Development of the nidicolous tadpoles of Eupsophus emiliopugini (Anura: Cycloramphidae) until metamorphosis, with comments on systematic relationships of the species and its endotrophic developmental mode

Acta Zoologica

Volumn 92, Issue 1, 2011, Pages 27-45

  Vera Candioti, Maria Florencia ^a   Nuñez, José J ^b   Úbeda, Carmen ^c  

^a FUNDACIÓN MIGUEL LILLO   (Argentina)

^b UNIVERSIDAD AUSTRAL DE CHILE   (Chile)

^c LABORATORIO ECOTONO   (Argentina)

Author keywords

Alsodinae; Cranial morphology; Early development; Heterochrony

Indexed keywords

CRANIUM; FROG; HETEROCHRONY (ONTOGENY); LARVAL DEVELOPMENT; METAMORPHOSIS; TAXONOMY;

AMPHIBIA; ANURA; EUPSOPHUS; EUPSOPHUS EMILIOPUGINI;

EID: 77958548061     PISSN: 00017272     EISSN: 14636395     Source Type: Journal    
DOI: 10.1111/j.1463-6395.2010.00448.x     Document Type: Article

References (115)

1. Abravaya, J. P. and Jackson, J. F. 1978. Reproduction in Macrogenioglottus alipioi Carvalho (Anura: Leptodactylidae). Natural History Museum of Los Angeles County Contribution in Science 298: 1-9.
2. Alcalde, L. and Blotto, B. L. 2006. Chondrocranium, cranial muscles and buccopharyngeal morphology on tadpoles of the controversial leptodactylid frog Limnomedusa macroglossa (Anura: Leptodactylidae). Amphibia-Reptilia 27: 241-253.
3. Altig, R. 2006. Discussion of the origin and evolution of the oral apparatus of anuran tadpoles. Acta Herpetologica 2: 95-105.
4. Altig, R. 2007. A primer for the morphology of anuran tadpoles. Herpetological Conservation and Biology 2: 71-74.
5. Altig, R. and Johnston, G. 1989. Guilds of anuran larvae: relationships among developmental modes, morphologies and habits. Herpetological Monographs 2: 81-109.
6. Altig, R. and McDiarmid, R. W. 1999a. Body plan. Development and morphology. In McDiarmid, R. W. and Altig, R. (Eds): Tadpoles. The Biology of Anuran Larvae, pp. 24-51. University of Chicago Press, Chicago, IL.
7. Altig, R. and McDiarmid, R. W. 1999b. Diversity. Familial and generic characterization. In McDiarmid, R. W. and Altig, R. (Eds): Tadpoles. The Biology of Anuran Larvae, pp. 295-337. University of Chicago Press, Chicago, IL.
8. Bininda-Emonds, O. R. P., Jeffery, J. E., Sánchez-Villagra, M. R., Hanken, J., Colbert, M., Pieau, C., et al. 2007. Forelimb-hindlimb developmental timing changes across tetrapod phylogeny. BMC Evolutionary Biology 7: 182.
9. Böck, J. W. and Shear, C. R. 1972. A staining method for gross dissection of vertebrate muscles. Anatomischer Anzeiger 130: 222-227.
10. Buchholz, D. R. and Hayes, T. B. 2002. Evolutionary patterns of diversity in Spadefoot Toad metamorphosis (Anura: Pelobatidae). Copeia 2002: 180-189.
11. Caldwell, J. P. and Lima, A. P. 2003. A new species of Colostethus (Anura: Dendrobatidae) with a nidicolous tadpole. Herpetologica 59: 219-234.
12. Callery, E. M., Fang, H. and Elinson, R. P. 2001. Frogs without polliwogs: evolution of anuran direct development. Bioessays 23: 233-241.
13. Caramaschi, U. and Sazima, I. 1984. Uma nuova espécies de Thoropa da Serra do Cipó, Minas Gerais, Brasil (Amphibia, Leptodactylidae). Revista Brasileira de Zoologia 2: 139-146.
14. Cárdenas-Rojas, D. R., Veloso, A. and De Sá, R. O. 2007a. The tadpole of Eupsophus queulensis (Anura, Cycloramphidae). Alytes 25: 45-54.
15. Cárdenas-Rojas, D. R., Rabanal, F. and Formas, J. R. 2007b. The tadpole of Hylorina sylvatica (Anura: Cycloramphidae) in Southern Chile. Zootaxa 1580: 51-62.
16. Cei, J. M. and Capurro, L. F. 1958. Biología y desarrollo de Eupsophus taeniatus Girard. Investigaciones Zoológicas Chilenas 4: 150-182.
