MISSING LINKS BETWEEN ARGYRONETA AND CYBAEIDAE REVEALED BY FOSSIL SPIDERS

12 Pages·2002·12.9 MB·English

by  Paul A Selden

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2002. The Journal of Arachnology 30: 89-200
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MISSING LINKS BETWEEN ARGYRONETA AND CYBAEIDAE
REVEALED BY FOSSIL SPIDERS
Paul A. Selden: Department of Earth Sciences, University of Manchester, Manchester
M13 9PL, UK. E-mail: [email protected]
ABSTRACT. Argyroneta aquatica (Clerck 1757) should be included in Cybaeidae Simon 1898. There
is no justification for a monotypic family Argyronetidae; differences from other cybaeids are either spe-
cializations for aquatic life or derived with respect to other cybaeids. The features of a recently described
Eocene spider, Vectaraneus yulei Selden 2001 are discussed, which place it together with Argyroneta in
subfamily Argyronetinae Thorell 1870 of Cybaeidae. Fossil spiders intermediate between Vectaraneus and
Argyroneta are reviewed.
Keywords: Argyronetidae, Argyronetinae, Desidae, Eocene, England, Isle of Wight
The European water spider, Argyroneta land; all from upper Eocene Bembridge Marls
aquatica (Clerck 1757) is the only spider (‘Insect Bed’) of Gurnard Bay (except
known to live for most of its life in fresh water. IWCMS 1999.6 which is from Thorness Bay),
Most authors (e.g. Simon 1898; Platnick 1989, Isle of Wight, England. The following Recent
&
1993, 1997; Bennett 1991; Grothendieck material, all in the author’s collection unless
Kraus 1994) agree that this species is close to stated otherwise, was studied for comparative
Cybaeidae Simon 1898, but it has been placed purposes. Agelenidae: Agelena labyrinthica
in a monotypic family Argyronetidae by some (Clerck 1757), female, 19 July 1990, Inns-
(e.g. Roth 1967a; and references therein), thus bruck University, Austria, 11°20.5'E/
emphasizing the unique adaptations for aquatic 47°I5.6'N, rough ground; Lycosoides coarc-
life which set this species well apart from its tata (Dufour 1831), female. May 1994, SW
terrestrial relatives. In this paper I briefly re- side of Sober harbor, Mallorca, garrigue; Te-
view the morphological adaptations to aqua- genaria silvestris L. Koch 1872a, male. Black
tism in Argyroneta Latreille 1804; summarize Ball, Dunster, Somerset, England, SS 982425,
the features of a recently described Eocene spi- heathland near pines. Anyphaenidae: Amau-
der, Vectaraneus yulei Selden 2001, which robioides maritimus O. P.-Cambridge 1883,
place it in the cybaeid subfamily Argyroneti- female, Dunedin, New Zealand (coll, Califor-
nae, also recently emended by Selden (2001); nia Academy of Sciences); Anyphaena accen-
and refer to other fossil spiders which are in- tuata (Walckenaer 1802), female, 10 April
termediate between Vectaraneus Selden 2001 1996, Carnac, France (coll, D. Penney); Hi-
and Argyroneta. bana similaris (Banks 1929), female, 3 De-
cember 1995, El Valle, Panama (coll. D. Pen-
METHODS
ney); Cybaeidae: Argyroneta aquatica Clerck
Material studied. Elvina antiqua (von 1757, female, 18 June 1981, Whixall Moss,
BMNH
Heyden 1859), holotype 58825, Nat- Shropshire, England, SJ 49-36-; male, com-
ural History Museum, London, from Miocene mercial slide, compressed mount (dated
&
Brown Coal of Grube Stoschen, near Linz am 1895); Cybaeus hesper Chamberlin Ivie
Rhein, Germany. Vectaraneus yulei Selden 1932, male, 30 October 1998, Redwood
2001, holotype BMBN 021960/1, Booth Mu- grove, Monte Rio, Sonoma County, Califor-
seum of Natural History, Brighton, England; nia, 38°28.811'N/123°00,275'W; Cybaeus pa-
paratypes: IWCMS 1999.6, Isle of Wight Mu- tritus Bishop & Crosby 1926, female, 15 July
seum of Geology, Sandown, Isle of Wight, 1996, Highlands Biological Station, Macon
BMNH BMNH
England; In 1715 1, I 8438, County, North Carolina. Dictynidae: Devade
BMNH
I 8440 and I 8452 (part and counter- Simon 1884 sp. female, 24 May 2000, bridge
part), Natural History Museum, London, Eng- on Ghara-Aghatch river, Ears Province, Iran,
