Dasyprocta leporina (Linnaeus)

VOSS, ROBERT S., LUNDE, DARRIN P. & SIMMONS, NANCY B., 2001, The Mammals Of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna Part 2. Nonvolant Species, Bulletin of the American Museum of Natural History 2001 (263), pp. 1-236 : 140-155

Dasyprocta leporina (Linnaeus)

VOUCHER MATERIAL: AMNH 265955 ; MNHN 1998.677 . Total = 2 specimens .

IDENTIFICATION: The genus Dasyprocta has never been revised and the current specieslevel taxonomy (e.g., as summarized by Cabrera, 1961; Emmons, 1990, 1997; Woods, 1993) is sorely in need of critical attention. Traditionally, the red­ or yellow­rumped agoutis of Amazonia have been referred to D. aguti (Linnaeus, 1766) , but the oldest available name for these animals is unequivocally D. leporina (Linnaeus, 1758) (see Husson [1978] and Remarks, below).

Our voucher material closely resembles Husson’s (1978) description of Dasyprocta leporina , which was based on the neotype and other specimens from Surinam. The only noteworthy point of difference is the color of the long nape hairs, which are blackish in our vouchers, whereas Husson (p. 459) stated that ‘‘[t]he anterior part of the dorsal surface of the body including the neck is olivaceous gray speckled with yellowish’’, the nuchal hairs apparently not being distinctively colored in the neotype. Husson’s other specimens, however, were described (op. cit.) as having darker necks, and most of the Surinamese agoutis we examined had blackish napes like our vouchers. As noted by Husson, the rump color in this species is also variable, ranging from clear yellow­orange to grizzled reddish­brown in the specimens we examined. Although our single adult voucher (AMNH 265955) is larger than any of the 12 Surinamese specimens measured by Husson (1978: table 82), the differences between homologous dimensions of AMNH 265955 and his largest example (RMNH 18235) are proportionately small (e.g., about 4% in maxillary toothrow length), and we do not regard them as taxonomically significant. Morphometric variation among nine FMNH specimens from Surinam (table 40) likewise suggests that our voucher is large but probably not outside the normal size range of typical D. leporina . For future revisionary work, a large series of specimens collected by H. A. Beatty in the Wilhelmina Mountains of Surinam (see Specimens Examined, below) provides a useful sample of individual variation from a single local population of this nomenclaturally important species.

Both Cabrera (1961) and Ojasti (1972) recognized several subspecies of Dasyprocta aguti (= D. leporina ; see above and Remarks, below) as valid, but the necessity for a trinomial classification remains to be convincingly established by a comprehensive study of geographic variation. From the close similarity between our voucher material and the Surinamese specimens with which we compared them, the Paracou population would be unambiguously referable to the nominate form if other subspecies were to be recognized in a future revisionary study. Alternatively, it is possible that red­rumped agoutis include two or more separate species (as suggested by Krumbiegel, 1941), another hypothesis that remains to be effectively test­ ed by critical analyses of specimen data.

The type of Dasyprocta cristata (Geoffroy, 1803) and another specimen so identified in the RMNH are both zoo animals said to have been collected in Surinam (Husson,

TABLE 40 Measurements (mm) and Weights (kg) of Dasyprocta leporina from French Guiana and Surinam

1978). A single 19th­century RMNH specimen of D. fuliginosa is also said to have come from Surinam (op. cit.). None of this material, however, is accompanied by names of collectors, dates of collection, or any additional geographic information. Because we have not seen any material referable to D. cristata or D. fuliginosa accompanied by definite evidence of origin from any of the Guianas, we assume that these old and poorly documented Surinamese records are erroneous. As discussed by Goeldi and Hagmann (1904), Thomas (1917), and Cabrera (1961), the type of D. prymnolopha , said to be from ‘‘Guiana’’ (Wagler, 1831: 619), was probably collected somewhere along the Atlantic coast of Brazil between the mouth of the Rio Tocantins and Bahia. Apparently, D. leporina is the only agouti species validly known from Guyana, Surinam, French Guiana, and Guianan Brazil. The black agouti ( Dasyprocta fuliginosa ), however, occurs allopatrically in the headwaters of the Orinoco (geographically part of the Guiana subregion of Amazonia) in southernmost Amazonian Venezuela (Tate, 1939; Ojasti, 1972; Handley, 1976).

