A new species of fossil ray spider, Baalzebub? mesozoicum n. sp. (Araneae: Theridiosomatidae), is described from Mesozoic amber from the Cretaceous (Middle Cenomanian to Early Santonian) deposits of La Garnache, Vendée, NW France. The palpal structures, especially the highly sclerotized claw-shaped retrolateral ‘paracymbium’ originating as an outgrowth of the cymbium basally and the basal cymbial lamella, are considered sufficient to make a tentative placement of the new fossil species in the extant genus Baalzebub Coddington, 1986.
The fossil record of spiders is diverse (Penney, Dunlop, & Marusik, 2012; Dunlop, Penney, & Jekel, 2013), particularly in Tertiary ambers. Within the last few decades, however, an increasing number of species have been described from the Mesozoic (Selden & Penney, 2010; Penney & Selden, 2011; Wunderlich, 2008, 2012; Penney, 2013). France has a diverse fossil spider fauna in both amber and rock (briefly summarized by Penney, 2004), including the oldest known fossil spider species (Selden, 1996). Amber spiders have been formally described and named from Tertiary deposits of Oise (Micropholcommatidae: Penney & others, 2007; Pholcidae: Penney, 2007a; Oonopidae: Penney, 2007b; see Nel & Brasero (2010) for a summary of this deposit) and Cretaceous Charentes amber (Mecysmaucheniidae: Saupe & Selden, 2009; see Perrichot, Néraudeau, & Tafforeau (2010) for a summary of this deposit).
Ray spiders (family Theridiosomatidae) are minute orb-web weaving spiders with a worldwide distribution today. They are usually found in shady, humid places and are represented by 106 extant species in 18 genera (Platnick, 2013). In addition, fossil species have been described from Tertiary amber deposits: Dominican Republic (Wunderlich, 1988) (but note that the species described as Theridiosoma incompletum Wunderlich, 1988 is probably misplaced in that genus, see Penney (2006, 2008); Bitterfeld and Baltic (Wunderlich, 2004); Cretaceous amber from Myanmar (Wunderlich, 2012); and a single species, based on several specimens, has been described in rocks from the Cretaceous of Baissa, Transbaikalia (Selden, 2010). Here, a new species of ray spider is described from the newly discovered amber deposits of La Garnache, Vendée, France, possibly representing the only extant theridiosomatid genus known from the fossil record.
The amber originates from deposits of early Late Cretaceous age, either Middle Cenomanian, Turonian, or Early Santonian. The regional geology is rather complex, resulting in difficulties obtaining a precise age, and resolving this issue is still work in progress. For further details see the foreword paper in this volume (Perrichot & Néraudeau, 2014: 10A).
MATERIAL AND METHODS
One specimen, coll. Fanny Dupé (IGR.GAR-91) held in the collections of the Geological Institute and Museum of the University Rennes 1, Rennes, France. The fossil spider is preserved in a tiny sliver of amber which, prior to receipt by the author, was embedded in clear synthetic resin; total dimensions of the resin matrix: 6 × 3 × 0.5 mm. There are no syninclusions. Abbreviations used in the text and figures are as follows: ab = abdomen; AME = anterior median eyes; c = conductor; car = carapace; cl = cymbial lamella; cy = cymbium; em = embolus; L/R1-4 = left and right walking legs 1-4; p = pedipalp; pcy = paracymbium; PME = posterior median eyes; s = spine; t = trichobothrium.
ARANEAE Clerck, 1757
OPISTHOTHELAE Pocock, 1892
ARANEOMORPHAE Smith, 1902
THERIDIOSOMATIDAE Simon, 1881
BAALZEBUB Coddington, 1986
Type species.—Baalzebub baubo Coddington, 1986 by original designation.
Included species.—B. albonotatus (Petrunkevitch, 1930) (Puerto Rico), B. baubo Coddington, 1986 (Costa Rica, Panama, Brazil); B. brauni (Wunderlich, 1976) (Australia); B. nemesis Miller, Griswold, & Yin, 2009 (China); B. rastrarius Zhao & Li, 2012 (China); B. youyiensis Zhao & Li, 2012 (China). Coddington (1986) referred to 10–20 additional undescribed species, including additional geographic records from Mexico, Guatemala, Colombia, South Africa, Malaysia, New Guinea and New Zealand.
