Contr. Tert. Quateni. Geol 37(3-4) 57-65 4 figs. Leiden, December2000
The genus Solariella
(Mollusca, Archaeogastropoda)
from the Pliocene of Vale de Freixo, Portugal: palaeobiogeographic and palaeoclimatic implications
Carlos Marques+da+Silva
Universidade de Lisboa
Lisboa. Portugal
Bernard Landau
InternationalHealth Centres
Albufcira, Portugal
and
Jordi Martinell
Universitat de Barcelona
Barcelona. Spain
& from the Plio- Silva, Carlos Marques da, Bernard Landau Jordi Martinell. The genus Solariella (Mollusca, Archaeogastropoda)
— 57- cene ofVale de Freixo, Portugal: palaeobiogeographic and palaeoclimatic implications. Contr. Tert. Quatern. Geol., 37(3-4):
65, 4 figs. Leiden, December 2000.
the first time from Pliocene In the present paper, trochid gastropod Solariellacincta (Philippi, 1836) is recorded for the (Piacenzian) strata exposed at Vale de Freixo (Pombal, central-west Portugal). This record of the species constitutes the first from the Atlantic
Neogene; the taxon is here compared with other Miocene to Recent European species ofSolariella. At present, S. cincta is restricted in Mediterraneanand the to the coast ofWest Africa. During the Late Pliocene, it had a much wider distribution, occurring the along
at least far north central-west Iberia. The of benthic such as S. European Atlantic coasts, as as presence thermophilic gastropods cincta, Tribia uniangulata (Deshayes, 1830), Solatiapiscatoria (Gmelin in Linné, 1790), Ancilla sp., Ficus sp., and Strioterebrum than still sp. in Pliocene strata at Vale de Freixo, clearly indicates that relatively high water temperatures (i.e. warmer today) pre- the Atlantic this between 3.2-3.1 and 2.7 Ma. vailed, at least sporadically, along European coast at latitude, c.
Key words —Gastropoda, Trochidae, Pliocene, Portugal, palaeobiogeography, palaeoecology.
de Universidade de da Escola P-1250 102 C M. da Silva, Departamento e Centro Geologia, Lisboa, Rua Politecnica, 58, Lisboa,
Portugal [e-mail: [email protected]]; B.M. Landau, InternationalHealth Centres, Avenida Infante Dom Henrique 7, Areias de
Sao Joao, P-8200 Albufeira, Portugal [e-mail: [email protected]]; J. Martinell, Departament d'Estratigrafia i Paleontolo- gia, Facultat de Geologia, Universitat de Barcelona, E-08028 Barcelona, Spain [e-mail: [email protected]].
Contents Introduction
molluscs from central-west Introduction p. 57 Although Pliocene marine
have been known for than hundred Systematic palaeontology p. 58 Portugal more one
Discussion Choffat. of the classic p. 62 years now (see e.g. 1889), none
Conclusion 63 localities has a fauna as diverse or well p. produced pre-
served that at Vale de Freixo in the Pombal Acknowledgements p. 63 as region
References p. 64 (Fig. 1). 58
the location of the Vale de Freixo in central-west Fig. 1. Map showing outcrop Portugal
The Pliocene sequence in this region consists oftwo affinity, as defined by Raffi et al. (1989). The chrono-
members, the Formagao Arenito de Carnide below, and logic overlap between biozone CN12a and molluscan
time Formagao Arenito de Roussa-Paredes above. The for- unit MPMU2 provides a more precise assignment
mer unit comprises barren, fine, silty, micaceous sand. ofBed 3 deposition at Vale de Freixo, viz. between 3.2-
the last Locally, the lowermost portion of this formation con- 3.1 and 2.7 Ma, the latter documenting appear-
tamalis tains a basal conglomerate and a sand rich in marine ance datum (LAD) of Discoaster (see Silva,
molluscan shells. At Vale de Freixo, the maximum 1995).
thickness of the basal fossiliferous beds of the Forma-
gao Arenito de Carnide amounts to approximately 1 m
(Fig. 2). These beds are remarkable for their relatively SYSTEMATICPALAEONTOLOGY
abundant, well-preserved macrofossils, mostly bivalves
and Gili for gastropods (see et al., 1995, more details). Superfamily Trochoidea Rafinesque, 1815
The material studied for the present paper was col- Family Trochidae Rafinesque. 1815
lected from Bed 3. Subfamily SolariellinaePowell. 1951
The molluscan assemblage from Vale de Freixo Genus and subgenus Solariella Wood. 1842
indicates a shallow marine, infralittoral environment
with relatively high water temperatures (Silva, 1993a;
Gili et al., 1995; Nolf& Silva. 1997). The fauna shows Solariella(Solariella) cincta (Philippi, 1836)
an interesting combination of Mediterranean and Fig. 4
northern European Pliocene species (Gili et al., 1995),
in addition to a number of probable endemics, most of
which await description. 1836 Trochus cinctus Philippi, p. 185, pi. 10, fig. 20.
