The anatomy of the world's largest extinct rodent.
ABSTRACT Phoberomys is reported to be the largest rodent that ever existed, although it has been known only from isolated teeth and fragmentary postcranial bones. An exceptionally complete skeleton of Phoberomys pattersoni was discovered in a rich locality of fossil vertebrates in the Upper Miocene of Venezuela. Reliable body mass estimates yield approximately 700 kilograms, more than 10 times the mass of the largest living rodent, the capybara. With Phoberomys, Rodentia becomes one of the mammalian orders with the largest size range, second only to diprotodontian marsupials. Several postcranial features support an evolutionary relationship of Phoberomys with pakaranas from the South American rodent radiation. The associated fossil fauna is diverse and suggests that Phoberomys lived in marginal lagoons and wetlands.
Article: The Incredible Fossils of Urumaco and Beyond: Exploring Venezuela’s Geologic Past: URUMACO AND VENEZUELAN PALEONTOLOGY: THE FOSSIL RECORD OF THE NORTHERN NEOTROPICS. Edited by Marcelo R. Sánchez-Villagra, Orangel A. Aguilera, and Alfredo A. Carlini. Bloomington: Indiana University Press. 2010. 286 pp., $49.95 (cloth). ISBN: 978-0-253-35476-1Journal of Mammalian Evolution 01/2013; 20(2). · 2.63 Impact Factor
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ABSTRACT: Caviomorph rodents represent an excellent model to explore morphological diversification on a macroevolutionary scale, as they are ecologically and morphologically diverse. We analysed cranial shape variation using geometric morphometrics and phylogenetic comparative methods. Most variation involved the shape of the rostrum, basicranium, and cranial vault, and clearly matched the phylogenetic structure. At the same time, a strong allometric pattern was associated with the length of the rostrum and cranial vault, size of the auditory bulla, and depth of the zygomatic arch. After accounting for size influence, and taking phylogenetic structure into account, shape variation was significantly associated with habitat. Our results highlight the presence of complex relationships between morphological, phylogenetic, and ecological dimensions in the diversification of the caviomorph craniumBiological Journal of the Linnean Society 10/2013; · 2.54 Impact Factor
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ABSTRACT: The island rule entails a modification of the body size of insular mammals, a character related with numerous biological and ecological variables. From the Miocene to human colonization (Holocene), Mediterranean and Canary Islands were unaltered natural ecosystems, with paleofaunas formed with endemic giant rodents among other mammals. Our aim is to create methods to estimate the body masses of fossil island rodents and address the nature of ecological pressures driving the island rule. We created regression equations based on extant rodent data and used these to estimate the body masses of the extinct species. Our results show strong correlations between teeth, cranial and postcranial measurements and body mass, except for the length of the long bones, the transversal diameter of the distal tibia and the anteroposterior diameter of the proximal tibia, where the equations were less reliable. The use of equations obtained from a more homogeneous group (suborder and family) is preferable when analyzing the area of the first molar. The new regressions were applied to estimate the body masses of some Mediterranean and Canarian fossil rodents (Canariomys, C. bravoi 1.5 kg and C. tamarani 1 kg; Hypnomys, H. morpheus 230 g and H. onicensis 200 g; and Muscardinus cyclopeus 100 g). Our results indicate that under absence of predation, resource availability (island area) is the key factor that determines the size of the Canariomys sp. However, under presence of specialized predators (birds of prey), body size evolution is less pronounced (Hypnomys sp.).Integrative Zoology 03/2014; 9(2):197-212. · 1.42 Impact Factor
References and Notes
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Supporting Online Material
27 June 2003; accepted 13 August 2003
The Anatomy of the World’s
Largest Extinct Rodent
Marcelo R. Sa ´nchez-Villagra,1* Orangel Aguilera,2Ine ´s Horovitz3
Phoberomys is reported to be the largest rodent that ever existed, although it
has been known only from isolated teeth and fragmentary postcranial bones.
An exceptionally complete skeleton of Phoberomys pattersoni was discovered
in a rich locality of fossil vertebrates in the Upper Miocene of Venezuela.
Reliable body mass estimates yield ?700 kilograms, more than 10 times the
mass of the largest living rodent, the capybara. With Phoberomys, Rodentia
becomes one of the mammalian orders with the largest size range, second only
to diprotodontian marsupials. Several postcranial features support an evolu-
tionary relationship of Phoberomys with pakaranas from the South American
rodent radiation. The associated fossil fauna is diverse and suggests that
Phoberomys lived in marginal lagoons and wetlands.
