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Proc Natl Acad Sci U S A. 2000 March 14; 97(6): 2646–2651. Published online 2000 February 29. | PMCID: PMC15983 |
Copyright © 2000, The National Academy of Sciences Evolution Widanelfarasia, a diminutive placental from the
late Eocene of Egypt Erik R. Seiffert* and Elwyn L. Simons*†‡ *Department of Biological Anthropology and Anatomy, Duke University, Box 90383, Durham, NC 27708-0383; and †Primate Center, Duke University, 3705 Erwin Road, Durham, NC 27705 Accepted December 15, 1999. The lower dentition of Widanelfarasia (new genus), a
diminutive late Eocene placental from the Fayum Depression in Egypt, is
described. Widanelfarasia exhibits a complex of features
associated with incipient zalambdodonty and at least three unequivocal
apomorphies [loss of P1, an enlarged I2
(relative to I3), and a basal cusp on I2],
which provide weak support for its placement as a possible sister taxon
of either a tenrecid–chrysochlorid clade or of solenodontids. The
former hypothesis gains additional support from biogeographical
evidence, but both scenarios are currently tenuous as
Widanelfarasia is clearly not truly zalambdodont.
Phylogenetic hypotheses positing affinities with tenrecids alone or
chrysochlorids alone must invoke either convergent acquisition of
zalambdodonty in these taxa or autapomorphic reversal in
Widanelfarasia. Given these considerations, a
relationship with more generalized taxa from the Laurasian Paleogene
(e.g., geolabidids, nyctitheriids, leptictids) cannot yet be ruled out.
Comparisons with other Paleogene Afro-Arabian forms are generally
inconclusive. A relationship with the earlier Eocene
Chambilestes from Tunisia—currently represented by a
single specimen preserving P4–M3—seems
possible based on the geometry and predicted occlusal relationships of
these teeth, but cannot be confidently determined until these two taxa
come to be represented by common diagnostic elements.
Todralestes (late Paleocene, Morocco) exhibits general
phenetic similarities to Widanelfarasia, but it is not
yet known whether this taxon shares any of
Widanelfarasia's unequivocal dental apomorphies.
Pending the recovery of more informative material, we tentatively refer
Widanelfarasia to Placentalia incertae
sedis. Truly zalambdodont placentals remain conspicuously
absent from the Paleogene of Afro-Arabia. Recent paleontological discoveries from the Cretaceous
( 1– 4) and early Paleogene ( 5– 10) of Morocco indicate that Afro-Arabia
served as an important center for the early diversification of various
mammaliaforms, including eutherians. § The evolution
of primitive placentals of “insectivoran” grade remains poorly
documented on this continent before the early Miocene, however, and
only within the last decade have such mammals been described in any
detail; most taxa are still represented almost entirely by isolated
teeth. Eutherians formally or informally allocated to Lipotyphla [a
potentially para- or polyphyletic assemblage (e.g., ref. 12)
conventionally defined to include a crown clade of extant erinaceids,
soricids, talpids, tenrecids, chrysochlorids, and
Solenodon] have been recovered from five Paleogene
localities on the Afro-Arabian plate—the Ouarzazate Basin [late
Paleocene, Morocco ( 5– 9)], El Kohol [early(?) Eocene, Algeria
( 13)], the Fayum Depression (late Eocene–early Oligocene, Egypt),
Chambi [early(?) Eocene, Tunisia ( 14)], and Taqah [early
Oligocene(?), Oman ( 15)]. As yet, Gheerbrant ( 9) has assigned the
Moroccan Paleocene adapisoriculid Afrodon and possible
representatives of Adapisoriculus and Garatherium
to Lipotyphla with a query, as have Gheerbrant and Hartenberger ( 14)
with Chambilestes, a newly described form from the Eocene of
Tunisia; Mahboubi et al. ( 13) have noted similarities of a
species from El Kohol designated “Lipotyphla indet.” to Laurasian
geolabidids and nyctitheriids. A number of cimolestans or
“proteutherians” of Laurasian affinities
( Palaeoryctes, Cimolestes,
Aboletylestes, indeterminate didelphodontines) as well as a
possible endemic form referred to Proteutheria, Todralestes,
have also been described from the Ouarzazate Basin ( 5, 7,
8). These diminutive north African eutherians have provided new evidence
for the presence of intermittent biogeographical connections between
Afro-Arabia and Laurasia during the early Cenozoic ( 16) and have helped
to elucidate a considerable degree of biogeographical cosmopolitanism
for palaeoryctoids through the late Cretaceous and early Paleogene
(e.g., ref. 17). Due to the limited nature of the available material,
however, it remains unclear just how the scarce Eocene Afro-Arabian
“lipotyphlans” may relate to living and extinct Laurasian forms
or to the extant tenrecs and golden moles—two groups whose fossil
record appears to extend back only to the early Miocene ( 18), but which
are generally considered to have had a long history of endemic
evolution on the Afro-Arabian land mass. Here we report on the lower
dentition of a late Eocene placental from the Fayum Depression which
may prove to have a direct bearing on these issues. Mammalia Linnaeus 1758. Placentalia incertae sedis Owen 1837.
