CHAPTER 2
THE NEOGENE EURO-NORTH AFRICAN
SIRENIANS
This study concerns the Neogene Euro-North African sirenians (see Appendix 2). Sirenians inhabited the Euro-North African coasts continuously for about 40 Ma, from Middle Eocene to Middle Pliocene, with 14 recognized genera and 28 species belonging to three of the four sirenian families: Protosirenidae, Trichechidae and Dugongidae (Tabb. 1 and 2). Therefore this region appears to be crucial in sirenian history, and the sirenians appear to be important to the palaeoecology of this region as aquatic macroherbivores, the main consumers of seagrasses and other aquatic plants.
The first occurrence of sirenians along the Euro-North African coasts is represented by the Protosirenidae Protosiren fraasi and Protosiren smithae, coming from the Lutetian and Bartonian respectively of Egypt, and by primitive dugongids (Gingerich et al., 1994; Domning & Gingerich, 1994; Sagne 2001; Bajpai et al., 2006).
During the Middle-Late Eocene, sirenians underwent rapid evolution and diversification along the northern and southern Tethys coasts, showing differences in locomotor and feeding adaptations. This was greatly furthered by a vacant adaptive zone, without competition and with rich food assets. Protosiren appears to have been an amphibious animal, capable of very limited terrestrial locomotion but less fully aquatic than contemporary primitive dugongids. From P. fraasi to P. smithae we see an increase in breadth of masticating surfaces, in tusk size and in rostral deflection and the separation of the nasals and exoccipitals. These trends are also observable in other sirenian lineages (Domning & Gingerich, 1994).
The early dugongids, belonging to the genera Eotheroides, Prototherium, Eosiren,
Sirenavus, Anisosiren, Halitherium and Paralitherium, seem to be fully aquatic, with
vestigial limbs (Domning, 1996, 2002a).
The Upper Oligocene – Lower Miocene sirenian record also shows high biodiversity, with about 10 genera formally recognized in the entire world (Domning, 1996). In the Euro-North African record three sirenian lines are represented during this period:
• The basal Trichechidae (Miosireninae), represented by Anomotherium
• The Dugongidae (Dugonginae), represented by the genus Rytiodus from the Aquitanian of France and the Aquitanian - Burdigalian of Libya, and maybe by “Halitherium” bellunense from the Lower Miocene of North Italy, considered by Domning (1996) a dugongine.
• The Dugongidae (Halitheriinae), represented by Halitherium christolii from the Chattian of Austria and by Metaxytherium krahuletzi from the Burdigalian of Switzerland, Austria, France and maybe other areas of the Euro-North African coasts.
From the Middle Miocene, however, the only sirenians surviving in the Euro-North African region belonged to the generalist cosmopolitan halitheriine genus
Metaxytherium, with the only exception represented by a partial mandible found in the
Middle Miocene deposits of Audon, near Tartas (Landes, SW France) and referred to
Prohalicore dubaleni by Flot (1887).
Metaxytherium is represented in this region by five species: M. krahuletzi (Burdigalian); M. petersi (Langhian to Serravallian: Badenian) (Domning, pers. comm.); M. medium
(Langhian to Tortonian); M. serresii (uppermost Tortonian to early Zanclean) and M.
subapenninum (Zanclean to Piacenzian) (Domning & Thomas, 1987; Domning &
Pervesler, 2001; Bianucci et al. in press).
Most of these Euro-North African Metaxytherium species seem to represent a single lineage characterized by very slight morphological change from M. krahuletzi to M.
medium and by dwarfing in M. serresii followed by a notable increase in body size in
the M. subapenninum (Domning & Thomas, 1987; Bianucci et al., in press). The exception is M. petersi, which apparently evolved in isolation in the Carpathian Basin during the Badenian as a short-lived and localized offshoot of the M. krahuletzi-M.
