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Obscure Taxa; For interesting or obscure organisms you'd like to share.
Topic Started: Dec 14 2016, 09:46 PM (48,915 Views)
Sphenodon
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Calcareous

The La Plata dolphin (Pontoporia blainvillei), known alternatively as the franciscana (after the Franciscans, a group of Catholic monastic orders), is a small species of dolphin in the superfamily Inioidea, whose diversity encompasses the South American river dolphins. What sets the franciscana apart from its relatives is its choice of habitat - the La Plata dolphin is alone among the paraphyletic assemblage of river dolphin clades in that it inhabits saltwater, dwelling within the coastal waters from southern Brazil to central Argentina as well as the Rio de la Plata estuary. The species is believed to be basal to the freshwater members of Inioidea, representing a remnant of the intermediary stage of the group's colonization of the Amazon during the Miocene; analogous species for the other groups of river dolphins have since gone extinct.

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An adult P. blainvillei specimen.


The La Plata dolphin is one of the smaller cetacean species in the world. The greatest lengths are generally achieved by females, which can reach a maximum of 5.9 ft. (1.8 m.) as opposed to the male maximum of 5.2 ft. (1.6 m.); average mass is similarly small, at roughly 110 lbs. (50 kg.) In contrast to this, the species possesses the largest rostrum in proportion to body size of any dolphin, with the snout composing up to nearly 15% of the animal's body length. This snout is used by the dolphin to snap up small fish, crustaceans, and cephalopods, which it captures near or at the seafloor; the species bears a preference for turbid, murky waters, not entirely dissimilar in visibility to those inhabited by its riverine relations.

Franciscanas are not the most social of dolphins; specimens are typically observed alone or in small groups, though exceptionally large pods of up to 15 members have been recorded. Combined with the species' preference for turbid coastal waters and slow, smooth locomotive patterns, this makes observation of La Plata dolphins in the wild to be a challenge. As such, the majority of observations of the species come from beached specimens or those unfortunate to have been caught and drowned as bycatch.

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Skull of P. blainvillei, held by the Smithsonian Museum of Natural History's Department of Vertebrate Zoology, Division of Mammals.


Between the current lack of reliable data and live study of the species, frequent entanglement in gillnets, increased pollution of coastal waters, and disturbance of the coastline benthos upon which the species relies upon for prey by trawling, the La Plata river dolphin is currently listed as Vulnerable by the IUCN. Recognition of the franciscana's vulnerability to anthropogenic factors on part of its limited distribution has been noted by the governments of the countries whose coastline the species inhabits, and has led to the establishment in 2003 of four distinct Franciscana Management Areas throughout the species' range. These areas were determined using contemporary genetic, geographical, and demographic data, though a 2014 study indicates that a revision of the system to two areas (dividing the northern and southern populations, which exhibit a significant evolutionary divide) would be in order.

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A newborn female franciscana was discovered beached, umbilical cord still attached, on the shores of Piriápolis, Uruguay in October of 2011. The calf was rescued shortly after by representatives of SOS Rescate Fauna Marina, the head of whom can be seen bottle-feeding the young dolphin here.
Edited by Sphenodon, Jan 16 2018, 12:14 PM.

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Some of my ideas (nothing real yet, but soon):
Refugium: A last chance for collapsing ecosystems and their inhabitants.
Pansauria: A terraforming project featuring the evolution of exactly one animal - the marine iguana.
Mars Renewed: An insight into the life of Mars thirty million years after its terraforming by humankind.
Microcosm: An exceedingly small environment.
Alcyon: A planet colonized by species remodeled into new niches by genetic engineering.
Oddballs: Aberrant representatives of various biological groups compete and coexist.

..and probably some other stuff at some point (perhaps a no K-T project). Stay tuned!
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lamna
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I'd like to take a moment to talk about an animal that I'm sure almost everyone has heard of, but I still feel is obscure. Hydrodamalis gigas better known as Steller's sea cow.

Steller's sea cow is often little more than a footnote when talking about recently extinct animals, overshadowed by the Dodo, Passenger Pigeon and Thylacine. First, the one fact that's generally well known, its rapid extinction. First discovered by the famous naturalist Georg Wilhelm Steller in 1741, the species was rapidly exploited by Europeans. Within thirty years, the species had vanished from the face of the earth. That story is fairly well known, but the animal is not.
This is probably the only illustration of a sea cow based on a actual specimen, rather than a reconstitution. It's not great, but it's what we've got.
Spoiler: click to toggle


Firstly, Steller's sea cow was a species of sirenian, related to the dugong and manatee. It was however, vastly different to is cousin in appearance, ecology and range. Living sirenians are tropical animals, with the state of Georgia being about the coldest place with a population of manatees. Steller's sea cow on the other hand, lived in the ice waters of the Bering Sea.