Widanelfarasia, new genus. Type species:
Widanelfarasia bowni, new species. Age and distribution:
Late Eocene, Jebel Qatrani Formation, Fayum Depression, Egypt. Diagnosis. Differs from tenrecids, chrysochlorids, and other zalambdodont
placentals (e.g., solenodontids, apternodontids) in having
mesiodistally longer and buccolingually broader talonid basins on
M 1–M 3 with three talonid
cusps; the hypoconid is relatively well developed. Further differs from
solenodontids in having a smaller I 2 with a
pronounced posterior basal cusp, a presumably more caniniform canine,
slightly more mesially oriented protoconids on
P 2–P 3, and larger and more
bulbous paraconid on P 4, and from apternodontids
in having a relatively large I 2 with posterior
basal cusp, less upright and complex P 3,
P 4 less molariform and less compressed
mesiodistally, no distal decrease in size or height of molars. Differs
from most North American geolabidids in having a relatively large
I 2 with a posterior basal cusp [as opposed to
the bilobed condition of I 2 in
Centetodon ( 19)], loss of P 1, lower
and more distally placed metaconid on P 4, bulbous
and somewhat more mesially oriented paraconid on
P 4, well developed precingulid on
P 4, slightly less crestiform cusps on lower
molars, cristid obliqua which contacts the distal wall of trigonid at
or slightly lingual to the metaconid–protoconid notch, slightly more
defined entoconid on
M 1–M 3,
M 3 as large as M 1 and
M 2. Differs from Laurasian nyctitheriids in
having a relatively large I 2 with a single basal
cusp, a presumably larger and more caniniform canine, loss of
P 1, taller, less mesially oriented, and more
upright premolars, shorter, narrower, and somewhat lower-crowned molar
talonids with less sharply defined talonid cusps, taller and slightly
more lingual paraconids on
M 1–M 3, relatively tall
protoconids on all molars (highest on M 3), less
disparity in relative height of paraconids and metaconids, relatively
larger P 4 with a taller protoconid. Differs from
Micropternodus in the loss of P 1,
having less mesiodistally compressed premolars, a well developed
talonid on P 4, and less recumbent protoconids on
P 4–M 3. Differs from
Butselia most notably in having little or no size decrease
from M 1–M 3, loss of
P 1, a two-rooted P 2, larger
paraconid on P 4, and slightly less lingual
paraconids on molars. Differs from Todralestes in having a
stronger precingulid and a lower, more bulbous, and more mesially
oriented paraconid on P 4 as well as more mesially
placed metaconids on P 4–M 3
(and thus more labiolingually oriented protocristids). Differs from
adapisoriculids such as Afrodon in the loss of
P 1, having a larger paraconid on
P 4, more acute paracristid–protocristid angle on
molars, and a more mesially placed metaconid and buccolingually
oriented protocristid as well as more pronounced precingulids and
narrower talonids. Differs from most cimolestans (e.g., pantolestids,
cimolestids) in the loss of P 1 (occurs in
palaeoryctids) and in having a semimolariform P 4.