REMARKS: Although Dasyprocta aguti has long been used as the technical name for one or more geographic forms of red­ or yellowrumped agoutis (e.g., by Waterhouse, 1848; Thomas, 1917; Cabrera, 1961), the basis for this traditional usage is problematic. Because Linnaeus’s (1766) original description of Mus aguti did not mention rump color, the identification of aguti has been justified primarily by reference to the bibliographic sources of his account (Marcgraf, 1648; Piso, 1658; Ray, 1693; Brisson, 1756). Thomas (1898) argued that all of Linnaeus’s sources for Mus aguti could be traced back to the Brazilian animal described by the Dutch explorer­naturalist Georg Marcgraf. According to Thomas, Marcgraf’s agouti was a yellowrumped animal, but this inference is not consistent with what is known about the South American travels of that author.

Marcgraf, an employee of the Dutch West India Company, principally resided at Recife in the northeastern state of Pernambuco, from which base he explored the region effectively controlled by the 17th­century Dutch millitary occupation of northeastern Brazil (Whitehead, 1979). However, red­ (or yellow­) rumped agoutis are not known to occur in Pernambuco (see range map in Emmons, 1990, 1997), nor anywhere else within the geographic limits of Dutch Brazil (as mapped by Boxer, 1973). Instead, Marcgraf’s agouti was almost certainly the black­rumped species of the northeastern Brazilian coast, a taxon currently known as D. prymnolopha (Wagler, 1831) . Marcgraf’s (1648) brief color description and an accompanying woodcut of his ‘‘Aguti vel Acuti Brasiliensibus’’ are too ambiguous to support or refute this inference, but a painting by one of Marcgraf’s contemporaries in Dutch Brazil (reproduced by Teixeira, 1995: vol. 5, p. 28) shows the local species as a more­or­less reddish animal with a blackish middorsal stripe over the rump, closely resembling D. prymnolopha of current usage.

Although this line of reasoning suggests that Dasyprocta aguti is a senior synonym of D. prymnolopha (as suggested by Carvalho and Toccheton, 1969) and not a junior synonym of D. leporina (contra Husson, 1978), our examination of Linnaeus’s (1766) bibliographic sources for Mus aguti does not support Thomas’s (1898) statement that all were based on Marcgraf’s species. Whereas it is true that Piso’s (1658: 102) and Ray’s (1693: 226) accounts were obviously extracted from Marcgraf (1648), Brisson’s (1756: 143) agouti description was based on an examined specimen (as previously noted by Tate, 1935). Unfortunately, Brisson’s description is taxonomically uninformative (like Marcgraf’s), and the geographic origin of his specimen is not stated. However, Brisson was employed in the natural history cabinet of the French naturalist Réaumur (Taton, 1970), so it is probable that all of the Neotropical specimens seen by him were from French Guiana. Additionally, Brisson (1756: 144) gave the geographic range of his agouti as ‘‘Guiania & Brasilia’’ and he cited Barrère’s (1741) description of the ‘‘Agouty’’ of Cayenne. After Réaumur’s death, his collection was transferred to the Cabinet du Roi (Taton, 1970), which subsequently became part of the Muséum National d’Histoire Naturelle. Geoffroy (1803), however, recorded no MNHN agouti material from the ‘‘ancien cabinet’’, nor does that museum now contain any 18th­century specimen of Dasyprocta that might have been the one described by Brisson (L. Granjon, personal commun.).

Finally, Linnaeus’s (1766: 80) account of Mus aguti gave the geographic range as ‘‘Brasilia, Surinamo, Guiania’’ despite the fact that none of his cited references for this species mentioned Surinam. It is therefore probable that Linnaeus himself either had seen specimens of Surinamese agoutis or had reliable reports of them from his many Dutch colleagues and aquaintances. Regrettably, no material of Dasyprocta that is certainly known to have been examined by Linnaeus has apparently been identified in the literature, nor have we succeeded in locating any nomenclaturally useful 18th­century specimens in museums known to contain Linnae­ an mammals. However, any Surinamese agoutis seen by or reported to Linnaeus were necessarily red­rumped animals.

Linnaeus’s Mus aguti is therefore composite, having been based directly or indirectly on lost specimens of both the red­ and the black­rumped species. Because Thomas’s (1898) proposal to restrict aguti to Marcgraf’s Brazilian animal was not equivalent to a lectotype designation, the application of the name aguti is still an open question. In our judgment, it would not be desirable to replace prymnolopha , the name by which the black­rumped agouti of the Brazilian Atlantic coast has been long and consistently known, with aguti , the traditional name for the redrumped species. We therefore select as the neotype for Mus aguti Linnaeus (1766) the same specimen (RMNH 20752) that Husson (1978) designated as the neotype of Mus leporinus Linnaeus (1758) . By this action Dasyprocta aguti becomes an objective junior synonym of D. leporina and current usage (Woods, 1993) is preserved.