189
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THE JOURNAL OF ARACHNOLOGY
190
52°13'E/29°4UN; Dictyna arundinacea Lin- arrangement was followed by some other east
naeus 1758; female, 23 May 1999, Manning- Asian arachnologists, e.g. Komatsu (1961),
TM
tree, Essex, England, 081326, Phragmites Yaginuma (1955, 1958, 1960, 1962) and Paik
marsh; D. calcarata Banks 1904, females, 30 & Namkung (1967). In his catalog. Bonnet
June 1996, Wheeler Creek Nature Trail, Ven- (1955-9) included only the type genus, Ar-
tura County, California, riparian woodland; D. gyroneta, in the family, whereas Roewer
innocens O. R-Cambridge 1872, female, 10 (1942-54) added Gohia Dalmas 1917 and Ur-
April 1995, Odeion, Paphos, Cyprus, 32°24'E/ quhartia Bryant 1933. Roth (1967a) both rec-
&
34047'N; D. reticulata Gertsch Ivie 1936, ognized and reviewed Argyronetidae, and the
females, 30 June 1996, Rose Valley Lake, family status was used in the catalogs of Brig-
Ventura County California, on Artemisia', fe- noli (1983) and Platnick (1989, 1993). How-
W
males, 25 August 1993, 5 mi. of Middle- ever, Berland (1932), De Blauwe (1973),
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gate, Nevada, 1 18°10'W/39°15'N, on Artemi- Gertsch (1949), Locket Millidge (1953),
sia; D. uncinata Thorell 1856, female, 22 May Locket et al. (1974), Millot (1949) and Saito
1999, Newbourne, Ipswich, Suffolk, England, (1941) either ignored the family status or
TM
271435; Lathys humilis (Blackwall 1855), placed Argyroneta in Agelenidae, usually Cy-
female, 22 May 1999, Newbourne, Ipswich, baeinae (e.g. Grothendieck and Kraus 1994).
TM
Suffolk, England, 271435; Mallos palli- Cybaeinae is commonly raised to family sta-
dus Banks 1904, female, 30 June 1996, Rose tus in more recent works (e.g. Bennett 1991;
Valley Lake, Ventura County California, on Platnick 1993, 1997). Lehtinen (1967) limited
Artemisia', Tricholathys cf. spiralis Chamber- Argyronetinae to the type genus but placed it
&
lin Ivie 1935, females, 30 June 1996, Rose and Cybaeinae in Dictynidae in his superfam-
Valley Lake, Ventura County California, un- ily Amaurobioidea. Eorster (1970) put Argy-
der stones in dry wash. ronetidae (also limited to Argyroneta) and Cy-
Material was studied using a Wild stereo- baeidae (elevated by him to family status) in
microscope; drawings were made with a cam- Dictynoidea, but disagreed with most other
era lucida attachment; photographs were tak- authors on the close relationship between Ar-
en using a Minolta Dynax 9 camera attached gyroneta and Cybaeidae, preferring a closer
to the microscope. All measurements are in alliance of Argyroneta, Amaurobioides and
mm. Abbreviations: 1, 2, 3, 4 = walking legs Anyphaenidae. Platnick’s (1997, 2001) latest
1-4; AS = anterior spinneret; ch = chelicera; catalogs put Argyroneta in Cybaeidae. Plat-
cx = coxa; lab = labium; MS = median spin- nick (2001) pointed out that Argyronetidae
neret; p = posterior; Pd = pedipalp; PS = Thorell 1870 actually has priority over Cy-
posterior spinneret; st = sternum; tr = tro- baeidae Banks 1892, but that the latter name
chanter; tub = tubercle. is now in widespread use.
Numerous works have dealt with the aquat-
Argyroneta aquatica (Clerck 1757)
ic mode of life and associated morphological
Remarks. Argyroneta aquatica was first and physiological adaptations of A. aquatica,
formally described and named by Clerck especially Braun (1931, and references there-
(1757:143-150; pi. 6, tab. 8, figs. 1, 2), in his in) and Crome (1953); and most works on spi-
genus Araneus, and the monotypic genus Ar- der respiratory physiology have studied the
gyroneta was erected for this species by La- tracheal system of Argyroneta, e.g. Bertkau
treille (1804). Thorell (1870) created the sub- (1872), Bromhall (1987a), Lamy (1902) and
family Argyronetinae, which Menge (1871) Purcell (1910). There are a number of adap-
A
elevated to family level in the following year. tations in Argyroneta for an aquatic life.