Differs from leptictids in having a relatively large
I 2, loss of P 1, shorter and
narrower talonids, and deeper hypoflexids. Etymology. The genus is named for Widan el Faras, two hills which stand as a
prominent geological feature in the Fayum Depression and which are
capped by the Widan el Faras basalt. The name is Arabic for “ears of
the mare.” Widanelfarasia bowni, New Species. Holotype. Duke University Primate Center (DPC) 15637, a right dentary preserving
P2–M3 and complete ascending ramus, condyle,
and angular process (Fig.
A, C, and G).
Hypodigm. The type specimen; DPC 17106, a right dentary preserving
P4–M3 and complete
ascending ramus; DPC 17779, a left dentary containing
P2–P4,
I2, and the roots of the lower canine and
I3; Cairo Geological Museum (CGM) 41878, a left
dentary containing P3–M3. Locality and distribution. Quarry L-41, Late Eocene, Jebel Qatrani Formation, Fayum Depression,
Egypt. Diagnosis. Same as for genus. Description. DPC 17779 (Fig. F) preserves the crown of
I2 and the root of I3.
I2 preserves a posterior basal cusp, and the
relative sizes of the roots of these teeth indicate that
I2 is larger than I3. This
specimen also preserves a single oval and somewhat procumbent canine
root that is separated from P2 by a diastema
(suggesting the possible presence of a large upper canine). P2 is a two-rooted tooth with a mesially oriented
protoconid, a very weak anterobasal cusp, and a stronger distal cusp.
P3 is morphologically similar to
P2 but is slightly larger and separated from
P2 by a short diastema (it is likely that the
crowding of these teeth in DPC 17779 is due to distortion; Fig.
F). P4 is separated from
P3 by a short diastema and is semimolariform,
with a short talonid preserving a small entoconid and a more distal
hypoconulid. The metaconid is unworn on DPC 17779 and is clearly
intermediate in height between the bulbous and mesially oriented
paraconid and the slightly more mesially placed protoconid. The
P4 protoconid is as high as or higher than the
protoconids on M1–M3. The
protoconids of P4–M3 are
all somewhat labially convex, with this trend reaching its greatest
extreme on M3. The lower molars are subequal in size. The protoconid is generally
about two and a half times as high as the hypoconid on
M1–M3 (highest on
M3), and the hypoconid is in turn somewhat
elevated relative to the entoconid. This differential height
relationship of the talonid cusps leads the entire talonid basin to be
somewhat lingually canted in distal view. Molar paraconids are all
oriented slightly labial to the metaconids and are elevated well above
the talonid cusps of the mesially adjacent tooth on
M1–M3. The roughly
labiolingual orientation of the protocristids and slightly more oblique
orientation of the paracristids leads to a fairly acute conformation of
the trigonid cusps, similar to that seen in the geolabidid
Centetodon. As is often the case in dentally primitive
eutherians, this angle becomes more acute distally, reaching its
greatest extreme on M3. The metaconid is taller
than the paraconid on all molars. The talonids are about one-half to
two-thirds the length and about two-thirds to three-fourths the width
of the trigonids on all molars and preserve three cusps, with the
centrally placed hypoconulid being consistently more distal than the
entoconid and hypoconid. The cristid obliqua runs mesiolingually to
contact the distal trigonid wall at approximately the point of the
metaconid–protoconid notch. Precingulids are present on all molars. Mandibular condyle is transversely elongate and is positioned at or
slightly above the occlusal surface of the lower teeth. Coronoid
process is tall, rising at an angle of about 70° from the long axis
of the dentary. Masseteric fossa tends to be well developed. Angular
process is long and distinct, protruding almost as far caudally as the
condyle. Position of the mental foramen varies. Etymology. The species is named for Thomas M. Bown, who has made so many important
contributions to our understanding of the geology, paleoenvironment,
and vertebrate paleontology of the Jebel Qatrani Formation and who
first discovered quarry L-41 with Mary J. Kraus. Widanelfarasia rasmusseni, New Species. Holotype. DPC 17427, a right dentary containing P2,
P4–M3, and alveoli for P3, the
canine and I3 (Fig. E and
H). Hypodigm. The type specimen; DPC 17396, a left dentary containing
P3–M3. Locality and distribution. L-41, Late Eocene, Jebel Qatrani Formation, Fayum Depression, Egypt. Diagnosis. Same as for genus; differs from W. bowni in being much
smaller (about 60% the size of W. bowni based on dental
measurements), with slightly narrower talonids on
M2–M3, particularly on
M3. Description. Very similar to W. bowni in almost all respects; the
alveolus anterior to P2 is relatively large
(quite a bit larger than the I3 alveolus),
suggesting that W. rasmusseni had a lower canine of
approximately the same relative size as that seen in W.
