NovttatesAMERICAN MUSEUM PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET NEW YORK. N.Y. 10024 U.S.A. NUMBER 2707 FEBRUARY 26, 1981 ROBERT J. RAVEN AND NORMAN I. PLATNICK A Revision of the American Spiders of the Family Microstigmatidae (Araneae, Mygalomorphae) i.. AMERICAN MUSEUM Norntates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 2707, pp. 1-20, figs. 1-54 February 26, 1981 A Revision of the American Spiders of the Family Microstigmatidae (Araneae, Mygalomorphae) ROBERT J. RAVEN1 AND NORMAN I. PLATNICK2 ABSTRACT The tribal grouping Microstigmateae Roewer is Venezuelan species Pseudonemesia parva Ca- removed from the Dipluridae and elevated to fa- poriacco is described for the first time, and a new milial rank. The subfamily Pseudonemesiinae Ca- species, P. kochalkai, is described from Colom- poriacco is transferred from the Ctenizidae to the bia. A genus (Ministigmata) described for a new Microstigmatidae. The family is suggested to be species (M. minuta) from Brazil is hypothesized the sister group of the Mecicobothriidae plus to be more closely related to the South African Hexathelidae and Dipluridae. The male of the genus Microstigmata than to Pseudonemesia. INTRODUCTION The unusual mygalomorph spiders which (Dipluridae and Ctenizidae), neither of form the subject of this paper have been pre- whose defining features they share. viously studied by only three other arach- Hewitt (1916) had difficulty assigning the nologists: Hewitt (1916, 1925), Lawrence first known species, Microstigmata geophil- (1938), and Caporiacco (1955). The New um from Grahamstown, South Africa, to a World species, in particular, have long been family. He excluded the genus from the overlooked both because of their rarity in Ctenizidae because of the absence of a che- collections and their extremely small size liceral rastellum and placed it in the Dipluri- (adult males, reported here for the first time, dae, even though he was "unable to discover range from 1 to 3 mm. in total length and definite indication of close relationship to thus rival the mecicobothriid genus Hexu- any of the known genera" of that family. If rella and the diplurid genera Microhexura the species actually was a diplurid, the pres- and Masteria as the world's smallest myga- ence of two rows of teeth on the paired tarsal lomorphs). Moreover, these spiders illus- claws would associate it with the subfamily trate the difficulties currently plaguing the Diplurinae, and the short posterior lateral higher classification of mygalomorphs, hav- spinnerets would exclude it from diplurine ing been described in two different families subgroups other than the Brachytheleae and I Assistant Arachnologist, Queensland Museum, Gregory Terrace, Fortitude Valley, Queensland 4006, Australia. 2 Associate Curator, Department of Entomology, American Museum of Natural History; Adjunct Professor, Department of Biology, City College, City University of New York. Copyright ©) American Museum of Natural History 1981 ISSN 0003-0082 / Price $1.65 2 AMERICAN MUSEUM NOVITATES NO. 2707 FIGS. 1-4. Book-lung openings, ventral views. 1. Microstigmata sp., 560x. 2. Microstigmata sp., 2400x. 3. Sphodros sp. (Atypidae), 125 x . 4. Paratropis sp. (Paratropididae), 125 x. similar forms. However, Hewitt noted that of Microstigmata from Natal, gave no indi- Microstigmata lacks the tarsal scopulae typ- cation of his views on their affinities beyond ical of the Brachytheleae, and concluded labeling them as members of a "primitive only that the genus "can be considered as genus of four-lunged spider" (p. 460). one of the connecting links between the two Caporiacco (1955) had similar difficulties families Ctenizidae and Dipluridae" (1916, p. in placing his new Venezuelan spider, Pseu- 206). donemesia parva. He noted that it generally Discovery of the male of the species did resembled diplurids but (like Microstigmata) not lead Hewitt (1925) to change his assess- is excluded from that family by having short ment of the familial position of Microstig- posterior lateral spinnerets with short apical mata, but in addition to the Brachytheleae segments. He assigned the species to the he did indicate a possibly close relationship Ctenizidae and established for it the new to the family Paratropididae. Lawrence subfamily Pseudonemesiinae, differing from (1938), in describing two additional species most other ctenizids in having only two spin- 1981 RAVEN AND PLATNICK: MICROSTIGMATIDAE 3 I -10 IJ .i..: _aZ FIGS. 5-10. Cuticle of tarsus I, dorsal views. 5. Pseudonemesia parva Caporiacco, 1150x. 6. P. kochalkai, new species, 1350x. 7, 8. Ministigmata minuta, new species; 7, 1300x, 8, 5250x. 9, 10. Microstigmata sp.; 9, 210x, 10, 2000x. 4 AMERICAN MUSEUM NOVITATES NO. 2707 0 FIGS. 11-14. Claws of leg I, ventrolateral views. 