Simon (1898) recognized Argyroneteae as a dense mat of fine setae covering the opistho-
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tribe in Cybaeinae (Agelenidae), alongside soma (Figs. 1, 2) acts as a plastron an aquat-
Cybaeae and Desiae, and included the genera ic lung which allows air breathing under wa-
Amphinecta Simon 1898 and Cambridgea L. ter, which works in the following way. The
Koch 1872b in Argyroneteae. Eamily status specialized setae (Braun 1931; Grothendieck
&
for Argyronetidae was accepted by Dahl Kraus 1994: figs. 10-13) trap a bubble of
(1937), Kaston (1948), Petrunkevitch (1939) air against the body surface and in connection
and Reimoser (1919). Kishida (1930) placed with the tracheal spiracles. Oxygen diffuses
Desis and Cybaeinae in the family, and this from the surrounding water into the air bub-
SELDEN—FOSSIL ARGYRONETINAE 191
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Figures 1-2. Argyroneta aquatica (Clerck 1757), adult male, microscope preparation. 1, whole body
showing large chelicerae, heart-shaped sternum, long setae on base of posterior walking legs and sternum.
2, Opisthosoma showing dense felt of fine setae forming plastron, and long setae on base of posterior
walking legs and sternum.
ble, which can then be exchanged in the spi- heart rates have larger tracheal systems, and
der’s tracheal system in the normal way. are either active or aquatic spiders. Presum-
Eventually, the concentrations of O and CO ably, gas exchange is faster when oxygen is
2 2
in the bubble decrease/increase respectively, delivered directly to tissues by the tracheal
so that the bubble needs to be replenished system than by intermediate transport in he-
with fresh air. Long setae on the proximal po- molymph. The fewer heart ostia ofArgyroneta
domeres of the walking legs (mainly 3 and 4) (Roth 1967a) might also be correlated with the
and the sternum (Figs. 1, 2) may aid in re- diminished need for blood circulation. All of
plenishing the air bubble and in carrying air these features can be considered as adapta-
to the bubble-nest. The tracheal spiracle in Ar- tions for an aquatic mode of life.
&
gyroneta is rather wide and situated just pos- Grothendieck Kraus (1994) discussed
terior to the epigastric furrow. It leads to two aquatic adaptations and relationships of Ar-
large tracheae (Lamy 1902: fig. 56) which run gyroneta, and concluded that the adaptations
forward into the prosoma before splitting into of aquatic life were insufficient argument to
many finer tubes that extend into all parts of separate the genus from other members of Cy-
the prosoma, including the tarsi; similar tu- baeinae (to which it is otherwise closely re-
bules permeate the opisthosoma (Bromhall lated, e.g. similarities in male copulatory or-
1987a: figs, 2, 9-10), giving this spider the gans), and Argyroneta is merely an aquatic
highest density of tracheae of any studied so specialized cybaeine(-id). These authors stated
&
far. In a study of the relationship between spi- (Grothendieck Kraus 1994: 272): ‘Deshalb
der heart rates and locomotion (Bromhall favorisieren wir die urspriingliche Ansicht SI-
MONS
1987b), Argyroneta had the lowest heart rate (1898: 224, 230), wonach es sich bei
of those studied. In general, spiders with low Argyroneta um ein spezialisiertes Subtaxon
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THE JOURNAL OF ARACHNOLOGY
192
der Cybaeinae handelt. Es besteht keine Ver= part of the opisthosoma of the holotype (pre-
anlassung, ftir die Wasserspinne eine separate sumably replacing silk glands or ova) was re-
Subfamilie Argyronetinae oder gar eine Fam= moved to reveal the spinnerets (Figs. 3, 4).
ilie Argyronetidae beizubehalten. Spezielle Because of the preservation of internal anat-
Lebensweise und Anpassungen (insbesondere omy, and their three-dimensional nature, the
Lage des Tracheenstigmas, relativ dichte Kor^ fossils must represent dead animals rather
per-Behaarung, Zahl und Anordnung der than molts. Detailed description of the species
Bothriotrichen der Laufbein-Tarsen) stellen is given in Selden (2001) and a summary pre-
kein Argument zur Begriindung einer solchen sented in Table 1, herein.
Rangstufe dar/ [Therefore we favor the orig-
DISCUSSION
SIMON
inal opinion of (1898: 224, 230), ac-
cording to whom Argyroneta occupies a spe- Argyroneta and cybaeid monophyly.
cialized subtaxon of the Cybaeinae. There is Lehtinen (1967) was the first author to suggest
no reason to maintain a separate subfamily the separation of Cybaeidae from Agelenidae.