bowni. The dentary of the holotype has two major cracks, one
between the canine alveolus and P2 and one
through the P2 itself. The anterior half of this
tooth has been twisted out of place, giving the
P2 the superficial appearance of being two small
teeth. Etymology. The species is named for D. Tab Rasmussen, in recognition of his many
important contributions to our understanding of the vertebrate
paleontology and paleoenvironment of the Fayum Depression. Among Paleogene eutherians, the geometry of
Widanelfarasia's lower molars (and, in most cases,
P 4) exhibits the greatest resemblance to certain
geolabidids, nyctitheriids, leptictids, and cimolestans, as well as
more enigmatic forms such as the possible plesiosoricid
Butselia and the late Paleocene Todralestes from
Morocco. At present it is very difficult to determine, however, how
many of the various similarities shared by these taxa are simply
primitive features of the crown group Placentalia. As has been noted
many times in the past (e.g., refs. 20– 23), the polarity of dental
characters in primitive Cretaceous and Paleogene eutherians is often
ambiguous, and a healthy respect for homoplasy must lead to
considerable caution when drawing phylogenetic interpretations from
such material (particularly from teeth that tend to lack strong
diagnostic features). As an exhaustive cladistic analysis of the
available lower teeth of Widanelfarasia would be replete
with characters of uncertain polarity, we feel that such an exercise is
not yet likely to produce many compelling clues as to this taxon's
true affinities. Furthermore, consideration of lower dental material
alone fails to reflect the strong possibility (based on other
morphological and molecular lines of evidence) that many striking
dental apomorphies shared by higher taxa (e.g., those between Caribbean
Solenodon and the Afro-Malagasy zalambdodonts) are not due
to common ancestry (see discussion below). Thus, a brief consideration
of Widanelfarasia's few clearly derived features might be
positively supplemented to a greater extent by consideration of other
sources of data, including patterns of Paleogene biogeography and new
molecular data bearing on the interrelationships of extant taxa
traditionally placed in Lipotyphla. Widanelfarasia exhibits three features of the
antemolar dentition [loss of P 1, an enlarged
I 2 (relative to I 3), and a
posterior basal cusp on I 2] which are
unequivocally derived within Eutheria. None of these characters provide
particularly strong evidence for relationships at higher taxonomic
levels, however. The loss of P 1 is not at all
rare among “lipotyphlans” and other eutherians of relevance to
this study, but retention of P 1 can often be
observed in the close living or extinct relatives of those taxa which
have lost the tooth, indicating that its loss in various taxa is
generally only derived within some lower-level group (and, in most
cases, was clearly lost after the acquisition of other apomorphies not
seen in Widanelfarasia). For instance, while certain crown
erinaceids have lost premolars (including P 1), it
is evident from various other living and extinct erinaceids that
retention of four premolars is a primitive feature within that clade
and that premolar loss occurred in certain taxa only after the
appearance of crown erinaceid synapomorphies (see, e.g., ref. 24). The
same can be said of the common node of the talpid–soricid clade; as
Widanelfarasia does not exhibit any of the probable dental
synapomorphies of this clade (e.g., well developed dilambdodonty), a
close relationship with these taxa does not seem
likely. Tenrecids, chrysochlorids,
solenodontids, and the subfossil nesophontids have all lost
P 1, and all of these taxa share a similar pattern
of premolar loss with Widanelfarasia in that
P 2 remains two-rooted and premolars are
occasionally separated by diastemata (as in W. bowni). Among
relevant Paleogene taxa, Butselia, nyctitheriids,
leptictids, and most geolabidids and cimolestans retained
P 1, but this tooth was lost in apternodontids [a
group which may also be closely related to the solenodontids (e.g.,
ref. 25)], in palaeoryctid palaeoryctoids such as
Aaptoryctes ( 26) and Eoryctes ( 27), and, among
geolabidids, in certain species of Centetodon ( 28).
