran representadas las familias Proconulidae, Calliotropidae, Neritidae, Cryptaulacidae, ?Pseu-
domelaniidae, Vanikoridae, Epitoniidae y Acteonidae, con un registro no asignado aún a nivel familia.
Palabras clave. Gastropoda. Cuenca Neuquina. Argentina. Valanginiano. Hauteriviano.
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440 ARTICLES
ISSN 0002-7014
THE latest Jurassic–Early Cretaceous marine units of the
Neuquén Basin have yielded a rich macroinvertebrate fauna,
one of the most diverse of the coeval basins of southern
South America and certainly the one that is the best known
so far. The upper Valanginian–lowermost Barremian Agrio
Formation is particularly highly fossiliferous (for a summary
see Aguirre-Urreta et al., 2011).
Gastropods from the Tithonian–Berriasian interval of
the Neuquén Basin were first reported by Behrendsen
(1891, 1892), Haupt (1907), Weaver (1931), Camacho (1953),
Damborenea et al. (1979) and Manceñido and Damborenea
(1984) and yet studied with different degrees of detail.
Although these authors reported about 45 gastropod taxa
in total, more recent studies resulted in the synonymy of
several of these records and the arising of new findings
(e.g., Cataldo, 2013; Cataldo and Lazo, 2016) whilst several
records are still under revision (see Supplementary Online
Information). So far, more than 30 gastropod species were
recovered only from the Agrio Formation, plus several still
undescribed gastropods from other Early Cretaceous units
of the same basin (pers. obs.).
Herein, new systematic information regarding the gas-
tropod fauna of the Mulichinco and Agrio formations of the
Neuquén Basin is provided and eleven hitherto unknown
gastropod records are reported, including eight new species.
Three records are however left in open nomenclature at
the species level due to scarcity of material or poor preser-
vation. The new association is composed of the vetigas-
tropods Proconulus kotrus sp. nov. and Calliotropis (Rise-
lloidea)ligosta sp. nov., the neritiform Lyosoma truquicoensis
sp. nov., the caenogastropods Exelissa crassicostata sp. nov.,
Cirsocerithium agriorivensis sp. nov, Paosia? sp., Cataldia? bin-
odosa sp. nov., Vanikoropsis? leviplicata sp. nov. and Confu-
siscala sp., and the heterobranchs Tornatellaea neuquina sp.
nov. and Tornatellaea? sp..
The new records herein presented comprise more than
500 specimens recovered from 17 localities across the
Neuquén Basin. Precise stratigraphic ranges are provided
for each species based on the solid biostratigraphic frame-
work produced by Aguirre-Urreta et al. (2005) and Aguirre-
Urreta and Rawson (2012). The specimens constitute
loose three-dimension shells with fine-grained fill as well
as shells embedded in coquina and thin pavements marked
by different degrees of consolidation. The teleoconchs are
recrystallized and, except for a few exceptions, exhibit a
comparable level of taphonomic modification. The apices
are, as a rule, broken off and, therefore, the protoconchs could
not be observed except those of the holotype of Calliotropis
(Riselloidea) ligosta sp. nov. and one paratype of Tornatellaea
neuquina sp. nov. The fact that the delicate peristomes are
also almost always chipped hinders taxonomic determina-
tion. Still, because abrasion is generally low, the details of
the teleoconch sculpture prove well preserved in almost
every specimen.
All scanning electron microscope (SEM) images were
taken with a FEI Quanta 200 device in low vacuum mode in
the Servicio de Microscopía Electrónica de Barrido y Micro-
análisis (SeMFi), Laboratorio de Investigaciones de Meta-
lurgia Física Ingeniero Gregorio Cusminsky (LIMF), Facultad
de Ingeniería, Universidad Nacional de La Plata, La Plata,
Argentina. Conventional photographs were taken with a
number of compact and DSLR plus macro lens cameras; all
specimens were coated with sublimated ammonium chloride.
Matthews’ (1973) and Bengtson’s (1988) criteria for the
usage of open nomenclature were followed.
Institutional acronyms. The material described and illustra-
ted herein is housed in the Collección de Paleontología, Uni-
versidad de Buenos Aires, Buenos Aires, Argentina (CPBA)
and the Colección de Paleoinvertebrados, Museo de Ciencias
Naturales y Antropológicas J.C. Moyano, Mendoza, Argentina
(MCNAM-Pi). Additionally, references to specimens housed
in other institutions are provided as follows: MLP, Museo de
La Plata, La Plata, Argentina; PRI, Paleontological Research
Institution, Ithaca, USA; SIPB, Steinmann-Institut für Geolo-
gie, Mineralogie und Paläontologie, Bonn, Germany.
Measurements.Morphologic terminology and measurements
follow Cox (1960). D, maximum diameter of teleoconch; H,
height of teleoconch; H/D, height to diameter rate; Hap,
height of aperture; Hlw, height of last whorl; Hlw/H, height
of last whorl to height of teleoconch rate; PA, pleural angle.
The new records presented herein were collected from
15 localities in the Neuquén province and two localities in
the Mendoza province (Fig. 1). Nine out of ten species were
gathered from the Agrio Formation whilst the remaining
species were retrieved from the Mulichinco Formation (Fig.
2–3). The species hereby discussed are rather uncommon
and restricted to one or a handful of localities but for a few
exceptions and thus contrast with other known species
from these units that are very abundant and geographically
widespread within the basin (e.g., Cataldo, 2014).
Within the sedimentary fill of the Neuquén Basin, the
bearing units are part of the Mendoza Group and particu-
larly of its middle and upper sections (Fig. 2). In the Valan-
ginian Mulichinco Formation, continental and volcaniclastic
deposits coexist with marine shales and thick carbonates
(Legarreta and Gulisano, 1989). The outcrops of this unit
are developed mainly in central and northern Neuquén and
the facies grade vertically and laterally from continental to
marginal marine, being mostly marine in the northernmost
area (Schwarz et al., 2011), with sandstones and shales in-
terbedded with coquinas (Aguirre-Urreta et al., 2008). The
Agrio Formation is a thick unit almost totally composed of
marine beds for which deposition begun with a basin-scale
transgression (Spalletti et al., 2011). The Pilmatué (lower)
and Agua de la Mula (upper) members are typically com-
posed of thick shales interbedded with sandstones, lime-
stones and coquinas within a shallow-platform marine
setting (Spalletti et al., 2001). The middle, fluvial-aeolian
Avi Member was the result of a temporary drop in the
relative sea level during the mid-Hauterivian (Legarreta
and Gulisano, 1989).
Class GASTROPODA Cuvier, 1795
Subclass VETIGASTROPODA Salvini-Plawen, 1980
Superfamily TURBINOIDEA Rafinesque, 1815
Family PROCONULIDAE Cox in Knight et al., 1960
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Figure 1. Map with fossil localities, indicating species and number of specimens (in parentheses) occurring at each site.
Remarks. Gründel (2000) revised this family and its type
genus taking into account diagnostic features previously
unnoticed, e.g., an intermediate sculpture between the pro-
toconch and the teleoconch, and stressing the diagnostic
importance of the morphology of the inner lip area.
1) Lagunitas Este (S34º36’, W69º30’)
Paosia? sp. (1)
2) Lomas Bayas (S34º39’, W69º31’)
Paosia? sp. (6)
3) Puerta Curaco (S37º22’, W69º56’)
Tornatellaea? sp. (5)
4) Loma de la Torre (S37º20’, W69º48’)
Vanikoropsis? leviplicata sp. nov. (2)
5) Chos Malal Norte (S37º21’, W70º23’)
Calliotropis (Riselloidea) ligosta sp. nov. (1)
6) El Gasoducto (S37º25’, W69º56’)
Cataldia? binodosa sp. nov. (1)
7) Arroyo Truquico (S37º28’, W70º17’)
Lyosoma truquicoensis sp. nov. (27)
8) Puesto Canale (S37º36’, W70º2’)
Vanikoropsis? leviplicata sp. nov. (1)
9) Pichaihue (S37º47’, W70º13’)
Tornatellaea neuquina sp. nov. (15)
10) Agua de la Mula (S34º36’, W69º30’)
Exelissa crassicostata sp. nov. (166)
Cirsocerithium agriorivensis sp. nov. (23)
Paosia? sp. (2)
Cataldia? binodosa sp. nov. (2)
Vanikoropsis? leviplicata sp. nov. (20)
11) Salado Norte (S38º10’, W70°5’)
Cataldia? binodosa sp. nov. (59)
12) Salado Sur (S38º12’, W70º3’)
Confusiscala sp. (1)
13) Agrio del Medio (S38º20’, W69º57’)
Paosia? sp. (5)
14) Bajada Vieja (S38º25’, W70º0’)
Exelissa crassicostata sp. nov. (135)
Cirsocerithium agriorivensis sp. nov. (19)
Paosia? sp. (1)
Cataldia? binodosa sp. nov. (7)
15) Cerro Bayo (S38º41’, W70º4’)
Confusiscala sp. (2)
16) Cerro Marucho (S39º26’, W70º10’)
Cataldia? binodosa sp. nov. (1)
17) Aguada Florencio (S39º29’, W70º16’)
Cataldia? binodosa sp. nov. (6)
Genus Proconulus Cossmann, 1918 (= Cochleochilus
Cossmann, 1918)
Type species. Trochus guillieri Cossmann, 1885 (see also Cossmann,
1918, pl. 9, fig. 30), Bathonian, France; by original designation.
Remarks. According to the records reported by various au-
thors (Cossmann, 1918; Cox in Knight et al., 1960; Calzada,
1989a; Szabó, 2008), this genus ranges from the Lower
Jurassic (Sinemurian) to the Upper Cretaceous and occurs
almost worldwide, though more widely distributed during
the Jurassic than during the Cretaceous.
Proconulus is strongly similar in overall shape and sculp-
ture to Cochleochilus, a genus erected by Cossmann (1918)
for trochiform, anomphalous shells with a prosocline and
round aperture as well as a columellar callus bearing a
groove and a knob on its adapical end. The type species is
Trochus diomedes d’Orbigny, 1850 (= Trochus cottaldinus
d’Orbigny, 1850, sensu Fischer and Weber, 1997, p. 119, pl.
20, figs. 6–7; see also Cox in Knight et al., 1960, p. 253, fig.
163.16), which, according to Gründel (2008), fits the revised
diagnosis of Proconulus. However, this author considered
that Proconulus and Cochleochilus could be distinguished on
the basis of a subtle difference regarding inner lip construc-
tion: while there is a knob on the adapical end of the col-
umellar groove in Cochleochilus, in Proconulus there is no
such knob but a thickening of the adapical end of the right
wall that borders the columellar groove. However, as Grün-
del (2008) stated, the implications of such subtle difference
are yet to be clarified. With only a handful of species based
on badly preserved material failing to conclusively exhibit
the supposedly diagnostic inner lip morphology (see Coss-
mann, 1918; Fischer and Weber, 1997), Cochleochilus is a
rather enigmatic genus. Moreover, Cossmann’s (1918, pl. 9,
fig. 34) and Fischer and Weber’s (1997, pl. 20, fig. 7) figures
of the type species illustrate an inner lip morphology just
like that of Proconulus, i.e., with a thickening instead of a
knob. It is thus herein concluded that Cochleochilus is not
thoroughly supported by morphological features and should
thus be regarded as a junior synonym of Proconulus.
