Kryptochroma: a new genus of bark-dwelling crab spiders (Araneae, Thomisidae)

A recent phylogenetic analysis has shown that the genus Stephanopis comprises several different lineages of bark-dweller crab spiders. The ones with South American distribution that present a close relationship with other Neotropical genera like Epicadus, Onocolus, Rejanellus and Epicadinus were recovered in a single clade, with good support and stability. Here, we present a taxonomic review of Stephanopis species attributed to the ‘pentacantha clade’, proposing the new genus Kryptochroma Machado gen. nov. to accommodate them. New distribution records are provided and the following species are described for the fi rst time: Kryptochroma gigas Machado & Viecelli gen. et sp. nov., Kryptochroma hilaris Machado & Teixeira gen. et sp. nov., Kryptochroma quadrata Machado & Viecelli sp. nov. and Kryptochroma septata Machado & Teixeira sp. nov. The species Stephanopis borgmeyeri is considered a nomen dubium, Stephanopis aheneus is a junior synonym of Epicadus tuberculatus, Stephanopis quimiliensis is transferred to Ulocymus and Stephanopis stelloides is transferred to Epicadus, being Epicadus stelloides the senior synonym of Stephanopis salobrensis, Stephanopis trilobata and Epicadus caudatus.


Introduction
The morphological aspects and taxonomic boundaries of Neotropical stephanopines have been extensively studied during the past years (Machado et al. 2015(Machado et al. , 2019aSilva-Moreira & Machado 2016). Meanwhile, p hylogenies based on morphological and molecular data were congruent in recovering some close related genera, corroborating classic propositions for the possible existence of tribes or even certain "groups" in this subfamily (Benjamin 2011;Benjamin et al. 2008;Wheeler et al. 2017;Machado et al. 2017Machado et al. , 2019bMachado & Teixeira 2021).

Laboratory procedures and abbreviations
All measurements provided were taken in millimeters and the terminology used to name both somatic and copulatory structures follows Machado et al. (2018). The dissection procedure applied to study the female genitalia consisted in detaching the epigynal plate from the spider body and immersing it in proteolytic enzyme (pancreatine solution). In order to accelerate the process of digestion of the soft tissues, the solution was placed in a double boiler for a few minutes. Males had their left palps removed and represented in ventral and retrolateral views. Most photographs of the habitus, front and both male and female genitalia were taken on a Multipurpose Zoom Microscope Leica M205A with a digital camera. Scanning electron microscopy images were taken at the Centro de Microscopia e Microanálises (CEMM) of the Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), where the examined material was prepared, receiving a coat of AuPd and placed in a high vacuum chamber to be properly analyzed and photographed with a microscope model Inspect F50 (FEI).

Diagnosis
The species of Kryptochroma gen. nov. resemble some of those of Epicadus [e.g., Epicadus caudatus (Mello-Leitão, 1929) and Epicadus tuberculatus (Petrunkevitch, 1910)] by their cryptic bark-dwelling habitus with predominant brown or reddish-brown body coloration, and those of Epicadinus, especially by their small size (varying from approximately three millimeters of the total body length for males and nine to females) and spiny habitus (body covered by many setae and rugose teguments, and opisthosoma bearing stout conical projections) ( Fig. 2A-D). However, they can be easily recognized and distinguished from Epicadus, Epicadinus and other genera of Stephanopinae by the presence of a pair of ventral macrosetae on their anterior patellae (I and II) (Fig. 1D), sensorial pits (three to fi ve trichobothria surrounded by a small group of duster-shaped setae) on dorsal tibial depressions preceded by a strong plumose macroseta (Fig. 1C), and a pair of circular taints on the posterior slope of the prosoma (Figs 3A, 4A, 7A). Differently from Epicadinus, the species of Kryptochroma gen. nov. have fi ve opisthosomal projections instead of three, and short leaf-shaped setae covering their entire body instead of long needle-shaped ones ( Fig. 1A-B). Females present a fl at epigynal plate, short copulatory ducts and a single pair of oval spermathecae ( Fig. 10C-F); the male palp bears a pear-shaped tegulum with a short and fi xed embolus, and a single tipped, stout and conical RTA ( Fig. 11C-F).

