''Thylacoleo'' ("pouch lion") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of carnivorous

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

s that lived in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

from the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

(2 million to 46 thousand years ago). Some of these marsupial lions were the largest

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

ian predators in Australia of their time, with ''

Thylacoleo carnifex ''Thylacoleo'' ("pouch lion") is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene (2 million to 46 thousand years ago). Some of these marsupial lions were the largest mammalian pred ...

'' approaching the weight of a

lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphi ...

ess. The estimated average weight for the species ranges from .

Taxonomy

The genus was first published in 1859, erected to describe the type species ''Thylacoleo carnifex''. The new taxon was established in examination of fossil specimens provided to

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owe ...

. The familial alliance takes its name from this description, the so-called marsupial lions of

Thylacoleonidae Thylacoleonidae is a family of extinct meat-eating marsupials from Australia, referred to as marsupial lions. The best known is ''Thylacoleo carnifex'', also called the marsupial lion. The clade ranged from the Late Oligocene to the Pleistoc ...

. The colloquial name "marsupial lion" alludes to the superficial resemblance to the placental lion and its ecological niche as a large predator. ''Thylacoleo'' is not closely related to the modern lion (''

Panthera leo The lion (''Panthera leo'') is a large cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphic; adult ...

''). Genus: ''Thylacoleo'' (''Thylacopardus'') – Australia's marsupial lions, that lived from about 2 million years ago, during the Late Pliocene Epoch and became extinct about 30,000 years ago, during the Late Pleistocene Epoch. Three species are known: *''Thylacoleo carnifex'' The holotype cranium was collected from Lake Colongulac in 1843 by pastoralist William Adeney. A partial rostrum collected by Adeney in 1876 from the same locality would later be found to belong to the same individual. *''Thylacoleo crassidentatus'' lived during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

. *''Thylacoleo hilli'' lived during the Pliocene and was half the size of ''T. crassidentatus''. It is the oldest member of the genus. Fossils of other representatives of Thylacoleonidae, such as ''

Microleo ''Microleo attenboroughi'' is a very small species of the Thylacoleonidae family of marsupials from the Early Miocene of Australia, living in the wet forest that dominated Riversleigh about 18 million years ago. The genus ''Microleo'' is curre ...

'' and ''

Wakaleo ''Wakaleo'' (indigenous Australian ''waka'', "little", "small", and Latin ''leo'', "lion") was a genus of medium-sized thylacoleonids that lived in Australia in the Late Oligocene and Miocene Epochs. Although much smaller than its close relativ ...

'', date back to the Late Oligocene Epoch, some 24 million years ago. ''T. hilli'' was described by Neville Pledge in a study published in the records of the South Australia Museum in 1977. The holotype is a third premolar, discovered at a cave in

Curramulka Curramulka is a town in the Australian state of South Australia on the Yorke Peninsula. Curramulka is within easy driving distance of the coastal resort towns of Port Victoria and Port Vincent and is north-east of Minlaton. At the , Curramu ...

in South Australia, exhibiting the carnivorous characteristics of the genus and around half the size of ''T. carnifex''. This tooth was collected by Alan Hill, a speleologist and founding member of the Cave Exploration Group of South Australia, while examining a site known as the "Town Cave" in 1956; the specific epithet ''hilli'' honours the collector of the first specimen. Material found amidst the fauna at

Bow River The Bow River is a river in Alberta, Canada. It begins within the Canadian Rocky Mountains and winds through the Alberta foothills onto the prairies, where it meets the Oldman River, the two then forming the South Saskatchewan River. These w ...

in New South Wales, dated to the early

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 A fragment of an incisor, unworn and only diagnosable to the genus, was located at a site in Curramulka, close to the Town Cave site, and referred to the species for the apparent correlation in size when compared to the better known ''T. carnifex''. The marsupial lion is classified in the order Diprotodontia along with many other well-known marsupials such as kangaroos,

possums Possum may refer to: Animals * Phalangeriformes, or possums, any of a number of arboreal marsupial species native to Australia, New Guinea, and Sulawesi ** Common brushtail possum (''Trichosurus vulpecula''), a common possum in Australian urban a ...

