Nandinia (African palm civet)

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Nandinia binotata. Image credit: Mathias D’haen, under CC BY-NC 4.0.

Named by: Gray, 1843

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodontia, Cynodontia, Probainognathia, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Eutheria, Placentalia, Laurasiatheria, Ferae, Carnivoramorpha, Carnivora, Feliformia, Nandiniidae

Included species: Nandinia binotata

Viverrids (civets) are one of those groups of organisms that have experienced dramatic taxonomic revision in recent times. Particularly with the advent of molecular phylogenetics, many groups formerly considered viverrids have been booted out. These ex-civets include mongooses (more closely related to hyenas than to civets), Malagasy carnivorans such as the fossa (Cryptoprocta ferox) (also more closely related to hyenas), and linsangs (more closely related to cats).

One former viverrid, however, sits alone in the family tree of feliforms, the large clade of carnivorans that comprises all species more closely related to cats than to dogs, encompassing all of the groups mentioned in the previous paragraph. The single living species in the genus Nandinia is descended from a lineage that may have split from all other feliforms 40-50 million years ago and has no close living relatives. Despite this, it is still known by the vernacular names “African palm civet” and “two-spotted palm civet”.

feliforms
Phylogenetic tree of feliform relationships.

Nandinia may be phylogenetically lonely, but in many parts of their range they are considered the most abundant small carnivorans in the forests of central Africa. They are generally solitary, though this doesn’t mean that their lives are devoid of social interaction. The home range of a dominant male overlaps with those of several females and smaller males, and he communicates with the females in his range using a loud cry that can be heard up to almost 1 km (3280 ft) away. The smaller males, on the other hand, generally keep to their individual sectors within the larger range of the dominant male, a sensible choice given that conflicts between males are known to be fatal. Several individual Nandinia may gather in close proximity where food is abundant, such as groves of fruiting trees.

Fruit constitutes roughly 80% of the diet in Nandinia, and they assist in the seed dispersal of at least 12 different plant species. After feeding on fruit for 5-10 minutes at a time, Nandinia typically rest for about 2 hours on a tree branch a short distance away before returning to partake in another meal. Perhaps not coincidentally, the digestive system of Nandinia works quickly; it takes only 2-3 hours for consumed fruit to pass through the digestive tract. When more than one individual is feeding the same tree, females have priority access to food.

Their largely frugivorous habits should not be taken as a indicator of Nandinia lacking predatory prowess, however, considering that they are known to go after small primates such as pottos (Perodicticus potto) and juvenile monkeys. Nandinia dispatch their prey by holding it down with their forefeet while biting them all over the body. Their climbing skills serve them well when hunting; they have been observed catching fruit bats and raiding the nests of weaver birds at the tips of very thin branches.

The arboreal agility of Nandinia is facilitated by their large, ridged foot pads and a long, balancing tail. They are able to climb smooth posts, hang upside down by their feet, and descend trees headfirst. They can also jump across gaps 1 m (3.3 ft) wide and leap 1.8 m (5.9 ft) vertically into the air. One anecdotal account described an individual Nandinia repeatedly climbing to a height before apparently parachuting to the ground by extending its legs and tail. As one might expect, regular performance of such stunts can be risky. A wild specimen was once caught with healed fractures across its femur and kneecap.

Despite their acrobatics, it appears that Nandinia rarely venture higher than 40 m (131.2 ft) above the ground, preferring heights of 5-35 m (16.4-114.8 ft). During the day they rest on thick horizontal branches or tree hollows 12-15 m (39.4-49.2 ft) above ground. Unlike many other specialized arboreal mammals though, Nandinia display no aversion to traveling and foraging on the ground, and are regularly caught in traps set at ground level.

References

Albertonykus

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Thylacinus (Thylacines)

Thylacinus
Thylacinus cynocephalus individuals, photographed at the National Zoo, Washington, DC, ca. 1904. Image credit: Baker & Keller, public domain under US law.

