Sciurus (Hadrosciurus) pyrrhinus Thomas, 1898

Voss, Robert S., Fleck, David W. & Jansa, Sharon A., 2019, Mammalian Diversity And Matses Ethnomammalogy In Amazonian Peru Part 5. Rodents, Bulletin of the American Museum of Natural History 2024 (466), pp. 1-180 : 29-30

Sciurus (Hadrosciurus) pyrrhinus Thomas, 1898

Figures 4A, 7A, 8B, 10B, 10E, 11B, 13

VOUCHER MATERIAL (N = 22): Jenaro Herrera (MUSM 23833), Marupa (AMNH 98430), Nuevo San Juan (AMNH 272859; MUSM 11192, 13354), Orosa (AMNH 73864, 73865, 73868, 73869, 73871–73874, 73877, 74057, 74059–74065).

UNVOUCHERED OBSERVATIONS: Choncó ( Amanzo, 2006), Itia Tëbu ( Amanzo, 2006), Río Yavarí ( Salovaara et al., 2003), Río Yavarí-Mirím ( Salovaara et al., 2003), San Pedro ( Valqui, 1999, 2001).

IDENTIFICATION: Specimens and sightings of Sciurus pyrrhinus from our region have long been identified as S. igniventris (e.g., by Patton 1984; Salovaara et al., 2003; Amanzo, 2006; Sánchez-Vendizú et al., 2021). Although we follow Vivo and Carmignotto (2015) and Abreu et al. (2020b) by treating S. pyrrhinus and S. igniventris as distinct species, we are not convinced that they are consistently diagnosable morphologically. Additional analyses of sequence data and close study of pelage traits are needed to better document current taxonomic distinctions. As recognized in this report, Sciurus pyrrhinus is a geographically variable species that occurs north and south of the Amazon and includes the nominal taxa cocalis Thomas, 1900a , and fulminatus Thomas, 1926.

8 The type series of Macroxus irroratus was collected by E. Bartlett on the “Upper Ucayali ” ( Gray, 1867: 431). Thomas (1899: 40) remarked that these specimens were “probably from near Sarayacu” (a town on the Ucayali in modern Loreto department), but he cited no evidence for this inference, and none has come to light subsequently. In the absence of other indications, it would seem reasonable to assume that Bartlett’s “Upper Ucayali ” corresponds to the “Alto Ucayali ” of Peruvian usage, a term that denotes the river above its confluence with the Río Pachitea, a left-bank tributary ( Faura-Gaig, 1964: 287). This portion of the river lies entirely within the modern department of Ucayali. BMNH 66.3.28.8 is currently labelled as the lectotype, but we can find no published record that any of Gray’s syntypes has been so designated.

Specimens of Sciurus pyrrhinus from the Yavarí-Ucayali interfluve are large (645–715 g) squirrels that are uniformly grizzled reddish or reddish brown from crown to rump (none of the skins from our region are melanistic). Additionally, all examined specimens have bright orange postauricular patches (fig. 4A). The fore- and hind feet are always covered with self-orange fur, and the ventral pelage is uniformly pale orange. The fur at the base of the tail is often much darker than the dorsal body fur (almost blackish in some individuals), but the rest of the tail is conspicuously orange, although variously streaked or mottled with black in some specimens. Every examined parous female specimen with countable mammae in our material (N = 7) has eight teats.

Skulls of this species have a relatively short, broad rostrum and, like other members of the Hadrosciurus clade, only a single premolar in each upper cheektooth row. None of the specimens that we scored for cranial character variation has a distinct sagittal crest on the interparietal, and all of them have separate (not confluent) sphenopalatine and dorsal palatine foramina (fig. 7A). Additionally, most specimens (17 out of 18 scored) exhibit bilateral alisphenoid-parietal contact (AMNH 272859 has narrow squamosal-frontal contact on the right side), and most (13 of 19) have an accessory oval foramen on each side (six specimens lack this foramen on one or both sides). The sphenopalatine vacuities in the roof of the mesopterygoid fossa are very small or absent in all the specimens we examined.

The only other squirrel in our region with which Sciurus pyrrhinus could possibly be confused is S. spadiceus . Although these species are similar in size (table 7), they are easily distinguished with specimens in hand. 9 Red-phase specimens of S. spadiceus have much darker (sometimes almost blackish) fur on the crown of the head, lack conspicuous postauricular patches,

9 Field identifications of free-ranging individuals are more problematic, although blackish individuals in our region seem to always be Sciurus spadiceus .

have grizzled-brownish (rather than self-orange) fore- and hind feet, and have more abundantly black-streaked tails. Skulls of S. spadiceus have longer and narrower rostrums than skulls of S. pyrrhinus , a difference that is visually obvious in side by side cranial comparisons (figs. 8, 10), and which is reflected in nonoverlapping measurements of diastemal length (LD, table 7). Additionally, in S. spadiceus the left and right temporalis scars usually converge to form a distinct sagittal crest on the interparietal bone (fig. 8A), the sphenopalatine and dorsal palatine foramina in the medial wall of the orbit are usually confluent (fig. 7B), and the sphenopalatine openings in the roof of the mesopterygoid fossa are always large. On average, S. spadiceus has deeper lower incisors than S. pyrrhinus , although there is some species overlap in this dimension (DI, table 7).

Of the two subspecies of Sciurus pyrrhinus recognized by Vivo and Carmignotto (2015), our material closely resembles S. p. fulminatus in size and pelage traits based on our examination of the holotype (BMNH 20.7.1.1) and other specimens of fulminatus, which Thomas (1926) described from the lower Rio Negro, Amazonas state, Brazil. By contrast, our material differs from the type (BMNH 97.10.3.12) and other specimens of S. p. pyrrhinus from the Andean