Argyronetinae or a family Argyronetidae for Following the realization that the presence of
the water spider. The specialized way of life cribellum and calamistrum was plesiomorphic
and adaptations (in particular the position of within Araneomorphae, he was able to place
the tracheal stigmata, relatively thick body se- the ecribellate Cybaeinae and Argyronetinae
tation, number and arrangement of the tricho- in the cribellate Dictynidae, based on similar-
bothria of the walking-leg tarsi) do not con- ity of genital organs, and separate from Age-
stitute an argument in favor of such a status.] lenidae. Lehtinen defined Agelenidae on a
combination of three characters: paired colu-
Vectaraneus yulei Selden 2001
lus, three tarsal claws, and lengthened poste-
Vectamneus yulei Selden 2001: 725-726, plates 1- &
rior spinnerets. Forster (1970) and Forster
5, text-figs. 1-9. Wilton (1973) carried the separation of Age-
Remarks. This taxon was erected for lenidae from Cybaeidae further or by placing
some fossil spiders from the so-called Insect Cybaeidae and Argyronetidae in Dictynoidea
Bed of the upper Eocene (c. 35 Ma) Bem- but Agelenidae in Amaurobioidea, primarily
bridge Marls Member of the Bouldnor For- on tracheal system characters. Bennett (1991)
mation (Solent Group) of Thorness Bay, Isle reviewed the status of Cybaeidae to that date.
of Wight, England. The most remarkable as- He suggested that secondary pores on the vul-
pect of the Bembridge spiders is the very fine va might be a useful taxonomic character, but
preservation of internal anatomical structure found that they were rather widespread in Dic-
by replacement with calcite (CaC03 Some tynoidea (sensu Forster 1970), and present
).
organic matter is preserved, mainly cuticle both in cybaeids and Argyroneta. He dis-
lining the external mould cavities of the che- cussed the status of cybaeids in relation to
licerae and setae within the rock which can be Agelenidae, concluding that cybaeids shared
seen when the specimens are observed under many of the characters of agelenids: ecribel-
alcohol, but within the moulds of the chelic- late, three tarsal claws, single row of tarsal
erae, labium and coxae, fine fibers of cream- trichobothria, unnotched trochanters, and
colored calcite can be seen replacing muscle spinnerets not in a transverse row, but that
fibers, as described for the Bembridge Marls these characters were either convergent or ple-
insects by McCobb et al. (1998). In the op- siomorphic at the family level. Characters sep-
isthosomae, book-lung lamellae are preserved arating cybaeids from agelenids: closely
in buff-colored calcite, and the book-lung atria spaced anterior spinnerets, and narrowed pos-
anterior to the lamellae are lined with tiny, terior spinnerets with a very short distal seg-
buff, drusy calcite crystals. The opisthosomae ment, are widespread in other spiders. As
are filled with cream-colored calcite, which pointed out by Griswold (1990:13) ‘'The Age-
strikingly preserves the large tracheae running lenidae has performed for three-clawed ecri-
forward from a wide spiracle near the middle bellate spiders much the same function as
of the opisthosoma. The inner surfaces of Amaurobiidae has for cribellates: a dumping
these tubes bear spiral or scalariform rein- ground for obscure and undistinguished
forcements preserved in the same cream cal- forms. Not surprisingly, identification of a
cite. Spheroidal calcite filling the posterior synapomorphy for the Agelenidae is difficult.
SELDEN—FOSSIL ARGYRONETINAE 193
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BMBN
Figures 3-4. Vectaraneus yulei Selden 2001, holotype part, female, 021960, upper Eocene,
Bembridge Marls, Isle of Wight, England. 3, Camera lucida drawing, explanation for Fig. 4; 4, Specimen
after excavation of fibrous calcite replacing fine tracheae (dashed line shows rear edge of sternum); spin-
nerets after removal of calcite spheroids.
but I think that Lehtinen (1967:401) has pro- the outgroup of the cybaeids probably is, or
posed just such a character. He stated that all lies within, Dictynidae.
true agelenids (including the genus Agelena) Regardless of where cybaeids are placed,
have a paired colulus consisting of two, more and their taxonomic rank, Argyroneta is rec-
or less protruding, obtusely triangular plates. ognized by nearly all authorities (e.g. De
&
I have examined many genera of Agelenidae Blauwe 1973; Bennett 1991; Coddington
&
and found this character to be a conspicuous Levi 1991; Grothendieck Kraus 1994) to be
and consistent synapomorphy.” Cybaeids and a derived cybaeid. The position of Cybaeidae
&
Argyroneta (e.g. Roth 1967a; Grothendieck is relevant to the position of Argyroneta be-
Kraus 1994) lack a colulus, but do show cause Argyronetidae is only sustainable if Cy-
paired setal patches. Roth (1967b) suggested baeidae is monophyletic without Argyroneta.
