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*Please check the larger image. Also, poll is added.

Battle Beyond Epochs : The wondrous world of short-faced bears! (Ailuropodine and Tremarctine Giant Bears)

●Scene●

A lakeshore scenery in south central Great Plains, the area what's now Oklahoma, North America, during the Latest Miocene. An experienced male Huracan coffeyi  that had killed a Teleoceras (medium sized short limbed rhinoceros) a little while ago, immediately became aware of a threatening presence that emerged in the distance (distance I mean, not ordinary distant place but the place from the different epoch!). The giant ailuropodoine bear braced himself to protect the prey against its Ice Age counterpart of equal might...!

In this new episode of Battle Beyond Epochs, I feature a transcendental encounter beyond time and space, between Huracan coffeyi (The Mio-Pliocene) and Arctodus simus (The Pleistocene), the two representative 'giant short faced bear phenotypes' of Ailuropodinae and Tremarctinae, and also add a modern Panda and a Spectacled bear to compare characteristics and sizes of these major taxa of the two subfamilies.

●Species●

（Right）

Huracan coffeyi

Teleoceras spp.

In a small square frame

Ailuropoda melanoleuca

（Left）

Arctodus simus

In a small square frame

Tremarctos ornatus

●Description●

<Huracan, a new taxon of Ailuropodinae>

The only surviving member of the subfamily Ailuropodinae (panda relatives) is a herbivorous giant panda (Ailuropoda melanoleuca) whose diet consists almost exclusively of bamboo, but in the past, there existed multiple taxa ranging from hyper-carnivorous to omnivorous, gigantic to medium.

The genus Indarctos, a large omnivorous bear widely distributed in Eurasia and North America during the Miocene, was one such taxon.

Recently, it has been found that Indarctos and some North American specimens of the genus Agriotherium share synapomorphies and later, some Chinese Agriotherium were also found to have similar characteristics (Jiangzuo and Flynn, 2019).

These particular specimens with combining characteristics of Indarctos and Agriotherium that had previously been classified in the genus Agriotherium, are now being re-classified into a newly proposed genus Huracan (Jiangzuo et al., 2023).

It was also found that Indarctos, Huracan and Agriotherium all share morphological traits unique to Ailuropodinae.

Based on these findings, all three of them are now placed within Ailuropodinae, under the tribe Agriotherinii, as opposed to the tribe Ailuropodinii which includes the extant panda and its close relatives (see below).

Agriotherinii

(Indarctos, Agriotherium, Huracan)

  ／

♦Ailuropodinae

  ＼ Ailuropodinii

(Kretzoiarctos, Agriarctos, Ailurarctos, Ailuropoda(modern Panda))

Huracan and Agriotherium are believed to have diverged from some local populations of Indarctos, and the divergence seems to have taken place in East Asia during the Late Miocene, judging from fossil records. Although Huracan's morphologies were intermediate or transitional, Agriotherium's earliest fossil records are older and the distribution of the two overlapped in some areas, so Huracan was not ancestral to Agriotherium, but its closest sister taxon.

<Morphology of Huracan & Agriotherium>

Huracan and Agriotherium were relatively short snouted (while Agriotherium had a shorter muzzle), with teeth well adapted for both slicing and bone crushing, specialized for hyper-carnivorous diet.

They both had long limbs and exhibit a higher degree of cursorial adaptations than in Indarctos. The decline of Indarctos and the rise of Huracan and Agriotherium during the Miocene-Pliocene boundary coincided with global expansions of open environments due to periodic cooling and drying events, indicating that species better adapted to running became advantageous.

Morphometric analysis of distal and proximal forelimb proportions suggests that Huracan and Agriotherium were probably the second most cursorial taxa in Ursidae, after Hemicyonine 'dog-bears' (Hemicyonines were digitigrade as opposed to plantigrade Agriotherines). On the other hand, due to the forelimb features such as the small ratio of the long bone length to peripheral width (smaller this ratio, lankier the limbs) and the weaker humeral epicondyle, forelimb grappling capability in Huracan and Agriotherium was inferior to that of ursine bears and tremarctine Arctodus (Jiangzuo et al., 2023).

The skull of Huracan coffeyi (the largest species) is estimated to have reached condylobasal length of 383–515 mm and total skull length of 411–553 mm (although no complete crania has been found), making its craniodental dimension one of the largest among Ursidae, alongside Arctotherium angustidens and Ursus ingressus.

However, Huracan was proportionally large headed, as the postcranial dimension of Huracan coffeyi was only slightly larger than that of Agriotherium africanum, smaller than Indarctos oregonensis and distinctly smaller than Arctodus simus (Jiangzuo et al., 2023).

＜"Giant Short Faced Bear Phenotypes"＞

Sorkin (2006) once categorized Agriotherium africanum and Arctodus simus together as 'giant short-faced bear morphotypes' (obviously not as taxonomically but phenotypically). Following this manner, we can perhaps categorize Huracan and Agriotherium as 'Ailuropodine giant short-faced bears', while Arctodus and Arctotherium as 'Tremarctine giant short-faced bears'.