OTHER SPECIMENS EXAMINED: Surinam — Brokopondo, Locksie Hattie on the Saramacca River ( FMNH 95757 , 95758 , 95760 ) ; Marowijne, Paloemeu Camp ( FMNH 95763 , 95765 , 95767–95771 ) ; Nickerie, Wilhelmina Mountains on West River ( FMNH 95772– 95778 , 95790 –95792 ) ; Para, Zanderij ( BMNH 1952.1152 – 1952.1154 ) ; Paramaribo, Paramaribo ( BMNH 1952.1155 , 1952.1156 ) ; Saramacca, Dirkshoop ( FMNH 95761 ) ; Suriname, Carolina Kreek ( FMNH 95756 ) .

FIELD OBSERVATIONS: We saw or heard Dasyprocta leporina almost every day that we were in the forest at Paracou, often in the early morning or late afternoon, less frequently in the middle of the day, and only rarely after dark (most nocturnal sightings may have been of individuals frightened from their resting places in dense vegetation). Most individuals were encountered singly, but a few groups of two or three individuals were also seen. We recorded sightings in well­drained primary forest, swampy primary forest, creekside primary forest, and roadside secondary growth. Both of our voucher specimens were shot.

Myoprocta acouchy (Erxleben) Figures 72A , 74 , 75

VOUCHER MATERIAL: AMNH 266566 ; MNHN 1998.678 . Total = 2 specimens .

IDENTIFICATION: Members of the genus

Myoprocta —commonly known as acouchies—are restricted to Amazonia, where most authors have recognized two species, one ‘‘red’’ (or ‘‘reddish’’) and the other ‘‘green’’ (or ‘‘greenish’’), based primarily on coat­color differences. Despite this consensus, the diagnostic morphological characters and geographic distribution of red and green acouchies have yet to be convincingly documented by any published revisionary study based on museum specimens, and the nomenclature of Myoprocta species is currently confused.

Red and green acouchies can be distinguished unambiguously by a combination of external and cranial characters whose diagnostic value we tested by examining all of the Myoprocta specimens (including types) in five American and European museums (AMNH, BMNH, FMNH, MNHN, and USNM). In external appearance, most red acouchies are rich reddish­brown dorsally, with uniformly orange or reddish underparts, whereas most green acouchies are drab yellowish­ or grayish­brown dorsally with yellowish underparts that are usually marked by white midventral streaks. Occasional skins of both the red and green species, however, have somewhat intermediate pigmentation. Thus, a few red acouchies (especially zoo specimens) have rather drab fur (e.g., AMNH 130148, BMNH 5.11.1.19, FMNH 21786), and a few green acouchies (e.g., AMNH 68243, BMNH 54.608) have warmer pelage tones than usual. Some coat­color variation is geographic in origin (e.g., red acouchies from the Guianas have generally less saturated pigments than Brazilian specimens from the north bank of the Amazon), but individual tonal differences also exist within most large series (e.g., 16 AMNH skins of green acouchies from San José Abajo, Ecuador). Nevertheless, the difference in coloration between red and green acouchies is conspicuous when typical exemplars of both kinds are viewed side­by­side.

Another obvious external difference is the presence in all red acouchies of a distinct rump patch of very long (60–80 mm) highly polished hairs that are typically much more heavily pigmented than the fur of the sides, middle back, and forequarters; in life, these hairs form a dark, glossy fringe that actually extends beyond the rump to overlap the base of the tail (Emmons, 1990, 1997). Some specimens (e.g., AMNH 93043) have blackish rump hairs, but the usual color is a deep mahogany brown with or without inconspicuous basal bands of red. In a few Brazilian specimens (e.g., AMNH 94068, 94071; BMNH 20.7.1.23), the rump hairs are not substantially darker than the hairs of the sides and middle back, but they are still distinguishable from the fur of the latter parts by their length and high polish. By contrast, green acouchies never have a distinct rump patch, the fur over the hindquarters being essentially similar in length, color, and texture to the rest of the dorsal pelage.