17. Clarke, B. T. 1983. A morphological re-examination of the frog genus Nannophrys (Anura: Ranidae) with comments on its biology, distribution and relationships. Zoological Journal of the Linnean Society 79: 377-398.
18. Correa, C., Veloso, A., Iturra, P. and Mendez, M. A. 2006. Relaciones filogenéticas de los leptodactílidos chilenos: una aproximación molecular basada en los genes mitocondriales 12S y 16S. Revista Chilena de Historia Natural 79: 435-450.
19. De la Riva, I. 1995. A new reproductive mode for the genus Adenomera (Amophibia : Anura : Leptodactylidae): taxonomic implications for certain Bolivian and Paraguayan populations. Studies on Neotropical Fauna and Environment 30: 15-29.
20. Desnitskiy, A. G. 2004. Evolutionary transformations of ontogenesis in anuran amphibians. Russian Journal of Developmental Biology 35: 125-130.
21. Díaz, N. F. 1986. Biosistemática de los Leptodactylidae chilenos. Anales del Museo de Historia Natural de Valparaíso (Chile) 17: 65-85.
22. Díaz, N. F. and Valencia, J. 1985. Larval morphology and phenetic relationships of the Chilean Alsodes, Telmatobius, Caudiverbera and Insuetophrynus (Anura: Leptodactylidae). Copeia 1985: 175-181.
23. Drewes, R. C., Altig, R. and Howell, K. M. 1989. Tadpoles of three frog species endemic to the forests of the Eastern Arc Mountains, Tanzania. Amphibia-Reptilia 10: 435-443.
24. Duellman, W. E. and Gray, P. 1983. Developmental biology and systematics of the egg-brooding hylid frogs, genera Flectonotus and Fritziana. Herpetologica 39: 333-359.
25. Echeverría, D. D. and Filipello, A. M. 1994. Consideraciones acerca de la fórmula dentaria y del aparato bucal de las larvas de Odontophrynus occidentalis (Berg, 1896) (Anura, Leptodactylidae). Physis Sección B 49: 59-63.
26. Echeverría, D. D. and Montanelli, S. B. 1995. Acerca del aparato bucal y de las fórmulas dentarias en Odontophrynus americanus (Duméril y Bibron, 1841) (Anura, Leptodactylidae). Physis Sección B 50: 37-43.
27. Echeverría, D. D., Alonso, C. A., Pillado, M. S. and Úbeda, C. 2001. Microanatomía del aparato bucal y cavidad bucofaríngea de la larva de Alsodes gargola Gallardo, 1970 (Leptodactylidae, Telmatobiinae). Alytes 18: 187-200.
28. Elinson, R. P. 2001. Direct development: an alternative way to make a frog. Genesis 29: 91-95.
29. Eterovick, P. C. and Sazima, I. 1998. New species of Proceratophrys (Anura: Leptodactylidae) from Southeastern Brazil. Copeia 1998: 159-164.
30. Fabrezi, M. 1988. Metamorfosis en Pleurodema borellii (Anura: Leptodactylidae). Estudio del neurocráneo, esqueleto visceral y musculatura asociada. Magister Thesis, Universidad Nacional de Tucumán, Tucumán, Argentina.
31. Fabrezi, M. and Goldberg, J. 2009. Heterochrony during skeletal development of Pseudis platensis (Anura, Hylidae) and the early offset of skeleton development and growth. Journal of Morphology 270: 205-220.
32. Fabrezi, M. and Quinzio, S. I. 2008. Morphological evolution in Ceratophryinae frogs (Anura, Neobatrachia): the effects of heterochronic changes during larval development and metamorphosis. Zoological Journal of the Linnean Society 154: 752-780.
33. Fabrezi, M. and Vera, R. 1997. Caracterización morfológica de larvas de anuros del Noroeste Argentino. Cuadernos de Herpetología 11: 37-49.
34. Fabrezi, M., Quinzio, S. I. and Goldberg, J. 2009a. Giant tadpole and delayed metamorphosis of Pseudis platensis Gallardo, 1961 (Anura, Hylidae). Journal of Herpetology 43: 228-243.
