Anatomy and Morphology

[brobear]

onlinelibrary.wiley.com/doi/10.1111/mec.12501/abstract
Mammals have diversified into many dietary niches. Specialized myrmecophagous (ant- and termite-eating) placental mammals represent a textbook example of evolutionary convergence driven by extreme diet specialization. Armadillos, anteaters, aardvarks, pangolins and aardwolves thus provide a model system for understanding the potential role of gut microbiota in the convergent adaptation to myrmecophagy. Here, we expand upon previous mammalian gut microbiome studies by using high-throughput barcoded Illumina sequencing of the 16S rRNA gene to characterize the composition of gut microbiota in 15 species representing all placental myrmecophagous lineages and their close relatives from zoo- and field-collected samples. We confirm that both diet and phylogeny drive the evolution of mammalian gut microbiota, with cases of convergence in global composition, but also examples of phylogenetic inertia. Our results reveal specialized placental myrmecophages as a spectacular case of large-scale convergence in gut microbiome composition. Indeed, neighbour-net networks and beta-diversity plots based on UniFrac distances show significant clustering of myrmecophagous species (anteaters, aardvarks and aardwolves), even though they belong to phylogenetically distant lineages representing different orders. The aardwolf, which diverged from carnivorous hyenas only in the last 10 million years, experienced a convergent shift in the composition of its gut microbiome to become more similar to other myrmecophages. These results confirm diet adaptation to be a major driving factor of convergence in gut microbiome composition over evolutionary timescales. This study sets the scene for future metagenomic studies aiming at evaluating potential convergence in functional gene content in the microbiomes of specialized mammalian myrmecophages.
( the sloth bear is not mentioned even though he is indeed a myrmecophagous mammal ).

[brobear]

wildpro.twycrosszoo.org/S/0MCarnivor/ursidae/melursus/Melursus_ursinus/03Melursus_ursinusAMLegs.htm

Sloth bears have relatively short hind legs. The claws of the hind feet are only about 3 cm long but those of the front feet are longer (about 7 cm) and slightly curved, good for digging. The soles of the feet are naked and the digital pads are mainly fused together. The claws are whitish or greyish in colour.
Bears have a caudal extension to the shoulder blade (scapula), called the post-scapular fossa, from which the subscapularis minor muscle arises; this is used in climbing, pulling the bear's body up.

This bear has long, slightly curved claws, good for digging. (B285.w4)
Sloth bears have long (up to 7 cm), curved claws on the front feet, adapted for digging. These are ivory-white, dirty-white or greyish in colour. The claws of the hind feet are about 3 cm long. (B435.w1)
Sloth bears have relatively short hind legs, which may assist in stabilising the body while the forelimbs are used for digging. (B435.w1)
Sloth bears have naked soles of their feet. The five digital pads, arranged in a line, "are fused together up to their distal ends." (B435.w1)

The upper posterior margin of the scapula of the bears has a caudal extension, the post-scapular fossa. From this, on both the lateral and medial surfaces, arises the subscapularis minor muscle, which inserts on the head of the humerus. This muscle is well developed in bears, which is associated with their style of climbing, using the fore limbs to pull the heavy body up trees. (B399.2.w2)

[brobear]

animals.fandom.com/wiki/Sloth_Bear 
 
The Sloth bear (Melursus ursinus), also known as the Stickney bear or labiated bear, is a nocturnal insectivorous species of bears found wild within the Indian Subcontinent. The sloth bear evolved from ancestral brown bears during the Pleistocene and shares features found in insect-eating mammals through convergent evolution. The population isolated in Sri Lanka is considered a subspecies. Unlike brown and black bears, sloth bears have lankier builds, long, shaggy coats that form a mane around the face, long, sickle-shaped claws, and a specially adapted lower lip and palate used for sucking insects. Sloth bears breed during spring and early summer and give birth near the beginning of winter. They feed on termites, honeybee colonies, and fruits. Sloth bears sometimes attack humans who encroach on their territories. Historically, humans have drastically reduced their habitat and diminished their population by hunting them for food and products such as their bacula and claws. These bears have been used as performing pets due to their tameable nature. 
 