Red acouchies are, on average, larger than green acouchies, a comparison that is best appreciated by craniometric comparisons of representative series (table 41). Visually, most red acouchy skulls have noticeably larger toothrows and bullae, broader interorbits, and longer nasals than most green acouchy skulls. Although no univariate measurement is diagnostic, red and green acouchies have nonoverlapping morphometric distributions in multivariate ordinations (e.g., by principal components analysis; not shown). Of the several qualitative cranial traits that Tate (1939: table IV) used to distinguish red and green acouchies, the most consistently useful is the size of the ‘‘palatal foramina’’ (= sphenopalatine vacuities), which perforate the bony roof of the mesopterygoid fossa; these are very narrow slits (<1 mm wide) in most specimens of red acouchies (fig. 72A), but they are wider (> 1 mm) teardrop­shaped openings in most specimens of green acouchies (fig. 72B).

Based on specimens that we examined, red acouchies occur throughout Guyana, Surinam, French Guiana, and Brazil north of the Amazon and east of the Rio Branco (fig. 73). We are aware of only two vouchered records of red acouchies outside the Guiana subregion of Amazonia: (1) one specimen ( AMNH 37123 ) collected by Leo E. Miller on 21 April 1914 on the ‘‘ Lower Solimões’ ’, a locality that is now believed (see footnote 17) to correspond to Manacaparú, a settlement on the north bank of the upper Amazon just west of its confluence with the Rio Negro (locality 5 in fig. 73) ; and (2) two spec­

TABLE 41 Comparisons of Craniodental Measurements (mm) from Representative Samples of Adult Red Acouchies ( Myoprocta acouchy ) and Green Acouchies ( M. pratti )

imens (FMNH 50895, 50896) collected by A. M. Olalla on 9 August 1936 at Lago do Baptista on the south bank of the Amazon between the Rio Madeira and the Rio Tapajos (locality 3 in fig. 73). Based on the latter record, we assume that unvouchered reports of unidentified Myoprocta from other sites along the south bank of the Amazon between the Madeira and the Tocantins (e.g., George et al., 1988; Voss and Emmons, 1996: appendix 8) were probably of red acouchies. Acouchies are apparently unknown east of the Rio Tocantins (Carvalho and Toccheton, 1969; Pine, 1973).

By contrast, green acouchies are extensively distributed in western Amazonia (west of the zoogeographic axis defined by the Rio Negro and the Rio Madeira), and they also occur in the headwaters of the Orinoco in southernmost Venezuela (Tate, 1939; Handley, 1976; Linares, 1998). Although a few published sources imply that red and green acouchies occur sympatrically in eastern Ecuador (Lönnberg, 1925) or eastern Colombia (Emmons, 1990, 1997), our specimen data suggest that red and green acouchies are allopatrically distributed. At least some of the historical uncertainty about the geographic ranges of red and green acouchies is due to the confused technical nomenclature for these animals.

Erxleben’s ( 1777) original description of Cavia acouchy mentioned only small size, presence of a tail, and olivaceous coloration as characters distinguishing this species from other terrestrial hystricognaths then referred to the genus Cavia . Apparently, Erxleben did not examine any specimens himself, but instead based his description of acouchy on the earlier accounts of des Marchais (1730), Barrère (1741), Buffon (1767), and Pennant (1771) that he cited as references. We examined all of these early works and determined that Buffon and Pennant contain nothing more than rephrased versions of des Marchais’ and Barrère’s very brief reports about the ‘‘Agouchi’’ or ‘‘Akouchy’’ of Cayenne. By way of description, des Marchais stated only that the Agouchi is smaller and tastes better than the Agouti ( Dasyprocta leporina ), but Barrère (quoted verbatim by Tate [1935: 331] and Husson [1978: 471]) mentioned a tail and olive coloration.

There has never been any question that Erxleben’s sources were describing a Myoprocta from French Guiana, but the refer­ ence to olive coloration has led to conflicting taxonomic applications of the epithet acouchy . Thomas (1926: 639) argued that this name applies to the reddish species based on the geographic origin of des Marchais’ and Barrère’s observations, noting that ‘‘many specimens of this animal are of a somewhat olivaceous tone, which, in the absence of [M.] pratti [the green acouchy], might easily justify the word being applied to them.’’ Cabrera (1961) agreed, noting that Erxleben’s original sources were not professional naturalists and might have been describing the species inaccurately from memory. By contrast, Tate (1939), Carvalho (1962), and Husson (1978) applied the name acouchy to the green species based on Barrère’s color description; according to these authors, the red acouchy should be called M. exilis (Wagler, 1831) .