Phoberomys belongs to the Caviomorpha, a di-
verse and endemic group of South American
rodents that includes arboreal, cursorial, and
fossorial forms and that ranges today in size
between ?200 g and ?50 kg (1). The evolution
of caviomorphs is recorded in a rich but geo-
graphically biased fossil record. The southern
portion of South America contains most of the
record (2); hence, discoveries in the northern
tropics are of special significance. The Urumaco
Formation in northwestern Venezuela contains
one of the few examples of a diverse fauna of
Upper Miocene vertebrates in the continent. Re-
cent explorations resulted in the discovery of
additional vertebrates in the upper and middle
members of this formation, including the rodent
reported here (table S1). Old and new discover-
ies make Urumaco one of the best-documented
tropical Miocene fossil fauna of vertebrates in
the world after La Venta in Colombia (3).
The Urumaco Formation is characterized
by diverse faunal associations in continental
(savannas), freshwater (swamps and rivers),
estuarine (brackish), and marine (coastal la-
goon, salt marsh, and sandy littoral) environ-
ments (table S1). Each assemblage can be
correlated with a distinctive sedimentary en-
vironment. The following facies are apparent:
shallow-water marine sediments rich in mol-
lusks and fishes; brackish water rich in ma-
rine catfish; and swampy paleoenvironments
rich in crocodilians and gavialids, in fresh-
water and marine turtles, and in freshwater
catfish. These general sequences repeat sev-
eral times in the outcrop (4). The skeleton
reported here was found in brown shales
interbedded with thin layers of coal.
Two specimens of Phoberomys pattersoni
Mones 1980 (5) provide the basis for this re-
port. One consists of an almost complete asso-
ciated skeleton (Fig. 1A). The skull is poorly
preserved and consists of a deformed palate
with the upper molariform series and most of
the dentaries, with molariform teeth and frag-
ments of the incisors. An additional shattered
partial skull, preserving most of the occipital
and portions of the basicranial region, was also
collected (Fig. 1B). Based on the degree of
tooth wear and sutural fusion, we estimate that
the specimens were adults at the time of death.
The proximal epiphysis of the tibia and the
distal epiphysis of the ulna are not fused to the
diaphysis. However, it is possible that the ani-
mal was an adult, because no sutures can be
recognized in the occipital region. In the pa-
karana Dinomys, probably the closest extant
relative of Phoberomys, the epiphyses of long
bones fuse late in ontogeny, some during adult-
hood (6). A description of the anatomy of the
postcranial skeleton of P. pattersoni is present-
ed in the supporting online material.
Allocation of the specimens to P. pattersoni
is secured based on two diagnostic features of
the last upper molar (5): the narrowing of the
posteriormost portion at the level of the last
mm; width: 20.7 mm) and relative proportions
of this tooth. Based solely on tooth dimensions,
P. pattersoni is slightly smaller than P. insolita
and P. lozanoi, which have a M3 with a mesio-
distal length of 47 and 48 mm, respectively.
Phoberomys, together with the genera Neo-
epiblema and Eusigmomys, belongs to the fossil
Family Neoepiblemidae, distributed in Argenti-
species of Neoepiblemidae, cranial remains of
only Neoepiblema ambrosettianus have been
reported to date (7). This animal had a promi-
nent sagittal crest, absent in P. pattersoni. Based
on fragmentary dental remains, Phoberomys
(and therefore the neoepiblemids) has been clas-
sified either with the chinchillas and viscachas
(8), with the pakarana (9), or as the sister group
to both (10). We plotted a set of 13 postcranial
characters on a preexisting phylogenetic tree
based on molecular data and found that several
postcranial features support the association of
Phoberomys with the pakarana (Fig. 2). This
position for Phoberomys was the one that re-
quired the least number of steps.
P. pattersoni is reported to have been the
size of a rhinoceros (1, 11, 12). This rough
estimate, based on isolated teeth, can be
1Universita ¨t Tu ¨bingen, Spezielle Zoologie, Auf der
Morgenstelle 28, D-72076 Tu ¨bingen, Germany.2Uni-
versidad Nacional Experimental Francisco de Miranda,
CICBA, Complejo Docente Los Perozos, Carretera
Variante Sur, Coro, 4101, Estado Falco ´n, Venezuela.
3Department of Organismic Biology, Ecology, and
Evolution, 621 Young Drive South, University of Cal-
ifornia, Los Angeles, CA 90095–1606, USA.
*To whom correspondence should be addressed. E-
R E P O R T S
19 SEPTEMBER 2003VOL 301SCIENCE www.sciencemag.org
checked using the new postcranial material.