Named by: Temminck, 1824

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodontia, Cynodontia, Probainognathia, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Metatheria, Marsupialia, Australidelphia, Dasyuromorphia, Thylacinidae

Included species: T. cynocephalus (type), T. macknessiT. megirianiT. potensT. rostralisT. yorkellus

Few mammals are more emblematic of extinction than the thylacine. The largest marsupial predator of modern times, this shy, nocturnal animal (also known as the Tasmanian wolf or Tasmanian tiger) was never numerous anywhere in its range, but it wasn’t always constrained to the island of Tasmania. At one point, thylacines could be found across Australia and New Guinea (which were joined in a landmass called Sahul before the end of the last ice age), but by around 2,000 years before the present, they had been completely extirpated from New Guinea and mainland Australia, and became constrained to the island whose name the species later bore. After almost 2,000 years of persecution by humankind and other stressors, the thylacine became even scarcer in its remaining Tasmanian range in the first four decades of the 20th century. The last known thylacine died in captivity in 1936, marking the end of this remarkable marsupial’s time on earth.

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A thylacine pictured in rock art at Ubirr, Northern Territory, Australia, >2,000 years old. Image credit: Original author unknown, photographed by Dave Pape, under CC BY 2.0.

Of course, this whole sorry saga is only a small part of the history of the thylacine and its relatives. Thylacinus cynocephalus was only the last of its family, which arose late in the Oligocene epoch and lasted for almost 30 million years before its extinction. Some of these extinct thylacine genera are worth discussing later, but there also existed extinct members of Thylacinus itself, which varied in some respects from the modern variety. Most noteworthy of these is the so-called “powerful thylacine”, T. potens, which is known from the Late Miocene Alcoota fauna of Northern Territory, Australia. A large, robust thylacine, it approximated a grey wolf in size and had a shorter snout. T. cynocephalus itself arose during the Pliocene and outlasted its relatives to become widespread, for a time, across the continent.

The modern thylacine was a medium-sized predator, a little bigger than a red fox. Males usually measured in at a direct length of around 1.63 meters (5.34 feet), and females at around 1.54 meters (5.05 feet). Males and females also possessed a degree of sexual dimorphism unusually high for marsupials in possessing different facial structures, with females tending to have shorter, more slender snouts. Notably, the thylacine was one of only two marsupial species known to have retained a pouch in males, which was repurposed as a sheath for the scrotal sac. In its more typical use, the female pouch, which (in another unusual twist) faced rearward, could bear up to four joeys (or “pups”), but typical litters were fewer than that, at two or three. Their fur was a sandy brown, with anywhere from 13 to 22 dark bands striping their haunches. There was a great deal of individual variation in these stripes, and no two thylacines would have had the same pattern. Museum specimens have even been matched to previously captive individuals on the basis of these stripes. In gross bauplan, they strongly resembled canids, despite having no close relation to them. They could be easily distinguished by, among other things, their significantly taller hindlimbs in proportion to their bodies, which gave them a strange, loping gait. The thylacine possessed the greatest mouth gape of any known modern mammal, and was capable of achieving as much as 80 degrees of jaw flexion during its “threat yawn” warning display.

Thylacines apparently bred year-round, with the peak breeding seasons in the spring and winter. They formed and hunted in family groups rather than packs, and seem to have opportunistically taken birds, lizards, small marsupials, and wallabies, but occasionally were adventurous enough to hunt eastern grey kangaroos. When in pursuit, they would move at a leisurely jog or canter rather than sprinting, and seem to have relied on superior stamina to outpace their prey. They also very occasionally preyed on domestic sheep and poultry, something which earned them the enmity of European settlers. Although indigenous Australians had occasionally poached thylacines for tens of thousands of years, the high-impact persecution of these settlers, whether government-led or private, led to the deaths of thousands of thylacines through the 19th and early 20th centuries. Hefty bounties for the animal would have driven the motivation for the killings just as much as any alleged predation upon livestock; at least one famous photo of a thylacine clutching a chicken in its mouth in fact comes from a sequence which, in context, shows it clearly being fed the bird in captivity. Habitat degradation caused by humankind and possible outbreaks of disease noted by trappers may have also contributed to the decline of this species. By the turn of the century, they were very rare, and the last thylacine shot in the country was in 1930; the last capture was of an individual posthumously named “Benjamin” in 1933, whereupon the male thylacine was transported to the Beaumaris Zoo, Hobart, where it lived for three years until dying, apparently of neglect. The death of “Benjamin” on 7 September 1936 also marks the last known human contact with this species, for from this point on, no confirmed sightings of this remarkable marsupial have been made. In 1982, it was declared extinct by the IUCN, and in 1986 by the government of Tasmania.