35. Fabrezi, M., Quinzio, S. I. and Goldberg, J. 2009b. The ontogeny of Pseudis platensis (Anura, Hylidae): heterochrony and the effects of larval development on the postmetamorphic life. Journal of Morphology. doi:
36. Fernández de la Reguera, P. A. 1987. Identifying species in the Chilean frogs by principal component analysis. Herpetologica 43: 173-177.
37. Formas, J. R. 1989a. A new species of Eupsophus (Amphibia: Anura: Leptodactylidae) from southern Chile. Proceedings of the Biological Society of Washington 102: 568-576.
38. Formas, J. R. 1989b. The tadpole of Eupsophus calcaratus in southern Chile. Journal of Herpetology 23: 195-197.
39. Formas, J. R. 1992a. El cariotipo de la rana chilena Eupsophus contulmoensis (Anura: Leptodactylidae), con comentarios sobre la evolución cariológica del género Eupsophus. Boletín de la Sociedad de Biología de Concepción (Chile) 63: 77-82.
40. Formas, J. R. 1992b. The tadpole of Eupsophus vertebralis (Anura: Leptodactylidae). Herpetologica 48: 115-119.
41. Formas, J. R. and Brieva, L. 1994. Advertisement calls and relationships of Chilean frogs Eupsophus contulmoensis and E. insularis (Amphibia: Anura: Leptodactylidae). Proceedings of the Biological Society of Washington 107: 391-397.
42. Formas, J. R. and Brieva, L. 2004. The tadpoles of Alsodes vanzolinii and A. verrucosus (Anura: Leptodactylidae) with descriptions of their internal oral and chondrocranial morphology. Amphibia-Reptilia 25: 151-164.
43. Formas, J. R. and Pugín, E. 1971. Reproducción y desarrollo de Batrachyla antartandica (Barrio) (Anura, Leptodactylidae). Boletín del Museo Nacional de Historia Natural (Chile) 32: 201-213.
44. Formas, J. R. and Pugín, E. 1978. Tadpoles of Eupsophus roseus and Bufo variegatus (Amphibia, Anura) in southern Chile. Journal of Herpetology 12: 243-246.
45. Formas, J. R. and Vera, M. A. 1980. Reproductive patterns of Eupsophus roseus and E. vittatus. Journal of Herpetology 14: 11-14.
46. Formas, J. R., Vera, M. I. and Lacrampe, S. 1983. Allozymic and morphological differentiation in the South American frogs genus Eupsophus. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 75: 475-478.
47. Frost, D. R. 2009. Amphibian Species of the World: An Online Reference Version 5.3 (12 February, 2009). American Museum of Natural History, New York. Available at: (accessed December 2009).
48. Frost, D. R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C. F. B., et al. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1-370.
49. Giannini, N. P. 2003. Canonical phylogenetic ordination. Systematic Biology 52: 684-695.
50. Giaretta, A. A., Bernarde, P. S. and Kokubum, M. N. C. 2000. A new species of Proceratophrys (Anura: Leptodactylidae) from the Amazon rain forest. Journal of Herpetology 34: 173-178.
51. Gosner, K. L. 1960. A simplified table for staging anuran embryos and larvae, with notes on identification. Herpetologica 16: 183-190.
52. Grosjean, S. 2001. The tadpole of Leptobrachium (Vibrissaphora) echinatum (Amphibia, Anura, Megophryidae). Zoosystema 23: 143-156.
53. Grosjean, S. 2005. The choice of external morphological characters and developmental stages for tadpoles-based anuran taxonomy: a case study in Rana (Sylvirana) nigrovittata (Blyth, 1855) (Amphibia, Anura, Ranidae). Contributions to Zoology 74: 61-76.
54. Haas, A. 1996a. Non-feeding and feeding tadpoles in hemiphractine frogs: larval head morphology, heterochrony, and systematics of Flectonotus goeldii (Amphibia: Anura: Hylidae). Journal of Zoological Systematics and Evolutionary Research 34: 163-171.