Sloth bears are distinguished from Asian black bears by their lankier builds, longer, shaggier coats, pale muzzles and white claws. Adult sloth bears are medium-sized bears, weighing around 130 kg (290 lb) on average, though weight can range variously from 55 to 124 kg (121 to 273 lb) in females and from 80 to 192 kg (176 to 423 lb) in males. They are 60–90 cm (2–3 ft) high at the shoulder, and have a body length of 1.4–1.9 m (4.6–6.3 ft). Females are smaller than males, and have more fur between the shoulders.

Sloth bear muzzles are thick and long, with small jaws and bulbous snouts with wide nostrils. They have long lower lips which can be stretched over the outer edge of their noses, and lack upper incisors, thus allowing them to suck up large numbers of insects. The premolars and molars are smaller than in other bears, as they do not chew as much vegetation. In adults, the teeth are usually in poor condition, due to the amount of soil they suck up and chew when feeding on insects. The back of the palate is long and broad, as is typical in other ant-eating mammals. The paws are disproportionately large, and have highly developed, sickle-shaped, blunt claws which measure 4 in (10 cm) in length. Their toe pads are connected by a hairless web. They have the longest tail in the bear family, which can grow to 6–7 in. Their back legs are not very strong, though they are knee-jointed, and allow them to assume almost any position. The ears are very large and floppy. The sloth bear is the only bear with long hair on its ears.

Sloth bear fur is completely black (rusty for some specimens), save for a whitish Y- or V-shaped mark on the chest. This feature is sometimes absent, particularly in Sri Lankan specimens. This feature, which is also present in Asian black bears and sun bears, is thought to serve as a threat display, as all three species are sympatric with tigers. The coat is long, shaggy, and unkempt, despite the relatively warm environment in which the species is found, and is particularly heavy behind the neck and between the shoulders, forming a mane which can be 30 cm (12 in) long. The belly and under legs are almost bare. 
 
*Quote: "...Sloth bears are distinguished from Asian black bears by their lankier builds..." ( less muscular ).

[brobear]

kids.sandiegozoo.org/animals/sloth-bear

Sloth bears have a great sense of smell, which helps them locate food, but their vision and their hearing is not as good as that of other bears.

[brobear]

Maybe someone here can understand this scientific gibberish... ?

www.worldwidejournals.com/indian-journal-of-applied-research-(IJAR)/article/architecture-of-shoulder-muscles-of-sloth-bear-melursus-ursinus/MTQwNzI=/?is=1

Volume : VII, Issue : XI, November - 2017
ARCHITECTURE OF SHOULDER MUSCLES OF SLOTH BEAR (Melursus ursinus)
Annie V. R, K. V. Jamuna, Arun A. Sha, R. V. Prasad, V. Girish Kumar, Shruti, Rajani Chunkkath, Sunilkumar Patil, Manjunath K, Bharath Kumar

Abstract :
Sloth bear is one of the youngest carnivores occupying a wide range of habitats in Indian subcontinent. Carcass of sloth bears were studied from Bannerghatta Bear Rescue Centre, Bangalore. The study was undertaken to systematically establish the myological characteristics of shoulder region muscle which might help to carryout morphological assessments. In this study it was observed that well developed supraspinous fossa was filled by M. supraspinatus and infraspinous fossa was filled by M. infraspinatus. The powerful deltoideus muscle consisted of two bellies, arose from acromion process and from the fascia overlying M. infraspinatus. Subscapularis muscle was divided into five fascicular tracts and additional subscapularis minor muscle which was positioned medial to M. subscapularis proper. M. coracoachialis consisted of two heads, short head inserted beneath the lesser tubercle and longus inserted on supracondylar crest. In sloth bear attachment of muscle was more proximally compared with other carnivore which may account for slow gait of bears and the muscle mass has reflected the quadrupedal walking of sloth bear.