, and the

koala The koala or, inaccurately, koala bear (''Phascolarctos cinereus''), is an arboreal herbivorous marsupial native to Australia. It is the only extant representative of the family Phascolarctidae and its closest living relatives are the womb ...

. It is further classified in its own

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

, the

, of which three

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

and 11

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

are recognised, all extinct. The term marsupial lion (lower case) is often applied to other members of this family. Distinct possum-like characteristics led ''Thylacoleo'' to be regarded as members of

Phalangeroidea The Phalangeroidea are a superfamily of mammals that include the families Burramyidae and Phalangeridae The Phalangeridae are a family of mostly nocturnal marsupials native to Australia, New Guinea, and Eastern Indonesia, including the cusc ...

for a few decades. Though a few authors continued to hint at phalangeroid affinities for thylacoleonids as recently as the 1990s, cranial and other characters have generally led to their inclusion within

vombatiformes The Vombatiformes are one of the three suborders of the large marsupial order Diprotodontia. Seven of the nine known families within this suborder are extinct; only the families Phascolarctidae, with the koala, and Vombatidae, with three extan ...

, and as stem-members of the wombat lineage. Marsupial lions and other ecologically and morphologically diverse vombatiforms were once represented by over 60 species of

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...

and

arboreal Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...

forms ranging in size from 3 kg to 2.5 tonnes. Only two families represented by four

species (koalas and three species of wombat) have survived into modern times and are considered the marsupial lion's closest living relatives.

Evolution

The ancestors of

thylacoleonid Thylacoleonidae is a family of extinct meat-eating marsupials from Australia, referred to as marsupial lions. The best known is '' Thylacoleo carnifex'', also called the marsupial lion. The clade ranged from the Late Oligocene to the Pleistocene ...

s are believed to have been

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

s, something unusual for carnivores. They are members of the

Vombatiformes The Vombatiformes are one of the three suborders of the large marsupial order Diprotodontia. Seven of the nine known families within this suborder are extinct; only the families Phascolarctidae, with the koala, and Vombatidae, with three extan ...

, an almost entirely herbivorous order of marsupials, the only extant representatives of which are

s and

wombat Wombats are short-legged, muscular quadrupedal marsupials that are native to Australia. They are about in length with small, stubby tails and weigh between . All three of the extant species are members of the family Vombatidae. They are adap ...

s, as well as extinct members such as the diprotodontids and

palorchestids Palorchestidae is an extinct family of diprotodont marsupials whose members are sometimes referred to as marsupial tapirs due to their superficial similarity to true tapirs. Genera The family consists of the following four genera: * ''Propalorc ...

. The group first appeared in the Late

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

. The earliest thylacoleonids like ''

'' were small possum-like animals, with the group increasing in size during the

Miocene The Miocene ( ) is the first 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 means "less recen ...

, with representatives like the leopoard sized ''

.'' The genus ''Thylacoleo'' first appeared during the

. The youngest representative of ''Thylacoleo'' and the thylacoleonids, ''T. carnifex'', is the largest known member of the family.

Description

''T. carnifex'' is the

largest Large means of great size. Large may also refer to: Mathematics * Arbitrarily large, a phrase in mathematics * Large cardinal, a property of certain transfinite numbers * Large category, a category with a proper class of objects and morphisms (o ...

carnivorous

known to have ever existed in Australia, and one of the larger

metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well ...

n carnivores of the world (comparable to ''

Thylacosmilus ''Thylacosmilus'' is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though ''Thylacosmilus'' looks similar to the " saber-toothed cats", it was not a felid, like the ...

'' and ''

Borhyaena ''Borhyaena'' is an extinct genus of South American metatherian, living between 17.5 and 15.5 million years ago in Patagonia, Argentina ( Santa Cruz and Sarmiento Formations) and Chile ( Río Frias Formation).''Proborhyaena gigantea''). Individuals ranged up to around high at the shoulder and about from head to tail. Measurements taken from a number of specimens show they averaged in weight, although individuals as large as might not have been uncommon, and the largest weight was of . This would make it comparable to female lions and female

tiger The tiger (''Panthera tigris'') is the largest living cat species and a member of the genus '' Panthera''. It is most recognisable for its dark vertical stripes on orange fur with a white underside. An apex predator, it primarily preys on u ...

s in general size.

