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Teratology is the science that deals with the causes and patterns of deformities, abnormalities and defects in the physical development of animals. Teratological occurrences can be due to genetic o...

Stasimopidae is monotypic and represented by the genus Stasimopus Simon, 1892. It is a southern African endemic represented by 45 species and two subspecies. The genus has not yet been revised and based on the morphological diversity contained within the genus, it is possible that it could be split in to multiple genera at some point in the future (Opatova et al. 2020). According to Hewitt (1915) the characters employed in distinguishing the various species are all somewhat variable, even in specimens taken from the same locality and with the advent of more material from different parts of the country it becomes increasingly difficult to draw a hard and fast line between the various species. Of the 47 Stasimopus taxa known from South Africa 46 were South African endemics and 18 Eastern Cape Endemics. Only Stasimopus fordi Hewitt, 1927 was also known from Lesotho and Botswana. Only 23 species were known from both sexes and 18 only from the female. Stasimopus specimens are difficult to collect and are not well sampled. Twenty-two species are known only from the type locality. Presently only two species are listed as Least Concern due to their wider distribution range and 40 species are data deficient. Only five species are listed of special concern, ranging from Critical Rare (S. mandelai Hendrixson & Bond, 2004), Near Threatened (S. robertsi Hewitt, 1910), Endangered (S. filmeri Engelbrecht & Prendini, 2012 and S. griswoldi Engelbrecht & Prendini, 2012) and Vulnerable (S. hewitti Engelbrecht & Prendini, 2012).

Funds for pitfall trapping equipment were provided by the Oppenheimer family and E. Oppenheimer & Son, with the assistance of Duncan MacFadyen. Funds for other costs associated with fieldwork were provided by the Gauteng Department of Agriculture and Rural Development, Government of the Republic of South Africa. Fieldwork was funded in part by National Science Foundation grants EAR 0228699 and DEB 0228699 to the second author.

Taxonomic classifications simultaneously represent hypotheses of taxon identity and relationships to taxonomists, and real, unchanging entities to users of taxonomic information. Taxonomic changes, while representing scientific progress, can be a source of frustration for users. A method for assessing confidence in the taxonomy of a group of organisms would assist users of the taxonomy. A method is presented for determining the degree of development of a taxonomy, a concept termed ‘taxonomic resolution’. The method was applied to six groups of southern African mygalomorph trapdoor spiders, namely Stasimopus Simon 1892 (Ctenizidae Thorell 1877), Ancylotrypa Simon 1889 (Cyrtaucheniidae Simon 1889), four genera of Idiopidae Simon 1889 assessed as a single group, Galeosoma Purcell 1903, the families Migidae Simon 1889 and Microstigmatidae Roewer 1942, and the burrowing scorpion genus Opistophthalmus C. L. Koch 1837 (Scorpionidae Latreille 1802). The method was based on the assumption that species delimitation in a group of organisms, the taxonomy of which is based on morphological characters, depends on whether the sample of material examined is adequate for assessing variation in those characters. Five assessment criteria were identified and scored for a group of species using the taxonomic literature. Estimates of the number of species remaining to be discovered and described in each group were also included in the assessment. The results obtained for the trapdoor spiders ranged from 15 to 29%, indicating a potentially significant degree of uncertainty in the taxonomy. Results for Migidae and Microstigmatidae were 51 and 78% respectively, whereas the result for Opistophthalmus was 93%. The applied value of a measure of taxonomic resolution, the limitations of the method, and a strategy for developing a more generally applicable method are discussed.