The crux of this disagreement is whether geography or color is to be given greater importance in applying the name acouchy . In the absence of an extant type, 20 the issue cannot be definitely resolved, and both of the conflicting usages mentioned above are current in the literature (e.g., Woods, 1993; Emmons, 1990, 1997). Since the geographic datum is definite whereas the color description is subject to interpretation, we favor Thomas’s (1926) and Cabrera’s (1961) usage, which also avoids the absurdity of making French Guiana —where only red acouchies are known to occur—the type locality for the green species. In order to fix this application of Myoprocta acouchy and thereby stabilize the species­level nomenclature of Myoprocta , we select as the neotype of Cavia acouchy Erxleben ( 1777) our adult Paracou voucher, AMNH 266566, consisting of a well­preserved skin (fig. 74), skull (fig. 75), and postcranial skeleton; measurements of this specimen are provided in table 42 along with those of other conspecific adults from French Guiana.

Our assignment of nominal taxa in the genus Myoprocta to either the red or green species groups (table 43) is based on first­hand examination of types and/or original descriptions. Although some Brazilian specimens of red acouchies are larger and redder than most specimens from Guyana, Surinam, or French Guiana, all red acouchies closely resemble one another and we see no compelling evidence that more than a single species is represented. Green acouchies, however, appear to exhibit significant geographic variation and may eventually prove to be a complex of closely related species; nevertheless, all

20 According to Husson (1978: 472), ‘‘we may consider Barrère’s specimen to be the lectotype of this species’’, but it is unclear whether Barrère actually saw an acouchy himself or was merely repeating what he had been told about it by natives. Geoffroy (1803: 167) mentioned an old Paris museum specimen (‘‘Individu provenant de l’ancien cabinet’’) of Cavia acuschi [sic] that might have been seen by Barrère, but Rode (1945) did not list it in his catalog of MNHN rodent types, and the museum does not now contain any 18th­century specimens of Myoprocta (L. Granjon, personal commun.). In the absence of any indication to the contrary, we assume that the lectotype no longer exists.

can be provisionally referred to M. pratti pending a comprehensive study of this group.

OTHER SPECIMENS EXAMINED: Brazil — Amapa´, Serra do Navio ( USNM 546313 ) ; Amazonas, Boca Rio Paratucu on Rio Jamundá ( AMNH 94073–94075 ), Lago do Baptista on Rio Amazonas ( FMNH 50895 , 50896 ), Lago do Serpa on Rio Amazonas ( FMNH 50897 ), ‘‘ Lago do Taraci on Rio Negro’ ’ ( BMNH 27.8.11.52), Lower Solimões ( AMNH 37123 ), Santo Antonio do Amatari ( AMNH AMNH 92886–92888 , 93043 ) ; Para´, ‘‘ Castanhal on Rio Jamunda´ ’’ ( AMNH 94076 ), Colonia do Veado ( BMNH 12.5.11.9), Faro ( AMNH 94068–94072 ), Monte Alegre ( BMNH 20.7.1.23), Cachoeira Porteira ( USNM 546296 , 546297 ), San José on Rio Jamundá ( AMNH 94077 ) ; Roraima, Conceição ( FMNH 20007 ), Serra Grande ( FMNH 20019 ) . French Guiana — Saut Macaque ( MNHN 1962.1329 ), St.­ Laurent du Maroni ( MNHN 1909.243 ), Tamanoir on Mana River ( FMNH 21783 , 21785–21787 ), no other locality data ( MNHN 1962.1330 , 1974.268 ) . Guyana —‘‘ Bonasica on Essequibo River’ ’ ( AMNH 36493 [type of demerarae ], BMNH 12.6 .5.28, 13.5.23.6– 13.5.23.9), ‘‘ Kuitaro River’ ’ ( USNM 338969–338971 ), ‘‘ Manarica Creek on Essequibo River’ ’ ( BMNH 13.6.8.11), ‘‘Moon Mountains’’ ( BMNH 11.6.7.45), ‘‘Supinaam River’’ ( BMNH 20.7.1.20–20.7.1.22) ; Cuyuni ­Mazaruni, Kartabo ( AMNH 8178 ) ; Potaro ­Siparuni, Potaro ( BMNH 3.4 .6.6, 3.4.6.7) ; Upper Demerara ­Berbice, ‘‘ Comackka on Demerara River’ ’ ( BMNH 5.11.1.19), Moraballi ( BMNH 34.6.30.57– 34.6.30.61) ; Upper Takutu ­Upper Essequibo, Dadanawa ( USNM 339670 ) . Surinam — Brokopondo, Locksie Hattie ( FMNH 95753 [two specimens with this number]) ; Marowijne, Paloemeu Camp on Tapahoni River ( FMNH 95593 , 95754 , 95787 ) ; Nickerie, Kaiserberg Airstrip on Zuid River ( FMNH 93270–93277 ), Wilhelmina Mountains on West River ( FMNH 95755 ) .