55. Haas, A. 1996b. Das larvale Cranium von Gastrotheca riobambae und seine Metamorphose (Amphibia, Anura, Hylidae). Verhandlungen des Naturwissenschaftlichen Vereins Hamburg 36: 33-162.
56. Haas, A. 2001. Mandibular arches musculature of anuran tadpoles, with comments on homologies of amphibian jaw muscles. Journal of Morphology 247: 1-33.
57. Haas, A. 2003. Phylogeny of frogs as inferred from primarily larval characters (Amphibia: Anura). Cladistics 19: 23-89.
58. Hall, J. A., Larsen, J. H. Jr and Fitzner, R. E. 1997. Postembryonic ontogeny of the Spadefoot Toad, Scaphiopus intermontanus (Anura: Pelobatidae): external morphology. Herpetological Monographs 11: 124-178.
59. Hanken, J., Klymkowsky, M. W., Summers, C. H., Seufert, D. W. and Ingebrigtsen, N. 1992. Cranial ontogeny in the direct-developing frog, Eleutherodactylus coqui (Anura: Leptodactylidae), analyzed using whole mount immunohistochemistry. Journal of Morphology 211: 95-118.
60. Hanken, J., Klymkowsky, M. W., Alley, K. and Jennings, D. 1997. Jaw muscle development as evidence for embryonic repatterning in direct-developing frogs. Proceedings of the Royal Society B: Biological Sciences 264: 1349-1354.
61. Heyer, R. 1969. The adaptive ecology of the species groups of the genus Leptodactylus (Amphibia, Leptodactylidae). Evolution 23: 421-428.
62. Heyer, R. 1975. A preliminary analysis of the intergeneric relationships of the frog family Leptodactylidae. Smithsonian Contributions to Zoology 199: 1-55.
63. Heyer, R. 1983a. Variation and systematics of frogs of the genus Cycloramphus (Amphibia, Leptodactylidae). Arquivos de Zoologia 30: 235-339.
64. Heyer, R. 1983b. Notes on the frog genus Cycloramphus (Amphibia: Leptodactylidae), with descriptions on two new species. Proceedings of the Biological Society of Washington 96: 548-559.
65. Heyer, W. R. and Crombie, R. I. 1979. Natural history notes on Craspedoglossa stejnegeri and Thoropa petropolitana (Amphibia: Salientia, Leptodactylidae). Journal of the Washington Academy of Sciences 69: 17-20.
66. Heyer, R. and Silverstone, P. A. 1969. The larva of the frog Leptodactylus hylaedactylus (Leptodactylidae). Fieldiana Zoology 51: 141-145.
67. Inger, R. 1960. Notes on toads of the genus Pelophryne. Fieldiana Zoologia 39: 415-418.
68. Juncá, F. A., Altig, R. and Gascon, C. 1994. Breeding biology of Colostethus stepheni, a dendrobatid frog with a nontransported nidicolous tadpole. Copeia 1994: 747-750.
69. Kaiser, H. and Altig, R. 1994. The atypical tadpole of the dendrobatid frog, Colostethus chalcopis, from Martinique, French Antilles. Journal of Herpetology 28: 374-378.
70. Kerney, R., Meegaskumbura, M., Manamendra-Arachchi, K. and Hanken, J. 2007. Cranial ontogeny in Philautus silus (Anura: Ranidae: Rhacophorinae) reveals few similarities with other direct-developing anurans. Journal of Morphology 268: 715-725.
71. Kokubum, M. N. C. and Giaretta, A. A. 2005. Reproductive ecology and behaviour of a species of Adenomera (Anura, Leptodactylinae) with endotrophic tadpoles: systematics implications. Journal of Natural History 39: 1745-1758.
72. Krügel, P. and Richter, S. 1995. Syncope antenori-a bromeliad breeding frog with free-swimming, non-feeding tadpoles (Anuran: Microhylidae). Copeia 1995: 955-963.
73. Larson, P. M. 2005. Ontogeny, phylogeny, and morphology in anuran larvae: morphometric analysis of cranial development and evolution in Rana tadpoles (Anura: Ranidae). Journal of Morphology 264: 34-52.
74. Larson, P. M. 2008. The chondrocrania of North American Rana larvae (Anura: Ranidae): a morphological comparison. Acta Zoologica 89: 279-288.