11. Microstigmata sp., 240x. 12. Ministigmata minuta, new species, 1250x. 13. Pseudonemesia parva Caporiacco, 1050x. 14. P. kochalkai, new species, i1OOx. nerets and lacking a cheliceral rastellum. As ican species, has allowed us to present below the presence of a rastellum is virtually the a reassessment of these spiders and their re- only defining character of the Ctenizidae, lationships. We will first argue that Micro- Caporiacco's assessment is fully as proble- stigmata, Pseudonemesia, and the new matical as Hewitt's. Caporiacco did not as- species described below represent a distinct sociate Pseudonemesia with Microstigmata, and monophyletic group, and then inquire as probably because the small size of the former to what their sister group may be and how prevented him from observing some of the the various microstigmatid species may be characters they share. interrelated. Thus it is clear even from the literature that the present taxonomic positions of these MONOPHYLY two genera are untenable. The discovery of There are three characters that seem to be adult males that can be attributed to P. par- synapomorphies uniting the species treated va, as well as of two additional South Amer- below as microstigmatids: the tiny, oval 1981 RAVEN AND PLATNICK: MICROSTIGMATIDAE 5 I I I I FIGS. 15-20. Claws of leg I, lateral views (15-19), ventral view (20). 15. Ministigmata minuta, new species, 1160x. 16. Pseudonemesia kochalkai, new species, 750x. 17. Nemesia sp. (Ctenizidae), 240x. 18. Diplura sp. (Dipluridae), 240x. 19, 20. Diplothelopsis sp. (Pycnothelidae), 125x. 6 AMERICAN MUSEUM NOVITATES NO. 2707 I p- . -0 I :.' '. '. r, -4 jppr,..,, .. :,?, -, .. FIGS. 21-24. Cuticle and setae of leg I, dorsolateral views. 21. Paratropis sp. (Paratropididae), 240x. 22. Microstigmata sp., 240x. 23, 24. Ministigmata minuta, new species; 23, 1040x, 24, 2400x (whorled seta at base of claws). book-lung openings, the scaly cuticle of the begins to approach the microstigmatids in legs and palpi, and the tarsal claw dentition. this character is the Paratropididae. Some Hewitt (1916) first recognized the peculiari- paratropidids, particularly small ones, have ties of the book-lung apertures of Microstig- book-lung openings that are reduced in size mata. Whereas in other mygalomorphs the (perhaps an adaptation to living in, and hav- book-lungs open through long, transverse ing their bodies encrusted and camouflaged slits (figs. 3, 4), in Microstigmata the open- by, dirt), but they have a sclerotized rim only ings are unusually small oval pores com- along their anterior borders and generally re- pletely surrounded by a sclerotized rim, with tain the slit-like form found in other myg- the opening consisting "of a rather cribri- alomorphs (fig. 4). The peculiar book-lung form plate reminiscent of the stigmata of cer- openings of microstigmatids cannot be dis- tain insects, which is provided with a few missed as merely being adaptations to small minute black hairs on its surface" (Law- size and a resulting higher rate of water loss, rence, 1938, p. 460; figs. 1, 2). The only other for Microstigmata species are no smaller mygalomorph group known to us that even than many other mygalomorphs, and the 1981 RAVEN AND PLATNICK: MICROSTIGMATIDAE 7 V.A 0 j A 1014 I" .1 4 a I ., i"* A 14. a :-, .4 .14 ,a,* 10* W. ..4 I 4. -,I 1. ... i FIGS. 25-28. Serrula, anterior views. 25. Microstigmata sp., 500x. 26. Ministigmata minuta, new species, 1250x. 27. Pseudonemesia parva Caporiacco, 725x. 28. P. kochalkai, new species, 600x. modifications do not occur in other tiny of atypid, antrodiaetid, hexathelid, and di- forms like Hexurella, Microhexura, and plurid legs can be found in Gertsch and Plat- Masteria. nick, 1979, figs. 5, 7, 9, 15, 17, 19, 21, 23, 25, Secondly, the microstigmatids are distinc- 27). Interestingly, spiders of the suborder tive in having the cuticle of the legs and ped- Mesothelae have similar (although less ele- ipalps covered with flattened scales, semi- vated) digitiform pustules (Gertsch and Plat- circular or triangular in shape and highest at nick, 1979, figs. 11, 13), as do a few species their distal ends. These are most easily seen of Dipluridae (Ixamatus and a related genus in Pseudonemesia (figs. 5, 6), but they also in the Diplurinae; Raven, 1980a, figs. 11-13), occur in Mfcrostigmata and the new genus but there are no scales underlying the pus- Ministigmata, where they bear numerous tules in those species. digitiform pustules (figs. 7, 9); the outlines of Finally, the form of the tarsal claws may the scales in these species are marked by also be synapomorphic for microstigmatids. longer pustules (figs. 8, 10). Such scales are The paired (superior) claws each bear two not known to occur in other mygalomorphs rows of teeth (figs. 11-14), a condition un- (comparable scanning electron micrographs usual among mygalomorphs but also found 8 AMERICAN MUSEUM NOVITATES NO. 2707 .A. FIGS. 29-32. Tarsal organ of leg I, lateral views. 29. Microstigmata sp., 50Ox. 30. Ministigmata minuta, new species, 5250x. 31. Pseudonemesia parva Caporiacco, 2800x. 32. P. kochalkai, new species, 1l,500x. in the Pycnothelidae, Dipluridae (Dipluri- claws of other diplurines (such as Teyl) re- nae), and some Ctenizidae (the Aporopty- semble this ctenizid condition more than the cheae and Nemesieae of Simon, 1892).