First records and three new species of the family Symphytognathidae (Arachnida, Araneae) from Thailand, and the circumscription of the genus Crassignatha Wunderlich, 1995

Abstract The family Symphytognathidae is reported from Thailand for the first time. Three new species: Anapistula choojaiaesp. nov., Crassignatha seeliamsp. nov., and Crassignatha seedamsp. nov. are described and illustrated. Distribution is expanded and additional morphological data are reported for Patu shiluensis Lin & Li, 2009. Specimens were collected in Thailand between July and August 2018. The newly described species were found in the north mountainous region of Chiang Mai, and Patu shiluensis was collected in the coastal region of Phuket. DNA sequences are provided for all the species here studied. The relations of these symphytognathid species were tested using previously published phylogenetic analyses on micro orb-weavers. Also, we used micro CT analysis to build 3D models of the male genitalia and somatic characters of two species of Crassignatha Wunderlich, 1995. The molecular phylogeny and 3D models were used to discuss the taxonomy and circumscription of the currently valid symphytognathid genera, with focus on Crassignatha and Patu Marples, 1951. Based on this, three new combinations are suggested: Crassignatha bicorniventris (Lin & Li, 2009), comb. nov., Crassignatha quadriventris (Lin & Li, 2009), comb. nov., and Crassignatha spinathoraxi (Lin & Li, 2009), comb. nov. A new record of Crassignatha danaugirangensisMiller et al. 2014 is reported from Brunei.


introduction
The family Symphytognathidae includes some of the tiniest spiders known. According to a recent "Spider World Record" study (Mammola et al. 2017), this family holds the records for the smallest female, smallest male and smallest web. The Symphytognathidae has traditionally been put together with other small size araneoids (Anapidae, Mysmenidae, and Theridiosomatidae, sometimes with synaphrids and micropholcommatids) in a group informally called the symphytognathoids (Griswold et al. 1998;Hormiga and Griswold 2014). Although phylogenetic relationships among the Symphytognathidae have not been directly studied, some representatives have been used as part of other phylogenetic studies targeting the family Mysmenidae (Lopardo et al. 2011;Feng et al. 2019), as well as a broad scope analysis of the whole order Araneae (Wheeler et al. 2017;Kulkarni et al. 2020). Symphytognathids can be separated from other relatives by the following combination of characters: the loss of the posterior median eyes, reducing eye number to six (with the further loss of the anterior median eyes in the case of the foureyed genus Anapistula), fusion of the chelicerae (but see below), extreme reduction or loss of female pedipalp, the labium being much wider than long, loss of the colulus, sternum broadly truncated posteriorly, the absence of book lungs, and the presence of one or two promarginal cheliceral teeth originating from a common base (Forster and Platnick 1977;Wunderlich 2004;Miller et al. 2009;Lopardo et al. 2011;Hormiga and Griswold 2014).
The family is widespread in the tropics and subtropical regions, with most species described from the southern hemisphere. At present 8 genera and 74 species are recorded worldwide. In Asia, six genera and 29 species have been recorded (WSC, 2020). From these, 19 species have been recorded from China (Tong and Li 2006;Miller et al. 2009;Lin et al. 2013;Lin 2019) and six from South East Asia (Indonesia, Malaysia and Vietnam) (Wunderlich 1995;Harvey 1998;Miller et al. 2014). Here, the family Symphytognathidae is formally reported from Thailand for the first time, although Lopardo et al. (2011) did include a Thai symphytognathid in their study, designated SYMP-004-THAI, which was later identified as Crassignatha (Lopardo, pers. comm.). We describe three new species of the genera Anapistula and Crassignatha and expand the known distribution of Patu shiluensis. We used a combination of newly generated sequences and sequences available in GenBank to build a molecular phylogeny of the Symphytognathidae, and related micro orb-weaver families, in order to test the familial placement of our new species. Additionally, we discuss the taxonomy of the Symphytognathidae with emphasis on the genera Crassignatha and Patu.

Fieldwork
The symphytognathid specimens reported here were collected in Chiang Mai and Phuket, Thailand, between 16 July and 6 August 2018. All the specimens were captured using methods optimized for ground dwelling spiders: leaf litter sifting, Winkler extractors, pitfall traps and direct collecting on ground, and among sifted leaf litter.

