Phyllotis stenops Osgood 1914

Rengifo, Edgardo M. & Pacheco, Víctor, 2015, Taxonomic revision of the Andean leaf-eared mouse, Phyllotis andium Thomas 1912 (Rodentia: Cricetidae), with the description of a new species, Zootaxa 4018 (3), pp. 349-380 : 366-375

Phyllotis stenops Osgood 1914

Narrow-nasal Leaf- eared Mouse

Phyllotis andium stenops: Osgood (1914:165) Phyllotis tamborum: Osgood (1914:165)

Phyllotis andium tamborum: Thomas (1926: 614) Phyllotis andium: Thomas (1926: 162)

Holotype. Adult male, Field Museum of Natural History ( FMNH) No. 19840, collected on May 30, 1912 by W.H. Osgood and M.P. Anderson.

Type locality. Rio Utcubamba, 15 miles above Chachapoyas, [Amazonas,]

Peru.

Distribution. Known only at eastern Marañón River, Amazonas Department in Peru, 1289–2423 m elevation (see Fig. 13 )

Measurements. External and craniodental measurements are presented in Table 2 .

Emended diagnosis. Phyllotis stenops exhibits dark grey coloration at bases of dorsal pelage; tail long (± 127.00 mm) and notoriously bicolored; condyle-incisive length is 25.21 mm in average, narrow nasal tips; premaxillary-naso-frontal joint same level or posterior to maxillary-fronto-lacrimal joint; narrow and moderately concave interorbital region (± 4.08 mm); internal carotid bounded by petrosal and ectotympanic portions of auditory bulla; long Eustachian tube, reaching the parapterygoid process; and small paroccipital process ( Fig. 10 ).

Description. The Dorsal pelage is composed of rich-brow hairs that are dark grey at base, and the hairs are dense, long, averaging 13 mm over rump; the ventral pelage is whitish with a short grey basal band and a white distal band; a pectoral streak is present but barely conspicuous. The pinnae are comparatively short in comparison to congeners; the orbicular ring is absent. The genal, superciliary, submental, interramal and mystacial vibrissae are present; the mystacial vibrissae reach the posterior pinnae border when laid back against head. The tail is distinctly longer than combined head and body (± 127 mm). It is conspicuously bicolored, dark above and pale neutral gray below, with furred dorsal and ventral sides; the hair along the shaft extend over more 2 or 3 rows of scale. The dorsal surface of the manus is covered with fine white hairs and the ungual tuft is present but not very dense. The margin of the ventral surface of the claws is closed at the base. The III pad is above the II and IV pads and the hypothenar is longer than the thenar. The metacarpal patch is absent. The pes is slender and elongate, with white hair on the dorsal surface, and a scarce ungual tuft; the heel is furred. Six small plantar pads are present. The hypothenar is behind IV pad and it is smaller than the thenar, though both are separated by a gap; the plantar surface among the pads is squamated. The metatarsal patch is absent. Digit I is the shortest and digit V is smaller than II, III and IV digits.