Etymology
The name of the genus is a combination of the Greek words 'kryptos' (κρυπτός) and 'chroma' (χρῶμα), which respectively mean 'hidden' and 'color'. The name is a reference to the general color pattern of these spiders, which is associated to their cryptic behavior. Gender feminine.

Description
PROSOMA. Granular surfaced due to the presence of spherical setae sockets ( Fig. 1A-B); slightly longer than wide, pear-shaped and usually covered with organic particles. ALE almost two times as large as AME, prosoma coloration shows a gradient of brown and dark-yellow shades (predominantly reddish brown in Kryptochroma hilaris Machado & Teixeira gen. et sp. nov.), lighter on the posterior slope, where there is a pair of rounded spots close to the anterior border of the opisthosoma (Figs 3A, 4A, 7A); in some cases the individual has a yellow longitudinal line between the MS and PME (Figs 3A, 5A, 7A, 9A). Anterior eye row strongly recurved, AME close to each other, and posterior eye row procurved ( Fig. 11A-B). Clypeus with a central pair of serrated macrosetae (Fig. 1A). Sternum scutiform, slightly longer than wide in females and as long as wide in males, with brush-shaped setae. Carapace with a conical medianposterior projection pointing backwards (except for K. hilaris gen. et sp. nov. and K. parahybana (Mello-Leitão, 1929) gen. et comb. nov., which have just an obtuse and slight elevation on the top of the thoracic area); opisthosoma short with fi ve stout projections (two lateral pairs and one single and larger terminal projection), anal region and spinneret ring area projected backwards. Mouthparts: chelicerae with fi ve equal-sized teeth; three on the promarginal row and two on the retromarginal. Labium truncated, slightly wider than long. Endites truncated, longer than wide, with scarce promarginal scopula.
LEGS. Anterior femora enlarged and bearing many conical setiferous tubercles, legs I and II stouter and longer than legs III and IV, femora I and II with dorsal and dorsolateral stout macrosetae in conical sockets. Tibia I and II with fi ve pairs of ventral macrosetae, metatarsi I and II with three ventral and one dorso-distal pair (Fig. 1E). Tarsal claws curved, pectinated, unequal in number of teeth (mesial claw with numerous thin teeth and ectal having three stout ones); subungueal tufts scarce, with brush-shaped setae (Fig. 3B).
OPISTHOSOMA. Five short conical projections (two dorsolateral consecutive pairs, and a single caudal one), straight or slightly concave anterior border and rough surfaced, covered by leaf-shaped setae (Fig. 1B). Anal region and spinneret ring projected backwards, elongated.

Description
Female (holotype, UFMG 4734) PROSOMA. Anterior eye row very recurved and posterior slightly procurved; prosoma dark yellow with large lateral black taints, median region and posterior slope yellow, contoured by black lines (Fig. 3A -B). Chelicerae dark yellow with black stains, endites and labium black, sternum black with a median yellow taint.
LEGS. Femora I and II dorsally enlarged and with many setiferous tubercles, femora III and IV bicolor, half black, half yellow.
OPISTHOSOMA. Predominantly dark-yellow, black on the back of the abdominal projections and on the sides, rough surfaced and slightly concave on the anterior border ( Fig. 3A-B).

Male
Unknown.

Distribution
Central Brazil (Minas Gerais) (Fig. 9).  5A). Females can also be distinguished by the presence of two anterolateral and one median depression on the epigynal plate and by the copulatory openings located in a demilune-shaped concavity delimited by the posterior folds of the tegument (Figs 4C, E, 21B).