Bite

Pound for pound, ''T. carnifex'' had the strongest bite of any

species, living or extinct; a ''T. carnifex'' weighing had a bite comparable to that of a 250 kg African

, and research suggests that ''Thylacoleo'' could hunt and take prey much larger than itself. Larger animals that were likely prey include ''

Diprotodon ''Diprotodon'' (Ancient Greek: "two protruding front teeth") is an extinct genus of marsupial from the Pleistocene of Australia, containing one species, ''D. optatum''. The earliest finds date to 1.77 million to 780,000 years ago, but most speci ...

'' spp. and giant kangaroos. It seems improbable that ''Thylacoleo'' could achieve as high a bite force as a modern-day lion; however, this might have been possible when taking into consideration the size of its brain and skull. Carnivores usually have rather large brains when compared to

marsupials, which lessens the amount of bone that can be devoted to enhancing bite force. ''Thylacoleo'' however, is thought to have had substantially stronger muscle attachments and therefore a smaller brain. Using

3D modeling In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based representation of any surface of an object (inanimate or living) in three dimensions via specialized software by manipulating edges, vertices, an ...

based on

X-ray computed tomography An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...

scans, marsupial lions were found to be unable to use the prolonged, suffocating bite typical of living big cats. They instead had an extremely efficient and unique bite; the incisors would have been used to stab at and pierce the flesh of their prey while the more specialised carnassials crushed the

windpipe The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the la ...

, severed the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

, and lacerated the major

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s such as the

carotid artery Carotid artery may refer to: * Common carotid artery, often "carotids" or "carotid", an artery on each side of the neck which divides into the external carotid artery and internal carotid artery * External carotid artery, an artery on each side of t ...

and

jugular vein The jugular veins are veins that take deoxygenated blood from the head back to the heart via the superior vena cava. The internal jugular vein descends next to the internal carotid artery and continues posteriorly to the sternocleidomastoid ...

. Compared to an African lion which may take 15 minutes to kill a large catch, the marsupial lion could kill a large animal in less than a minute. The skull was so specialized for big game that it was very inefficient at catching smaller animals, which possibly contributed to its extinction.

Postcranium

Thylacoleo skeleton in Naracoorte Caves (cropped)

''Thylacoleo'' had extremely strong forelimbs, with retractable, cat-like claws, a trait previously unseen in marsupials. ''Thylacoleo'' also possessed enormous hooked claws set on large semi-opposable thumbs, which were used to capture and disembowel prey. The long muscular tail was similar to that of a kangaroo. Specialised tail bones called

chevrons Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock l ...

allowed the animal to balance on its back legs, and freed the front legs for slashing and grasping. Retractable claws would remain sharp by protecting them from being worn down on hard surfaces. The first digits (" thumbs") on each hand were semi-opposable and bore an enlarged claw.

Palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s believe this would have been used to grapple its intended prey, as well as providing it with a sure footing on tree trunks and branches. The hind feet had four functional toes, the first digit being much reduced in size, but possessing a roughened pad similar to that of

, which may have assisted with climbing. The discovery in 2005 of a specimen which included complete hind feet provided evidence that the marsupial lion exhibited

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δάκ� ...

(fused second and third toes) like other diprotodonts. Its strong forelimbs and retracting claws mean that ''Thylacoleo'' possibly climbed trees and perhaps carried carcasses to keep the kill for itself (similar to the

leopard The leopard (''Panthera pardus'') is one of the five extant species in the genus '' Panthera'', a member of the cat family, Felidae. It occurs in a wide range in sub-Saharan Africa, in some parts of Western and Central Asia, Southern Russia, a ...

today). The climbing ability would have also helped them climb out of caves, which could therefore have been used as dens to rear their young. Due to its unique predatory morphology, some scientists have claimed ''Thylacoleo'' to be the most specialised mammalian carnivore of all time. ''Thylacoleo'' had vertical shearing 'carnassial' cheek teeth that are relatively larger than in any other mammalian carnivore. ''Thylacoleo'' was clearly derived from the

diprotodontia Diprotodontia (, from Greek language, Greek "two forward teeth") is the largest extant order (biology), order of marsupials, with about 155 species, including the kangaroos, Wallaby, wallabies, Phalangeriformes, possums, koala, wombats, and many ...

n ancestry due to its incisor morphology and is distinguished by the pronounced development of upper and lower third premolars which functioned as extreme

carnassial Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...

s with complementary reduction in the molar teeth row. They also had canines but they served little purpose as they were stubby and not very sharp.