Thylacine-chicken
Staged photograph of a thylacine feeding upon a chicken, 1921. Image credit: Henry Burrell, public domain under Australian law.

Despite more than eighty years having passed since the death of the last known living individual, the thylacine has remained a darling of career and amateur cryptozoologists alike, and the possibility of its continued existence remains an article of serious public fascination. Surveys in 1938 turned up potentially credible scat and markings in the west of Tasmania, and alleged physical evidence has continued to surface in the decades since, not always convincingly. Some sightings and would-be photographic evidence have come from mainland Australia, but since the animal was not even known to exist there in the historical record, these must be regarded as improbable. If it really has persisted to the present, it would be in an incredibly small population deep in western Tasmania, since determined searches have turned up nothing conclusive and the projected population in the 1930s was that of only a few hundred individuals at most. Sadly, the fact that this marsupial predator is gone for good must be held as almost a certainty, and an object lesson in the effects of misinformed persecution against animal populations.

References

  • Australian Museum. The Thylacine. Accessed 16 December 2017.
  • Naturalworlds.org. The Thylacine Museum. Accessed 15 December 2017.
  • Paddle, R. 2000. The Last Tasmanian Tiger: The History and Extinction of the Thylacine. Cambridge University Press; Cambridge, UK. 273 pp.
  • Yates, A.M. 2014. New craniodental remains of Thylacinus potens (Dasyuromorphia: Thylacinidae), a carnivorous marsupial from the late Miocene Alcoota Local Fauna of central Australia. PeerJ 2: e547. 10.7717/peerj.547

—Valerie

Rhynchocyon (Giant sengis)

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Rhynchocyon petersi. Image credit: Joey Makalintal, under CC BY 2.0.

Named by: Peters, 1847

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodontia, Cynodontia, Probainognathia, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Eutheria, Placentalia, Afrotheria, Afroinsectiphilia, Macroscelidea, Macroscelididae

Included species: R. cirnei (type), R. chrysopygus, R. petersi, R. udzungwensis

Sengis are great. They are commonly known as “elephant shrews”, and it’s not hard to see why. Like shrews, they are small, mostly insectivorous mammals, and, like elephants, they have an elongated, mobile snout. However, prior to the rise of phylogenetic analysis incorporating molecular data, perhaps no one would have guessed that they are, in fact, more closely related to elephants than to shrews!

In terms of their size, the most elephantine sengis are members of the genus Rhynchocyon, hence their vernacular name of “giant sengis”. By “giant”, we mean up to 750 g (1.7 lb), slightly larger than a gray squirrel. These gargantuan sizes are attained by the most recently discovered species, R. udzungwensis, which was only scientifically described in 2008. Other species range between 300-700 g (0.7-1.5 lb).

Rhynchocyon live in the forests of Africa. They uncover invertebrates hiding under leaf litter by using their snout and long claws, and, like other sengis, capture prey with their tongue. Unusually among sengis, they don’t clear trails to use as runways within their home range. At night, they sleep in nests made from leaves on the forest floor. These nests lack a proper entrance; instead, the sengis enter simply by digging into them from one side. Unlike other sengis, which have highly precocial young that can run shortly after birth, juvenile Rhynchocyon stay in a nest for several weeks before they are old enough to forage.

Being active during the day, Rhynchocyon must remain on the lookout for a variety of predators, including birds of prey and chimpanzees. Sengis are highly specialized for rapid, almost antelope-like quadrupedal bounding, allowing them to escape from danger (at least much of the time). Rhynchocyon have been recorded reaching speeds of 27 km/h (17 mph). If a predator is detected before it gets close enough to be an immediate threat, R. chrysopygus are known to slap their tail against the ground while walking away, perhaps signalling to the predator that it has been spotted. R. chrysopygus are additionally notable for the golden patch of hair on their rump, which may divert predator attacks towards the thickened skin in this region and increase the sengis’ chances of escape. The rump shield also protects R. chrysopygus against bites from rivals.