using this character in conjunction with the Bennett (1991) was unable to find an auta-
length of the distal segment of the posterior pomorphy for all species referred to Cybaei-
spinneret in the separation of agelenines and dae, though the presence of one or more peg
cybaeines. Bennett (1991) concluded that Cy- setae on the patellar apophysis of the male
baeidae was monophyletic on the basis of palp serves as a character which distinguishes
shared possession of a suite of characters not most species. The clade defined by this char-
found in the same combination elsewhere, and acter excludes Cybaeota, for example, which
used male palp characters to demonstrate that lacks a patellar apophysis but was included in
THE JOURNAL OF ARACHNOLOGY
194
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Table 1, Comparison of features of Vectaraneus Selden 2001 with Anyphaenidae, Cybaeidae [Argy-
roneta in brackets], and Desidae [Desis in brackets]. Italics denote characters in common with Vectaraneus.
Cybaeidae Desidae
Feature Vectaraneus Anyphaenidae [Argyroneta] [Desis]
Chelicera: shape vertical vertical vertical commonly porrect
promarginal teeth 3(1+1 bifid) 3-6 3 toothed
retromarginal teeth 2 + carina/denti- 5-9 minute denticles [2 teeth] toothed
cles
furrow broad, ribbed narrow narrow broad
condyle distinct distinct distinct distinct
setal fringe 7 present present [absent] absent
Labium: shape longer than wide as long as wide as long as wide longer than wide
apex unnotched, round- usually notched blunt rounded to blunt
ed
basal notches present present slight present
Pedipalp coxa: shape rectangular rectangular rectangular elongate
scopula present present present present [absent]
seiTula present present present absent
Legs: leg formula 4123 1423 4123 1423
ta claw tufts absent? lamellate absent absent
scopula absent dense absent weak
tr limulus unnotched notched unnotched to notched [unnotch-
slightly notched ed]
spines present (fe, pa, ti, present present present [few on
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mt) legs 1 2]
ta spines absent? absent absent present
Carapace: shape longer than wide longer than wide longer than wide longer than wide
fovea 9 longitudinal longitudinal distinct
[weak]
Sternum: shape heart-shaped oval, apex pointed heart-shaped scutiform
precoxa triangles absent present absent absent
Opisthosoma: shape globular-ovoid ovoid globular ovoid
setation only normal setae plumose + nor- normal [+ fine] fine setae only
mal setae
Tracheae: extent into prosoma into prosoma into prosoma opisthosoma only
spiracle position median median posterior [anteri- slightly anterior to
or] spinnerets
spiracle width broad broad narrow [wide, broad
separate]
median trunks large, thickened large normal [large] normal
lateral trunks absent? present absent present
Spinnerets: position subterminal terminal subterminal terminal
AS close together contiguous close together contiguous
MS very small large very small same size as AS
PS smaller than AS cylindrical smaller than equal to or longer
[equal to] AS than AS
colulus/cribellum absent group of setae absent prominent colulus/
cribellum
Anal tubercle distinct distinct distinct distinct
Total similarities with 33 15 27 [25] 13 [12]
Vectaraneus
Cybaeidae by Bennett (1988, 1991) because it ed to only those species which share the syn-
could not be placed elsewhere. Argyroneta has apomorphy of peg setae on a patellar apoph-
a small patellar apophysis but lacks peg setae. ysis, which would leave at least Cybaeota,
To summarize: Cybaeidae could be restrict- Cybaeozygci and Argyroneta Vls incertae sedis
SELDEN—FOSSIL ARGYRONETINAE 195
within Dictyeoidea, as Bennett (1991) con- half-way between the epigastric furrow and
cluded. The presently constituted Cybaeidae the base of the spinnerets, with large tracheae
(e.g. Platnick 1997) encompasses these addi- running forwards into the prosoma, are the
tional genera; thus the family lacks an auta- most characteristic. Forster (1970) placed
pomorphy but nevertheless can be defined on Amaurobioididae, Anyphaenidae, Argyrone-
a suite of shared characters not found in the tidae, Cybaeidae, Desidae, Dictynidae, and
same combination elsewhere. Regarding Ar- Hahniidae in the superfamily Dictynoidea,
gyroneta, it has been pointed out by Groth- united by their large, branched, median tra-
endieck & Kraus (1994) that the differences cheal trunks. He pointed out that in dictynoids
between the genus and other cybaeids are al- in which tracheal systems extend into the pro-
most entirely due to a secondary aquatic life. soma, spiracles occur in a more anterior po-
Thus, these character states are derived with sition than usual; this occurs in Anyphaenidae