Estimation of body mass in Phoberomys has
two main limitations: We do not know what
kind of locomotion the animal performed (13),
and its body size was obviously an order of
magnitude larger than that of the largest extant
representatives of its group (14). Despite these
caveats, having available both femora and hu-
meri of the same specimen permits the calcu-
lation of a range of body mass. Femora and
humeri provide the most reliable estimates be-
cause they do not share weight-bearing func-
tions with other bones in their limb segments
(15). The body mass is estimated using predic-
tive equations based on anteroposterior diame-
ters of humeral and femoral diaphyses. The
equations are provided on the basis of data for
53 specimens representing 16 species of cavi-
omorphs showing different locomotor habits
(15). The anteroposterior diameter was mea-
sured at 35 and 65% from the distal end for the
humeral and femoral shafts, respectively. The
analysis yields body mass estimates of 436 kg
using the humerus and of 741 kg using the
Among caviomorphs and many other mam-
mals, femoral sections tend to have greater an-
of the same animal (15, 17). Phoberomys had a
gracile forelimb and a disproportionately robust
hindlimb. Tibia and femur are particularly ro-
bust—much more so in Phoberomys in relation
extant caviomorphs (18). It is likely that the
hindlimbs of Phoberomys played a more impor-
pattersoni. (A) Entire
array of elements of
Francisco de Miranda,
UNEFM-VF-020) in dif-
ferent views, collected
at Tı ´o Gregorio (11°
in the northern part of
the town of Urumaco.
Most of the skeleton is
preserved with the ex-
bones from the hands
and feet, the scapulae,
and the ribs. Thirteen
served, including the
atlas. (B) Additional
shattered partial skull
serving most of the
occipital and portions
of the basicranial re-
gion. Collected in El
Hatillo, sector Taparito
W). (C) Lingual and (D)
occlusal view of the left
dentary of UNEFM-VF-
020. (E to L) Miscella-
neous bones of UNEFM-
VF-020. (E) Left innom-
inate, lateral view; (F)
right femur, anterior
view; (G) right femur,
lus, dorsal view; (I) as-
tragalus, ventral view;
(J) humerus, flexor as-
pect; (K) radius; (L) right
ulna, anterior view. Ab-
breviations: an, astraga-
lar neck; ap, anconeal
crest; ef, ectal facet;
fm, foramen magnum;
gf, glenoid fossa; gt,
greater tubercle; mc,
medial condyle; mt, medial trochlea; mtr, medial trochlear ridge; p, palate; Rfm, Rectus femoris
muscle attachment; s, mandibular symphysis; sf, sustentacular facet. Bars: (A), 10 cm; (B) to (D), 5
cm; (E) to (L), 5 cm.
Fig. 2. Phylogenetic position of Phoberomys super-
imposed on a phylogeny of caviomorph rodents
29 character states were examined in 13 cavi-
omorphs. Relationships among taxa were based on
Phoberomys was added to that tree in several alter-
native positions, using the scaffold approach (25).
The morphological characters were optimized in
these different topologies. The most parsimonious
placement for Phoberomys was as sister group of
Dinomys (47 steps), three steps shorter than the
las and viscachas and indeed at least three steps
shorter than any other hypothesis. Based only on
dental traits, Phoberomys has been classified to-
gether with the chinchillas and viscachas, with the
pakaranas (Dinomys), or as sister group to both.
Several postcranial traits support the pakarana hy-
pothesis, represented in this tree: Rectus femoris
muscle attachment in pelvis forms an elongated
crest; medial and lateral ridges of femoral trochlea
convergent proximally; medial condyle wider than
lateral condyle in posterior view of femur; medial
ridge of astragalar trochlea protrudes posteriorly
further than lateral one; anconeal process of ulna
extends further cranially than coronoid process.
Some of these shared-derived character states of
Dinomys and Phoberomys evolved convergently in
other caviomorphs. See supplementary information
for a complete list of characters, the character ma-
trix, and a list of specimens examined.
R E P O R T S
www.sciencemag.orgSCIENCE VOL 30119 SEPTEMBER 2003
tant role in locomotor propulsion than the fore-
limbs, which were probably important in food
manipulation. Because of this, the body mass
estimation based on the femur is more reliable:
P. pattersoni probably weighed ?700 kg. With
Phoberomys, the size range of the order is in-
creased and Rodentia becomes one of the mam-
malian orders with the widest size variation,
second only to the Diprotodontia (kangaroos,
koalas, wombats, and possums) (fig. S1).