75. Larson, P. M. and De Sá, R. O. 1998. Chondrocranial morphology of Leptodactylus larvae (Leptodactylidae: Leptodactylinae): its utility in phylogenetic reconstruction. Journal of Morphology 238: 287-306.
76. Lavilla, E. O. 1987. La larva de Rhinoderma darwinii D & B (Anura: Rhinodermatidae). Acta Zoologica Lilloana 39: 81-88.
77. Lavilla, E. O. 1991. Condrocráneo y esqueleto visceral en larvas de Cycloramphus stejnegeri (Leptodactylidae). Amphibia-Reptilia 12: 33-38.
78. Lavilla, E. O. 1992. Estructura del condrocráneo y esqueleto visceral de larvas de Alsodes barrioi (Anura: Leptodactylidae). Acta Zoologica Lilloana 42: 13-18.
79. Lavilla, E. O. and Scrocchi, G. J. 1991. Aportes a la herpetología del Chaco Argentino. II - Nuevos datos sobre Odontophrynus lavillai Cei, 1985 (Anura: Leptodactylidae). Acta Zoologica Lilloana 40: 33-37.
80. Leong, T. M. and Teo, S. C. 2009. Endotrophic tadpoles of the Saint Andrew's Cross toadlet, Pelophryne signata (Amphibia: Anura; Bufonidae) in Singapore. Nature in Singapore 2: 21-25.
81. Lutz, B. 1944. Biologia e taxonomia de Zachaenus parvulus. Boletim do Museu Nacional do Rio de Janeiro, Zoologia 17: 1-66.
82. McDiarmid, R. 1971. Comparative morphology and evolution of frogs of the neotropical genera Atelopus, Dendrophryniscus, Melanophryniscus, and Oreophrynella. Bulletin of the Los Angeles County, Museum of Natural History, Science 12: 1-66.
83. Nixon, K. C. 1999. Winclada (BETA) Ver. 0.9.9. Published by the Author, Ithaca, NY.
84. Nodzenski, E. and Inger, R. F. 1990. Uncoupling of related structural changes in metamorphosing torrent-dwelling tadpoles. Copeia 1990: 1047-1054.
85. Nuñez, J. J. 2004. Taxonomía y sistemática de las ranas del género Eupsophus (Anura: Leptodactylidae). PhD Thesis, Universidad Austral de Chile, Valdivia, Chile.
86. Nuñez, J. J. and Úbeda, C. 2009. The tadpole of Eupsophus nahuelbutensis (Anura: Neobatrachia): external morphology, chondrocranium, and comments on its natural history. Zootaxa 2126: 58-68.
87. Palavecino, P. M. 1999. Musculatura asociada al primer y segundo arco visceral de algunos anuros leptodactílidos. Cuadernos de Herpetología 13: 37-46.
88. Peixoto, O. L. 1981. Notas sobre o girino de Crossodactylodes pintoi Cochran (Amphibia, Anura, Leptodactylidae). Revista Brasileira de Biologia 41: 339-341.
89. Perotti, M. G. 2001. Skeletal development of Leptodactylus chaquensis (Anura: Leptodactylidae). Herpetologica 57: 318-335.
90. Púgener, L. A. and Maglia, A. M. 1997. Osteology and skeletal development of Discoglossus sardus (Anura: Discoglossidae). Journal of Morphology 233: 267-286.
91. Púgener, L. A., Maglia, A. M. and Trueb, L. 2003. Revisiting the contribution of larval characters to an analysis of phylogenetic relationships of basal anurans. Zoological Journal of the Linnean Society 139: 129-155.
92. Rabanal, F. E. and Formas, J. R. 2009. Complementary diagnosis of the genus Insuetophrynus (Anura, Cycloramphidae) based on larval characters. Zootaxa 2116: 59-67.
93. Rossa-Feres, D. C. and Jim, J. 1996. Tadpole of Odontophrynus moratoi (Anura, Leptodactylidae). Journal of Herpetology 30: 536-539.
94. De Sá, R. O. 1988. Chondrocranium and ossification sequence of Hyla lanciformis. Journal of Morphology 195: 345-355.
95. De Sá, R. O. and Langone, J. 2002. The tadpole of Proceratophrys avelinoi (Anura Leptodactylidae). Journal of Herpetology 36: 490-494.
96. Sheil, C. A. 1999. Osteology and skeletal development of Pyxicephalus adspersus (Anura: Ranidae: Raninae). Journal of Morphology 240: 49-75.
