Gilbert, Carter R., Mayden, Richard L. & Powers, Steven L., 2017, Morphological and genetic evolution in eastern populations of the Macrhybopsis aestivalis complex (Cypriniformes: Cyprinidae), with the descriptions of four new species, Zootaxa 4247 (5), pp. 501-555: 508

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Genus Macrhybopsis 

Macrhybopsis Cockerell & Allison 1909: 162  (as subgenus of Hybopsis  ; type species Gobio gelidus Girard 1856  , by original designation).

Extrarius  Jordan 1919: 342 (type species Hybopsis tetranemus Gilbert 1886  , by original designation [also monotypic]). 

Macrhybopsis  was proposed by Cockerell & Allison (1909), based on aspects of scale morphology. Although poorly founded, the genus received recognition because the type species ( gelida  ) is characterized most prominently by a single pair of maxillary barbels, and was accordingly placed by Hubbs & Ortenburger (1929: 25) in the “ Hybopsis  complex” of North American minnows. Jordan (1919) meanwhile had erected a new genus, Extrarius  , for reception of a single species ( tetranema  ) distinguished by the consistent presence of a second pair of maxillary barbels. Hubbs & Ortenburger (1929), in their description of another new and closely related four-barbeled species ( australis  ), determined that these two species bear a close relationship to another widespread two-barbeled species then known as Hybopsis aestivalis  . They accordingly referred all three species to Extrarius  , in which genus they remained until it was submerged by Bailey (1951: 192) into the broad genus Hybopsis  , an artificial assemblage of North American cyprinids for which all included species possess one or two pairs of maxillary barbels. This arrangement remained largely unchanged until Extrarius  was restored to a genus by Mayden (1989), to include the aestivalis  species complex. Mayden (1989) also accorded recognition to Macrhybopsis  , which comprised a clade including M. storeriana  , M. gelida  , and M. meeki  ; and considered it most closely related to the monophyletic genus Extrarius  .

Coburn & Cavender (1992: 349), in their phylogenetic treatment of North American cyprinid genera, included 16 North American genera in a group termed by them the “chub clade,” within which nine (including Macrhybopsis  ) were included in the so-called “exoglossin clade.” Extrarius aestivalis  was formally included within Macrhybopsis ( Coburn & Cavender 1992: 354)  based on six shared synapomorphies, including an enlarged nasal capsule; metapterygoid with an enlarged prong for insertion of the adductor palatine muscle; urohyal with an eroded horizontal lamina and a serrate vertical lamina; an elongated hyoid bar; a short triangular basihyal; and elongated branchiostegal rays. This assignment was accepted by Mayden et al. (1992), and is generally followed today.

As presently conceived Macrhybopsis  comprises 12 species, including M. storeriana (Kirtland)  , M. gelida (Girard)  , M. meeki  ( Jordan & Evermann), and the nine species now recognized in the Macrhybopsis aestivalis  species complex. The following generic diagnosis is copied verbatim from Boschung & Mayden (2004: 206): Body elongate, relatively slender; head flattened ventrally, snout conical to blunt. One or two barbels at corner of each jaw. Lateral scale rows 34 to 50; predorsal scales 14 to 24. Anal rays 7 or 8; pectoral rays 13 to 18. Pharyngeal teeth 1,4-4,1 or 4-4, or combinations thereof. Nuptial tubercles on pectoral fins. Enlarged nasal capsule. Elongated branchiostegal rays. Coloration dusky to silvery, with no chromatic pigments.

In species of the genus, tastebuds and lateral-line neuromasts are exceedingly abundant, and the eyes range from quite small (in M. gelida  and M. meeki  ) to what could be described as “normal” in size. These senses working together account for their ability to occupy both clear and turbid waters ( Branson 1963, 1975; Davis & Miller 1967; Reno 1969).













Gilbert, Carter R., Mayden, Richard L. & Powers, Steven L. 2017


Jordan 1919: 342


Cockerell 1909: 162