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The fossil record of early primates is largely comprised of dentitions. While teeth can indicate phylogenetic relationships and dietary preferences, they say little about hypotheses pertaining to the positional behavior or substrate preference of the ancestral crown primate. Here we report the discovery of a talus bone of the dentally primitive fossil euprimate Donrussellia provincialis. Our comparisons and analyses indicate that this talus is more primitive than that of other euprimates. It lacks features exclusive to strepsirrhines, like a large medial tibial facet and a sloping fibular facet. It also lacks the medially positioned flexor-fibularis groove of extant haplorhines. In these respects, the talus of D. provincialis comes surprisingly close to that of the pen-tailed treeshrew, Ptilocercus lowii, and extinct plesiadapiforms for which tali are known. However, it differs from P. lowii and is more like other early euprimates in exhibiting an expanded posterior trochlear shelf and deep talar body. In overall form, the bone approximates more leaping reliant euprimates. The phylogenetically basal signal from the new fossil is confirmed with cladistic analyses of two different character matrices, which place D. provincialis as the most basal strepsirrhine when the new tarsal data are included. Interpreting our results in the context of other recent discoveries, we conclude that the lineage leading to the ancestral euprimate had already become somewhat leaping specialized, while certain specializations for the small branch niche came after crown primates began to radiate.

The ecology, and particularly the diet, of treeshrews (order Scandentia) is poorly understood compared to that of their close relatives, the primates. This stems partially from treeshrews having fast food transit times through the gut, meaning fecal and stomach samples only represent a small portion of the foodstuffs consumed in a given day. Moreover, treeshrews are difficult to observe in the wild, leading to a lack of observational data in the literature. Although treeshrews are mixed feeders, consuming both insects and fruit, it is currently unknown how the relative importance of these food types varies across Scandentia. Previous study of functional dental morphology has provided an alternative means for understanding the diet of living euarchontans. We used dental topographic metrics to quantify aspects of functional dental morphology in a large sample of treeshrews (n = 58). We measured relief index, Dirichlet normal energy, and three-dimensional orientation patch count rotated, which quantify crown relief, occlusal curvature, and complexity, respectively. Our results suggest that treeshrews exhibit dental morphology consistent with high levels of insectivory relative to other euarchontans. They also suggest that taxa such as Dendrogale melanura and Tupaia belangeri appear to be best suited to insectivory, whereas taxa such as T. palawanensis and T. gracilis appear to be best adapted to frugivory. Our results suggest that Ptilocercus lowii is characterized by a dentition better adapted to insectivory than the early primate Purgatorius. If P. lowii represents a good modern analogue for primitive euarchontans, this contrast would support models of primate origins that include a shift to greater frugivory.

The ethmoidal region of the skull houses one of the most important sense organs of mammals, the sense of smell. Investigation of the ontogeny and comparative anatomy of internal nasal structures of the macrosmatic order Scandentia is a significant contribution to the understanding of the morphotype of Scandentia with potential implications for our understanding of the primate nasal morphological pattern. For the first time perinatal and adult stages of Ptilocercus lowii and selected Tupaia species were investigated by serial histological sections and high-resolution computed tomography (μCT), respectively. Scandentia show a very common olfactory turbinal pattern of small mammals in having two frontoturbinals, three ethmoturbinals, and one interturbinal between the first and second ethmoturbinal. This indicates a moderately developed sense of smell (moderately macrosmatic). The observed septoturbinal is probably an apomorphic character of Scandentia. A general growth in length occurs during postnatal ontogeny; thus the adult ethmoidal region is proportionally longer compared to the rest of the skull. Throughout ontogeny Ptilocercus has a proportionally longer nasal cavity than Tupaia. Major differences exist between Ptilocercus and Tupaia in regard to the proportions of the nasal cavity which correlate with the position of the orbits. Compared to Tupaia, Ptilocercus shows more anteriorly oriented orbits and has a proportionally longer nasal capsule than Tupaia and based on anatomy probably a higher level of olfactory discrimination. Furthermore, Ptilocercus has a platybasic skull base that resembles a derived feature of Ptilocercidae. In contrast, Tupaia has a distinct septum interorbitale leading to a tropibasic skull, a pattern that is a plesiomorphic character of Tupaiidae and Scandentia in general. This finding helps us to understand the septum interorbitale pattern in Primates. Our results indicate that differences among the investigated Scandentia species are correlated with adaptations to foraging and behavioural biology.

