Genus Eremocosta Roewer 1934

Eremopus Roewer, 1934: 561 [junior homonym of Eremopus Brady, 1910 (Crustacea: Copepoda)]; Muma 1989: 3 (key), 4.

Eremocosta Roewer 1934: 569 (synonymised by Muma 1951: 41); Harvey 2002a: 450, 451.

Eremacantha Roewer 1934: 571 (synonymised by Muma 1970a: 9).

Eremocosta striata (Putnam 1883). Top photo: male. Bottom photo: female. Both from Santa Cruz County, AZ.
Copyright Warren E. Savary.

Type species:

of Eremopus: Eremopus montezuma Roewer 1934 by original designation.

of Eremocosta: Eremocosta gigas Roewer 1934 by original designation.

of Eremacantha: Eremacantha robusta Roewer 1934 by original designation.


Eremobatine species in which the fixed cheliceral finger of the male bears a distinct apical-ventral cup on its distal half.  The cup does not contain an enlarged seta.


Above: Tip of fixed cheliceral finger of Eremocosta titania (Muma), mesal view, showing apical-ventral cup.

Below: Chelicera of male Eremocosta bajaensis (Muma). Illustrations by Warren E. Savary.

Original description:

Roewer 1934: 569:

"Eremobatinae, deren 2. und 3. Tarsus ventral mit jeweils Dornen und deren 4. Tarsus ventral mit Dornen bewehrt ist (Abb. 320, f, m).

2 Arten, deren eine nur als ♂ deren andere nur als ♀ bekannt ist."

Subsequent accounts:

Roewer, 1934: 561 (as Eremopus):

"Eremobatinae, deren 2. und 3. Tarsus ventral mit jeweils 4.6 Dornen und deren 4. Tarsus ventral mit 2.2.2/0/4.6 Dornen bewehrt ist (Abb. 320, b, k).

8 Arten, von denen die eine nur als ♂ bekannt ist und möglicherweise zu einer der 7 anderen Arten gehört, die nur als ♀ bekannt sind."

Roewer 1934: 571 (as Eremocantha):

"Eremobatinae, deren 2. und 3. Tarsus ventral mit jeweils Dornen und deren 4. Tarsus ventral mit Dornen bewehrt ist (Abb. 320, d, p).

Nur 1 Art"

Muma 1989: 3 (key), 4 (as Eremopus):

(Males Only) Leg 1 with one claw; chelicerae about twice as long as wide; small to large species .......... .. . .......... Eremobatinae ......
Fixed chelicera! finger long, style-like or needle-like; mesoventral groove a crease, slot or cup-like structure ; moderate-sized to large species....
Mesoventral groove a distinct crease, cup, or slot that may or may not extend to base of finger; movable finger dentition normal or increased....
Mesoventral groove short not extending to base of finger; apical striate or plumose setae of male flagellum complex not obviously modified or flattened....
Palpal metatarsus, tibia and femur provided with enlarged spine-like setae , but they are not in ventral rows, especially robust, nor obviously movable ..... Eremopus Roewer

"Predominately large Eremobatinae. Fixed chelicera! finger of males with indistinct to distinct short mesal or mesoventral grooves that do not extend to the base of finger. Dorsal setae of flagellum complex striate but often weakly so, ventral setae plumose but often weakly so; apical setae of complex not obviously modified. Females have opercula alate and widely separated posteriorly."

Key to Species groups of Eremopus Roewer
1. Male cheliceral groove a short distinct ventral cup or slot; males with or without process distad to anterior tooth on movable cheliceral finger ; female opercula alate with concave posterior notches, but without anterior pits ................................................. striatus group
1. Male cheliceral groove a short indistinct mesal crease; males without process distad of anterior tooth on movable finger; female opercula angulate with anterior pits..................
..................................................................................................................montezuma group

Harvey, 2002a: 450, 451:

"Roewer (1934) described numerous new eremobatid genera from the Americas, including Eremorhax Roewer with the type and only species, Datames magna Hancock, 1888. Although the types of this species from Laredo, Texas, are apparently lost (Muma, 1951, 1970), Roewer (1934) had access to five specimens, two males and three females, from Texas that he identified as E. magnus. The genus Eremorhax was later enlarged by Muma (1951, 1970) with the synonymy of Eremopus Roewer, 1934 (type species Eremopus montezuma Roewer, 1934 by original designation), Eremocosta Roewer, 1934 (type species Eremocosta gigas Roewer, 1934 by original designation), and Eremacantha Roewer, 1934 (type species Eremacantha robusta Roewer, 1934 by original designation). Eremorhax was made the type genus of Eremorhaxinae Roewer, 1934, although this subfamily was later synonymized under Eremobatinae Kraepelin by Muma (1951). Brookhart and Muma (1987) discussed the identity of the species described as E. magnus (Hancock, 1888) by Roewer (1934), concluding that it was not conspecific with the species described and illustrated by Hancock (1888) and Muma (1951). Rather, they considered it a representative of the genus Eremobates Banks, but did not speculate any further on its identity. They then placed Eremorhax Roewer as a junior synonym of Eremobates Banks, 1900, and described a new genus, Arenotherus Brookhart and Muma, 1987 for Datames magna Hancock, 1888 and several other species. Although they consistently referred to the new genus as accommodating those species previously placed in the Eremorhax magnus group of Muma (1951), they did not specify a type species, in contravention of Article 13(b) of the International Code of Zoological Nomenclature, 3rd edition. The remaining species previously placed in Eremorhax were transferred to Eremopus by Muma (1989). The lack of a type designation for Arenotherus was clearly a lapsus by Brookhart and Muma (1987), and I hereby designate Datames magna Hancock, 1888 as type species (new designation), as they so obviously intended. In addition, when Brookhart and Muma (1987) discovered that Roewer (1934) had misidentified the type species when describing the genus Eremorhax, they were required by Article 70(b) of the International Code of Zoological Nomenclature then in effect (3rd edition) to request the Commission to resolve the case. Article 70.3 of the 4th edition of the Code (International Commission on Zoological Nomenclature, 1999) gives authors the power to designate as type species that species which best serves stability and universality - either the nominal species previously cited as type species, regardless of misidentification, or the species actually involved which was wrongly named in the type fixation - without application to the Commission. Designation of the nominal species previously cited as the type species would render Arenotherus Brookhart and Muma (1987) as a junior synonym of Eremorhax. Designation of the species actually involved would render the misidentified specimens available to Roewer (1934) as representing the type species. The identity of these specimens is unclear and my attempts to locate the material have proved fruitless - Roewer (1934) did not state from which institution they were borrowed, and they were not part of Roewer's collection now lodged in Naturmuseum Senckenburg, Frankfurt (Zilch, 1946). However, Brookhart and Muma (1987) did state (p. 1) that Roewer's description fitted a species of Eremobates but without access to these specimens it will be difficult to determine their identity. In the interests of stability, I here propose that the first option is the best solution and I here designate Datames magna Hancock, 1888 as the type species of Eremorhax, regardless of the misidentification made by Roewer (1934). This automatically places Arenotherus as a junior objective synonym of Eremorhax Roewer, 1934 (syn. nov.). In addition, Eremopus Roewer, 1934 is here found to be a junior homonym of the copepod genus Eremopus Brady, 1910. However, a replacement name is not needed for Roewer's name because Eremopus currently has two junior synonyms, Eremocosta Roewer, 1934 and Eremacantha Roewer, 1934 (Muma, 1951, 1970), of which Eremocosta is here selected as the valid name. The type species of Eremocosta, E. gigas Roewer, is well defined and the holotype is an adult male lodged in Naturmuseum Senckenburg, Frankfurt, Germany (Muma, 1970), whereas the holotype of the type species of the other synonym, Eremacantha, E. robusta Roewer, is an immature specimen (Muma, 1970) whose specific identity may never be known with certainty."


The genus Eremocosta contains thirteen species from the southwestern United States and Mexico.

Included species

  • Eremocosta acuitlapanensis (Vasquez & Gavin 2000)
  • Eremocosta bajaensis (Muma 1986)
  • Eremocosta calexicensis (Muma 1951)
  • Eremocosta formidabilis (Simon 1879a)
  • Eremocosta fusca (Muma 1986)
  • Eremocosta gigas Roewer 1934
  • Eremocosta gigasellus (Muma 1970a)
  • Eremocosta montezuma (Roewer 1934)
  • Eremocosta nigrimana (Pocock 1895a)
  • Eremocosta robusta (Roewer 1934)
  • Eremocosta spinipalpis (Kraepelin 1899a)
  • Eremocosta striata (Putnam 1883)
  • Eremocosta titania (Muma 1951)