FIELD OBSERVATIONS: We frequently heard the alarm calls of Myoprocta acouchy and we caught glimpses of fleeing individuals on many occasions, but we seldom obtained an unobstructed view of the animal in repose. Our single adult voucher was taken on the

1777 (= Myoprocta acouchy ). Both views about Χ0.3.

TABLE 42 Measurements (mm) and Weight (kg) of the Neotype and Other Specimens of Myoprocta acouchy from French Guiana

TABLE 43

Species Groups, Nominal Taxa, and Type Localities of Acouchies (Genus Myoprocta )

ground in a leghold trap in swampy primary forest, and a juvenile specimen was subsequently taken in a Victor trap tied to the base of a broad liana 50 cm above the ground in well­drained primary forest. Four unvouchered observations recorded in our fieldnotes document the presence of this species in well­drained primary forest, swampy primary forest, creekside primary forest, and secondary vegetation. Most of our sightings were diurnal, usually in the very early morning or late afternoon, but a few animals were flushed from their hiding places at night.

CUNICULIDAE

Only a single cuniculid species occurs at Paracou. The lowland paca is unmistakable in external and craniodental characters and cannot be confused with any other species of Guianan mammal.

Cuniculus paca (Linnaeus)

VOUCHER MATERIAL: AMNH 265954 , 266567 , 266569 ; MNHN 1998.679 . Total = 4 specimens .

IDENTIFICATION: Our specimens are topotypes of this species (the type locality of which was restricted to French Guiana by Tate , 1935) and agree closely with Husson’s (1978) detailed description and illustrations of Surinamese material. Selected measurements (mm) and weights (kg) of two adult male vouchers ( AMNH 265954 , MNHN 1998.679 ) are: HBL 650, 739 ; LT 0, 11; HF 115, 121; Ear 52, 53; CIL 138.1, 134.4; LD 54.3, 52.7; MTR 27.3, 30.5; LN 52.4, 51.0; LIB 41.2, 42.4; ZL 72.3, 77.0; ZB 98.4, 105.2; Wt 9.5, 9.2.

The lowland paca ranges from southern Mexico to Paraguay, and several subspecies have been recognized as valid by authors (e.g., Krumbiegel, 1940b; Cabrera, 1961). Although Krumbiegel (1940b) cited pelage and cranial characters to justify his trinomial distinctions, no comprehensive review of geographic variation in this species based on the very large museum collections now available for study has yet been attempted. In the absence of such a critical undertaking, a subspecific nomenclature does not seem warranted at present; however, our material would obviously represent the nominate race if trinomials were to be recognized in any future revision.

In a recently published opinion, the International Commission on Zoological Nomenclature (ICZN, 1998) ruled that Cuniculus was available from Brisson (1762), thus replacing Agouti Lacépède (1799) as the oldest valid generic name for the lowland paca.

FIELD OBSERVATIONS: We collected four specimens of Cuniculus paca at Paracou and recorded 24 unvouchered observations in our fieldnotes. Habitat information accompanying 26 records include 7 encounters (27%) in well­drained primary forest, 4 (15%) in swampy primary forest, 6 (23%) in creekside primary forest, 1 (4%) in primary forest of unspecified character, and 9 (35%) in secondary vegetation; all encounters were nocturnal. Pacas were encountered singly, except in rare cases when we witnessed agonistic encounters between two adults or saw an adult female accompanied by a juvenile. Most individuals were sighted on the ground, but one individual was submerged in a stream under a fallen tree, apparently attempting to hide underwater.

ECHIMYIDAE

We captured or observed four echimyid species at Paracou, including representatives of the genera Makalata , Mesomys , and Proe­

chimys. Based on collections from other localities in French Guiana and Surinam (appendix 1), it seems probable that two additional echimyids could occur locally. Although species of Proechimys can only be distinguished from one another with adult specimens in the hand, other French Guianan echimyids can be identified at a distance by well­marked external characters (Emmons, 1990, 1997) if a sufficiently clear view is obtained. Unfortunately, although the taxa in question are readily distinguished, their nomenclature is still problematic in some cases.

