Diaglena spatulata is a relatively large shovel-head treefrog with a snout-vent length range of 61 - 87 mm in males and 75 - 101 mm in females. The head length is about a third of the snout-vent length and the head width is about a tenth of the snout-vent length. This species has a flat supralabial region in the shape of a shovel, with integumentary cranial co-ossification. Its snout is pointed, protruding beyond the lower jaw, with a distinguished nasal ridge extending to the tip, and laterally directed nostrils. The labial flange is narrow and finely serrate. It is upturned anteriorly toward the pre-orbital ridge, posterior to this, the labial shelf is reduced to a ridge. The loreal region is concave. The eyes are large and protrude anterolaterally. They have a bony postorbital ridge that extends from the eye socket to the posterior edge of the skull. The tympanum spans a length of about half the eye diameter and has a ridge that hangs over the upper edge. A low, smooth transverse bony ridge marks the end of the posterior edge of the skull (Duellman 2001).
Diaglena spatuala has slender upper arms and more robust forearms. The wrists have a distinct transverse dermal fold. They have a large flat, elliptical palmar tubercle. The fingers are moderately long and robust with large terminal digital disks. The disk on the third finger is equal to the diameter of the tympanum. The subarticular tubercles are relatively large and subconical, whereas the supernumerary tubercles are low, round, and indistinct. Webbing is absent between the first and second fingers and minimal between the third and fourth (Duellman 2001).
The legs are short and when adpressed at right angles to the body, the heel overlaps about one sixth of the shank. The tibiotarsal articulation extends to the shoulder when the leg is adpressed along the body. The length of the tibia and the foot length are both roughly one third the length of the snout-vent. There is a heavy tarsal fold that extends the full length of the tarsus. The disks on their long toes are slightly smaller than on the fingers. The toes are about two-thirds webbed. The webbing goes from the base of the penultimate phalanx of the first toe to the distal end of the antepenultimate of the second. The webbing continues from the middle of the penultimate phalanx of the second to the antepenultimate phalanx of the third (Duellman 2001).
The anal opening is at the level of the upper surfaces of the thighs and does not have an anal flap, however the area below is covered by moderately large tubercles. The dorsum is smooth or finely granular. The throat and ventral surfaces of the thighs are lightly granular, the skin on the rest of the venter is smooth (Duellman 1968, 2001).
Diaglena spatulata can be distinguished from other casque-headed hylids (such as Triprion petasatus, Aparasphenodon brunoi, and Hemiphractus fasiatus) by its large pre-nasal, expanded maxillaries, and odontoids on the palatines. Diaglena spatulata lack both spines on top of the head (present in Anotheca spinosa) and a dermal sphenethmoid, which is present in T. petasatus (Duellman 2001).
In life, the dorsal color ranges from yellow-tan, grey green, olive-gray, to green with yellow flecks. The body is lighter than the head, and the head is more heavily marked with dashes or reticulations. The venter is white, with brown flecks on the vocal sac in breeding males. The flanks are yellow, even in olive-gray bodied individuals. The patterning may be presented in small flecks, dashes, fine reticulations, bold reticulations, or reticulations and spots. Some of the darker flecks and dashes form indistinct transverse markings on the dorsal sides of the shanks and thighs. Color and pattern varies in southern and northern regions, with darker pigmentation in southern D. reticulatus. In preservative, the flanks are lighter. The dorsum is grayish brown to creamy tan, and brown markings may be visible (Duellman 2001).
