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Speciation in the Brazilian Spiny Rats (Genus Proechimys, Family Echimyidae)
Speciation in the Brazilian Spiny Rats (Genus Proechimys, Family Echimyidae)
BY JOÃO MOOJEN University of Kansas Publications Museum of Natural History Volume 1, No. 19, pp. 301-406, 140 figures in text December 10, 1948 University of Kansas LAWRENCE 1948 University of Kansas Publications, Museum of Natural History Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor Volume 1, No. 19, pp. 301-406, 1 plate, 140 figures in text Published December 10, 1948 University of Kansas Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1948
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INTRODUCTION
INTRODUCTION
The spiny-rats included in the genus Proechimys are common in almost every forest of South America above the Tropic of Capricorn, and in Central America northward to approximately 12° N, in Nicaragua. In size and proportions they are similar to the brown rat Rattus norvegicus but actually they belong to a very different suborder of rodents—the Hystricomorpha. The hystricomorphs are represented in South America by a large variety of animals, of which capybaras, agoutis and cavies are common repre
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METHODS AND TERMINOLOGY
METHODS AND TERMINOLOGY
Pelage. —It was found advisable to use a standardized nomenclature for hairs. The names here proposed are a choice of those used in the literature, with the suffix " form " as an element of uniformity. I feel that it would be advantageous if everyone adopted a similar universal system in mammalogy. The names listed below are used as nouns and are considered as English versions which could easily be adapted to different languages. These names may be complemented with adjectives as needed. Example
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ACKNOWLEDGMENTS
ACKNOWLEDGMENTS
Approximately two thousand skins and skulls were assembled at the Museum of Natural History, University of Kansas, through the coöperation of the authorities in the various institutions of North America, Brazil and Denmark, as listed immediately above. This comprehensive material was used to obtain a more complete understanding of the group, and for the loan of these specimens I am extremely grateful to the authorities of each of the institutions. First of all I acknowledge the encouragement giv
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PALEONTOLOGY
PALEONTOLOGY
The only known, significant, fossil Proechimys comes from deposits in the limestone caves of Lagoa Santa, Minas Gerais, Brazil. These deposits, of Late Pleistocene or Recent age, were extensively studied by P. W. Lund and the results published in a series of French and Danish papers. F. Ameghino (1934:110) studied another fauna from a deposit of similar age in the cave of Iporanga, São Paulo, Brazil. Proechimys is recorded in his account under the inclusive specific name fuliginosus . The molari
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SUBGENERIC VARIATION
SUBGENERIC VARIATION
A few characters are common to one group of species and other features are common to a second group. The most striking of these features is the character of the main fold in the molariform teeth. In one group the fold transversely crosses the crown of the tooth and in the other it extends scarcely halfway across. No specimen is intermediate in this respect. These two groups, furthermore, are separated geographically by an important barrier, the arid belt that starts in the northeastern littoral
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SPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS
SPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS
Most of the described forms in the subgenus were initially named as distinct full species. More recently, however, in accordance with the ideas now prevalent in systematic work, many of the named kinds were reduced to the rank of subspecies. Tate first made a geographic arrangement (1935:399-400) and later (1939:177-178) provisionally synonymised several named kinds of Proechimys with Proechimys " cayennensis cayennensis ." A similar tendency was clearly displayed by Ellerman (1940:115-122) who
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SUBSPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS
SUBSPECIFIC VARIATION IN THE SUBGENUS PROECHIMYS
In spite of the lack of specimens from areas in which Proechimys certainly occurs, it is evident that the genus has great plasticity and that the number of subspecies will be greatly increased as additional material is studied. Only perfunctory examination of samples from outside the area of Brazil shows me that there are several unnamed subspecies there. My impression is that Allen's trinitatis , of Trinidad, the genotype of Proechimys , will eventually be split. There are two main lines of sub