Schlaijker ( 25) suggested that Micropternodus borealis had
lost P 1, but various authorities ( 29– 31) have
challenged this assertion; regardless, the affinities of
Micropternodus arguably lie with Asian forms such as
Sarcodon, Prosarcodon, Sinosinopa, and
Carnilestes (refs. 32 and 33, but see also ref. 34), all of
which primitively retain P 1. It is not yet known
whether the Afro-Arabian todralestids retained
P 1. An enlarged I 2 is seen in Solenodon,
but not in Nesophontes [arguably one of
Solenodon's closer relatives (e.g., 31, 33)], which has
bilobed incisors of subequal size. A trend toward subequal
polycuspidate incisors is also seen among geolabidids ( 19) and
nyctitheriids ( 35), but it is not yet clear whether this morphology is
derived from the sort of pattern seen in Widanelfarasia,
chrysochlorids, and many tenrecids, which exhibit an enlarged
I 2 relative to I 3 with a
basal cusp. Crown soricids have enlarged incisors of uncertain
homology, but this apomorphy clearly appeared after the talpid–soricid
clade acquired various dental specializations which
Widanelfarasia lacks. Butselia ( 36),
Plesiosorex ( 37), the palaeoryctids Palaeoryctes
( 26, 38), Aaptoryctes ( 26), Eoryctes ( 27), and
possibly Naranius ( 39) all have an enlarged
I 2 relative to I 3;
apternodontids show a reversal of this trend in that
I 2 is markedly reduced ( 31).
Micropternodus has a slightly enlarged
I 2, but more primitive micropternodontids such as
Prosarcodon and Carnilestes have somewhat
spatulate incisors of approximately equal size, with
I 2 being only slightly larger than
I 3 ( 32, 34). This pattern is also seen among
various leptictids (e.g., ref. 21) and many of the controversial
“erinaceomorphs” [e.g., amphilemurids ( 40)], although
Litolestes [an erinaceid according to Novacek ( 24); a
possible dormaalid according to Butler ( 33)] has subequal trilobed
incisors ( 41), and the sespedectine Proterixoides has an
I 1 and I 2 that are enlarged
relative to I 3 ( 42). Lower incisors of
Todralestes have not yet been discovered. These comparisons indicate that Widanelfarasia's three
unambiguously apomorphic dental features can only be matched by
tenrecids, chrysochlorids, solenodontids (variably), and possibly
palaeoryctids among the living and extinct eutherians considered. If
other features of Widanelfarasia's dentition are apomorphic
within Eutheria (e.g., semimolariform P 4),
support rises for a relationship with the extant zalambdodonts to the
exclusion of palaeoryctids, which generally have a relatively simple
P 4. Other potentially derived features of
Widanelfarasia are related to a pattern of incipient
zalambdodonty which is also observable in other Paleogene taxa such as
Butselia and various geolabidids. These forms tend to
exhibit taller trigonids, relatively short and narrow talonids, deep
hypoflexids (which accommodate a relatively large occluding paracone),
well developed precingulids, and taller, more prominent (and more
lingually placed) paraconids. Some or all of these features are
exaggerated in true zalambdodonts such as the living tenrecids,
chrysochlorids, and solenodontids and the extinct apternodontids, all
of which have enlarged the paracone and lost the metacone on the upper
molars [with the exception of the tenrecid Potamogale,
whose small metacone is likely to be secondarily acquired (e.g., ref.
31)]. The polarity of the features associated with this pattern of
incipient zalambdodonty are admittedly still unclear, however, due in
part to the presence of some of these features in various cimolestans.