The fossil record of Caviomorpha is exten-
sive, with 140 fossil genera recognized in a
recent review (8), but no form competes with
Phoberomys in terms of size. Artigasia magna
from the upper Pliocene of Uruguay is reported
to be gigantic, but its lower teeth are only
?60% the size of those of P. pattersoni (19).
Artigasia, like most fossil rodents, is known
based only on dental and mandibular parts.
The paleoenvironment in which P. patter-
soni was found and the associated fauna indi-
cate that this rodent was either semiaquatic or
foraged in or near water, as capybaras do. P.
pattersoni had a deep and massive horizontal
ramus of the mandible, correlated with a high
degree of hypsodonty. Phoberomys clearly had
an abrasive diet, perhaps consisting of sea-
grasses. Potential predators could have been the
many crocodiles reported from Urumaco, in-
cluding some of the largest forms that ever
existed, such as Purussaurus spp. Contempo-
raries included Stupendemys geographicus, the
world’s largest turtle (20).
References and Notes
1. D. Starck, Lehrbuch der Speziellen Zoologie. Wirbelt-
iere. Teil 5: Sa ¨ugetiere (Gustav Fischer Verlag, Jena,
2. J. J. Flynn, A. R. Wyss, Trends Ecol. Evol. 13, 449
3. R. F. Kay, R. H. Madden, R. L. Cifelli, J. J. Flynn, Eds.,
Vertebrate Paleontology in the Neotropics. The Mio-
cene Fauna of La Venta, Colombia (Smithsonian In-
stitution, Washington, DC, 1997).
4. Le ´xico Estratigra ´fico de Venezuela (Ministerio de En-
ergı ´a y Minas, Boletı ´n de Geologı ´a, Caracas, ed. 3,
5. A. Mones, Ameghiniana 17, 277 (1980).
6. A. Mones, Comun. Paleontol. Mus. Hist. Nat. Montev.
2, 1 (1997).
7. F. R. Negri, J. Ferigolo, Bolet. Mus. Pare. Emı ´lio Goeldi
11, 1 (1999).
8. M. C. McKenna, S. K. Bell, Classification of Mammals
Above the Species Level (Columbia Univ. Press, New
9. S. O. Landry, Univ. Calif. Pub. Zool. 56, 1 (1957).
10. M. G. Vucetich, D. H. Verzi, J.-L. Hartenberger, C. R.
Acad. Sci. Ser. II Sci. Terre Planetes 329, 763 (1999).
11. L. Kraglievich, An. Soc. Cient. Argent. 114, 155
12. C. de Paula Couto, Tratado de Paleomastozoologia
(Academia Brasileira de Ciencias, Rı ´o de Janeiro,
13. B. Demes, W. L. Jungers, Folia Primatol. 52, 58
14. J. Bertram, A. A. Biewener, J. Morphol. 204, 157
15. A. R. Biknevicius , D. A. McFarlane, R. D. E. MacPhee,
Am. Mus. Novit. 3079, 1 (1993).
16. Predictive equations for body size (15): log W ? log
a ? b (log AP), where W is body mass (in kilograms),
log a is intercept, b is slope, and AP is the antero-
posterior diameter of the bone examined. Anteropos-
terior proximal femur diameter (APF): log W ?
?1.678 ? 2.518 (1.80618), W ? 741.1; anteropos-
terior distal humerus diameter (APH): log W ?
?1.467 ? 2.484 (1.6532), W ? 436.1 kg.
17. A. R. Biknevicius, J. Mammal. 74, 95 (1993).
18. The humerus/femur length ratio (H/F) and the (humer-
us ? radius)/(femur ? tibia) length ratio [(H ? R)/(F ?
T)] in P. pattersoni (0.76 and 0.78, respectively) are
average compared with those of other caviomorphs. For
a sample of 17 extant caviomorphs, the mean values ?
SD were H/F ? 0.80 ? 0.08 and (H ? R)/(F ? T) ?
0.74 ? 0.09. In the sample, there are no marked trends
associated with growth or phylogeny (21). On the other
hand, the ratios between femur versus humerus cross-
sectional diameters (APF/APH) (15) show that the hind-
limbs of P. pattersoni are robust. APF/APH is 1.42,
whereas the average ? SD for a sample of 19 cavi-
omorph species (21) is 1.27 ? 0.18. Robust hindlimbs in
comparison to forelimbs characterizes also the clade
composed of Dinomys, Chinchilla, and Lagostomus
(mean ? SD 1.40 ? 0.26), the closest relatives to
Phoberomys among extant caviomorphs.
