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According to this worldview, frogs of that age should look quite different to the frogs of today. This might be expected from a drastically changing environment and enormous timespan of >200 million years that should have seen considerable evolutionary change in a species so ecologically sensitive and unique. Therefore, the striking similarities have surprised him.
"The most astonishing thing to me about this study is that this animal is far more froglike than I would ever have expected from its age. Nothing this nonprimitive has ever been described from this age. It's just amazing."
No clear example of a transitional frog fossil has been found (as otherwise might be expected from the many imperfectly evolved specimens). Frogs are thought to have evolved from salamanders, and are interpreted likewise. Triadobatrachus is considered an 'excellent example of a transitional fossil', yet the most transitional characteristics of mention are several more vertebrae than in modern frogs and what might be considered a tail nib. This creature is clearly still a frog as seen by the majority of the fossil. These features do not provide a very compelling case for frog evolution, nor warrant the title of an 'excellent example of a transitional fossil'.
For the evolution of the frog to successfully occur, major developmental changes would have had to occur at precise moments to allow the transition into a frog a success. Any development occurring out of order would be fatal or severely handicap the individual. Each development would also need to be fully-functional, as the animal could not use any partially-developed organ
Gordon Rattray Taylor, former BBC science writer was quoted as saying "There are no intermediate forms between finned and limbed creatures in the fossil collections of the world." There is more recent confusion and disagreement among palaeontologists about certain characteristics in organisms supposedly related to frogs. A study on modern frog skin and that of a modern fish has found very little if any related characteristics between either skin, that might otherwise be expected if they were distantly related.
Considering how unique the frog is to every other vertebrate group, transitional fossils should abound from unsuccessful evolutionary attempts at producing a creature so specially adapted to its environment, like the permeability and sensitivity of the skin in which it uses to breathe.
When all assumptions and interpretations of the actual fossil evidence is removed, what remains are fossils that appear incredibly anatomically similar to modern frogs today. Is it possible that the few differences observed in the fossils represent variation within the one frog 'kind', of which there is such species diversity, both past and present?
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Armitage, M. and Sherwin, F. (2004) 'From fish to frog? Not by the skin'. TJ, 18, 69-73.
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*Whilst Wikipedia was utilised for components of the above text, other sites considered more trustworthy were also utilised. Nowhere else on this site has Wikipedia been used or cited.
South-east Queensland is a frog diversity hotspot, accommodating for three frog families and approximately a quarter of the 240 species known. These families are Hylidae - treefrogs, rocket frogs, water-holding frogs and collared-frogs. Family Myobactrachidae, or the Australian water frogs, include froglets, toadlets, many parental care species and the barred frogs. The Limnodynastidae Family (Australian ground frogs) include the marsh and burrowing frogs and some species endemic to rainforests.
The Greater Brisbane Region (which extends from Bribie Island, west to Mt Nebo and south to Mt Tamborine), is home to 41 native species of frog. Many of these species can be found outside of this region, so are not refined to this region alone. Two additional species have gone extinct, the southern dayfrog (Taudactylus diurnus) and the southern platypus frog (Rheobatrachus silus). This is a sad reminder that many frogs are threatened by habitat destruction and are consequently listed as endangered. The chytrid fungal disease (chytridiomycosis) is thought to have also been responsible for declining frog numbers, which ironically may have been assisted in spreading via people moving tadpoles around areas to try and establish frog populations on their property. Stream dwelling frogs are particularly vulnerable to this disease.
Frogs can be found at various altitudes and locations, with some species only occurring in particular habitats. Some will only appear when conditions are just right. Frogs and some other amphibians have a high level of adaptability, such as the green tree frog which seems to occur more often within suburbia than in the natural environment.
Get to know the frogs in your area by visiting the Frog ID Key and listen to their calls and see photos.
(2009) 'Wildlife of Greater Brisbane: A Queensland Museum Wild Guide', 2nd edition, Queensland Museum, Brisbane, Australia, pp.428.
Czechura, G. (2008) 'Frogs of South-East Queensland: A Queensland Museum Wild Guide', Queensland Museum, Brisbane, Australia, pp.68.