The skull profile is convex and slightly more swollen in the Interorbital region ( Fig. 10 ). The rostrum is short and narrow. The nasolacrimal capsule is moderately broader than the anterior portion of the rostrum (in the dorsal view). The nasal is conical and long and anteriorly it is broad; in lateral view, it projects anterodorsally beyond the premaxillae and the anterior border of the incisors. The fronto-nasal suture is aligned to the fronto- premaxillary suture. The premaxillary-naso-frontal joint is posterior to the maxillary-fronto-lacrimal joint. The premaxillary is short and narrow; it projects slightly anteriorly to the plane of the incisors. The zygomatic plate is moderately broad with a vertical dip and the anterodorsal spinous process is absent; the zygomatic notch is deep; the infraorbital foramen is narrow; the superficial masseteric origin is small but conspicuous; the antorbital bridge lies below the dorsal surface of the rostrum and it overlaps slightly and is connected to the lacrimal. The zygomatic arch has parallel-sides, which are slightly convergent anteriorly; the zygomatic process of the maxillary is narrow; it is barely wider than the antorbital bridge; the jugal is long and very thin. The interorbital region is very narrow and moderately concave, the molar bases are visible from the dorsal view; the supraorbital margin has sharp edges; the lacrimal is large and projects over the antorbital bridge. The frontal bone is narrow (in the dorsal view) and slightly swollen (in the lateral view) and it doesn't have have a medial depression. The braincase is rounded and the fronto-parietal suture is slightly serrated and convex; the parietal edge (on the squamosal-parietal suture) is smooth; the interparietal is small with a trapezoid-shape and both the interparietal-parietal and interparietalsupraoccipital sutures are dentate. The palatal region is long and narrow. The incisive foramen is long and narrow with parallel margins, extending to the M1 alveolus. The premaxillary portion of the septum builds a medial ridge overlapping on the vomer; the maxillary portion of the septum is moderately thin. The bony palate is moderately wide and long, extending behind the posterior plane of M3. The maxillo-palatal suture is dentate. The palatal lateral grove is deep. The maxillary palatal pit is placed close to maxillo-palatal suture. The posterior palatine foramen is very small. The posterolateral palatal pit is small and placed anterior to the mesopterygoid fossa. The mesopterygoid fossa is narrow and square-shaped with parallel sides. The palatal process is absent. The sphenopalatine vacuities are large and reach halfway to the basisphenoid. The presphenoid is present but thin. The parapterygoid fossa is triangular and wide, but with inconspicuous or absent vacuities. The parapterygoid process is short and swollen, projected outside. The middle lacerate foramen is moderately open. The alisphenoid strut is absent. The anterior opening of alisphenoid canal is smaller than the buccinator-masticatory and foramen ovale joint. The ethmoid foramen is small and it is placed dorsal to M2. The ethmoturbinals are moderate in size and smaller than sphenopalatine foramen. The sphenopalatine foramen is large with ovoid shape and bounded by palatine bone; the optic foramen is very large with half-moon shape. The orbitosphenoid is large and overlaps barely M3 or borders M3. The carotid circulation corresponds to the “primitive” condition (sensu Voss 1988) with a large stapedial foramen, a distinct squamosal-alisphenoid grove, and a wide sphenofrontal foramen; the internal carotid is large and bounded by the petrosal and the ectotympanic portion of the auditory bulla. The auditory region is formed by moderate-sized ectotympanic bullae. The tegmen tympani overlaps the posterior suspensory process of the squamosal, it has a sinuous groove; the ectotympanic ring is closed and the dorsal margin of the ectotympanic extends to make contact with the petrosal. The bony Eustachian tube is long; it is more developed than anterior margin of the middle lacerate foramen, and often contacts the parapterygoid process. The anterior process of the ectotympanic (stapedial spine) is moderate-size. The malleus and incus are exposed in the lateral view. The lamina of the malleus is square shaped with a long and thin parallel manubrium, with a well-developed and large orbicular apophysis. The processus brevis of incus is conspicuous have a rounded base and knob-like tip. The cephalic process of the malleus exhibits a thin crest. The postglenoid foramen is smaller than the subsquamosal fenestra; the hamular process of the squamosal is moderately broad and reaches the mastoid bone. The lambdoid ridge is absent. The basioccipital is narrow with a trapezoid-shape; it shows a medial spine that extends to the basioccipital—basisphenoid suture. The mastoid (the periotic capsule of the petrosal) is squared-shape with an open mastoid fenestra and a conspicuous mastoid-occipital opening. The occipital condyle is not evident in the dorsal view; the paroccipital process is very small.

The ventral margin of the mandible is slightly concave; the diastema is short with a weakly acute angle formed by the root of m1. The superior and inferior masseteric crests converge anteriorly forming a smooth crest that extends to the anterior edge of m1. The mental foramen is high and positioned on the dorsal surface of the diastema. The capsular process is present but small. The coronoid process is small but is level with the condyle process, forming a shallow sigmoid notch. The condylar process is rounded and is level with the angular process which has a deep angular notch.

The upper incisor has an orthodont orientation; the tips are rounded without incisor groves; the wear surface of the upper incisor face is flat and faces backwards. The tooth topography is tetralophodont with a flat crown (lightly hypsodont); the cusp arrangement on M1 is intermediate and on m1 it is alternate; the toothrow has a parallel orientation. The alveolus of M1 is placed anterior to the incisive foramen and slightly behind the posterior margin of the zygomatic plate. The procingulum of M1 is small and undivided; the paraflexus has a triangular shape, and it is sunken in to cover half of M1; the paraflexus and metaflexus are wider than the protoflexus and hypoflexus; the paracone and metacone are slightly narrower than the protocone and hypocone. The M2 has an “S” shape; the hypoflexus is slightly deeper and narrower than the metaflexus; the paraflexus is shallow. The M3 is smaller than the M2. The m1 has a procingulum that does not show an anteromedian flexid and is smaller than the metaconid, and equal to or larger than the protoconid; the metaflexid is small or slightly deep. The m2 has a conspicuous protoflexid. The m3 is smaller than the m2.