Pen-tailed Treeshrew Ptilocercus lowii French: Ptilocerque de Low / German: Federschwanz-Spitzhérnchen / Spanish: Musarana arboricola de cola plumosa Other common names: Feathertailed Treeshrew, Low's Treeshrew Taxonomy. Plilocercus lowii Gray, 1848, Kuching, Sarawak, Borneo, Malaysia. Two subspecies are recognized. Subspecies and Distribution. P. l. lowii Gray, 1848 — Borneo and offshore Labuan I. P. l. continentis Thomas, 1910 — Malay Peninsula (from extreme S Thailand to; the S tip). The Pen-tailed Treeshrew occurs also on Serasan (South Natuna Is), Sumatra and several associated islands such as Pini and Tanahbala (Batu Is), Siberut (Mentawai Is), Kundur (Riau Is), Lingga, and Bangka, but subspecies involved are not known. Descriptive notes. Head-body 130-150 mm, tail 160-200 mm, ear c.17 mm, hindfoot c.26 mm; weight 50-60 g. The Pen-tailed Treeshrew is the most distinct treeshrew, with large round black eyes, gray dorsal fur, and ivory/white ventral surfaces. Tail is scaled, long, and mouse-like, with distinct feathering beginning about halfway down its length, black feathering at the proximate end, and white fur at the distal end. Ears are large and mouse-like. Eyes have black mask around them; eye shine is silver-colored, making it easily distinguishable when illuminated with a flashlight. Muzzle is thin and pointed, with pink skin around nose and whiskers. Subspecies continentis has wider black stripe on face. The Pen-tailed Treeshrew is adapted for an arboreal lifestyle, with curved claws, broad and strong limbs, and tail used for balance. Face is short, with premolars in lateral contact with enlarged temporal muscles;it is assumed to have the strongest bite force of all treeshrews. Habitat. Most commonly lowland primary tropical rainforests, but sometimes secondary forests and gardens, up to elevations of ¢.1200 m. The Pen-tailed Treeshrew ap- pears to be dependent on large dipterocarp trees for nest sites. Food and Feeding. The Pen-tailed Treeshrew is known to forage on insects and fruit. It eats fermented nectar from bertam palm (Fugeissona, Arecaceae), but individuals do not seem to be affected by the alcohol. It forages at night for insects on tree trunks, ranging from near the forest floor to high in the canopy. It very rarely spends time foraging on foliage, almost exclusively on trunks of trees. It has been caught in traps with bananas, but feces indicate that fruit is only a sporadic part of the diet. Breeding. Specific behaviors of the Pen-tailed Treeshrew are unknown; however, nests are large (c.60 cm in length) and constructed of fibers and leaves inside hollow trees. Nests are thought to occur in large trees with natural cavities and multiple entrances. Seasonality of breeding is unknown. Unlike species of Tupaiidae, Pentailed Treeshrews are not believed to practice absentee parental care because nests are shared by mothers and offspring. Litters likely consist of two offspring, but data are limited. Activity patterns. The Pen-tailed Treeshrew is typically considered strictly arboreal, but it occasionally visits the forest floor where it has been trapped. It is the only nocturnal treeshrew; it emerges shortly after sunset and returnsto its nest around dawn. Movements, Home range and Social organization. Pen-tailed Treeshrews are known to use communal tree nests with up to five individuals, probably related family groups. They appear to forage alone, but all individuals that share a nest seem to disperse and return to the nest simultaneously. Shared nest sites might assist with metabolic demands. Individuals make bird-like chirps when leaving a shared nest. Home ranges of adults are not well characterized but likely encompass c.6 ha. Although the home range might seem small, vertical habitat is vast in lowland dipterocarp forests, giving individuals large amounts of vertical foraging space. Movements occur on trunks of trees, with little use offoliage. Pen-tailed Treeshrews do not make large leaps between trees but walk along branches in contact with nearby trees. Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. In most forests, Pen-tailed Treeshrews are thought to be rare, with relict distributions. Based on observations from L. H. Emmons in 2000, they are thought to be common only in Danum Valley, Sabah, Malaysia. Additional studies are necessary to better understand the natural history and conservation needs of the Pen-tailed Treeshrew. Bibliography. Butler (1972), Corbet & Hill (1992), Dunn et al. (1968), Emmons (2000), Gray (1848), Gregory (1910), Helgen (2005), Huxley (1872), Li Qiang & Ni Xijun (2016), Lim (1967a), Lyon (1913), Mason et al. (2016), McKenna (1966, 1975), Muul & Lim (1971), O'Leary et al. (2013), Roberts et al. (2011), Sargis (2002a, 2002b), Szalay (1977), Van Valen (1965), Wagner (1855), Whittow & Gould (1976), Wiens et al. (2008), Zeller (1986)., Published as part of Russell A. Mittermeier & Don E. Wilson, 2018, Ptilocercidae, pp. 236-241 in Handbook of the Mammals of the World – Volume 8 Insectivores, Sloths and Colugos, Barcelona :Lynx Edicions on page 241, DOI: 10.5281/zenodo.6656870

