The Dolphin Tree of Life and the Smithsonian Panama Link

Ocean Dolphins at Surface Level Navigation -Image Wallpaper

The complete Dolphin Evolutionary Tree of Life begins to come together with the unearthing of the newly discovered Smithsonian Panamanian Missing Link dated 6 million years ago. Smithsonian Scientist assure that the fossil despite living in ocean environments is the closest relative to River Dolphins. The implications of this discovery are deep and wide. Why would a salted ocean dolphin have evolved to resemble a river dolphin when these subspecies are widely different.

Dolphins worldwide, in the ocean and in river waters are threatened, some species have even reached extinction levels, the Dolphin Tree of Life is a tool which could serve in raising awareness and understanding. 

Dolphin historical evolution is widespread throughout all oceans and far dates back in time. Dolphins have been on the move and adapting from the most singular shapes to reach current molds today. 

Some dolphins in this evolutionary road took a one-way-no-return ticket evolving from the ocean to river ways passing through deltas and estuaries to finally reach their final form after years of passing genes down through the genetic flow channels. But fossil records and living species of dolphin today reveal that there is a gap of evolution species which existed and where the links and branches of the Evolution Tree. The road of Ocean Dolphins to River Dolphin holds one of these gaps.

Earth Touch News assured that the Ancient River Dolphin Fossil discovered by Smithsonian scientists could finally explain where did River Dolphins come from.

The Smithsonian News Desk communicated on September 1 that the unearthed River Dolphin fossil is part of a new genus and specie which has long been extinct was discovered. Smithsonian scientists and colleagues made the discovery after carefully examining fossil fragments from Panama. The dates provided by the fossil reveal that the specie lived in a time when South and North America were still divided by the Caribbean Seas and not united. The rising of Central America and the Panama Isthmus came in later geological eras.

The Fossil was discovered in the Caribbean coast near the town of Piña Panama -location which 6 million years ago was a plankton hotspot and ideal rich ocean energy location for dolphins. Testing dated the specie to range back in time at least 5.8 to as much as 6.1 million years ago. 

The fossil fragments also shed new light on the evolution of today’s freshwater river dolphin species. The conclusions of the works, excavation, testing and analysis were published in full by Scientific Journal Peerj. 

“When in their evolutionary tract did River Dolphins transition from the saltwater of the ocean to the freshwater of rivers?” Smithsonian Scientists asked. 

The fossil which the team discovered could be a key link in the chain of evolution, the very branching out of the superb Dolphin Tree of Life. 

“It consists of half a skull, lower jaw with an almost entire set of conical teeth, right shoulder blade and two small bones from the dolphin’s flipper. In comparison with other river dolphins—both fossil and living—the shape and size of these parts suggests that the full specimen may have been more than 9 feet long,” Scientists revealed.

The article at Peerj Titled: “Isthmia panamensis, a new fossil inioid (Mammalia, Cetacea) from the Chagres Formation of Panama and the evolution of ‘river dolphins’ in the Americas” addresses in detail the discovery. 

“In contrast to dominant mode of ecological transition in the evolution of marine mammals, different lineages of toothed whales (Odontoceti) have repeatedly invaded freshwater ecosystems during the Cenozoic era. The so-called ‘river dolphins’ are now recognized as independent lineages that converged on similar morphological specializations. In South America, the two endemic ‘river dolphin’ lineages form a clade (Inioidea), with closely related fossil inioids from marine rock units in the South Pacific and North Atlantic oceans. Here we describe a new genus and species of fossil inioid, Isthminia panamensis, from the late Miocene of Panama,” the paper breaks it open.  

Smithsonian scientists concluded that the specie discovered was mainly a marine inhabitant -a creature of the oceans, not very different from existing ocean dolphins. 

“We propose that a marine ancestor of Inia invaded Amazonia during late Miocene eustatic sea-level highs,” researchers concluded. 

The Dolphin Tree of Life (Ocean-River Branch) is not simple and branches out to other continents. Living River Dolphin species spread throughout the world. From India to China, Vietnam and other locations in Asia to South America Amazonas Basin the Dolphin Tree of Life is complex when it comes in close contact with earth-waterways and rivers. 

Evolution from Ocean to River is matter of study world wide. NOAA Fisheries assures that the Baji Chinese River Dolphin originates from “after the subsequent sea-level lowering and transition to a freshwater river during the late Neogene period.” In India the Ganges River Dolphin was linked by a study of the University of Otago to a distant cousin of an ancient New Zealand dolphin specie. 

In South America Brazil the Amazon river dolphin goes by the name Boto. Like all river dolphins it has adapted its mouth and entire body to make the most of the river environment. River Dolphins rely more on acoustic sightings and mapping due to high turbidity of river waters making their adaptation unique among cetaceans. River Dolphins are present in three sub-species in the Amazonia River System countries of Brazil, Peru and Ecuador as well as those within the Orinoco Basin in Venezuela and Colombia as well as some registered in Bolivian water ways. 

Discovery Channel covering the finding of the Smithsonian Panama Fossil assured that despite dwelling in the salty waters of the Caribbean Sea the specie is actually more closely related to modern-day freshwater river dolphins. 

In fact, "Isthminia is actually the closest relative of the living Amazon river dolphin," study co-author Aaron O'Dea, a staff scientist at the Smithsonian Tropical Research Institute in Panama, said in a statement. 

“Many other iconic freshwater species in the Amazon, such as manatees, turtles and stingrays have marine ancestors, but until now, the fossil record of river dolphins in this basin has not revealed much about their marine ancestry. Isthminia now gives us a clear boundary in geologic time for understanding when this lineage invaded Amazonia,” lead author of the study Nicholas D. Pyenson said. Pyenson is also the Curator of Fossil Marine Mammals at the Smithsonian’s National Museum of Natural History. 

“While whales and dolphins long ago evolved from terrestrial ancestors to fully marine mammals, river dolphins represent a reverse movement by returning inland to freshwater ecosystems. As such, fossil specimens may tell stories not just of the evolution these aquatic animals, but also of the changing geographies and ecosystems of the past,” Aaron O’Dea, staff scientist at the Smithsonian Tropical Research Institute in Panama and co-author of the paper ended it.