Molecular data
To test the relationships and position of the novel species within the Symphytognathidae, we selected one specimen from each species we collected and used all four right legs to extracted genomic DNA and sequence six gene fragments: COI, H3, 12S, 16S, 18S, and 28S (primers in Suppl. material 1) following Miller et al. (2010) and Wheeler et al. (2017) protocols. Sequences were edited in Geneious Prime 2020.0.5 and deposited in GenBank; accession numbers are reported in Table 1. We used these sequences and a selection of taxa previously used to test the phylogeny of mysmenid spiders (Lopardo et al. 2011;Feng et al. 2019). In total, 47 species of "symphytognathoids" from the families Anapidae, Mysmenidae, Symphytognathidae and Theridiosomatidae were used. Two more species of Tetragnathidae were used as an outgroup to the symphytognathoids. We used MAFFT v.7.450 online (https://mafft.cbrc.jp/alignment/server/) with default parameters to align the sequences. Matrix was built using in Sequence Matrix v.1.8 (http://www.ggvaidya. com/taxondna/); matrix available in Suppl. material 1. Each locus was treated as a partition and examined with jModelTest2 (Darriba et al. 2012) in CIPRES (Miller et al. 2010) to get the best model fit for each; GTR+I+G was selected in all cases. Our datasets were analyzed using MEGA X (Kumar et al. 2018) for Maximum Parsimony (SPR, default values, bootstrap = 1000); RaXML (Stamatakis 2014) in CIPRES for Maximum Likelihood (GTR, bootstrap = 1000) and MrBayes v. 3.2.6 (Ronquist and Huelsenbeck 2003) in CIPRES for the Bayesian Inference (GTR+I+G, two independent runs with one cold and three heated chains, mcmc = 50,000,000 gen, samplefreq = 1000, burnin = 2500; partitions are indicated in the NEXUS file). The program Tracer v. 1.7.1 (Rambaut et al. 2018) was used to analyze the performance of our BI analyses.

Morphological data
Specimens were photographed with a Nikon DS-Ri2 camera attached to a Leica DM 2500 microscope. Specimens were observed in ethanol using semi-permanent  (Coddington 1983). Female genitalia were dissected, digested using pancreatin solution (Alvarez-Padilla and Hormiga 2007), and cleared with methyl salicylate. For the 3D scans, whole male spiders were stained in 1% iodine in 70% et-OH for 24 hours. Specimens were fixed in a modified 10 ul pipette tip and scanned using a Zeiss X-radia 520 versa. 3D model and subsequent segmentation of the internal ducts of male pedipalps were done in Avizo 9.5.0. All the specimens have been deposited in the collection of the Naturalis Biodiversity Center, Leiden, the Netherlands. Additionally, two males of Crassignatha danaugirangensis Miller et al., 2014, recently collected in Brunei, were analyzed using micro-CT scanning. 3D reconstructions were used to clarify some anatomical details of this species and the genus Crassignatha, including the internal and external structure of the male pedipalp, cheliceral armature, and carapace texture. Nomenclature of the genital structures was based on Harvey (1998) and Lin et al. (2013) for Anapistula, and Lin andMiller et al. (2009) for Crassignatha and Patu. Abbreviations in text and figures: A -Epigynal atrium; AME -Anterior median eyes; BI -Bayesian Inference; C -Conductor; C1 -Conductor, anterior projection; C2 -conductor, posterior projection; Cd -Copulatory duct; Ch -Chelicera; ChT-cheliceral tooth; Co -Copulatory opening; Ct -cymbial tooth; Cy-Cymbium; E -Embolus; Em-Embolic membrane; EMD -Epigynal median duct; F -Femur; Fd -Fertilization duct; Lb -lateral branch of the EMD; LE -lateral eyes; Mcl -male leg II mating clasper; ML -Maximum Likelihood; MP -Maximum Parsimony; Pa -Patella; Pc -Paracymbium; PME -Posterior median eyes; S -Spermatheca; Sa -Secretory ampulla; Sc -Epigynal scape; Sd -Spermatic duct; T -Tibia.