Debate on the adaptive origins of primates has long focused on the functional ecology of the primate visual system. For example, it is hypothesized that variable expression of short- (SWS1) and middle-to-long-wavelength sensitive (M/LWS) opsins, which confer color vision, can be used to infer ancestral activity patterns and therefore selective ecological pressures. A problem with this approach is that opsin gene variation is incompletely known in the grandorder Euarchonta, that is, the orders Scandentia (treeshrews), Dermoptera (colugos), and Primates. The ancestral state of primate color vision is therefore uncertain. Here, we report on the genes (OPN1SW and OPN1LW) that encode SWS1 and M/LWS opsins in seven species of treeshrew, including the sole nocturnal scandentian Ptilocercus lowii. In addition, we examined the opsin genes of the Central American woolly opossum (Caluromys derbianus), an enduring ecological analogue in the debate on primate origins. Our results indicate: 1) retention of ultraviolet (UV) visual sensitivity in C. derbianus and a shift from UV to blue spectral sensitivities at the base of Euarchonta; 2) ancient pseudogenization of OPN1SW in the ancestors of P. lowii, but a signature of purifying selection in those of C. derbianus; and, 3) the absence of OPN1LW polymorphism among diurnal treeshrews. These findings suggest functional variation in the color vision of nocturnal mammals and a distinctive visual ecology of early primates, perhaps one that demanded greater spatial resolution under light levels that could support cone-mediated color discrimination.

Skull anatomy other than the ear region of the pen-tailed treeshrew, Ptilocercus lowii Gray, 1848 (Ptilocercidae), is described and illustrated in detail based on 11 specimens from the Carnegie Museum of Natural History and the United States National Museum. Comparisons are made to the common treeshrew, Tupaia glis (Diard, 1820) (Tupaiidae), in a manner similar to the author's treatment of the ear region (Wible 2009). Included are bone by bone treatment of the external surfaces of the skull and hyoid apparatus, and composite treatment of the endocranium for P. lowii with comparisons to an uncertain species of Tupaia Raffles, 1821, and T. glis. The principal cranial foramina and their contents are addressed. Treeshrews are members of the placental order Scandentia, which is nested within the higher-level clade Euarchonta, along with the order Primates and the order Dermoptera (colugos). Relationships among these three orders are controversial in recent molecular studies, and detailed morphological...

The ear region of the pen-tailed treeshrew, Ptilocercus lowii Gray, 1848 (Scandentia, Ptilocercidae), is described and illustrated in detail based on five museum specimens from the National Museum of Natural History, two with the auditory bulla removed exposing the intratympanic surfaces. Soft tissues (arteries, veins, nerves, and muscles) are reconstructed onto the adult skulls based on published reports of these elements in a fetal P. lowii. Comparisons are made with four specimens of the common treeshrew, the tupaiid Tupaia glis (Diard, 1820), from the Carnegie Museum of Natural History, including one with the auditory bulla removed.

