INVESTIGADORES
PUJOS FranÇois Roger Francis
artículos
Título:
A Miocene relative of the Ganges River dolphin from the Amazonian basin
Autor/es:
BIANUCCI, G.; LAMBERT, O.; SALAS-GISMONDI, R.; TEJADA, J.; PUJOS, F.; URBINA, M.; ANTOINE, P.-O.
Revista:
JOURNAL OF VERTEBRATE PALEONTOLOGY
Editorial:
SOC VERTEBRATE PALEONTOLOGY
Referencias:
Lugar: Lawrence; Año: 2013 vol. 33 p. 741 - 745
ISSN:
0272-4634
Resumen:
Nowadays,
only three odontocete (toothed whales) genera can be considered as
strictly freshwater dolphins: the Amazon river dolphin (Inia
geoffrensis), the possibly extinct Yangtze river dolphin (Lipotes
vexillifer) (Turvey et al., 2007), and the Ganges and Indus river
dolphin (Platanista gangetica). Even if their phylogenetic
relationships are still debated, Inia, Lipotes, and
Platanista are now recognized as belonging to different
families (Iniidae, Lipotidae, and Platanistidae, respectively), both
on the basis of morphological and molecular characters (Muizon, 1988;
Cassens et al., 2000; Hamilton et al., 2001; Nikaido et al., 2001;
MacGowen et al., 2009; Geisler et al., 2011; Geisler et al., 2012).
Considering their geographic distribution and the discovery of some
fossil relatives in marine deposits, for example the iniid
Meherrinia, the lipotid Parapontoporia, and the
platanistids Prepomatodelphis, Pomatodelphis, and Zarachis,
the current habitat of freshwater dolphins must be explained by
independent episodes of colonization of the freshwater environment
(Cassens et al., 2000; Geisler et al., 2011; Geisler et al., 2012).
Several fragmentary fossil specimens, isolated teeth or jaw
fragments, have been tentatively attributed in the past to species
presumably closely related to extant river dolphin genera (e.g., Zhou
et al., 1984; review in Muizon, 1988), but until now no diagnostic
fossil remains could provide clues about the early steps of these
colonization episodes. More specifically, the fossil record of
Platanistinae, the subfamily including the extant Platanista, is
scarce, with only one tentative record from early Miocene coastal
deposits of Oregon, north Pacific, based on an isolated mandibular
symphyseal region that is transversely compressed (Barnes, 2006).
Even if we consider this attribution as valid, a long ghost lineage
characterizes most of the history of the Platanistinae, the latter
having diverged from the extinct subfamily Pomatodelphininae since at
least the latest early Miocene (Barnes, 2002, 2006). We present here
a new fossil platanistine specimen, a periotic from the middle
Miocene of Peruvian Amazonia. This highly diagnostic ear bone partly
fills the ghost lineage mentioned above and provides insight on the
shift to freshwater environments by various odontocete clades, a
phenomenon seemingly underestimated, due to the lack of fossils from
the freshwater sedimentary record, and probably not just limited to
extant clades of freshwater odontocetes (Fordyce, 1983).