Phylogenetic analysis
Tree topologies inferred by the different phylogenetic analyses performed (Figs 1-3) show some consistencies in several groupings; however, low support values are common, especially in the MP and ML trees. There is an inconsistent and problematic placement of the Symphytognathidae in relation to the Anapidae. All tree analyses recovered Mysmenidae as monophyletic and a sister group of Anapidae + Symphytognathidae. Theridiosomatidae is recovered as monophyletic in the MP and ML analyses with medium to high support (Figs 1, 2); nevertheless, in the BI the position of this family is not resolved (Fig. 3). Similarly, the position of Micropholcommatinae, currently considered part of the Anapidae, is not clear, being found as paraphyletic in the MP, unresolved in the BI, and a poorly supported monophyletic clade in the ML analysis (Figs 1-3). The Anapidae is closely related to the Symphytognathidae in all our trees (with the notable exception of the two micropholcommatines in the ML and BI); however, it appears as a poorly supported monophyletic group in the ML  Lopardo et al., (2011) andFeng et al., (2019) plus the four symphytognathid species from our study (in red). Numbers at nodes indicate bootstrap support. Note the paraphyly of Anapidae and the high support of Crassignatha and Patu in the Symphytognathidae. Molecular vouchers used for previous "symphytognathoid" studies (Lopardo et al. 2011;Lopardo and Hormiga 2015) identified to genus level by L. Lopardo (pers. comm.) as follows: ■ Crassignatha (apparently conspecific with C. seeliam); Patu; and ▲Symphytognatha. Numbers at nodes indicate bootstrap support. Note the long branch of Anapistula and its position within Anapidae; and the high support of Crassignatha and Patu in the Symphytognathidae. Molecular vouchers used for previous "symphytognathoid" studies (Lopardo et al. 2011;Lopardo and Hormiga 2015) identified to genus level by L. Lopardo (pers. comm.) as follows: ■ Crassignatha (apparently conspecific with C. seeliam); Patu; and ▲Symphytognatha.  Lopardo et al. (2011) andFeng et al. (2019) plus the four symphytognathid species from our study (in red). Numbers at nodes indicate percent posterior probabilities. Note the unresolved relations of the Anapidae and the highly supported monophyly of Symphytognathidae. Molecular vouchers used for previous "symphytognathoid" studies (Lopardo et al. 2011;Lopardo and Hormiga 2015) identified to genus level by L. Lopardo (pers. comm.) as follows: ■ Crassignatha (apparently conspecific with C. seeliam); Patu; and ▲Symphytognatha. (Fig. 2), and paraphyletic in the MP and BI (Figs 1, 3). The Symphytognathidae appear monophyletic with moderate to high support in all the analyses (Figs 1, 2). In the BI analysis, this family is monophyletic and highly supported but found in an unresolved branch that includes the paraphyletic Anapidae (Fig. 3). The internal relations of the Symphytognathidae are similar in all our trees forming one clade that includes Symphytognatha picta, one species (SYMP_008_DR) identified as Symphytognatha, one as Patu (Patu_SYMP_001_DR), and one more (SYMP_005_AUST) that remained unidentified. The other clade recovers the rest of the Patu species + Crassignatha. Here, two terminals (SYMP_002_MAD and SYMP_003_MAD) are closer to Patu shiluensis and related to the three Crassignatha representatives; and two other (SYMP_006_AUS and SYMP_007_AUS) are consistently found outside of the Crassignatha + Patu clade. SYMP-004-THAI consistently clusters with Crassignatha seeliam sp. nov., and unpublished morphological observations (Lopardo, pers. comm.) are consistent with the possibility that these are conspecific.

Micro-CT and 3D modelling
The micro computed tomography scans allowed us to observe in detail small structures of the surface and internal ducts of the male genitalia ( Fig. 4a-f ). Structures like the cheliceral teeth ( Fig. 5a), cephalothorax tubercles (Fig. 5b, c), and mating clasper on male tibia II (Fig. 5d, e) were also observed. We reconstructed 3D models of the whole body surface of Crassignatha seeliam (Fig. 6a, b) and Crassignata danaugirangensis ( Fig. 6c, d). All of these images were important to examine, interpret and clarify the diagnostic characters of the genus Crassignatha. Additional views of the pedipalps, spermatic ducts and habitus can be found in the Suppl. material 2, 3)     Etymology. The species epithet is a Latinized matronym of the second authors' daughter.
