Glossotherium

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Glossotherium
Skeleton reconstruction of Glossotherium in the Natural History Museum Vienna

Skeleton reconstruction of Glossotherium in the Natural History Museum Vienna

Temporal occurrence
Late Pliocene to Late Pleistocene
3? Millions of years to around 10,000 years
Locations
Systematics
Sub-articulated animals (Xenarthra)
Tooth arms (pilosa)
Sloths (folivora)
Mylodontoidea
Mylodontidae
Glossotherium
Scientific name
Glossotherium
Owen , 1840

Glossotherium is a genus of the extinct family Mylodontidae that includes large ground-dwelling sloths . Along with Mylodon, it is one of the most well-known members of the family. The majority of the Glossotherium findscome from the Middle and Upper Pleistocene around 300,000 to 10,000 years ago, and a few are older, possibly as far back as the Pliocene around 3 million years ago. The distribution area covered large parts of South America from about 20 degrees south latitude upwards with the exception of the Amazon basin . The animals largely inhabited the open landscapes of the pampas and the northern savanna regions .

Like other mylodonts, Glossotherium was adapted to a more or less grassy diet, as indicated by the wide snout and the shape of the teeth. This view is confirmed by isotope studies . The anatomical structure of the musculoskeletal system suggests that animals were four-footed, but they were also able to change into a two-footed stance. The particularly strong structure of the forelimbs is remarkable, which leads to the assumption that Glossotherium burrowed underground. Large fossil burial tunnels with corresponding scratch marks support this assumption, so it is possibly the largest known burrowing mammal at all. The structure of the hearing shows that Glossotherium frequencies in infrasound perceive and could probably produce with the help of his voluminous nose.

The research history of the genus is very complex. The first description was in 1840 by Richard Owen . But he rejected the generic name two years later. In the following years this led to a persistent confusion and equation with Mylodon and other forms, which was only dissolved in the 1920s. Especially in the course of the 20th century, Glossotherium was considered identical to the North American paramylodon . It was not until the 1990s that it became generally accepted that both genres are independent of one another.

features

General

Glossotherium was a medium-sized to large representative of the Mylodonts. Reconstructed, the animals had a total length of 300 to 400 cm, with a fully assembled skeleton totaling 335 cm long, of which about 90 cm was the tail. The weight was around 500 to 1000 kg for more delicate forms, 1200 to 1700 kg for more robust ones. Like all ground-living sloths, Glossotherium had a massive body with short and strong limbs. The head was elongated and the tail was very long compared to today's tree-living sloths.

Skull and dentition features

Skull of Glossotherium
Skull of Glossotherium in side view from the first description of the species G. robustum from 1842
Bottom view of the skull of Glossotherium from the first description of the species G. robustum from 1842

The skull of Glossotherium was typically elongated tubular and rectangular in top and side views. Its length varied from 39.6 to 46.8 cm, the average width in the front snout area was 16.0 cm, behind the eyes 15.4 cm and at the rear end 18.3 cm. A striking feature was the very widened region of the anterior rostrum . The related Mylodon , on the other hand, had a differently structured skull, which was long and narrow in shape and had a closed nasal arch, which was created by the nasal bone that was arched forward and fused with the median jawbone at the front end . The skull of Glossotherium overlapped with that of the closely related Paramylodon in appearance and size . In general, the skull of Glossotherium was much more robust and broader than that of Paramylodon and, unlike the latter, had a dome-like bulge of the forehead line in side view. In the supervision of Glossotherium, there was also a stronger constriction in the area of ​​the lacrimal bone . Glossotherium's generally wider skull also resulted in a wider nostril, with width exceeding height. In Paramylodon , the width and height of the nostril were about the same. In addition, the parasagittal ridges on the parietal bone were further apart than in the Paramylodon . In agreement with most other sloths, the middle jaw bone of Glossotherium was only loosely connected to the nasal bone, while in Mylodon there was firm contact between the two bones due to the closed nasal arch. Again like most of the other sloths but unlike Paramylodon , the zygomatic arch in Glossotherium was not closed. It consists of an anterior and posterior arch section. The posterior one, beginning at the temporal bone , was finger-shaped, the anterior one, beginning at the zygomatic bone , had three processes: one ascending, one descending and one horizontally oriented. The occipital bone was in view from behind a pressed contour with distinct narrowed up and down. This made it different from the oval shape of Lestodon and the almost circular shape of Mylodon . Further peculiarities were developed in the area of ​​the skull base. Here the palatine bone in Glossotherium was not quite as long as in Paramylodon , as it showed significant shortenings behind the last molar. On the other hand , the flanks of the wing bone in Glossotherium were more inflated and thus the distance between them was smaller. Similar formations can be found in numerous other sloths, but their function is unclear.

Lower jaw of Glossotherium
Lower jaw of Glossotherium from the first description of the species G. robustum from 1842

The lower jaw measured between 30.1 and 37.0 cm in length and was therefore on average shorter than that of Paramylodon . The horizontal body of the bone was extremely sturdy; it increased in height from front to back and reached a maximum of 9.5 cm below the last tooth. The lower edge of the lower jaw was straight, like other Mylodonts. With regard to the articular process, this protruded less than the coronary process than in the case of the paramylodon , so the mandibular joint in the case of Glossotherium was on average lower. The entire crown process reached a height of 14.8 to 18.0 cm and was located well above the occlusal plane, the front edge of the process was more vaulted in Glossotherium than in Paramylodon . A striking feature is the symphysis , which was extraordinarily wide and thus reflects the wide snout. It ended at the back at the level of the first tooth, and at the front it had a spoon-like or spatula-like extension that was typical of sloths, which was also wide and rose at an angle of 45 °, but did not reach the chewing plane of the teeth. As a characteristic difference to Paramylodon, the lateral edge of this extension in Glossotherium protruded significantly.

Like the other sloths, the set of teeth was greatly reduced, consisting of five teeth per half of the jaw in the upper jaw and four in the lower jaw, making a total of 18 teeth. The foremost tooth in the jaw branch had a canine-like ( canine - shaped ) shape, the following ones were molar-like ( molar-shaped ). This structure of teeth is seen as ancestral history within the sloth. Notwithstanding paramylodon and Mylodon had Glossotherium the caniniformen always trained teeth, the first setting of the upper jaw were partially reduced Mylodon contrast at all had no caniniformen teeth with him were top formed back, but transformed the lower to molarenartigen. The canine- shaped teeth were oval or triangular in cross-section and there was a short diastema towards the rear dentition . The molar-like molars had a flat chewing surface with a slightly raised edge. They had the two-lobed outline typical of Mylodonts with a strong constriction in the middle. Only the foremost molar tooth of the upper jaw was more square in shape, which in turn represents a difference to the rather long, rectangular first molar-shaped tooth in Paramylodon . There are also differences in the design between the two genera of the second upper molar, since the bilobed structure in Glossotherium was less pronounced than in Paramylodon . As with all sloths, teeth typically lacked enamel . Instead, they consisted of a softer version of the dentin on the inside and a harder variant on the outside ( vasodentin and orthodentin ), plus a layer of dental cement . The length of the upper row of teeth varied between 11.6 and 16.3 cm, but averaged 14.4 cm, of which the molar-like molars took up around 11.2 cm. The forward widening muzzle caused the rows of teeth to diverge from one another.

