The Prehistoric Bear Thread- Anything Ursidae related

Adam Khor

Agriotherium africanum, a prehistoric giant bear, seemingly had the most powerful bite of any carnivoran known, according to a new study- much stronger than any big cat or any bear living today.
Scientists believe that this bear (one of the few African members of the family) was a pure meat-eater, unlike living bears.
It could weigh up to 700 kgs, maybe more, being among the largest kinds of bears.



http://www.bbc.co.uk/nature/15559929

Adam Khor

For some reason this just got to the headlines despite the discovery having been made last year.

http://paleorama.wordpress.com/2012/01/19/video-inah-halla-restos-de-osos-de-hace-12-mil-anos-en-cenote-proximos-a-craneos-humanos/

Basically, four skulls (and some jaws and long bones) belonging to giant short-faced bears were found in a cenote (underwater caves considered sacred by the Maya, and often studied by archaeologists as the Maya would throw in human sacrifices to Chaac, the god of rain).

At first, they thought the skulls had belonged to jaguars, but they were too large and when examined, they were found to be bear skulls- a surprise, as bears are no longer found in the area (the only bear that still lives in Mexico is the American black bear and lives in the central and northern states only).
Eventually the skulls were identified as belonging to Arctotherium, the so called South American Short Faced Bear- recently made relatively famous thanks to some truly colossal remains found in Argentina.
Two paleontologists, however, believe that the remains may actually belong to Arctodus (fossils of which have been found in other parts of Mexico).

Human remains were also found in the cenote, close to the bears, and since they lack the skull deformations seen in most Maya skeletons, scientists believe they may be from an earlier time- probably the same as the giant bears.
The cenote was a dry cave 11.000 years ago, and was either used as a den by the bears (some of which were very young when they died) or else the animals fell there by accident.

Rubecula

Not really expected to be found that far south I suppose, but as I think about it. Didn't the predators start to overlap each other after the continents collided?

I think big cats came north and I see no reason why the bear couldn't head south.

As i said not expected, but understandable.

Good find though Adam, I never knew about this item.

Galvasean

Rubecula wrote: »

Not really expected to be found that far south I suppose, but as I think about it. Didn't the predators start to overlap each other after the continents collided?

I think big cats came north and I see no reason why the bear couldn't head south.

There was a lot of species interchange when the continents overlapped. The big cats expanded their range from north to south, Smilodon would be a popular example. While the interchange is more well known for creatures moving south a few types including giant ground sloths and some terror birds did venture northward.

Adam Khor

Galvasean wrote: »

The big cats expanded their range from north to south, Smilodon would be a popular example.

No, Smilodon is a populator example

Galvasean

^^ Oooooh, it would appear a lurker also appreciated that pun. :pac:

Allosaur

Still going on.
Fire Ants.
Armadillos.....

Adam Khor

They seem to be much older than believed.

http://the-scientist.com/2012/07/23/the-polar-bears-prehistoric-past/

Rubecula

I find that very interesting, and it also mentions genomes in humans at the end too.

I always thought that polar bears were a fairly recent species as an offshoot of brown bears, I certainly didn't think that as a species they were so much older than us.

Climate change could give us more Pizzlies eh? That could be interesting. (Pizzlies are crosses between Grizzlies and Polar bears with Grizzlies being the Brown bears.)

Adam Khor

Yes, and some scientists say the ancestors of polar bears probably looked quite a bit like pizzlies/grolars.

Adam Khor

The bear skull belongs to the species Ursus dolinensis and was found at Atapuerca. According to the article it lived one million years ago, was closely related to cave and brown bears, and used the caves to hibernate- its claw marks have been found there as well.

http://www.noticiasciencias.com/2012/07/un-craneo-completo-de-oso-de-casi-un.html#.UBWHTaTIQ5o.twitter

Galvasean

The link in the OP appears to be down now. Here's another link to the story for anyone who missed it:
http://www.thespec.com/news/world/article/766567--polar-bears-likely-way-older-than-previously-thought

Adam Khor

This is about Indarctos arctoides. Indarctos atticus was once estimated to weigh up to 3 tons...

http://phys.org/news/2013-09-ancient-european-unusually-large-penis.html

Rubecula

Looks to be a bit of a clever dick.