In North America, after the extinction of Huracan and Agriotherium during the Pliocene, it may be argued that tremarctine giant short faced bears independently acquired 'similar' ecomorphs to fill the previously occupied niche (although we must also note that tremarctine giant short faced bears were omnivorous and the degree of limb adaptations to running were not as good compared to Agriotherines (Jiangzuo et al., 2023)). The paleoecological and paleoenvironmental factors that led to this convergence, as well as the fact that 'the giant short-faced bear phenotype' has not occurred in the Old World since the extinction of Agriotherine bears must be interesting subjects for discussion.

＜Titanic Match-up : Comparison＞

Hypothetical mighty clash between Huracan coffeyi and Arctodus simus.

Although Jiangzuo et al. (2023) do not provide weight estimates for Huracan coffeyi, its size is described as intermediate between Agriotherium africanum and Arctodus simus. The scientific body mass estimates of A. africanum and A. simus are 317~540 kg (Sorkin, 2008, Oldfield et al., 2012) and 770 kg (Christiansen & Harris, 1999, based on six specimens. Figueirido, 2011 reported several A. simus specimens that may have exceeded 900kg), respectively.

Being 'slightly larger than the former and distinctly smaller than the latter', let's assume that the size of H. coffeyi could be about 450 to 650kg (this is only a guesstimate), for the sake of convenience.

●Huracan’s advantages = larger skull and superior bite force, agility(better cursoriality), probably better killing techniques

●Arctodus' advantages = overall larger size and superior strength(specifically, grappling)

You can vote for the one you believe could be more dominant, from here↓
www.deviantart.com/jagroar/pol…

Thank you in advance for your votes!

Also, next up, the full version of the mid-Pleistocene Steppe Cave lion vs. Homotherium vs. Giant Mid-Pleistocene Brown bear will be up soon, sorry for this delay!

Please stay tuned and look forward to that mega interspecific clash, thank you.

Image and text by ©Jagroar (All rights reserved)

●References●

(Jiangzuo et al., 'New Fossil Giant Panda Relatives (Ailuropodinae, Ursidae): A Basal Lineage of Gigantic Mio-Pliocene Cursorial Carnivores', 2023)

(Abella et al., 'Paleodiversity of the superfamily Ursoidea (Carnivora, Mammalia) in the Spanish Neogene, related to environmental changes', 2014)

(Sorkin, 'Ecomorphology of the giant short-faced bears Agriotherium and Arctodus' , 2006)

Description

*Please check the larger image. Also, poll is added.

Battle Beyond Epochs : The wondrous world of short-faced bears! (Ailuropodine and Tremarctine Giant Bears)

●Scene●

A lakeshore scenery in south central Great Plains, the area what's now Oklahoma, North America, during the Latest Miocene. An experienced male Huracan coffeyi  that had killed a Teleoceras (medium sized short limbed rhinoceros) a little while ago, immediately became aware of a threatening presence that emerged in the distance (distance I mean, not ordinary distant place but the place from the different epoch!). The giant ailuropodoine bear braced himself to protect the prey against its Ice Age counterpart of equal might...!

In this new episode of Battle Beyond Epochs, I feature a transcendental encounter beyond time and space, between Huracan coffeyi (The Mio-Pliocene) and Arctodus simus (The Pleistocene), the two representative 'giant short faced bear phenotypes' of Ailuropodinae and Tremarctinae, and also add a modern Panda and a Spectacled bear to compare characteristics and sizes of these major taxa of the two subfamilies.

●Species●

（Right）

Huracan coffeyi

Teleoceras spp.

In a small square frame

Ailuropoda melanoleuca

（Left）

Arctodus simus

In a small square frame

Tremarctos ornatus

●Description●

<Huracan, a new taxon of Ailuropodinae>

The only surviving member of the subfamily Ailuropodinae (panda relatives) is a herbivorous giant panda (Ailuropoda melanoleuca) whose diet consists almost exclusively of bamboo, but in the past, there existed multiple taxa ranging from hyper-carnivorous to omnivorous, gigantic to medium.

The genus Indarctos, a large omnivorous bear widely distributed in Eurasia and North America during the Miocene, was one such taxon.

Recently, it has been found that Indarctos and some North American specimens of the genus Agriotherium share synapomorphies and later, some Chinese Agriotherium were also found to have similar characteristics (Jiangzuo and Flynn, 2019).

These particular specimens with combining characteristics of Indarctos and Agriotherium that had previously been classified in the genus Agriotherium, are now being re-classified into a newly proposed genus Huracan (Jiangzuo et al., 2023).

It was also found that Indarctos, Huracan and Agriotherium all share morphological traits unique to Ailuropodinae.

Based on these findings, all three of them are now placed within Ailuropodinae, under the tribe Agriotherinii, as opposed to the tribe Ailuropodinii which includes the extant panda and its close relatives (see below).