Given these considerations, it can only be said with confidence that
Widanelfarasia exhibits at least three apomorphic characters
in the antemolar dentition and a suite of features in
P 4–M 3 that are more
similar to dental patterns seen in certain lipotyphlan-grade placentals
than in most “proteutherians,” and that the distribution of
Widanelfarasia's derived (and potentially derived) features
among the former taxa most clearly supports (albeit weakly) affinities
with either tenrecids, chrysochlorids, or solenodontids—all of which
are, however, highly derived in being truly zalambdodont. Various studies over the last half-century ( 31, 33, 36) have rejected
the monophyly of living and extinct zalambdodont placentals and have
supported a close relationship between Solenodon and the
subfossil Caribbean dilambdodont Nesophontes (Fig.
C), but there has been little consensus as to whether these
latter taxa should be placed as sister to soricids (e.g., ref. 31) or
to a talpid–soricid clade (e.g., ref. 33). Most recently, Asher ( 43)
presented multiple phylogenetic analyses of morphological data which
tended to support a clustering of solenodontids, apternodontids, and
the Afro-Malagasy zalambdodonts to the exclusion of other
“lipotyphlans.” Clearly, there is morphological support for
various phylogenetic scenarios and, until recently, very little new
data which could aid the resolution of this debate.
Importantly, the difficulties associated with phylogenetic analysis of
living and extinct eutherian “insectivores” have been further
compounded in recent years by molecular data which strongly suggest
that Lipotyphla is para- or polyphyletic (e.g., ref. 12). Various
nuclear and mitochondrial genes have supported a supraordinal clade of
tenrecs, golden moles, elephant shrews, aardvarks, and paenungulates
(“Afrotheria”) ( 12, 44, 45) and a tenrecid–chrysochlorid clade
within Afrotheria for which Stanhope et al. ( 12) erected the
new order “Afrosoricida.” These data also suggest that
Solenodon joins talpids and soricids in a distantly related
clade ( 12), but the position of erinaceids is less clear ( 46). These
results clearly conflict with morphological studies supporting the
monophyly of Lipotyphla ( 33, 47), as well as recent endorsements ( 47,
48) of earlier suggestions ( 49– 51) that chrysochlorids and tenrecids
do not share an exclusive relationship and that golden moles should be
placed in their own order or suborder. We opt to support phylogenetic hypotheses which receive
reasonable support from morphological, molecular, and biogeographical
data. Thus, we suggest that the association of Solenodon
with the soricid–talpid clade already proposed on the basis of
morphological evidence (and now supported by limited molecular
evidence) is more likely to be correct than an association with the
Afro-Malagasy zalambdodonts. Evidence for this
solenodontid–soricid–talpid radiation can be found in the Laurasian
fossil record, although it is not yet clear how or to what extent
various geolabidids, plesiosoricids, nesophontids, apternodontids, or
nyctitheriids might be involved. Regardless, this combined evidence
indicates to us that the dental features of Solenodon are
likely to be convergent on those of tenrecids and chrysochlorids, and
that Solenodon and the Afro-Malagasy zalambdodonts are
independently descended from more generalized forms which may have had
dentitions similar to geolabidids and Widanelfarasia,
respectively. This hypothesis is somewhat similar to that proposed by
Butler ( 33), who suggested that an early African “nyctitheriid”
branch gave rise to the tenrecid–chrysochlorid clade. Although it has long been clear that faunal interchange between
Afro-Arabia and northern continents was possible during the Eocene, the
highly endemic nature of the Paleogene Afro-Arabian mammal fauna [as
indicated directly by paleontological data ( 16) and indirectly by
molecular data ( 12, 44, 45, 52)] provides supplementary evidence
suggesting that the presence of a late Eocene Afro-Arabian
taxon— Widanelfarasia—sharing apomorphic dental features
with the endemic Afro-Arabian tenrecid–chrysochlorid clade is more
likely to be a consequence of some phylogenetic relationship between
the two groups than of an appearance by an otherwise endemic Laurasian
form which coincidentally evolved the same apomorphic features
convergently. As Widanelfarasia is not truly zalambdodont,
however, this suggestion is not without its problems. Dental convergence in tenrecids and chrysochlorids is a possibility
which has been suggested (e.g., ref. 47), but for which there has, as
yet, been little or no fossil evidence. It is a difficult hypothesis to
test as the dentition of chrysochlorids is highly autapomorphic and
possibly derived from a dental pattern resembling the zalambdodont
morphotype of the extant tenrecids. As there is no known fossil record
for tenrecids or chrysochlorids prior to the early Miocene, there is
also little indication of a more conservative stage in either group's
ancestry [although early Miocene Prochrysochloris exhibits
longer and more complex talonids and less molariform premolars than do
crown chrysochlorids, and the contemporaneous tenrecid
Protenrec retains a small metacone ( 18)]. The combined
morphology, antiquity, and biogeographical provenance of
Widanelfarasia raises the possibility that the dental
similarities of tenrecids and chrysochlorids evolved convergently from
what may have been an incipiently zalambdodont common ancestor.