Another similar genus is Calliostoma Swainson, 1840,
but, according to Cossmann (1918), it can be distinguished
from Proconulus by its smooth columellar lip with a knob on
its abapical end and a notch that separates it from the
basal lip.
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Figure 2. Comparative stratigraphic chart of the units outcropping in southern Mendoza, north-central Neuquén and southern Neuquén. Based
on Leanza and Hugo (1997), Leanza et al. (2001) and Sruoga et al. (2005). Fm., formation; Gr., group; L., Lower; Mbr., member; pars., partially;
U., Upper.
Proconulus kotrus sp. nov.
Figure 4.1–6
Diagnosis.Proconulus with very fine spiral threads, mature
whorls with concave-convex profile and suture dropping
ever lower, and broadly rounded periphery.
Description. Shell small, trochiform, slightly taller than wide,
with moderately low apex and regularly expanding whorls.
Protoconch not preserved. Teleoconch with three and a
half to four preserved whorls. Spire conical, representing
approximately 25% of the total shell height. First and
second spire whorls flat-sided; third whorl slightly more
concave, abapically bordered by poorly defined suprasutural
spiral carina. Suture impressed, slightly channeled from
third whorl onwards where it drops ever lower. Last whorl
large, with sinuous profile: concave profile in adapical half
and convex towards a markedly rounded periphery. Base
flat to slightly convex. Umbilicus closed, covered by inner lip
callus. Aperture only partially known, apparently holosto-
mate, round and strongly prosocline. Outer lip not pre-
served. Columellar lip wide and crescent-shaped, with
narrow and shallow groove, slightly more excavated on its
adapical end. Inner margin of columellar lip raised as ridge
that thickens on its adapical end forming a transversely ex-
panded protuberance. Sculpture of fine, equidistant spiral
threads. Growth lines strongly prosocline, forming shallow
prosocyrt sinus just below adapical suture and then straight,
forming growth rugae near aperture.
Occurrence. The species occurs at the Salado Sur locality,
central Neuquén, in late Hauterivian beds belonging to the
C. schlagintweiti Subzone in the Agua de la Mula Member of
the Agrio Formation.
Material. Three specimens; holotype CPBA 21292.1 and two
paratypes, CPBA 21292.2 and 21292.3.
Derivation of name.Latinized form of the Mapuche adjective
kotrü, salty, bitter, literal translation of the name of the type
and so far only locality.
Dimensions. Holotype: H= 11.1 mm; Hlw= 8.3 mm; Hap= 5.2
mm; D= 9.3 mm; D/H= 0.84; Hlw/H= 0.75; PA= 49.7º.
Paratype (CPBA 21292.2): H= 10.6 mm; Hlw= 8.3 mm; Hap=
5.7 mm; D= 10.4 mm; D/H= 0.98; Hlw/H= 0.78; PA= 61º.
Discussion. Proconulus kotrus sp. nov. matches the diagnosis
of Proconulidae and Proconulus in the sense of Gründel’s
(2000) revision.
The construction of the columellar lip is comparable to
that of Proconulus coelotropis (Schmidt, 1905) and Proconu-
lus viadrinus (Schmidt, 1905), both species from the Upper
Jurassic (upper Oxfordian) of Poland (see Gründel and Kaim,
2006, p. 128–130, figs. 6–7).
In the mature whorls of the holotype of P. kotrus there is
an abapical displacement of the adapical suture, making the
shell outline change from conical to slightly cyrtoconoid.
This is consistent to what whas pointed out by Dambore-
nea and Ferrari (2009) when comparing Lithotrochus Conrad,
1855 with Proconulus. Both paratypes present fewer whorls
than the holotype and their shells therefore retain a conical
outline. The lateral profile of whorls is also marked by onto-
genetic variability in this species; that is, the younger the
whorl, the more noticeable its concave-convex lateral pro-
file will be. The sculpture in P. kotrus is composed of nu-
merous, very thin spiral threads that are almost invisible to
the naked eye.
The oldest records of Proconulus correspond to the Sine-
murian of Hungary (e.g., Szabó, 2008). Most known species
were recovered from the Middle Jurassic of Europe and
other peri-Tethyan localities. Only a handful of Early Cre-
taceous species are so far known: Proconulus paskensis
Beisel, 1983 (p. 58, pl. 2, fig. 4), from the lower Valanginian
of Siberia; Proconulus sp. (Mongin, 1979: p. 112, fig. 1), from
the Valanginian of Tunisia; Proconulus eixarchi Calzada and
Forner, 2006 (p. 49, figs. 1–2), from the upper Barremian–
lower Aptian of eastern Spain; Proconulus hiraigensis Kase,
1984 (p. 64, pl. 4, figs. 2–5, 11–12), from the upper Aptian–
lower Albian of Miyako, Japan; and Proconulus chebeikiaen-
sis Collignon, 1972 (p. 12, pl. 1, figs. 10–13), from the Albian
of Morocco; among others. These species differ from P.
kotrus in having a different shell and/or whorl profile (e.g.,P.
hiraigensis, P. chebeikiaensis, P. eixarchi,Proconulus sp.) and/or
in lacking a protuberance in the columellar lip (e.g.,P. hirai-
gensis, P. paskensis, P. eixarchi).
The representatives of this genus were seemingly
present in the region since the Early Jurassic, as indicated by
the record of Proconulus? argentinus Ferrari, 2015a, from the
Pliensbachian of Neuquén. This species differs from P. kotrus
in presenting a conical instead of a cyrtoconoid adult shell
and flat-sided to slightly convex whorls instead of a concave-
convex whorl profile, as well as a more angular periphery.
Proconulus kotrus is very similar to the type species of
Cochleochilus as illustrated by Cossmann (1918, pl. 9, figs. 31–
34). Such resemblance, plus the fact that even the construc-
tion of the inner lip seems equivalent in both species, supplies
further reasons to question the independence of Cochleochilus.
Superfamily SEGUENZIOIDEA Verrill, 1884
Family EUCYCLIDAE Koken, 1897
Remarks. Recently, Ferrari et al. (2014) revised the type
genus of Eucyclidae and other related genera and pro-
posed a new classification scheme in which Calliotropidae
is synonymous of Eucyclidae. Hickman and McLean (1990)
originally proposed Calliotropidae as a tribe of the Eucycli-
nae and Bandel (2010) subsequently elevated it to family.
The main shell feature distinguishing eucyclids consists
of the fact that the first teleoconch whorls exhibit collabral
ribs (e.g., Gründel, 1997, pl. 3, figs. 5–7; Kaim, 2004, figs. 6-
A4, 6-B2, 9-E5; Bandel, 2010, pl. 9, figs. D–G).
Genus Calliotropis Seguenza, 1903
Type species.Trochus ottoi Philippi, 1844, Pliocene–Pleistocene,
Italy; by original designation. Currently living in the Mediterranean
Sea and the NE Atlantic Ocean (Kaim, 2004; Stilwell, 2005; Bandel,
Subgenus Riselloidea Cossmann, 1909a
Type species.Risellopsis subdisjuncta Cossmann, 1908, Pliens-
bachian, France; by original designation.
Remarks. The great morphological variability and similarity
among the species of Calliotropis and Riselloidea was re-
peatedly pointed out by numerous authors over the last
decades. In some works they were treated as independent
genera whilst, in others, a synonymy was put forth (e.g.,
Gründel, 1997, 2000; Nützel and Senowbari-Daryan, 1999;
Nützel et al., 2003; Kaim, 2004; Stilwell, 2005; Szabó, 2008;
Bandel, 2010). Some distortion was introduced by Wenz’s
(1938, fig. 552) illustration of the type species of Riselloidea,
which is quite inaccurate and significantly differs from
Cossmann’s original (1908, pl. 2, figs. 10–12). Also, the re-
markable longevity of Calliotropis, recorded from the lower
Mesozoic upwards, constituted an underlying problem
which led to a great systematic instability both at the
generic and the suprageneric levels. Recently, Ferrari et al.
(2014) proposed that Riselloidea is in fact a temporal sub-
genus of Calliotropis and the problem of the longevity of
Calliotropis and the similarity between both genera was
thus tackled.
Riselloidea is represented by records as early as Late
Triassic (e.g., Cossmann, 1909a; Nützel and Senowbari-
Daryan, 1999) although it was most diverse and widely dis-
tributed during the Early and Middle Jurassic. Thus far, only
two species were reported from the Lower Cretaceous (see
discussion below).
The diagnosis of Trochonodus tzel, Hamedani and
Senowbari-Daryan, 2003 falls within the morphological
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Figure 3. Stratigraphic range of the species herein described. Am-
monoid biozonation from Aguirre-Urreta et al. (2005) and Aguirre-
Urreta and Rawson (2012). Discontinuous lines indicate inferred
occurrences. LOW., lower; VAL., Valanginian; B., Barremian; other
abbreviations as in Figure 2.
variability of Riselloidea. The differences between these
genera mentioned by Nützel et al. (2003), i.e., that Riselloidea
presents a sculpture dominated by collabral elements
without prominent nodes, are based on Wenz’s (1938)
aforementioned illustration of R. subdisjuncta. Actually, R.
subdisjuncta and other species of the genus, including the
Figure 4. 1–6, Proconulus kotrus sp. nov.; 1–3, 6, holotype, CPBA 21292.1; 1–3, apertural, lateral, and basal view; 6, SEM close-up of sculp-
ture, the arrow points towards apex of shell; 4–5, paratype, CPBA 21292.2, abapertural and apertural view. 7–12, Calliotropis (Riselloidea)
ligosta sp. nov., holotype CPBA 21291; 7, apertural view; 8–9, SEM images, abapertural and lateral view; 10, basal view; 11–12, SEM images,
details of the protoconch and first teleoconch whorls. 13–16, Lysosoma truquicoensis sp. nov.; 13–14, holotype, CPBA 21364.1, abapertural and
apical view; 15–16, paratype, CPBA 21364.6, abapertural and apertural view. Scale bars: 1–5= 2 mm, 6= 750 m, 7–10= 1 mm, 11= 500 m,
12= 250 m, 13–16= 5 mm.
one described below, exhibit nodular sculpture (see Coss-
mann, 1909a; Ferrari et al., 2014; among others). Trochon-
odus is therefore herein considered a synonym of Riselloidea.