Natural history. There are no studies nor data on the natural history of Phyllotis stenops .

Remarks. P. t a m b or u m was described by Osgood (1914) based in one juvenile specimen from Tambo Carrizal, east of Balsas, Amazonas, which was considered similar to P. andium from Ecuador ( Pearson 1958). Based on our own examination of specimens collected near to the type locality of tamborum , we concluded that they correspond to P. stenops ; therefore tamborum is considered a synonymy of P. stenops .

Phyllotis occidens sp. nov. Western Leaf-eared Mouse

Holotype. Adult female collected on July 20, 1987 by Cesar Ascorra and deposited at Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima- Peru, The specimen is preserved as skin and skull, with the catalogue number MUSM 547 ( Figs. 9 , 10 ).

Paratype. Six adult specimens ( MUSM 546, 549, 550, 551, 552, and 553) preserved as skull and skin. Selected measurements of the holotype and paratype specimens are provided in Table 3 .

Type locality. Huarochiri, Huarochiri, Lima, Perú, at approximately 3100 m elevation, with geographic coordinates: 12°08'14.928"S, 76°13'54.984"W.

Distribution. Currently known from the western slope of the Cordillera Blanca and Cordillera Waywash, from Ancash to Lima department, 200–3800 m elevation (see Fig. 13 ).

Etymology. From the Latin word "occidental" meaning "western", referring to the known distribution of the species in the western Andes of Peru.

Measurements. External and craniodental measurements are presented in Table 2 .

Diagnosis. Soft and long fur with gray-yellowish tone, with intermixed dark and yellowish dorsal coloration, with neutral gray color at its base; weakly bicolored tail ( Fig. 11 ); nasal extends slightly beyond frontopremaxillary suture; supraorbital margin shows smooth-rounded edges, the maxillary palatal pits placed near the maxillo-palatine suture; distinct palatal process; short bony Eustachian tube that not reach the parapterygoid process; thin hamular processes of the squamosal; deep paraflexus of M2 ( Fig. 12 ).

Description. The dorsal pelage is composed of rich-brow hairs that have neutral grey at the base, the dorsal band on the dorsum is inconspicuous; the hairs are dense and long and average 13 mm over the rump; the ventral pelage is whitish with a short grey basal band followed by a white band; a pectoral streak is present but barely conspicuous ( Fig. 11 ). The pinnae are comparatively short in comparison to congeners; the auricular patch is inconspicuous, represented by some flew hairs over and under ears; the orbicular ring is absent. The genal, superciliary, submental, interramal and mystacial vibrissae are present; the mystacial vibrissae reach the posterior border pinna when laid back against head. The tail is barely longer than the head and the body together (± 120 mm). It is dimly bicolored, dark above and pale neutral gray below and both the dorsum and venter are furred; the hair along the shaft extends over more than 2 rows of scales. The dorsal surface of the manus is covered with fine white hairs and the ungual tuft is present but not very dense. The margin of the ventral surface of the claws is closed at the base. The III pad is above the II and IV pads and the hypothenar is longer than the thenar. The metacarpal patch is absent. The pes is slender and elongate, with white hair on the dorsal surface, and a scarce ungual tuft; the heel is furred. Six small plantar pads are present. The hypothenar is behind IV pad and it is smaller than the thenar, though both are separated by a gap; the plantar surface among the pads is squamated. The metatarsal patch is absent. Digit I is the shortest and digit V is smaller than II, III and IV digits.