Diagnosis. Female genitalia in Anapistula show little morphological variation between congeneric species making it generally difficult to tell species apart. However, A. choojaiae sp. nov. can be distinguished from most Anapistula species by the presence of an epigynal atrium; A. aquytabuera Rheims & Brescovit, 2003, A. pocaruguara and A. ybyquyra Rheims & Brescovit, 2003from Brazil, A. panensis Lin, Tao, and Li 2013and A. zhengi Lin, Tao, and Li 2013from China, and A. seychellensis Saaristo, 1996 from the Seychelles also share this character. A. choojaiae differs from all of these by the relative size and shape of the atrium, the width of the EMD and the bifurcation of the Lb (compare Figs 8d and 9c to Rheims and Brescovit 2003: figs 16, 18, 21;Lin et al. 2013: figs 3, 4, 8, 9; and Saaristo 1996: fig. 3). Male pedipalp of A. choojaiae similar to A. panensis in the overall shape of the palp and in having C1 and C2 roughly the same length, but differs on the width of C1 in respect to C2 and the length of the E in relation to C1 (compare Figs 7c, 9a to Lin et al. 2013: figs 1, 2).
Vulva: Epigynal plate flat, without scape. Atrium semi-circular as wide as inner distance between S (Fig. 8c). Spermathecae spherical, heavily sclerotized in relation to the rest of the body (Fig. 8d). Cd easy to distinguish inside the EMD. LB diverging from the EMD forming a "Y" (Figs 8d, 9c). Fertilization ducts very short and difficult to see, they appear as small bumps on the distal portion of Lb (Fig. 9c) Etymology. The species epithet is a derivation of the Thai seeliam (square), in reference to the shape of the abdomen in dorsal view.
Vulva: Epigynum with wide scape directed ventrally, heavily sclerotized at the tip (Fig. 11c). Copulatory opening at the tip of scape (Figs 11d, 12c, d). Spermathecae spherical, slightly more sclerotized than epigynum, separated by ca. 2× their diameter (Fig. 11d). Copulatory ducts very long, coiling over themselves before connecting to S. Fertilization ducts as long as S width, projecting dorsally (Figs 11d, 12c).   Etymology. The species epithet is a derivation of the Thai seedam (black), in reference to the dark coloration of this species. Diagnosis. Crassignatha seedam sp. nov. differs from other Crassignatha species by having a nearly round abdomen instead of triangular or squared, and having the epigynum bulging ventro-posteriorly but not forming an scape (compare Figs 13d and 15b, d to Fig. 12c; Lin and Li 2009: fig. 10;and Miller et al. 2009 fig. 76d, h).
Description. Carapace brown with smooth texture (Fig. 13b). Legs light brown, slightly darker on the distal portion its segments. Abdomen sub-spherical, darker than carapace with sparse light patches (Fig. 13a, b). Vulva: Epigynum weakly sclerotized but covered by small dark patches (Fig. 13d), bulging ventrally. Copulatory openings broad but not forming an atrium (Fig. 15b). Spermathecae spherical, much more sclerotized than epigynum, separated by 0.5× their diameter (Fig. 13d). Copulatory ducts long, coiling over themselves before connecting to S. Fertilization ducts as long as S width, connecting very close to Cd and projecting dorsally (Fig. 15b, d).
Female Distribution. Known only from its type locality, Shilu Town, Hainan Province, China and the specimens collected for the present work.
Notes. Small somatic variations can be seen between the specimen we collected in Thailand and the ones previously described from China (compare Fig. 14b to   fig. 11). However, we did not find any objective differences in the female genitalia.
Secretory ampullae (Figs 14d, 15a) were very evident in our specimens; these glandular structures might be homologous to the accessory glands in Lopardo and Hormiga (2015). These structures were found in one anapid (Tasmanaspis) and several mysmenids, but scored as absent or unknown for all the symphytognathids. The authors of this species mentioned it to be close to Patu silho Saaristo, 1996 from Seychelles. The possibility of P. silho not being a true Patu was discussed by its author (Saaristo 1996;2010) mentioning evident differences on somatic and sexual characters between P. silho and other Patu species. Nevertheless, the author deemed appropriate to place it in this genus. We also consider this species might be misplaced in Patu but would need further and more detailed analysis out of the scope of this work to clarify it (see discussion on Patu relationships below).

