20th International Congress of Arachnology

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78 DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Cushing
Student - oral presentation
Fossil spiders and ancient salt lakes
*Matthew R. Downen, Paul A Selden
Department of Geology, The University of Kansas,
1475 Jayhawk Blvd Lindley Hall Room 120, Law-
rence, KS 66045
Fossil spiders are relatively abundant in lacustrine depos-
its. This talk examines the diversity of spiders from several
lacustrine deposits, and the information they provide
about paleoenvironments. Fossil spiders from the Green
River Formation of Colorado (Eocene) include specimens
from the families Uloboridae, Hersiliidae, Selenopidae,
and Thomisidae that have recently been described. The
Florissant Formation (Eocene) has a similarly diverse
fauna with several families represented including Lycosi-
dae, Tetragnathidae, Thomisidae, and Gnaphosidae. Few
fossils from the Crato Formation (Cretaceous) have been
formally described but include mygalomorphs, araneids,
nephilids, and an exquisite palpimanid. The diversity from
these three deposits represents various life modes and
habitats. Recently, it has been demonstrated that the leg
flexure of spiders may serve as a proxy for the paleosalin-
ity of ancient lakes. The typical pose of fossil spiders from
the Crato Formation, for example, is legs tightly curled
under the body, and is suggestive of hypersalinity. Fossil
spiders from each of the three deposits were examined and
compared to modern spiders drowned in varying salinities.
Keywords: Araneae, taphonomy, paleontology, paleoen-
vironments, lacustrine
Oral presentation
Comparing araneoid biodiversity between
high and low elevation Panamanian rain-
forest sites
Michael L. Draney1, Petra Sierwald2
1Department of Natural & Applied Sciences, Univer-
sity of Wisconsin-Green Bay, Green Bay, Wisconsin,
USA; 2Division of Insects, Field Museum of Natural
History, Chicago, Illinois, USA
We used a Rapid Assessment Protocol to acquire compa-
rable samples of ground-accessible spider assemblages
from eight Panamanian rainforest sites during Sep-
tember and October, 2008. Our objectives are to obtain
species-level data on clade Araneoidea in Neotropical
rainforests; provide descriptions of the assemblages from
four low elevation (70–135 m) and four high elevation
(1181–2326 m) sites; and to determine what differences
among sites are detectable using this Rapid Assessment
data. 72 person-hours of sampling time yielded 309
adult araneoids (4.3/hour) belonging to 111 morpho-
species (56% determined to known species) in 9 families.
75% of species were found at only one of the eight sites,
and only six species were found in both low and high
elevation sites. No species were found from more than
half (four) of the sites. Theridiidae comprised nearly
half of the adult Araneoids and 38.7% of the species. It
was the numerically dominant family except at the two
highest sites, which were dominated by Tetragnathidae.
Tetragnathidae species richness was greater at higher
elevation sites, whereas Theridiidae and Mysmenidae
richness was greater at low elevation sites. Inter-site
species similarity (Bray-Curtis) was largely a function
of distance, but family-level similarity was uncorrelated
with distance and is likely ecologically meaningful. Our
data was useful for describing the assemblages, but most
site pairs were not statistically distinguishable in rich-
ness or Simpson’s diversity. Richness estimators yielded
highly variable estimates, suggesting that more data is
necessary for robust richness estimation.
Keywords: rapid assessment protocol, Neotropics, rain-
forest, elevation, Araneoidea, biodiversity, faunistics
Oral presentation
The beautiful behavior and morphology of
how spiders find and grasp silk lines
William G. Eberhard
Smithsonian Tropical Research Institute Biologia, U.
C. R. Ciudad Universitaria, Costa Rica
The morphology and behavior of the tarsi and claws are
crucial in allowing spiders to find, grasp securely, and