Body skeleton

The spine consisted of 7 cervical, 16 thoracic, 3 lumbar, 7 sacrum and at least 20 caudal vertebrae. However, the sacrum was designed as a synsacrum , which formed a unit with the lumbar vertebrae and the last thoracic vertebra, as the spinous processes of the corresponding vertebrae were connected to one another and the vertebral bodies were partially fused. The spine performed an S-shaped oscillation, the lowest point being reached on the fourth cervical vertebra and the highest point on the 15th thoracic vertebra. The spinous processes of the thoracic vertebrae protruded obliquely backwards, that of the eighth vertebra was up to 14 cm long. All thoracic vertebrae had ribs, the first nine pairs of which were firmly attached to the sternum . The foremost caudal vertebrae were extremely massive and still resembled the other vertebrae with vertebral arches and transverse and spinous processes. On the underside there were also chevron bones , all in all the front section of the tail was designed in such a way that it could carry extremely strong muscles. However, the size of the caudal vertebrae decreased sharply towards the rear.

The humerus had a roughly columnar, short form, he widened the lower pivot end but massive and worked there spatelartig. Its length varied from 32 to 42 cm. A massive deltopectoral ridge ran around the shaft, a bone ridge that served as a starting point for the upper arm and shoulder muscles. Overall, the humerus was extremely robust compared to that of the gigantic Megatherium . The same applies to the ulna and radius . The latter bone was 24 to 30 cm long, the former up to 36 cm. At the ulna, the upper end of the joint, the olecranon, was noticeably elongated. The femur was short and sturdy. It measured between 44 and 52 cm in length. Typically for ground-dwelling sloths, it had a board-like, flat but broad shape, but the shaft tapered from top to bottom, so that it was around twice as wide near the upper joint end as near the lower one. Due to the great width of the shaft, the third rolling hillock (third trochanter) was not clearly formed. The hemispherical joint head stood out clearly, but did not sit on a pronounced neck. The laterally adjoining large rolling mound ran almost straight and then turned at a right angle to the shaft. The lower end of the joint was somewhat asymmetrical, with the outer joint role being significantly larger than the inner one. Compared to the thigh bone, the shin bone was extremely short and, with dimensions of 23 to 25 cm, did not even reach half its length. The joint ends bulged out far, the upper (knee joint) had a width of three quarters of the shin length. Similar to the femur, the shaft of the tibia was clearly flattened. The almost triangular-prismatic-looking fibula was not firmly attached to the shin.

Reconstructed hand skeleton from Glossotherium

The structure of the hands and feet was similar to that of the other large Mylodons such as Paramylodon , Mylodon and Lestodon , but there are individual deviations from each other. The hand had a total of five rays (I to V), but only the three inner rays (I to III) had claws. The metacarpal bones increased in size from the first to the fourth ray, and the third metacarpus was sometimes up to 11 cm long. The fifth reached the dimensions of the third, but was massive and wide. As a special feature of the large ground-dwelling sloths, the metacarpal bone of the first ray was fused with the large polygonal bone to form a unit (the so-called Metacrapal Carpal Complex or MCC), and the first two phalanges also fused here. There were three phalanges each on rays II and III, but the first two were very short. The respective end links of all three inner rays had extensive claw processes, which suggests correspondingly large claws. The extensions reached lengths of up to 16.5 cm and a height of 4.8 cm. The phalanges of the clawless outer rays were greatly reduced in number and size. The foot had a total of four rays (II to V), the innermost ray (I) was completely regressed. Claws only had toes II and III, which were also the strongest. The metatarsals of the two inner rays were short in length, while those of the outer, clawless toes became extremely massive and long. The first two phalanxes of the innermost (second) ray were fused together and thus corresponded to the first ray of the hand. On the following third ray there were three toe phalanges, which corresponds to Lestodon but differs markedly from Paramylodon , in which only two limbs were sometimes formed. The respective terminal phalanges with claws had an extremely strong structure, analogous to the hand, and had massive claw extensions. On the outer rays, the number and size of the toe joints were again greatly reduced, comparable to the hand.

Osteoderms

Mylodonts are the only group of sloths with small bone platelets called osteoderms embedded in their skin . Such ossified skin formations in mammals are only found in armadillos today . In the Mylodonts, however, the bone platelets do not form a solid armor, but are rather randomly distributed in the skin, as finds from skin remnants of Mylodon show. In terms of research history, Glossotherium discovered osteoderms very early on, as early as 1865 Hermann Burmeister presented finds from the area of ​​the Río Salado in Ecuador . These had a rhombic, trapezoidal or irregular elliptical outline and were between 0.7 and 2.5 cm long. They had a roughened surface with irregular depressions 2 to 3 mm in diameter, while the underside was smooth and convex. Investigations of osteoderms of " Glossotherium " chapadmalense , whose position within the genus is rather uncertain, showed that these were more simply structured in cross-section than those of the armored articulated animals . They had a compact structure and consisted of numerous fiber bundles mixed with hard bone lamellae ( osteomas ).

Distribution and important fossil finds

Glossotherium was widespread in South America, but is largely only known there from the Pleistocene . An exception is the controversial form " Glossotherium " chapadmalense , which is documented from the Middle Pliocene (locally stratigraphically Chapadmalalan ) around 4 to 3 million years ago. Finds come from the type locality near Miramar in the Argentine province of Buenos Aires and include a 39 cm long skull with a lower jaw and a first cervical vertebra . Further finds in the form of several mandibular fragments were reported from Inchasi about 50 km southeast of Potosí in the Bolivian Department of Potosí , the site is at an altitude of 3220 m above sea level.

The vast majority of the finds from Glossotherium date to the later or the late Pleistocene (late phase of the local stratigraphic stage Lujanian ). Older finds from the Middle Pleistocene are very rare, including a right talus from La Huaca in the northern Peruvian region of Piura , which is around 304,000 years old. In the ensuing Young Pleistocene, Glossotherium is spread over large parts of South America with the exception of the areas south of the 20th southern parallel and the Amazon basin. The main distribution area includes central and northern Argentina, Uruguay and southern Brazil . Other important sites are documented from the coastal areas in the southeast and east of Brazil in the states of Paraná , Minas Gerais and Bahia . In addition, the genus was found in Venezuela , Colombia , the coastal lowlands or (less often) in the Andean regions of Ecuador , Peru and Chile as well as Bolivia . From Chile, an almost complete skeleton from Lonquimay in the Región de la Araucanía is the only specimen of the genus in the country to date. The animals mainly inhabited more open landscapes such as the pampas regions of central South America (Argentina, Uruguay and Brazil), but also the savannah landscapes further north . Mainly in the pampas the occurrence overlaps with those of the other large Mylodonten of the Pleistocene South America, Mylodon and Lestodon . At individual find locations such as in Arroyo del Vizcaíno in southern Uruguay or on the Chuí River in southeastern Brazil, all three genus of Mylodont occur together.

