Sciurus (Hadrosciurus) spadiceus ( Olfers, 1818 )

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 : 33-34

Sciurus (Hadrosciurus) spadiceus ( Olfers, 1818)

Figures 4B, 7B, 8A, 10C, 10F, 11C, 13

VOUCHER MATERIAL (N = 41): Boca Río Yaquerana (FMNH 88969–88971), Bombo (AMNH 98424, 98425), Marupa (AMNH 98434, 98435), Nuevo San Juan (AMNH 268253, 272825, 272860; MUSM 13355), Orosa (AMNH 73863, 73866, 73867, 73870, 73875–73888, 74059, 74061, 74063), Quebrada Esperanza (FMNH 88972, 88973), Quebrada Vainilla (LSUMZ 28413, 28414), Río Blanco (AMNH 98406), San Fernando (FMNH 88967, 88968), Santa Cecilia (FMNH 87170, 87171). Additionally, Pavlinov (1994) reported three ZMMU specimens from Jenaro Herrera that we have not seen.

UNVOUCHERED OBSERVATIONS: Actiamë ( Amanzo, 2006), Anguila ( Escobedo-Torres, 2015), Choncó ( Amanzo, 2006), Divisor ( Jorge and Velazco, 2006), Itia Tëbu ( Amanzo, 2006), Río Yavarí ( Salovaara et al., 2003), Río Yavarí-Mirím ( Salovaara et al., 2003), Tapiche ( Jorge and Velazco, 2006), San Pedro ( Valqui, 1999, 2001).

IDENTIFICATION: Sciurus spadiceus is another large (540–683 g) squirrel, equivalent in size to sympatric S. pyrrhinus , but differing from that species in several external and craniodental traits (table 2). The most conspicuous difference is coloration: whereas S. pyrrhinus is consistently reddish in our region, most individuals of S. spadiceus (30 of 38 examined skins and fluid-preserved specimens) are melanistic, with black or grizzled-blackish fur. Red-phase individuals of S. spadiceus might be mistaken for S. pyrrhinus at a distance, but the crown of the head is darker in S. spadiceus , and postauricular patches are absent or indistinct (fig. 4B); additionally, the dorsal fur of red-phase S. spadiceus is duller and more conspicuously grizzled than that of S. pyrrhinus , and the distal limbs and feet are grizzled reddish rather than clear red or orange (fig. 13). As in other species in the subgenus Hadrosciurus , most females with countable mammae (N = 14) have eight teats (one fluid-preserved specimen, AMNH 272860, has seven).

Sciurus spadiceus has a visibly longer rostrum than other squirrels in our region (figs. 8, 10), and diastemal length (LD, table 7) is sufficient to distinguish skulls of this species from those of sympatric S. pyrrhinus . Additionally, the right and left temporalis scars converge to form a small but distinct sagittal crest on the interparietal of most specimens of S. spadiceus (29 of 32 scored for this character; fig. 8A), another unusual trait. Other distinctive cranial features include consistently large sphenopalatine vacuities in the roof of the mesopterygoid fossa and a large sphenopalatine foramen in the orbit that is usually confluent with the dorsal palatine foramen (in 37 of 40 specimens) and that usually exceeds the optic foramen in diameter (fig. 7B). An accessory oval foramen is present bilaterally in most specimens (33 of 37), and most specimens (33 of 40) exhibit bilateral alisphenoid-parietal contact. The lower incisors are remarkably deep in proportion to their width and, as in other species of the subgenus Hadrosciurus , only a single premolar is present in each upper cheektooth row.

Phylogenetic analyses of mtDNA sequences ( Abreu et al., 2020b) suggest that Sciurus spadiceus exhibits little phylogeographic structure across its enormous geographic range, so it seems unlikely that the subspecies recognized by Vivo and Carmignotto (2015) are evolutionarily significant taxa. However, it is relevant to point out that the trinomial nomenclature proposed by those authors is based on the assumption that the type locality of S. spadiceus is in the Brazilian state of Mato Grosso, which cannot possibly be correct. Olfers (1818) based his description of S. spadiceus on ZMB material from Brazil, but the only specimens of Brazilian mammals in the ZMB collection prior to 1818 were either collected by Francisco Agostinho Gomes in the Atlantic Forest or by Friedrich Wilhelm Sieber in eastern Amazonia ( Voss and Angermann, 1997). The likeliest place where Olfers’ type material was collected—consistent with the geographic range of S. spadiceus ( Vivo and Carmignotto, 2015: map 7) and Sieber’s known itinerary ( Papavero, 1971: 48)—is somewhere along the right (south) bank of the Amazon west of the Tapajós or along the left (west) bank of the Tapajós itself. In fact, Olfers’ (1818: 208) description 10 better fits the coloration of specimens from the lower Tapajós (in the AMNH) than that of specimens from Mato Grosso (as described by Vivo and Carmignotto, 2015). It is not known whether Olfers’ type material still exists at the ZMB (C. Funk, personal commun.), but, if it cannot be found, a neotype should be selected to fix the application of this name.

ETHNOBIOLOGY: See the account for Sciurus pyrrhinus (above), which the Matses do not recognize as a different species.

MATSES NATURAL HISTORY: See the account for Sciurus pyrrhinus (above), which the Matses do not recognize as a different species.

REMARKS: The four specimens of Sciurus spadiceus accompanied by habitat information from our region were all shot in the daytime by Matses hunters. Of these, one was shot in secondary upland forest (probably an abandoned swidden), one was shot in a palm swamp, and two were shot in primary riparian (probably seasonally inundated) forest. As for S. pachecoi and S. spadiceus (see above), the large Orosa series was probably collected in seasonally inundated forest, but the specimens from Quebrada Vainilla were apparently taken in primary terra firme forest ( Robbins et al., 1991).