Discussion
The monophyly of the Symphytognathidae and its relations to other symphytognathoid spiders have resulted in complications and inconsistencies across different studies. The symphytognathoids were first recognized in a morphological study being formed by four putatively monophyletic families Anapidae, Symphytognathidae, Mysmenidae and Theridiosomatidae (Griswold et al. 1998). The monophyly of this clade has been tested several times using different molecular approaches targeting specific families (Rix et al. 2008;Lopardo et al. 2011;Feng et al. 2019), the Orbiculariae (Fernández et al. 2014), and the whole order Araneae (Wheeler et al. 2017;Kulkarni et al. 2020). However, only a few representatives of the family Symphytognathidae have been used rendering their position and relations largely unexplored. Here, we built on two previous studies that used nine species of Symphytognathidae to test the relations of the Mysmenidae (Feng et al. 2019;Lopardo et al. 2011). Similarly to Feng et al. (2019) low node supports were common in our trees, especially for MP and ML; still, the topologies we observed when including our four species are consistent with the results from these studies. All of our analyses showed a close relationship between the Symphytognathidae and the Anapidae (Figs 1-3). This relationship has also been recovered in previous works (Griswold et al. 1998;Lopardo et al. 2011;Wheeler et al. 2017;Feng et al. 2019). Although tenuous due to the few terminals included, our study fails to recover the monophyly of the Anapidae and the position of micropholcommatids within this family. Our BI tree could not fully resolve the relations between the Anapidae and Symphytognathidae; similar issues have been observed before for the symphytognathoids (Rix et al. 2008;Lopardo et al. 2011;Dimitrov et al. 2012;Fernández et al. 2014;Feng et al. 2019). This has been explained by either the limited set of loci and the relatively low taxon sampling (Feng et al. 2019) or an indication of the polyphyly of the "symphytognathoids" as suggested by three broad scoped phylogenies (Dimitrov et al. 2012;Fernández et al. 2014;Wheeler et al. 2017). Nevertheless, Symphytognathoids were found to be a highly supported monophyletic group in a recent study that used ultraconserved elements (UCE) from 16 species across the four principal symphytognathoid families (Kulkarni et al. 2020) The internal relations of the Symphytognathidae in our analyses are still unresolved. Most of Lopardo's identifications (pers. comm.) are found in the Crassignatha + Patu clade. From these, SYMP_004_THAI (identified to Crassignatha; presumably conspecific to C. seeliam), and SYMP_002_MAD and SYMP_003_MAD (Patu) group together with the other representatives of the genera they were identified to. But the placing of two more, SYMP_006_AUS and SYMP_007_AUS (Patu), is more ambiguous being found outside of the Crassignatha + Patu clade rendering Patu paraphyletic. This clade and its internal relations are highly supported in all our trees (Figs 1-3). Other two sequences, SYMP_008_DR (Symphytognatha) and Patu_SYMP_001_DR, are consistently grouped in another branch of the Symphytognathidae together with Symphytognatha picta and other unidentified symphytognathid (Figs 1-3) suggesting that Patu_SYMP_001_DR might be misidentified. The position of Anapistula within the Symphytognathidae is also problematic. Anapistula choojaiae has a very long branch that is recovered as a sister to Tasmanapis strahan Platnick & Forster, 1989 with moderate to high support in the ML and BI (Figs 2, 3). In these two analyses, this branch is related to other Anapidae having much higher support values in the BI than the ML (Figs 2, 3). Nevertheless, the recent UCE study by Kulkarni et al., (2020) places this genus next to Patu in a highly supported but taxonomically limited Symphytognathidae. Solving the internal relations of the families Anapidae and Symphytognathidae, and clarifying their delimitations would need a much more detailed examination with a broader taxonomic sample.