For humans alcohol consumption often has devastating consequences. Wild mammals may also be behaviorally and physiologically challenged by alcohol in their food. Here, we provide a detailed account of chronic alcohol intake by mammals as part of a coevolved relationship with a plant. We discovered that seven mammalian species in a West Malaysian rainforest consume alcoholic nectar daily from flower buds of the bertam palm ( Eugeissona tristis ), which they pollinate. The 3.8% maximum alcohol concentration (mean: 0.6%; median: 0.5%) that we recorded is among the highest ever reported in a natural food. Nectar high in alcohol is facilitated by specialized flower buds that harbor a fermenting yeast community, including several species new to science. Pentailed treeshrews ( Ptilocercus lowii ) frequently consume alcohol doses from the inflorescences that would intoxicate humans. Yet, the flower-visiting mammals showed no signs of intoxication. Analysis of an alcohol metabolite (ethyl glucuronide) in their hair yielded concentrations higher than those in humans with similarly high alcohol intake. The pentailed treeshrew is considered a living model for extinct mammals representing the stock from which all extinct and living treeshrews and primates radiated. Therefore, we hypothesize that moderate to high alcohol intake was present early on in the evolution of these closely related lineages. It is yet unclear to what extent treeshrews benefit from ingested alcohol per se and how they mitigate the risk of continuous high blood alcohol concentrations.

Treeshrews are widely considered a “living model” of an ancestral primate and have long been called “living fossils”. Actual fossils of treeshrews, however, are extremely rare. We report a new fossil species of Ptilocercus treeshrew recovered from the early Oligocene (~34 Ma) of China that represents the oldest definitive fossil record of the crown group of treeshrews and nearly doubles the temporal length of their fossil record. The fossil species is strikingly similar to the living Ptilocercus lowii, a species generally recognized as the most plesiomorphic extant treeshrew. It demonstrates that Ptilocercus treeshrews have undergone little evolutionary change in their morphology since the early Oligocene. Morphological comparisons and phylogenetic analysis support the long-standing idea that Ptilocercus treeshrews are morphologically conservative and have probably retained many characters present in the common stock that gave rise to archontans, which include primates, flying lemurs, plesiadapiforms and treeshrews. This discovery provides an exceptional example of slow morphological evolution in a mammalian group over a period of 34 million years. The persistent and stable tropical environment in Southeast Asia through the Cenozoic likely played a critical role in the survival of such a morphologically conservative lineage.

Skull size and shape were examined among 14 species of the tree shrews (Tupaia montana, T. picta, T. splendidula, T. mulleri, T. longipes, T. glis, T. javanica, T. minor, T. gracilis, T. dorsalis, T. tana, Dendrogale melanura, D. murina, and Ptilocercus lowii). The bones of face were rostro-caudally longer in T. tana and T. dorsalis, contrasting with T. minor and T. gracilis, D. melanura, D. murina and P. lowii which have smaller facial length ratios. The arbo-terrestrial species (T. longipes and T. glis) were similar to terrestrial species in length ratios of bones of face unlike the other arbo-terrestrial species (T. montana, T. picta, T. splendidula, and T. mulleri). We propose that T. longipes and T. glis have adapted to foraging for termites and ants as have T. tana and T. dorsalis. Additionally small body size in T. javanica may be the result of being isolated in Java. We separated the species into 5 groups from the measurment values of skulls: 1) Terrestrial species; T. tana and T. dorsalis, 2) Arboreal species; T. minor and T. gracilis, 3) Arbo-terrestrial species group 1: T. montana, T. splendidula, T. picta and T. mulleri, and T. javanica, 4) Arbo-terrestrial species group 2: T. glis and T. longipes, 5) Arboreal species of Dendrogale and Ptilocercus. Principal component analysis separated species into 8 clusters as follows: 1) T. tana, 2) T. dorsalis, 3) T. montana, T. splendidula, T. picta and T. mulleri, 4) T. glis and T. longipes, 5) T. javanica, 6) T. minor and T. gracilis, 7) D. melanura and D. murina, and 8) P. lowii. We suggest that these clusters correspond to behavioral strategies and peculiarities observed in foraging, feeding and locomotion in each species.

The chapter includes three subchapters—Skeleton, Joints and Musculature, which describe, respectively, osteology, syndesmology and myology of the shoulder girdle and forelimb in Tupaia belangeri, one of the most generalized members of the order Scandentia. The original myological data are compared with those published by Le Gros Clark, Davis, Miller, Verma, George, Sargis, etc. on the other tree shrews, namely, Dendrogale murina, Ptilocercus lowii, Tupaia glis, Tupaia minor, Tupaia nicobarica, Tupaia tana and Urogale evereti. The description is supplied with 52 original illustrations—45 black-and-white drawings of myological dissections, 6 grayscale and 1 coloured photos of the skeleton.