STATE SPECIES SYNONYMY (species included) REFERENCES MIDDLE EOCENE
Egypt Protosiren fraasi Abel, 1907 Abel, 1904, 1907; Gingerich, 1992
Egypt Protosiren smithae Domning and
Gingerich, 1994 Domning & Gingerich, 1994
France ?Protosiren minima (Desmarest, 1822) Hooijer, 1952
?Protosiren dubia (Cuvier)
Sickenberg, 1934 Hooijer, 1952 Egypt Eotheroides aegyptiacum (Owen,
1875) Trouessart, 1905
Eotherium aegyptiacum Owen, 1875; Masrisiren Abeli Kretzoi, 1941
Andrews, 1906; Abel, 1913; Sickenberg, 1934;
Gingerich, 1992 Egypt Eosiren abeli Sickenberg, 1934 Sickenberg, 1934 Hungary Sirenavus hungaricus Kretzoi,
1941 Kretzoi, 1941; Kordos, 1981
Hungary Anisosiren pannonica Kordos,
1979 Kordos, 1979
LATE EOCENE
Egypt ,
Libya Eosiren libyca Andrews, 1902 Gingerich, 1992 Egypt Eosiren stromeri (Sickenberg,
1934) Kordos, 1977 Kordos, 1977
Libya Libysiren sp. Heal; 1973
Italy Prototherium veronense (Zigno, 1875) Zigno, 1887
Halitherium angustifrons Zigno,
1875; Halitherium curvidens Zigno, 1875; Mesosiren Dolloi Abel, 1906;
Paraliosiren Suessi Abel, 1906
Abel, 1906; Bizzotto, 1983
Italy, Spain Prototherium intermedium Bizzotto, 1983
P. montserratense Pilleri, Biosca and
Via, 1989 Bizzotto, 2005
France Halitherium taulannanse Sagne,
2001
Freudenthal, 1970; Sagne, 2001
Hungary Paralitherium tarkanyense
Kordos, 1977 Kordos, 1977
EARLY-MIDDLE OLIGOCENE
Egypt
Eosiren imenti Domning,
Gingerich, Simons and Ankel Simons, 1994
Domning et al., 1994
France, Germany, Belgium
Halitherium schinzii (Kaup. 1838)
Kaup, 1855
Halianassa Studeri Meyer, 1838
[partim]; Halitherium schinzi
lareolensis Pilleri, 1987
Pilleri, 1987
LATE OLIGOCENE
Austria Halitherium christolii Fitzinger,
1842 Fitzinger, 1842
Germany Anomotherium langewieschei
Siegfried 1965 Siegfried, 1965
STATE SPECIES SYNONYMY (species included) REFERENCES EARLY MIOCENE
Italy “Halitherium“ bellunense Zigno,
1875
Zigno, 1875; Domning, 1996
France Rytiodus capgrandi Lartet, 1866 Thelriope capgrandi (Lartet) Pilleri,
1987 Lartet, 1866; Pilleri, 1987
Libya Rytiodus sp. Heal, 1973
Belgium and England (reworked)
Miosiren kocki Dollo, 1889 Miosiren canhami (Flower, 1874)
Sickenberg, 1934
Dollo, 1889; Sickenberg, 1934; Domning, 1996 France Metaxytherium aquitaniae Pilleri,
1987 Pilleri, 1987 Austria, France, Switzerland, maybe Libya, Slovakia, Czech Republic, Portugal, Spain, and Malta Metaxytherium krahuletzi Depéret, 1895
Halianassa Studeri Meyer, 1838
[partim]; Thalattosiren studeri (Meyer ) Thenius, 1952;
Metaxytherium argoviense Pilleri,
1987; M. beaumontii Christol in Blainville, 1844; M. meyeri Abel, 1904; M. krahuletzi excelsum Pilleri, 1987
Domning & Pervesler, 2001
MIDDLE-LATE MIOCENE
France Prohalicore dubaleni Flot, 1887 Flot, 1887 Austria,
Slovakia
Metaxytherium petersi Abel, 1904
(Domning, pers. comm.)
Thalattosiren petersi (Abel, 1904)
Sickenberg, 1928 Abel, 1904; Sickenberg, 1928; Domning, 1996 Italy, Spain, Hungary, France, Portugal, Greece, Tunisia, Libya Metaxytherium medium (Desmarest, 1822) Hooijer, 1952
Metaxytherium cuvieri Christol in
Blainville, 1844; and maybe M.
lovisati Capellini, 1886 and M. catalaunicum Pilleri, 1989
Ginsburg & Janvier, 1971; Ginsburg et al., 1979; Moncharmont Zei & Moncharmont, 1987; Pilleri, 1989; Bianucci et al., 2003
LATE MIOCENE
Libya, Italy Metaxytherium serresii (Gervais, 1847) Depéret, 1895
Domning & Thomas, 1987; Carone & Domning, 2007.
EARLY PLIOCENE
France Metaxytherium serresii (Gervais, 1847) Depéret, 1895 Gervais, 1849-1850; Depéret & Roman, 1920 EARLY-MIDDLE PLIOCENE Italy and Spain Metaxytherium subapenninum
(Bruno, 1839) Fondi & Pacini, 1974
Felsinotherium forestii Capellini,
1872; F. gervaisi Capellini, 1872; F.
gastaldi Zigno, 1878.
Capellini, 1872, Fondi & Pacini, 1974 , Canocchi, 1987
Morocco Metaxytherium subapenninum or
M. serresii
Felsinotherium cf. serresi (Ennouchi,
1954)
Ennouchi, 1954; Domning & Thomas, 1987
The study proposes to investigate the evolution of the Neogene Euro-North African sirenian species, providing a better chronostratigraphic setting and a review of the main specimens (see Appendix 2) in the light of new knowledge, clarifying the relationships among the Neogene Euro-North African sirenian species, between them and their Palaeogene relatives and the other Neogene sirenian species. This approach will also permit the development of palaeobiogeographic considerations. Moreover, this study proposes to investigate their ecology, with particular attention to their diet and habitat in correlation with the palaeogeographic and palaeoclimatic evolution of the Mediterranean Basin and of the northeastern Atlantic coasts, in order to understand their role as aquatic macroherbivores and the main consumers of seagrasses and other aquatic plants, their morphological adaptations and changes, and, in conclusion, the causes of their extinction.
