Eugnamptus proterus, n. sp. (Coleoptera: Curculionoidea : Rhynchitidae), a tooth-nosed snout beetle in mexican amber

2007·2.8 MB·

by  George Poinar

PROC. ENTOMOL. SOC. WASH.
109(4), 2007, pp. 880-885
EUGNAMPTUS PROTERUS, N. SP. (COLEOPTERA: CURCULIONOIDEA:
RHYNCHITIDAE), A TOOTH-NOSED SNOUT BEETLE IN
MEXICAN AMBER
George Poinar, Jr. and Alex E. Brown
OR
(GP) Department of Zoology, Oregon State University, Corvallis, 97331,
U.S.A. (e-mail: [email protected]); (AEB) 629 Euclid Avenue,
CA
Berkeley, 94708, U.S.A.
—
Abstract. a new species oftooth-nosed snout beetle, Eugnamptusproterus Poinar
and Brown (Coleoptera: Curculionoidea: Rhynchitidae) is described from Mexican
amber. Distinguishing characters include 1) the next to last strial row joins the last
strial row near the middle ofthe elytra, 2) the presence ofa median longitudinal ridge
on the rostrum, 3) long, slender, erect dark setae on the frons, 4) a narrow,
cylindrical prothorax and extended "neck" region and 5) unusually broad claw
appendages. Based on the available literature, the closest described extant species is
A
the Japanese E. awifrons Roel. brief survey of fossil rhynchitids is presented.
Key Words: Eugnamptusproterus, Rhynchitidae, Curculionoidea, Mexican amber
Thetooth-nosedsnoutbeetles (Rhynch- Hymenaea mexicana (Fabaceae) (Poinar
itidae), often considered a subfamily of and Brown 2002) and occurs in lignitic
the leaf-roller weevils (Attelabidae), are a beds among sequences ofprimarilymarine
primitive group that Zimmerman (1994) calcareous sandstones and silt. The amber
assigned to his "convenience" Division is associated with Balumtun Sandstone of
Orthoceri based on their non-geniculate, the early Miocene and the La Quinta
straight antennae. There are over 1,000 formation of the Late Oligocene with
described species in 49 genera, and while radiometric ages from 22.5 to 26 million -
the range is cosmopolitan, most taxa are years (Berggren and Van Couvering 1974).
restricted to the warmer portions of the Since the amberis secondarilydeposited in
globe (Zimmerman 1994; Kuschel 1995; these marine formations, it is somewhat
Thompson 1992; Voss 1941). older than the above dates.
The present study describes a represen- The piece of amber containing the
mm mm
tative of this group in Mexican amber. fossil is 11 long, 5 wide and
mm
4 deep. The body length measure-
ment was a direct line from the tip ofthe
Materials and Methods
elytra to the anterior border of the eyes
The specimen was obtained from an (excluding the rostrum). Body width was
amber mine in the Simojovel area of taken at the widest part of the elytra,
Chiapas, Mexico. Locations of the Chia- head length was measured as the portion
pas mines and a synopsis of Mexican of the head bordered by the eyes, head
amber are presented in Poinar (1992). width at the widest point between the
Amber from this region was produced by eyes, frons width was the head width at
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109, 4 881
the midpoint ofthe eyes, neck length was Thorax: Pronotum cylindrical, longer
measured from the posterior border of than wide, widest at middle; with four
the eyes to the anterior collar of the irregular longitudinal rows of medium-
pronotum, and head- eye width was the to large- sized puncta; legs elongate, all
distance from the outer rim of one eye terminated by paired pointed claws with
across the head to the outer rim of the unusually broad appendages at bases.
opposite eye. All measurements are in Abdomen: First ventral suture not
mm
unless otherwise specified. distinctly impressed throughout; elytra
The specimen is complete and well long and narrow (2 Vi times longer than
preserved. In the same piece ofamber are wide), widest near declivities, lacking
an oribatid mite, an adult gall gnat noticeable spots; with rows of small
(Diptera: Cecidomyidae) and a worker puncta; next to last strial row joins last
ant of the genus Azteca (Hymenoptera: strial row near middle ofelytron; rows of
Formicidae). Systematic placement fol- semi-erect to reclinate setae associated
lows that of O'Brien and Wibmer (1982) with elytral interspaces; scattered larger
and the generic diagnoses ofEugnamptus erect setae between rows of puncta;
Schonherr as presented by Voss (1941) scutellum small, partly concealed; scutel-
and Hamilton (1989) were used. lar striole not visible; pygidium obscured
by partially exposed inner wings.
—
Eugnamptusproterus Poinar and Brown, Material examined. Holotype female
new species in amber from Chiapas, Mexico. De-
(Figs. 1^) posited in the Poinar amber collection
— maintained at Oregon State University
Description. Length, 4.7; width, 1.3; (accession number C-7-402).
color reddish brown throughout, anten- Etymology.—The specific epithet
nal funicle paler. "proterus," a latinised adjective derived
Head: Elongated, somewhat dorso- from the Greek proteros meaning earlier,
ventrally flattened; length (0.60) greater refers to the specimen being the first
than width (1.30); frons wide, width, definite fossil —representative ofthe genus.
0.38; head-eye width, 0.96; weakly nar- Comments. Whether the pygidium is
rowed behind eyes; portion between eyes or is not exposed is a character used in
with few scattered medium-sized punc- separating members of this group (Voss
tures; most of rostrum with few barely 1941; Hamilton and Novinger 2004 ). It
detectable fine punctures; neck (length, is not possible to determine if the tip of
0.40) with small punctures arranged in the pygdium is exposed since that area is
longitudinal rows; approximately equal covered by the tips of the inner pair of
to width at base of rostrum; length wings. However, based on the curved
rostrum, 1.20; eyes large, protruding, tips of the elytra, it is likely that at least