1898 Gibbula P. Fischer — According to Cachao (1990). the calcareous nan- inoptanda Locard, p. 51, 1, 24-27. nofossil assemblage of Bed 3 at Vale de Freixo indi- pi figs
1916 Solariella cincta (Philippi, 1836) — Cerulli- cates placement in the Discoaster tamalis Zone Irelli, p. 187, pi. 21, figs 23-25 (typical), fig. 26 (CN12a, see Okada & Bukry, 1980), i.e. Upper Plio- (var. depressa Seguenza), fig. 27 (var. conica Ce- cene. Piacenzian {sen.su Berggren et al., 1995). The rulli-Irelli). molluscan faunas from this bed allow assignment to the 1993 Solariella cincta (Philippi, 1836) — Waren, p Mediterranean Pliocene Molluscan Unit 2 of Raffi & 161, fig. lb, c. Monegatti i.e. the 3.2-3.1 Ma eco- (1993), postdating — 1993 Solariellainoptanda (Locard, 1897) Waren, p
extinction event and lo- biostratigraphic (immigration 161, fig. 2e.
cal of benthic molluscan taxa of — extinction) tropical 1993b Solariellasp. Silva, p. 116, pi. 2, figs 1-3 59
Fig. 2. Stratigraphy ofthe Vale deFreixo outcrop, representing the lowermost portion of the Pliocene (Piacenzian) sequence in the
Pombal region (central-west Portugal).
cords Diameterof 320-360 Material — Over 30 well-preserved specimens (Silva spiral (Fig. 4d-f). protoconch and Landau all from nucleus 180-200 Shell collns), representing growth stages, pm, of pm. small, trochiform,
Bed 3 at Vale de Freixo (Pombal region, central-west maximum height 8.6 mm, maximum width 10.0 mm;
Portugal); Pliocene, Piacenzian. teleoconch of 6 whorls with a prominent, subhorizontal,
Diagnosis — A medium-sized Solariella with an angu- concave subsutural ramp, inward sloping in early lar periphery on the spire whorls, rounded body whorl, whorls, outward sloping in subsequent whorls. Whorl
with ornament of three strong primary cords additional profile below subsutural ramp flat on early whorls, con- secondaries whorls and on later a wide, deep, ridged cave on body whorl. Teleoconch ornament of two umbilicus. granulose primary spiral cords on the first whorl, with a
Description — Protoconch homeostrophic, paucispiral, third appearing towards the end of the second; adapical
delineated from telcoconch, of about sharply consisting cord defines outer limit of subsutural ramp. Below,
whorls with elevated nucleus. 1.25 a large, slightly whorl is flattened and slopes at an angle towards abapi-
Whorl ornament consisting of several (3-4 ?) very fine cal cord, from which whorl profile drops vertically to- 60
wards suture, which is narrow, linear and shallow; ir- tions of spiral cords; parietal lip adherent to body whorl regularly spaced spiral secondaries and tertiaries appear with no callus formation.
— similar the in interspaces between the three primaries on later Comparisons Solariella cincta is to Re- whorls. Axial ornament of numerous weak growth lines cent S. amabilis (Jeffreys, 1865), which ranges from
overlying spiral ornament and forming granulose cords. southwest Iceland to the coast of western Morocco;
it has wider and ornamented Growth lines most prominent over abapical cord, giving however, a more coarsely
colour it a finely beaded appearance, strongest on the early umbilicus, more convex whorls, a prominent
whorl well and smaller teleoconch whorls. Body developed, com- pattern a protoconch (Waren, 1993, p. 161).
prising two-thirds of total shell height; whorl profile There is also a resemblance to Solariella maculata rounded rather than angular as in earlier teleoconch Wood, 1842 (p. 531, pi. 5, figs 7, 10), which is endemic
whorls. Base flattened, concave with wide, deep umbili- to the Lower-Middle Pliocene of the North Sea Basin
half of base. Ornament of This form has rounded, rather cus, occupying the diameter (Marquet, 1995, p. 64).
