One lineage of dugongid sirenians (Metaxytherium spp.) inhabited Old World waters throughout the Miocene and Pliocene. During the Early to Late Miocene (M. krahuletzi, M. medium) and the Early and Middle Pliocene (M. subapenninum), these animals were consistently large; however, the earliest Pliocene member of this lineage, M. serresii, was distinctly smaller, as shown by the population sample from Montpellier, France. In 1987 Domning and Thomas interpreted this as ecophenotypic dwarfing and attributed it to suboptimal foraging habitat in the wake of the Messinian Salinity Crisis (MSC). This explanation implied that the reduction in body size should have first occurred near the onset of the MSC, and should have been reversed after its end, or whenever adequate seagrass resources again became available. Recent discoveries of Late (post-M. medium) Miocene M. serresii in Calabria, Italy and the attribution to the latest Miocene of the M. serresii records from As Sahabi, Libya, previously referred to the Early Pliocene, support the hypothesis of peri-Messinian dwarfing. This decrease in size is well evidenced in this study where we have analysed the pattern of body size change from the Early Miocene to the Middle Pliocene of these and other diagnostic European and Libyan fossils of Metaxytherium. We have also observed an increase in tusk size of these sirenians beginning with M. serresii that could be related to a shift to a diet richer in rhizomes due to the degradation of food resources.
Peri-Messinian Dwarfing in Mediterranean Metaxytherium (Mammalia: Sirenia): Evidence of Habitat Degradation Related to the Messinian Salinity Crisis
BIANUCCI, GIOVANNI;LANDINI, WALTER;
2008-01-01
Abstract
One lineage of dugongid sirenians (Metaxytherium spp.) inhabited Old World waters throughout the Miocene and Pliocene. During the Early to Late Miocene (M. krahuletzi, M. medium) and the Early and Middle Pliocene (M. subapenninum), these animals were consistently large; however, the earliest Pliocene member of this lineage, M. serresii, was distinctly smaller, as shown by the population sample from Montpellier, France. In 1987 Domning and Thomas interpreted this as ecophenotypic dwarfing and attributed it to suboptimal foraging habitat in the wake of the Messinian Salinity Crisis (MSC). This explanation implied that the reduction in body size should have first occurred near the onset of the MSC, and should have been reversed after its end, or whenever adequate seagrass resources again became available. Recent discoveries of Late (post-M. medium) Miocene M. serresii in Calabria, Italy and the attribution to the latest Miocene of the M. serresii records from As Sahabi, Libya, previously referred to the Early Pliocene, support the hypothesis of peri-Messinian dwarfing. This decrease in size is well evidenced in this study where we have analysed the pattern of body size change from the Early Miocene to the Middle Pliocene of these and other diagnostic European and Libyan fossils of Metaxytherium. We have also observed an increase in tusk size of these sirenians beginning with M. serresii that could be related to a shift to a diet richer in rhizomes due to the degradation of food resources.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