Considering the apparent reversal to tribospheny seen in extant
Potamogale, however, it is, of course, entirely possible
that (among other scenarios) Widanelfarasia is a tenrecid
which exhibits a similar reversal from ancestral zalambdodonty. The limited nature of the available material leaves open many
other interesting phylogenetic options, including a possible
relationship with the recently described Chambilestes ( 14)
from the earlier Eocene of Tunisia (currently represented only by
P 4–M 3). From what little
can be determined based on the geometry and predicted occlusal
relationships of these upper teeth, the morphology of
Chambilestes does not appear to be entirely inconsistent
with the lower dentition of Widanelfarasia. As
Widanelfarasia exhibits relatively short and narrow talonids
with well developed hypoconids on
M 1–M 3, and
Chambilestes exhibits transversely elongate upper molars
with well developed paracone and (reduced) metacone, the morphology of
the Tunisian form certainly more closely approximates the predicted
upper molar morphology of Widanelfarasia than does any known
living or extinct tenrecid or chrysochlorid. In light of
Widanelfarasia's antemolar specializations, however, an
allocation of Widanelfarasia to the Chambilestidae would be
at odds with Gheerbrant and Hartenberger's ( 14) suggestion that
Chambilestes may be a primitive erinaceomorph. Clearly, much
more complete material will be needed before the higher-level
relationships of Afro-Arabian forms such as Widanelfarasia,
Chambilestes, and Todralestes can be confidently
resolved, but it is entirely possible that these taxa are all more
closely related to each other than to any known Laurasian group. Until
more informative material becomes available, we prefer to tentatively
refer Widanelfarasia to Placentalia incertae
sedis. This taxonomic decision is conservative, but we believe
that it more accurately reflects current understanding of the true
relationships of various extinct placentals traditionally placed in
unstable taxa such as Insectivora or Lipotyphla. We thank C. V. M. Simons for helpful discussion as well
as editorial and research assistance and R. J. Asher, P. D.
Gingerich, and J. G. M. Thewissen for providing a number of
helpful comments and criticisms on earlier versions of this manuscript.
The opinions expressed in this paper are, however, entirely those of
the authors. We also thank L. Gordon and M. Carleton for access to
specimens at the National Museum of Natural History; M. Godinot, E.
Gheerbrant, and C. Berge for discussion, hospitality, and access to
fossil material at the Muséum National d'Histoire Naturelle
Institut de Paléontologie; and J.-J. Jaeger, S. Ducrocq, Y.
Chaimanee, J. Sudre, and B. Marandat for discussion and hospitality
while in Montpellier. Funds in support of this project have come from
the U.S. National Science Foundation (BNS-91-08445 and SBR-95-07770) as
well as from the Boise Fund, Oxford University, Gordon and Ann Getty,
Margot Marsh, and Verna C. Simons. Specimens were prepared by P.
Chatrath and D. DeBlieux. Scanning electron microscopy photos were
taken by L. Eibest. This is DPC publication no. 697. | | DPC | Duke University Primate Center | | | CGM | Cairo
Geological Museum |
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