5-10 subequal spiral cords, wider than interspaces. Um- than angular whorls and evenly spaced spiral keel- bilicus delimited by a wider periumbilical cord crossed shaped cords, and also differs from S. cincta in other
by numerous axial growth lines forming ridges on the details of ornament. Traces of coloration are also pres-
cord. Inner face of umbilicus with 7-8 spiral cords, ent in many specimens of S. maculata (see Gevs &
finely ridged by numerous, closely spaced axial growth Marquet. 1979. p. 68, pi. 27, fig. 5). but appear as radial
lines. Aperture circular, with continuous peristome, lip spots rather than vertical flammules.
thin and sharp with a sinuous edge, caused by elonga-
Fig. 3. Stratigraphical and geographical distribution ofSolariella (S.) cincta (Philippi, 1836). 61
Fig. 4. Solariella (S.) cincta (Philippi, 1836), VFX.03.026 (Silva Colln), Upper Pliocene (Piacenzian), Vale de Freixo (Pombal
A - 10.0 B - - region, central-west Portugal); dorsal view (height 8.6 mm, diameter mm); apertural view; C umbilical view;
D-F - protoconch (scale bar 100 µm). 62
Two allied species occur in the Italian Pliocene. One Solariella sp.), the Mediterranean, southern Spain
Solariella which of these, peregrina (Libassi. 1859), is (Estepona. Zanclean. pers. obs.), and ?Italy (Sicily and also known from the Lower Pliocene (Zanclean) of Calabria. ?Pliocene; see Cerulli-Irelli, 1916; Waren,
southern Spain, is readily distinguished from S. cincta 1993), and the Pleistocene of the Mediterranean. Italy
axial Cavallo & Pleisto- by a stronger ornament (see Repetto. (Monte Mario, ?Sicily and ?Calabria, Lower
Solariella At 1992; Pavia, 1975). pliobscura Sacco, 1896, cene; see Cerulli-Irelli, 1916; Waren, 1993). present,
has an angular whorl profile, but an ornament consist- S. cincta occurs off the coast of West Africa, under the
of weak, cords of S. ing regular, closely spaced spiral (see name inoptanda (see Waren, 1993).
Ferrero-Mortara et al., 1984. pi. 49, fig. 4a-d). Palaeoecology — At Vale de Freixo, S. cincta is found
Other related species occur in the Miocene of the in fine sandy sediments, co-occurring with molluscs
North Sea Basin. The specimen assigned to Solariella (Silva, 1993a; Gili et al., 1995) and fish (Nolf & Silva. aff. duvergieri Cossmann & Peyrot, 1916 bv Janssen 1997) that indicate a normal salinity, shallow (infralitto-
(1984, p. 122, pi. 44, fig. 4a-c) has an angular whorl ral) marine environment with a fine sandy substrate.
profile, but is less depressed and lacks secondary spiral Associated with S. cincta are other trochid gastropods
ornament. Solariella marthae Kautsky, 1925 (see An- such as Clanculus corallinus (Gmelin, 1791), Clelan-
derson, 1964, p. 197, pi. 12, fig. 93a, b; Janssen, 1984. della miliaris (Brocchi, 1814), Gibbula cf. subciner- p. 123, pi. 44, fig. 5a-d) has an ornament which is very aria(?) (cTOrbigny, 1852), Gibbula cf. adansonif(?)
similar to that ofS. cincta, but the shell is less depressed (Payraudeau, 1826), and Calliostoma cf. zizyphinum and has stronger axial ornament on the adapical cord (Linne. 1758). and umbilicus. The specimens recorded by Janssen Extant members of genus Solariella, e.g. S. amabilis
(1984) show these species to be much smaller than the (see Graham, 1988), normally are infralittoralto bathval
Portuguese one. (up to 1.000 m deep) in their distribution, being
From the Miocene of Colli Torinesi (Italy), Solari- epibcnthic on sandy and gravelly bottoms. According to ella taurocincta Sacco, 1896 has a depressed shell and Fretter & Graham (1977), S. amabilis is either a ciliary beaded adapical cord like S. cincta, but stronger keel- feeder or collects detritus from the bottom. Graham
shaped spiral cords. This form is most similar to S. du- (1988, p. 100) wrote, 'Its way of life is unknown ( )'.