Sorry, I'll get me coat.

Adam Khor

Not precisely paleontology but interesting:
http://phys.org/news/2013-10-mythical-yeti-descended-ancient-polar.html#jCp

Wibbs

Very interesting.

Adam Khor

Didn´t they admit recently that they had done new genetic studies and it turned out the "official", accepted theory on polar bear origins was flawed, and once again they had no idea where polar bears came from?

Well I was thinking... what if polar bear ancestors actually lived in the Himalayas, and only later spread north, and became semi-aquatic and all that stuff?
I mean, it wouldn´t be the first case of that happening- I remember posting here about the discovery of a new, older species of Coelodonta, suggesting that woolly rhinos appeared in Tibet and only later spread to the rest of the continent...

Adam Khor

http://www.sciencemag.org/news/2016/03/ancient-otter-bear-may-have-popped-clams-rocks-bottle-opener?utm_source=newsfromscience&utm_medium=facebook-text&utm_campaign=otteropener-2679

Adam Khor

http://news.discovery.com/animals/giant-prehistoric-bears-evolved-to-fill-scavenger-gap-160421.htm

What does everyone think?

I don t doubt this was the most frequent MO for these bears but this part:

"At the time the giant bears lived there would have been lots of large herbivores (and) specialized predators like wolves, lions and sabre-tooth cats, but there would have been no specialized scavengers"

sounds like nonsense to me. What about all those vultures, condors and teratorns that are often and copiously found along with the remains of larger animals from those times? It takes minutes for a small flock of vultures to skeletonize a carcass, and only 10 of them are enough to intimidate a cheetah away from its kill. And some of these prehistoric vultures were the size of pterosaurs. I think they deserved a mention at the very least.

Capt'n Midnight

Adam Khor wrote: »

sounds like nonsense to me. What about all those vultures, condors and teratorns that are often and copiously found along with the remains of larger animals from those times? It takes minutes for a small flock of vultures to skeletonize a carcass, and only 10 of them are enough to intimidate a cheetah away from its kill. And some of these prehistoric vultures were the size of pterosaurs. I think they deserved a mention at the very least.

+1

Especially since most of the vultures from a large area could arrive very quickly.

Adam Khor

Study suggests it was about as vegetarian as today's giant panda.

http://www.sci-news.com/paleontology/dietary-habits-cave-bear-ursus-spelaeus-04129.html

Adam Khor

https://phys.org/news/2018-01-finny-polar.html

Adam Khor

Cave bear taxonomy is a mess apparently, with U. spelaeus no longer considered the only species. 
http://fi.nm.cz/wp-content/uploads/2017/12/03_Spassov_et-al_2017.pdf

Adam Khor

https://www.bbc.com/news/science-environment-44699233



Sadly no mention made of the fabled Ursus tyrannus (Ursus maritimus? tyrannus?) found in London, whose remains were once said to belong to an extremely large, early polar bear.

Adam Khor

https://eurekalert.org/pub_releases/2018-06/cp-2pf061118.php

Adam Khor

Apparently both species interbred.

https://www.nationalgeographic.com/science/2018/08/cave-bears-ancient-dna-paleogenomics-extinction/?cmpid=org=ngp::mc=social::src=facebook::cmp=editorial::add=fb20180827science-cavebeardna::rid=&sf196321303=1

Adam Khor

This is not a new species, but rather a specimen of the already known Arctotherium angustidens, possibly the largest bear ever to have existed . The article is in Spanish:

http://3.bp.blogspot.com/-8Y8SOK8H57U/VKGwHyLU9RI/AAAAAAAAA5U/z1eqW_8x-UA/s1600/1.jpg

Dr. Leopoldo Soibelzon, researcher for the Museo de la Plata and CONICET, both Argentinian entities, commented that "it is a large bear of the species Arctotherium angustidens, of which the largest individuals could reach up to 4.5 m in a rearing position.

It was Soibelzon who presented the largest specimen known in 2011. Meanwhile, this new specimen, found in the San Pedro region, was identified as a young male who weighed about 800 kg at the time of his death and would've been 2.5 m rearing on its hind legs.

The giant bear expert noted that "the skull and mandible of this new San Pedro specimen are incredibly well preserved, and part of the pelvis, part of a humerus and radius, and six articulated vertebrae"


(...)