distance between outer borders slightly some portion of the pygidium would
less than length of rostrum; rostrum have been exposed in life. The character
long, narrow, broadening at apex, longer "next to last strial rowjoins the last strial
than head but shorter than head + row near the middle of the elytron"
pronotum; rostrum with median longi- places the fossil in the subgenus Eu-
tudinal ridge extending from between gnamptobius Voss (1941) however this
antennal insertions toward apex; anten- taxon was given generic status by Lega-
nae insertions at middle of rostrum; lov (2003). In the key to the species of
scape longer than first funicular joint; this subgenus provided by Voss (1941),
club subequal to funicle in length; club the fossil runs to the Japanese E.
segments elongate, subequal in length. aurifrons Roel. Both species share several
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
882
Figs. 1-3. Eugnamptusproterus in Mexican amber. \, Lateral view. Bar = 0.85 mm. 2, Frontal view
showing rostral ridge. Bar = 0.37 mm. 3, Appendiculate claw. Bar = 0.07 mm.
VOLUME NUMBER
109, 4 883
characters, including a medial carina on
the rostrum. However, the fossil is larger
in total length (4.7 mm vs. 3.5 mm) and
has a head width (including eyes) of
almost 1.5 times the width of the pro-
thorax (this ratio is roughly equal in E.
aurifrons).
In the key to the La Selva species of
Eugnamptina (Hamilton and Novinger
2004), the fossil keys to the couplet
separating E. pusillus Hamilton and
Novinger and E. heredierisis Hamilton
and Novinger. These two species are
separated by color differences, which
cannot be used in the fossil since lighter
colors darken over time. However, both
of these extant species have shortened
elytra depressed behind the scutellum,
which is not the case with the present
fossil. Other extant species that resemble
E. proterns are E. rufifrons Sharp and E.
obscurus Sharp (Sharp 1889; Legalov
2003). However, in these species, the
length of the abdomen is longer or at
most subequal to the combined lengths
of the head (including beak) and thorax,
while in E. proterus, the combined length
of the head and thorax is 1.3 times the
length of the abdomen.
Distinguishing characters of the fossil
include the median longitudinal carina
extending from the antennal insertions
almost to the apex of the rostrum, the
elongate "neck" region, the cylindrical,
narrow pronotum, a head width of
almost 1.5 times the width of the pro-
thorax and the unusually wide claw
appendages.
Discussion
All previously described fossils as-
signed to the family Rhynchitidae are
impression fossils and many of their
Fig. 4. Dorsal view ofEugnamptusproterus in
Mexican amber. Scutellar striole not visible. Bar =
1.0 mm.
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
884
characters are difficult to discern. Two nus Heyden and Heyden (1866) have
previous fossils have been described in antennae with thickened clubs inserted at
the genus Eugnamptus, namely E. decem- the base of the rostrum and robust
satiis Scudder 1878 and E. grandaevus bodies with a straight beak, which differs
Scudder 1890, both from the Eocene from that of the present fossil.
Green River shales. However, the speci- The biology ofeugnamptines is poorly
mens (three of E. grandaevus and one of known although most appear to have
E. decemsatus) are all fragmentary and arboreal habits. Adults of the North
their assignment to the genus Eugnamp- American Eugnamptusangustatus(Herbst)
tus is questionable. In a later work listing feed and mate on sassafras trees while
the fossil weevils from the United States, the larvae mine both dead and living
Scudder (1893) acknowledged that nei- leaves ofsassafras, oak, walnut, dogwood,
ther of these two fossil species were hickory and black gum (Hamilton
placed in Eugnamptus "with any great 1980; Bright 1993). In Central America,
confidence." species of Eugnamptus have been re-
Also in his 1893 publication, Scudder covered from the tree families, Anacardia-
described an additional seven genera of ceae, Hernandiaceae, Leguminoseae,
Rhynchitidae in his newly proposed Meliaceae, Myristicaceae, Sabiaceae and
subfamily Isotheinae from the Florissant Tiliaceae (Hamilton and Novinger 2004).
beds in North America. He characterized The flora in Mexican amber has been
the subfamily as having the insertion of little studied; however, aside from
the antennae "before the middle of the Hymenaea mexicana Poinar and Brown
basal half of the straight and porrect (2002) (Fabaceae), Miranda (1963) de-
beak." The straight and porrect beak scribed Tapirira durhamii Miranda (Ana-
separates these genera from species in the cardiaceae) and an Acacia sp. (Fabaceae)
genus Eugnamptus, including the present from these deposits. It is interesting that
fossil. Other fossil rhynchitids include Tapirira guianensis Aubl. was one of the
members ofthe genus Masteutes Scudder trees from which Hamilton and Novinger
1893 as well as species of Auletes (2004) obtained Eugnamptus for their
Schonherr and Rhynchites Schneider
studies.
(Scudder 1893), all of which are mor-
phologically distinct from the present Acknowledgments
fossil. The fossil genus Eugnamptidea We thank G. Kuschel, M. Alonza, and
Wickham 1912 has a four-segmented A. Riedel for discussions regarding the
club and Rhynchites inartynovi Ter-Min- systematic position of this fossil, Alex-
asyan (1947) from Pleistocene shales in ander G. Kirejtshuk for supplying refer-
Asia is much larger and has characters ences on fossil rhynchitids, Lucas Roots
similar to those of the genus Rhynchites. for translation services, and Roberta
Zherichin (1992) described four fossil Poinar for corrections on earlier drafts.
attelabids from the Upper Oligocene of
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