vergieri, differing mainly in being more depressed. In
the same paper. Sacco (1896) described a second spe-
cies. S. taurobella, from the same horizon. Unfortu- DISCUSSION
nately, specimens of this species have not been illus-
trated nor described in the subsequent literature. With The Miocene-Recentgenus Solariella (see Knight et al.,
only Sacco's figures in hand, this species appears to be 1960) is widely distributed in Neogene faunas of
indistinguishable from its congeners. The description Europe, with records from the North Sea Basin as fol-
suggests a shell with a deeper suture, differing from S. lows: Miocene (Burdigalian-Lower Langhian) of the
cincta in details ofornament. Netherlands (Janssen, 1984), Miocene (Upper Serra-
Solariella duvergieri and S. contabulata Cossmann valian-Messinian) of Denmark (Rasmussen, 1968) and
& Peyrot, 1916 from the Burdigalian and 'Helvetian' of Germany (Anderson, 1964), Pliocene (Piacenzian) of
France, respectively, are much smaller with less de- East Anglia (England) (Wood. 1842. 1848; Harmer.
pressed shells, although they have the same elements of 1923) and Pliocene (Zanclean-Piacenzian) of Belgium axial and spiral ornament as does S. cincta. (Nyst. 1878-1881; Marquet. 1995). In the Atlantic Neo-
Remarks — Solariella cincta is common at Vale de gene, there are records from the Miocene (Burdigalian)
Freixo, being represented in our collections by over of Aquitaine (SW France) (Cossmann & Peyrot, 1916-
thirty, well-preserved specimens, most of them showing 1919) and the Pliocene (Piacenzian) of Portugal (Silva,
traces of their original colour pattern of vertical stripes 1993b; present paper).
or flammules; nacre can be seen where the upper shell There are also records from the Pliocene of north-
layer is missing. There is quite a range of intraspecific west Africa (Dar-bel-Hamri, Morocco; Zanclean, see
variation, both in ornament (with different relative Lecointre, 1952), the Miocene of Italy (Piedmont;
strengths of primaries and secondaries) and shell pro- 'Helvetian', see Sacco, 1896) and the Pliocene of south-
file. Both extremes of spire height, i.e. squat S. cincta ern Spain (Estepona; Zanclean, see Vera-Pelaez et al.,
S. var. depressa, and high-spired cincta var. conica, as 1995) and Italy (Piedmont; Zanclean-Piacenzian. sec
illustrated by Cerulli-Irelli (1916, pi. 21, figs 26, 27, Sacco, 1896; Pavia, 1975; Cavallo & Repetto. 1992; respectively), are represented at Vale de Freixo, with Monte Mario. Sicily and Calabria. ?Plio-Lower Pleisto-
numerous intermediate gradations. cene. see Cerulli-Irelli. 1916). The last representatives
Stratigraphical and geographical distribution (Fig. 3) of Solariella in the Mediterranean occurred during the
— To date. Solariella cincta has been recorded from the Pleistocene.
Pliocene (Piacenzian) of the Atlantic (Portugal, the pre- In extant European faunas, the genus is represented
sent paper; see also Silva. 1993b. under the name of by a single species, S. amabilis (Jeffreys, 1865), which 63
is restricted to the Atlantic coast, being found from the et al., 1995; Stanley & Ruddiman, 1995). This second
Bay of Biscay to the Shetland Islands (Graham, 1988; Pliocene cooling pulse resulted in the total disappear-
of Terebridae from Atlantic Poppc & Gotto. 1991). Although now confined to the ance the European coast
Atlantic, S. amabilis extended into the Mediterranean and the Mediterranean (Raffi & Monegatti, 1993). The
during Early Pliocene times and is commonly found in above-mentioned thermophilic taxa probably migrated
Zanclean Velerin the and Mediterranean strata of age exposed at (Estepona, southwards, leaving European
coasts, result of this event. These southern Spain; pers. obs.). as a particular extinction Solariella cincta was first described from the Sicil- Early/Late Pliocene migration and local (eco-
ian Plio-Pleistocene; it occurs in Lower Pleistocene de- biostratigraphic) events of western and eastern North
posits of mainland Italy (Cerulli-Irelli, 1916; Warén, Atlanticthermophilic molluscs are collectively classified
S. is found off the of Barnes al. Global Event of 1993). At present. cincta coast by et (1995, p. 320) as a third rank in West Africa, under the name of Solariella inoptanda relatively small order (E'/L' Plio event: a
(Locard. 1897), now considered a junior synonym of S. total of five), in what they labelled as a '(....) very rough
cincta (see Waren, 1993). and relative classification.'