The frequent evidence of Glossotherium at the end of the Pleistocene coincides with the disappearance of the genus in the course of the Quaternary extinction wave . The latest finds of the genus also overlap with the arrival of early hunter-gatherer groups in southern America. Whether the early human colonizers of America had a direct influence on the disappearance of the ground sloth is unclear, clear interactions are only known to a few. One of the few sites with the legacies of hunter-gatherer groups associated with the remains of Glossotherium is that of Arroyo Seco 2, a multi-phase archaeological site in the Argentine province of Buenos Aires, whose age with the help of the radiocarbon method is about 12,400 to 7,300 C14- Years prior to being dated today. In addition to numerous stone artefacts , which mainly contain finer preparation waste for the production of tools with sharp cutting edges, bone remains of large mammals were also found, including a few bones from Glossotherium . Direct age determinations of these finds indicate that the Glossotherium remains were stored in the earlier section of the sediment formation (about 12,240 to 10,500 years ago BP ). Another important site is Paso Otero 5, also located in the province of Buenos Aires. In the archaeological area investigated since 1994, more than 80,000 bone fragments came to light, but some of them were badly broken and could hardly be determined. The assignable bones included two bone fragments from Glossotherium . Around 80 stone tools made of quartzite were also discovered, including fish tail points . The age of the site is 10,440 to 10,190 years BP, but in this case the determination was not made on the remains of Glossotherium , but of Megatherium . Isolated references have also been passed down from other parts of South America, but their interpretation is uncertain. For example, from the Abri of Santa Elina in the Brazilian state of Mato Grosso , a storage area with the remains of a fireplace was examined in the 1990s, in the vicinity of which there were jaw and vertebral parts as well as hundreds of osteoderms of Glossotherium . The age of the fireplace has been dated to around 10,120 C14 years BP. One of the osteoderms was pierced, but this can also be attributed to biogenic influences. On the other hand, the direct relationship between the Glossotherium relics and the fireplace is largely unclear. In Taima-taima on the coastal zone of north-central Venezuela, in addition to a skeleton of Notiomastodon , in whose body an El Jobo-type projectile tip was stuck, individual remains of Glossotherium came to light, but these may not be directly related to the hunting ground. The age of the sediments in which the finds are embedded is around 13,390 to 12,580 years ago.

Paleobiology

Sexual dimorphism

In some skulls, differences in the expression of individual characteristics can be seen. So there are individuals with oval and small caniniform teeth in cross-section , while others are triangular and larger. Often large canine-like teeth are accompanied by diverging rows of teeth, smaller rows with parallel ones. There are also certain metric differences in the teeth and on the lower jaw. The variations are interpreted as an expression of a sexual dimorphism with larger teeth in males and smaller teeth in females. Something similar was found in the closely related paramylodon .

Locomotion

Skeleton reconstruction of a young Glossotherium , the posture of the front and rear feet can be seen

Like the other large ground sloths, Glossotherium moved mostly quadruped. The very short lower leg section compared to the upper one, which is typical of Mylodonts, is striking. In the type specimen of Glossotherium , the thighbone reaches a length of 48 cm, while the shinbone is only 21 cm long, which is less than half that. Shortened lower leg lengths are often associated with a clumsy gait, comparable to today's rhinos , while long lower leg sections as with horses go hand in hand with more agile locomotion. Referring to a similarly large representative of the ground sloths to Glossotherium , Pyramiodontherium from the group of Megatheriidae had approximately the same length of upper and lower leg sections with 49 and 47 cm respectively. The ratio roughly corresponds to that of today's lamas . Accordingly, the Mylodonts including Glossotherium are likely to have moved much more heavily than the Megatheria. When running, Glossotherium placed the hind feet on the outer edge, i.e. on the fifth ray, whereby the soles of the feet were directed inwards. The type of locomotion is called pedolateral and, with the exception of the Megalonychidae, is developed in all ground-living sloths; the rotation of the foot caused a noticeable remodeling of the foot skeleton. In addition to the fifth ray, in the Mylodonts the calcaneus touched the ground along its entire length. As a result, the foot was less arched than in the related Scelidotheriidae , in which only the rear end of the calcaneus was in contact with the ground.

It is often discussed whether mylodonts were able to dig. In Glossotherium , the very strong forelegs, which are about 30% more robust than the hind limbs, are particularly noticeable. The ulna has an extensive upper articular process, the triceps muscle attached here can enormously increase the leverage of the forearm and develop power. For example, with a total bone length of 36 cm , the olecranon requires around 13 cm, which corresponds to around 35%. The value is in the lower range of today's armadillos , which sometimes appear as good graves. In addition, the hands with the distinctive claw-bearing rays II and III are suitable for digging in the ground. According to the stress analyzes, the symmetrical and clearly curved claws withstood the tensile and compression forces that occurred. In the region around Mar del Plata in the Argentine province of Buenos Aires , some old, buried burrows of animals have been excavated, the age of which ranges from the Old to the New Pleistocene . Some of these are extremely large corridor systems with a diameter of 80 to 180 cm and a length that can sometimes be up to 40 m. The larger of these structures could be related to Glossotherium , whose basin width of about 120 cm correlates well with the duct width. Also on some walls there were parallel grooved scratch marks of up to 110 cm in length and with a groove spacing of 3 to 4 cm, which is also in accordance with the hand of Glossotherium . Some of the corridors contain deeper hollows up to 240 cm in diameter, the development of which was also found the chafing of the fur of the animals on the ground and possibly acted as resting places. Similar structures are also known from southeastern Brazil. Based on these clues, the representative sloth could be one of the largest known mammals to pursue a burrowing way of life. Today this position is occupied by the aardvark with a weight of up to 65 kg. Phascolomus , an extinct wombat that also lived in the Pleistocene, was long considered the largest burrowing mammal with an estimated body weight of 200 to 300 kg. The possibly burrowing way of life was supported by the fact that the center of gravity of Glossotherium, like other ground sloths, is very far back. As a result, about 69% of the body weight rested on the hind legs. The body's center of gravity, which was shifted far back, also enabled the animals to get up on their hind legs more easily and thus get their arms free for digging. A half-upright or half-crouching position is best known from today's armadillos digging. As a further indication of digging activity at Glossotherium , an often complete or partial adhesion of the first two thoracic vertebrae can be assessed, which occurs among other things in numerous small mammals with a corresponding way of life. However, it is not entirely clear whether this is a pathological finding or whether the adhesions developed in an evolutionary supportive manner as a result of a heavy load on the neck, for example when digging with the head. Other very large ground sloths such as Megatherium do not have such formations in the thoracic spine so far. As possible causes for a burrowing way of life at Glossotherium , in addition to the general search for food, among other things, the flight from predators , such as the saber-toothed cat Smilodon or the short- snouted bear Arctotherium , which, as extremely large predators, inhabited the open landscapes of the pampas at that time, are mentioned. Since such large underground corridors can also be visited by large predators without major problems, the protection offered in the buildings against extreme temperature fluctuations or against water loss in dry areas is a more likely reason for the possibly digging activities of Glossotherium .

The assumed digging way of life has so far not been supported by anatomical examinations of the inner ear . The orientation and position of the semicircular canals to one another determine the sense of balance and thus also the ability to rotate the head with an optimum at around 90 °. Burrowing animals often have narrow semicircular canals, which is not the case with Glossotherium . In addition, the width of the semicircular canals has an influence on the agility of an animal with narrow semicircular canals with dominant slow movements and wide ones with fast movements. The latter applies to Glosdsotherium . In the entire structure of the inner ear, the genus strongly resembles Megatherium and less clearly to today's tree sloths. In addition, there are stronger similarities with the anteaters . So far, however, the effect of body size on closely related forms has not been clarified, as the giant ground sloths differ significantly from the small tree sloths in this regard.