Etymology
The specifi c name -a Latin adjective that means cheerful -is a reference to the shape of the posterior fold of the epigynal plate, which resembles a smiling face (Figs 4C-F, 21B).
Male (MPEG 13239) PROSOMA. Reddish-brown with a median yellow stripe and dark posterior slope ( Fig. 5A-B); MS absent and eye disposition as in females. Sternum scutiform, as long as wide, light brown with a large yellow taint; labium and endites totally light brown and truncated.
LEGS. Legs I and II predominantly light brown with proximal yellow stains on tibiae and distal on metatarsi; posterior legs light brown, except by the bicolor femora (Fig. 5A).

Diagnosis
The male of K. macrostyla resembles that of K. pentacantha by its robust body and large size when compared to other males of the genus, and by the stout and conical RTA (Figs 6D, F, 20C), but can be easily distinguished by their long, free and fi liform embolus (Fig. 6C, E).

Description
Male (MZSP 15320) PROSOMA. Anterior eye row strongly recurved, ALE slightly larger than AME (Fig. 6B); posterior eye row in a straight line with equal sized eyes. Carapace predominantly dark-brown with a longitudinal yellow line that goes from the middle of PME to the edge of the MS (Fig. 6A); clypeus region and ocular tubercles lighter than the rest of the prosoma (Fig. 6B).
LEGS. Legs I and II reddish-brown, coxae I and II dark-brown with yellowish stains; legs III and IV darkbrown except by the femora which are yellow on its proximal region. OPISTHOSOMA. Rough surfaced, predominantly yellow with dark-brown stains between the abdominal projections and on the sides; lateral projections orange and median dark-brown (Fig. 6A).

Female
Unknown.

Note
The type series of S. salobrensis is constituted by four syntype individuals of two different species. As the male has remarkable genitalic features and clear diagnostic somatic characters ( Fig. 26A-B), we designate it as lectotype (see the section Additional taxonomic acts). The rest of the specimens in the type series are a juvenile and two adult females of K. parahybana, misidentifi ed ( Fig. 26C-D).

Diagnosis
The female

Description
Female (MPEG 30339) PROSOMA. Anterior eye row strongly recurved, posterior eye row slightly procurved, ocular mounds discrete (Fig. 7A-B). Carapace predominantly reddish-brown with black pigmentation increasing on the sides and on the cephalic area; pair of posterior slope scars whitish-yellow and surrounded by a pair of setae emerging from cylindrical sockets (Fig. 7A-B). Chelicerae yellow with dark-brown taints, sternum slightly longer than wide, brown with a median yellow taint; endites and labium truncated, brown.
LEGS. Legs I and II present femora and tibiae predominantly black, with some yellow regions, while posterior legs are lighter, predominantly light-yellow with few light brown spots (Fig. 7A). OPISTHOSOMA. Opisthosoma predominantly brown with yellow pigmentation on the edge of the abdominal projections; spermathecae rounded, slightly narrowed posteriorly (Fig. 7D, F).
LEGS. Predominantly brownish-red with yellowish taints on anterior tarsi (I and II) and on the proximal half of the posterior femora (III and IV).  (2021) OPISTHOSOMA. Predominantly yellow with a whitish line-like macula connecting the fi ve reddish spiniform projections (Fig. 8A).

Diagnosis
The male of K. pentacantha resembles that of K. quadrata sp. nov. by the shape of the tegulum and embolus (Fig. 11C, E); however, it can be distinguished by its stout and conical RTA (Figs 11D,F,19A) and larger body size, since they are the largest males of genus, being the sexual size dimorphism in this species less pronounced. Females can be recognized by the external genitalia bearing a noticeable median septum and a pair of long longitudinal depressions leading to the copulatory openings (Figs 10C, E, 22A). The most common body color pattern for both males and females usually present a diagnostic median white spot on the dorsum of the opisthosoma (Figs 10A, 11A).