respect to cybaeids, and to exclude Argyro- (which includes Amaurobioididae; see Plat-
neta from the Cybaeidae would render the nick 1974; Ramirez 1995), Argyronetidae,
family paraphyletic. some Desidae, and Hahniidae. Vectaraneus is
Looking at the differences between Argy- in this group of families, excluding Hahniidae
roneta and Cybaeus in more detail [state in because of their transverse spinnerets. Table 1
Argyroneta in brackets]. 1) setal fringe on the compares morphological features of Vectara-
chelicera: present [absent]; since the setal neus, Anyphaenidae, Cybaeidae (including
fringe is absent in other aquatic spiders (e.g. Argyroneta), and Desidae (including Desis). It
Desis)^ it could be a hindrance in feeding and can be seen that Vectaraneus shares more
thus a derived characteristic due to aquatic character states with Cybaeidae (27/33) than
life; moreover, its presence in potential out- with any other (see Selden 2001 for detailed
groups (Ageleeidae, Dictynidae) determines discussion). It is possible that Vectaraneus
that its absence is derived. 2) a suite of char- represents another parallel development of
acters related to the tracheal system (see Table aquatic life in a different group of spiders, but
1), e.g. large tracheal trunks, extensive tra- this hypothesis requires the unsubstantiated
cheation, broad spiracle, etc., are clearly re- assumption of more convergence, and nearly
lated to an aquatic mode of life, and therefore all other characters are consistent with Vec-
derived. 3) extensive, fine setation of the ab- taraneus being a cybaeid. As discussed above,
domen (plastron) and long setae on proximal the monophyly of Cybaeidae is not based on
podomeres of posterior legs in Argyroneta are synapomorphies but on a unique combination
clearly derived features related to air uptake of characters; Vectaraneus shares these char-
from the water surface. 4) heart ostia three acters, where they are preserved.
&
pairs [two pairs] (Roth 1967a, Table 1); this As discussed above, Grothendieck Kraus
reduction of heart ostia could be related to the (1994) considered Argyroneta to be a cybaeid
reduced need for blood circulation because of which shows adaptations for aquatic life, in-
the better tracheal penetration (cf. lower heart cluding a wide, forwardly positioned, tracheal
rate recorded for Argyroneta by Bromhall spiracle, large tracheal trunks running into
1987b). 5) tarsal trichobothria in a single row prosoma and extensive tracheal system. Vec-
[double row]; because a single row of tarsal taraneus shows these features also, but differs
trichobothria occurs in putative sister groups in that the spiracle is situated half-way be-
to Cybaeidae (Ageleeidae and Dictynidae), a tween the epigastric furrow and the spinnerets.
double row must be considered derived. However, the spiracle occurs in this position
To conclude this discussion, Cybaeidae in juvcnilQ Argyroneta (Crome 1953: figs 51-
would be paraphyletic without Argyroneta; 54). Vectaraneus also lacks the plastron.
recognition of Argyronetidae with the same Therefore, Vectaraneus most closely resem-
rank as Cybaeidae is unsustainable, but sub- bles juvenile Argyroneta. If Argyroneta is a
family Argyroeetinae could be justified. The cybaeid which has become adapted to an
large number of derived characters separating aquatic existence, then Vectaraneus may be
Argyroneta from other cybaeids predicts the considered to occupy a part-way stage in this
existence of intermediate taxa. trend. Juvenile Argyroneta show a stage in the
—
Vectaranem, Of all the features of Vec- development of aquatic adaptations seen in
taraneus, the wide tracheal spiracle, situated the adult stage of Vectaraneus.
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THE JOURNAL OF ARACHNOLOGY
196
Other fossils referred to Argyroneta,
Von Heyden (1859) described a fossil spider
from the Miocene Brown Coal of Grube
Stoschen, near Linz am Rheine, Germany, as
Argyroneta antiqua von Heyden 1859, placing
it in that genus on account of its general ap-
pearance and its preservation in a swampy pa-
laeoenvironment, rather than on the basis of
any characteristic morphological features,
which are lacking in the fossil. Heer (1865,
1872, 1876) described a collection of spiders
from the Miocene of Oeningen (Ohningen),
A
on the border of Switzerland and Germany.
particularly long-legged form he referred to
Argyroneta, and named Argyronectal [sic.]
longipes Heer 1865. In regard to this speci-
men, Heywood (footnote in Heer 1876: 11) —
BMNH
commented: “Unfortunately the two speci- Figure 5. Argyroneta sp. In 39930,
mens which Prof. Heer received are not suf- Miocene Brown Coal of Rott, Germany; see Bert-
kau (1878).