Stasimopus mandelai, new species (Figs. 1-19; Table 1) Type data.- Republic of South Africa: Eastern Cape Province: Great Fish River Nature Reserve Site #2, (elev. 420 m), 4 June 2002 (J. E. Bond & M. C. Hedin), male holotype (MY 557) (CAS); same locality data, male paratype (MY 559) (PPRI); Great Fish River Nature Reserve Site #3, (S 33°07.653', E 26°40.372', elev. 325 m), 4 June 2002 (J. E. Bond & M. C. Hedin), 1 male paratype (MY 560) (CAS); same locality data, 2 female paratypes (MY 563, 564) (CAS), MY 563 with 35 second instar spiderlings; same locality data, 1 female paratype (MY 568) (CAS); same locality data, 1 female paratype (MY 569) (PPRI). Diagnosis.-Males can be identified primarily on the basis of leg spination patterns and coloration. The new species differs from Stasimopus steynsburgensis Hewitt by lacking distinct spines on the leg tarsi, possessing fewer spines on metatarsus I, and having a slightly more slender pedipalpal femur. Stasimopus mandelai sp. nov. does not possess distinctly red tarsi and metatarsi, nor does it have yellow-coloured parts on the book lungs and epigastric region (these are significant color differences) as do males of S. schoenlandi. In addition, the legs of the new species are far less spinose than that of the latter species. Females are moderately difficult to distinguish from other species. However, size, dorsal opisthosomal markings, and leg spinule patterns may provide some characters for identification.Stasimopus mandelai sp. nov. possesses distinct markings on the opisthosoma and is considerably smaller than S. schoenlandi and S. spinosus Hewitt. It also differs from S. spinosus by having a less extensive patch of spinules on metatarsus I. Description.-Males (Figs. 2-10). General: Moderate to large spiders (CL = 4.90- 6.10). Carapace reddish-brown to nearly black. Sternum and coxae yellowish-orange. Opisthosoma of preserved specimens pale, light yellow to gray; faint dusky patch widening toward posterior, sometimes with chevron markings or posterior infuscated blotch. Chelicerae dark, nearly black. Proximal segments of pedipalps and legs I-III dark, nearly black; distal segments progressively lighter (brownish-orange to orange). Proximal segments of leg IV obviously lighter colored than corresponding segments of other legs. Prosoma: Carapace slightly longer than wide (CL / CW = 1.09-1.22), appearing somewhat circular when viewed from dorsal aspect. Carapace with sparsely scattered setae along posterior and lateral margins; caput region moderately setose, particularly near ocular area. Carapacial surface roughened, characterized by numerous indistinct ridges or striae. Caput region slightly elevated (Fig. 2), with three vestigial longitudinal carinae where setae originate. Foveal groove moderately deep, strongly procurved. Ocular area (i.e., trapezoidal region encompassing AER and PER) slightly over twice as wider than long; ocular tubercle weak. AER essentially straight; PER somewhat recurved. PME situated behind ALE; distance between AME distinctly greater than distance between PME. Sternum widest between coxae II and III; posterior margin obtusely shaped. Posterior sternal sigilla positioned meso-laterally, about four times longer than wide. Sternal surface slightly to moderately setose; labium moderately setose. Labium and maxillae lacking cuspules. Opisthosoma: All surfaces moderately to densely setose. Epiandrous fusillae distinct from surrounding setae (e.g., stouter stature, wider base). Chelicerae: Rastellum distinct, consisting of several spinules. Surfaces somewhat roughened. Pedipalps: Segments elongated, lacking spines; tibia over five times longer than deep, slightly convex ventrally when viewed from lateral aspect (Fig. 5). Embolus moderately long, slender; tip slightly curved (Figs. 5, 6, 8). Surfaces sparsely to densely setose. Legs: Femur I generally shorter than tibia I. Tarsus IV distinctly longer than femur IV. Ventral surface of coxae moderately setose. Other leg segments (except retrolateral aspect of femur IV) moderately to densely setose; femora usually less hirsute than other segments. Scopula well-developed on tarsus I, less so on other tarsi, but still present; scopula absent from metatarsi. Spination of tibia and metatarsus I are illustrated in Figs. 3, 4, 7, 9, 10. Distinct patch of spinules on patella IV. Preening comb on ventrodistal aspect of metatarsi moderately obscured by other setae and spines. Tibial mating claspers consisting of 2-3 elongated spines with (usually) recurved tips. Females (Figs. 1, 11-15). General: Moderate to large spiders (CW = 6.56-7.94). Carapace somewhat lighter than in male; caput region brown, surrounding surfaces usually lighter. Opisthosoma of preserved specimens pale gray, with variable patterns; sometimes with dusky anterior median blotches (e.g., MY 563); usually with distinct posterior chevron markings or blotch. Legs brownish-orange. Prosoma: Carapace not noticeably circular (CL / CW = 1.14-1.19); anterior margin distinctly wider than posterior. Carapacial surface glabrous, shiny. Caput region much more strongly elevated than in male (Fig. 1), carinae absent. Foveal groove deep, strongly procurved. Ocular area distinctly over two times wider than long; ocular tubercle weak. AER and PER straight. PLE and PME subequal in size. PME oval or nearly circular. Distance between ALE and PLE about one or two times the diameter of one PLE. Diameter of one ALE greater than distance between ALE and AME. Sternum widest between coxae II and III; posterior margin obtusely shaped. Sternal and labial surfaces moderately setose. Sigilla relatively shallow. Labium about as long as wide, with 5-8 cuspules. Maxillae with 7-14 cuspules concentrated near proximal prolateral margin. Opisthosoma: All surfaces moderately to densely setose. Spermathecae (Fig. 11) consisting of two simple, lightly-sclerotized and unbranched bulbs. Chelicerae: Rastellum