Description
Female (MCTP 38671) PROSOMA. Anterior eye row strongly recurved and posterior slightly procurve, carapace predominantly dark-brown with yellowish stains on sides; thoracic region with a pronounced median spire (Fig. 10A-B). Clypeus lighter than the rest of carapace, with a marginal yellowish triangle-shaped mark; chelicerae brown with yellowish stains (Fig. 10B), sternum scutiform, slightly longer than wide, dark-brown with a yellow median macula, endites and labium truncated and totally dark-brown.
LEGS. Predominantly dark-brown with dispersed lighter stains; femora I and II dorsally enlarged, suffused with dorsolateral and ventral conical sockets with a conical macrosetae in each one; tibia I and II with four pairs of ventral macrosetae (Fig. 10A).
OPISTHOSOMA. Dark-brown, rough surfaced, with concave anterior border and a remarkable white taint between the anterior muscular sigilla; the median posterior opisthosomal projection presents acuminate orange tubercles at the tip, with many leaf-shaped setae (Fig. 10B).
LEGS. Metatarsi of all legs with a distal yellow stain and posterior femora noticeably bicolor, half yellow, half dark-brown; other leg characteristics as in females (Fig. 11A).
OPISTHOSOMA. As in female, except by the shorter median posterior opisthosomal projection and the lack of agglomerated orange tubercles.

Diagnosis
The male of K. quadrata sp. nov. resembles that of K. pentacantha by the shape and disposition of embolus (Figs 13C,E,19B), however, it can be distinguished from that and other species of the genus by the rounded tegulum, which also presents a retrolateral reentrance, and by the squared-tipped RTA with remarkable grooved surface (Figs 13D,F,19B). The females have an anterior longitudinal ruckle connected to a shallow and convex fold on the epigynal plate, with no median outgrowth, gutters or septum separating the copulatory openings (Figs 12C, E, 22B).

Etymology
The epithet -a Latin feminine adjective that means squared -is a direct reference to the shape of the RTA tip, which ends abruptly.

Additional material
None.

Description
Female (paratype, MPEG 13297) PROSOMA. Anterior eye row strongly recurved and posterior procurve, ocular mounds discrete, not as elevated as in other species, carapace predominantly yellow, black on the sides, MS well developed (Fig. 12A-B). Chelicerae yellow with two pairs of dark stains, sternum slightly longer than wide, brown with a large yellow stain, endites and labium truncated and totally brown.
LEGS. Leg coloration pattern as in K. gigas gen. et sp. nov.
OPISTHOSOMA. Concave anterior border, predominantly yellow, dark-brown on sides and on the back of the abdominal projections (Fig. 12A). Spermathecae rounded and smooth surfaced (Fig. 12D, F).
LEGS. Anterior legs light brown with some darker taints while legs III and IV are lighter, with extensive whitish areas; anterior femora enlarged, with dorsolateral setiferous tubercles randomly distributed and ventral region dark-brown; tibia I and II with four pairs of ventral macrosetae and anterior metatarsi with three pairs (Fig. 13A).
OPISTHOSOMA. Predominantly pale yellow with small white punctuations and posterior black spots; straight anterior border and fi ve short spiniform projections.

Notes
According to Keyserling (1880), the description of the species in his work was based on the holotype originally proposed by Taczanowski (1872), from Cayenne (French Guiana), which is presumably lost.
We had access to a specimen from the Natural History Museum of London (BMNH 1890.7.1.3479) that is labeled as "type" (Fig. 14G-H); however, it is clearly not the holotype because it was collected after the original description. Since this specimen is strikingly similar to the one represented in the original illustrations (where the author highlighted the diagnostic features of the male palpus: sinuous RTA and the tip-narrowed tegulum) and was found near the original locality (New Granada, currently corresponding to the Colombian territory), we propose it as the neotype for K. quinquetuberculata comb. nov. (Fig. 14G-H).