Diet

The characteristic teeth of Glossotherium are very high crowned. Together with the rather flat chewing surface of the molar teeth, this speaks in comparison to other higher mammals such as ungulates for a diet based on largely hard plants such as grasses . Since the sloth's teeth are structured differently than those of the ungulates, this conclusion is not clear. However, the view of a more herbivorous diet is partly due to the design of the mouth, which is strikingly wide due to the wide mandibular symphysis. It is possible that Glossotherium also had broad, bulging lips, as indicated by various roughened surfaces on the rostrum . This made the mouth of Glossotherium look like that of today's white rhinoceros . This feeds mainly on hard grass forage in open landscapes and can ingest a large amount of grass with its wide mouth, although it is not very selective. Something similar is suspected for Glossotherium , just as this particular diet was likely for a larger part of the Mylodonts. In addition to the lips, the tongue also played a supporting role in eating. This is closed due to the position of the hyoid bone , which is shifted far back in the skull , which is also built robustly and has strong muscle attachment points. As a result, the geniohyoideus muscle , for example, was particularly strong and long and is involved in the movement of the tongue. In Glossotherium , the cranial-mandibular junction is at or slightly above the occlusal plane, the mandibular joint is laterally protruding and convex, while the glenoid pit into which the joint on the skull engages and appears slightly indented. The former suggests that the bite force is probably low, which is also indicated by the somewhat forward row of molars. The design of the joint connection, on the other hand, allowed wide rotational movements when chewing. Traces of wear on the teeth indicate that predominantly forward and lateral chewing movements predominated. The non-closed zygomatic arch is a limiting factor in the chewing movements . Due to the lack of closure , it was only able to withstand the counteracting forces of the two large mastication muscles, the masseter and pterygoid muscles (wing muscle), which is why more laterally oriented chewing movements probably played a subordinate role .

Like all mylodonts, Glossotherium has a comparatively very small total occlusal surface of all teeth together. This is 830 to 1280 mm², a similarly large Indian rhinoceros , on the other hand, has a total sales area of ​​2660 to 5190 mm², three to four times as high. Today's sloths have a very low metabolic rate , which is also assumed for the extinct forms. If the stomach was also chambered several times, as with the recent representatives, Glossotherium probably digested the majority of its food in the gastrointestinal tract and was thus able to compensate for the low processing capacity of the teeth. Due to the assumed long transit time of the food, it was possible to split it up more, which might enable the animals to use more fibrous plant parts. Since the teeth of the sloth do not contain tooth enamel , isotope measurements for a more direct determination of food have so far only been possible to a limited extent. More recent research approaches make it possible to obtain such information from other parts of the skeleton. For Glossotherium this was achieved with the help of an osteoderm. As a result it could be shown that at least the animals in the pampa region lived predominantly on food containing grass, which confirms the anatomical evidence.

Soft tissues and sensory services

The soft tissue is very rarely passed on in extinct organisms , so we can usually only speculate about a possible coat of fur in Glossotherium . The rather small recent, tree-dwelling sloths are densely hairy, fossilized hair has been documented for the extinct Mylodon, which is closely related to Glossotherium , as well as for some more distantly related forms such as Nothrotheriops from the group of Nothrotheriidae . From Glossotherium a partial skeleton from the left bank of the Arroyo Balta comes, about 3 km before its confluence with the Río Luján in the Argentine province of Buenos Aires. A matrix adhered to the surface of individual bones, such as the skull, which contained fossilized hair in the form of tube-like formations. The tubes still reveal the scaled outer skin of the cuticle (scale layer) and the hair cortex, the scales are arranged in waves. But inside they are hollow. It cannot currently be clarified whether this cavity was caused by weathering or whether the hair, analogous to that of today's sloths and the findings in Mylodon, had no pith.

Skeletal reconstruction of Glossotherium , the wide nostril can be seen

Today's sloths tend to have poorly developed sensory functions, including hearing . The spoken language is severely restricted as a result, communication often only takes place between the young and the mother, the latter being stimulated above all in frequency ranges from 2 to 8  kHz . From Glossotherium are isolated ossicles handed. The hammer and anvil are exceptionally large, they have a combined weight of 500 mg, the footplate of the stapes has an area of ​​7.4 mm². Due to the size of the tympanic ring in the middle ear of 18.4 by 14.4 mm, an area of ​​the eardrum of 200 mm² can be deduced . The dimensions are slightly larger than those of the related but significantly larger sloth Lestodon . In addition, they are among the largest known of land-living mammals; in the Asian elephant , all three ossicles weigh around 160 to 320 mg combined. Comparative studies on modern mammals suggest that Glossotherium could perceive sounds in the low frequency range up to infrasound . Accordingly, the lower ranges of sound perception were around 0.044 kHz, the optimum around 1.7 kHz, which is roughly in the range of the recent sloths. The possible upper limit was probably 15 kHz. The low-frequency tones in particular offer numerous advantages in open landscapes, as they are less susceptible to disturbances in the form of vegetation or terrain. They are therefore a suitable means of communication with conspecifics over long distances. This is the case with the elephants, whose calls are carried up to 10 km after sunset. The modulation of sounds in the recent sloths is carried out by puffs of air through the nostrils. With Glossotherium these were extraordinarily wide with 9.6 to 12.1 cm. This enabled the animals to theoretically generate sounds in the frequency range of 0.6 kHz using the loudspeaker principle , which in turn is ideally suited for transport over long distances.

Predators and diseases

Predatory damage on a humerus of Glossotherium

Some of the bones of Glossotherium have typical features that can be traced back to predatory feeding marks . Some of these show punctured bites at the joint ends of long bones, some bones were also broken and the internal cancellous material processed. Some of the traces point to very large representatives of the predators, which could come from the group of big cats or bears . The already mentioned large predators Smilodon and Arctotherium weighed in reconstructed 400 kg and more. At least for Smilodon , a prey spectrum in the weight range of 1 to 2 tons is given, which means that Glossotherium is definitely a potential victim of the big cat. It is unclear, however, whether the feeding marks on Glossotherium go back to captured animals or whether it is scavenging . Similar cases have also been documented in the related Mylodon .

Examination of more than 170 Glossotherium bones revealed pathological changes in at least 7.5% of the fossil remains . These mainly concerned the joint structures on the long bones and the vertebrae. Among other things, pseudogout , osteoarthritis , Schmorl cartilage nodules and spondylosis were identified. Some of the diseases such as pseudogout were probably caused by age, while others are due to the large body weight.

Systematics

Internal systematics of the Mylodontidae according to Boscaini et al. 2019 (based on skeletal anatomical analyzes)
 Mylodontidae  


 Urumacotherium


   

 Pseudoprepotherium



   


 Paroctodontotherium


   

 Octodontotherium



   

 Brievabradys


   



 Lestodon


   

 Bolivartherium



   

 Thinobadistes


   

 Sphenotherus


   

 Lestobradys





   

 Pleurolestodon


   


 "Glossotherium" chapadmalense


   

 Simomylodon



   



 Kiyumylodon


   

 Mylodon



   

 Paramylodon



   

 Glossotherium









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Internal systematics of the sloths according to Presslee et al. 2019 (based on protein analysis)
 Folivora  

 Megalocnoidea


   

 Megatherioidea


  Mylodontoidea  

 Scelidotheriidae


   

 Choloepodidae


  Mylodontidae  

 Lestodon


   

 Paramylodon


   

 Mylodon


   

 Glossotherium









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Glossotherium is an extinct genus from the also extinct family of the Mylodontidae . The Mylodontidae belong to the suborder of the sloths (Folivora), within which they form the superfamily of the Mylodontoidea together with the Orophodontidae and the Scelidotheriidae (sometimes the Scelidotheriidae and the Orophodontidae are also only listed as a subfamily within the Mylodontidae). According to a classic structure based on skeletal anatomical features, the Mylodontoidea represent the second large and important line of sloths alongside the Megatherioidea . Molecular genetic studies and protein analyzes add a third line to these two with the megalcnoidea . According to the latter two studies, the Mylodontoidea also includes the two-toed sloth ( Choloepus ), one of the two species of sloth still alive today. The Mylodontidae form one of the most diverse groups within the sloth. Their characteristics include high-crowned teeth with, unlike the Megatherioidea, flat ( lobater ) chewing surfaces, which is interpreted as an adaptation to food with a higher concentration of grass. The rear teeth have a round or oval cross-section, the front ones have a canine-like shape. The rear foot is also clearly rotated so that the sole points inwards. One of the earliest records of the Mylodonts is Paroctodontotherium , which is recorded in Salla-Luribay in Bolivia and dates back to the Oligocene .