The species described below is very similar to R. sub-
disjuncta, including the varieties described by Cossmann
(1916), and, at the same time, resembles some extant and
fossil species of Calliotropis, including its type species.
Therefore, this species supplies further evidence support-
ing the close relationship between Calliotropis and Riselloi-
Calliotropis (Riselloidea) ligosta sp. nov.
Figure 4.7–12
Diagnosis.Calliotropis without primary spiral threads or
node-rows on the base; third spiral node-row at periphery of
last whorl; periphery broadly angular; nodes large and round.
Description.Shell small, broad and low, gradate to trochi-
form, slightly taller than wide, with regularly expanding,
imbricate whorls. Protoconch with approximately one to
one and a half planispiral and smooth whorls. Teleoconch
with four and a half angulated whorls. Spire low, repre-
senting approximately 25% of the total shell height. First
whorl and a half of teleoconch convex, with ca. 30 thin or-
thocline to slightly prosocline collabral ribs and one very faint
spiral thread delimiting the adapical third. Spiral thread
strengthening gradually towards subsequent whorls, de-
veloping into conspicuous carina near mid-whorl, flanking
broad, flattish to slightly concave sutural platform. Sutural
platform widening towards later whorls. Rounded nodes
appearing by third whorl, ca. 15 per whorl. Subsutural row of
nodes appearing by third whorl and a half; nodes smaller,
connecting with those of central row through faint, wide,
prosocline collabral ribs that nearly disappear by last
whorl. Lateral whorl face flat and vertical. Suture canalicu-
late. Last whorl expanded. Periphery broadly angular, with
much less prominent nodes. Base convex, without primary
spiral threads or nodes. Umbilical area covered by narrow
inner lip callosity. Peristome not fully preserved. Aperture
apparently holostomate, round, prosocline. Outer lip un-
known; parietal lip forming narrow, clearly delimited callus;
columellar lip straight to slightly concave and slightly thick-
ened. Secondary sculpture of fine spiral threads covering all
whorls, even superimposed to nodes. Nodes becoming
fainter and more irregular towards last whorl. Growth lines
straight, strongly prosocline.
Occurrence.The only known specimen of this species was
retrieved from a late Hauterivian bed close to the top of the
Agrio Formation, north of Chos Malal city. The bed is provi-
sionally attributed to the C. diamantensis/P. groeberi zones
of the Agua de la Mula Member.
Material. Holotype, CPBA 21291.
Derivation of name.Latinized form with a change of endin-
gof the modern Greek adjective λιγοστός (ligostós), scant,
scarce, referring to the paucity of material of this species.
Dimensions. Holotype: H= 7.4 mm; Hlw= 5.5 mm; Hap= 3.8
mm; D= 6.7 mm; D/H= 0.9; Hlw/H= 0.74; PA= 50.6º.
Discussion.The smooth, planispiral protoconch whorls and
convex early teleoconch whorls with thin collabral ribs
enable a safe attribution to the Eucyclidae. Moreover, the
gradate to trochiform shell outline together with the spire
whorls with two node-rows, the abapical one being more
conspicuous while the adapical one is adjacent to the su-
ture, and the rudimentary collabral ribs, the canaliculate su-
tures and the prosocline aperture based on growth lines, as
well as the straight columellar lip, all match the diagnoses
provided for Calliotropis and Riselloidea.
Calliotropis (Riselloidea) ligosta sp. nov. differs from most
other species of the subgenus in presenting a broadly an-
gular and nodose periphery and lacking spiral cords or node-
rows below it, being inconspicuous, prosocline growth lines
and very thin secondary spiral threads the only sculpture on
the base. Despite being represented by a single specimen,
C. (R.) ligosta is so characteristic that it calls for a formal
description. If more specimens were to be collected in the
future, its generic attribution and specific distinctiveness
are unlikely to change.
The species described herein is considerably similar to
several recent species of Calliotropis, including its type
species. In fact, C. ottoi presents a third peripheral spiral
node-row at its periphery and a similar shell profile as well,
even though the profusion of concentric node-rows at its
base and the overall smaller size of the nodes distinguish it
from the Argentine Early Cretaceous species. Riselloidea
subdisjuncta is also very similar to C. (R.) ligosta, especially
as regards its strongly angular whorl profile, its canaliculate
suture and the fact that it presents a third peripheral carina.
However, this peripheral carina is smooth while the one in C.
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
(R.) ligosta bears wide and somewhat spirally-elongate
nodes. Riselloidea subdisjuncta also exhibits concentric spiral
cords at its base.
Only a few Riselloidea species recorded from the Lower
Cretaceous are referred to in the available literature. In ad-
dition to establishing the genus, Cossmann (1908) pointed
out that Wollemann (1908) had reported an almost certain
record from the “Neocomian” of Germany. This species,
Trochusstillei Wollemann, 1908 (p. 174, pl. 12, fig. 3, pl.
13, fig. 2), is certainly similar to R. subdisjuncta and, when
considering its trochiform, anomphalous shell, the moder-
ately deep sutures it presents, the two node-rows in the pe-
riphery of the last whorl and the unconspicuous prosocline
collabral ribs interconnecting the nodes, can be assigned to
Riselloidea. However, Wollemann (1908) did not mention an
adapical, subsutural row of nodes, and such presence can-
not be ascertained based on the illustrations either. For this
reason and until the meaning of such difference is better
understood, it might be more cautious to regard this attri-
bution as tentative. Riselloidea? stillei differs from C. (R.)
ligosta in bearing less deep sutures and a concave surface
between the mid-whorl and the peripheral node-rows.
In the same work, Wollemann (1908, p. 173, pl. 12, fig.
2) additionally illustratedTrochus quadricoronatus Harbort,
1905, which is very similar to R.? stillei and could also be
attributed to Riselloidea. This species differs from C. (R.)
ligosta in presenting a more conical, less trochiform and
almost cyrtoconoid shell profile.
Beisel (1983, p. 56, pl. 2, fig. 3) described two poorly-
preserved specimens from the lower Valanginian of Siberia
and attributed them to Riselloidea sp. This record differs
from C. (R.) ligosta in exhibiting a row of paired nodes along
the periphery of the whorls and several smooth spiral ribs in
the base.
Calliotropis (Riselloidea) ligosta lacks similar forms to be
compared with from nearby Early Cretaceous basins of
South America, actually representing the first record of the
genus and subgenus in the Cretaceous of the southern
world. Only one form from the Lower Cretaceous of Alexan-
der I Island, Antarctic Peninsula, is somewhat similar. Am-
phitrochus sp., as reported by Thomson (1971, p. 47, fig. 2j),
is too badly preserved to attempt a generic revision, for the
apical whorls and aperture are missing and most of the
sculpture is lost as well. However, its conical shape, its
slightly convex base, its moderately wide umbilicus and the
two node-rows adjacent to the sutures somewhat resem-
ble those of Calliotropis.
Representatives of the genus and subgenus were
present in the region from as early as the Early Jurassic
(Pliensbachian–Toarcian), with the record of Calliotropis
(Riselloidea) keideli Ferrari, Kaim and Damborenea, 2014 (p.
1181, figs. 4.1–13, 5.1–8) from Neuquén and Chubut
provinces. Calliotropis (R.) ligosta is somewhat similar to C.
(R.) keideli in the profile of its spire whorls and the canalicu-
late suture. Yet, these two species prove very different in
other aspects. For instance, the overall shell profile of C. (R.)
keideli is taller and pagodiform and its last whorl is more
elongate and has a strongly convex base bearing five
distinct spiral cords, including a node-row bordering the
pseudoumbilicus, thus resembling the genus Ambercyclus
Ferrari, Kaim and Damborenea, 2014. Also, the nodes are
smaller, sharper and more numerous than in C. (R.) ligosta.
Similar records, such as C. (R.) cf. keideli and Calliotropis
(Riselloidea) sp. (Ferrari et al., 2014), differ from C. (R.) ligosta
in basically the same traits that characterize C. (R.) keideli.
Subclass NERITIMORPHA Koken, 1897
Superfamily NERITOIDEA Rafinesque, 1815
Family NERITIDAE Rafinesque, 1815
Remarks.It is because of a calcitic outer layer (see Kaim and
Sztajner, 2004, and references therein) that neritids are
generally better preserved in comparison with other gas-
tropods with entirely aragonitic shells present in the same
lithologies. However, Saul and Squires (1997) indicated
that, in spite of the broad stratigraphic range of the family
(Triassic–Recent; Cossmann, 1925; Keen and Cox in Knight
et al., 1960; Tracey et al., 1993), neritids are normally un-
derrepresented in the fossil record due to their preference
for rocky-shore environments. In the Neuquén Basin, there
have been several reports of neritids in shoreface environ-
ments, thus making this family one of the most diverse of
the Early Cretaceous gastropod fauna of the basin (see
Supplementary Online Information). The Neritidae attained
a cosmopolitan distribution during the Jurassic.
Genus Lyosoma White, 1883
Type species.Neritina powelli White, 1876, Middle Jurassic, USA;
subsequent designation by Fischer (1885).
Remarks. The identification of Jurassic and Cretaceous neritid
genera is complex because the shell feature that bears the
apparently highest diagnostic value, i.e., the inner lip sep-
tum, is not always preserved (Kase, 1984). Shell sculpture in
Mesozoic neritids is generally not conclusive enough by its
own given that it can be highly convergent. Examples of
such inconvenience can be perceived when observing the
resemblance between Otostoma d’Archiac, 1859 and Lyo-
soma, as well as between the latter and Lissochilus Pëtho
in Zittel, 1882 (see below). The sculpture combined with the
nature of the margin of the apertural inner septum would
constitute a better diagnostic base.
Bandel and Kiel (2003) argued that Lyosoma is a pro-
blematic genus based on poorly preserved material, and
whose systematic position has not yet been adequately
established. The authors additionally pointed out that the
main difference between Lyosoma and Otostoma, i.e., a
smooth columellar edge on the inner lip septum, could prove
an artifact of preservation. This may be certainly so, given
that the inner septum is only known, according to Sohl
(1965), in two out of the more than 80 known specimens of
L. powelli. Nevertheless, Sohl (1965) added the lack of a ca-
rina in the last whorl of the species of Otostoma to the list of
differences with regard to Lyosoma and therefore affirmed
its character as an independent genus. Afterwards, Calzada
(2000) pointed out another diagnostic feature of Lyosoma:
a subsutural welt. Another species recovered from an
approximately equivalent stratigraphic interval as that from
which L. powelli was collected is Lyosoma enoda Sohl, 1965
(p. 18, pl. 2, figs. 11–13, 15–24), from the Middle Jurassic of
Utah and Wyoming, USA. The inner septum is not yet known
in this species. Sohl (1965) directly compared the specimens
of L. enoda with several specimens of the type species and,
on the grounds of a similar overall shape, concluded that
they were congeneric.