Behaviour and diet

Diet

When ''Thylacoleo'' was first described by Richard Owen, he considered it to be a carnivore, based on the morphology of its skull and teeth. However other anatomists, such as

William Henry Flower Sir William Henry Flower (30 November 18311 July 1899) was an English surgeon, museum curator and comparative anatomist, who became a leading authority on mammals and especially on the primate brain. He supported Thomas Henry Huxley in an imp ...

disagreed. Flower was the first to place ''Thylacoleo'' with the Diprotodonts, noting its skull and teeth to be laid out more like those of the

and the

, and suggested that it was more likely a herbivore. Owen did not disagree with Flower's placement of ''Thylacoleo'' with the Diprotodonts, but still maintained that it was a carnivore, despite its herbivorous ancestry. Owen found little support in his lifetime, despite the pointing out of ''Thylacoleos retractable claws, something only found in mammalian carnivores, and its lack of any ability to chew plant material. In 1911, a study by Spencer and Walcott claimed that certain marks on the bones of megafauna had been made by ''Thylacoleo'', but according to Horton (1979) they were not sufficiently rigorous, resulting in their arguments being strongly challenged by later scholars, such as Anderson (1929), and later Gill (1951, 1952, 1954), thereby leaving the issue unresolved. In 1981, another paper was published arguing that certain cuts to bones of large marsupials had been caused by ''Thylacoleo''. This paper by Horton and Wright was able to counter earlier arguments that such marks were the result of humans, largely by pointing out the presence of similar marks on the opposite side of many bones. They concluded that humans were extremely unlikely to have made the marks in question, but that if so "they had set out to produce only marks consistent with what ''Thylacoleo'' would produce". Since then, the academic consensus has emerged that ''Thylacoleo'' was a predator and a hypercarnivore. Besides the most common hypothesis that it was an active predator, a variety of other theories existed in the late 19th to early 20th centuries as to the diet and feeding of ''Thylacoleo'', with hypotheses of it being a scavenger filling the ecological niche of

hyenas Hyenas, or hyaenas (from Ancient Greek , ), are feliform carnivoran mammals of the family Hyaenidae . With only four extant species (each in its own genus), it is the fifth-smallest family in the Carnivora and one of the smallest in the cla ...

, being a specialist of crocodile eggs, or even a melon-eater. As late as 1954, doubts were still being raised as to whether it was actually a hypercarnivore. The marsupial lion's limb proportions and muscle mass distribution indicate that, although it was a powerful animal, it was not a particularly fast runner. Paleontologists conjecture that it was an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey us ...

, either sneaking up and then leaping upon its prey, or dropping down on it from overhanging tree branches. This is consistent with the depictions of the animal as striped: camouflage of that kind is needed for stalking and hiding in a largely forested habitat (like

tigers The tiger (''Panthera tigris'') is the largest living cat species and a member of the genus ''Panthera''. It is most recognisable for its dark vertical stripes on orange fur with a white underside. An apex predator, it primarily preys on un ...

) rather than chasing across open spaces (like

lions The lion (''Panthera leo'') is a large cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphic; adult ...

). Trace fossils in the form of claw marks and bones from caves in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

analyzed by Gavin Prideaux et al. indicate marsupial lions could also climb rock faces, and likely reared their young in such caves as a way of protecting them from potential predators. It is thought to have hunted large animals such as the enormous ''

'' and giant

browsing Browsing is a kind of orienting strategy. It is supposed to identify something of relevance for the browsing organism. When used about human beings it is a metaphor taken from the animal kingdom. It is used, for example, about people browsing o ...

kangaroo Kangaroos are four 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 like '' Sthenurus'' and '' Procoptodon'', and competed with other predatory animals such as the giant monitor lizard, ''

Megalania Megalania (''Varanus priscus'') is an extinct species of giant monitor lizard, part of the megafaunal assemblage that inhabited Australia during the Pleistocene. It is the largest terrestrial lizard known to have existed, reaching an estimated ...