Typical of most sengis, Rhynchocyon are socially monogamous, probably mating for life. Within their shared territory, each member of a mated pair drives off rivals of the same sex. However, mates don’t spend much time with each other and don’t even share the same nest at night. The adaptive function of monogamy in sengis is debated, because male sengis contribute little, if any, parental care of the young. In Rhynchocyon, it appears that the primary selective pressure for monogamy may be the high energetic cost that would be required for a male to defend multiple females from his competitors. Indeed, male Rhynchocyon will enter temporary polygynous relationships if the opportunity arises, usually when a female in a neighboring territory loses her mate.

References

—Albertonykus

Phataginus

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Phataginus tricuspis. Image credit: Николай Усик, under CC BY-SA 3.0.

Named by: Rafinesque, 1821

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodontia, Cynodontia, Probainognathia, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Eutheria, Placentalia, Laurasiatheria, Ferae, Pholidotamorpha, Pholidota, Manidae

Included species: P. tricuspis (type), P. tetradactyla

Pangolins are some of the most peculiar mammals. They are toothless, relying on their long, sticky tongue to capture insect prey. They are also covered in a coat of hard scales that serve as protection from predators. These unusual features may recall similarities with the anteaters and armadillos of South America. However, genetic studies have shown that the closest living relatives of pangolins are the carnivorans, the great radiation of predatory placental mammals including cats, dogs, bears, seals, and more.

Living pangolins are currently split into three different genera, of which the smallest are members of the genus Phataginus. Weighing around 2 kg (4.4 lb) as adults, Phataginus live in the forests of central Africa. Like other pangolins, they can roll into an armored ball to protect themselves from attack, but their scales are generally thinner and flimsier than those of larger pangolins. This, combined with their small size, likely makes them more vulnerable to predation, and they may rely more on their repulsive anal secretions to deter large carnivores.

P. tricuspis is the better-studied of the two species of Phataginus. Members of this species can retract their eyes into their sockets (an ability apparently shared by at least some other pangolin species). They regularly forage in trees and are able to climb quickly using a “caterpillar-like” motion. To get down from trees, they spiral around the tree trunk while supporting themselves using their tail. They have also been observed performing more expeditious descents by rolling into a ball before dropping directly to the ground.

Despite being at home in the trees, however, P. tricuspis spend much of their time on the ground, perhaps due to the greater availability of their preferred prey on the forest floor. While feeding, they flick their scales continuously to shake off attacking soldier ants and termites, and sweep their tail from side to side to herd their prey within reach. After feeding, they groom themselves meticulously using their hind feet to uncover any insects that may have ventured underneath their scales. During the day, P. tricuspis rest in tree cavities or in shallow burrows. They breed throughout the year; one field study rarely found females that were not pregnant.

Pangolins are typically solitary, but P. tricuspis exhibit behaviors suggestive of greater sociality in this species. Pairs have been found using the same tree hollows, and in captivity groups of up to six individuals have been observed sharing sleeping quarters and following one another around in single file. Juveniles in particular appear eager to seek contact with other pangolins and even their human handlers. One individual regularly returned to visit its handlers over a period of six months after being released into the wild. In general, P. tricuspis seem like a friendly bunch. However, males are known to fight to the death by slashing each other with their front claws. P. tricuspis have poor eyesight, so their social contacts are established using scent. They are also quite sensitive to vibrations, including sound.

Though most pangolins are competent climbers, members of the other species of Phataginus, P. tetradactyla, are particularly specialized for arboreal life. Their incredibly long, prehensile tail contains up to 47 vertebrae, more than that of any other mammal. The tail is strong enough to support their entire body weight for long periods, allowing them to hang by their tail. P. tetradactyla almost never descend to the ground. They rest in tree hollows or hollowed-out insect nests. Cavity-nesting birds are reportedly known to mob them, perhaps seeing them as competition for tree hollows.