The new species described below proves remarkably
similar to L. enoda and is closer to the revised diagnosis of
Lyosoma provided by Sohl (1965) than to any other neritid
genus. It is for these reasons that the species is herein in-
cluded within Lyosoma pending a thorough revision of the
genus to confirm that the diagnostic smooth columellar
edge of the inner septum is indeed present in all the species
so far attributed to it, a task beyond the scope of this paper.
Both Lyosoma and Lissochilus present an inner septum
without denticles on the free margin and prove alike in
terms of the shell outline as well. Sohl (1965) distinguished
Lissochilus from Lyosoma on the basis of a taller spire, a
more developed spiral sculpture and a bicarinate periphery.
So far, a few Lissochilus species have been recorded from
the Lower Cretaceous of west-central Argentina (see
Supplementary Online Information) and, although their sys-
tematics require further study, they all exhibit conspicuous
nodular spiral sculpture.
Lyosoma powelli and L. enoda, both from the USA, are the
oldest records of the genus (Middle Jurassic). The list of
Lyosoma species provided by Cossmann (1925, p. 206) in-
cludes two taxa from the Lower Cretaceous of Europe
whilst the youngest record consists of one species from the
“Senonian” of Brazil (White, 1888). White’s (1888) species
and the one described below are the only southern records
thus far attributed to the genus.
Lyosoma truquicoensis sp. nov.
Figure 4.13–16
Diagnosis. Lyosoma with small- to mid-sized, smooth shell
with fine, slightly prosocline and prosocyrt growth lines as
the only sculpture, adapical third of last whorl raised above
the peripheral carina and well-developed subsutural welt.
Description. Teleoconch medium-sized to small, nearly as
tall as wide, anomphalous, sub-globose in outline, with
short and wide spire. Protoconch not preserved. Suture
slightly impressed. Base wide and gently convex. Last whorl
very expanded, representing more than 90% of the total
shell height; with narrow and nearly horizontal sutural
platform and wide and convex subsutural welt. Shallow to
well-marked spiral depression between subsutural welt
and peripheral carina; peripheral carina strong, wide and
rounded. Whorl side more or less evenly convex up to base.
Aperture wide. Outer lip thin, angular at peripheral carina,
convex adapically to carina and straight to slightly concave
abapically, nearly vertical up to union with wide basal lip.
Inner lip callous, extended inwards as a wide septum with a
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
smooth columellar margin. Teleoconch smooth but for very
fine growth lines, slightly prosocline and prosocyrt.
Occurrence.This species has been recorded from a single
level within the O. (O.) atherstoni Subzone at the base of the
Agrio Formation, at a single locality of central Neuquén:
Arroyo Truquico.
Material.Twenty-seven specimens, CPBA 21364.1–27;
holotype CPBA 21364.1 and two paratypes: CPBA 21364.5
and 21364.6.
Derivation of name.Named after Arroyo Truquico, the type
locality in the Neuquén province.
Dimensions. Holotype: H= 47.2 mm; Hlw= 46.8 mm; Hap=
43.8 mm; D= 52 mm; H/D= 0.9; Hlw/H= 0.99; PA= 104º.
Paratype (CPBA 21364.5): H= 30 mm; Hlw= 28.7 mm; Hap=
25 mm; D= 30.7 mm; D/H= 0.98; Hlw/H= 0.96; PA= 115º.
Discussion.Lyosoma truquicoensis sp. nov., which was re-
trieved form a single bed, is represented by several speci-
mens exhibiting characteristics corresponding with the
features indicated in Sohl’s (1965) diagnosis of Lyosoma,
including the non-dentate columellar edge. This species
can be readily distinguished from other neritids present in
the Agrio Formation due to the absence of both spiral and
collabral sculpture.
Lyosoma truquicoensis is most similar, both in shell out-
line and lack of sculpture, to L. enoda from the Bathonian–
Bajocian of the USA. These species can be distinguished
because L. truquicoensis is somewhat taller and the adapical
third of its last whorl is raised higher above the peripheral
carina, and presents a more developed subsutural welt.
Cossmann (1925) attributed two Early Cretaceous
species to Lyosoma. According to Sohl (1965), however,
these species cannot be placed with certainty within the
genus since their inner septum is in fact not known.
Lyosoma? capduri (Cossmann, 1907, p. 22, pl. 4, figs. 23–26)
differs from L. truquicoensis in presenting coarse nodes along
the peripheral carina and poorly-developed subsutural welt
and spiral depression, as well as an apparently taller spire.
Lyosoma? ornatissima (Coquand, 1865, p. 74, pl. 5, figs. 4–5)
differs from the Argentinian species in exhibiting a rather
discoidal, much more depressed shell outline and a well-de-
veloped spiral sculpture at and below the peripheral carina.
Recently, Calzada and Corbacho (2015a) provided a new
description for the species Lyosoma gonii Bataller, 1959,
which differs from L. truquicoensis in bearing a poorly de-
veloped subsutural welt and a spiral depression above the
peripheral carina, as well as a sculpture composed of thin,
sinuous, prosocline collabral ribs that extend from the
adapical suture up to the base of the last whorl.
White (1888) attributed one species from the “Senonian”
of Brazil to Lyosoma: L. squamosa White, 1888 (p. 179, pl. 10,
figs. 25–27). This species differs from L. truquicoensis in pre-
senting conspicuous, lamellous collabral ribs that become
more accentuated a quarter of a whorl before the aperture.
Additionally, the lamellous ribs form spiny tubercles at the
intersection with the shoulder. Desmieria peruviana Olsson,
1934 (p. 58, pl. 4, fig. 8), from the Upper Cretaceous of Peru,
is somewhat similar to the type species of Lyosoma in
outline and sculpture. However, D. peruviana can be distin-
guished in terms of its coarse node rows along the subsu-
tural welt and peripheral carina. It is worth noticing that the
inner septum in D. peruviana is still unknown. Squires and
Saul (1993) attributed this species to another controversial
genus, i.e., Corsania Vidal, 1917 (see also Calzada, 2000), on
the basis of its external morphology.
The neritid record reported by Alarcón and Vergara
(1964, p. 115, pl. 4, fig. 10) as Lyosoma sp. aff. squamosa and
recovered from the Lower Cretaceous of the El Way area in
Antofagasta, Chile, bears a well-developed spiral sculpture
formed by several thin rows of nodes below the peripheral
suture and is therefore not consistent with the diagnosis
of Lyosoma.
Subclass CAENOGASTROPODA Cox in Knight et al., 1960
Superfamily CERITHIOIDEA Fleming, 1822
Family CRYPTAULACIDAE Gründel, 1976
Remarks. Cryptaulacids are characterized by a protoconch
consisting of one to one and a half smooth whorls followed
by bicarinate whorls in which the carinae gradually develop.
The onset of the teleoconch is marked by the appearance of
the collabral sculpture. Besides, the aperture exhibits some
kind of basal modification (Guzhov, 2004). Bandel (2006) ar-
gued that the concept of the family, originally proposed as
a subfamily of Procerithiidae, is difficult to sustain given
the close resemblance between Cryptaulax Tate, 1869 and
Procerithium Cossmann in Chartron and Cossmann, 1902,
which, according to him, may even be synonymous.
In the Southern Hemisphere, cryptaulacids have been
so far recorded from the Upper Triassic of Peru (Haas, 1953;
Ferrari, 2015b), the Jurassic of Chile and Argentina (e.g.,
Gründel, 2001; Gründel and Parent, 2001, 2006; Ferrari,
2012), and the Lower Cretaceous of Argentina (this work).
This family was much less diverse in Cretaceous than in
Jurassic faunas (Guzhov, 2004, tab. 1).
Genus Exelissa Piette, 1860 (= Kilvertia Lycett, 1863)
Type species. Cerithium strangulatum d’Archiac, 1843 (p. 382, pl. 31,
fig. 1a, b), Bathonian, France; by original designation.
Remarks.The earliest discussions regarding the type species
of Exelissa dealt with whether it presented an anterior canal.
While d’Archiac (1843) described one, Piette (1860) studied
several topotypes and confirmed that the aperture was
holostomatous. Moreover, Lycett (1863), who defined Kil-
vertia based on the same type species thus establishing a
junior objective synonym of Exelissa, confirmed Piette’s
(1860) notion and added that the last whorl is cylindrical and
sometimes constricted at the base, and the peristome is
slightly thickened and expanded. According to Cossmann
(1906), the basal lip only implies the presence of a short,
straight to slightly slanted groove at the end of the columella
but does not actually confirm the presence of a real notch
or canal.
In this work, Kaim’s (2004) diagnosis of the genus em-
phasizing the teleoconch morphology is followed. The
constricted nature and abapical shift of the last whorl
present in several species of the genus could be added to
such diagnosis. This feature was stressed by Guzhov (2004)
to establish the subfamily Exelissinae.
According to Gründel (1997), the traditional position
has been to, although uncertainly, assign Exelissa to the
Procerithiidae on the grounds of teleoconch ontogeny and
sculpture. Given that the protoconch of the type species
remains unknown, the familial affinity of this genus within
Cerithoidea has not yet been settled. The protoconchs of a
few other Exelissa species (e.g., Gründel, 1999, p. 22, pl. 5,
figs. 18, 22; Guzhov, 2004, pl. 4, figs. 4b, 10; Gründel and
Parent, 2006, fig. 3D) were described as similar to the pro-
toconchs of either Procerithium or Cryptaulax. Consequently,
opinions on whether belongs within the families Cerithiidae,
Procerithiidae or Cryptaulacidae are divided and, more re-
cently, the family Bitiidae was also suggested (Bandel,
2006). Guzhov (2004) defined the subfamily Exelissinae
of the Cryptaulacidae based on Exelissa. This subfamily,
which includes several other genera in addition to Exelissa,
differs from the Cryptaulacinae in presenting a last whorl
of conspicuous morphology.
Considering that most protoconchs described for the
genus are morphologically more similar to Cryptaulax and
following the criteria of several recent authors (e.g., Guzhov,
2004; Gründel and Kaim, 2006; Gründel and Parent, 2006),
Exelissa is herein considered a representative of the Cryptau-
lacidae. Additionally, the Procer ithiu m-like protoconchs
illustrated by Gründel (1999) for a few Exelissa species were
described by Kaim (2004) as similar to the protoconch of a
Cryptaulax species from the Lower Cretaceous of Poland.
Guzhov (2004) simultaneously reassigned those same
species to a different genus.
According to Cossmann in Chartron and Cossmann
(1902), the earliest record of Exelissa corresponds to the
Hettangian (Early Jurassic) and, considering the species
described hereunder, the stratigraphic range of the genus
can be extended up to the Hauterivian (Lower Cretaceous).
Although uncertainty about certain records prevails, the
genus was widespread especially during the Jurassic, with
records across Europe, North America, eastern Africa and
southern South America.