The beast's skull is really amazing regarding size and preservation state. It has fangs about 6 cm long, which are strong, sturdy and pointed and well designed to rend the flesh of its prey.

The lower jaw has 4.5 cm fangs, and the bear's molars too were well prepared to cut and crush the flesh and bone of its victim.

The largest Arctotherium angustidens would reach a size larger than the 2011 estimate, when Dr. Soibelzon announced the largest specimen. (...) had a strong tendency to feed on flesh and bone of animals they could hunt themselves, but also stole from other carnivores such as the sabertooth tiger.

Spores and grains of pollen from certain plants, fungi and algae have been found in the same sediments, which allows us to know that this giant bear lived in a steppe-like environment, with grassy vegetation, sand-like substrate, and always near water sources"


Dr. Soibelzon noted that these bears lived in the Pampas region until about 500.000 years ago. Meanwhile, bears as a whole arrived to South America about 3 million years ago when the Panama isthmus was elevated allowing land animals to arrive from North America"

Humerus of an Arctotherium angustidens compared to that of its closest living relative (the spectacled bear, far left), and the American black bear:



Dr. Leopoldo Solbeizon holds the Arctotherium's humerus to compare it to that of an elephant:

Adam Khor

The study is in Russian. It describes new Ursus arctos fossils from the Pleistocene, specifically the Karginian interstadial (32.000-25.000 years ago). The remains are described as "exceptionally large", being larger than any modern day brown bears in Eurasia.

https://journals.eco-vector.com/0869-5652/article/view/14506/11040

The connection with forest habitats explains why U. arctos Pleistocene finds are rare in the north of Eastern Siberia, since open tundro-steppe and steppe landscapes dominated here.

U. arctos Pleistocene remains are found on the territory of Yakutia since the beginning of the middle Pleistocene. It was assumed that at this time there existed a large bear close to U. a. kamiensis- at the end of the middle and beginning of the late Pleistocene the smaller U. a. priscus*, and at the end of the Pleistocene the latter was replaced by a small bear, U. arctos spp, similar in size to the modern Yakut brown bear.

In 2015–2016 in the north of Yakutia, new fossils of several specimens of exceptionally large brown bear have been found, which are described in this article.

All described finds belong to adult individuals, probably males. Their mineralization is insignificant and is characteristic of bone remains from the frost-holes of Yakutia during the Karginsky-Sartan period. The surface color of bones varies from yellowish light brown to dark brown. The mandibular branch of MM 1661 is more strongly mineralized, its color is dark brown, in places it is almost black, which is typical for bones of an earlier time, middle-beginning of the late Pleistocene.

The remains originate from the Upper Pleistocene sediments and are found together with the remains of typical mammals of the mammoth fauna, the woolly mammoth Mammuthus primigenius (Blum.), steppe bison Bison priscus (Boj.) and cave lion Panthera spelaea.

The brown bear fossils in many ways exceed the size of modern U. arctos from Yakutia. Among the new finds are CM1 and AN8004, the sizes of which are exceptionally large- the majority of their measurements are far superior to those of not only modern brown bears from Yakutia but also to the maximum sizes of the largest Eurasian subspecies, U. a. beringianus and U. a. piscator.

U. arctos can reach extremely large sizes in the presence of a rich forage base. The modern Yakutia brown bear lives in harsh climactic conditions, and its diet is rather poor. It eats less animal food and low-calorie vegetable matter prevails in its diet. Under unfavorable conditions, an ecomorph of smaller bears came to be, characterized by an adaptive feature- a long winter sleep which lasts for 6.5 to 7.5 months.

It is difficult to explain the reasons for gigantism in the fossil brown bear of northern Yakutia. Probably it was due to the peculiarities of the Karginian warm period, which saw an increase in the diversity of vegetation, and accordingly, of edible plants. In addition, at this time (the bears would've had access to) the carcasses of large animals- like mammoths and woolly rhinos- and would've hunted their young.

In modern day U. arctos the tendency towards predation increases during periods of lack of vegetable food. The corpses of adult mammoths, which could weigh up to 4.000-5.000 kg, would provide a brown bear with high protein feed for a long time, since for example, a modern bear that feeds on a moose weighing up to 400-500 kg will take between 7 and 10 days to consume it fully.