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SPECIFIC VARIATION IN THE SUBGENUS TRINOMYS
SPECIFIC VARIATION IN THE SUBGENUS TRINOMYS
Some specific characters are duplicated in each of the two subgenera; that is to say, there are some parallel developments and they give the common generic stock its biotypical variability. Among these parallel developments are the width of the aristiforms, the amount of pigment in the agouti-colored setiforms, and the shape of the nasal bones. Other characters, however, appear in one subgeneric group and not in the other. The specific variation will be discussed separately for each subgenus. Th
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SUBSPECIFIC VARIATION IN THE SUBGENUS TRINOMYS
SUBSPECIFIC VARIATION IN THE SUBGENUS TRINOMYS
One of the species of Trinomys , Proechimys iheringi , is here subdivided into six subspecies which show a clinal variation. P. i. iheringi , in the southernmost part of the range of the species (Ilha de São Sebastião), has three counterfolds in the upper cheekteeth of almost every young specimen but one of these counterfolds, since it is small, very shallow, and disappears after little wear, is probably in the process of disappearance; all lower cheekteeth have two counterfolds or, rarely, m3 h
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Size and Proportions of External Parts
Size and Proportions of External Parts
Absolute size of head and body, tail, hind-foot and ear are useful in distinguishing subgenera and subspecies and to some extent in differentiating species. The length of head and body is large to medium in Proechimys and medium to small in Trinomys . The tail is long to medium in Trinomys and short in Proechimys . The longest tail, 242 mm, is found in P. i. denigratus , and the shortest tail, 123 mm, in P. g. steerei . The relative length of tail also provides gradients or clines. In every spec
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Pelage
Pelage
The pelage provides most useful taxonomic characters. Excepting the vibrissiform hairs, all of the elements of the pelage have a common feature, the flattened shape. The hair constellation ( cf. Toldt, 1935) on the upper and lateral surfaces is composed of hairs of two main types: aristiforms (guard hairs) and setiforms (over hairs). The aristiforms are wide, strong, and have the dorsal (= anterior) margins raised, forming a wide shallow longitudinal groove on the dorsal face of the hair. The ti
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Skull
Skull
The absolute size of the skull is proportionate to bulk of the body. The supraorbital and parietal ridges are especially developed in the P. semispinosus group, where they extend across the parietals to the interparietals. In all members of the subgenus Proechimys , these ridges extend onto the parietal region. In Trinomys , however, they do not extend so far posteriorly as the parietal, but only onto the squamosal. The rostrum varies from slender to stout. Elongate rostra are common in Proechim
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Incisive Foramen
Incisive Foramen
The shape and dimensions of the incisive foramen long have been recognized as providing specific characters. Large size of the foramen is probably correlated with the requirement for a large amount of moisture reaching Jacobson's organ in the nasopalatine space; the moistening of the sensory epithelium is certainly involved. There seems to be a certain correlation between small size of the incisive foramen and high degree of humidity in the environment. Shapes and dimensions of the foramen appea
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Teeth
Teeth
Considered by itself the variation in the tooth pattern can lead to erroneous conclusions as to differentiation of species, because the number of folds on the occlusal face of a tooth and the depth of certain folds may be subject to great individual variation as shown by examination of more than one large series of specimens of the same kind, age and sex from a single locality. Also there are geographic gradients or clines, in number of folds. Nevertheless the variation in number of folds, when
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HABITS
HABITS
P. dimidiatus was studied in the field and laboratory. P. dimidiatus in captivity showed regular diurnal activity, coming out of the nest for food at intervals. Individuals were fed a cereal mixture and nuts of small size. The animals usually buried the nuts in the sand of the outer cage. While holding the nut with the mouth and front feet, the animal patted the sand rapidly, thus burying the nut, and it then pushed more sand over the place with the front feet. Sometimes the emergence from the n