Nützel and Gründel (2007) indicated that there are other
cerithioid genera in which the aperture is detached from the
shell base, e.g., Cryptaulax, Rhabdocolpus Cossmann, 1906,
Francocerithium Nützel and Gründel, 2007 and Tomaszoviella
Kaim, 2001. Overall, all these genera differ from Exelissa
in their much stronger nodose sculpture, their more nu-
merous opisthocyrt and othocline to prosocline collabral ribs
and the conspicuous spiral cords forming nodes at the in-
tersections with the ribs. Instead, Exelissa presents wide
and round, orthocline to slightly opisthocline ribs that are
aligned along the coiling axis providing the spire with a
pyramidal aspect. Also, Cryptoptyxis Cossmann (1906) a
pupoid shell with a detached aperture but differs from Ex-
elissa in having two columellar folds, a notch in its basal lip
and a conspicuous subsutural ramp (see Cossmann, 1906;
Gründel, 1999; Guzhov, 2004). Guzhov (2004) proposed
that Cryptoptyxis is a junior synonym of Exelissa on the
grounds of a gradual evolution between the cyrtoconoid
shell with seven or eight collabral ribs that characterizes
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Exelissa and the conical shells with five or six collabral ribs
observed in Cryptoptyxis.
Exelissa crassicostata sp. nov.
Figure 5.1–6, 5.8
Diagnosis.Exelissa with prominent, coarse collabral ribs and
non-nodose spiral sculpture.
Description.Shell small, cyrtoconoid to pupiform. Apex
acute. Protoconch and first teleoconch whorls not pre-
served. Teleoconch with up to eight whorls preserved. Spire
pyramidal, high, representing nearly 60% of the total shell
height. Suture canaliculated, within shallow depression
abapical to conspicuous spire cord. Spire whorls convex, im-
bricate, scarcely overlapping. Sculpture of wide collabral
ribs, straight to opisthocyrt and orthocline to slightly proso-
cline, oblong in shape, with convex top, tapering off towards
both sutures. Ribs equidistant from each other, lined up
forming longitudinal crests along coiling axis. Seven to eight
ribs per whorl on spire, increasing up to 10 to 12 by penul-
timate and last whorls by intercalated, out-of-alignment
additional ribs. Surface between ribs flat to concave. Con-
vexity of whorls decreasing with ontogeny. Ribs diminish in
strength and become nearly indistinct towards periphery
of last whorl. Numerous fine, band-like spiral cords, 11 to
12 on penultimate whorl, not forming nodes at intersections
with collabral ribs, with finer spiral threads in between. Pe-
riphery marked by two thicker spiral cords, surface concave
in between. Suture slightly dropping below periphery by
penultimate whorl. Base concave, with fine spiral threads.
Last whorl shorter and narrower than spire whorls. Aper-
ture partially known, small and seemingly round; parietal lip
concave, somewhat thickened and flared; basal and outer
lip unknown. Columella indistinct. Growth lines opisthocyrt,
orthocline to slightly prosocline.
Occurrence.The species occurs in the lower Hauterivian of
central Neuquén, in the Pilmatué Member of the Agrio For-
Material.A total of 301 specimens; 135 specimens from
Bajada Vieja, O. (O.) laticosta Subzone, CPBA 21293.1–135;
125 specimens from Agua de la Mula, O. (O.) laticosta Sub-
zone, CPBA 21792.1–125; 41 specimens from Agua de la
Mula, H. gentilii Zone, CPBA 21793.1–41. Holotype CPBA
21293.6 and five paratypes: CPBA 21293.3, 21293.7,
21293.8, 21792.1 and 21792.2.
Derivation of name. From the Latin adjectives crassa, thick,
and cost
ta, ribbed, owing to the sculpture of thick ribs.
Dimensions.Holotype (incomplete): H= 8.6 mm; Hlw= 5.9
mm; Hap= 2.4 mm; D= 4.25 mm; PA= 18º. Paratype (CPBA
21293.8, incomplete): H= 8.05 mm; Hlw= 4.9 mm; Hap= 2.6
mm; D= 3.55 mm; D/H= 0.44; Hlw/H= 0. 61.
Discussion. Despite lacking well-preserved apertures, the
cyrtoconoid to pupoid shell outline, the nature of the sculp-
ture and the known portion of the aperture in the studied
specimens are most reminiscent of the type species of the
genus as well as of other Exelissa species. The prominence
of the collabral ribs and the non-nodose overlapping spiral
sculpture are the key features that distinguish E. crassi-
costata from other congeneric species.
In Exelissa crassicostata sp. nov., the narrowing of the
last whorl and the abapical shift of the aperture are weak
and similar to those of Exelissa distans Cossmann, 1913 (see
also Gründel and Kaim, 2006, p. 139, fig. 16). The reduction
in strength of the sculpture towards the periphery is also
subtle. Even though the small size and thickening and fla-
ring of the peristome are manifest, the aperture in E. crassi-
costata is not preserved sufficiently well so as to evaluate
its degree of detachment from the last whorl.
The Exelissa species that are most similar to E. crassi-
costata are from the Jurassic and one example is the type
species, E. strangulata. According to Gründel’s (1997) revi-
sion of the specimens originally published by Cossmann
(1913, p. 116, pl. 5, figs. 42–45), E. strangulata bears seven
to eight collabral ribs initially orthocline and straight and
becoming slightly prosocline and opisthocyrt towards the
last whorl, just as in the Argentinian species (Gründel, 1997,
p. 93, pl. 4, figs. 12–13). Towards the last whorl, ribs lose
much of their relief and the nodose, intersecting spiral cords
become more conspicuous. Such nodose sculpture distin-
guishes E. strangulata from E. crassicostata.
Exelissa distans, from the Oxfordian of France, Poland
and Germany, is also very similar to E. crassicostata. The
number of collabral ribs and spiral cords, both primary and
secondary, and the absence of nodes at the intersections
are common to both these species. However, E. crassicostata
differs from E. distans in bearing coarser ribs and a concave
base with two stronger spiral cords at the periphery.
Exelissa arcuatoconcava Gründel and Parent, 2001 (p. 15,
fig. 3A–D) (see also Gründel and Parent, 2006, p. 506, fig.
3A–D) was recorded from the lower Tithonian of the
Neuqn Basin, in localities both in the Neuquén and
Mendoza provinces. This species presents a slender shell
and its sculpture consists of eight to 10 opisthocline and
opisthocyrt collabral ribs that are stronger at their adapical
end forming a round node. There are five to six spiral cords
on the whorl lateral face that break the ribs into several no-
dose sections, and also four to five cords on the base. The
distinct sculpture distinguishes this species from E. crassi-
There are very few known Cretaceous species of Exelissa.
Guzhov (2004) reported three: Pyrazus valanginensis Pche-
lintsev, 1965 (p. 142, pl. 27, fig. 10), from the Valanginian of
Crimea; Cryptoptyxis barremicus Sayn, 1932 (p. 37, pl. 3, figs.
2–6, 34, 35, 36), from the Barremian of Spain; and Melania
dollfusi Choffat, 1901 (p. 94, pl. 1, figs. 22–23), from the
“Senonian” of Portugal. Pyrazus valanginensis is characterized
by a conical to slightly cyrtoconical pyramidal shell with five
rows of collabral ribs along the spire and three spiral cords
on each whorl. Its aperture is not preserved but would seem
to have a round peristome (Pchelintsev, 1965). The latter
author did not mention a narrowing in the last whorl. Thus,
its attribution to Exelissa remains doubtful, considering also
that it somewhat resembles the teleoconch morphology
of Alamirifica Saul and Squires, 2003. Cryptoptyxis barremi-
cus is similar to E. crassicostata, especially regarding the
coarse collabral ribs and the pair of stronger spiral cords
at the periphery. However, the Spanish species bears a
broader shell and fewer collabral ribs. Given its seven rows
of collabral ribs and thin spiral cords, the teleoconch of M.
dollfusi as illustrated by Choffat (1901) resembles that of
Exelissa. Nevertheless, its aperture is badly preserved and
seems to have an oval peristome. In view of the doubtful
records presented above, E. crassicostata could represent
the first Early Cretaceous record of the genus.
Genus Cirsocerithium Cossmann, 1906
Type species. Cerithium subspinosum Deshayes in Leymerie, 1842 (p.
14, pl. 17, fig. 12a, b), Albian, France; by original designation.
Remarks. This genus is very similar to Rhynchocerithium
Cossmann, 1906, especially as regards the gradate spire,
the outer lip varix, the presence of the anterior canal and the
sculpture. These genera differ mainly in that the nodes in
Rhynchocerithium are spine-like, especially right below the
suture, as can be observed in the type species, R. fusiforme
(Hébert and Eudes-Deslongchamps, 1860) (see also Coss-
mann, 1906, pl. 6, figs. 18–21). Besides, the anterior canal
in Rhynchocerithium is more developed than in Cirsocerithium,
where it is more like a notch than a canal and does not
project beyond the basal lip margin. Moreover, the outer lip
in Cirsocerithium is not sinuous as it is in Rhynchocerithium.
Cossmann (1906) originally placed both Cirsocerithium
and Rhynchocerithium within the subfamily Paracerithiinae
(Family Procerithiidae), which is characterized by an aper-
ture with a basal notch that is not projected beyond the
basal lip margin (Guzhov, 2004). Bandel (2006) supported
this grouping with evidence from protoconch morphology.
However, Guzhov (2004), based on protoconch shape and
sculpture as well, ascribed the similar Rhynchocerithium to
a different family, the Maturifusidae, and argued that
Paracerithium Cossmann in Chartron and Cossmann, 1902
should be revised (see type species in Gründel, 1997;
Hikuroa and Kaim, 2007). Nützel and Gründel (2007) pre-
sented arguments opposing Guzhov’s (2004) grouping,
whilst Tracey (2010) ranked Cirsocerithium in the Cerithii-
dae. Kiel (2006, fig. 3.12, 3.14) illustrated a Cryptaulax-
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Figure 5. 1–6, 8, Exelissa crassicostata sp. nov.; 1, 6, 8, paratype, CPBA 21293.3; 1, SEM close-up of sculpture; 6, 8, apertural and abapertural
view; 2, holotype, CPBA 21293.6, apertural view; 3–4, paratype, CPBA 21293.7, abapertural and apertural view; 5, paratype, CPBA 21293.8,
lateral view; 7, 9–12, Cirsocerithium agriorivensis sp. nov.; 7, 9–10, 12, holotype, CPBA 21801.1; 7, 12, SEM close-ups of sculpture and aper-
ture; 9–10, apertural and abapertural view; 11, paratype, CPBA 21801.2, apertural view. 13–17, 19, Cataldia?binodosa sp. nov.; 13–14, holo-
type, CPBA 21796, apertural and abapertural view; 15, paratype, CPBA 21797.1, abapertural view; 16–17, CPBA 21797.3, abapertural view and
close-up of spiral sculpture; 19, CPBA 21797.4, abapertural view. 18, 20–22, Paosia?sp.; 18, 21–22, CPBA 21294, detail of growth lines on
base, apertural and abapertural view; 20, CPBA 21794.1, apertural view. Scale bars: 1, 7, 12= 500 m, 2–6, 8–11, 17= 1 mm, 13–16, 19= 4 mm,
18= 2 mm, 20–22= 5 mm. Arrows in 1, 7, 12, 17, 18 point towards apex of shells.
like protoconch for C. collignoni Kiel, 2006 and transferred
to Cirsocerithium two other species with similar protoconch
morphology that Kaim (2004) had previously regarded as
representatives of Cryptaulax. In consideration of the afore-
mentioned appreciations, the genus is herein included
within Cryptaulacidae. Yet, given its apertural morphology,
it is however difficult to assess which of Guzhov’s (2004)
subfamilies of the Cryptaulacidae would Cirsocerithium
actually correspond to.