Diaglena spatulata is composed of two subspecies: Diaglena spatulata spatulata in the north and Diaglena spatulata reticulate in the south. Diaglena s. reticulatus is also noticeably larger and has darker dorsal coloration than D. s. retculata. More specifically, D. s. spatulatais differentiated from D. s. reticulata by the former's flecked smooth olive-ray dorsum and narrower labial flange as opposed to D. s. retculata’s boldly reticulated brown and tan dorsal pattern with granular skin, and a broader labial flange (Duellman 2001). Flanges and crests also differ in relation to age and size (Duellman 1968, Taylor 1942).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Mexico
Diaglena spatulata is endemic to Mexico, it is distributed along the Pacific coastal lowlands in central Sinaloa and from Colima to the Isthmus of Tehuantepec, and in the Balsas Basin (Dulleman 2001). Certain records however indicated an absence of D. spatulata in Nayarit (Dullman 1968). They can be found from coastal lowlands in foothills, up to about 350 meters (Dulleman 2001). This species is arboreal and inhabits semi evergreen tropical forest, riparian vegetation, tropical dry forests, and desert scrub (Ordoñez-Ifarraguerri et al. 2017)
Life History, Abundance, Activity, and Special Behaviors
Diaglena spatulata is arboreal and often nocturnal (Garcia and Ceballos 1994). Breeding is seasonal, restricted to the rainy season in temporary ponds from June to November (Duellman 2001). Hardy and McDiarmid (1969) propose that cool weather, rain, and overcast sky can trigger reproductive behaviors.
The mating calls sound like a single low-pitched "braaa". This call has a range of 88 to 144 pulses per second, a duration range of 0.76 to 0.93 seconds, and a dominant frequency with a range of 1589 to 1869 cycles per second (Duellman 1968).
Diaglena spatulata is thought to be a dietary generalist. Ordoñez-Ifarraguerri et al. (2017) conducted a study in Jalisco, Mexico and found that this species’ diet was composed of 14 orders of prey. The most frequently consumed prey types were Araneae (spiders) and Orthoptera (grasshoppers, crickets, etc.). Diaglena spatulata use a sit-and-wait foraging technique (Ordoñez-Ifarraguerri et al. 2017).
This species demonstrated burrow guarding behavior in the laboratory by using its head as a protective barrier (Duellman and Klaas 1964).
Diaglena spatulata is a known host of the parasite Cosmocercella diaglenae in their large intestine (Mata-López et al. 2008). Of eight D. spatulata specimens collected from Jalisco and Yucatán states, Mexico, six carried the parasites with a total of 338 nematodes found.
Trends and Threats
According to IUCN, this species is of “Least Concern”. However, this evaluation needs to be reassessed to account for the high rate of habitat loss that has occurred along the Pacific coast of Mexico. Additionally, this species reproductive cycle revolves around water availability. Due to this, droughts, shifts in seasonality, and fires may impact populations (Santos-Barrera and Canseco-Márquez 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Climate change, increased UVB or increased sensitivity to it, etc.
The species authority is: Gunther, A. (1882). "Notice of a second species of Triprion." Annals and Magazine of Natural History 10:279.
Due to similar shovel-like supralabial region, Triprion petasatus and D. spatulata were originally considered members of the same genus, Triprion. However, Bayesian analysis of 10 nuclear and mitochondrial genes indicated that T. petasatus was more closely related to Anotheca spinosa, and together, they were sister to D. spatulata. Thus, the genus, Diaglena, was resurrected and three monotypic clades were recognized (Smith et al. 2007). Together, these three genera are the sister clade of Similisca (Faivovich et al. 2005, 2018).
The species epithet, “spatulata” references its broad labial flanges, derived from the Latin "spatula”, meaning “spoon” (Duellman 2001).
This species was first identified as Triprion spatulatus (Günther 1882), five years later it was assigned to a new genus as Diaglena spatulate (Cope 1887). Since then, proposal for both names have been made. Because of its unique morphological features and molecular sequence, AmphibiaWeb recognizes the name Diaglena spatulata. The species also has two recognized subspecies: Diaglena spatulata spatulata and Diaglena spatulata reticulatus (Duellman 1968).
Cope, E. D. (1887). ''Catalogue of batrachians and reptiles of Central America and Mexico.'' Bulletin of the United States National Museum , 32, 1-98.
Duellman, W. E. (1968). ''The Taxonomic Status of Some American Hylid Frogs.'' Herpetologica, 24(3), 194-209.
Duellman, W. E. (2001). The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Ithaca, New York.