The skull profile is convex and slightly more swollen in the interorbital region ( Fig. 12 ). The rostrum is short. The nasolacrimal capsule is moderately broader than the anterior portion of the rostrum (in the dorsal view). The nasal is conical and long and anteriorly it is broad; in lateral view it projects anterodorsally beyond the premaxillae and the anterior border of the incisors. The fronto-nasal suture is posterior to the fronto- premaxillary suture; the premaxillary-naso-frontal joint is anterior to the maxillary-fronto-lacrimal joint. The premaxillary is short and narrow, it projects slightly anteriorly to the plane of the incisors. The zygomatic plate is moderately broad with vertical dip, anterodorsal spinous process is absent; the zygomatic notch is deep; the infraorbital foramen is narrow; the superficial masseteric origin is small but conspicuous; the antorbital bridge lies below the dorsal surface of the rostrum, it overlaps slightly and connected to lacrimal. The zygomatic arch exhibits parallel-sides, which are slightly convergent anteriorly; the zygomatic process of maxillary is narrow; it is barely wider than the antorbital bridge; the jugal is long and very thin. The interorbital region is narrow and moderately concave, the molar bases are visible from the dorsal view; the supraorbital margin has sharp edges; the lacrimal is large and projects over the antorbital bridge. The frontal bone is moderately narrow (in the dorsal view) and slightly swollen (in the lateral view) and it doesn't have have a medial depression. The braincase is rounded and the fronto-parietal suture is slightly serrated and convex; the parietal edge (on the squamosal-parietal suture) is smooth; the interparietal is small with a trapezoid-shape and both the interparietal-parietal and interparietal-supraoccipital sutures are dentate. The palatal region is long and narrow. The incisive foramen is long and narrow with parallel margins, extending to the M1 alveolus. The premaxillary portion of the septum builds a medial ridge overlapping on the vomer; the maxillary portion of the septum is moderately thin. The bony palate is moderately wide and long, extending behind the posterior plane of M3. The maxillo-palatal suture is dentate. The palatal lateral grove is shallow. The maxillary palatal pit is close to the maxillo-palatine suture. The posterior palatine foramen is very small. The posterolateral palatal pit is small and placed anterior to the mesopterygoid fossa, but in some cases beside it. The mesopterygoid fossa is narrow and square-shaped with parallel sides. The palatal process is present and very visible. The sphenopalatine vacuities are large and reach halfway to the basisphenoid. The presphenoid is present but thin. The parapterygoid fossa is triangular and wide, but with inconspicuous or absent vacuities. The parapterygoid process is long and projected outside.The middle lacerate foramen is moderately open. The alisphenoid strut is absent. The anterior opening of alisphenoid canal is smaller than the buccinator-masticatory and foramen ovale joint. The ethmoid foramen is small and it is placed dorsal to M2. The ethmoturbinals are moderate in size and smaller than sphenopalatine foramen. The sphenopalatine foramen is large with ovoid shape and bounded by palatine bone; the optic foramen is very large with half-moon shape. The orbitosphenoid is large and overlaps barely M3 or borders M3. The carotid circulation corresponds to the “primitive” condition (sensu Voss 1988) with a large stapedial foramen, a distinct squamosal-alisphenoid grove, and a wide sphenofrontal foramen; the internal carotid is large and bounded by both the basioccipital and the ectotympanic portion of the auditory bulla. The auditory region is formed by moderate-sized ectotympanic bullae. The tegmen tympani overlaps the posterior suspensory process of the squamosal, it has a sinuous groove; the ectotympanic ring is closed and the dorsal margin of the ectotympanic extends to make contact with the petrosal. The bony Eustachian tube is short; it at same level or posterior of the anterior margin of the middle lacerate foramen, it does not reach to level parapterygoid process. The anterior process of the ectotympanic (stapedial spine) is moderate-size. The malleus and incus are exposed in the lateral view. The lamina of the malleus is square shaped with a long and thin manubrium parallelly orientated, and it has a well-developed and large orbicular apophysis. The processus brevis of incus is conspicuous have a rounded base and knob-like tip. The cephalic process of the malleus exhibits a thin crest. The postglenoid foramen is smaller than the subsquamosal fenestra; the hamular process of the squamosal is thin and reaches the mastoid bone. The lambdoid ridge is absent. The basioccipital is narrow with a trapezoid-shape; it shows a medial spine that extends to the basioccipital—basisphenoid suture. The mastoid (the periotic capsule of the petrosal) is squared-shape with an open mastoid fenestra and a conspicuous mastoidoccipital opening. The occipital condyle is not evident in the dorsal view; the paraoccipital process is small.

The upper incisor has an orthodont orientation; the tips are rounded without incisor groves; the wear surface of the upper incisor face is flat and faces backwards. The tooth topography is determined as having a tetralophodont dental pattern; it has a flat crow (lightly hypsodont); the cusp arrangement on M1 is intermediate and on m1 it is alternate; the toothrow has a parallel orientation. The alveolus of M1 is placed anterior to the incisive foramen and slightly behind the posterior margin of the zygomatic plate. The procingulum of M1 is small and undivided; the paraflexus has a triangular shape, and it is sunken in to cover half of M1; the paraflexus and metaflexus are wider than the protoflexus and hypoflexus; the paracone and metacone are slightly narrower than the protocone and hypocone. The M2 has an “S” shape; the hypoflexus is slightly deeper and narrower than the metaflexus; the paraflexus is distinctly deep (viewed in juvenile specimens, so superficial wear is not evident). The M3 is smaller than the M2. The m1 has a procingulum that does not show an anteromedian flexid and is smaller than the metaconid, and equal to or larger than the protoconid; the metaflexid is small or slightly deep. The m2 has a conspicuous protoflexid. The m3 is smaller than the m2.