The internal structure of the Mylodontidae is complex and varies depending on the processor. Most recognized are the late groups of the Mylodontinae with Mylodon as the type form and the Lestodontinae , whose character form is Lestodon ( called Mylodontini and Lestodontini on the tribal level). Paramylodon and Glossotherium are also included in the latter . In the past, numerous other subfamilies were established, such as the Nematheriinae for representatives from the Lower Miocene or the Octomylodontinae for all basal forms, which are not generally recognized. Another group are the Urumacotheriinae, which were only established in 2004 and include the late Miocene representatives of northern South America. In principle, some researchers are calling for a revision for the entire family, as many of the higher taxonomic units have no formal diagnosis.

However, the subdivision of the terminal group of the Mylodonts into the subfamilies of the Lestodontinae and Mylodontinae was largely confirmed in one of the most extensive studies on the tribal history of the sloths to date . The study, published in 2004 by Timothy J. Gaudin , was based on cranial features and suggests a close relationship between Glossotherium and other lestodontins. In addition, the study found a close relationship between Paramylodon and Mylodon , but the former shows strong anatomical similarities to Glossotherium . that this is closer to Lestodon . Although this relationship could be reproduced several times in the following years, other authors viewed this more critically, as illustrated, for example, in a study by Luciano Varela and research colleagues from the year 2019, including numerous taxa from the entire subordination of the sloth. According to this, Glossotherium and Paramylodon form a close unit, Lestodon groups with individual forms from northern South America and Mylodon initiates the development of modern Mylodonts. A higher-resolution phylogenetic analysis of the mylodonts from the same year, provided by a team led by Alberto Boscaini , underpins the branching of the terminal representatives. In contrast to Varela and colleagues, Glossotherium and Paramylodon form a common clade here together with Mylodon . A fundamental difference between the Mylodontinae and Lestodontinae can be found in the form of the canine-like front teeth, which in the latter are large and separated from the rear teeth by a long diastema, but in the former are only small in size or are partially reduced and closer to the molar-like teeth Teeth. According to this study, Glossotherium belongs to the immediate relational environment around Paramylodon and Mylodon within the Mylodontinae. This constellation was supported by the aforementioned biochemical analyzes, also published in 2019. A study by Robert K. McAfee , published in 2009, demonstrated the close relationship between Glossotherium and Paramylodon on the basis of cranial morphological aspects and came to the conclusion that both genera most likely have a common ancestor share. Common features of the two genera can be found in the structure of the dentition with the front canine-shaped teeth and in the tooth structure, such as the second molar. The position of the bone seam between the palatine bone and the upper jaw near the rearmost tooth is also very prominent. Mylodon, on the other hand, has a reduced set of teeth, more simply designed teeth and an advanced bone connection between the palatine bone and the upper jaw, so it differs more markedly from the other two genera.

In the course of time numerous species have been described within the genus Glossotherium , the following species are found more frequently in the literature and are sometimes listed as valid:

By far the most important and best-known species is G. robustum . Some of the other species mentioned above are also synonymous with G. robustum , although this does not happen very uniformly. Morphological studies show that there are noticeable differences, especially in the structure of teeth and skulls, between some fossil remains that are more northerly than those found further south. Accordingly, the genus Glossotherium could actually include several species. In this case, the remains of G. robustum are limited to the 40th to 20th parallel to the south, the fossil remains further north would have to be assigned to one or more other species. Some more recent studies therefore recognize at least G. tropicorum and G. wegneri as independent. Especially from the early research period, there are numerous species that are now synonymous with G. robustum . These include the Mylodon gracilis , introduced by Hermann Burmeister in 1865 , as well as forms such as Pseudolestodon reinhardtii , Pseudolestodon morenoii and, in some cases, Pseudolestodon myloides , all of which were established in 1880 by Henri Frédéric Paul Gervais and Florentino Ameghino , as well as by Max hexaspondylestodon Rautenberg from 1906. Other forms in turn were excluded from the genus Glossotherium and assigned to other representatives such as Mylodonopsis .

Internal systematics of Glossotherium according to Cartelle et al. 2019
 Glossotherium  

 G. robustum


   

 Pleurolestodon


   

 G. tropicorum


   

 G. phoenesis





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However, a phylogenetic study from 2019 taking into account the different species of Glossotherium suggests that the genus does not form a self-contained group and includes pleurolestodon . This shape was significantly smaller and appeared as early as the Miocene . As a consequence, either Pleurolestodon would have to be incorporated into Glossotherium or the latter genus would have to be split up. However, since there is too little material from the other representatives with the exception of G. robustum , one of these steps has not yet been carried out.

The " Glossotherium " chapadmalense species , which was introduced by Lucas Kraglievich in 1925 and is based on a skull from near Miramar in the Argentine province of Buenos Aires, is considered problematic . The find dates to the Middle Pliocene , making " G. " chapadmalense the oldest representative of Glossotherium . The species is also known from simultaneous layers in North America and is sometimes considered to be the forerunner of the local Paramylodon (it may then be called Paramylodon garbanii there ). Overall, the shape is slightly smaller than Glossotherium and shows individual deviations from the actual Glossotherium like a narrower snout. Should " G. " chapadmalense actually represent the ancestor of both Glossotherium and Paramylodon , the species would have to be assigned to a new genus. Eumylodon , a name that Kraglievich already used when listing the species, but rejected three years later, would be an option . At present the finds of this early species are too small and the original material too badly damaged to make a clear decision on the systematic position.

Research history

Initial description

Richard Owen (1856)
The holotype of Glossotherium , the Owen in his first description used

The taxonomic history of Glossotherium is complex and characterized by a long-standing equation, mixing and confusion with Mylodon and Paramylodon . The scientific name goes back to Richard Owen (1804-1892), one of the most important researchers of the Victorian era. From 1836 onwards, Owen investigated fossil finds that Charles Darwin had brought back from his seminal voyage with the HMS Beagle to South America . Among them was a rear part of a skull (copy number NHM 16586) from the bed of the Arroyo Sarandí in today's Uruguayan Department of Soriano . In 1840, Owen referred the skull fragment to the newly created genus Glossotherium , but without including a special species. The name is of Greek origin and is made up of the words γλῶσσα ( glossa ) for "tongue" and θηρίον ( thērion ) for "animal". Owen induced a round depression of around 2.5 cm in diameter near the ear region to assign the name. The recess serves as a starting point for the hyoid bone , which in turn supports the tongue. Due to the size and design of this attachment point, Owen concluded that there was an enormous tongue that apparently helped the animals to eat. For this reason, he also saw the skull closer to anteaters and pangolins standing and forecast an insect eat literary life for Glossotherium .