The minute size of the symphytognathid spiders complicates the observation of diagnostic traits. Examination and interpretation of many characters require higher magnifications than those a dissection microscope can give. Therefore, SEM images have been previously used in the taxonomy of this family (Forster and Platnick 1977;Rheims and Brescovit 2003;Miller et al. 2009, among others). Unfortunately, the process for getting SEM images is destructive; therefore, rare specimens or short series are not usually prepared in this way and some characters cannot be properly observed. Here we used micro-CT scanning to overcome this issue and get clear views of important characters without damaging the specimens. 3D reconstruction has been used before to elucidate surfaces and internal structures of spider genitalia Sentenská et al. 2017;Dederichs et al. 2019). Nevertheless, ours are, to the best of our knowledge, the smallest palps that have been processed using this method. This was challenging in itself since we wanted to preserve the samples without critical point drying, a method commonly used in micro-CT scanning (Sentenská et al. 2017;Keklikoglou et al. 2019;Steinhoff et al. 2017Steinhoff et al. , 2020. The tiny size of the palps, less than 0.2 mm wide, did not allow to properly fix the dissected organ and keep it from moving during the scanning process. We attempted to fix the palp in agarose gel inside a 10 µl pipette tip, but the contrast of the resulting scans was too low to allow any observations. This problem was solved by scanning the entire spider (without dissecting the palp) in Et-OH 70% inside a modified 10 µL pipette tip that was in turn inside a 0.5 ml Eppendorf tube (Fig. 5f ) in a similar fashion to Lipke et al. (2015), and Sombke et al. (2015). With this approach we were able to reconstruct the long and complicated internal ducts of the male genitalia (Fig. 4b, c, e, f ), as well as the surface of the external somatic and genital morphology (Figs 4a, b, 5a-e, 6a-d; Suppl. material 2, 3). Other internal structures of the male palp, probably glands, could be observed but would require more detailed examination out of the scope of the present work to accurately determine their nature; therefore, they are not shown in our 3D models. Images obtained through 3D reconstruction were used to interpret and discuss the diagnostic characters of the genus Crassignatha and compare them to other Symphytognathid genera in Table 2. Forster and Platnick (1977) reviewed the Symphytognathidae and its component genera. Five of the eight currently recognized symphytognathid genera were included: Anapistula Gertsch, 1941, Curimagua Forster & Platnick, 1977, Globignatha Balogh & Loksa, 1968, Patu Marples, 1951, and Symphytognatha Hickman, 1931. Crassignatha Wunderlich, 1995 was described based on a single male specimen from peninsular Malaysia. This genus has been associated with several families (Synaphridae, Anapidae, Mysmenidae, Symphytognathidae; Marusik and Lehtinen 2003;Wunderlich 2004;Miller et al. 2009;Lopardo and Hormiga 2015) and is currently considered a symphytognathid. Two other genera currently cataloged as Symphytognathidae, Iardinis Simon, 1899 Anapogonia Simon, 1905, are unrecognizable (Levi andLevi 1962;Forster and Platnick 1977;Platnick and Forster 1989;Lopardo and Hormiga 2015). Although spider taxonomy generally relies heavily on genitalia, little in the way of descriptive text or helpful depictions of genitalic characters was offered in Forster and Platnick's (1977) revision. Table 2 summarizes some important diagnostic characters of the currently accepted symphytognathid genera in an attempt to clarify the taxonomic inconsistencies in this family.
Other than their small size, the characteristic that is perhaps most strongly associated with the Symphytognathidae was the fusion of the chelicerae (Forster and Platnick 1977). But the degree of fusion is variable across the family and is particularly problematic in the genus Patu. The two species originally placed in Patu were reported as having the chelicerae fused for approximately half their length, but the degree of fusion was apparently less extensive in the genotype Patu vitiensis than in Patu samoensis, the other species described (Marples 1951). Subsequent authors have generally characterized Patu as having the chelicerae fused only at the base (Forster and Platnick 1977). Curiously, Forster (1959) made no mention of cheliceral fusion in Patu, but he did report basal fusion of the chelicerae in two genera (Pseudanapis and Textricella) that were subsequently transferred to Anapidae. So, assessing the presence or absence of basal cheliceral fusion is not always straight forward in practice. Some (but not all)  (Brignoli 1980;Forster and Platnick 1977;Gertsch 1960;Levi and Levi 1962;Lopardo and Hormiga 2015) (Marples 1951(Marples , 1955Forster 1959;Forster and Platnick 1977;Saaristo 1996) (Hickman 1931;Forster and Platnick 1977;Lopardo and Hormiga 2015;Lin 2019) Number of species is based on the WSC (2020). *Type species Iardinis weyersi Simon, 1899 is considered a nomen dubium; two species placed in this genus by Brignoli (1978Brignoli ( , 1980 remain cataloged here (WSC 2020).
Patu species known from males have a number of ventral distal macrosetae on tibia II, a characteristic scored as present in Lopardo's Patu specimens SYMP_002_MAD and SYMP_006_AUS and absent in Patu_SYMP_001_DR and Symphytognatha picta (Lopardo and Hormiga 2015); this leg II clasper is otherwise found only in Crassignatha.
