Pinnipeds - close relatives to bears

[brobear]

Some bear relatives took to the sea.
                                                       

[brobear]

what-when-how.com/marine-mammals/pinniped-evolution-marine-mammals/

I. Pinniped Ancestry: Origin and Affinities
There has long been debate about the relationship of pinnipeds to one another and to other mammals. The traditional view, also referred to as diphyly, proposes that pinnipeds originated from two carnivore lineages, an odobenid (walrus) plus otariids (fur seals and sea lions) grouping affiliated with ursids (bears) and phocids (seals) being related to mustelids (weasels. skunks, otters, and kin) (Fig. 1A). The current view supported by cladistic analysis of both morphologic and molecular data supports pinnipeds as monophyletic (having a single origin). Although the hypothesis presented here positions ursids as the closest relatives of pinnipeds, it is acknowledged that there is difficult)’ separating the various lineages of arctoid carnivores (mustelids, procyonids, and ursids) at their point of divergence (Fig. IB). Other hypotheses support pinnipeds as either allied with mustelids or as having an unresolved arctoid ancestry.

There is, however, still disagreement about relationships among pinnipeds. Most of the controversy lies in the debate as to whether odobenids are most closely related to phocids or to otariids. Most morphologic data support a link between phocids and the odobenids, whereas molecular data favor a link between odobenids and otariids.

[brobear]

palaeo.gly.bris.ac.uk/Palaeofiles/Pinnipeds/evolution.html

Evolutionary History of Pinnipeds
There are two main views of the evolution of pinnipeds. The biphyletic view, in which Walruses and eared seals evolved from a bear like ancestor and the true seals evolved from an otter-like carnivore. This view is now generally not accepted as all the evidence is largely morphological which can often be deceiving. The second view is that all of the pinnipeds belong to a monophyletic group and they all share a common ancestor. This view is the most accepted as it has been proved by extensive genetic evidence.

It is thought that after the most common ancestor of pinnipeds, the lineage split into the two superfamilies: the Otaroidea (consisting of eared seals and walruses) and the Phocoidea (the earless seals). Despite this division of the three families, it is thought that the walruses actually share a closer relationship with the phocid seals. Walruses are thought to be a very early divergence from the phocid seals, but not the first.

An animal known as Enaliarctos is thought to be the first known divergence from the last common ancestor of pinnipeds. Unlike modern pinnipeds, skeletal modification in Enaliarctos suggests that is used both its foreflippers and hindflippers in swimming. The two modern superfamilies of pinnipeds use either/or. The presence of elongate hindlimbs with extensive bony processes is an indication that this animal probably spent more of its time on land than in the ocean. The skulls of these animals also show the presence of slicing carnassials. These teeth are found in most terrestrial carnivores, but not in modern pinnipeds, which suggests Enaliarctos may have had to return to land with its prey to ingest it. Phylogenetic analyses of many Enaliarctos fossils indicated that the animal belongs in a sister group in relationship with modern pinnipeds.

Skeletons of Enaliarctos have been found from as far back as the late Oligocene which spanned from about 30 to 24 million years ago. This particular epoch marked the transition from the Palaeogene to the Neogene period which was characterized by a period of global cooling culminating in the ice ages in the Pleistocene.

Pinnipedia originally consisted of 5 families. As well as Enaliarctidae, there is another extinct family of called the Desmatophocidae. These primitive seals were closely related to the phocid seals. Whilst fossil evidence is poor, skull fossils found show that they would have relied more on sight to hunt as their inner ear was not as developed for underwater hearing as more modern pinnipeds.

[brobear]

*My big million-dollar question is: Will polar bears have flippers in the place of legs 100,000,000 years from today?

[Polar]

100 million years? Mammals might not even be living (lol), or they might be, who knows? I definitely know that bears and big cats won't exist for that long at all (we definitely won't either), and entire groupings of animals will eventually and definitely go extinct.

Now if it is 100,000 years, then it is a more realistic outcome. I don't think polar bears will adapt to the sea, they most likely will migrate south and change or they will eventually die off. It took millions-upon-millions of years for mesonychids (land-based carnivorous, canine-like mammals) to evolve to a cetacean with slight legs, and that involved a lot of mutations and species extinctions to do so. Plus, polar bears have many adaptations which are completely unlike mesonychids.

