Eremobates scaber species group

Diagnosis:

Muma (1951) established this group to accommodate species of Eremobates that he characterized as having.a wide basal notch in the fixed cheliceral finger of males that is visible from dorsal view. He described the notch as occupying one-third or more of the length of the finger. The mesoventral groove of the fixed finger, he stated, is dilated basally, and the first postspiracular abdominal sternite is provided with two to six ctenidia. Females, he reported, have roughly triangular genital opercula that are well separated along most of their mesal margins. Although he reported that both rows of fondal teeth are graded I, III, II, IV in size, he later (Muma 1986, 1987) suggested that fondal tooth formulae are not valid for genus or group separation, as they are subject to wear, especially by females.


Literature accounts:

Muma 1951: 51(key), 52

MALES

1. Fixed finger with a wide basal notch in dorsal view........................................scaber group


Males of this group have a broad basal notch of the fixed finger in dorsal view that occupies one-third or more of the length of the finger. The mesoventral groove of the fixed finger is dilated basally. They are provided with two to six ctenidia on first postspiracular abdominal sternite. Females have roughly triangular genital opercula that are well separated along most of their mesal margins. Both rows of fondal teeth graded I, III, II, IV in size.

TYPICAL SPECIES: Eremobates scaber (Kraepelin).


Muma 1970a: 10 [key to species groups (males)], 11 [Table 5]:

"1. Fixed cheliceral finger in dorsal view with wide basal notch......scaber group"


            Table 5.         Some male diagnostic characters of the Eremobates scaber species group
       Species
No. and form
of ctenidia
No. of
papillae
Other
       E. ascopulatus Muma 2 short, flattened None
Deep fondal notch and
pale color
       E. ctenidiellus Muma 2 hairlike 30+
Deep fondal notch,
slender fixed finger, and
indistinct markings
       E. gladiolus Muma 2 scimitarlike 80
Deep fondal notch and
pale leg and palpi
       E. septentrionis new name 2 short, flattened 40-160
Deep fondal notch and
legs and palpi distinctly
marked with dusky purple
       E. mormonus (Roewer) 4 elongate, flattened 40-160
Shallow fondal notch
and pale coloration
       E. similis Muma 4 short, needlelike None
Shallow fondal notch and
legs and palpi distinctly
marked with dusky purple
       E. zinni Muma 4 short, flattened None
Deep fondal notch and
dark palpal tarsus and
metatarsus


Muma 1976: 18:

""

Muma 1987: 10:

""

Muma 1989: (key):

Mesal groove of fixed cheliceral finger mesoventral in position Mesal groove narrow apically, occupying less than half of finger width Mesal groove distinctly dilated basally.................................................................................................................scaber group

Opercula not or only moderately separated posteriorly; broadly triangular in shape and without distinct pits midway along ectal margins except for E. mimbrenus new species Mesal margins of opercula lobate, bilobate or sinuate at or just anterior to posteriomesal notch..................................................................................................................scaber group


Brookhart and Cushing 2005: 284-286

"Muma (1951) redescribed the genus Eremobates Banks 1900 to include those solifugid species characterized by males with a basally dilated mesoventral groove running the length of the mesodorsal or mesoventral surface of the fixed finger. The male flagellum complex consists of dorsal striate setae, ventral striate setae, and a flattened apical plumose seta covering much of the mesoventral groove. The female genital opercula varied depending upon the species-group. Additionally the Eremobates scaber species group was erected by Muma (1951) to include those Eremobates whose males were characterized by a broad basal notch occupying one-third or more of the length of the fixed finger in dorsal view (Fig. 1). In the scaber group the mesoventral groove is deep and narrow. The female genital opercula are roughly triangular with species distinguished by differences in the medial margins."

"Muma (1951) listed six species in the scaber group including the typical or defining species E. scaber (Kraepelin 1899) although he had not seen the female type specimen. After examining type specimens in both the U.S. and Europe as well as other specimens from various collections and collectors Muma (1970) recalled Kraepelin’s 1899 description of Datames scaber based on the female type from ‘‘Washington Territory’’ as the correct characterization of Eremobates scaber. He used his 1951 description, erroneously attributed to E. scaber, to establish E. septentrionis Muma 1970, used his 1951 description of E. geniculatus to erect E. mormonus (Roewer 1934) and defined E. geniculatus (C.L. Koch 1842) (Simon 1879, misidentified) using Simon’s 1879 description of a single female from Mexico (Muma 1970). In 1989 Muma described six new species. This resulted in 15 species in the scaber group with E. scaber, E. actenidia Muma 1988, E. clarus Muma 1989, E. consors Muma 1989, E. ascopulatus Muma 1951 and E. hodai Muma 1989 described from only one sex although Muma included the male of E. scaber in the key. Eremobates clarus, E. actenidia and E. consors were each described from a single specimen and E. ascopulatus from two males. Eremobates similis (Muma 1951) was noted as being described in both sexes (Muma 1989), but the female description has not been found."