Cirsocerithium agriorivensis sp. nov.
Figure 5.7, 5.9–12
Diagnosis. Cirsocerithium with convex whorl profile, sharp or-
thocline collabral ribs, four spiral cords, no subsutural cord
and secondary threads, and with faint swellings on the ribs
instead of pointy nodes.
Description.Shell small, cyrtoconoid to subfusiform. Apex
acute. Protoconch and first teleoconch whorls not pre-
served. Teleoconch with up to seven whorls preserved. Spire
high, representing 50% of total shell height. Suture grooved.
Spire whorls strongly convex, slightly overlapping, without
subsutural ramp. Sculpture of 10 strong collabral ribs per
whorl. Ribs sharp, straight, orthocline to slightly prosocline,
equidistant, out of alingment between succeeding whorls.
Surface between ribs concave. Ribs crossed by four equi-
distant spiral threads forming faint swellings at intersec-
tions. Last whorl slightly taller than wide. Five visible spiral
ribs. Periphery rounded, marked by one slightly thicker
spiral thread followed abapically by another spiral thread.
Base convex, slightly concave near columella. Columella
straight. Aperture partially known. Peristome obliquely oval.
Outer lip evenly convex; apertural varix well-preserved,
thick, straight, slightly prosocline, extended from adapical
suture to junction with basal lip, sculptured by prolongation
of spiral threads. Inner lip simple and concave. Shallow pout
at junction of basal lip with end of columella, not forming
true anterior canal.
Occurrence. This species occurs in the Hauterivian of central
Neuquén, both in the Pilmatué and the Agua de la Mula
members of the Agrio Formation. In the Pilmatué Member,
the species occurs in the same levels as Exelissa crassi-
costata sp. nov..
Material. A total of 43 specimens; 19 specimens from Ba-
jada Vieja, O. (O.) laticosta Subzone, CPBA 21801.1–19; 20
specimens from Agua de la Mula, O. (O.) laticosta Subzone,
CPBA 21802.1–20; two specimens from Agua de la Mula,
H. gentilii Zone, CPBA 21803.1–2; one specimen from Agua
de la Mula, C. diamantensis Zone, CPBA 21804. Holotype
CPBA 21801.1, two paratypes: CPBA 21801.2 and 21801.3.
Derivation of name. From Agrio and the Latin noun r
river, because the type locality is by the Agrio River in cen-
tral Neuquén.
Dimensions. Holotype: H= 10 mm; Hlw= 5 mm; Hap= 3.35
mm; D= 4.5 mm; D/H= 0.45; Hlw/H= 0.5; PA= 22.1º.
Paratype (CPBA 21801.2, incomplete): H= 8.2 mm; Hlw=
5.55 mm; Hap= 4 mm; D= 5.1 mm.
Discussion. This Cirsocerithium species clearly displays a
well-preserved apertural varix in several specimens. Addi-
tionally, the shallow pout at the junction of the basal lip
with the end of the columella also justifies the attribution
to this genus.
The lack of a mid-whorl angulation sets the Argentinian
species apart from the type, C. subspinosum. Some species
with a convex whorl profile similar to that of Cirsocerithium
agriorivensis sp. nov. are, for instance, C. aptiense (d’Orbigny,
1843) and C. reticulatum (Nagao, 1934). The former was
collected from the Aptian of SE France (Kollmann, 2005, p.
159, pl. 17, fig. 28) whilst the latter was retrieved from the
upper Aptian–lower Albian of Japan (Kase, 1984, p. 130, pl.
20, figs. 12, 13). Both C. collignoni Kiel, 2006 (p. 459, fig.
3.11–14) and Cirsocerithium lallieranum (d’Orbigny, 1843)
were recovered from the Albian of Madagascar (Kollmann,
2005, p. 160, pl. 17, figs. 26–27) and present a subangular
whorl profile. Cirsocerithium aptiense also bears four spiral
cords on the whorl side and a fifth one just below the adapi-
cal suture, a feature that is present in several other species
but absent in C. agriorivensis. The meaning of such attribute
is not yet clear since all the other features characterizing C.
agriorivensis agree well with the diagnosis of the genus.
Cossmann (1906) included this feature in the original diag-
nosis and stated that the subsutural cord is frequently
beaded, as occurs in C. subspinosum.
Regarding the collabral sculpture, C. agriorivensis is
characterized by low swellings at the intersections of spiral
cords and collabral ribs. Other species present more promi-
nent or even pointy nodes and yet this feature exposes
some intraspecific variability. For instance, the syntypes and
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
several other specimens of C. subspinosum from Europe bear
pointy nodes along the mid-whorl carina of the last and
three to four precedent whorls; however, several other
specimens from around the world present blunter nodes
(see Abbass, 1973, p. 119, pl. 2, figs. 1–2; Kase, 1984, p.
130, pl. 20, figs. 10–11; Kollmann, 2005, p. 159, pl. 17, figs.
24–25). The collabral ribs in C. aptiense are thicker and
wider, and there are deeper-set interspaces between spi-
ral cords. In C. reticulatum, as the specific epithet states, the
sculpture forms a reticulate pattern. The ribs are thinner
than in C. agriorivensis and become even thinner and more
closely spaced towards the aperture while there are four
main spiral cords with finer threads intercalated. Cirsoceri-
thium collignoni exhibits two to three-noded spiral cords and
more numerous secondary spiral threads and collabral ribs.
Two species from the Cretaceous of England provi-
sionally included in the genus by Abbass (1973, p. 120, 121,
pl. 2, figs. 3–4, 8) differ from C. agriorivensis mainly as re-
gards sculpture. More specifically, C.? kirkaldyi Abbass, 1973,
from the Aptian, exhibits stronger collabral ribs and a su-
tural platform with secondary spiral threads while C.? nooryi
Abbass, 1973, from the Cenomanian, lacks well-defined
collabral ribs and presents beaded spiral cords increasing in
number towards the last whorl instead. Cirsocerithium peroni
Cossmann, 1906 (p. 242, pl. 13, figs. 6–7, 11), from the
Cenomanian of Algeria, differs from C. agriorivensis in its very
weak collabral and spiral sculpture. Cirsocerithium harborti
(Wollemann, 1908, p. 179, pl. 13, figs. 5–7), from the Lower
Cretaceous of Germany, can be distinguished from C. agri-
orivensis in terms of its angular whorl profile and coarse
pointy nodes, as observed in C. subspinosum. The sculpture
of Cirsocerithium quadricinctum Kollmann, 1979, from the
Cenomanian of Germany, is similar to that of C. lallieranum,
although the whorl profile in the former is more convex.
These two species are marked by thinner and more nu-
merous collabral ribs that are broken into conspicuous
round nodes by the spiral cords.
Cirsocerithium agriorivensis is seemingly the earliest
record of the genus, as Cirsocerithium antiquum Glasunova,
1968, from the upper Hauterivian of Russia, was recently
reinterpreted by Blagovetshenskiy (2015) as a representa-
tive of the Epitoniidae. All the other records found in the
literature are Barremian or younger in age.
Superfamily and family indeterminate
Genus Cataldia Calzada and Corbacho, 2015b
Type species. Confusiscala caneroti Calzada, 1973 (fig. 1), upper Ba-
rremian–lower Aptian, Spain; by original designation.
Remarks.This is a rather ill-defined genus based on a
species from the Lower Cretaceous of Spain. The available
material of the type and other species lacks complete adult
apertures. This is a recurrent problem with Mesozoic cerithi-
form gastropods that precludes establishing affinities at a
suprageneric level (Saul and Squires, 2003; Ozawa et al.,
The diagnosis provided by Calzada and Corbacho
(2015b) mentioned a homeostrophic, paucispiral and
smooth protoconch as well as a mid-sized cerithiform
teleoconch, slightly convex whorls, tuberculate collabral
ribs, spiral cords, a bicarinate periphery, a feebly convex
base, a straight columella, a thickened parietal lip, an ovate
and slightly dilated aperture and a small angular callus
where the parietal and the outer lip meet. The protoconch
is too poorly illustrated so as to confirm its alleged mor-
phology and the form of the aperture is largely presumed
since it is only partially known. Furthermore, Calzada and
Corbacho (2015b) did not state whether the upper spire
is pyramidal or not. Although the holotype of C. caneroti
presents a clearly pyramidal upper spire, the opposite is in-
dicated in the original description of the species (Calzada,
1973). Other specimens attributed to C. caneroti do not ex-
hibit a pyramidal spire (Calzada, 1989b, pl. 1, figs. 8–9) and
nor do the specimens of Cataldia mirambelensis (Vilanova,
1863, pl. 8, fig. 17), another species from the Lower Creta-
ceous of Spain (Calzada, 1985; Viera, 1991; Calzada and
Corbacho, 2015b). The importance of such feature relies
upon the fact that the material from the Neuquén Basin
lacks a pyramidal spire while other Cretaceous genera with
a similar teleoconch shape and sculpture, such as as Echi-
nobathra Cossmann, 1906, Pyrazopsis Akopyan, 1972 or
Alamirifica, do bear one.
Cataldia is very similar to most batillariids, especially
Batillaria Benson in Cantor, 1842 and Zeacumantus Finlay,
1927. Cataldia is most similar to Batillaria in its conical to
cyrtoconoid shell outline. However, in this genus, spiral
elements of the sculpture are in general more developed
than collabral elements, which are weaker and sometimes
inconspicuous. The periphery is also different, being round
and inconspicuous in Batillaria, and bicarinate in Cataldia.