ficiently well preserved for certain determi-
nation. The comparative lengths of the legs,
the thin filiform palpi, and the rounded form fer (‘flint-slate’) and nine from the Blatterkoh-
of the sides of the cephalothorax are in favour le (‘leaf-coal’). These are now distributed in
of it being refen'ed to Argyronecta [sic.]; but a number of museums, including The Natural
the cephalothorax is less prominent in front History Museum, London (BMNH 59627 and
than in the existing species. A similar form of BMNH In 39930 (Fig. 5)), American Museum
(AMNH
cephalothorax and legs also occurs in Tegen- of Natural History 26275) and the
aria. According to Thorell [1870, see below] George Statz Collection in the Los Angeles
this species does not belong in Argyronecta County Museum of Natural History (including
LACM
[sic.], but seems to form a distinct genus”. 3086, figured by Furst 1959, 1970).
Thorell (1870) created the new genus Elvina, Bertkau gave a detailed description of the spe-
diagnosed by the palps being thicker than the cies, including the heart-shaped sternum, and
legs, not for Heer’s specimen, but for the one discussed the nature of prominent parallel
described by von Heyden (1859). Thorell bands (‘Langstreiffen’) on the opisthosomae
(1870: 224) suggested that Argyroneta anti- of the Kieselschiefer specimens, concluding
qua von Heyden 1859 probably belonged in that these represented a prominent tracheal
Tubitelariae (a name no longer in use for spi- system. He suggested that the new specimens
ders which do not fall easily into any other were conspecific with the holotype of A. an-
category, including Agelenidae, Gnaphosidae, tiqua, and that the species belonged in Argy-
Clubionidae, Urocteidae, Filistatidae and Dys- roneta but differed from A. aquatica princi-
deridae), and possibly (ThorelTs emphasis) in pally in that the tracheal spiracle was more
Agelenidae: Argyronetinae. Re-study of the posterior in position than in the type species.
holotype of Argyroneta antiqua von Heyden Bertkau was familiar with Argyroneta, and
1859 by Selden (2001) concluded it is Ara- with spider tracheal systems in general, hav-
neomorphae incertae sedis, but not an Argy- ing published on spider respiratory organs a
roneta, and it was referred to Elvina Thorell few years earlier (Bertkau 1872). Thus, Bert-
1870. As for A. longipes Heer 1865, Thorell kau (1878: 359) clearly understood the im-
(1870) was certain that it did not belong in portance of his conclusion that the fossils
Argyroneta, and I concur. were an example of an evolutionary missing-
Bertkau (1878) described a collection of link: “Fine Gewissheit in dieser Frage ware
fossil spiders and a millipede from the Brown allerdings von hohen Interesse, da mir der ge-
Coal of Rott, including 19 specimens he re- genwartige Fall fiir die Descendenztheorie be-
ferred to Argyroneta antiqua', ten (including sonders lehrreich zu sein scheint.” [Certainty
von Heyden’s holotype) from the Kieselschie- of this question would, however, be of great
SELDEN—FOSSIL ARGYRONETINAE 197
Argyronetinae
other Vectaraneus Bertkau’s Argyroneta
cybaeids yulei specimens aquatica
—
Figure 6. Cladogram showing hypothesized relationship between Vectaraneus yulei, Argyroneta aqua-
tica, Bertkau’s specimens, and other Cybaeidae. Characters at node 1 defining Argyronetinae: enlarged
tracheal trunks running into prosoma, and wide tracheal spiracle situated well forward of base of spin-
nerets; at node 2 (Bertkau’s specimens + A. aquatica): dense opisthosomal pilosity (plastron), and long
setae on legs 3 and 4; and at node 3 (A. aquatica): tracheal spiracle close to epigastric furrow in adult.
interest, since it seems to me to be a particu- summarizes the phylogenetic hypothesis. Sel-
larly instructive case of the Theory of Evo- den (2001) emended Argyronetinae as fol-
lution.] lows: “Cybaeidae with enlarged tracheal
AMNH
In his study of 26275, Petrunkev- trunks running into prosoma; wide tracheal
itch (1946) showed that this specimen was not spiracle situated well forward of base of spin-
conspecific with the holotype of Argyroneta nerets.”; included genera and Vec-
BMNH
antiqua, and neither are the specimens taraneus.