"In describing E. scaber, Muma (1951) used specimens from an area that extended from the northwestern United States to Las Vegas, Nevada but noted that it might include other species of this group. In addition, other species of this group seemed to have sympatric ranges (Muma 1951, 1962, 1989). In each of his publications Muma (1951, 1962, 1989) cited several problems with the distinction between species and problems of sympatric associations. Muma (pers. comm.) indicated that this group needed to be more thoroughly studied."

"For the most part, this group is an inhabitant of pinyon pine-juniper or desert shrub communities. Muma (1963) identified E. zinni (Muma 1951), E. similis, E. ctenidiellus and E. mormonus as inhabitants of the Mercury, Nevada Nuclear Test Site, a Mojave Desert region, although some of the specimens were misidentified. Allred & Muma (1971) listed E. septentrionis and E. ctenidiellus as inhabitants of the Snake River Plain which is part of the Columbian Plateau. Brookhart (1972) found E. mormonus, later changed to E. similis, in the San Luis Valley of Colorado and E. ctenidiellus in the mesa regions of western Colorado. The Sevilleta Long Term Ecological Reserve project at the northern tip of the Chihuahuan Desert surveyed six distinct desert grassland/high desert areas and found E. similis in only the pinyon-juniper association (Brookhart & Brantely 2000). At the Hanford Nuclear Site, Rich Zack’s E. scaber material (WSU) was collected in Great Basin Desert shrub habitat, and various Canadian specimens were collected in the sagebrush of the Okanogon Valley. Eremobates scaber group species have been collected at 2394 m in Wyoming, 2303 m in the San Luis Valley of Colorado, and on Mt. Palomar, California."

"Muma (1951, 1962, 1970, 1989) used length vs. width of the fondal notch, number and shape of ctenidia, and number of palpal papillae, as well as coloration of appendages to separate each species. The number of ctenidia ranged from 0–6. The palpal scopula varied from none to over 120 papillae. Females were identified by the structure of the genital operculum and the coloration of appendages. Coloration of eye tubercle and malleoli were noted but were consistently the same for all species with eye tubercles dark and malleoli white. Abdominal coloration varied from a pale yellow to a grey background dorsally and ventrally with lighter pleural membranes between species and also between specimens of the same species. Many specimens had tergites with a rectangular, brownish, violet pigmentation which gave the appearance of a broad stripe to many specimens. Muma (1951) calls this a sclerite although it is not particularly thick or hardened. It was not found to be diagnostic in this study."

Male chelicerae have no teeth on the fixed finger and some variation in the shape of the fixed finger in ectal view. The movable finger follows the general pattern of a large primary tooth, two intermediate teeth, the posterior being larger and an anterior tooth. The mesal tooth varies from tiny to absent. Female chelicerae have a fixed finger with teeth ordered successively posterior to anterior, intermediate tooth, large primary tooth, two intermediate teeth, medial tooth, a single intermediate tooth and a smaller anterior tooth. The female movable finger has a large primary tooth, a variable sized anterior tooth and two intermediate teeth, the posterior of which is larger. The mesal tooth varies from absent to medium size. Fondal teeth in both male and female grade out I, III, II, IV in size, although in some species the fondal tooth III is equal in size to fondal tooth I. Due to wear, the intermediate teeth on both male and female movable fingers are sometimes hard to diagnose."


Cushing and Brookhart 2016:

"Cushing et al. (2015) produced a backbone molecular phylogeny of the Eremobatidae that supported the monophyly of several genera and species groups within the family. The Eremobates scaber species group was well supported but was made paraphyletic with respect to Hemerotrecha sevilleta Brookhart & Cushing 2002 (Cushing et al. 2015). However, the H. sevilleta specimen used in that analysis was missing data and none of the available specimens of this species of Hemerotrecha was well preserved. Thus, we suspect that rather than indicating that the E. scaber group is artificial, the placement of H. sevilleta in this clade indicates that a re-assessment of that species, once additional better preserved specimens are collected, is necessary. In this paper, we build upon our understanding of this species group."

"Brookhart & Cushing (2004) produced an analysis of the E. scaber species group including the description of three new species, the synonymization of two species, and identification of both sexes for 12 of the 14 species then known. We also produced a phylogeny of this species group based on morphological characters, the first for any solifuge taxon. In the Cushing et al. (2015) analysis, the E. scaber species group clade (which included H. sevilleta) was strongly supported in both the Bayesian and Maximum Likelihood analyses."