Genotype Crassignatha haeneli Wunderlich, 1995 features a textured carapace and a distinctive ventral spur on tibial II (Fig. 5d, e;Wunderlich 1995: figs 14, 15, 17). The chelicerae are not conspicuously fused and are armed with a single bifid tooth (Fig. 5a); a character also scored for three species (SYMP_002_MAD, SYMP_006_AUS and SYMP_007_AUS, later on identified as Patu) used in Lopardo and Hormiga (2015). Miller et al. (2009Miller et al. ( , 2014 placed several additional species in Crassignatha, including the first descriptions of females. In all of Miller's species where males are known, they possess a unique abdominal scutum surrounding the abdomen laterally and posteriorly. In most Crassignatha species, the female genitalia consists of a pair of robust round spermathecae separated by approximately their diameter, copulatory ducts that loop and switchback along their path, and a short, robust scape (Miller et al. 2009: figs 76, 79, 89A-D); only C. longtou and C. seedam sp. nov. have a transverse bulge and not a scape (Miller et al. 2009: figs 89E, F, 91F). Wunderlich (1995) stated that Crassignatha haeneli lacked an abdominal scutum, and among the Symphytognathidae, only Anapistula boneti and Miller's Crassignatha species have a scutum (but see Patu spinathoraxi, below). A dissection of Crassignatha chelicerae indicated that they were indeed fused at the base (Miller et al. 2009: fig. 78A). It is however worth noting that the 3D scan of Crassignatha presented here do not appear to indicate cheliceral fusion (Fig. 5a). It was also determined that most of these Crassignatha species have an asymmetrical split in the cheliceral tooth with a small peak on the mesal side of the tooth; only C. longtou has two subequal teeth. Crassignatha species known from the male all have a group of 1-3 strong ventral setae on male tibia II (Miller et al. 2015: figs 74E, 77D, 80E, 83E;Miller et al. 2009: fig. 1F). One species had the abdomen modified with a pair of posteriolateral lobes (Miller et al. 2009: figs 86D-F), not as conspicuous in other species (Fig. 6b, d), or generally round or oblong.

Modern symphytognathid taxonomy in Asia
2009 was a big year for little spiders in Asia. Four papers described a total of 18 symphytognathid species from China, Japan, and Vietnam Miller et al. 2009;Shinkai 2009). These were distributed across the genera Anapistula, Crassignatha, and Patu.  described five new Patu species from China. Again, fusion of the chelicerae only near the base was declared as a characteristic of Patu. Chelicerae of all species were illustrated as fused, but no details were provided in the text. Of these five species, three show characters that match the diagnostic characters of Crassignatha instead of Patu: Patu bicorniventris , known from the female only, has an asymmetrically bifid cheliceral tooth : figs 2C, 2D) resembling those typical of Crassignatha (Miller et al. 2009: fig. 78A). It also has modifications to the abdomen consisting of two posteriolateral lobes and a straight posterior margin, resembling Crassignatha ertou (Miller et al., 2009 figs 86D-86F). The female genitalia of Patu bicorniventris resembles most Crassignatha females described in Miller et al. (2009), featuring conspicuous spermathecae with convoluted copulatory ducts leading to a knob-like median scape. Patu quadriventris  shares with P. bicorniventris an abdomen that is truncated posteriorly, but lacks the posteriolateral lobes. The female genitalia is consistent with Crassignatha. The cymbium of the male pedipalp has a distal apophysis (CS in Lin and Li 2009: fig. 9C) that strongly resembles the Ct in Crassignatha (Figs 9a, 13a, d;Miller et al. 2009: figs 75, 77B, 81, 82B, 84, 87, 88). Patu spinathoraxi  has distinctive spikey tubercles covering the carapace.
It closely resembles (but is not conspecific with) Crassignatha longtou Miller, Griswold & Yin, 2009, which was described from the female only. The female genitalia of both species are similar, featuring round spermathecae with ducts that run ectally before turning back toward the middle and terminate in a pair of conspicuous posterior openings; they contrast with Crassignatha in that they lack a robust scape. The male has a medially split abdominal scutum, a single ventral macroseta on tibia II, and a distal apophysis of the cymbium similar to those found in Crassignatha (CS in   fig. 16C). These two species are clearly congeneric; whether they are best placed together in Crassignatha, or in their own new genus, is debatable.
Thanks to Lara Lopardo for the morphological identifications of the voucher specimens used in Lopardo et al. (2011). Funding for the first author was provided by CONACyT Becas al extranjero 294543/440613, Mexico. All specimens used in this study were collected under permit 5830802 emitted by the Department of National Parks, Wildlife and Plant Conservation, Thailand.