Well-Groomed Predecessors Assigned to the Lorisid Species Nycticeboides Simpsoni

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536 Nature Vol. 289 12 February 1981 from the late Miocene Siwalik deposits of Pakistan (some 7-10 million years old) Well-groomed predecessors assigned to the lorisid species Nycticeboides simpsoni. This newly from R. D. Martin discovered species definitely had a tooth RECONSTRUCTIONS of mammalian phy It has been claimed 7 that the tooth-comb in comb, and Rose et a/. have applied their logeny have depended heavily on dental small-bodied lemurs and lorises is too SEM procedure to the crowns of one evidence, since teeth are preferentially fragile to allow for its use in feeding, but canine and two incisors. These teeth closely preserved in the fossil record. As a rule fruit pulp provides no great resistance and resemble their counterparts in modern anterior teeth (especially incisors) are easily gums are usually collected in a semi-liquid lorisids and SEM examination revealed the lost in fossilization and most weight has state. It is therefore a moot point whether fine vertical grooves characteristic of use in been placed on the characteristics of cheek grooming or feeding was the primary grooming. Thus, the use of the lorisid teeth (premolars and molars). However, function of the tooth comb in lemurs and tooth-comb in grooming can be definitely there are some striking modifications of the lorises, but it is certain that both functions traced back at least 7 million years. Un lower anterior teeth among living are served in extant species. fortunately, though, feeding on gum or mammals and these provide not only useful Our understanding of the origin of soft fruit pulp is not known to leave diagnostic features but also valuable tooth-comb grooming has now been con characteristic wear patterns on the tooth functional clues. A good example is the siderably advanced by the report by Rose, comb, so possible dietary function remains 'tooth-comb' formed by the procumbent Walker and Jacobs (see this issue of Nature untested. lower front teeth in mammal groups such p583) that wear patterns produced by Jacobs regards Nycticebodies simpsoni as the tree-shrews, strepsirhine primates repeated passage of hairs between the as belonging to the subfamily Lorisinae (lemurs and lorises) and 'flying lemurs' lower anterior teeth can be clearly (including the slow-moving pottos and (which actually are not lemurs and do not recognised with the scanning electron their relatives), rather than to the fly - they are unusual gliding mammals microscope (SEM). SEM photographs of Galaginae (the agile, saltatory relegated to their own order, Dermoptera). the lower anterior dentitions of extant bushbabies). It is true that Nycticeboides The tooth-comb of lemurs and lorises is strepsirhine primates, such as Galago shares with modern lorisines specific particularly unusual in that the lower crassicaudatus, reveal fine vertical grooves characters such as simple rear premolars, canines are incorporated along with the on the sides of the teeth. Similar grooves relatively weak development of the fourth incisors, and it is now widely accepted that are found on the lower incisors of certain cusp (hypocone) on the upper molars, and a unique six-tooth comb (two canines and tree-shrew species, but no such wear poor development of the ectepicondylar four incisors) was probably an ancestral patterns are found on the comb-like lower flange on the humerus. However, such feature of lemurs and lorises. 1•2 In tree incisors of the flying lemur, suggesting that characters only indicate a phylogenetic link shrews, by contrast, the tooth-comb is their function is restricted to feeding. This between Nycticeboides and lorisines if they formed by some or all of the six lower new evidence is particularly valuable emerged after the divergence between incisors without involvement of the canine because the findings can be extended back galagines and lorisines (that is, if they are teeth, and in flying lemurs the four lower through the fossil record. A tooth-comb not primitive features of the lorisids), and incisors all have crenulated tips and act as consisting of six lower incisors has been this remains to be demonstrated. But if individual combs. These are doubtless reported8 