"The E. scaber species group currently includes: E. actenidia Muma 1989, E. ascopulatus Muma 1951, E. clarus Muma 1989, E. corpink Brookhart & Cushing 2004, E. ctenidiellus Muma 1951, E. hodai Muma 1989, E. icenoglei Brookhart & Cushing 2004, E. legalis Harvey 2002, E. mormonus (Roewer 1934), E. paleta Brookhart & Cushing 2005, E. scaber (Kraepelin 1899), E. similis Muma 1951, E. socal Brookhart & Cushing 2004, and E. zinni Muma 1951. The group was erected by Muma (1951) to encompass those species of Eremobates whose males were characterized by a broad basal notch occupying one-third or more of the length of the fixed finger in dorsal view (Fig. 1A, arrow). In the E. scaber species group the mesoventral groove (MVG) is deep and narrow (Fig. 1B). The female genital operculum is roughly triangular (Fig. 1C) with species distinguished by differences in the medial margins. In their molecular phylogenetic analysis of Eremobatidae, Cushing et al. (2015) found that the E. scaber species group was phylogenetically and geographically cohesive. This species group diversified during the Pliocene (Cushing et al. 2015). Increasing aridification in the middle Miocene and beyond is thought to have generated a large, contiguous expanse of proto-desert across what is now the Mojave, Sonoran, and Chihuahuan deserts (Morafka 1977) and likely led to the diversification of many arid-adapted taxa, including many species of solifuges (Cushing et al. 2015)."

The majority of species in this group are found in piñon pine-juniper or desert shrub communities of the arid USA. Eremobates paleta and E. legalis both have type localities in Mexico (Brookhart & Cushing 2004, 2005; Brookhart & Brookhart 2006); all the rest were first described from the USA. However, Vásquez-Rojas (1981) recorded E. zinni from Mexico and Muma (1951, 1987) listed E. ctenidiellus and E. geniculatus from Mexico. The latter record was found to have resulted from a misidentification of E. mormonus by Muma (1951) (Brookhart & Cushing 2004). Seven genera and 64 species of solifuges have been identified from Mexico (Brookhart & Brookhart 2006; Ballesteros & Francke 2008), and it is likely that more species of the E. scaber species group range into the Chihuahuan Desert region of Mexico."

Muma (1951, 1962, 1970, 1987, 1989) used length vs. width of the fondal notch, number and shape of ctenidia,and number of palpal papillae, as well as coloration of appendages to separate each species within the E. scaber species group. The number of ctenidia range from none to six. The palpal scopula varies from none to over 120 papillae. Females are identified by the structure of the genital operculum and coloration of appendages. Coloration of the eye tubercle and malleoli are consistently the same for all species with eye tubercles dark and malleoli white. Abdominal coloration varies from a pale yellow to a grey background dorsally and ventrally with lighter pleural membranes and is a poor character to use for species identification. Many specimens have tergites with a rectangular, violet-brown pigmentation which gives the appearance of a broad stripe to many specimens. Muma (1951) calls this a sclerite although it is not particularly thick or hardened. It was not found to be diagnostic in this study.

Throughout this paper, we follow the cheliceral terminology suggested by Bird et al. (2015) except for fondal teeth. We maintain Muma’s (1951) use of Roman numerals designating the location and relative size of fondal teeth since this designation is less cumbersome and more adequately expresses relative size than the terminology proposed by Bird et al. (2015).

Typical male chelicerae in the Eremobates scaber species group is characterized by the broad basal notch of the cheliceral fixed finger in dorsal view (Fig. 1A, arrow). There are no median series teeth (per Bird et al. 2015) on the fixed finger and some variation in the shape of the fixed finger in retrolateral view. The movable finger follows the general pattern of a large proximal tooth (MP), two submedial teeth (MSM) (the proximal being larger) and a medial tooth (MM) (Fig. 2). The medial tooth is distinctively flattened and frequently has a cleft beneath the anterior face. The movable finger prolateral tooth (MPL, not visible in Fig. 2) varies from tiny to absent. The fondal notch is “U” shaped but some variation is evident. Zero to three retrofondal teeth are present. Female chelicerae have a fixed finger with teeth in the following order (proximal to distal): 0–3 retrofondal teeth (RF), a large proximal tooth (FP), two submedial teeth (FSM), a medial tooth (FM), a single subdistal tooth (FSD), and smaller distal tooth (FD) (see plate 21, Bird et al. 2015 and Figs. 5 I–L). The female movable finger has a large proximal tooth (MP); two submedial teeth (MSM), the posterior of which is larger; and a large medial tooth (MM). The prolateral tooth (MPL) varies from absent to medium sized (Fig. 5 I–L). Fondal teeth in both males and females grade out (apex to base) I, III, II, IV in size although in some species the fondal tooth III is equal in size to fondal tooth I (Fig. 6). Due to wear, the medial teeth on both male and female movable fingers are sometimes hard to diagnose".

"While examining the solifuge collection from the Instituto de Biología Universidad Nacional Autonoma de Mexico (IBUNAM), Mexico City, courtesy of Oscar Francke, we discovered nine new members of the E. scaber species group, most of which are represented by singletons. However, because this species group is diagnosable based upon distinct morphological synapomorphies (e.g., the broad basal notch of the male fixed finger), we felt confident in placing these single specimens into the E. scaber species group. Additionally we have discovered one new species from California, USA that is deposited in the collection at the Denver Museum of Nature & Science (DMNS) that was collected by staff with the U.S. Geological Survey (USGS)."


Notes:



Included species



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