Description
Eleutherodactylus maculabialis is a relatively small frog only described from males with a snout-vent length range of 17.9 - 24.7 mm. Its head is longer than it is wide, and slightly wider than its body. From a dorsal view the short snout is subovoid and from a lateral profile it is rounded. The diameter of the eye is about equal to the distance between the eye and the tympanum. The eyelid width is about a third of the interorbital distance. The indistinct tympanum is small, circular, and has a width of 0.7 mm at its maximum. The tympanum has no detectable supra-tympanic fold. The hand has three palmar tubercles - a large middle palmar tubercle that is flanked by an inner palmar tubercle that is ~70% of the size of the middle and an outer palmar tubercle that is ~45% of the middle. The relative finger lengths are I < II < IV < III and there are pads on fingers two, three, and four that expand to roughly 1.5 - 2.1 times the narrowest point of fingers the third and fourth fingers. These expanded finger pads are slightly rounded. The tibia is 44 - 50% of the snout-vent length and the femur is 41 - 47%. The foot length is 66 - 73% of the snout-vent length. The planter has a round, moderately-sized outer metatarsal tubercle that is ~66% of the length of the spherically, oval inner metatarsal tubercle. The toe relative lengths are I < V < II < III < IV with toes II and V being very similar. There is an indistinct, compact lumbar gland located above the inguinal region. The skin is smooth or slightly shagreen in life, but the lateral surface becomes shagreened and the ventral surface is slightly areolate in preservative. Males have vocal slits (Grünwald et al. 2021).

DIAGNOSIS:

Eleutherodactylus maculabialis has a wide variety of distinguishing traits that help to distinguish it from other species of Eleutherodactylus. The main features E. maculabialis possesses that differentiate it from other Eleutherodactylus species is a very small, indistinct tympanum that lacks a visible tympanic annulus, a compact and raised lumbar gland above the inguinal region, and a distinctive ventral epidermis that is not clear with non-white visceral peritoneum and abdominal vein. This species also displays expanded digital tips, which are more than 1.5 times the width of the narrowest part of finger three and four that differentiate it from other members of the Eleutherodactylus modestus species group. The inguinal gland that is barely visible in life in E. maculabialis differentiates from other members of the Eleutherodactylus nitidus species group, of which it is a part of. More specifically, this gland is absent from E. erythrochomus, E. nebulosus and E. pipilans but distinct in all other members (Grünwald et al. 2021).

COLORATION:

In life, the dorsum is variable and ranges from orange, tan, reddish-tan, to brown. The dorsum also has pairs of dark brown mottling patches that become increasingly dense as it approaches the middorsal area. The loreal region has a dark brown background color with large orange to white spots on the lower region near the upper labia and on the upper labia. There is an interorbial bar that is of similar color as the lightest parts of the dorsum. The flanks transition to a lavender or grey coloration toward the belly and have dark brown mottling with small white spots. The fore- and hind limbs have irregular brown transverse bars. There are flash colors in the groin area. The ventrum is grey with orange and white spots on the throat and upper chest. White marbling may also be present on the ventrum. The ventrum is partially translucent and the visceral peritoneum is clear. In preservative, the dorsum becomes light brown and the markings remain darker. The throat becomes light brown while the rest of the ventrum becomes white (Grünwald et al. 2021).

VARIATION:

Eleutherodactylus maculabialis had slight variations in relative finger pad size and coloration and patterning (Grünwald et al. 2021).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Mexico

View distribution map in BerkeleyMapper.

Eleutherodactylus maculabialis has a known distribution of roughly 150 km² in the Sierra Madre del Sur of central Guerrero, Mexico. The species has been found at elevations of roughly 900 - 2,100 m in tropical evergreen forests, cloud forests, oak woodlands, pine-oak forests, and riparian vegetation (Grünwald et al. 2021).

Life History, Abundance, Activity, and Special Behaviors
Eleutherodactylus maculabialis is abundant in localities where it occurs. Specimens were collected in July from low-growing vegetation or rocks along roads (Grünwald et al. 2021).

Eleutherodactylus maculabialis has a short trill call type with a dominant frequency of 3.28 ± 532.5 kHz. Calls lasted 212.5 ± 20.55 ms, with a call interval of 19.87 ± 4.28 and a call rate of 5.49 ± 1.1 per second. The calls had a rise time of 18.5 ± 2.25 ms, and a pulse rate of 5.5 ± 0.25 (Grünwald et al. 2021).

The species can be found in sympatry with E. albolabris and E. nitidus (Grünwald et al. 2021).

Trends and Threats
At the time of the species description, E. maculabialis had no glaring or major threats. There is small-scale agriculture present throughout its range, but based on the current data this does not seem to largely impact this species as it continues to inhibit and survive in disturbed areas (Grünwald et al. 2021).

Comments

PHYLOGENETIC RELATIONSHIPS:

ETYMOLOGY:

The etymology for this species epithet comes from the combination of the Latin words “maculatus” and “labialis”, which mean “spotted” and “lip” respectively. This name references the brightly colored spots that appear on this species' upper lip (Grünwald et al. 2021).

References

Grünwald, C. I., Reyes-Velasco, J., Franz-Chavez, H., Morales-Flores, K. I., Ahumada-Carrillo, I. T., Rodrıguez, C. M., Jones, J. M. (2021). “Two new species of Eleutherodactylus (Anura: Eleutherodactylidae) from Southern Mexico, with comments on the taxonomy of related species and their advertisement calls.” Amphibian and Reptile Conservation 15, 1–35. [link]

Species Account Citation: AmphibiaWeb 2023 Eleutherodactylus maculabialis: English name: Spot-lipped Trilling Frog. Spanish name: Rana trinadora de labios manchados. <https://amphibiaweb.org/species/9323> University of California, Berkeley, CA, USA. Accessed Jun 5, 2023.

Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Jun 2023.

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