Hylids (treefrogs) are one of the largest families of frogs. There are about 37-39 genera. These are arranged in four subfamilies, the first three of which are distinctive: Pelodryadinae, Phyllomedusinae, Hemiphractinae, and Hylinae.
Among the most bizarre hyline frogs are certain casque-headed genera, such as Triprion and Trachycephalus, in which the skull bones are elaborated into a solid helmet. Certain casque-headed species use their bony heads to block the entrances to their burrows and reduce evaporative water loss.
Evolution and Systematics
Discussion of Phylogenetic Relationships
The name Hylidae was defined by Ford and Cannatella (1993) as node-based name for the most recent ancestor of Hemiphractinae, Phyllomedusinae, Pelodryadinae, and Hylinae, and all of its descendants. The single synapomorphy known is claw-shaped terminal phalanges; these are also found in some hyperoliids (see below). Another commonly mentioned diagnostic feature of hylids is the presence of intercalary elements, but these are also present in centrolenids and pseudids, among the non-ranoid neobatrachians (see below). Savage (1973), Laurent (1979, 1986) and Dubois (1983, 1984) recognized the Australian hylids (Pelodryadinae) as a distinct family.
The monophyly of Hylidae is questionable if Allophryne ruthveni is included. See the account under Allophryne ruthveni.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimen Records: 6088
Specimens with Sequences: 7496
Specimens with Barcodes: 4628
Species With Barcodes: 458
Public Records: 661
Public Species: 86
Public BINs: 99
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The Hylidae are a wide-ranging family of frogs commonly referred to as "tree frogs and their allies". However, the hylids include a diversity of frog species, many of which do not live in trees, but are terrestrial or semiaquatic.
Most hylids show adaptations suitable for an arboreal lifestyle, including forward-facing eyes providing binocular vision, and adhesive pads on the fingers and toes. In the nonarboreal species, these features may be greatly reduced, or absent. The Cyclorana species are burrowing frogs that spend much of their lives underground.
Hylids mostly feed on insects and other invertebrates, but some larger species can feed on small vertebrates.
Hylids lay their eggs in a range of different locations, depending on species. Many use ponds, or puddles that collect in the holes of their trees, while others use bromeliads or other water-holding plants. Other species lay their eggs on the leaves of vegetation hanging over water, allowing the tadpoles to drop into the pond when they hatch.
A few species use fast-flowing streams, attaching the eggs firmly to the substrate. The tadpoles of these species have suckers enabling them to hold onto rocks after they hatch. Another unusual adaptation is found in some South American hylids, which brood the eggs on the back of the female. The tadpoles of most hylid species have laterally placed eyes, and broad tails with narrow, filamentous tips.
The European tree frog, Hyla arborea, is common in the middle and south of Europe, and ranges into Asia and North Africa. The species becomes very noisy on the approach of rain and is sometimes kept in confinement as a kind of barometer.
North America has many species of the Hylidae family, including the Gray tree frog (Hyla versicolor) and the American green tree frog (H. cinerea). The spring peeper (Pseudacris crucifer) is also widespread in the eastern United States and is commonly heard on summer and spring evenings.
"Tree frog" is a popular name for several of the Hylidae. H. versicolor is the changeable tree frog, Trachycephalus lichenatus is the lichened tree frog, and Trachycephalus marmoratus is the marbled tree frog. However, the name "treefrog" is not unique to this family, also being used for many species of the Rhacophoridae.
The Hylidae family is divided into these subfamilies and genera:
- This article incorporates text from the Collier's New Encyclopedia (1921).
- "Amero-Australian Treefrogs (Hylidae)". William E. Duellman. Grzimek's Animal Life Encyclopedia. Ed. Michael Hutchins, Arthur V. Evans, Jerome A. Jackson, Devra G. Kleiman, James B. Murphy, Dennis A. Thoney, et al. Vol. 6: Amphibians. 2nd ed. Detroit: Gale, 2004. p225-243.
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