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CHANGES WITH AGE
CHANGES WITH AGE
Juveniles. —The animals are born with a thick pelage of thin aristiforms and thin setiforms. The color is uniformly blackish brown. The nose, hands, feet, ears and tail are pinkish; P4 and M1 are already erupted and the second molars are included in the bony alveoli. The incisors are orthodont; the rostrum is short and the braincase is wide. The posterior part of the skull is greatly curved dorsally. No change is noticed in the pelage before the second molars erupt and become functional. Adolesc
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Genus Proechimys J. A. Allen
Genus Proechimys J. A. Allen
Genotype. — Echimys trinitatis Allen and Chapman, by original designation. Proechimys Allen and Chapman, 26 December 1899, Bull. Amer. Mus. Nat. Hist., 12(20):264, orig. description; Tate , 1935, Bull. Amer. Mus. Nat. Hist., 68(5):398; Ellerman , 1940, The families and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:115. General characters. —Muriform echimyids of medium size; pelage with flattened and lanceolate and sometimes clavate aristiforms, varying greatly in width and distributed ove
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Artificial Key to the Subgenera and Species
Artificial Key to the Subgenera and Species
General characters. —Pelage with lanceolate aristiforms limited to an area on the dorsal surface between the shoulders and the hips; length of tail less than 90 per cent of length of head and body; skull with conspicuous ridges; extension of supraorbital ridges always evident on parietals; infraorbital foramen usually with separate groove for transmission of nerve; palate usually extended posteriorly as far as third molars; incisors opisthodont; molariform teeth with a small main fold, never ext
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Proechimys goeldii Thomas
Proechimys goeldii Thomas
General characters. —Size large; tail short; aristiforms narrow and soft, usually concealed in pelage by setiforms; general color of upper parts some tint of orange, gradually becoming lighter on sides with no conspicuous, dark longitudinal band on back; feet dark; ventral surface of body and inner side of legs white but sometimes with some buff locally; skull broad and strongly built but not conspicuously ridged; zygomatic expanse great and rostrum not elongate; incisive foramen narrow; bullae
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Proechimys semispinosus (Tomes)
Proechimys semispinosus (Tomes)
Figs. 33, 36. Proechimys semispinosus liminalis , female, MN no. 6253, Rio Quichito. Type. × 1. Figs. 34, 37. Proechimys semispinosus amphichoricus , male, AMNH no. 77020, Mount Duida. Type. × 1. Figs. 35, 38. Proechimys semispinosus kermiti , female, AMNH no. 37124, Lower Rio Solimões. Type. × 1.2 (from photograph). General characters. —Size large; tail short and hairy; aristiforms wide and stiff, especially well-developed on back; general color on upper parts some shade of ochraceous, us
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Proechimys longicaudatus (Rengger)
Proechimys longicaudatus (Rengger)
General characters. —Size medium to large; tail short; aristiforms long and narrow; general color on upper parts Ochraceous-Buff to Ochraceous-Orange, finely and uniformly lined with blackish and not forming evident dark band on back; feet dorsally white or gray; underparts of body and inner sides of legs white; skull elongate and slender with moderate ridges; incisive foramen of medium size; vomerine sheath complete or incomplete; bullae large and elongate; upper molariform teeth with three cou
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Proechimys guyannensis (E. Geoffroy)
Proechimys guyannensis (E. Geoffroy)
Mus guyannensis E. Geoffroy Saint-Hilaire, 1803, Catalogue des mammifères du Museum d'Histoire Naturelle, Paris, p. 194. Echimys cayennensis Desmarest , 1817, Nouv. Dict. Hist. Nat., Paris, nouv. ed., 10:59. Proechimys cayennensis Allen , 1899, Bull. Amer. Mus. Nat. Hist., 12(20):261, 264; Tate , 1935, Bull. Amer. Mus. Nat. Hist., 68(5):399; Ellerman , 1940, The families and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:120. General characters. —Size medium to large; tail usually short; a
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Proechimys guyannensis hyleae subspecies nova
Proechimys guyannensis hyleae subspecies nova