Natural History. Phyllotis occidens prefers shrubby habitats ( Pearson 1958, Pearson 1972, Cerro 2005). Population density and reproduction were studied by Arana et al. (2002), who mentioned Phyllotis occidens has a density that vary between 0–3 individuals per ha2 and seasonal reproduction with pregnant females in the Lomas de Lachay´s population occurs between July and October. Pizzimenti & De Salle (1980) mentioned an omnivore diet composed mainly of leafy vegetation, forb, insect, and seed.

Figures

FIGURE 9. Dorsal, ventral and lateral views of the cranium and the mandible of Phyllotis andium (MUSM 24754).

FIGURE 10. Dorsal, ventral and lateral views of the cranium and the mandible of Phyllotis stenops (FMNH 19842).

FIGURE 11. Dorsal and ventral views of the skin of Phyllotis occidens sp. nov. (MUSM 547, holotype).

FIGURE 12. Dorsal, ventral and lateral views of the cranium and the mandible of Phyllotis occidens sp. nov. (MUSM 547, holotype).

FIGURE 13. Illustration map showing the distribution range of Phyllotis andium, Phyllotis. stenops, and Phyllotis occidens sp. nov.

Tables

TABLE 3. Measurements of the type series of Phyllotis occidens sp. nov. from Huarochiri, Huarochiri, Lima, Perú. The number in the column heading is the MUSM catalogue number. Age and sex are in parentheses, f = female, m = male.

Variable TL T F	Holotype 547 * (IV, f) 216.00 121.00 24.00	Paratype Paratype 544 545 (II, m) (IV, m) 185.00 - 101.00 - 26.00 27.00	Paratype 546 (III, m) - - 26.00	Paratype 549 (V, m) 224.00 123.00 26.00	Paratype 550 (III, f) 225.00 122.00 26.00	Paratype 551 (III, m) 220.00 120.00 26.00	Paratype 552 (IV, f) 238.00 125.00 26.00	Paratype 553 (V, m) 223.00 120.00 25.00
E CIL	22.00 25.40	21.00 23.00 24.50 26.48	22.00 25.35	23.00 27.75	20.00 24.37	21.00 23.90	22.00 26.09	23.00 27.55
ZB BB IOC RL	14.45 12.76 4.47 8.74	13.65 15.15 12.60 13.27 4.25 4.34 8.25 9.46	14.12 12.65 4.29 8.61	- 13.35 4.45 9.52	- 13.01 4.27 8.66	13.45 12.48 4.48 8.50	14.48 13.03 4.26 9.64	15.50 13.12 4.19 9.83
NL RW	11.20 5.42	10.79 11.60 4.91 4.99	10.68 5.11	12.32 5.48	11.13 4.62	10.57 4.55	11.63 4.97	12.33 5.60
RW2 OL DL MTRL	4.30 9.87 7.21 4.43	3.96 4.12 9.47 10.14 6.88 7.63 4.51 4.74	4.02 9.50 7.07 4.48	4.45 10.60 8.30 4.67	4.03 9.37 6.76 4.57	4.09 9.26 6.63 4.62	4.18 10.08 7.65 4.70	4.37 10.42 7.92 4.73
IFL AW	6.26 5.69	6.27 6.57 5.64 5.89	6.52 5.87	6.90 5.85	6.04 5.74	5.86 5.62	6.70 5.99	6.86 6.04
OCW MB BOL MFL	6.39 11.10 1.83 3.48	6.82 6.87 11.10 11.76 1.88 2.09 3.54 3.55	6.77 11.39 1.88 3.42	6.90 11.75 2.29 3.80	6.72 11.43 1.70 3.24	6.67 10.75 1.93 3.30	6.63 11.37 2.10 3.63	6.67 11.64 2.54 3.74
MFW CD	1.46 10.07	1.20 1.23 10.15 10.90	1.24 10.51	1.21 10.58	1.23 10.41	1.26 10.01	1.25 10.30	1.14 10.48
ZP	2.83	2.98 3.00	2.78	3.19	2.89	2.82	3.07	3.28