Makalata didelphoides (Desmarest)

Our only record of this species at Paracou is an unambiguous sighting by DPL of a solitary adult perched on a tree trunk 3 m above a small stream in primary forest at 10:30 hours on 27 October 1992.

In most of the older literature (e.g., Tate, 1935, 1939; Cabrera, 1961) this species is called Echimys armatus (I. Geoffroy) , but Husson (1978) proposed the new genus Makalata with armatus as type species in recognition of the well­marked craniodental differences between this taxon and Echimys chrysurus (the type species of Echimys G. Cuvier ). For the use of didelphoides to replace armatus as the oldest available name for the red­nosed tree rats of the Guiana subregion of Amazonia, see Emmons (1993b).

Mesomys sp.

VOUCHER MATERIAL: AMNH 266596.

IDENTIFICATION: The genus Mesomys has never been revised and the identification of its constituent species has long been problematic. Woods ( 1993) recognized M. didelphoides (Desmarest) , M. hispidus (Desmarest) , M. leniceps Thomas , M. obscurus (Wagner) , and M. stimulax Thomas as valid species, but Emmons (1993b) showed that didelphoides and obscurus both belong in the genus Makalata , and Patton et al. (2000) subsequently described a new species, Mesomys occultus . Therefore, current usage would now recognize four valid species of Mesomys : M. hispidus (including ecaudatus Wagner, ferrugineus Günther , and spicatus Thomas as synonyms; after Woods, 1993), M. leniceps , M. occultus , and M. stimulax .

In order to identify our single Paracou voucher, we consulted the original descriptions of all nominal taxa currently referred to Mesomys , and we examined the holotypes of every named form except ecaudatus. In addition, we measured relevant series of specimens in the AMNH, USNM, and BMNH to assess geographic variation in morphometric characters. Below we explain why, despite this effort, we are still unable to confidently assign a specific epithet to our material.

Of all the material we examined, the most distinctive is the holotype of Mesomys leniceps from the Andean highlands of eastern Peru. This specimen (BMNH 26.8.6.61) is distinguished from all other congeners by its much longer tail (relative to head­and­body length), finer and denser tail hairs, finer and softer spines, more convergent toothrows, posteriorly constricted incisive foramina, and much smaller bullae. By contrast, Amazonian specimens of Mesomys (including all of the remaining nominal taxa in this genus) have relatively shorter tails, coarser spines and tail hairs, less convergent toothrows, posteriorly unconstricted incisive foramina, and larger bullae. Although we searched diligently for external and craniodental character variation among Amazonian samples of Mesomys , only maxillary toothrow length appears to offer any broadly useful morphological basis for taxonomic inference.

The first example of Mesomys to be reported from any of the Guianas was a Surinamese specimen that Husson (1978) identified as M. stimulax . We have examined five additional specimens (table 44) from the Guiana subregion, including our Paracou voucher, all of which essentially resemble Husson’s material and appear to represent the same taxon despite substantial variation in some cranial dimensions (plausibly attributable to age differences) and in external proportions (perhaps attributable to measurement artifacts). Consistent with Husson’s identification, these Guianan specimens have small toothrows (MTR = 5.9–6.6 mm) that fall within the range of variation exhibited by specimens referable to stimulax from southeastern Amazonia (right­hand column, table 44). By contrast with these smalltoothed Guiana and Southeastern subregion samples, all western Amazonian Mesomys samples have mean toothrow lengths greater than 7 mm (e.g., the series measured by Patton et al., 2000: tables 56, 58). Small­toothed and large­toothed Mesomys are sympatric at Igarapé Amorim on the left (west) bank of the Rio Tapajos (specimens in AMNH), but elsewhere these morphometric classes appear to be allopatric. Although it is geographically part of the Guiana subregion of Amazonia, the Venezuelan state of Amazonas is inhabited by large­toothed Mesomys (e.g., nine USNM specimens with a mean maxillary toothrow length of 7.2 mm), an observation consistent with the presence of other western Amazonian taxa (e.g., Dasyprocta fuliginosa , Myoprocta pratti ; see above) in that area.