P. tetradactyla are said to be more diurnal than P. tricuspis, which may reduce competition between the two species. It is likely that the highly arboreal habits of P. tetradactyla, along with their preference for forests that experience regular flooding, correspond to a specialization in feeding on ants and termites that avoid floods by nesting high in the forest canopy. Such insects tend to have well-developed chemical weaponry, so it is plausible that P. tetradactyla possesses adaptive countermeasures to these defenses. However, due to the lack of detailed study, such specializations, if present, remain unknown.

Reference

  • Kingdon, J. and M. Hoffmann (eds.). 2013. Mammals of Africa Volume V: Carnivores, Pangolins, Equids and Rhinoceroses. A&C Black Publishers Ltd., London. 560 pp.

—Albertonykus

Propithecus (Sifakas or Simponas)

Propithecus diadema. Image credit: Tom Junek, under CC BY-SA 3.0.

Named by: Bennett, 1832

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodonta, Cynodontia, Probainognatha, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Eutheria, Placentalia, Euarchontoglires, Archonta, Primates, Strepsirrhini, Lemuriformes, Lemuroidea, Indriidae

Included Species: P. diadema, P. edwardsi, P. candidus, P. perrieri, P. coquereli, P. verreauxi, P. deckenii, P. coronatus, and P. tattersalli

The name sifaka (pronounced: she-fak) is derived from the Malagasy language and is a reference to the sneeze-like call the animals make. The common name simpona is generally used by peoples in the eastern region of the island. Two species were originally recognized by primatologists: P. diadema (the Diademed Sifaka) and P. verreauxi (Verreaux’s Sifaka), containing a number of subspecies in each. In 1988 P. tattersalli (Golden-crowned Sifaka) was described by Elwyn L. Simons: a new species named after palaeoanthropologist Ian Tattersall. While aspects of the taxonomy behind some of the subspecies was questioned, this clade of three species was generally accepted until genetic studies during the middle of the 1990s more or less elevated all of the subspecies into species in their own right. Controversy still abounds as to the validity of these studies, but today nine species of sifakas are recognized.

Sifakas are found on Madagascar: throughout the western side of the island, with scattered eastern populations. They inhabit various forested regions, from evergreen and deciduous forests to rainforests and dry, semi-arid scrubland.

Generally large-bodied primates, sifakas exhibit a decent array of body-coloration. While one species is fully black-furred (P. perrieri) and few species have white-fur (e.g. P. candidus, P. deckenii, P. tattersalli), most have a blend of several colors on their heads, limbs, and chests. The color of the body actually varies based on the habitat that the animals reside: dark-bodied lemurs tend to live in warm, wet forests and light-bodied lemurs inhabit cooler, dry forests. The sifakas in the eastern regions of Madagascar also tend to be bigger in size than those elsewhere. The face is dark black/blue in color and devoid of hair across all species. The hindlimbs tend to be longer than the forelimbs and this is relevant to their modes of transportation.

Sifakas are famous for their curious hopping-motion when on the ground. Essentially bipedal, they use their legs to spring their bodies in a sideways motion – sometimes up to distances of 4 meters (~13 feet) – while the arms are raised for balance. When they are not on the ground, they move through the trees through vertical climbing and leaping, a strategy common among several lemur genera where the animal will grasp branches with their hands and propel themselves from tree-to-tree via their feet. Jumping up to 10 meter (~32 feet) spans, a sifaka will supplement these vast leaps by use of a fleshy-stretch of skin along the posterior and anterior regions of their arms. This ‘parachute’ allows the animal to slow their leaps when in descent and there has been rich discussion that these membranes may actually allow for gliding. Compared to other lemurs, the tail actually does not provide aid in balancing. When they are not moving through the trees or on the ground, resting lemurs will support themselves on trunks and branches by gripping the plants with their hindlimbs, pulling their hands and knees to their chests, and curling their tails between their legs. Sometimes during really hot days they will lean against the branches of trees and allow their legs to dangle downwards, giving them rather open comfort while resting.