'', and terrestrial crocodiles such as ''

Quinkana ''Quinkana'' is an extinct genus of mekosuchine crocodylians that lived in Australia from about 28 million to about 10,000 years ago. Most attributed specimens have been found in Queensland. It is speculated to have been one of the top predators ...

''. The marsupial lion may have cached kills in trees in a manner similar to the modern

. Like many predators, it was probably also an opportunistic

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

, feeding on

carrion Carrion () is the decaying flesh of dead animals, including human flesh. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...

and driving off less powerful predators from their kills. It also may have shared behaviours exhibited by recent

diprotodont Diprotodontia (, from Greek "two forward teeth") is the largest extant order of marsupials, with about 155 species, including the kangaroos, wallabies, possums, koala, wombats, and many others. Extinct diprotodonts include the hippopotamus-sized ...

marsupials such as kangaroos, like digging shallow holes under trees to reduce body temperature during the day.

Senses

CT scans of a well-preserved

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

have allowed scientists to study internal structures and create a brain

endocast An endocast is the internal cast of a hollow object, often referring to the cranial vault in the study of brain development in humans and other organisms. Endocasts can be artificially made for examining the properties of a hollow, inaccessible sp ...

showing the surface features of the animal's brain. The

parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...

visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...

, and

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...

s of the

cerebrum The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In ...

were enlarged, indicating the marsupial lion had good senses of hearing, sight, and smell, as might be expected of an active predator. Also, a pair of blind canals within the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...

were probably associated with detecting

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

s as in the

Tasmanian devil The Tasmanian devil (''Sarcophilus harrisii'') (palawa kani: purinina) is a carnivorous marsupial of the family Dasyuridae. Until recently, it was only found on the island state of Tasmania, but it has been reintroduced to New South Wales in ...

. This indicates it most likely had seasonal mating habits and would "sniff out" a mate when in season.Thylacoleo "The Beast of the Nullarbor"
''

Catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

'', Western Australian Museum, Storyteller Media Group and ABC TV, 17 August 2006.

Feeding

The feeding behaviour of ''Thylacoleo'' remains a topic of academic debate, largely due the lack of any living analogue. While considered a powerful hunter, and a fierce predator, it has been theorized that due to its physiology ''Thylacoleo'' was, in fact, a slow runner, limiting its ability to chase prey. Analysis of its scapula suggests "walking and trotting, rather than climbing ... the pelvis similarly agrees with that of ambulators and cursors alkers and runners. These bones indicate that ''Thylacoleo'' was a slow to medium-paced runner, which is likely to mean it was an ambush predator. That fits with the stripes: camouflage of the kind one would need for stalking and hiding in a largely forested habitat (like tigers or leopards) rather than chasing across open spaces (like lions)." It may have functioned generally much like a larger analog of the

. New evidence also suggests that it may have been arboreal, and was at the very least capable of climbing trees. Incisions on bones of ''Macropus titan'', and the general morphology of ''Thylacoleo'' suggests that it fed in a similar manner to modern cheetahs, by using their sharp teeth to slice open the ribcage of their prey, thereby accessing the internal organs. They may have killed by using their front claws as either stabbing weapons or as a way to grab their prey with strangulation or suffocation.

Palaeoecology

Numerous fossil discoveries indicate the marsupial lion was distributed across much of the

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...

. A large proportion of its environment would have been similar to the southern third of Australia today,

semiarid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi- ...

, open scrub and

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

punctuated by

waterhole A waterhole is a depression in the ground in which water can collect, or a more permanent pool in the bed of an ephemeral river. Waterhole or water hole may refer to: * Water hole (radio), an especially quiet region of the electromagnetic spect ...

s and water courses. It would have coexisted with many of the so-called

Australian megafauna The term Australian megafauna refers to the megafauna in Australia during the Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, and the roles of human and climatic factors in their extinction are ...

such as ''Diprotodon'', giant kangaroos, and ''Megalania'', as well as giant

wallabies A wallaby () is a small or middle-sized macropod native to Australia and New Guinea, with introduced populations in New Zealand, Hawaii, the United Kingdom and other countries. They belong to the same taxonomic family as kangaroos and so ...

like ''

Protemnodon ''Protemnodon'' is an extinct genus of megafaunal macropodids that existed in Australia, Tasmania, and New Guinea in the Pliocene and Pleistocene. It is also called the giant kangaroo. Taxonomy Recent analysis of mtDNA extracted from fossils i ...