for early Tertiary Jacobs is right, the presence of convergent developments. (Palaeocene/Eocene) arctocyonid Nycticeboides in the Siwalik deposits could The tooth-comb has often been seen as condylarths and Rose et a/. have demon have a wider significance, since an adaptation for grooming of the fur. strated that the lower incisors of these early Ramapithecus (regarded by many Indeed, virtually all tree-shrew, lemur and placental mammals bear grooves closely palaeontologists as an early relative of loris species have been seen using the tooth resembling those found on the comb-teeth man) also occurs in the Siwaliks. All comb in a characteristic rake-and-lift of modern lemurs, lorises and tree-shrews. modern lorisine species, unlike some action to groom the fur, though no such This neatly confirms the proposal made by bushbabies, are confined to relatively use of the lower incisors has been recorded Gingerich and Rose that the lower incisors dense forests with virtually continuous for the flying lemur. Despite some past of these condylarths were used for arboreal pathways. Modern tree-shrews claims to the contrary3•4 there is now no grooming. This would seem to be the are similarly confined to forested regions doubt that the tooth-comb serves a earliest direct fossil evidence of a and fossil tree-shrews have already been valuable grooming function in tree-shrews mammalian behaviour pattern, and it reported from these same Siwalik and in strepsirhine primates. Nevertheless, would certainly appear to be the most deposits10•11 • The combined evidence of in recent years evidence has accumulated reliable demonstration that mammalian forest conditions provided by fossil that all of these species also use their hair was definitely in existence over 55 lorisines and tree-shrews in the Siwaliks anterior lower teeth for feeding. For million years ago! Significantly, the earliest raises the possibility that Ramapithecus instance, soft fruit pulp may be scooped (mid-Palaeocene) condylarth species was also at least partly a forest-living out with the tooth-comb and detailed field examined by Rose eta/. also exhibited wear primate. If Ramapithecus does lie close to observations of nocturnal lemurs and on the tips of the comb-teeth, indicating a the origin of the hominid line, as many lorises 5 have revealed that many species combined grooming and feeding function. authorities believe, confirmation of a feed upon gums (natural polysaccharide Reconstruction of the evolutionary forest background for this Miocene genus exudates from trees). For one species- the history of the tooth-comb in lemurs is would be of great value, if only in ruling out lesser bushbaby (Galago senegalensis) - hampered by the poor fossil record. Until some of the speculative suggestions which clear evidence of the use of the tooth-comb recently, the only reliable early fossil forms have been made in the past. D in gum-feeding has been collected6 • were early Miocene lorisids from East

Further, the greatest development of the Africa (approx. 18-20 million years old). I. Martin Phil. Trans. R. Soc. 264, 295 (1972). tooth-comb (once body size has been taken On the basis of indirect evidence, all three 2. Cartini in Phylogeny of the Primates(ed. Lucke!! & Szalay) 313 (Plenum, New York, 1975). into account) is found in two species which recognised East African lorisid genera 3. Stein Am. Nat. 70, 19 (1936). 4. Avis Am. J. Phys. Anthrop. 19, 55 (1961). feed predominantly on gums, the needle from the Miocene (Komba; Progalago; 5. Martin in The Study of Prosimian Behavior (ed. Doyle & clawed bush baby (Galago elegantulus) and Mioeuoticus) are thought to have Martin) 45 (Academic, New York, 1979). 6. Bearder & Martin Int.]. Primatol. 1, 103 (1980). the fork-crowned lemur (Phaner furcifer). possessed tooth-combs like their modern 7. Szaley & Seligsohn Folia Primatol. 27, 75 (1977). 8. Gingerich & Rose J. Mammal. 60, 16 (1979). relatives, but no anterior tooth crowns are 9. Walker in Prosimian Biology (eds. Martin, Doyle & known9 • Now Jacobs (see this issue of Walker) 435 (Duckworth, London, 1974). R.D. Martin is Reader in Physical 10. Chopra, Kaul & Vasishat Nature 281, 213 (1979). Anthropology, University College London. Nature p585) has reported new fossil finds II. Chopra& VasishatNature281, 214(1979).