These lemurs are strictly herbivorous. While leaves make up a substantial part of their diet, fruits and seeds are regularly taken. Sifakas have substantial bodily-adaptations towards the consumption of foliage: a large digestive tract with a swollen cecum permits the food to pass through the gut for a very long time to extract all the vital nutrients. The teeth are adapted too, with shearing crests on the molar teeth for ripping leaves. When feasting on seeds, sifakas will actually chew and grind up the grains – a high contrast to other seed-dispersing animals. As such, the feces almost never has full seeds enclosed inside. Other aspects of their diet include flower blossoms, tree bark, and even dirt (which aids in digestion). By having such an extensive digestion time, sifakas can spend much of their time at rest. Water is never directly consumed from streams, as all the liquid they need comes from tree bark and the cambium directly beneath it.

They are quite active during the day time and all species have been recorded engaging in activities during daylight hours, however a few regional populations of P. tattersalli will stay up at dusk during the wet season. Early in the morning, sifakas will group together and display their arms, chests, and stomachs towards the rising sun to allow for additional warmth. The rest of the day is devoted to feasting, resting, and social grooming, and there is a clear spike in activity in the late-afternoon/early-evening where the lemurs engage in rigorous leaping and climbing. On some occasions, they will descend to the ground to reach for fallen fruits.

Sifakas are social animals, forming relatively large multi-male and multi-female groups of roughly 12 individuals. That being said, groups are territorial and will defend their feeding areas and families with rigor. The consumption of fruits provides very high-energy that goes into the use of their scent-glands in their chins, which are used to mark their territories. Urine may also be used. Both methods go towards communication between groups. When confrontations do arise, sifaka groups will call to each other with a series of barks that are uttered in unison. The only exceptions are in P. tattersalli where multiple groups have been recorded living together without antagonistic interactions.

Female sifakas tend to remain in the groups to which they were born with for their entire lives. Males, on the other hand, always leave their groups and may relocate to others several times. This allows for females to mate with several males during the breeding season. Males have been recorded mounting other males as well, with one study recording 14% of the interactions as such. A single female is only receptive for a few hours and may engage in several mating systems, even in her own group. The only known instances of hybridization between sifakas of different species are between P. coronatus and P. deckenii.

After sex, a sifaka mother will remain in gestation for roughly four months. This results in the birth of a single eye-opened infant that will soon cling to the fur on her belly. The mother is very protective of the young from birth and the first few days of life for the infant are spent being licked and moved around the habitat with a wary manner. Fast forward to the thirty day-old baby which has now moved to a position clinging on the mother’s back. At this stage the sifaka is already able to move by itself and engage in some rudimentary jumping from branch to branch. It also practices walking bipedally, balancing with its arms held downward. From three months the sifaka is already playing excitedly with other members of its group. The mother will still cling to her baby until the 6-7 month mark, when the juvenile is clearly able to fend for itself, either staying in the group (if female) or leaving (if male). The adult age and size is not reached until much later, in one year since birth. Sexual maturity hits at two-and-a-half years and wild individuals have been recorded living for at least twenty years. Among sifakas, infant mortality is rather high: approximately 30-40% of young die within their first year of life.

Along with the trademark sneezing “she-fak” call and territorial growls, sifakas actually have their own unique vocalizations when dealing with predatory species. Fossa (Cryptoprocta ferox) and birds-of-prey are known hunters of this genus. When these are spotted by a member of the group, a sifaka will emit a loud ‘disturbance roar’ and sometimes raise their heads and drop from their perches while making said roars. Other common noises include low-frequency hums.

Sifakas have a low-quality fossil record and the oldest specimens attributed to the genus are 12,000 years old. However, phylogenetic studies place a divergence date from its closest living relatives at around 9.12-3.78 million years ago.

All species are at serious risk of extinction: the IUCN lists all nine species of sifakas as having declining populations in Madagascar. Four species are critically endangered while the rest are listed as endangered.