'', the giant

Phascolonus ''Phascolonus'' was a genus of prehistoric Australian marsupials in the wombat family. The largest species, ''Phascolonus gigas'', weighed as much as 200 kg (450 lb). ''Phascolonus'' existed alongside an even larger marsupial, ''Diprotodon'' ...

'', the giant snake ''

Wonambi ''Wonambi'' is an extinct genus of madtsoiid snakes that lived in late Neogene to late Quaternary Australia. Species of ''Wonambi'' were constrictor snakes unrelated to Australian pythons. Description ''Wonambi'' was a fairly large snake, ...

'', and the

thunderbird Thunderbird, thunder bird or thunderbirds may refer to: * Thunderbird (mythology), a legendary creature in certain North American indigenous peoples' history and culture * Ford Thunderbird, a car Birds * Dromornithidae, extinct flightless birds ...

Genyornis ''Genyornis newtoni'', also known as thunder bird and mihirung paringmal (meaning "giant bird"), is an extinct species of large, flightless bird that lived in Australia during the Pleistocene epoch until around 50,000 years ago. Over two met ...

''. ''T. hilli'' was a similar size to a contemporaneous thylacinid species, ''

Wakaleo alcootaensis ''Wakaleo alcootaensis'' was a species of marsupial lion of the genus ''Wakaleo'', that lived during the late Miocene, about 10 million years ago. Taxonomy The first description was given in an examination of material discovered at Alcoota in ...

'', and may have occupied habitat to the exclusion of that carnivore. Australia's

Pleistocene megafauna Pleistocene megafauna is the set of large animals that lived on Earth during the Pleistocene epoch. Pleistocene megafauna became extinct during the Quaternary extinction event resulting in substantial changes to ecosystems globally. The role of hu ...

would have been the prey for the agile ''T. carnifex'', who was especially

adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

for hunting large animals, but was not particularly suited to catching smaller prey. The relatively quick reduction in the numbers of its primary food source around 40,000 to 50,000 years ago probably led to the decline and eventual extinction of the marsupial lion. The arrival of

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s in Australia and the use of

fire-stick farming Fire-stick farming, also known as cultural burning and cool burning, is the practice of Aboriginal Australians regularly using fire to burn vegetation, which has been practised for thousands of years. There are a number of purposes for doing this ...

precipitated their decline. The extinction of ''T. carnifex'' makes

unique from the other continents because no substantial, apex mammalian predators have replaced the marsupial lions after their disappearance.

Extinction

It was believed that the extinction was due to the climate changes, but human activities as an extinction driver of the most recent species is possible yet unproven. There is a growing consensus that the extinction of the

megafauna In terrestrial zoology, the megafauna (from Greek μέγας ''megas'' "large" and New Latin ''fauna'' "animal life") comprises the large or giant animals of an area, habitat, or geological period, extinct and/or extant. The most common threshold ...

was caused by progressive drying starting about 700,000 years ago (700 ka). It is revealed recently that there was a major change in glacial-

interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...

cycles after ~450 ka. As for human involvement's contribution to the extinction, one argument is that the arrival of humans was coincident with the disappearance of all the extinct megafauna. This is supported by the claims that during MIS3, climatic conditions are relatively stable and no major climate change would cause the mass extinction of megafauna including ''Thylacoleo''. Although believed to have been a victim of climate change, some scientists now believe ''Thylacoleo'' to have been exterminated by humans altering the ecosystem with fire in addition to hunting its prey. "They found ''Sporormiella'' spores, which grow in herbivore dung, virtually disappeared around 41,000 years ago, a time when no known climate transformation was taking place. At the same time, the incidence of fire increased, as shown by a steep rise in charcoal fragments. It appears that humans, who arrived in Australia around this time, hunted the megafauna to extinction". Following the extinction of ''T. carnifex'', no other apex mammalian predators have taken its place.