Steller's sea cow was also big, not simply for a sirenian, but when it was alive it was one of the largest animals on the planet. Steller's sea cow could weigh up to 10 metric tons and measure 9 metres long. To give you some idea of scale, that's as big as a Minke whale. These animals weighed about the same as two average elephants.
Low quality image, but I think it shows the scale of these animals well.
Spoiler: click to toggle


Unlike most marine mammals, Steller's sea cow seem to have been buoyant, unable to dive for extended periods and spending most time floating on the surface, grazing on the canopy of kelp. It had skin that was extremly thick, and described and being bark-like in appearance, as well as a thick layer of insulating blubber.

Steller's sea cow also had several unusual physical characteristics that really set it apart from other sirenians. It totally lacked teeth, and instead fed by using a muscular upper lip covered in bristles to tear up algae and before
grinding it up with keratinous plates on the roof of its mouth and on its lower jaw. Its tongue was located towards the back of the mouth.
Note the total lack of teeth. Why do animals keep ditching teeth only to evolve some weird replacement for them?
Spoiler: click to toggle


Another bizarre adaptation, the Steller's sea cow probably did not have hands. It had large, well developed flippers, but the manus in all specimens is missing, and extinct relatives of the Steller's sea cow had reduced finger bones. More on those relatives in a moment.
Note the lack of any hand bones.
Spoiler: click to toggle


It seems that Steller's sea cow was a gregarious animal, living in large family groups. They seem to have given birth to a single calf, and to have been very protective of other members of their family, even attack boats that were hunting members of the pod.
Spoiler: click to toggle


Perhaps the reason that Steller's sea cow gets overlooked so much, is that it seems to come from nowhere, and disappear almost immediately. This likely and accident of history. You see, the Steller's sea cows we know lived in the coastal waters around the Commander Islands. They had an extremely limited range, and probably had a population less than 2,000 at the time of European discovery. Thinking of this being the extent of the animals history is a bit like thinking of Mammoths as a species from Wrangel Island.

You see, the Commander Islands were uninhabited at the time Europeans first visited them. They were the last refuge for this long linage of giant, cold water sirenians, the Hydrodamalinae. Stellar's sea cow once ranged across the North Pacific, while its cousins/ancestors the Hydrodamalis cuestae, the Cuesta sea cow and Hydrodamalis spissa, the Takikawa sea cow lived off the coasts of California and Japan respectively. As the ice ages came, Hydrodamalis evolved to be better adapted to living in cold environments.
A reconstruction of the Cuesta sea cow, note the massively reduced hands
Spoiler: click to toggle


Unfortunately, these adaptations made them uniquely vulnerable to humans. Their large size made them a valuable food source, and also mean they bred slowly. Tied to the coasts where they grazed on kelp, they were within easy striking range of humans with even the most basic of boats. Finally, their inability to dive made it impossible for them to escape. Faced with a new predator, the Stellar's sea cow was reduced to one tiny relict population around the Commander Islands. When they finally met Europeans, this last population disappeared rapidly.

For some reason these animals are rarely reconstructed in a naturalistic way, most show them as immobile specimens or being harpooned.
Spoiler: click to toggle


A sad story perhaps, but I take some comfort in it. Left alone, the Steller's sea cow survived for thousands of years. This is an animal that, by all rights, should have died out with the mammoths and the sabre-toothed cats. But it managed to cling on into the era of science, and happened to be first encountered by a scientist. I wish we could have known this fascinating animal better, but the glimpse we got into its world is much more than we typically get for most Pleistocene animals.
Edited by lamna, Jan 16 2018, 03:27 PM.
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Fósseis Vibos: Reserva Natural


34 MYH, 4 tonne dinosaur.
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Carlos
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Even less well known are the last sirenians of the Mediterranean, which were just as large, actually.
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

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Zorcuspine
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Carlos
Jan 16 2018, 12:47 PM
Even less well known are the last sirenians of the Mediterranean, which were just as large, actually.
Any chance you could do a writeup on them?
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Carlos
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Someone else did:

https://synapsida.blogspot.pt/2012/05/dugongs-of-italy.html
Lemuria:
http://s1.zetaboards.com/Conceptual_Evolution/topic/5724950/

Terra Alternativa:
http://s1.zetaboards.com/Conceptual_Evolution/forum/460637/

My Patreon:

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LittleLazyLass
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Huh, I never knew how weird and interesting steller's sea cow was. Also, you seem to have missed putting the given number in front of "metres long", leaving us just to know it's several metres long in the range of Minke whale size.
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so it was agressive?
Astarte an alt eocene world,now on long hiatus but you never know
Fanauraa; The rebirth of Aotearoa future evo set in new zealand after a mass extinction
coming soon......a world that was seeded with earth´s weridest
and who knows what is coming next...........

" I have to know what the world will be looking throw a future beyond us
I have to know what could have been if fate acted in another way
I have to know what lies on the unknown universe
I have to know that the laws of thee universe can be broken
throw The Spec I gain strength to the inner peace
the is not good of evil only nature and change,the evolution of all livings beings"
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bloom_boi
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I dont think aggressive is the right word.

