Biology Reference
In-Depth Information
C
ONCLUSION
The extant
Inia
and
Pontoporia
taxa are the only living members of two families that
were more diverse during the Neogene. The fossil records for these taxa are summarized in
Figure 3, and the geographic distributions of these records are in Figure 4.
Figure 3. Map showing the distribution of the records of fossil Inioidea. 1.
Pontistes
(Late Miocene
Parana Formation) and
Ischyrorhyncus,
Saurocetes
and cf
Pontoporia
(late Miocene ―Mesopotamian‖
beds), Entre Rios Province, Argentina and Uruguay. 2.
Brachydelphis,
Pliopontos
and
Pontistes
(late
Miocene-Pliocene Bahia Inglesa Formation), Chile. 3.
Brachydelphis
and
Pliopontos
(late middle
Miocene-early Pliocene Pisco Formation), southern Peru. 4.
Ischyrorhyncus
and
Saurocetes
(late
Miocene Solimões Formation) Acre state, Brazil. 5. cf
Ischyrorhyncus
and cf
Saurocetes
(late Miocene
middle and upper levels of Urumaco Formation) Venezuela. 6.
Goniodelphis
(latest Miocene-early
Pliocene Bone Valley Formation), Florida, USA. 7.
Stenasodelphis
(early late Miocene St. Marys
Formation), Calvert County, Maryland, USA. 8.
Parapontoporia
(latest Miocene, Almejas Formation,
Cedros Island, Mexico; latest Miocene Purisima Formation and late Pliocene San Diego Formation,
California, USA); 9.
Protophocaena
(late Miocene Breda Formation and ‗Bold￩rien d'Anvers'),
Belgium and Netherlands. 10. cf
Pontistes
and Pontoporiidae indeterminate (Late Miocene Gram
Formation), Denmark. 11.
Prolipotes
(indeterminate Miocene), China.
Fossils clearly recognized as iniids are restricted to freshwater deposits of southern South
America, including areas where
Inia
do not occur today. These late Miocene fossils exhibit
morphology that suggests significant evolutionary adaptation to turbid fluviodeltaic
environments. The early Pliocene
Goniodelphis
of Florida may well be part of the iniid
lineage and the only marine one. But it seems to be an early offshoot. All other reputed
marine iniids are clearly not part of the family or even superfamily.
Pontoporiids had a wider geographic and ecologic range than the extinct iniids. The
Brachydelphinae, formerly considered as pontoporiids, are removed from this family,
elevated to the rank of family, and considered here as the sister group of the
Iniidae+Pontoporiidae clade. Over the last few years pontoporiid and brachydelphid dolphins
have been reported for the north Atlantic, including at high latitudes in the Netherlands and in
Denmark.
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