Although western Amazonian Mesomys specimens have often been identified as M. hispidus (e.g., by Cabrera, 1961; da Silva and Patton, 1993; Patton et al., 1994, 2000; Voss and Emmons, 1996), this usage appears to be incorrect. The maxillary toothrow of the type of hispidus 21 measures 6.4 mm, well outside the observed range of variation in this dimension for any known western Amazonian sample. Unfortunately, it is not known exactly where the type was collected. Desmarest (1817) gave the type locality as ‘‘l’Amérique méridionale’’, but the specimen was almost certainly obtained by Alexandre Rodriguez Ferreira, 22 whose known collect­

21 Rode’s (1945) catalog of MNHN rodent types lists that of Echimys hispidus as a mounted specimen (number 1806 in the old ‘‘montage’’ series of the MNHN) from which the skull had been extracted and lost. The skull, however, identified as that of the type by a BMNH label in Thomas’s handwriting, is still preserved as A­ 7668 in the nearby Laboratoire d’Anatomie Comparée. Emmons (1993b) and RSV independently examined both skin and skull, which we judge to be correctly associated in the absence of any indication to the contrary.

22 The 19th­century wooden base on which the type skin of Mesomys hispidus is still mounted bears the inscription ‘‘du Cabinet de Lisbonne 1808’’, indicating that this specimen was part of the plunder that Napoleon’s troops shipped to Paris following the sack of Lisbon. That shipment apparently included the entire collection of natural history specimens assembled in Brazil between 1783 and 1792 by Ferreira, an employee of the Museu Royal d’Ajuda (Hershkovitz, 1987a). Significantly, the primates illustrated in Ferreira’s ‘‘Viagem Filosófica’’ include two taxa ( Chiropotes satanas chiropotes and Saguinus midas midas ; op. cit.: table 2) that must have been collected or observed in the Guiana subregion of Amazonia, where the type of Mesomys hispidus might also have been taken.

TABLE 44 Measurements (mm) and Weights (g) of Adult Specimens of Small­Toothed Mesomys from the Guiana and Southeastern Subregions of Amazonia

ing itinerary (reproduced by Hershkovitz, 1987a: fig. 3) was largely confined to Amazonian Brazil. Tate (1935) proposed restricting the type locality of hispidus to Borba, a settlement on the right bank of the lower Rio Madeira where Natterer collected the type of ecaudatus in 1830 (Pelzeln, 1883). Tate’s action was biologically arbitrary but served to justify his synonymization of hispidus and ecaudatus, the types of which he had not seen. Unfortunately, two species of Mesomys with divergent toothrow measurements are known to occur in the interfluvial region between the Madeira and the Tapajos (e.g., at Igarapé Amorim, see above) and it is not known whether the type of ecaudatus is a small­toothed animal (like hispidus ) or not. Until the type of ecaudatus is examined and measured, the oldest available name based on a large­toothed Mesomys specimen is ferrugineus Günther (1876) from northeastern Peru.

Based simply on toothrow measurements, our Paracou voucher and other similar specimens from the Guiana subregion of Amazonia could justifiably be referred to Mesomys hispidus , of which stimulax is perhaps only a junior synonym. However, Patton et al. (2000) reported high cytochrome­b sequence divergence between small­toothed Mesomys specimens from opposite sides of the Amazon, a result that clearly indicates the

insufficiency of toothrow length as a basis for taxonomic inference and brings into sharper focus the problem of exactly where the type of hispidus was collected (see footnote 22). For the moment, these are insoluble problems for which the only appropriate interim solution is to leave our voucher material unnamed.

OTHER SMALL­ TOOTHED SPECIMENS EXAM­ INED FROM THE GUIANA SUBREGION: Brazil — Amapa´, Serra do Navio (USNM 543283). French Guiana —Les Nouragues (V­924). Guyana — Potaro ­Siparuni, 5 km SE Surama (ROM 103346); Upper Takutu ­Upper Essequibo, Maipaima Creek in Kanuku Mountains (LHE 968, an uncataloged specimen to be deposited in UG).

FIELD OBSERVATIONS: Our single record of Mesomys from Paracou is based on a specimen taken in a Victor trap tied to a broad liana 1.9 m above the ground in swampy primary forest.

Figures

Fig. 72. Fenestration of the bony roof of the mesopterygoid fossa in typical examples of Myoprocta acouchy (A, AMNH 266566) and M. pratti (B, FMNH 125085). The sphenopalatine vacuities (spv) are usually present only as narrow (<1 mm) slits in the bony roof of the mesopterygoid fossa of M. acouchy, but in M. pratti these fenestrae are wider, teardrop­shaped apertures.

Fig. 74. Dorsal and ventral views of the skin of AMNH 266566, neotype of Cavia acouchy Erxleben,

Fig. 75. Dorsal, ventral, and left lateral views of the skull of AMNH 266566, neotype of Cavia acouchy Erxleben, 1777 (= Myoprocta acouchy). All views approximately Χ1.3.