Résumé
Abstract Terrestrial gastropods occur in many North
African localities in Eocene continental deposits. Here we
analyse the faunal assemblage from the Hamada de Meridja
Formation in southwestern Algeria, dated as Early to
Middle Eocene on the basis of charophytes. The assemblage
consists of three closely related species that to date
have been classified either in the extant Madagascan genus
Leucotaenius v. Martens, 1860, or in the SW European
Eocene genera Romanella Jodot, 1957 and Vicentinia
Jodot, 1957. This is rejected for shell morphological and
phylogeographical reasons, and a new classification as
Maghrebiola gen. nov. is proposed. Maghrebiola is tentatively
placed in the South American family Strophocheilidae,
as species from the Early Eocene Itaboraf Basin of
Brazil, currently placed in the genus Eoborus Klappenbach
Handling editor: Mike Reich.
El Sid Ahmed Hammouda
sid.hammouda@gmail.com
E Dietrich Kadolsky
kadolsky @ btsgeo .com
1 Laboratoire de Recherche n° 25 «PRHPM-LECT»,
Departement des Sciences de la Terre et de l'Univers,
Universite de Tlemcen, B.P. 119, Tlemcen 13000, Algerie
2 66 Heathhurst Road, Sanderstead, Surrey CR2 OBA, UK
3 Departement des Sciences de la Terre et de I'Univers, Faculte
des Sciences de la Nature et de la Vie, Universite de Jijel,
B.P. 98, Ouled Ai'ssa, Jijel 18000, Algerie
4 Laboratoire de Paleontologie Stratigraphique et Paleoenvironnement,
FSTGAT, Universite d'Oran 2, B.P. 1524, El
Mnaouer, Oran 31000, Algerie
5 Laboratoire de Paleontologie, Institut des Sciences de
l'Evolution, C.c. 064, Universite de Montpellier 2, Place
Eugene Bataillon, 34095 Montpellier Cedex 05, France
and Olazarri, 1970 in the family Strophocheilidae, superfamily
Acavoidea, have a very similar shell habitus. This
record possibly extends the known geographical range of
the Strophocheilidae into the African continent during the
Eocene. Immigration of this stock into North Africa during
the Cretaceous via a still existing plate connection is
assumed. An attribution of Maghrebiola to the African
family Achatinidae is unlikely for shell morphological
reasons despite certain habitus similarities, although the
Priabonian genera Arabicolaria and Pacaudiella from
Oman most likely belong into this family, and not to the
Vidaliellidae as originally proposed. Possible causes for the
very low diversity of the assemblage are mainly unfavourable
living conditions, i.e. a relatively dry climate
resulting in sparse vegetation and only occasional presence
of water bodies, which may have had increased salinities,
accounting for the lack of freshwater mollusks. The
absence of any competing large gastropods may possibly
have facilitated high intraspecific variability leading to
sympatric occurrence of three closely related species, due
to the animals occupying a wide range of available ecological
niches. As the species discussed here have also been
attributed to the genera Romanella and Vicentinia in the
Vidaliellidae, we provide an appendix with annotated
characterisations of most genera of the Vidaliellidae and
list the nominal species assigned to them. This family is
tentatively placed in the South American superfamily
Orthalicoidea; its stock would have similarly immigrated
from South America, but have successfully colonized
mainly SW Europe, with only one Eocene species [Romanella
kantarensis (Jodot, 1936)] recognized in Algeria.
Keywords New taxa ■ Gastropoda * Achatinidae *
Orthalicoidea ■ Acavoidea * Vidaliellidae * Cretaceous
migration * Paleoenvironment
Kurzfassung Terrestrische Gastropoden treten in zahlreichen
Lokalitaten Nordafrikas in eozanen kontinentalen
Formationen auf. Hier analysieren wir die Faunengemeinschaft
der Unteren und Mittleren Subformation einer
Abfolge am Siidrand der Hamada de Meridja in SW-Algerien,
die aufgrund von Charophyten als friihes bis mittleres
Eozan datiert ist. Die Faunengemeinschaft besteht aus drei
eng verwandten Arten, die bisher entweder der rezenten
madegassischen Gattung Leucotaenius v. Martens, 1860,
oder den eozanen siideuropaischen Gattungen Romanella
Jodot, 1957 und Vicentinia Jodot, 1957 zugeordnet wurden.
Dies ist jedoch aufgrund der Gehausemorphologie und/oder
der Phylogeographie unwahrscheinlich, weshalb eine neue
Klassifikation als Maghrebiola gen. nov. vorgeschlagen
wird. Maghrebiola wird einstweilen der siidamerikanischen
Familie Strophocheilidae in der Uberfamilie Acavoidea
Beckens in Brasilien, die z. Zt. innerhalb der Gattung Eoborus
Klappenbach und Olazarri, 1970 in die Familie
Strophocheilidae gestellt werden, im Gehausehabitus sehr
ahnlich sind. Dieser Nachweis erweitert vorbehaltlich die
bekannte geographische Verbreitung der Strophocheilidae
bis nach NW-Afrika im Eozan. Eine Einwanderung dieser
Linie in N-Afrika wahrend der Kreide iiber eine noch vorhandene
Landverbindung der affikanischen und siidamerikanischen
Platte wird angenommen. Die Zuo