Discoveries

The first specimens of ''Thylacoleo'' were collected in the early 1830s from the Wellington Valley region of New South Wales by Major (later Sir) Thomas Mitchell, however they were not recognised as ''Thylacoleo'' at the time. The species was first described by

in 1859, from a fragmentary specimen discovered by William Adeney near Lake Colungolac, near Camperdown in

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

In 2002, eight remarkably complete skeletons of ''T. carnifex'' were discovered in a limestone cave under

Nullarbor Plain The Nullarbor Plain ( ; Latin: feminine of , 'no', and , 'tree') is part of the area of flat, almost treeless, arid or semi-arid country of southern Australia, located on the Great Australian Bight coast with the Great Victoria Desert to its ...

, where the animals fell through a narrow opening in the plain above. Based on the placement of their skeletons, at least some survived the fall, only to die of thirst and starvation. In 2008, rock art depicting what is thought to be a ''Thylacoleo'' was discovered on the northwestern coast of the Kimberley. However, there is the possibility that the

thylacine The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct carnivorous marsupial that was native to the Australian mainland and the islands of Tasmania and New Guinea. The last known live animal was captured in 1930 in Tasman ...

, a related marsupial that also had a striped coat, may be the subject of the work, instead. The drawing represented only the second example of megafauna depicted by the indigenous inhabitants of Australia. The image contains details that would otherwise have remained only conjecture; the tail is depicted with a tufted tip, it has pointed ears rather than rounded, and the coat is striped. The prominence of the eye, a feature rarely shown in other animal images of the region, raises the possibility that the creature may have been a

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

hunter. In 2009, a second image was found that depicts a ''Thylacoleo'' interacting with a hunter who is in the act of spearing or fending the animal off with a multiple-barbed spear. Much smaller and less detailed than the 2008 find, it may depict a

, but the comparative size indicates a ''Thylacoleo'' is more likely, meaning that it is possible that ''Thylacoleo'' was extant until more recently than previously thought. In 2016,

trace fossils A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

in Tight Entrance Cave were identified as being the scratch marks of a ''Thylacoleo''.

Fossils

The first ''Thylacoleo'' fossil findings, discovered by Thomas Mitchell were found in the 1830s in the Wellington Valley of New South Wales, though not recognised as such at the time. The generic holotype, consisting of broken teeth, jaws, and a skull was discovered by a pastoralist, William Avery, near Lake Colungolac from which the species ''Thylacoleo carnifex'' was described by

. It was not until 1966 that the first nearly-complete skeleton was found. The only pieces missing were a foot and the tail. Currently, the

of West Australia remains to be the greatest finding site. These fossils now reside at the Australian Museum. It was reported that in 2012, an accumulation of vertebrate trace and body fossils were found in the Victorian Volcanic Plains in south-eastern Australia. It was determined that ''Thylacoleo'' was the only taxon that represented three divergent fossil records: skeletal, footprints, and bite marks. What this suggests is that these large carnivores had behavioral characteristics that could have increased their likelihood of their presence being detected within a fossil fauna. A characteristic seen in the remains of skull fragments is a set of carnassial teeth, suggesting the carnivorous habits of ''Thylacoleo''. Tooth fossils of the thylacoleo exhibit specific degrees of erosion that are credited to the utility of the carnassial teeth remains as they were used for hunting and consuming prey in a prehistoric Australia teeming with other megafauna. The specialisation found in the dental history of the marsupial indicates its status in the predatory hierarchy in which it existed.

References

External links

New study finds no evidence for theory humans wiped out megafauna

''Thylacoleo'' in Pleistocene Australia

Western Australian Museum: ''Thylacoleo'' - a voracious hunter

PLEDGE. N 1977, A NEW SPECIES OF ''THYLACOLEO'' (MARSUPIALIA: THYLACOLEONIDAE) WITH NOTES ON THE OCCURRENCES AND DISTRIBUTION OF THYLACOLEONIDAE IN SOUTH AUSTRALIA
{{Taxonbar, from=Q312099 Prehistoric vombatiforms Prehistoric mammals of Australia Pliocene marsupials Pleistocene marsupials Pleistocene genus extinctions Carnivorous marsupials Prehistoric marsupial genera Taxa named by Richard Owen Fossil taxa described in 1859 Apex predators