The eutherian orders Scandentia, Primates, Dermoptera, and Chiroptera have been grouped together by many morphologists, using various methods and data sets, into the cohort Archonta. Molecular evidence, however, has supported a clade (called Euarchonta) that includes Scandentia, Primates, and Dermoptera, but not Chiroptera. Within Archonta, some systematists have grouped Dermoptera and Chiroptera in Volitantia, while others have grouped Dermoptera and Primates in Primatomorpha. The order Scandentia includes the single family Tupaiidae, with two subfamilies, Ptilocercinae and Tupaiinae. Ptilocercinae is represented only by Ptilocercus lowii, which has been said to be the taxon most closely approximating the ancestral tupaiid. However, most researchers working on archontan phylogeny typically do not treat the order Scandentia as being polymorphic. They usually use Tupaia to represent Scandentia, despite the fact that Ptilocercus is quite distinct from Tupaia and has been argued to be the more plesiomorphic of the two taxa. In this study, a character analysis was performed on postcranial features that have been used to support the competing Primatomorpha and Volitantia hypotheses. In recognition of the polymorphic nature of Scandentia, taxonomic sampling within Scandentia was increased to include Ptilocercus. The postcranium of Ptilocercus was compared to that of tupaiines, euprimates, plesiadapiforms, dermopterans, and chiropterans. Several character states used to support either Primatomorpha or Volitantia, while not found in Tupaia, were found in Ptilocercus. While these features may have evolved independently in Ptilocercus, it is perhaps more likely that they represent features that first evolved in the ancestral archontan and were then lost in one of the extant orders. This character analysis greatly reduces the supportive evidence for the Primatomorpha hypothesis.

The grasping behaviour, locomotion and substrate use of the tree shrews Tupaia minor and T. tana were investigated in the Department of Zoological Research at the National Zoological Park in Washington, DC. Seven arboreal T. minor and five terrestrial T. tana were observed and videotaped for 10-min focal animal samples totalling 77 h of observation. Locomotion and substrate use were scored and images of grasping behaviour were captured from videotapes. Tupaia minor individuals were videotaped crossing dowels and the number of dowel crossings that included grasps were scored. In 84% of dowel crossings, T. minor individuals used either their hallux or their pollex to grasp the dowels. Tupaia minor was also more active, moved more quickly, was more arboreal, rooted less, reversed its feet more, flexed its forelimbs more and was more semi-plantigrade than T. tana . It is proposed that arboreal tupaiids, such as Ptilocercus lowii and T. minor , may represent better models for early primates than didelphid marsupials because they are capable of grasping and are more closely related to primates.

A full understanding of primate morphological and genomic evolution requires the identification of their closest living relative. In order to resolve the ancestral relationships among primates and their closest relatives, we searched multispecies genome alignments for phylogenetically informative rare genomic changes within the superordinal group Euarchonta, which includes the orders Primates, Dermoptera (colugos), and Scandentia (treeshrews). We also constructed phylogenetic trees from 14 kilobases of nuclear genes for representatives from most major primate lineages, both extant colugos, and multiple treeshrews, including the pentail treeshrew, Ptilocercus lowii , the only living member of the family Ptilocercidae. A relaxed molecular clock analysis including Ptilocercus suggests that treeshrews arose approximately 63 million years ago. Our data show that colugos are the closest living relatives of primates and indicate that their divergence occurred in the Cretaceous.

Mammalian Evolution![Figure][1] Pen-tailed tree shrew gives us a glimpse of one of our earliest ancestors PHOTO: JOSEPH WOLF, PROCEEDINGS OF THE ZOOLOGICAL SOCIETY OF LONDON Tree shrews are often held up as being living fossils, presumably very similar to our own earliest primate ancestor. The dearth of actual fossils of these small tropical mammals, however, has meant that much of this conclusion has been speculative. Li and Ni describe a new fossil tree shrew that is exceedingly similar to the extant pen-tailed tree shrew ( Ptilocercus lowii ), yet twice as old as any previously described sister taxa. The fossil suggests that this tree shrew has gone nearly unchanged since the Oligocene (over 34 million years ago). Further, it supports the suggestion that the extant P. lowii gives us a living glimpse of the first ancestor of the Archonta, our own superordinal group. Sci. Rep. 10.1038/srep18627 (2016). [1]: pending:yes