I just think they didnt like, you know, let you murder it without complaint.
Edited by bloom_boi, Jan 17 2018, 12:32 PM.
"You shall perish, whatever you do! If you are taken with arms in your hands, death! If you beg for mercy, death! Whichever way you turn, right, left, back, forward, up, down, death! You are not merely outside the law, you are outside humanity. Neither age nor sex shall save you and yours. You shall die, but first you shall taste the agony of your wife, your sister, your sons and daughters, even those in the cradle! Before your eyes the wounded man shall be taken out of the ambulance and hacked with bayonets or knocked down with the butt end of a rifle. He shall be dragged living by his broken leg or bleeding arm and flung like a suffering, groaning bundle of refuse into the gutter. Death! Death! Death!"



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Rodlox
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Blue_Komrade
Jan 17 2018, 06:03 AM
I dont think aggressive is the right word.

I just think they didnt like, you know, let you murder it without complaint.
they're like dodos - when one comes under attack, it summons help...who promptly also get bashed on the skull.
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suchipithecus
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That made me realise that 'they went extinct really quickly' was all I knew about the Steller's sea cow.
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DINOCARID
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We've shared the weird derived anatines of Hawai'i before, but not all of the native waterfowl are extinct.

Posted Image
Photo taken by Jorg Hempel, on Kaua'i.

Meet the Nene, or Hawaiian Goose, Branta sandvicensis. They're considered "black geese" along with the rest of Branta, and their specific name refers to their range, as the Hawai'i islands were originally called the Sandwich islands.

As for how the otherwise laurasian black geese have a representative in the middle of the pacific, it's believed that a flock of migrating Canada geese got blown west in a storm about 500,000 years ago, and the disoriented birds found the island chain by sheer luck. With no predators and an abundance of food, they settled down, giving up their migratory ways. Without the need to escape danger or fly long distances, their wings began to shrink. Even their toe webbing began to recede with the rarity of standing water in their new home. This culminated in Branta rhuax, the giant Hawaiian goose, which weighed 19 lbs (compared to the 9 lbs of the original settlers) and was probably mostly flightless. The only other large herbivores on the islands were the bizarre moa-nalo ducks, and they never colonized big island Hawai'i where the giant goose lived, giving it free reign ecologically.

Another result of this radiation was the nene-nui, or great Hawaiian goose, which was smaller than rhuax but larger than sandvicensis. Found on Maui, and possibly a few other islands. Their wings weren't as reduced as in rhuax, but they varied, raising the possibility that this might have been a variable species that was found in both flightless and flighted forms.

Only the nene survived the polynesian settlers and their rats, pigs, dogs, and chickens. The moa-nalo and mole ducks also died out in this invasion, as specialized island-dwellers often do when humans come across them. It wasn't simple luck though; being able, though infrequent, fliers meant that nene could escape the worst of the foreign predators. But things went downhill when the British arrived. Numbering roughly 25,000 when James Cook arrived, the new wave of invasive species and hunting brought their numbers down to a desperate 30 by 1952. Conservation programs were able to save the luckily easy-to-breed nene, and they now number 2,500 total worldwide. Still a fraction of their former numbers, but one of humanity's few successes with what was seemingly a doomed species.

Once found on every island but O'ahu, the nene is now found only on Hawai'i, Maui, Moloka'i, and Kaua'i, grazing and browsing plains, dunes, lava fields, scrub, and even agricultural fields and golf courses.

They're probably my favorite example of evolution in action, seeing as how their ancestor still exists for comparison, better illustrating their adaptations.
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LittleLazyLass
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...I had no idea the nene was extant. For some reason I was under the impression it was extinct.
totally not British, b-baka!
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I don't even really like this song that much but the title is pretty relatable sometimes, I guess.
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Archeoraptor
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"A living paradox"
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unless there is very similar species I have seen yhis in person in zoos or at least they are too familiar
Astarte an alt eocene world,now on long hiatus but you never know
Fanauraa; The rebirth of Aotearoa future evo set in new zealand after a mass extinction
coming soon......a world that was seeded with earth´s weridest
and who knows what is coming next...........

" I have to know what the world will be looking throw a future beyond us
I have to know what could have been if fate acted in another way
I have to know what lies on the unknown universe
I have to know that the laws of thee universe can be broken
throw The Spec I gain strength to the inner peace
the is not good of evil only nature and change,the evolution of all livings beings"
"
Spoiler: click to toggle
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Rodlox
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Archeoraptor
Jan 22 2018, 03:24 AM
unless there is very similar species I have seen yhis in person in zoos or at least they are too familiar
deja vu, here we go again
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The Sputnik Virophage is a virus which infects the giant virus known as Mamavirus, which in turn infects the protist Acanthamoeba, which in turn sometimes infects animals. Another type of virophage is found in a lake in Antarctica, where it parasitizes other viruses that infect algae.

Truly "big fleas have little fleas..."
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