97. Sheil, C. A. and Alamillo, H. 2005. Osteology and skeletal development of Phyllomedusa vaillanti (Anura: Hylidae: Phyllomedusinae) and a comparison of this arboreal species with a terrestrial member of the genus. Journal of Morphology 265: 343-368.
98. Starrett, P. 1968. The Phylogenetic Significance of the Jaw Musculature in Anuran Amphibians. PhD Thesis, University of Michigan, Michigan, USA.
99. Thibaudeau, G. and Altig, R. 1999. Endotrophic anurans. In McDiarmid, R. W. and Altig, R. (Eds): Tadpoles. The Biology of Anuran Larvae, pp. 170-188. University of Chicago Press, Chicago, IL.
100. Trueb, L. 1985. A summary of osteocranial development in anurans with notes on the sequence of cranial ossification in Rhinophrynus dorsalis (Anura: Pipoidea: Rhinophrynidae). South African Journal of Science 81: 181-185.
101. Trueb, L., Púgener, L. A. and Maglia, A. M. 2000. Ontogeny of the bizarre: an osteological description of Pipa pipa (Anura: Pipidae), with an account of skeletal development in the species. Journal of Morphology 243: 75-104.
102. Úbeda, C. A. and Nuñez, J. J. 2006. New parental care behaviours in two telmatobiine genera from temperate Patagonian forests: Batrachyla and Eupsophus (Anura: Leptodactylidae). Amphibia-Reptilia 27: 441-444.
103. Veloso, A., Celis-Diez, J. L., Guerrero, P. C., Méndez, M. A., Iturra, P. and Simonetti, J. A. 2005. Description of a new Eupsophus species (Amphibia, Leptodactylidae) from the remnants of Maulino Forest, Central Chile. Herpetological Journal 15: 159-165.
104. Vera Candioti, M. F. 2007. Anatomy of anuran tadpoles from lentic water bodies: systematic relevance and correlation with feeding habits. Zootaxa 1600: 1-175.
105. Vera Candioti, M. F. 2008. Larval anatomy of Andean tadpoles of Telmatobius (Anura: Ceratophryidae) from Northwestern Argentina. Zootaxa 1938: 40-60.
106. Vera Candioti, M. F., Úbeda, C. and Lavilla, E. O. 2005. Morphology and metamorphosis of Eupsophus calcaratus tadpoles (Anura: Leptodactylidae). Journal of Morphology 264: 161-177.
107. Wassersug, R. J. 1976a. A procedure for differential staining of cartilage and bone in whole formalin-fixed vertebrates. Stain Technology 51: 131-134.
108. Wassersug, R. J. 1976b. Oral morphology of anuran larvae: terminology and general description. Occasional Papers of the Museum of Natural History, University of Kansas 48: 1-23.
109. Wassersug, R. J. and Duellman, W. E. 1984. Oral structures and their development in egg-brooding hylid frog embryos and larvae: evolutionary and ecological implications. Journal of Morphology 182: 1-37.
110. Wassersug, R. J. and Heyer, W. R. 1983. Morphological correlates of subaerial existence in leptodactylid tadpoles associated with flowing water. Canadian Journal of Zoology 61: 761-769.
111. Wassersug, R. J. and Heyer, W. R. 1988. A survey of internal oral features of Leptodactyloid larvae (Amphibia: Anura). Smithsonian Contribution to Zoology 457: 1-99.
112. Wiens, J. J. 1989. Ontogeny of the skeleton of Spea bombifrons (Anura: Pelobatidae). Journal of Morphology 202: 29-51.
113. Wild, E. R. 1997. Description of the adult skeleton and developmental osteology of the hyperossified Horned Frog, Ceratophrys cornuta (Anura: Leptodactylidae). Journal of Morphology 232: 169-206.
114. Wild, E. R. 1999. Description of the chondrocranium and osteogenesis of the Chacoan Burrowing Frog, Chacophrys pierotti (Anura: Leptodactylidae). Journal of Morphology 242: 229-246.
115. Yeh, J. 2002. The evolution of development: two portraits of skull ossification in pipoid frogs. Evolution 56: 2484-2498.