The consumption of mammoth meat has been indicated by isotope analysis data from eastern Beringia. This increase in available food apparently caused the increase of size in the Karginian brown bears from Yakutia.

*Ursus arctos priscus is known to have been both gigantic (probably up to 1.000 kg, that is comparable to the largest cave bears and to Arctodus simus from North America), and highly carnivorous. Image below unrelated to the article.

Adam Khor

Humans, not climate change, doomed the cave bear.

https://www.nationalgeographic.com/science/2019/08/humans-not-glaciers-wiped-out-ice-age-cave-bears-ancient-dna-shows/

“If not for our arrival in Europe, I don’t see any reason why cave bears should not be around today,” says study coauthor Hervé Bocherens, a paleobiologist at the University of Tübingen in Germany who has studied cave bear remains for 30 years.

When the scientists ran their analysis, the data suggested that the cave bear decline started some 40,000 years ago—long before the last ice age set in. This also means that cave bears thrived throughout a number of earlier periods when temperatures significantly decreased. Instead, their downward trend starts right about the same time that our species began to spread across Europe.

“There is some evidence suggesting some modern humans may have set foot in Europe even earlier,” Bocherens says. “But as far as we know, they only really populated the continent around the time the cave bears start declining.”

Adam Khor

New study contradicts the above. Trade-off between glacial climate adaptations and dietary niche versatility may have eventually doomed the cave bear:

https://advances.sciencemag.org/content/6/14/eaay9462

The cave bear is one of the best known extinct large mammals that inhabited Europe during the “Ice Age,” becoming extinct ≈24,000 years ago along with other members of the Pleistocene megafauna. Long-standing hypotheses speculate that many cave bears died during their long hibernation periods, which were necessary to overcome the severe and prolonged winters of the Last Glacial. Here, we investigate how long hibernation periods in cave bears would have directly affected their feeding biomechanics using CT-based biomechanical simulations of skulls of cave and extant bears. Our results demonstrate that although large paranasal sinuses were necessary for, and consistent with, long hibernation periods, trade-offs in sinus-associated cranial biomechanical traits restricted cave bears to feed exclusively on low energetic vegetal resources during the predormancy period. This biomechanical trade-off constitutes a new key factor to mechanistically explain the demise of this dominant Pleistocene megafaunal species as a direct consequence of climate cooling.

Adam Khor

Another amazing discovery from Yakutia, Siberia! This time a practically complete, frozen bear carcass!

Two bears have actually been found, one adult and one cub, but apparently in different locations. They have been announced as being possibly cave bears (Ursus spelaeus), which would make them the very first specimens of the species with soft tissue preserved, and would contribute enormously to our understanding of this extinct animal. Alternatively, one or both could actually be Pleistocene brown bear.

https://siberiantimes.com/other/othe...arctic-island/


https://siberiantimes.com/other/others/news/first-ever-preserved-grown-up-cave-bear-even-its-nose-is-intact-unearthed-on-the-arctic-island/

Adam Khor

Toe bone found in California's Channel Islands belonged to short-faced bear (Arctodus simus). As no other remains of this predator have been found at the island- once home to pygmy mammoths and giant mice-, the study theorizes the bone was carried to the island by a scavenging bird. Alternatively, the bone could be the first evidence of a previously unknown island population of these bears.

Also, a chemical analysis of the bone suggests the bear was hunting pinnipeds (seals, sea lions) in a coastal environment, something never before suggested for this particular species.

https://scitechdaily.com/fearsome-2000-pound-beast-solving-the-mystery-of-a-13000-year-old-bone-discovered-on-the-california-channel-islands/

The idea of coastal marine mammal predation by short-faced bears had at least been suggested before though it seems, as there exists a picture of a smaller South American short faced bear (Arctotherium) attacking a pinniped.

Adam Khor

A Miocene ursine bear from North America, Aurorarctos, and the origins of herbivory-dominated omnivory in bears:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303987/

Adam Khor

360.000 year old DNA recovered from cave bear fossil bones:

https://www.cell.com/current-biology/fulltext/S0960-9822(21)00138-X?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS096098222100138X%3Fshowall%3Dtrue