Mylodon , Glossotherium, and Grypotherium

In the same script, Owen set up the genus Mylodon , which he saw as being related to the other large ground sloths known at the time, such as Megatherium or Megalonyx . Mylodon is based on a lower jaw with four molar-like teeth that Darwin had recovered near Punta Alta in the south of the Argentine province of Buenos Aires . In honor of Darwin, Owen named the species as Mylodon darwinii (sometimes the spelling Mylodon darwini is also used) and established it as a type of the genus. Only two years later, however, Owen rejected the name Glossotherium again. At this time he published a paper in which he described an almost complete skull with associated body skeleton (copy number NHM M2500). The finds had been discovered the year before by M. Pedro in the flood plains of the Río de la Plata north of Buenos Aires . The skull was characterized by a wide snout, a total of 18 teeth were formed in the dentition, the foremost tooth in each case had a canine-like design. Together with the description of the skeleton, Owen introduced the new species Mylodon robustus for this , and the skull fragment that he had originally assigned to Glossotherium was now associated with Mylodon darwinii in the essay .

Skull of Mylodon

In 1879 the description of a skull and lower jaw made of Pergamino , also located in the province of Buenos Aires, was published by the Danish zoologist Johannes Theodor Reinhardt (1816–1882). The narrow snout of the skull, which also had a nasal arch closed at the front, was striking, as the nasal bone was firmly fused with the median jawbone. In addition, the dentition consisted of a total of 16 teeth, the upper front canine-like tooth was reduced, while in the lower jaw there were four molar-like teeth. Reinhardt recognized that the lower jaw was similar to that of Mylodon darwinii , but the skull with its narrow snout differed from the broad-snouted one of Mylodon robustus . Reinhardt also pointed out that the skull fragment, which Owen originally used to establish the genus Glossotherium and later classified as Mylodon darwinii , corresponds to the corresponding skull sections in Mylodon robustus . Reinhardt then propagated the new genus Grypotherium with Grypotherium darwinii as the type form. Florentino Ameghino (1854–1911) later confirmed, in 1889, the separation of the two species at the genus level. In contrast to Reinhardt, however, he saw the lower jaw of Mylodon darwinii and the skull fragment of Glossotherium as belonging together, and he also pointed out that Glossotherium had priority over Mylodon and Grypotherium in this scenario and thus introduced Glossotherium darwinii . Ameghino left the species Mylodon robustus unchanged. In contrast, Arthur Smith Woodward (1864–1944) followed Reinhardt's argument in 1900. In an article he presented finds of ground sloths from southern Patagonia and revised the collection of Charles Darwin. He equated the lower jaw of Mylodon darwinii with Reinhardt's Grypotherium and subsequently restored Grypotherium darwinii . In contrast, he referred the skull fragment of Glossotherium to Mylodon robustus .

At the end of the 1920s, Lucas Kraglievich (1886–1932) dealt with the taxonomy of the South American ground sloth, and especially with Mylodon , Glossotherium and Grypotherium . Using the features of the skull, he worked out that the three names are clearly to be assigned to two different genera. The description of Mylodon darwinii by Owen linked the generic name firmly with the specific epithet . Kraglievich presented Mylodon darwinii as a type of the genus and assigned it to the complete, narrow- snouted skull and lower jaw of Reinhardt's Grypotherium from Pergamino, as well as the lower jaw from Punta Alta, which Owen had used in his first description of the species. The latter is the type specimen of the species. Owens Mylodon robustus , based on a skull with a broad snout, he referred to the genus Glossotherium , which Owen had not associated with any species at the time. At the same time, Kraglievich found the name Glossotherium robustum unsuitable for the type species of the genus, rather he gave this status to the newly established form Glossotherium uruguayensis . Kraglievich based the new species on the skull fragment that Owen had once used to describe Glossotherium in 1840. Kraglievich failed to underpin his unusual step with an elaboration of different characteristics of the two species, which was not done by subsequent authors either. Since the original skeleton of Mylodon robustus was destroyed in the bombing of London during World War II, this is no longer possible in retrospect. Today Glossotherium robustum is generally recognized as a type of the genus, while Glossotherium uruguayensis is considered a synonym.

Glossotherium and Paramylodon

Skeletal reconstruction of Paramylodon , the shape was long considered identical to Glossotherium

In addition to Mylodon darwinii , Owen introduced another representative of the genus in 1840 with Mylodon harlani . The basis for this species was formed by a lower jaw and a collarbone from Big Bone Lick in Boone County in the US state of Kentucky , which Richard Harlan had already described in 1831 as Megalonyx laqueatus . Owen recognized similarities with his Mylodon darwinii based on the lower jaw and renamed Harlan's shape. As a result, three species of Mylodon had already been described in the 1840s , giving the sloth representative a very wide distribution, ranging from southern South America to North America. A sharp increase in the number of fossil remains in the further course of the 19th century in North America led to the establishment of the genus Paramylodon by Barnum Brown in 1903 . With its broad snout, Paramylodon clearly resembled Glossotherium (which Brown led under the name Mylodon robustus ), but in contrast to this, had reduced the front upper canine-like teeth. However, some 14 years later, Chester Stock reunited paramylodon with mylodon , referring to his research on the mylodonts from the asphalt pits of Rancho La Brea in southern California .

It was not until 1928 that Kraglievich, in his essay on the taxonomic and systematic separation of Glossotherium and Mylodon, assigned all North American finds to Paramylodon , an opinion that Ángel Cabrera also took eight years later . The strong similarity of Glossotherium and Paramylodon led in the following time to the fact that both genera were equated. George Gaylord Simpson pointed out in his general taxonomy of mammals in 1945 that if Paramylodon could not be clearly separated from Glossotherium , the name Glossotherium should be preferred because of this naming priority . Robert Hoffstetter then introduced Paramylodon in 1952 as a subgenus of Glossotherium , with which the latter, like Mylodon before, received a distribution far beyond the American double continent. This also gave the genus a high degree of variability. During this time Glossotherium developed into a "trash can" taxon in which numerous closely related mylodontic forms were set. The congeneric nature of the two genera was advocated by numerous researchers as the 20th century progressed. It was not until 1995, however, that H. Gregory McDonald emphasized that there were no studies to date in which the synonymy of the two genera was proven. He then separated the North American Paramylodon from the South American Glossotherium , whereby in his opinion the isolation of Paramylodon in North America tended to support the independence of the form. At the beginning of the 21st century, the clear separation of the two genera and also of Mylodon could be worked out in several skull studies .

literature

  • Richard A. Fariña, Sergio F. Vizcaíno and Gerardo De Iuliis: Megafauna. Giant beasts of Pleistocene South America. Indiana University Press, 2013, ISBN 978-0-253-00230-3 , pp. 209-212 and 248-254
  • Robert K. McAfee: Reassessment of the cranial characters of Glossotherium and Paramylodon (Mammalia: Xenarthra: Mylodontidae). Zoological Journal of the Linnean Society 155, 2009, pp. 885-903