[brobear]

Yeah, well I'm just saying, should we not blow the world up or, perhaps a better way of putting it, should some micro-super-bug kill off humanity while leaving all other lifeforms intact, would the polar bear in the far future become even more aquatic?
Look carefully at the evolution of the whale. First a beach-comber with hooves, then an otter-like predator, then a sea-lion-like predator, then more seal-like, and finally a whale.

[smedz]

Apr 18, 2018 13:34:51 GMT -5 brobear said:

*My big million-dollar question is: Will polar bears have flippers in the place of legs 100,000,000 years from today?

Not impossible considering the ancestors of whales were land animals, perhaps I can draw a picture of what that could look like.

[Deleted]

May 17, 2019 23:05:17 GMT -5 smedz said:

Apr 18, 2018 13:34:51 GMT -5 brobear said:

*My big million-dollar question is: Will polar bears have flippers in the place of legs 100,000,000 years from today?

Not impossible considering the ancestors of whales were land animals, perhaps I can draw a picture of what that could look like.

You can do your drawing on this link below:


domainofthebears.proboards.com/thread/337/art-pictures-sketching-domain-members

Would love to see your drawing.

[brobear]

Go to: Prehistoric & Extinct Bears / Bear Classification / Almost a Bear - Reply #13

Puijila
(Rybczynski et al., 2009) was originally considered “a walking seal”, but here links weasels to bears and weasels to seals (but not sea lions, contra Rybczynski et al., 2009, because the Pinnipedia is diphyletic).

Remember:
(Don’t trust teeth alone because they change with diet. Always score traits for the entire skull and body whenever possible to get the closest possible relatives from a long list of candidates). 
 
*Note: Definition of diphyletic : derived from two lines of evolutionary descent. 

[brobear]

Puijila darwini

prehistoric-fauna.com/Puijila-darwini
Class: Mammalia
Order: Carnivora
Suborder: Pinnipedimorpha
Family: ?
Time period: lived during the Miocene epoch about 21 to 24 million years ago (North America)
Size: Up to 1 meters long. Weight estimated at up to 20 kg.
A typical representative: Puijila darwini

Puijila darwini is an extinct species of seal which lived during the Miocene epoch about 21 to 24 million years ago. Approximately a 1 m in length, the animal possessed only minimal physical adaptations for swimming. Unlike modern pinnipeds, it did not have flippers and its overall form was otter-like, albeit more specialized; its skull and teeth are the features that most clearly indicate that it is a seal.

It is considered to be the most primitive member of the seal family yet found. The genus name is an Inuktitut word for a young seal; the species name honours the English naturalist Charles Darwin. The one known specimen is a nearly complete fossilised skeleton. It is being housed at the Canadian Museum of Nature in Ottawa, Ontario.

Puijila darwini was a semi-aquatic carnivore which represents a morphological link in early pinniped evolution. Its fossil remains demonstrate the presence of enlarged, probably webbed feet, robust forelimbs and an unspecialized tail. This suggests that Puijila swam quadrupedally using its webbed fore and hind feet for propulsion. Phylogenetic studies including molecular evidence suggest a sister relationship between pinnipeds (seals) and ursoids (bears) as well as musteloids (weasels and otters). It had been popularly assumed that land-dwelling mammals had at some point transitioned to a more marine existence, in essence "returning to the sea" in order to gain some sort of survival advantage. However, fossil evidence of this transition had been weak or contentious. The discovery of Puijila is important as it represents a morphological link in early pinniped evolution, and one that appears to morphologically precede the more familiarly structured Enaliarctos genus, despite apparently being a younger genus. In other words, Puijila is a transitional fossil that provides information about how the seal family returned to the seas, similar to the way that Archaeopteryx illuminates the origin of modern birds. 

[brobear]

Seals have a sense of rhythm
Date: October 26, 2022

www.sciencedaily.com/releases/2022/10/221026103159.htm

Rhythm is important for human music and speech. But are we the only mammal with a sense of rhythm? Researchers show that seals can discriminate rhythm without prior training. Seals' rhythmic ability may be linked to their ability to learn vocalisations, skills that may have co-evolved in both humans and seals.