19. J. C. Francis, A. Mones, Kraglieviana 1, 89 (1966).
20. R. C. Wood, Breviora 436, 1 (1976).
21. M. R. Sa ´nchez-Villagra, O. Aguilera, I. Horovitz, un-
22. R. M. Nowak, Walker’s Mammals of the World (John
Hopkins Univ. Press, Baltimore, ed. 6, 1999).
23. D. Huchon, J. P. Douzery, Mol. Phylogenet. Evol. 20,
24. We added Lagostomus to the tree to increase the
relevant sampling in our scaffold analysis. All rel-
evant treatments of caviomorph taxonomy and
Amazonia 1492: Pristine Forest
or Cultural Parkland?
phylogeny place Lagostomus together with Chin-
25. M. S. Springer et al., Proc. Natl. Acad. Sci. U.S.A. 98,
26. We thank J. Bocquentin, A. Ranci, A. Rinco ´n, J. Reyes,
D. Rodrigues de Aguilera, and R. Sa ´nchez for help with
fieldwork; J. Reyes and E. Weston for laboratory work;
E. Weston and three anonymous reviewers for com-
ments on the manuscript; O. Aguilera Jr. for assist-
ance with digital imaging; S. Melendrez for recon-
struction of the skeleton of Phoberomys in Fig. 2; D.
Mo ¨rike (Stuttgart) and E. Weber (Tu ¨bingen) for ac-
cess to collections; and J. Bocquentin and A. Ranci for
preliminary work on the identification of the giant
rodent. Work in Venezuela by M.R.S.-V. was partially
supported by the National Geographic Society and
the University of Tu ¨bingen. The Smithsonian Tropical
Research Institute and the Universidad Nacional Ex-
perimental Francisco de Miranda (UNEFM) supported
the field and laboratory work of O.A. O.A. is a Re-
search Associate of the Smithsonian Tropical Re-
Supporting Online Material
Tables S1 to S3
6 May 2003; accepted 6 August 2003
Michael J. Heckenberger,1* Afukaka Kuikuro,4
Urissapa ´ Tabata Kuikuro,4J. Christian Russell,2
Morgan Schmidt,3Carlos Fausto,5Bruna Franchetto5
Archaeology and indigenous history of Native Amazonian peoples in the Upper
Xingu region of Brazil reveal unexpectedly complex regional settlement pat-
terns and large-scale transformations of local landscapes over the past mil-
lennium. Mapping and excavation of archaeological structures document pro-
nounced human-induced alteration of the forest cover, particularly in relation
to large, dense late-prehistoric settlements (circa 1200 to 1600 A.D.). The
findings contribute to debates on human carrying capacity, population size and
settlement patterns, anthropogenic impacts on the environment, and the im-
portance of indigenous knowledge, as well as contributing to the pride of place
of the native peoples in this part of the Amazon.
Was the Amazon a natural forest in 1492,
sparsely populated and essentially pristine, as
has been traditionally thought? Or, instead,
were parts of it densely settled and better
viewed as cultural forests, including large
agricultural areas, open parklands, and work-
ing forests associated with large, regional
polities (1–3). Despite growing popularity for
the latter view (4–6), entrenched debates re-
garding pre-Columbian cultural and ecologi-
cal variation in the region remain unresolved
due to a lack of well-documented case studies
(7, 8). Here, we present clear evidence of
large, regional social formations [circa (c.)
1250 to 1600 A.D.] and their substantial in-
fluence on the landscape, where they have
altered much of the local forest cover. Spe-
cifically, archaeological research in the Up-
per Xingu (Mato Grosso, Brazil), including
detailed mapping and excavations of exten-
sive earthen features (such as moats, roads,
and bridges) in and around ancient settle-
ments, reveals unexpectedly complex region-
al settlement patterns that created areas of
acute forest alteration.
The Upper Xingu is unique in the south-
ern peripheries of the Amazon as the larg-
est contiguous tract of tropical forest still
1Department of Anthropology,2Land-Use and En-
vironmental Change Institute,3Department of Ge-
ography, University of Florida, Gainesville, FL
32611, USA.4Associac ¸a ˜o Indı ´gena Kuikuro do Alto
Xingu, Parque Indı ´gena do Xingu, Mato Grosso,
Brazil.5Department of Anthropology, Museu Nacio-
nal, Universidade Federal do Rio de Janeiro, Quinta
da Boa Vista, Rio de Janeiro 20940–040, Brazil.
*To whom correspondence should be addressed. E-
R E P O R T S
19 SEPTEMBER 2003VOL 301SCIENCE www.sciencemag.org