References:

  • Bagemihl, B., & Megahan, J. (2000). Biological Exuberance: Animal Homosexuality and Natural Diversity. New York: St. Martins Press.
  • Fossilworks.org. (2017). Fossilworks: Primonatalus prattae. [online] Available at: http://fossilworks.org/?a=taxonInfo&taxon_no=56186
  • Garbutt, N. and Garbutt, N. (2006). Guide to the Mammals of Madagascar. London: A. & C. Black.
  • Grzimek, B. and Fiedler, W. (1972). Grzimek’s Animal Life Encyclopedia: Mammals I. New York [etc.]: Van Nostrand Reinhold.
  • Ielc.libguides.com. (2017). LibGuides: Coquerel’s Sifaka (Propithecus coquereli) Fact Sheet: Taxonomy & History. [online] Available at: http://ielc.libguides.com/sdzg/factsheets/coquerels_sifaka/taxonomy
  • Iucnredlist.org. (2017). The IUCN Red List of Threatened Species. [online] Available at: http://www.iucnredlist.org
  • Mittermeier, R., Martinez-Vilalta, A., Rylands, A., Wilson, D., Nash, S., Hoyo, J., Copete, J. and Anandam, M. (2013). Handbook of the Mammals of the World: Primates. Barcelona: Lynx.
  • Mittermeier, R. and Nash, S. (2010). Lemurs of Madagascar. Arlington, Va: Conservation International.
  • Petter JJ, Desbordes F. (2013). Primates of the World: An Illustrated Guide. Princeton: Princeton University Press.
  • Redmond, I. (2008). The Primate Family Tree. Buffalo, N.Y.: Firefly Books.
  • Tetrapod Zoology. (2017). Literally, Flying Lemurs (and not Dermopterans). [online] Available at: http://scienceblogs.com/tetrapodzoology/2010/08/12/literally-flying-lemurs

—Joan

Psammomys (Sand rats)

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Psammomys obesus. Image credit: MinoZig, under CC BY-SA 4.0.

Named by: Cretzschmar, 1828

Taxonomy: Synapsida, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Theriodontia, Cynodontia, Probainognathia, Mammaliamorpha, Mammaliaformes, Mammalia, Theria, Eutheria, Placentalia, Euarchontoglires, Glires, Rodentia, Myomorpha, Muridae

Included species: P. obesus (type), P. vexillaris

Psammomys are a genus of large gerbils that live in arid regions of the Middle East and northern Africa. Of the two named species, P. vexillaris is known from only a handful of specimens, so most of what is written here pertains to the better-studied P. obesus.

A wide variety of rodents have become specialized to a desert-dwelling lifestyle. Many accordingly have physiological adaptations to help them survive in dry environments, such as the production of very small quantities of urine. Behavioral adaptations like nocturnality are also commonplace, allowing these rodents to avoid the heat of the day. Psammomys, however, urinate freely and are active in broad daylight. How do they manage this?

The answer lies in their diet. Psammomys specialize in feeding on saltbushes (e.g.: Atriplex), which can contain up to 82% water by weight and provide them with all the water they need. Such luxury does not come cheap, however. Saltbushes are eaten by no other rodent species, because, true to their name, they also contain high quantities of salt (12% by weight). Psammomys get rid of excess salt by peeing large amounts of urine (25 mL/day). The urine is highly-concentrated (i.e.: pasty) to reduce water loss, making it, on average, four times saltier than the sea!

Psammomys are generally solitary in their individual burrows, but will often live in close association with one another, forming colonies. The burrows can be quite complex, reaching up to 50 cm (19.7 in) beneath the ground and having 5-15 entrances. A typical colony has a burrow under every saltbush in the vicinity, with trails connecting separate burrows and food plants. While foraging, Psammomys cut off small branches from saltbushes and carry them back to their burrow entrance to eat. As such, active burrows can be recognized by the presence of discarded piles of saltbush fragments near the entrance. Over time, colonies shift from one part of their range to another as the Psammomys deplete one patch of saltbushes and move on to the next.

Due to their specialized low-calorie, vegetation-based diet, Psammomys readily develop diabetes and obesity in captivity if fed the grain-based diet of most small rodents, making them model organisms in medical research.

References

  • Happold, D.C.D. (ed.). 2013. Mammals of Africa Volume III: Rodents, Hares and Rabbits. A&C Black Publishers Ltd., London. 784 pp.
  • Kaiser, N., E. Cerasi, and G. Leibowitz. 2012. Diet-induced diabetes in the sand rat (Psammomys obesus). Pp. 89-102, in H.G. Joost, H. Al-Hasani, and A. Schürmann (eds.), Animal Models in Diabetes Research. Methods in Molecular Biology 933. Humana Press; Totowa, NJ.

—Albertonykus