Sturnira boadai, Yánez-Fernández & Marchán-Rivadeneira & Velazco & Burneo & Tinoco & Camacho, 2023

Yánez-Fernández, Viviana, Marchán-Rivadeneira, M. Raquel, Velazco, Paúl M., Burneo, Santiago F., Tinoco, Nicolás & Camacho, M. Alejandra, 2023, On the taxonomic identity of Sturnira nana Gardner and O’Neil, 1971 (Chiroptera: Phyllostomidae), from Ecuador, with the description of a new species of Sturnira, American Museum Novitates 2023 (4001), pp. 1-28 : 11-16

Sturnira boadai , sp. nov.

Boada’s Yellow-shouldered Bat

Murciélago de hombros amarillos de Boada

Sturnira nana : Boada, 2011: 76.

Sturnira nana : Regalado and Albuja, 2012: 160.

Sturnira sp. A : Tirira, 2012: 268.

Sturnira nana : Solari et al., 2019: 543 (pt.)

Sturnira nana : Narváez-Romero et al., 2020: 81.

Sturnira nana : Tirira et al., 2022: 33.

HOLOTYPE: An adult female ( QCAZ 11122 ) collected on March 12, 2009, by Carlos Boada. The body is preserved in 75% ethanol, with the skull removed and cleaned. Muscle and liver tissues preserved in 95% ethanol are also deposited at QCAZ.

TYPE LOCALITY: Las Orquideas , Miazi Alto near Nangaritza River basin, Zamora Chinchipe province, Ecuador, 04°15.48′S, 78°40.59′W, between 1250–1430 m ( fig. 5 ).

PARATYPES: One female ( QCAZ11120 ) and four males ( QCAZ11116 , QCAZ11119 , QCAZ11121 , QCAZ11123 ) were also collected at the type locality on March 12, 2009 by Carlos Boada. All specimens are preserved in 75% ethanol, with the skulls removed and cleaned.

DISTRIBUTION: Known from two confirmed localities in Zamora Chinchipe Province: Las Orquideas, Miazi Alto near Nangaritza River basin (04°15′29.30″ S; 78°40′53.40″ W) and Military Detachment Cóndor Mirador, El Pangui (03°38′08″ S; 78°23′22″ W) near the border of Ecuador and Peru ( fig. 5 ). We expect that S. boadai also occurs in adjacent, climatically similar habitats of northeastern Peru.

DIAGNOSIS: Sturnira boadai is a small species (FA = 32.5–33.8 mm, GLS = 18.3–19.2 mm; tables 1 , 6 ) that is externally distinguished from other congeners by lacking shoulder glands (epaulettes), and by its sparsely haired hind feet, interfemoral membrane, and forearm. The braincase is globular, and the zygomatic arches are incomplete. The foramen magnum has an acutely angled anteroventral margin. The inner upper incisors protrude notably from the skull profile, and in rostral view, the distal third of their medial surfaces are in contact. Two to four lower incisors are present, of which the inner incisors are trilobed and subtriangular. The outer lower incisors (when present) are small, bilobed, with blunt edges, and inclined towards the inner incisors. In the series of specimens collected in Miazi Alto (N = 9), some intraspecific variation is observed in relation to the number and presence of the outer lower incisors: most specimens exhibit four lower incisors (e.g., QCAZ11122) and, in specimens where the outer lower incisors are absent (e.g., QCAZ11121), superficial alveoli or diastemata are observed. One specimen (QCAZ11119) has no outer lower incisors, alveoli, or spaces between i1 and the canine. Lastly, two specimens (QCAZ11120 and QCAZ11123) exhibit only one outer incisor. In one of the latter cases (QCAZ 11123), the external incisor is minuscule and difficult to observe with the naked eye.

DESCRIPTION: Sturnira boadai is one of the two smallest species of yellow-shouldered bats, with most measurements overlapping those of S. nana . The dorsal fur is dense and dark brown, with long (6–7 mm) hairs. Dorsal hairs are tetracolored with a narrow white basal band of around 10% of the hair length, an epibasal brown band of about 40% of the hair length, a subterminal light-brown band of about 30% of the hair length, and a dark-brown apical band that covers 20% of the hair length. The ventral fur and underparts are lighter than the dorsal fur. Ventral hairs are tricolored due to lacking the terminal dark brown tip of the dorsal hairs. The fur is sparsely distributed at the dorsal surface of the femur, tibia, hind feet, interfemoral membrane, and upper forearm. The wing membranes are grayish to blackish brown. Shoulder glands are absent. The nose leaf is dark brown, long, and narrow.

The skull of Sturnira boadai has a globular braincase with a flattened rostrum by comparison with other members of the subgenus Corvira . A sagittal crest is not developed. The zygomatic arches are always incomplete. The basisphenoid pits and septum are shallow. The anteroventral margin of the foramen magnum is angular.

