Paradox FrogsDavid Cannatella
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The pseudids include two genera of aquatic frogs from The Magdalena Valley of Colombia and tropical lowlands of South America east of the Andes. Pseudis paradoxa is best known because its immense tadpoles (250-300 mm) metamorphose into relatively moderate-sized frogs. The two species of Lysapsus are much smaller than the two species of Pseudis.
Pseudids have an additional bony element in the fingers and toes between the penultimate and terminal phalanx. This element may increase the functional surface area of the highly webbed foot. Pseudis paradoxa float among vegetation in shallow ponds and roadside ditches, much like Rana catesbeiana in North America.
There are no fossils. Were it not for the distinctive intercalary elements, pseudids would be considered leptodactylids. The intercalary phalangeal elements are very different than those of arboreal frogs such as hylids and centrolenids.
Pseudidae was defined by Ford and Cannatella (1993) as the node-based name for the common ancestor of Lysapsus and Pseudis. Pseudids are generally characterized as having bony intercalary elements (Lynch, 1973), but Ford and Cannatella (1993) pointed out that these elements are distinctive in being elongate and perichondrially ossified. They considered these intercalary elements to be a synapomorphy of Pseudidae. The elongate nature of the intercalary element is unique among frogs, and suggests a role in increasing the length of the digit and area of the webbing in these highly aquatic frogs.
Lynch (1973) and Duellman and Trueb (1986:character J) used the presence of intercalary elements to unite Hylidae, Centrolenidae and Pseudidae into a clade. Intercalary elements are also known in Hyperoliidae and Rhacophoridae, as well as mantelline ranids and phrynomerine microhylids. The tree presented by Duellman and Trueb (1986:Fig. 17-3) has an equally parsimonious solution that would require convergent evolution of a firmisternal girdle (character C1) if lack of homoplasy in the intercalary element (character J1) is favored. In a subtree Duellman and Trueb (1986:Fig. 17-4) used the presence of intercalary elements to unite mantellines, hyperoliids, and rhacophorids, but not phrynomerines. This tree also has an equally parsimonious alternative that would unite phrynomerines with the aforementioned clade, but requires homoplasy in the Type 2 larva (character O2').
Ford's (1989b) study of dendrobatid relationships did not include centrolenids or pseudids. Ford and Cannatella continued the recognition of the clade consisting of Hylidae, Pseudidae, and Centrolenidae, which is diagnosed by the presence of intercalary elements., but did not name it. Hay et al. (1995) found that pseudids, hylids and centrolenids (each represented by one species) not to be a clade, although the latter two were sister-taxa, and all three were part of the Neobatrachia.
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University of Texas, Austin, Texas, USA
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Page copyright © 1995 David Cannatella
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Citing this page:
Cannatella, David. 1995. Pseudidae. Paradox Frogs. Version 01 January 1995 (under construction). http://tolweb.org/Pseudidae/16951/1995.01.01 in The Tree of Life Web Project, http://tolweb.org/