The shell sculpture in Cataldia is more similar to that of
Zeacumantus since the collabral ribs are more conspicuous,
wide and rounded as well as being subnodulous, orthocline
to slightly opisthocline and straight to opisthocyrt, and
sometimes cut by spiral furrows. They are out of alignment
between successive whorls. The numerous convex to flat
whorls, the straight columella, the bicarinate periphery and
the slightly convex base with or without fine spiral threads
are also similar in both genera. Cataldia somewhat resem-
bles Pyrazus Montfort, 1810 as regards its spire outline and
sculpture, especially in the non-pyramidal spire. The latter
can be distinguished by an angular last whorl with pointed
or spine-like ribs whilst, in Cataldia, the last whorl is convex
as the spire whorls and the nodes are rounded. The aper-
tural morphology in the type species of Pyrazus, P. ebeninus
(Bruguière, 1792), is apparently much more complex than
that of Cataldia as it presents thick and flared outer and
inner lips with a wide siphonal notch and a conspicuous
cerithial canal as well as a ventrolateral varix (Ozawa et al.,
2009). The apertural features so far known for Cataldia
seem much simpler, with a relatively thick and bent parietal
lip and, apparently, a simple and thin outer lip that would
explain its easy fragmentation. Most Cretaceous cerithiform
records with a pyramidal spire had been assigned to Pyrazus
(e.g., Cossmann, 1906; Sayn, 1932; Olsson, 1944; Kase,
1984; Buitrón, 1986; Buitrón-Sánchez and López-Tinajero,
1995; Ayoub-Hannaa and Fürsich, 2011; Kase et al., 2015)
but Saul and Squires (2003) and Ozawa et al. (2009) ascribed
them all to different genera.
Cataldia resembles the spire of some species attributed
to Eustoma Piette, 1855 such as E. forneri Calzada, 1996. The
main difference between Cataldia and Eustoma is that the
latter has very prominent pointed nodes in the last whorl
formed by fusion of the nodes in the spiral rows of the spire.
Calzada and Corbacho (2015b) ranked Cataldia within
the Batillariidae and, in that respect, Cataldia is consistent
with most of the diagnostic features listed for Batillariidae
s.l. by Ozawa et al. (2009). However, other than the general
resemblance as regards shell shape and sculpture, there
are no further grounds for this attribution. For instance, the
teleoconchs of representatives of other cerithiod families,
e.g. Potamididae, are also similar to that of Cataldia. Fur-
thermore, the holotype illustrated by Calzada and Corbacho
(2015b) is similar to a juvenile of Campanile sp. illustrated
by Bandel (2006, pl. 10, fig. 11). Therefore, the attribution
of this genus to any family known so far will not be pursued
herein in view of the lack of details on protonch and aper-
ture morphology.
Cataldia?binodosa sp. nov.
Figure 5.13–17, 5.19
Diagnosis. Cataldia with flattish to convex whorls bearing
broad, rounded and out-of-alignment collabral ribs, ortho-
cline to slightly opisthocline and straight to opisthocyrt,
crossed by shallow spiral depression that splits them into
two node-rows, the abapical one slightly more prominent
towards last whorl.
Description. Shell mid-sized, conical to slightly cyrtoconical.
Protoconch and first teleoconch whorls missing. Teleoconch
with up to seven whorls preserved. Spire high, repre-
senting nearly 55% of the total shell height. Suture slightly
canaliculated, bordered by suprasutural spiral cord. Whorls
flat to convex. Sculpture of thick, wide collabral ribs on all
teleoconch whorls, 10–13 on penultimate whorl. Ribs or-
thocline to slightly opisthocline and straight to opisthocyrt
on upper spire, wider on middle part and tapering towards
sutures. Ribs crossed by shallow spiral depression that
splits them into two connected nodes. Abapical row of
nodes slightly more prominent towards last whorl. Ribs
equidistant and out of alignment between succeeding
whorls. Interspaces concave and narrower than ribs. Num-
ber of ribs increasing slightly with ontogeny. Fine, subequal
spiral threads covering all whorls, not observed on base,
18–20 on penultimate whorl. Periphery bicarinate; carinae
smooth to slightly nodose. Base flat. Growth lines ortho-
cline and opisthocyrt. Columella straight. Aperture incom-
plete; parietal lip thick, not forming a callus, continuous with
columellar lip, thick and raised. Parietal lip meeting outer lip
in acute angle, slightly projecting adapically from peristome
but not forming true posterior channel and without parietal
ridge. Basal and outer lips unknown.
Occurrence.The material studied herein comes from six lo-
calities in central Neuquén province, in late Hauterivian–
early Barremian strata near the top of the Agua de la Mula
Member of the Agrio Formation.
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
Material.A total of 76 specimens; one specimen from El
Gasoducto, ?P. groeberi Zone, CPBA 21296; 59 specimens
from Salado Norte, P. groeberi/S. riverorum zones, CPBA
21798.1–6 and 21797.1–53; two specimens from Agua de
la Mula, P. groeberi Zone, CPBA 21795 and CPBA 21796;
seven specimens from Bajada Vieja, S. riverorum Zone, CPBA
21799.1–4 and CPBA 21297.1–3; one specimen from Cerro
Marucho, ?C. diamantensis/P. groeberi zones, CPBA 21298;
six specimens from Aguada Florencio, CPBA 21299.1–5 and
CPBA 21300. Holotype CPBA 21796 and two paratypes:
CPBA 21797.1 and 21797.2.
Der ivation of name. From the Latin adjective n ōdōsa ,
meaning ‘having or covered with small knobs’, owing to the
pair of nodes formed by the splitting of each collabral rib.
Dimensions. Holotype (incomplete): H= 40.3 mm; Hlw=
21.45 mm; D= 18.8 mm; D/H= 0.46; Hlw/H= 0.53; PA=
17.6º. Paratype (CPBA 21797.1, incomplete): H= 31.4 mm;
D= 16.15 mm; D/H= 0.47.
Discussion. Although the aperture and early whorls are not
preserved in the available specimens, the teleoconch mor-
phology, especially the sculpture, suggests that the closest
genus is Cataldia. The species resembles many batillariids
and particularly Batillaria and Zeacumantus, as well as some
potamidids, but these are all recent genera with a fossil
record restricted to the Cenozoic. Nevertheless, the assign-
ment of the species to Cataldia is only tentative since the
aperture in this genus is not fully known either and the
meaning of the apparently pyramidal spire of the type
species is unclear. The studied material is considerably
similar to the specimens of C. caneroti illustrated by Calzada
(1989b, pl. 1, figs. 8–9). However, in the well-preserved
specimen of figure 9, the observed collabral ribs are
straighter than those of C.? binodosa and the adapical node
row is slightly more prominent instead of the abapical one
as in the Argentinian species. Besides, the peripheral spiral
thread is visible thorughout most of the spire whorls whilst,
in C.? binodosa, it can only be seen in the periphery of the
last whorl. The early Hauterivian species C. mirambelensis
differs from C.? binodosa in presenting seven to nine fine
spiral threads with finer intercalating lines.
Pyrazus? scalariformis Nagao, 1934 (p. 257, pl. 35, figs.
10, 10a,b, pl. 36, fig. 24; see also Kase, 1984, p. 137, pl. 20,
figs. 18–19), from the upper Aptian–lower Albian of Japan,
resembles the Argentinian species in its convex whorls with
broad, rounded and out-of-alignment collabral ribs crossed
by spiral cords. The species is also characterized by the
adapical part of its outer lip being thickened and dilated as
well as extended towards the spire. Even though Calzada
and Corbacho (2015b) tentatively included this species
within Cataldia, its outer lip morphology has not been ob-
served in other species of the genus. Ozawa et al. (2009) had
previously assigned this species to Pyrazopsis? and yet,
given its lack of a piramidal spire and beaded spiral cords, it
would not fit into this genus either.
Pyrazus quinquenodosus (Mertin, 1939, p. 210, pl. 6, fig.
7e; see also Akopyan, 1974, p. 238, pl. 126, fig. 11), from
the Lower Cretaceous of Germany and Armenia, also bears
a resemblance with C.?binodosa as regards teleoconch
shape and sculpture. Yet, its collabral ribs seem fainter than
those observed in the Argentinian species.
Two relatively abundant taxa provisionally attributed
to Potamides Brongniart, 1810, in its broadest sense, were
described from the Upper Cretaceous of Patagonia (Griffin
and Varela, 2012). Although the specimens are poorly pre-
served and present variability in the sculpture, slight simi-
larities with the species herein described can be observed
in terms of their convex whorls, their thick, opisthocyrt,
subnodulose collabral ribs and the bicarinate periphery they
bear. Additionally, these specimens differ from C.? binodosa
mainly in that they display five conspicuous spiral cords that
divide each rib into five rounded nodes as opposed to the
ribs split into two nodes that characterize C.? binodosa.
Uchauxia fraasi Alencáster, 1956 (non Blanckenhorn,
1890), from the Aptian of Mexico, greatly resembles C.?
binodosa and could also be congeneric with it as these
species are similar in size, teleoconch outline, spiral and
collabral sculpture, periphery and base. The Mexican species
can be however distinguished by its slightly larger number
of collabral ribs per whorl and the more numerous fine spi-
ral threads that cover both its whorl face and its flat base
(Alencáster, 1956, pl. 6, fig. 6). Unfortunately, the aperture
in U. fraasi sensu Alencáster (1956) is unknown. Anyways,
it is clear that this species does not belong in Uchauxia
Cossmann, 1906, which is more similar to Procerithium and
Rhabdocolpus but for its conspicuous, short and twisted
anterior canal (Abbass, 1973). Conversely, Uchauxia? poblana
Alencáster, 1956 (pl. 6, figs. 1, 2), although similar in spire
shape and sculpture, and judging by the prominent and
pointed nodes that form in its last whorl, seems to belong in
Superfamily PSEUDOMELANOIDEA Fischer, 1885
Family PSEUDOMELANIIDAE Fischer, 1885
Remarks.Pseudomelaniidae is a problematic group based
on a genus which is often a wastebasket taxon and that, in
turn, has a poorly known type. Often, species with mid-sized
to large, slender conical and anomphalous teleoconchs,
smooth or with inconspicuous sculpture and with parasig-
moidal growth lines are included in Pseudomelania Pictet
and Campiche, 1862 (Gründel, 2001). Pseudomelaniids are
also distinguished by their inner lip callus without folds
(Squires and Saul, 2004). That being said and thus far,
pseudomelaniids are, among the Mesozoic marine caeno-
gastropods, the closest to the specimens from the Neuquén
Basin as regards teleoconch morphology.
Genus Paosia Böhm, 1895
Type species.Natica fadaltensis Böhm, 1895, Cenomanian, Italy; by
original designation.
Remarks.Squires and Saul (2004) revised the genus, its
stratigraphic range and the geographic extension of its
occurrence. According to these authors, Paosia may have
originated towards the end of the Jurassic in Eastern Europe
and reached North America by the Aptian. So far, there were
no records of the genus in South America and most of the
Austral world (Squires and Saul, 2004, fig. 2).