BAALZEBUB? MESOZOICUM n. sp.
Etymology.—The specific epithet relates to the Mesozoic Era, from which the fossil originates.
Material.—Holotype male (IGR.GAR-91) held in the collections of Geological Institute and Museum of the University Rennes 1, Rennes, France. The only known specimen.
Diagnosis.—Pedipalp of male with claw-shaped retrolateral ‘paracymbium’ fused to the cymbium basally and with a basal cymbial lamella; ‘conductor’ large and embolus extending distally beyond the cymbium. The palpal structure is similar to B. albonotatus (Petrunkevitch, 1930) but differs in having the embolus directed anteriorly rather than laterally.
Description.—Tiny spider, total body length approximately 1 mm. Carapace approximately 0.6 mm, not distinctly raised in the ocular area, and with a low clypeus. Eight eyes in two rows, anterior row recurved, posterior row straight. AME largest, contiguous, remaining eyes subequal, laterals contiguous, PME separated by slightly less than their diameter (Fig. B1). Sternum with promarginal sternal pits characteristic of the family, shield-shaped, as broad as long and extending between fourth coxae. Labium and maxillae broader than long. Leg formula (longest first) 1243, lacking unusual modifications. Femur 1 with distinct prolateral spine in distal half (Fig. B1); patellae 1 and 2 with both proximal and distal spine; patellae 3 and 4 with only distal spine. Tibia 1 and 4 with single dorsal spine close to patella; absence of similar spines on legs 2 and 3 cannot be confirmed with absolute certainty. Trichobothria difficult to see, but visible as follows: two on tibia 1, one on tibia 2, one on tibia 4. Tarsus with three claws; paired claws without teeth.
Abdomen lacking scuta, approximately 0.6 mm, damaged but was probably subspherical in life and overlapping carapace slightly; adorned with short setae. Spinnerets not clear, but appear short, compact and unmodified.
Pedipalp (Fig. B1) with highly sclerotized claw-shaped retrolateral ‘paracymbium’ fused to cymbium basally and with a basal cymbial lamella; ‘conductor’ large and embolus extending distally beyond cymbium. Palpal patella with single, long spine distally.
Theridiosomatidae is a poorly known or understood, exotic, cosmostropical family of tiny spiders, usually less than 2 mm in total body length (Coddington, 1986) with a relatively long geological history. Their true extant diversity far exceeds that which is known at present. The same is true for the constituent genera, including Baalzebub, considered in this paper (see previously under species included in the genus). This can make the placement of new fossil species in extant genera uncertain, especially when details of the pedipalps are obscured, and this is particularly true for older fossils from the Mesozoic.
Unfortunately, the bulbus structures are not clearly visible in the specimen described here, so it is not possible to differentiate between structures such as the tegulum, subtegulum and conductor. Nonetheless, the remaining palpal structures, especially the highly sclerotized claw-shaped retrolateral ‘paracymbium’ originating as an outgrowth of the cymbium basally and the basal cymbial lamella are considered sufficient to make a tentative placement of the new fossil species in the extant genus Baalzebub. Indeed, there are no particular characters that could be identified to exclude the fossil from this genus and to warrant the description of a new genus. Extant species of this genus prefer dark habitats and are often found in the interior of hollow logs or under large, fallen trees, a behaviour that would make them susceptible to becoming trapped in any secreted resin that may be present.
Interestingly, this Cretaceous French fossil shares features used in the diagnoses of Wunderlich's (2012) new Cretaceous genera, e.g. the presence of a single prolateral bristle on femur 1 (Leviunguis Wunderlich, 2012) and a very long and pointed paracymbium (Hypotheridiosoma Wunderlich, 2012). However, the overall palpal configuration excludes it from either of these genera. B.? mesozoicum represents the first Mesozoic fossil theridiosomatid assigned to an extant genus, suggesting a considerable antiquity for this spider lineage.
I am grateful to Vincent Perrichot and Fanny Dupé for making this specimen available for study and VP for providing photographs. Dmitri Logunov (Manchester Museum) is thanked for access to facilities and literature. The comments of two referees and emendation by the editors were helpful. The author acknowledges Siri Scientific Press for financial support.