Duellman, W.E., and Klaas, L.T. (1964). ''The biology of the hylid frog Triprion petasatus.'' Copeia, 1964(2), 308-321.
Faivovich, J., Haddad, C. F. B., Garcia, P. C. A., Frost, D. R., Campbell, J. A., Wheeler, W. C. (2005). ''Systematic review of the frog family Hylidae, with special reference to Hylinae: phylogenetic analysis and taxonomic revision.'' Bulletin of the American Museum of Natural History, (294), 1-240. [link]
Faivovich, J., Pereyra, M.O., Luna, M.C., Hertz, A., Blotto, B.L., Vásquez-Almazán, C.R., McCranie, J.R., Sánchez, D.A., Baêta, D., Araujo-Vieira, K., Köhler, G., Kubicki, B., Campbell, J.A., Frost, D.R., Wheeler, W.C., Haddad, C.F.B. (2018). ''On the monophyly and relationships of several genera of Hylini (Anura: Hylidae: Hylinae), with comments on recent taxonomic changes in Hylids.'' South American Journal of Herpetology, 13(1), 1-32. [link]
García, A., Ceballos, G. (1994). Guía de campo de los reptiles y anfibios de la costa de Jalisco, México. / Field guide to the reptiles and amphibians of the coast of Jalisco, Mexico. Fundación Ecológica de Cuixmala and Instituto de Biología, Universidad Nacional Autónoma de México., Mexico.
Günther, A. (1882). ''Notice of a second species of Triprion.'' Annals and Magazine of Natural History, 10, 279.
Hardy, L. M., and McDiarmid, Roy W. (1969). ''The amphibians and reptiles of Sinaloa, Mexico.'' University of Kansas Publications, Museum of Natural History, 18(3), 39-252.
Loc Barragán, J. (2014). ''Diaglena spatulata (Duck-bill Hylid Frog). Distribution Notes. Nayarit, Mexico.''
Mata-López, R., Guillén-Hernández, S., and León-Règagnon, V. (2008). ''A new species of Cosmocercella parasite of Diaglena spatulata and Triprion petasatus (Anura: Hylidae) from Mexico, based on new morphological information for the genus.'' Zootaxa,
Ordoñez-Ifarraguerri, A., Siliceo-Cantero, H., Suazo-Ortuño, I., Alvarado-Díaz, J. (2017). ''Does a frog change its diet along a successional forest gradient? The case of the shovel-nosed treefrog (Diaglena spatulata) in a tropical dry forest in western Mexico.'' Journal of Herpetology, 51, 411-416. [link]
Santos-Barrera, G., Canseco-Márquez, L. 2004. ''Diaglena spatulata.'' The IUCN Red List of Threatened Species 2004: e.T56052A11418082. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T56052A11418082.en.
Smith, S. A., De Oca, A. N., Reeder, T. W., and Wiens, J. J. (2007). ''A phylogenetic perspective on elevational species richness patterns in middle American treefrogs: Why so few species in lowland tropical rainforests?'' Evolution, 61, 1188-1207.
Taylor, E. H. (1942). ''The Frog Genus Diaglena, with a Description of a New Species.'' Univ. Kansas Sci. Bull, 28, 57-65.
Trueb, L. (1970). ''The evolutionary relationships of casque-headed treefrogs with co-ossified skulls (family Hylidae).'' University of Kansas Publications, Museum of Natural History, 18, 547-716.
Wiens, J. J., Fetzner, J. W., Parkinson, C. L., Reeder, T. W. (2005). ''Hylid frog phylogeny and sampling strategies for speciose clades.'' Systematic Biology , 54, 719-748.
Written by Katherine Agustina Martinez (xktamx AT gmail.com), University of Washington
First submitted 2019-10-14
Edited by Maxine Weber (2019-10-21)
Species Account Citation: AmphibiaWeb 2019 Diaglena spatulata: Mexican Shovel-headed Treefrog <http://amphibiaweb.org/species/1196> University of California, Berkeley, CA, USA. Accessed Jul 9, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 9 Jul 2020.
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