The diagnosis of Paosia indicates that it presents an
elongate-conical adult shell, a spire that can be high or low,
whorls that may bear no sculpture or rarely display fine spi-
ral grooves, a columella that usually has a callus, sinuous
growth lines and a basal lip curved anteriorly and forming a
triangular projection (Squires and Saul, 2004).
Paosia? sp.
Figure 5.18, 5.20–22
Description. Shell medium-sized, slightly cyrtoconoidal, oval
in outline. Protoconch and first teleoconch whorls not pre-
served. Teleoconch with up to five preserved whorls. Spire
moderately high, representing nearly 30% of the total shell
height. Suture impressed. Spire whorls slightly convex. Last
whorl sub-cylindrical, with convex sides, diameter slightly
below mid-whorl. Whorls smooth but for very fine growth
lines. Periphery gently rounded; base convex. Growth lines
orthocline and straight to slightly opisthocyrt near mid-
whorl, markedly prosocyrt at base. Aperture holostomate,
obliquely oval in outline; outer lip and parietal lip joining in
acute angle slightly dropping relative to suture line. Outer
lip simple, straight and vertical. Basal lip not fully preserved,
with slightly thickened margin. Parietal lip flat, oblique and
slightly thickened. Columellar lip flat to concave, oblique to
vertical, slightly thickened.
Occurrence. This species occurs in the upper part of the Agua
de la Mula Member of the Agrio Formation; that is, in the C.
diamantensis and P. groeberi zones. It was recorded from
both central Neuquén and southern Mendoza.
Material. Fifteen specimens; five specimens from Agrio del
Medio, CPBA 21794.1–5, P. groeberi Zone; one specimen
from Bajada Vieja, CPBA 21294, C. diamantensis Zone; two
specimens from Agua de la Mula, CPBA 21295.1–2, P. groe-
beri Zone; six specimens from Lomas Bayas, MCNAM-PI
24492, P. groeberi Zone; one specimen from Lagunitas Este,
MCNAM-PI 24493, P. groeberi Zone.
Dimensions. CPBA 21294 (incomplete): H= 62.3 mm; Hlw=
43.9 mm; Hap= 30.2 mm; D= 29.3 mm; D/H= 0.47; Hlw/H=
0.7; PA= 23.2°. CPBA 21794.1 (incomplete): H= 56.5 mm;
Hlw= 36.25 mm; Hap= 24.9 mm; D= 23.2 mm; D/H= 0.41;
Hlw/H= 0.64; PA= 29.5º.
Discussion. The Neuquén specimens resemble Paosia in their
teleoconch profile and the subcylindrical last whorl of the
most elongate species of this genus. They however differ in
that the aperture in most Paosia species is lower relative to
the height of the last whorl and their growth lines are more
sinuous than in the Argentinian species. Moreover, given
that the basal lip of the available specimens of Paosia? sp. is
not fully preserved, it cannot be compared with the trian-
gular projection that is diagnostic of the genus.
Among all the known species of Paosia, Paosia? sp. re-
sembles P. acuminata (Anderson, 1958) in its larger adult
shell size, its taller spire outline, its narrower pleural angle,
its higher last whorl and its lack of sculpture. However, this
species is based on a weathered holotype and the basal lip
is not preserved either.
Paosia? sp. also resembles some Recent or Cenozoic
AMEGHINIANA - 2017 - Volume 54 (4): 405 – 440
fresh- or brackish-water genera of the cerithioid families
Thiaridae, Pleuroceridae and Pachychilidae. Although most
such families are not represented in the Cretaceous, the
similarities among them and Paosia? sp. include the teleo-
conch shape, the apertural morphology and the sculpture.
This resemblance may be due to convergence since the
shells in these families are actually often very variable in
sculpture and shell shape both inter- and intraspecifically.
The species herein discussed is very similar to the Recent
freshwater genus Bayania Hébert and Munier-Chalmas,
1877 (Cerithioidea, Thiaridae) in its elongate-oval cyrto-
conoidal teleoconch outline, its tall and subcylindrical last
whorl, its broadly round periphery, its slightly convex spire
whorls and its slightly opisthocyrt growth lines with a
prosocyrt sinus towards the base. Additionally, their aper-
ture is similar; that is, oval with an acute adapical margin
and a broadly rounded abapical one, as well as a simple
and vertical outer lip and a straight to slightly concave
and slightly thickened columellar lip. The sutures in the
type species of Bayania, B. lactea (Lamarck, 1806), and the
Neuquén specimens are, when considering that they both
present a slightly irregular trace in some parts and drop
near the aperture, similar as well. The early spire whorls in
B. lactea show collabral ribs and spiral cords and, although
such whorls are not well preserved in the available speci-
mens, they seem to be smooth. The basal lip in B. lactea is
somewhat flared and forms a shallow sinus yet cannot be
compared with that of the Neuquén specimens for their
basal lip is not fully preserved. Moreover, B. lactea is much
smaller than the specimens studied herein, reaching 30 mm
in shell height while other species are frequently below 10
mm (Gougerot and Le Renard, 1983). Only a few Cretaceous
records of Bayania were reported from the Upper Creta-
ceous (Campanian–Maastrichtian) of southern India and
Europe by Cossmann (1909b) and, furthermore, their attri-
bution is dubious.
Superfamily VANIKOROIDEA Gray, 1840
Family ?VANIKORIDAE Gray, 1840
Remarks. According to Cossmann (1925), vanikorids are
characterized by an invariably open and deep umbilicus
whilst their teleoconch, normally small and globose, may be
highly variable in shape, and their peristome is round and
prosocline (Tunnell et al., 2010). Cossmann (1925) described
the protoconch of vanikorids as smooth, slender and pointed.
However, Bandel (2006, pl. 2, figs. 8, 10) illustrated the pro-
toconch of a species of Vanikoro Quoy and Gaimard, 1832
by depicting three round whorls of which one was a smooth
embryonic whorl while the remaining two were larval
whorls bearing beaded spiral cords.
The stratigraphic range of Vanikoridae depends on
whether or not Vanikoropsis Meek, 1876 is included within
(see discussion below). If so, its earliest records could date
as far back as the Early Cretaceous.
Genus Vanikoropsis Meek, 1876
Type speci es. Natica tuomeyana Meek and Hayden, 1856 (p. 270),
Maastrichtian, USA; by original designation.
Remarks. The holotype of V. tuomeyana is an incomplete
specimen lacking the apertural area and only presenting a
part of the last whorl preserved and a considerably worn
spire (Sohl, 1967; Erickson, 1974). This specimen has a
relatively thick shell, a large and globose last whorl, a wide
conical and depressed spire and a narrow umbilicus. Its
sculpture consists of spiral striae and collabral growth
rugae, i.e., thick, broad and irregular ribs. Whitfield (1876)
described topotypes with a slightly taller spire and more
conspicuous rugae. Sohl (1967) included thin-shelled species
within Vanikoropsis and therefore expanded the morpho-
logical range of the genus. According to Erickson (1974),
this genus resembles Spironema Meek, 1864 (Family Littori-
nidae), thus exposing the need for a so far unachieved revision
of these genera based on more abundant and better material.
Meek (1876) tentatively assigned Vanikoropsis to
Vanikoridae on the basis of its similarity with Vanikoro, type
genus of the family. These species are similar in their general
shell outline and their sculpture of wide spiral threads and
deep striae. Although several authors followed this classifi-
cation (e.g., Sohl, 1967; Thomson, 1971; Erickson, 1974;
Kase, 1984; Stilwell and Henderson, 2002; Kollmann, 2005),
there were some exceptions (e.g., White, 1889; Pchelintsev,
1927; Beisel, 1983; Caze et al., 2011). Sohl (1967), in par-
ticular, emphasized the strong resemblance between
Vanikoropsis and Vanikoro cancellata (Lamarck, 1822), the
former differing only in having a thicker shell, a lower spire
and a rounder aperture. Cossmann (1907, 1925) and Coss-
mann and Peyrot (1919) argued that the thick shell, broad
aperture, inner-lip callus and closed umbilicus do not match
the diagnosis of Vanikoridae. Accordingly, Cossmann (1925)
included the genus within the Ampullinidae. Sohl, 1967 (pl.
5, figs. 15, 16) re-illustrated the holotype of V. tuomeyana
displaying its actually narrow umbilicus.
The shell shape and sculpture in Vanikoropsis are evi-
dently convergent with other gastropod taxa. A revision
should also consider protoconch morphology for a safer
suprageneric placement. Sohl (1967) described the proto-
conch of V. nebrascensis (Meek and Hayden, 1860), from the
Maastrichtian of Wyoming, USA (Sohl, 1967, p. B22, pl. 5,
figs. 1, 5–10, 12, 14, 17; pl. 6, figs. 1–4, 11; Erickson, 1974,
p. 170, pl. 15, figs. 1–3), as dome-shaped, paucispiral and
smooth. Although poorly preserved, the protoconch of V.
demipleura Stilwell and Henderson, 2002, from the Ceno-
manian of Australia, is also paucispiral.
Sohl’s (1967) criterion is herein adopted and the genus
is accordingly tentatively included within Vanikoridae.
The stratigraphic record of Vanikoropsis crosses the
Jurassic/Cretaceous and Cretaceous/Paleogene boundaries
(Rosenkrantz, 1970; Kollmann and Peel, 1983; Gerasimov,
1992), and the genus was rather widespread during the
Early Cretaceous.
Vanikoropsis?leviplicata sp. nov.
Figure 6.1–7
Diagnosis.Vanikoropsis with moderately thick shell, low
spire, moderately marked growth rugae, umbilicus closed
and partially covered with callus, ca. 20 band-like spiral
cords and lacking secondary spiral striae.
Description. Shell small, turbiniform, slightly taller than
wide, moderately thick, with regularly expanding whorls.
Apical whorls apparently dome-shaped, paucispiral, smooth.
Teleoconch with four to five preserved whorls. Spire low,
representing approximately 25% or less of the total shell
height. Suture impressed to slightly canaliculated. Whorls
strongly convex. Last whorl large and swollen, slightly taller
than wide, maximum diameter slightly above mid-whorl.
Umbilicus closed, umbilical area partially covered by inner-lip
callus. Aperture incomplete, holostomate, slightly proso-
cline, peristome round to slightly ovate, subangular adapi-
cally, round abapically. Outer lip not preserved. Inner lip
flat to convex on parietal area, callus thick and narrow.
Columella concave. Sculpture of wide, band-like spiral cords
separated by spiral striae. Cords twice as broad as striae,
nearly 20 on last whorl. Growth lines prosocline and straight.
Growth rugae on last and penultimate whorl; irregular,
parallel to growth lines, accentuated on adapical third of
whorls. Periphery inconspicuous. Base convex, with spiral
cords and growth lines.
Occurrence.Vanikoropsis?leviplicata sp. nov. was recorded
from the upper Hauterivian, Agua de la Mula Member of
Agrio Formation, in few loc</