The dental formula is I2/1–2, C1/1, P2/2, M3/3 x 2 = 30–32. The inner upper incisor (I1) is proodont, with a straight occlusal edge and a well-developed posterolateral cusp. The outer upper incisors (I2) are small and opisthodont. I2 is close to but not in contact with the posterolateral cusp of the I1 ( fig. 6A ). I1 is more than three times the height of I2. The upper canine (C1) is long and robust. The first upper premolar (P3) is small, narrow, and half the height of the second upper premolar (P4). P4 is broad, with a blunt distal cusp that is more noticeable in some specimens than in others, but it is always present. Diastemata are present between P3 and C1, and between P3 and P4. M1 and M2 are broad. The anteroposterior length of the first upper molar (M1) is greater than that of M2 ( fig. 1B ). In occlusal view, the paracone of M1 is shorter than the metacone. The second upper molar (M2) is ovoid and has a broad crown. The third upper molar (M3) is small, with a crown area approximately one-half that of M2 ( fig. 1F ).

Two to four lower incisors are present. The inner lower incisor (i1) is trilobed. When present, the outer lower incisor (i2s) is minute, bilobed, and approximately one-third the size of i1. The anterior surface of the lower canine(c1) is in contact with the entire posterior surface of the i2 ( fig. 6B ), but when i2 is missing, the c1 is in contact with i1. The lower canines are long, narrow, robust, and laterally divergent, with their shafts slanted outward. The anteroposterior length of the first lower premolar (p2) is greater than that of the second lower premolar (p4). In lateral view, p2 exhibits an irregular, tricuspid border that is wider (anteroposterior dimension) than the crown of the tooth is tall. By contrast, p4 is taller than it is wide, and it has a well-developed main cusp. Both lower premolars are separated by a diastema ( fig. 1H ). The first lower molar (m1) is broad. The anteroposterior length of m1 is larger than that of the second lower molar (m2). The third lower molar (m3) is small, with two well-defined lobes separated by a notch between the metaconid and entoconid. The metaconid and entoconid of m1 and m2 are moderately defined. Adjacent upper and lower teeth are separated by narrow diastemata ( fig. 1H ).

COMPARISONS: Among other species traditionally referred to the subgenus Corvina , Sturnira boadai differs from S. bidens in size, being notably smaller. Morphologically, S. boadai has sparsely haired hind feet and uropatagium, whereas both structures are densely haired in S. bidens . Additionally, S. boadai possesses one or two pairs of lower incisors, whereas S. bidens always has a single pair of lower incisors. The anterior margin of the foramen magnum in S. boadai is angular, whereas it is rounded in most S. bidens specimens. Lastly, the zygomatic arches are incomplete in S. boadai , whereas they can be complete or incomplete in S. bidens .

Externally, Sturnira boadai and S. nana are similar. Epaulettes (patches of stained shoulder hairs) are not evident in either species. The dorsal fur is long and tetracolored in both species, and the forearm, legs, feet, proximal segments of the wings, and uropatagium are sparsely covered with long hairs. However, both species can be distinguished by several craniodental characteristics. The skull has a globular braincase and a less elongated rostrum in S. boadai , whereas the braincase is relatively long with a narrow, sloping rostrum in S. nana . The anterior margin of the foramen magnum is angular in S. boadai , whereas it is rounded S. nana . The zygomatic arches are always incomplete in S. boadai , whereas they can be complete or incomplete in S. nana . P3 is small, narrow, sharp crowned, and not in contact with either C1 or P 4 in S boadai , whereas P3 is broader and in contact with both C1 and P 4 in S. nana . Lastly, M3 is less wide in lateral view, whereas M3 is broader in S. nana .

ETYMOLOGY: The epithet boadai is dedicated to the memory of the Ecuadorian mammalogist Carlos Boada (1973–2015). Carlos was passionate about studying small mammals, especially bats and rodents. His academic contributions to the knowledge of Ecuadorian mammals were remarkable and primarily included taxonomic assessments and biological inventories. Carlos trained an extensive group of young mammalogists in the country, and herein we commemorate his early departure by naming this new species in his honor.

Figures

FIGURE 1. A, B. Lateral, C, D. dorsal, and E, F. ventral views of the skulls and G, H. lateral view of the mandibles of Sturnira nana (AMNH 219172, left column) and Sturnira EC (QCAZ 11122, right column). Red arrows show the differences between the two skulls.

FIGURE 5. Map of NW South America showing the collection localities of Sturnira bidens (circles), S. nana (diamonds), and Sturnira boadai, sp. nov. (stars), analyzed in this study. The collection points of Sturnira nana overlap, so only two diamonds are observed.

FIGURE 6. A. Upper and lower incisors of the holotype of Sturnira boadai, sp. nov. (QCAZ 11122). B. Detail of incisors. Photographs by Rubén D. Jarrín.