This paper presents results of historical data (1968–1974) of small mammals trapping, mist netting of bats, and direct observations in the Pasoh Forest Reserve (Pasoh FR). Eighty-five mammalian species belonging to 8 orders from 24 families has been catalogued. Of these, 8 species of fruit bats and 21 species of insectivorous bats were netted. Among the insectivorous bats, four species are of significant findings. These are Myotis ridleyi, Pipistrellus stenopterus, Murina cylotes and Phoniscus atrox, which are new localities records for Pasoh FR. The remaining 56 species comprised small mammals (insectivores, tree shrews, rodents, primate, carnivores and herbivores). Among the mammals, two species, Pithecheir parvus and Ptilocercus lowii are also new locality records for Pasoh FR. An additional of 27 species were recorded in later studies by Kemper (1988) and Francis (1990) that were not recorded in our study made up a total of 112 species altogether, thus far recorded for Pasoh FR. This represents 56% of the total mammalian fauna in Peninsular Malaysia. There is a marked difference in the species diversity between primary forest (PF) and regenerating forest (RF). Of the 85 species recorded in Pasoh, 46 species were found in RF compared to 78 in PF. The higher number of species diversity reported in PF was reflected by more efforts made in PF as opposed to RF. This study is far from conclusive, nevertheless results revealed sign of mammalian fauna recovering in the regenerating forest if left alone without further disturbance.

In this study, the forelimb of 12 species of tupaiids was analyzed functionally and compared to that of other archontan mammals. Several differences that relate to differential substrate use were found in the forelimb morphology of tupaiids. These differences included shape of the scapula, length and orientation of the coracoid process, size of the lesser tuberosity, shape of the capitulum, length of the olecranon process, and shape of the radial head and central fossa. The forelimb of the arboreal Ptilocercus lowii, the only ptilocercine, is better adapted for arboreal locomotion, while that of tupaiines is better adapted for terrestrial (or scansorial) locomotion. While the forelimb of the arboreal Ptilocercus appears to be habitually flexed and exhibits more mobility in its joints, a necessity for movement on uneven, discontinuous arboreal supports, all tupaiines are characterized by more extended forelimbs and less mobility in their joints. These restricted joints limit movements more to the parasagittal plane, which increases the efficiency of locomotion on a more even and continuous surface like the ground. Even the most arboreal tupaiines remain similar to their terrestrial relatives in their forelimb morphology, which probably reflects the terrestrial ancestry of Tupaiinae (but not Tupaiidae). The forelimb of Urogale everetti is unique among tupaiines in that it exhibits adaptations for scratch-digging. Several features of the tupaiid forelimb reflect the arboreal ancestry of Tupaiidae and it is proposed that the ancestral tupaiid was arboreal like Ptilocercus. Also, compared to the forelimb character states of tupaiines, those of Ptilocercus are more similar to those of other archontans and it is proposed that the attributes of the forelimb of Ptilocercus are primitive for the Tupaiidae. Hence, Ptilocercus should be considered in any phylogenetic analysis that includes Scandentia.

Ptilocercus lowii Gray, 1848. Proc. Zool. Soc. Lond., 1848:24. TYPE LOCALITY: Malaysia, Sarawak, "caught in the Rajah's house", i.e. Kuching. DISTRIBUTION: S peninsular Thailand; peninsular Malaysia; Sumatra, Riau Isis, Batu Isis, Banka, and Serasan Isl (Indonesia); Borneo; Labuan Isl (Malaysia). SYNONYMS: continentis., Published as part of Don E. Wilson, 1993, Order Scandentia, pp. 131-133 in Mammal Species of the World (2 nd Edition), Washington and London :Smithsonian Institution Press on page 133, DOI: 10.5281/zenodo.7353126

