''Sthenurus'' ("strong tail") is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

kangaroo Kangaroos are marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use, the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...

s. With a length around 3 m (10 ft), some species were twice as large as modern extant species. ''Sthenurus'' was related to the better-known '' Procoptodon''. The subfamily Sthenurinae is believed to have separated from its sister taxon, the Macropodinae (kangaroos and wallabies), halfway through the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, and then its population grew during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58

Fossil habitats

A 1997 study analysed the diets of the fauna at various fossil site localities in South Australia, using stable

carbon isotope Carbon (6C) has 14 known isotopes, from to as well as , of which only and are stable. The longest-lived radioisotope is , with a half-life of years. This is also the only carbon radioisotope found in nature, as trace quantities are formed ...

analysis 13C/12C of

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

. It found that at older localities such as Cooper Creek, the species of ''Sthenurus'' were adapted to a diet of leaves and twigs (

browsing Browsing is a kind of orienting strategy. It is supposed to identify something of relevance for the browsing organism. In context of humans, it is a metaphor taken from the animal kingdom. It is used, for example, about people browsing open sh ...

) due to the wet climate of the time between 132 and 108 thousand years ago (kya - by

thermoluminescence dating Thermoluminescence dating (TL) is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediment ...

and uranium dating), which allowed for a more varied vegetation cover. At the Baldina Creek fossil site 30 kya ( C14 dating), the genus had transitioned to a diet of grass-

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

. During this time, the area was open grasslands with sparse tree cover as the continent was drier than today, but at Dempsey's Lake (36-25 kya) and Rockey River (19 kya C14 dating), their diet was of both grazing and browsing. This analysis may be because of a wetter climatic period. The overall anatomy of the genus did not alter in response to the change in diet and dentition did not adapt to the varying toughness of the vegetation between grasses, shrubs, and trees. Other animals found in the Cuddie Springs habitat include the flightless bird '' Genyornis'', the

red kangaroo The red kangaroo (''Osphranter rufus'') is the largest of all kangaroos, the largest terrestrial mammal native to Australia, and the Largest mammals#Marsupials (Marsupialia), largest extant marsupial. It is found across mainland Australia, exce ...

, '' Diprotodon'', humans, and many others. Examination of skeletal remains of ''Sthenurus'' from Lake Callabonna, northern South Australia, revealed that as the animals were trapped as they floundered in the clay mud while attempting to cross the floor of the lake during low-water or dry times. The data show that three closely allied sthenurine species coexisted sympatrically at Lake Callabonna: a new giant taxon, ''S. stirlingi'', an intermediate-sized ''S. tindalei'', and the considerably smaller ''S. andersoni''. Comparative osteology of these ''Sthenurus'' species with '' Macropus giganteus'' emphasizes how different sthenurine kangaroos were from extant kangaroos, especially with the sthenurines' short, deep skulls, long front feet with very reduced lateral digits, and the monodactyl hind feet. Teapot Creek, a tributary of the MacLaughlin River in the Southern Monaro, southeastern New South Wales, contains a sequence of terraces. The highest and oldest of these terraces was reported to contain the remains of fossil mammals found in Plio-Pleistocene fossil deposits elsewhere in eastern Australia. ''Sthenurus atlas'', ''S. occidentalis'', and ''S. newtonae'' are some of the species identified from the fossils found in the terrace.

Paleodiet

Examining the structure and lifestyle of this species is difficult because not much material has surfaced in regards to them. However, even within the rarity of discoveries relating to the kangaroo-like species, scientists were able to use their findings to learn more about their lifestyles. For example, scientists broke down the few bones that they had discovered during the process of isotope analysis (which is the study of the distribution of certain isotopes that ease the process of drawing conclusions when determining food chains) and retrieved material which allowed them to draw the conclusion regarding their paleodiet. These animals were herbivores because the material they retrieved drew back to the plantation that was Australia (where their bones were found).By: Grocke, DR AUSTRALIAN JOURNAL OF BOTANY Volume: 45 Issue: 3 Pages: 607-617 Published: 1997