Type locality. —Tauarí, Rio Tapajoz, Porto de Moz , Pará, Brazil; approximately 87 kilometers south of Santarem. Type : Museum of Comparative Zoology at Harvard College, no. 30887, adult male; collected on 19 January, 1934, by A. M. Olalla; original number 7288. Range. —Region of lower Tapajoz River and banks of Amazon up to the Jamundá River. Diagnosis. —Aristiforms conspicuously wide and stiff; general color on upper parts Tawny; incisive foramen long and oval; vomerine sheath complete but wit
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Proechimys dimidiatus (Günther)
Proechimys dimidiatus (Günther)
Echimys dimidiatus Günther, 1 April 1877, Proc. Zool. Soc. London, 1876(4):747. Proechimys dimidiatus Allen , 1899, Bull. Amer. Mus. Nat. Hist., 12(20):264; Ribeiro , 1905, Arch. Mus. Nac. Rio de Janeiro, 13:187; Thomas , 1921, Ann. Mag. Nat. Hist., 8 (ser. 9):141; Tate , 1935, Bull. Amer. Mus. Nat. Hist., 68(5):400; Ellerman , 1940, The families and genera of living rodents, Brit. Mus. (Nat. Hist.), 1:122. Type locality. —Unknown; probably southwestern Rio de Janeiro, Brazil (see Remarks). Type
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Proechimys iheringi Thomas
Proechimys iheringi Thomas
General characters. —Size large; tail long; aristiforms generally wide and stiff; general color on upper parts and sides a combination of blackish from tips of aristiforms with cinnamon ground color from subapical zones of setiforms; darker band on middorsal line; differentiated light-colored aristiforms conspicuous on outer sides of thighs and rump; usually rufous tint on neck and postauricular region; underparts white; tail with white tip, usually accentuated by white brush; feet white on dors
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Proechimys setosus (Desmarest)
Proechimys setosus (Desmarest)
General characters. —Size medium; tail approximately same length as head and body; aristiforms moderately wide; feet rather large; ears of medium size; color on upper parts and sides sepia gradually changing to Ochraceous-Tawny; few differentiated, light-colored aristiforms present on outer thighs and rump; under surface of body and inner sides of legs white; tail with white tip and conspicuous, white pencil; feet white dorsally; skull short and smooth, somewhat flattened in interorbital region;
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Proechimys albispinus (Is. Geoffroy)
Proechimys albispinus (Is. Geoffroy)
General characters. —Size small; tail of same length as head and body or slightly less; feet small; ears of medium size; color of upper parts Ochraceous-Tawny gradually changing to Ochraceous-Buff on sides; differentiated, light-colored aristiforms on back, sides, rump and at base of tail; clavate aristiforms on back with Ochraceous-Tawny or Ochraceous-Buff, subapical zone; underparts of body and inner sides of legs white; tail blackish above, white below, with no white tip; hands and feet white
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Proechimys myosuros (Lichtenstein)
Proechimys myosuros (Lichtenstein)
Loncheres myosuros Lichtenstein , 1818, Das zoologische Museum der Universität zu Berlin, (2):18 ( nomen nudum ); Lichtenstein , 1820, Abhandl. K. Akad. Wissensch., Berlin (1818-1819):192, pl. 1, fig. 2 (orig. descr.); Wied , 1826, Beiträge zur Naturgeschichte von Brasilien, 2:445. Mus leptosoma Brants, 1827, Het geslacht der Muizen door Linnaeus opgesteld ..., Berlyn, p. 150; Lichtenstein , 1830, Darstellung neuer oder wenig bekannter Säugethiere, Berlin, Heft 7, pl. 36, fig. and text pages. Mu
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CONCLUSIONS
CONCLUSIONS
1. The genus Proechimys is divisible into two subgenera. In all Brazil there are four full species of each subgenus, or 8 species in all. All but one of these are divisible into subspecies of which there are 29, making a total of 30 kinds in Brazil; 14 of these are here newly named. 2. It is new information, I think, that: (1) One main fold extending entirely across the worn crown of the molariform tooth is peculiar to Trinomys ; in the subgenus Proechimys , apparent complete division of the
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TABLE 1
TABLE 1
Measurements (in Millimeters) of adults of Proechimys P. g. steerei , ♂ ♂ Hyutanaham USNM 105535 218 123 48 17 53.5 44.0 25.2 19.3 11.7 18.2 8.2 USNM 105536 217 135 50 55.2 45.3 25.7 20.7 11.4 19.2 8.0 ? USNM 105537 56.32 44.9 24.0 20.4 11.4 19.3 8.7 P. g. goeldii , ♂ Fazenda Paraiso AMNH 37489 218 52 20 55.1 44.9 27.0 22.1 12.0 18.6 9.4 ♀ AMNH 37488 228 157 49 22 57.3 47.6 27.9 22.1 12.4 20.3 9.6 P. s. liminalis , ♂ ♂ Rio Quichito Mean 229 145 43 21 58.4 47.6 27.3 21.8 12.9 20.1 8.3 Max
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