Red monkeys, red ink: Resolving pyrronotus vs. pyrrhonotus as a species name for the Patas Monkey Erythrocebus

Yvonne de Jong April 6, 2026 Blogs

Yvonne A. de Jong and Thomas M. Butynski
Eastern Africa Primate Diversity and Conservation Program, wildsolutions.nl

Patas monkeys Erythrocebus Trouessart, 1897 are semi-terrestrial primates endemic to tropical Africa. They are characterized by their large size (up to 18 kg), slender bodies, and red, white, and black pelage (Figure 1). The taxonomy of the species and subspecies within Erythrocebus is complex and far from resolved. We are currently undertaking a review of the taxonomic arrangement within Erythrocebus.

Figure 1. Eastern patas monkeys Erythrocebus patas pyrrhonotus, Borana Conservancy, Laikipia Plateau, central Kenya. Photograph by Y. de Jong & T. Butynski.

During our review of the literature, we found considerable variation in the spelling of one of the specific names (= epithets) for the eastern patas monkey – ‘Erythrocebus pyrronotus’ versus ‘Erythrocebus pyrrhonotus’. Also, this specific name’s authority and the year of publication vary considerably in the literature. Table 1 presents some examples of this variation.

Table 1. Variation in the spelling of ‘pyrronotus’ vs ‘pyrrhonotus’ as the specific name for the eastern patas monkey.

The confusion over ‘pyrronotus’ vs ‘pyrrhonotus’ goes back to the protologue of Cercopithecus pyrronotus (Hemprich & Ehrenberg, 1829). These authors first published the description and specific name of this monkey  in Verhandlungen der Gesellschaft Naturforschender Freunde zu Berlin (1829, p. 407; Figure 2). The specific name ‘pyrronotus’ is presented twice in this work.

Figure 2. Original description of Cercopithecus pyrronotus. Pages 406–407 in Verhandlungen der Gesellschaft Naturforschender Freunde zu Berlin (1829) (6): 406–408.

Hemprich & Ehrenberg (1833) subsequently published supporting text and an illustration with caption (Plate 10) in Symbolae Physicae (‘1832’ appears in this publication but it was not printed and made available until 1833). Here they introduced the name ‘pyrrhonotus’ (Figure 3) while the caption to the drawing applied the name ‘pyrronotus’ (Figure 4).

Figure 3. Title of the Cercopithecus pyrrhonotus protologue by Hemprich & Ehrenberg (1933) in Symbolae Physicae.

Figure 4. Cercopithecus pyrronotus in Plate 10 in Hemprich & Ehrenberg (1833). Note the spelling ‘pyrronotus’ in the caption.

Hemprich & Ehrenberg (1833) used ‘pyrrhonotus’ in the title, listed ‘pyrrhonotus’ as a synonym (i.e., Cercopithecus pyrrhonotus Ehrenberg Verhandl. d. Gesellschaft naturf. Fr. zu Berlin I. 1927), and mentioned ‘pyrrhonotus’ twice in the protologue, while ‘pyrronotus’ was only presented in the caption to Plate 10. It seems unlikely that the spelling ‘pyrrhonotus’ is a lapsus. Note that pyrrhos (Greek: Πύρρος) originates from the Greek word pyr (fire), meaning ‘flame-colored’, ‘fiery’, or ‘red-haired’, notus means ‘back’ which seems morphologically consistent and semantically appropriate for Erythrocebus.

From the time of its introduction in 1829 until 1981, ‘pyrronotus’ was frequently used (Table 1), probably mostly by those who had read both Hemprich & Ehrenberg (1829) and Hemprich & Ehrenberg (1833). M. Geoffroy Saint-Hilaire & Cuvier (1842) used ‘pyrronotus’. Apart from Hemprich & Ehrenberg (1833), I. Geoffroy Saint-Hilaire (1855) appears to have been the first author to apply ‘pyrrhonotus’. Sclater (1872, 1893), Schlegel (1876), Forbes (1897), Trouessart (1897), and Anderson & de Winton (1902) followed Geoffroy Saint-Hilaire (1855) by citing ‘pyrrhonotus’.

Figure 5. Adult male eastern patas monkey Erythrocebus patas pyrrhonotus, Kidepo Valley National Park, northeastern Uganda.

In 1905, Matschie brought ‘pyrronotus’ back into the literature. This usage was subsequently applied in some works (e.g., Allen 1925; Schwarz 1927; Hill 1966; Kock 1969; Yalden et al. 1977; Napier 1981), while ‘pyrrhonotus’ was retained in others (e.g., Pocock 1907; Elliot 1909, 1913; Hollister 1924; Allen 1939; Setzer 1956; Butler 1966; Dandelot 1974; Groves 1993, 2001, 2005; Grubb et al. 2003; Wallis 2013; De Jong et al. 2025; Table 1). The Global Biodiversity Information Facility (GBIF 2026), the IUCN Red List of Threatened Species (IUCN 2026), and the IUCN/SSC Primate Specialist Group (PSG 2026) use ‘pyrrhonotus’. The American Society of Mammalogist’s Mammal Diversity Database (MDD; 2026), however, uses ‘pyrronotus’.

The International Code of Zoological Nomenclature (ICZN, often referred to as the “Code”) is the global rulebook that ensures every animal species has one stable, universally accepted, scientific name. Following Article 32 (‘Original Spellings’) and Article 33 (‘Subsequent Spellings’) of the Code (1999), we conclude as ‘First Reviewers’ the following (Butynski and De Jong submitted):

1. That ‘pyrronotus’ Hemprich & Ehrenberg (1829) precedes ‘pyrrhonotus’ Hemprich & Ehrenberg, 1833), that ‘pyrronotus’ is the ‘correct original spelling’, and that these are the correct authority names and years of publication for these names.
2. That an emendation for ‘pyrrhonotus’ was provided by Hemprich & Ehrenberg (1833), but that this was an ‘unjustified emendation’ on the basis that ‘pyrronotus’ is a ‘correct original spelling’.
3. That the ‘unjustified emendation’ for ‘pyrrhonotus’ should now be taken as a ‘justified emendation’ on that basis that ‘pyrrhonotus’ has been in prevailing usage for about the last 50 years.
4. That ‘pyrrhonotus’ Hemprich & Ehrenberg, 1829, is now the ‘current valid spelling’.
5. That ‘pyrronotus’Hemprich & Ehrenberg, 1829, is now the ‘historic original spelling’ and ‘invalid’.

As far as we are aware, the correct name for the eastern patas monkey has not been of much concern—until now. The considerable disparities among the names and years used for the authority of the names ‘pyrronotus’ and ‘pyrrhonotus’ strongly suggests that few authors studied the two publications in which these names first appeared. This seems to be the reason that ‘pyrrhonotus’ has been able to gain common usage over the past 120 years or so.

Figure 6. Adult female Eastern patas monkey Erythrocebus patas pyrrhonotus, Kidepo Valley National Park, northeastern Uganda.

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