Agriotherinii

(Indarctos, Agriotherium, Huracan)

  ／

♦Ailuropodinae

  ＼ Ailuropodinii

(Kretzoiarctos, Agriarctos, Ailurarctos, Ailuropoda(modern Panda))

Huracan and Agriotherium are believed to have diverged from some local populations of Indarctos, and the divergence seems to have taken place in East Asia during the Late Miocene, judging from fossil records. Although Huracan's morphologies were intermediate or transitional, Agriotherium's earliest fossil records are older and the distribution of the two overlapped in some areas, so Huracan was not ancestral to Agriotherium, but its closest sister taxon.

<Morphology of Huracan & Agriotherium>

Huracan and Agriotherium were relatively short snouted (while Agriotherium had a shorter muzzle), with teeth well adapted for both slicing and bone crushing, specialized for hyper-carnivorous diet.

They both had long limbs and exhibit a higher degree of cursorial adaptations than in Indarctos. The decline of Indarctos and the rise of Huracan and Agriotherium during the Miocene-Pliocene boundary coincided with global expansions of open environments due to periodic cooling and drying events, indicating that species better adapted to running became advantageous.

Morphometric analysis of distal and proximal forelimb proportions suggests that Huracan and Agriotherium were probably the second most cursorial taxa in Ursidae, after Hemicyonine 'dog-bears' (Hemicyonines were digitigrade as opposed to plantigrade Agriotherines). On the other hand, due to the forelimb features such as the small ratio of the long bone length to peripheral width (smaller this ratio, lankier the limbs) and the weaker humeral epicondyle, forelimb grappling capability in Huracan and Agriotherium was inferior to that of ursine bears and tremarctine Arctodus (Jiangzuo et al., 2023).

The skull of Huracan coffeyi (the largest species) is estimated to have reached condylobasal length of 383–515 mm and total skull length of 411–553 mm (although no complete crania has been found), making its craniodental dimension one of the largest among Ursidae, alongside Arctotherium angustidens and Ursus ingressus.

However, Huracan was proportionally large headed, as the postcranial dimension of Huracan coffeyi was only slightly larger than that of Agriotherium africanum, smaller than Indarctos oregonensis and distinctly smaller than Arctodus simus (Jiangzuo et al., 2023).

＜"Giant Short Faced Bear Phenotypes"＞

Sorkin (2006) once categorized Agriotherium africanum and Arctodus simus together as 'giant short-faced bear morphotypes' (obviously not as taxonomically but phenotypically). Following this manner, we can perhaps categorize Huracan and Agriotherium as 'Ailuropodine giant short-faced bears', while Arctodus and Arctotherium as 'Tremarctine giant short-faced bears'.

In North America, after the extinction of Huracan and Agriotherium during the Pliocene, it may be argued that tremarctine giant short faced bears independently acquired 'similar' ecomorphs to fill the previously occupied niche (although we must also note that tremarctine giant short faced bears were omnivorous and the degree of limb adaptations to running were not as good compared to Agriotherines (Jiangzuo et al., 2023)). The paleoecological and paleoenvironmental factors that led to this convergence, as well as the fact that 'the giant short-faced bear phenotype' has not occurred in the Old World since the extinction of Agriotherine bears must be interesting subjects for discussion.

＜Titanic Match-up : Comparison＞

Hypothetical mighty clash between Huracan coffeyi and Arctodus simus.

Although Jiangzuo et al. (2023) do not provide weight estimates for Huracan coffeyi, its size is described as intermediate between Agriotherium africanum and Arctodus simus. The scientific body mass estimates of A. africanum and A. simus are 317~540 kg (Sorkin, 2008, Oldfield et al., 2012) and 770 kg (Christiansen & Harris, 1999, based on six specimens. Figueirido, 2011 reported several A. simus specimens that may have exceeded 900kg), respectively.

Being 'slightly larger than the former and distinctly smaller than the latter', let's assume that the size of H. coffeyi could be about 450 to 650kg (this is only a guesstimate), for the sake of convenience.

●Huracan’s advantages = larger skull and superior bite force, agility(better cursoriality), probably better killing techniques

●Arctodus' advantages = overall larger size and superior strength(specifically, grappling)

You can vote for the one you believe could be more dominant, from here↓
www.deviantart.com/jagroar/pol…

Thank you in advance for your votes!

Also, next up, the full version of the mid-Pleistocene Steppe Cave lion vs. Homotherium vs. Giant Mid-Pleistocene Brown bear will be up soon, sorry for this delay!

Please stay tuned and look forward to that mega interspecific clash, thank you.

Image and text by ©Jagroar (All rights reserved)

●References●

(Jiangzuo et al., 'New Fossil Giant Panda Relatives (Ailuropodinae, Ursidae): A Basal Lineage of Gigantic Mio-Pliocene Cursorial Carnivores', 2023)

(Abella et al., 'Paleodiversity of the superfamily Ursoidea (Carnivora, Mammalia) in the Spanish Neogene, related to environmental changes', 2014)

(Sorkin, 'Ecomorphology of the giant short-faced bears Agriotherium and Arctodus' , 2006)