—
59627 and In 39930 (Selden 2001). Bertkau’s Mode of life. The rock matrix preserving
specimens are, however, close to the extant A. Vectaraneus is a massive, fine limestone
aquatica, differing, as Bertkau (1878) men- which resembles the lithology of the main,
tioned, by the more posterior position of the tabular, insect-bearing horizon occurring near
tracheal spiracle. In this, they resemble Vec- the base of the Bembridge Marls (Jarzem-
taraneus. However, Vectaraneus lacks the bowski 1980; McCobb et al. 1998). Biota as-
plastron of fine hairs on the abdomen and pos- sociated with the spiders include the reed Ty-
sibly also the long hairs on the posterior two pha, the crustacean Branchipodites vectensis,
legs (the relevant podomeres are poorly pre- Hymenoptera, Diptera, and juvenile Araneae.
served in Vectaraneus), both of which occur The arthropods are commonly in distinct ho-
in the Bertkau specimens. Thus, the Bertkau rizons which suggests mass mortality, e.g. fol-
specimens, which all appear to be conspecific, lowing a synchronous emergence, or aggre-
sit between Vectaraneus and modern Argy- gations accumulated by water surface tension
roneta. It is likely that they could be included or adhesion to floating vegetation. The pa-
in the modern genus because they share the laeoenvironment of deposition suggested by
same characters except for the more posterior the sedimentology is a shallow, freshwater, al-
position of the tracheal spiracle. No taxonom- kaline lake (McCobb et al. 1998). Associated
ic changes are suggested here while Ph.D. re- plants, insects, and mammals suggest an open
search is being conducted on these specimens marsh habitat with wooded islands in a sub-
in Manchester by Richard Cutts. Figure 6 tropical climate (Jarzembowski 1980; Collin-
THE JOURNAL OF ARACHNOLOGY
198
son 1983, 1990; Collinson et al. 1993), per- sischen Rheinlande und Westfalens, Bonn 35:
haps similar to the Florida Everglades today. 346-360.
&
This evidence points to Vectaraneus yulei as Bishop, S.C. C.R. Crosby. 1926. Notes on the
living in a marshy habitat, and its morpholog- spiders of the southeastern United States with de-
scriptions of new species. Journal of the Elisha
ical adaptations suggest it was possibly am-
Mitchel Scientific Society 41:165-212.
phibious in its mode of life. Blackwall, J. 1855. Descriptions of two newly dis-
ACKNOWLEDGMENTS covered species of Araneida. Annals and Maga-
zine of Natural History (2) 16:120-122.
I thank Ed Jarzembowski (Maidstone Mu- Bonnet, P. 1955-1959. Bibliographia Araneorum.
seum, Kent) for kindly passing BMBN Vol. 2. Douladore, Toulouse.
021960/1 on for study; John Dalingwater Braun, F. 1931. Beitrage zur Biologie und Atmung-
sphysiologie der Argyroneta aquatica Cl. Zool-
(Hale, Cheshire) for help with scanning elec-
ogisches Jahrbuch Abteiung fiir Systematik 62:
tron microscopy; Martin Ramirez (Universi-
175-261.
dad de Buenos Aires) for helpful discussion Brignoli, PM. 1983. A Catalogue of the Araneae
on spider tracheal systems; Derek Siveter Described Between 1940 and 1981. Manchester
(University Museum, Oxford) for comments University Press, Manchester.
on taxonomy; Yuri Marusik (University of Bromhall, C. 1987a. Spider tracheal systems. Tissue
Magadan, Russia), David Penney (Manchester and Cell 19:793-807.
University) and Charles Griswold (California Bromhall, C. 1987b. Spider heart rates and loco-
Academy of Sciences) for provision of com- motion. Journal of Comparative Physiology B
157:451-460.
parative material; Lindsey Groves (Los An-
Bryant, E.B. 1933. Notes on types of Urquhart’s
geles County Museum of Natural History) for
spiders. Records of the Canterbury Museum 4:
drawing my attention to the George Statz Col-
1-27.
lection; Andrew Ross (The Natural History Chamberlin, R.V. & W. Ivie. 1932. North American
Museum, London), Stephen Hutt (Museum of spiders of the genera Cybaeus and Cybaeina.
Geology, Isle of Wight, England), and John Bulletin of the University of Utah 23(2): 1-43.
Cooper (Booth Museum of Natural History, Chamberlin, R.V. & W. Ivie. 1935. Miscellaneous
Brighton, England) for help with literature and new American spiders. Bulletin of the University
the loan of fossil specimens in their care; and of Utah 26(4): 1-79.
Margaret Collinson (University of London) Clerck, C. 1757. Araneae Suecici, Descriptionibus
et Figuris Oeneis lllustrati, ad Genera Subalterna
for discussion on the palaeoecology of the
LX
Redact! Speciebus Ultra Determinati. L. Sal-
Bembridge Marls. I thank two anonymous re-
vii, Stockholm. (In Swedish and Latin).
viewers for useful comments. &
Coddington, J.A. H.W. Levi. 1991. Systematics
and evolution of spiders. Annual Reviews of
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