Diagnosis
The male of K. quinquetuberculata resembles that of K. pentacantha by its stout opisthosomal projections and by the presence of a dorsal white macula on the opisthosoma (Fig. 14A). However, it can be recognized by the tegulum in the shape of a water drop, bearing a straight and tip-narrowed embolus instead of a curved termination observed in its closest correlated species (Figs 14C,E,19C). Moreover, K. quinquetuberculata has a remarkable RTA which is large at the basis, sharpen abruptly at the tip, and sinuous, pointing towards to the dorsum of the cymbium (Figs 14D, F, 19C).
LEGS. Anterior legs (I and II) dark-brown and posterior femora (III and IV) presenting their proximal half yellow.
OPISTHOSOMA. Predominantly brown with a dorsal white macula at its median region and a light transversal line connecting the anterolateral projections (Fig. 14A).

Female
Unknown.

Diagnosis
The male of K. renipalpis is similar to that of K. quinquetuberculata due to their well-developed MS, light clypeus and white macula on dorsum (Fig. 15A-B). However, it can be distinguished from this and other congeneric species by the medially positioned spermatic duct (Figs 15C,E,19D) and extreme curvature of the RTA, which is thinner than in the other species and smooth at the tip (Figs 15D, F, 19D).
LEGS. Anterior legs (I and II) mostly reddish-brown, with yellowish spots on the proximal portion of metatarsi and tarsi; posterior legs (III and IV) with bicolor femora.

Female
Unknown.
LEGS. Anterior legs (I and II) reddish-brown with macrosetae sockets yellowish-white; posterior femora (III and IV) bicolor, yellow on their proximal half and reddish-brown on its distal part. OPISTHOSOMA. Predominantly brown with black punctuations; opisthosomal projections are reddish and bear white maculae on its basis; a dorsal white guanine spot can be also observed on the median region of the dorsum (Fig. 17A).

Note
We propose Stephanopis furcillata as senior synonym of Sidymella multispinulosa (Mello-Leitão, 1944), based on the distinct opisthosoma presenting a long pair of projections with a terminal tubercle at their tips ( Fig. 24C-D). Ulocymus quimiliensis (Mello-Leitão, 1942) comb. nov. Fig. 25 Stephanopis quimiliensis Mello-Leitão, 1942 This group was recovered with signifi cant stability and branch support, presenting two synapomorphies: (1) patellae I and II with a pair of ventral macrosetae; (2) pear-shaped tegulum. Here, we not only describe and provide detailed images of these traits but also formally propose a new generic assignment to this group of species provisionally treated as a clade that should not be recognized as part of Stephanopis (stricto sensu).
Although these studies were based solely on morphological traits, their fi ndings showed to be consistent with what molecular phylogenies have brought to the discussion regarding the relationships in Stephanopinae (Benjamin et al. 2008;Benjamin 2011;Wheeler et al. 2017). While few papers discussed the apparent "simplicity" of the copulatory features in the group, somatic characters (i.e., cryptic body coloration and rugose tegument usually with soil particles attached on it or associated lichen/fungi) have been constantly pointed out (Ramírez 2014;Machado et al. 2017;Machado & Teixeira 2021). These traits and behaviors could be a result of an evolutionary convergence related to hunt and camoufl age adaptations or a plesiomorphic condition in Thomisidae that could have changed multiple times along the phylogeny. Although these evolutionary hypotheses are still open, the importance of a tegument hue and ability of UV refl ection were tested and seem to have an effect on the fi tness of the spiders and their hunting success (Viera et al. 2017). In this sense, it is obvious that to better understand the evolution and relationships in Stephanopinae, performing extensive phylogenies is a must. But to do so, either to sequence the right material or to score a matrix of morphological characters, it is imperative that we start from an accurate taxonomic basis. This is part of an initial effort to clarify the morphological boundaries of some groups of Stephanopinae that were discussed in Machado & Teixeira (2021). More genera are expected to be proposed in the near future since there are fi ve other clades highlighted by these authors that are still in need of proper revisions.