[King Kodiak]

Maybe someone here can understand this scientific gibberish... ? 

First of all, great find brobear, we dont see many studies on sloth bear anatomy like this.

What i clearly see is couple of things:

In this study it was observed that well developed supraspinous fossa was filled by M. supraspinatus and infraspinous fossa was filled by M. infraspinatus. 

Sloth bears have well developed surpraspinous fossa:

The powerful deltoideus muscle consisted of two bellies, arose from acromion process and from the fascia overlying M. infraspinatus. 

Sloth bears have powerful deltoid muscles.

So it looks like sloth bears might have powerful front limbs. They might be underrated. Awesome find once again.

[OldGreenGrolar]

Sloth bears actually have more robust limbs than expected. They do have the weakest jaws pound to pound but they still can inflict damage with their teeth and especially their claws.

[yz]

Forelimb Comparison Between lion and sloth bear:




Studies used for the above comparison :

www.researchgate.net/publication/354365707_Anatomical_Features_of_Some_Bones_of_the_Forelimbs_of_Lions_Panthera_leo

www.researchgate.net/publication/230843015_Postcranial_morphology_and_the_locomotor_habits_of_living_and_extinct_carnivores

www.semanticscholar.org/paper/What-size-were-Arctodus-simus-and-Ursus-spelaeus-Christiansen/14c1ecaa29bb88d8930fa543279937074628c946

www.researchgate.net/publication/7531697_Body_size_ofSmilodon_Mammalia_Felidae

pubs.geoscienceworld.org/paleobiol/article-abstract/38/1/1/86555/Morphological-convergence-of-the-prey-killing

www.researchgate.net/publication/20806549_Differential_scaling_of_the_long_bones_in_the_terrestrial_carnivora_and_other_mammals

www.researchgate.net/publication/23720916_Forelimb_Indicators_of_Prey-Size_Preference_in_the_Felidae

www.semanticscholar.org/paper/Osteology-and-ecology-of-Megantereon-cultridens-a-%E2%80%93-Christiansen-Adolfssen/f5dd2b7f596ef6b84aff81281e97e6f7f75422a6

www.researchgate.net/publication/280925355_Carnivoran_postcranial_adaptations_and_their_relationships_to_climate

www.ncbi.nlm.nih.gov/pmc/articles/PMC5312108/#:~:text=In%20contrast%20to%20most%20other,force%20couples)%20to%20the%20ground.

academic.oup.com/zoolinnean/article/142/1/91/2691231

www.researchgate.net/publication/298056854_Sexual_selection_on_skeletal_shape_in_Carnivora

As seen, the sloth bear has relatively stronger shoulders, thicker Forelimb bones, larger epicondyles, trochleas,olecrana, shorter forelimbs, bigger paws and the ability to produce more force based on its Forelimb Proportions and foot posture. Overall, the bear seems to have been a proportionally stronger,more robust and more muscular animal.

[brobear]

Architecture of arm muscles of sloth bear (Melursus ursinus)

www.entomoljournal.com/archives/2019/vol7issue1/PartY/7-1-303-744.pdf

Abstract

The present study was undertaken to systematically establish the myological characteristics of the arm region of sloth bear which might help to carryout morphological assessments. Carcasses of sloth bears were obtained from the Bannerghatta Bear Rescue Centre of Bannerghatta Biological Park, Bangalore. In this study it was observed that M. Biceps brachi was principally made up of the long head and its tendon coursed within bicipital groove. M. brachialis lodged in the musculo spiral groove and coursed in a spiral like fashion. M. triceps comprised of five heads with M. triceps longus and medialis again subdivided two parts, got inserted on the olecranon process. M. triceps lateralis was smaller than M. triceps longus which run diagonally across the outer surface of arm. M. anconeus lied deep to the distal part of the M triceps. In sloth bear attachment of muscle was more proximally compared with other carnivore which may account for the slow gait of bears.

[brobear]

The shaggiest bear. 

[OldGreenGrolar]

The shaggy sloth bear.