strong. Surfaces more or less glabrous. Prolateral margin of cheliceral fang furrow with 4-5 teeth (anterior-most sometimes smaller or absent). Pedipalps: Tarsus with proximal patch of spinules extending over less than one-third of segment or consisting of only a small basal cluster. Tibia without stout dorsal spines; often with a few stiffened setae distally. Tibia and tarsus with numerous digging spines on ventral side of segment. Legs: Tibia, metatarsus and tarsus I and II with numerous digging spines. Metatarsus I with dorsobasal band of spinules reaching approximately one-fourth to slightly over one-half of segment (Figs. 12-15); moderately well developed. Femur III with or without single dorsal spine near apex. Patella III with or without distinct spines near apex, not especially slender; with patch of black spinules (unlike red spinules on patella IV). Metatarsus III with apical spines, but not along extreme distal margin; other spines well developed. Metatarsus IV without single, enlarged stout spine within apical tuft; without ventromedian band of spines, but moderately spinose prolaterally; preening comb distinct on ventral surface. Dorsobasal surface of patella IV with distinct patch of red spinules. Most segments weakly to moderately setose; some areas devoid of setae. Selected measurements and meristics are provided in Table 1. Taxonomic Remarks.-At present, females can be differentiated from S. schoenlandi and S. spinosus primarily upon the basis of opisthosomal markings and size. The opisthosoma of numerous Stasimopus species is reported as being pale with a darkened blotch posteriorly. The new species has a distinct infuscated blotch (often with anteriorly projecting swathes of pigment which originate from the lateral aspect of the blotch) or a chevronlike pattern on the posterior portion of the opisthosoma. Such a character was not reported for S. schoenlandi and was not observed in the holotype female of S. spinosus (although it is possible that the opisthosomal markings, if present, have faded over time), but it is fairly conspicuous and was well known to Hewitt, who worked extensively with these two species (Hewitt 1913, 1914, 1915a, 1917, 1927). He described the opisthosoma of an additional species, S. maraisi Hewitt, as "pale above with some dark blotches which in the hinder half are symmetrically arranged, forming a kind of tree pattern" (Hewitt 1914); this is somewhat consistent with the opisthosomal pattern of the new species. However, S. maraisi is known from the Northern and Western Cape Provinces only. In addition, females of the new species appear to be considerably smaller than those of S. schoenlandi and S. spinosus. Hewitt (1913) reported that a female specimen of S. schoenlandi had a carapace length of 13.75 mm, nearly twice the average length of the new species (Table 1). The total length of this species has commonly been reported to be well over 30 mm, whereas the largest female (MY 569) of the new species is only about 24 mm. We are well aware that size can be an unreliable diagnostic character for females because of age (i.e., due to post-maturation molts) and nutritional history, but this character has been used successfully in other mygalomorph spiders (e.g., Hendrixson & Bond in press) and the size difference observed herein appears to be significant. Distribution.-Presently known only from the type locality. Etymology.-The specific epithet is a patronym honoring Nelson Mandela, the former president of South Africa and one of the great moral leaders of our time. Natural history Stasimopus mandelai sp. nov. was collected in open Karoo habitat. This habitat type, particularly that of the Great Fish River Nature Reserve, is considered to be an extremely harsh environment with high diurnal and annual temperature ranges, and with exceptionally low amounts of precipitation (Cowling 1983). Dominant vegetation types at the collecting locality (site #3) included Maytenus capitata,Lycium campanulatum, Grewia robusta,Ehretia rigida,Pentzia incana,Protasparagus suaveolens,Rhus refracta, and Acacia karroo. A number of other mygalomorph species were collected very close to S. mandelai sp. nov. and are considered to be syntopic. These included Stasimopus schoenlandi,Moggridea crudeni Hewitt (Migidae), Ancylotrypa sp. (Cyrtaucheniidae), Allothele australis (Purcell) (Dipluridae), and Ctenolophus sp. (Idiopidae). There are relatively few detailed accounts of Stasimopus natural history, although Dippenaar-Schoeman (2002) did provide a brief, general overview of trapdoor and burrow construction thought to be typical for members of this genus. Figures 16-19 show a typical Stasimopus mandelai sp. nov. (specimen MY 563) burrow excavated from the upper ledge (20-25° slope) of a steep bank (the trapdoor hinge facing down the slope), collected at Great Fish River site #3. The trapdoor was a very thick, cork-type door, measuring over 8.70 mm in thickness and firmly attached to the burrow lip by a relatively thin silken hinge approximately 16.00 mm wide. The door is ovoid in shape (length = 15.97 mm, width = 13.30 mm) and is composed primarily of silk and soil with a very light covering of moss. The burrow was approximately 14.50 mm in diameter and 175.00 mm deep, extending into the ravine bank at almost a 90° angle to the entrance. The inside of the trapdoor (Fig. 18) had small pits likely made by the spider gripping the lid with its tarsal claws and chelicerae (Dippenaar-Schoeman 2002, Bond & Coyle 1995). All males examined were collected in their burrows after they had reached maturity. Based on this information, males likely perform their final molt during the late autumn/ early winter months and emerge shortly thereafter. One female (MY 563) contained 35 second instar spiderlings within her burrow. It is unknown whether females mate while brooding young from previous seasons, or how long spiderlings remain within the maternal burrow.