Anatomy

thumb , Life restoration Sthenurus stirlingi

In anatomy, they had a tail shorter but stronger than present species of kangaroos, and only one toe instead of three like the red kangaroo. At the end of the foot was a small hoof-like nail suited for flat terrain; this toe is considered their fourth toe. Their skeletal structure was very robust with powerful hind limbs, a broad pelvis, a short neck, and longer arms and

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

than modern species. Their phalanges may have been used to hold stems and twigs. These unique adaptations suited their feeding habits of browsing in the case of ''S. occidentalis'', but other species were most likely grazers. The body mass of the largest species is estimated to be , nearly three times that of the largest extant species. Due to their giant height and weight, the largest species possibly did not hop as a form of locomotion, but rather walked bipedally in a similar manner to

hominids The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...

. This gait would have been used at slow speeds, since hopping at slow speeds would have been inefficient. Pentapedal movement and bipedal hopping no longer seem to have been options for these massive kangaroos. A morphological difference exists between the scapulae (shoulder blades) of the Sthenurine and the extant and extinct macropodids. They possessed a short, deep skull, which was suited for

stereoscopic vision Binocular vision is seeing with two eyes, which increases the size of the visual field. If the visual fields of the two eyes overlap, binocular depth can be seen. This allows objects to be recognized more quickly, camouflage to be detected, spa ...

; this allowed for better depth perception.

Skull

''S. stirlingi'' had a large, dolichocephalic skull with a more elevated braincase position and an inflamed nasal frontal region in comparison to the contemporaneous skull of ''S. tindelai''. ''S. andersoni'' skull fossils show a dome-like forehead that is unique to it among other dolichocephalic sthenurines. This is attributed to the continuous high vaulting of the frontals above the orbits and the line of the rostrum.

Teeth

These structures were tough and strongly enamelled, useful for tough vegetation and with a striation pattern. In ''S. stirlingi'', fossil evidence shows that the tooth row curves medially (anteriorly and posteriorly) from a line tangential to the labial side of the molars at the anterior ridge of the masseteric processes. The fossils of teeth may also suggest that the sthenurines and macropodines shared a common ancestor. They share many synapomorphic character states. They each have well-developed lophs on molars and both lack a posthypocristid.

Human interaction

From evidence gathered at Cuddie Springs, Native Australians inhabited the same habitat as that of ''Sthenurus'' and various other

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

and

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of animals. At this locality, a lack of any specific tools suitable for hunting seems to occur. Instead, tools used to cut meat off the bone and blood residue left on the stone tools were found. Any material made of wood for hunting, such as the

boomerang A boomerang () is a thrown tool typically constructed with airfoil sections and designed to spin about an axis perpendicular to the direction of its flight, designed to return to the thrower. The origin of the word is from Australian Aborigin ...

and

spear A spear is a polearm consisting of a shaft, usually of wood, with a pointed head. The head may be simply the sharpened end of the shaft itself, as is the case with Fire hardening, fire hardened spears, or it may be made of a more durable materia ...

, has either not survived intact or was not used by the people of the time in this locality. While this evidence may suggest that human contact with ''Sthenurus'' spp. and the remainder of the Australian megafauna could have caused the extinction of these mammals, some studies show the extinction was probably under way before human contact. ''Sthenurus'' spp. were herbivores, and when a great climate change began to occur, they did not change their eating habits. This probably had a much larger impact on this particular genus regarding extinction.

References

*Gavin Prideaux, "Systematics and Evolution of the Sthenurine Kangaroos" (April 1, 2004). UC Publications in Geological Sciences. Paper vol_146. http://repositories.cdlib.org/ucpress/ucpgs/vol_146

External links

Victoria museum.Sthenurus from the American Museum of Natural History.Naracoorte caves.
{{Taxonbar, from=Q142888 Prehistoric macropods Prehistoric mammals of Australia Pleistocene marsupials Prehistoric marsupial genera Taxa named by Richard Owen Fossil taxa described in 1873