The structure of the tympanic region of the skull of Ptilocercus lowii was studied in an embryo of 30 mm crown-rump length and in 5 osteocrania. As in Tupaia, the anterior wall of the bulla of Ptilocercus is not completed by a tympanic process of the alisphenoid, contrary to earlier reports. Ptilocercus resembles Tupaia in the following derived characters. The ventral wall of the tympanic cavity is formed by a rostral entotympanic and by a caudal tympanic process of the petrosal. The entotympanic develops in primary connection with the tubal cartilage. The tympanic aperture of the auditory tube is bordered by the entotympanic. The ring-shaped tympanicum is covered by the entotympanicum and is aphaneric. The musculus tensor tympani is lacking. Among mammals, these characters can be regarded as synapomorphic for the Tupaiidae, that is, to have been present in the common ancestor of the two subfamilies. From the evidence of the tympanic region, the Tupaiidae, therefore, form a monophyletic group. Besides these synapomorphies, there are remarkable differences between Ptilocercus and Tupaia in the structure of the bulla. In Ptilocercus the bulla is smaller and less pneumatized than in Tupaia. An anterior intrabullar septum, present in Tupaia, is lacking in Ptilocercus. The epitympanic wing of the alisphenoid is smaller in Ptilocercus than in Tupaia. A lateral prefacial commissure of the tegmen tympani is present in Ptilocercus, but absent in Tupaia. The caudal tympanic process of the petrosal is larger in Ptilocercus than in Tupaia. These characters are autapomorphic for the Ptilocercinae and for the Tupaiinae, respectively. They demonstrate that the auditory bulla of Ptilocercus and that of Tupaia have evolved independently to a considerable extent. An early phylogenetic separation of their respective ancestors seems likely. The tympanic region of the skull provides no evidence for close relationships of the tree shrews to the primates or to any other eutherians. The classification of the Tupaiidae in a separate order, Scandentia, is supported.

Introduction When my friend Mr. C. W. Beebe was in Borneo he made persistent efforts to secure for me specimens of the rare pen-tailed tree-shrew (Ptilocercus lowii). Failing in this, he obtained the loan of a skin and skeleton of this animal from the Rajah of Sarawak, and these he has very kindly intrusted to me for study and description. Ptilocercus and its ally, Tupaia, together constituting the family Tupaiidse of the suborder Menotyphla, are of peculiar interest, because they appear to bridge over to some extent the gap that separates Insectivores from Primates. They are arboreal in habit, and Tupaia is said to be lively, active, and squirrel-like, both in appearance and in habit. Certain anatomical resemblances shown by Tupaia to the Lemurs have been noted from time to time by various authors, but until recently the Tupaiids have been studied far less thoroughly than other families of Insectivores. . . .

Examination of the endoparasites and stomach contents of Moonrats and Pentail treeshrews helps to establish certain facts as to the behaviour and food preference in their natural environment. Earthworms and arthropods are the main diet of Moonrats in the wild, with fish, crabs and land molluscs as supplementary food. In captivity, this animal fed primarily on fresh fish. The Pentail tree-shrews, on the other hand are more insectivorous although meat is occasionally eaten. This animal apparently is not strictly a canopydweller as was previously believed. The stomach contents, and the fact that some specimens were trapped on the forest floor indicates that they may often descend to ground level.

The tree shrews (family Tupaiidae) of Southeast Asia are small, scansorial, squirrel-like mammals which occupy a range of arboreal, semi-arboreal, and forest floor niches. They are insectivorous/omnivorous and predominantly diurnal, although one species (Ptilocercus lowii) is crepuscular or nocturnal. The only monographic description of all genera and species of the family was that by Lyon (1913). Most taxonomists have accepted Lyon’s subdivision of Tupaiidae into two subfamilies: (1) the diurnal subfamily Tupaiinae, containing five genera (Tupaia, Anathana, Dendrogale, Lyonogale, and Urogale); and (2) the crepuscular (or nocturnal) subfamily Ptilocercinae, containing the single genus Ptilocercus. The geographic distribution of the family extends from India to the Philippines, and from southern China to Java, Borneo, Sumatra, and Bali, including the many islands within this region. This distribution corresponds closely with the limits of the Zoogeographic Oriental Region.

Ptilocercus lowii Gray, 1848. Proc. Zool. Soc. Lond., 1848:24. TYPE LOCALITY: Malaysia, Sarawak, "caught in the Rajah's house", i.e., Kuching. DISTRIBUTION: Southern peninsular Thailand, peninsular Malaysia, Sumatra, including Riau Isis, and Batu Isis., Banka, Serasan Isl. and Borneo, including Labuan IsL ISIS NUMBER: 5301403009003001001., Published as part of James H. Honacki, Kenneth E. Kinman & James W. Koeppl, 1982, Order Scandentia, pp. 107-109 in Mammal Species of the World (1 st Edition), Lawrence, Kansas, USA :Alien Press, Inc. & The Association of Systematics Collections on page 107, DOI: 10.5281/zenodo.7353041