The present record of the species is the first from the
Iberian Neogene. and extends the palaeogeographic
Atlantic. CONCLUSION range from the Mediterraneaninto the
Palaeoclimatic implications — The presence in the
Portuguese Pliocene (Piacenzian) of representatives of At present, Solariella cincta occurs only off the coast of
and that thermophilic genera species at present occur West Africa. During the Late Pliocene this species had a
only further south (i.e. off the coast of West Africa), much wider distribution, occurring in the Mediterranean
S. Other does not exclusively relate to cincta. species and along the European Atlantic coast, at least as far
and such Tribia and Solatia genera, as uniangulata pis- north as central-west Iberia.
both found at the and at catoria, same locality present The presence of thermophilic benthic gastropods
from the Atlantic and Mediterranean missing European such as Solariella cincta, Tribia uniangulata, Solatia
but off the West African coast. Simi- and Strioterebrum coasts, occurring piscatoria, Ancilla sp., Ficus sp., sp.
larly, genera such as Ficus, Ancilla and Strioterebrum, in the Portuguese Pliocene (Piacenzian) at Vale de
also represented in Vale de Freixo fauna, disappeared Freixo, clearly indicates that relatively high water tem-
from the Late Pliocene. This than still least European waters during peratures (warmer today) prevailed, at of southerly migration and local extinction Pliocene sporadically, along the European Atlantic coast at this
from the Pliocene latitudebetween and The thermophilic gastropods European c. 3.1-3.2 2.7 Ma. presence of
Atlantic coast and the Mediterraneanreflects successive several thermophilic genera and species in the Portu-
climatic events the Pliocene (see Raffi & Pliocene and their cooling during guese subsequent disappearance, & Monegatti. 1993; Barnes et al., 1995; Stanley Rud- would favour climatic change as a trigger of these local
diman. 1995). extinctions and southerly migrations of marine benthic
The taxonomie of the Vale de Freixo composition gastropods oftropical affinity. In this respect, it does not
with several elements still malacofauna. thermophilic appear necessary to evoke the possibility of different
but clear indicators of condi- present, without tropical Pliocene palaeobiogeographic distributions based on
tions (sensu Raffi et al., 1989; Raffi & Monegatti. 1993) distinct palaeoecological requirements for these thermo-
such as a high number of tropical species and a high philic molluscs, thus undermining the general applica-
diversity of Terebridaeand Conidae in particular, is the bility of Dodd & Stanton's (1981) principle of taxo-
result of the first Pliocene climatic cooling event. This nomic uniformitarianism. which was suggested by
first pulse of cooling occurred in the Northern Hemi- Aguirre (1998) to interpret bioconstructions of the oys-
sphere at high and mid-latitudes relatively suddenly, at ter Saccostrea cuccullata Born. 1778. a west Afri-
about 3.2-3.1 Ma. presaging the onset of the Plio- can/Indo-Pacific thermophilic species, in the Upper
of Pleistocene ice age, but still without the buildup ma- Pliocene of Cadiz (southwest Spain, Atlantic coast). jor ice sheets (Raffi & Monegatti, 1993; Barnes et al..
1995; Stanley & Ruddiman. 1995). However, the pres-
of benthic ence at Vale de Freixo thermophilic gastro- ACKNOWLEDGEMENTS
that pods suggests relatively high water temperatures
(warmer than today) still prevailed along the European The authors wish to thank Dr Anders Waren (Swedish
Atlantic coast at this latitude between c. 3.2-3.1 and 2.7 Museum of Natural History, Stockholm) for his kind
Ma, i.e. the age assignments for the Vale de Freixo fos- advice on classification and assistance in photography.
Sr. Octavio siliferous beds. SEM micrographs were kindly prepared by
The next Pliocene climatic cooling event took place Chaveiro (Estagao Agronomica Nacional, Oeiras, Por-
at c. 2.5 Ma, and marked the formation of large ice tugal). This is Contribution 36 of the "Grupo Paleo'
of the National sheets and the transition to the modern ice age (Barnes (Palaeontology Group Natural History 64
of Lisbon This work Mollusca. — Palaeontogr. Soc. Lond., 2: Museum University). was sup- Crag Monogr.
57-64. ported by Research Project 1999SGR 00348 of the "Pla 705-856, pis
de Recerca de Catalunya' (Catalonia, Spain). Knight, J.B., L.R. Cox, A.M. Keen, R.L. Batten, E.L. Yochel-
son & R. Robertson, 1960. Systematic descriptions. In:
R.C. Moore (ed.). Treatise on Invertebrate Paleontology,
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