Individual evidence

  1. ↑ In it A. Croft and Velizar Simeonovski: Horned armadillos and rafting monkeys. The fascinating fossil mammals of South America. Indiana University Press, 2016, pp. 1–304 (pp. 228–229)
  2. ↑ a b c d e Richard Owen: Description of the skeleton of an extinct gigantic Sloth, Mylodon robustus, Owen, with observations on the osteology, natural affinities, and probable habitats of the Megatherioid quadrupeds in general. London, 1842, pp. 1–176 (especially p. 154) ( [1] )
  3. ^ A b Richard A. Fariña, Sergio F. Vizcaíno and María S. Bargo: Body mass estimations in Lujanian (Late Pleistocene-Early Holocene of South America) mammal megafauna. Mastozoología Neotropical 5 (2), 1998, pp. 87-108
  4. ↑ a b c M. Susana Bargo, Sergio F. Vizcaíno, Fernando M. Archuby and R. Ernesto Blanco: Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) mylodontid ground sloths (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 20 (3), 2000, pp. 601-610
  5. ↑ Per Christiansen and Richard A. Fariña: Mass estimation of two fossil ground sloths (Mammalia, Xenarthra, Mylodontidae). Senckenbergiana biologica 83 (1), 2003, pp. 95-101
  6. ↑ a b c d Lucas Kraglievich: “Mylodon darwini” Owen es la especie genotipo de “Mylodon” Ow. Rectificacíon de la nomenclatura genérica de los Milodontes. Physis 9, 1928, pp. 169-185
  7. ↑ a b Diego Brandoni, Brenda S. Ferrero and Ernesto Brunetto: Mylodon darwini Owen (Xenarthra, Mylodontinae) from the Late Pleistocene of Mesopotamia, Argentina, with Remarks on Individual Variability, Paleobiology, Paleobiogeography, and Paleoenvironment. Journal of Vertebrate Paleontology 30 (5), 2010, pp. 1547-1558
  8. ↑ Luciano Brambilla and Damián A. Ibarra: The occipital region of late Pleistocene Mylodontidae of Argentina. Boletín del Instituto de Fisiografía y Geología 88, 2018, pp. 1–9
  9. ↑ a b c d M. Susana Bargo and Sergio F. Vizcaíno: Paleobiology of Pleistocene ground sloths (Xenarthra, Tardigrada): biomechanics, morphogeometry and ecomorphology applied to the masticatory apparatus. Ameghiniana 45 (1), 2008, pp. 175-196
  10. ↑ a b c d e f g h i j k Robert K. McAfee: Reassessment of the cranial characters of Glossotherium and Paramylodon (Mammalia: Xenarthra: Mylodontidae). Zoological Journal of the Linnean Society 155, 2009, pp. 885-903
  11. ↑ a b c d e Vanessa Gregis Pitana, Graciela Irene Esteban, Ana Maria Ribeiro and Cástor Cartelle: Cranial and dental studies of Glossotherium robustum (Owen, 1842) (Xenarthra: Pilosa: Mylodontidae) from the Pleistocene of southern Brazil. Alcheringa: An Australasian Journal of Palaeontology 37 (2), 2013, doi: 10.1080 / 03115518.2012.717463
  12. ^ A b M. Susana Bargo, Gerardo De Iuliis and Sergio F. Vizcaíno: Hypsodonty in Pleistocene ground sloths. Acta Palaeontologica Polonica 51 (1), 2006, pp. 53-61
  13. ^ Daniela C. Kalthoff: Microstructure of Dental Hard Tissues in Fossil and Recent Xenarthrans (Mammalia: Folivora and Cingulata). Journal of Morphology 272, 2011, pp. 641-661
  14. ↑ a b c Max Rautenberg: About Pseudolestodon hexaspondylus. Stuttgart, 1906, pp. 1-50
  15. ↑ a b c Vanessa Gregis Pitana: Estudo do gênero Glossotherium Owen, 1840 (Xenarthra, Tardigrada, Mylodontidae), Pleistoceno do Estado do Rio Grande do Sul, Brasil. Universidade Federal do Rio Grande do Sul, Porto Alegre, 2011, pp. 1-183
  16. ^ Robert K. McAfee: Description of New Postcranial Elements of Mylodon darwinii Owen 1839 (Mammalia: Pilosa: Mylodontinae), and Functional Morphology of the Forelimb. Ameghiniana 53 (4), 2016, pp. 418-443
  17. ^ Cástor Cartelle: Estudo comparativo do rádio e esqueleto da mao de Glossotherium (Ocnotherium) giganteum Lund, 1842. Anais da Academia Brasileira de Ciências 52 (2), 1980, pp. 359-376
  18. ↑ a b Chester Stock: Structure of the pes in Mylodon harlani. University of California Publications. Bulletin of the Department of Geology 10 (16), 1917, pp. 267-286
  19. ↑ a b Chester Stock: Cenozoic gravigrade edentates of western North America with special reference to the Pleistocene Megalonychinae and Mylodontidae of Rancho La Brea. Carnegie. Institute of Washington 331, 1925, pp. 1-206
  20. ↑ José A. Haro, Adan A. Tauber and Jerónimo M. Krapovickas: The Manus of Mylodon darwinii Owen (Tardigrada, Mylodontidae) and Ist Phylogenetic Implications. Journal of Vertebrate Paleontology 36 (5), 2016, p. E1188824, doi: 10.1080 / 02724634.2016.1188824
  21. ^ FP Moreno and A. Smith Woodward: On a Portion of Mammalian Skin, named Neomylodon listai, from a Cave near Consuelo Cove, Last Hope Inlet, Patagonia. By Dr. FP Moreno, CMZS With a Description of the Specimen by A. Smith Woodward, FZS Proceedings of the Zoological Society 1899, pp. 144-156.
  22. ↑ a b Hermann Burmeister: skin armor at Mylodon. Archive for Anatomy, Physiology and Scientific Medicine 1865, pp. 334–336
  23. ^ Robert V. Hill: Comparative Anatomy and Histology of Xenarthran Osteoderms. Journal of Morphology 267, 2005, pp. 1441-1460
  24. ↑ a b c d e Cástor Cartelle, Gerardo De Iuliis, Alberto Boscaini and François Pujos: Anatomy, possible sexual dimorphism, and phylogenetic affinities of a new mylodontine sloth from the late Pleistocene of intertropical Brazil. Journal of Systematic Palaeontology 17 (23), 2019, pp. 1957–1988, doi: 10.1080 / 14772019.2019.1574406
  25. ↑ a b Lucas Kraglievich: Cuatro nuevos gravigrados de la fauna Araucana "Chapadmalense". Anales del Museo Nacional de Historia Natural de Buenos Aires33, 1925, pp. 215-235
  26. ↑ Federico Anaya and Bruce J. MacFadden: Pliocene mammals from Inchasi, Bolivia: The endemic fauna just before the Great American Interchange. Bulletin of the Florida Museum of Natural History 39 (3), 1995, pp. 87-140
  27. ^ François Pujos and Rodolfo Salas: A systematic reassessment and paleogeographic review of fossil Xenarthra from Peru. Bulletin de l'Institut Français d'Etudes Andines, 33, 2004, pp. 331-378
  28. ↑ a b Luciano Varela and Richard A. Fariña: Co-occurrence of mylodontid sloths and insights on their potential distributions during the late Pleistocene. Quaternary Research 85, 2016, pp. 66-74
  29. ↑ a b Hans P. Püschel, Thomas A. Püschel and David Rubilar-Rogers: Taxonomic comments of a Glossotherium specimen from the Pleistocene of Central Chile. Boletín del Museo Nacional de Historia Natural, Chile 66 (2), 2017, pp. 223–262
  30. ↑ Richard A. Fariña, P. Sebastián Tambusso, Luciano Varela, Ada Czerwonogora, Mariana Di Giacomo, Marcos Musso, Roberto Bracco and Andrés Gascue: Arroyo del Vizcaíno, Uruguay: a fossil-rich 30-ka-old megafaunal locality with cut- marked bones. Proceedings of the Royal Society B 281, 2014, doi: 10.1098 / rspb.2013.2211
  31. ↑ Jamil Corrêa Pereira, Renato Pereira Lopes and Leonardo Kerber: New remains of Late Pleistocene mammals from the Chuí Creek, Southern Brazil. Revista Brasileira de Paleontologia 15 (2), 2012, pp. 228-239
  32. ↑ a b Marína A. Gutiérrez and Gustavo A. Martínez: Trends in the faunal human exploitation during the Late Pleistocene and Early Holocene in the Pampean region (Argentina). Quaternary International 191, 2008, pp. 53-68
  33. ^ Gustavo G. Politis, Clara Scabuzzo and Robert H. Tykot: An Approach to Pre-Hispanic Diets in the Pampas during the Early / Middle Holocene. International Journal of Osteoarchaeology 19, 2009, pp. 266-280
  34. ^ Gustavo Martínez, María Gutiérrez and José Luis Prado: New Archaeological Evidences from the Late-Pleistocene / Early-Holocene Paso Otero 5 Site (Pampean Region, Argentina). Current Research in the Pleistocene 21, 2004, pp. 16-18
  35. ↑ Gustavo Martínez: Arqueolgía del curso medio del Río Quequén Grande: Estado actual y aportes a la arqueología de la región Pampeana. Relaciones de la Sociedad Argentina de Antropología 31, 2006, pp. 249-275
  36. ^ Gustavo Martínez, María A. Gutiérrez and Eduardo P. Tonni: Paleoenvironments and faunal extinctions: Analysis of the archaeological assemblages at the Paso Otero locality (Argentina) during the Late Pleistocene-Early Holocene. Quaternary International 299, 2013, pp. 53-63
  37. ^ Agueda Vilhena Vialou, Thierry Aubry, Mohammed Benabdelhadi, Cástor Cartelle, Levy Figuti, Michel Fontugne, Maria Eugenia Solari and Denis Vialou: Découverte de Mylodontinae dans un habitat préhistorique daté du Mato Grosso (Brésil Elina de Santa rupest). Comptes Rendus de l'Academie Sciences Paris 320, 1995, pp. 655-661
  38. ↑ Alex Hubbe, Mark Hubbe and Walter A. Neves: The Brazilian megamastofauna of the Pleistocene / Holocene transition and its relationship with the early human settlement of the continent. Earth Science Review 118, 2013, pp. 1-10
  39. ^ Alan J. Bryan, Rodolfo M. Casamiquela, José M. Cruxent, Ruth Gruhn and Claudio Ochsenius: An El Jobo Mastodon Kill at Taima-Taima, Venezuela. Science 200, 1978, pp. 1275-1277
  40. ↑ Ruth Gruhn and Alan J. Bryan: The record of Pleistocene megafaunal extinction at Taima-taima, Northern Venezuela. In: Paul S. Martin and Richard G. Klein (Eds.): Quaternary Extinctions. A Prehistoric Revolution. The University of Arizona Press, Tucson AZ, 1984, pp. 128-137
  41. ^ H. Gregory McDonald: Sexual dimorphism in the skull of Harlan's ground sloth. Contribution in Science 510, 2006, pp. 1-9
  42. ↑ Gerardo De Iuliis, Guillermo H. Ré and Sergio F. Vizcaíno: The Toro Negro megatheriine (Mammalia, Xenarthra): A new species of Pyramiodontherium and a review of Plesiomegatherium. Journal of Vertebrate Paleontology 24 (1), 2004, pp. 214-227
  43. ^ A b H. Gregory McDonald: Evolution of the Pedolateral Foot in Ground Sloths: Patterns of Change in the Astragalus. Journal of Mammalian Evolution 19, 2012, pp. 209-215
  44. ↑ Santiago Pantiño and Richard A. Fariña: Ungual phalanges analysis in Pleistocene ground sloths (Xenarthra, Folivora). Historical Biology 29 (8), 2017, pp. 1065-1075, doi: 10.1080 / 08912963.2017.1286653
  45. ↑ Santiago Pantiño, Jorge Peréz Zerpa and Richard A. Fariña: Finite element and morphological analysis in extant mammal's claws and Quaternary sloth 'ungual phalanges. Historical Biology, 2019, doi: 10.1080 / 08912963.2019.1664504
  46. ↑ Francisco Segikurch de Carvalho Buchmann, Heinrich Theodor Frank, Victor Moreira Ferreira Sandim and Erick Cruz Antal: Evidência de vida Gregaria em paleotocas attribuítas a Mylodontidae (Preguiças gigantes). Revista Brasileira de Paleontologia 19 (2), 2016, pp. 259-270
  47. ↑ a b Renato Pereira Lopez, Heinrich Theodor Frank, Francisco Sekiguchi de Carvalho Buchmann and Felipe Caron: Megaichnus igen. nov .: Giant paleoburrows attributed to extinct Cenozoic mammals from South America. Ichnos 24 (2), 2017, pp. 133–145, doi: 10.1080 / 10420940.2016.1223654
  48. ↑ a b Sergio F. Vizcaíno, Marcelo Zaráte, M. Susana Bargo and Alejandro Dondas: Pleistocene burrows in the Mar del Plata area (Argentina) and their probable builders. Acta Palaeontologica Polonica 46 (2), 2001, pp. 289-301
  49. ↑ Alejandro Dondas, Federico I. Isla and José L. Carballido: Paleocaves exhumed from the Miramar Formation (Ensenadan Stage-age, Pleistocene), Mar del Plata, Argentina. Quaternary International 210, 2009, pp. 44-50
  50. ↑ P. Sebastián Tambusso, Luciano Varela and H. Gregory McDonald: Fusion of anterior thoracic vertebrae in Pleistocene ground sloths. Historical Biology, 2018, doi: 10.1080 / 08912963.2018.1487419
  51. ↑ Hervé Bocherens, Martin Cotte, Ricardo Bonini, Daniel Scian, Pablo Straccia, Leopoldo Soibelzon and Francisco J. Prevosti: Paleobiology of sabretooth catSmilodon populator in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from carbon and nitrogen stable isotopes in bone collages. Palaeogeography, Palaeoclimatology, Palaeoecology 449, 2016, pp. 463-474
  52. ^ Richard A. Fariña, Sergio F. Vizcaíno and Gerardo De Iuliis: Megafauna. Giant beasts of Pleistocene South America. Indiana University Press, 2013, ISBN 978-0-253-00230-3 , pp. 209-212 and 248-254
  53. ↑ Alberto Boscaini, Dawid A. Iurino, Guillaume Billet, Lionel Hautier, Raffaele Sardella, German Tirao, Timothy J. Gaudin and François Pujos: Phylogenetic and functional implications of the ear region anatomy of Glossotherium robustum (Xenarthra, Mylodontidae) from the Late Pleistocene of Argentina. The Science of Nature 105, 2018, p. 28, doi: 10.1007 / s00114-018-1548-y
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