'In Australia, much work has been done on identifying species declines, factors that make a species more vulnerable to decline and identifying the causes of declines themselves (Hero and Morrison, 2004; Hero et al. 2005; Kriger and Hero, 2008; Collins and Storfer, 2003 (review of global impacts)). However, there is global consensus and evidence that frog declines cannot be put down to a single common factor (Hero and Morrison, 2004; summarized by Alford and Richards, 1999; Collins and Storfer, 2003). Anthropogenic causes of amphibian decline include habitat destruction and urbanisation (Gillespie, 2002; Lemckert, 1999), introduced fish species (Gillespie, 2001), introduced amphibians (Greenlees et al. 2007), increased UV-B radiation (Broomhall et al. 2000), river regulation (Wassens and Maher, 2011), cattle grazing, altered fire regimes, exotic animals and invasion of weeds, which are likely to have high significance on frogs (Hines et al. 2003). Weather conditions such as unusual rainfall and temperature patterns have been proposed in the past (Corn and Fogleman, 1984; Fellers and Drost, 1993) however there is little evidence to directly support this notion (Laurance, 1996).
'Frogs have also been drastically declining in virtually undisturbed habitat in Queensland and overseas (Alford and Richards, 1999; Hero and Morrison, 2004). Several lines of evidence suggest these declines were caused by a lethal waterborne pathogen (Laurance et al. 1996) and observations found that affected frog species exhibited similar characteristics as expected from a highly lethal virus (Laurance et al. 1996). This virus was subsequently described by Berger et al. (1998) as Batrachochytrium which was shown from several lines of evidence to cause chytridiomycosis, resulting in the deaths of amphibians in several countries (Berger et al. 1999). It is hypothesised that this pathogen could be spread via several vectors such as fish introductions, motor vehicles (Laurance et al. 1996) cattle and humans (Lips, 1998).'
If there is one take-home message from this it is that humans are the sole cause of global frog declines. Now we've got the responsibility of fixing it.
Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G. and Parkes, H. (1998) ‘Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America’. PNAS, 95, 9031-9036.
Berger, L., Speare, R. and Hyatt, A. (1999) ‘Chytrid fungi and amphibian declines: Overview, implications and future directions’. In Declines and Disappearances of Australian Frogs, 23-33. Campbell, A. (Ed). Environment Australia, Canberra.
Broomhall, S. D., Osborne, W. S. and Cunningham, R. B. (2000) ‘Comparative Effects of Ambient Ultraviolet-B Radiation on Two Sympatric Species of Australian Frogs’. Conservation Biology, 14, 420-427.
Collins, J. P. and Storfer, A. (2003) ‘Global amphibian declines: sorting the hypotheses’. Diversity and Distributions, 9, 89-98.
Corn, P. S. and Fogleman, J.C. (1984) ‘Extinction of Montane Populations of the Northern Leopard Frog (Rana pipiens) in Colorado’. Journal of Herpetology, 18, 147-152.
Fellers, G. M. and Drost, C. A. (1993) ‘Disappearance of the Cascades Frog Rana cascadae at the southern end of its range, California, USA’. Biological Conservation, 65, 177-181.
Gillespie, G. R. (2001) ‘The role of introduced trout in the decline of the spotted tree frog (Litoria Spenceri) in south-eastern Australia’. Biological Conservation, 100, 187-198.
Gillespie, G. R. (2002) ‘Impacts of sediment loads, tadpole density, and food type on the growth and development of tadpoles of the spotted tree frog Litoria spenceri: an in-stream experiment’. Biological Conservation, 106, 141-150.
Greenlees, M. J., Brown, G. P., Webb, J. K., Phillips, B. L. and Shine, R. (2007) ‘Do invasive cane toads (Chaunus marinus) compete with Australian frogs (Cyclorana australis)?’. Austral Ecology, 32, 900-907.
Hazel, D. (2003) ‘Frog ecology in modified landscapes: a review’. Wildlife Research, 30, 193-205.
Hero, J. M and Morrison, C. (2004) ‘Frog declines in Australia: global implications’. Herpetological Journal, 14, 175-186.
Hero, J. M., Williams, S .E. and Magnusson, W. E. (2005) ‘Ecological traits of declining amphibians in upland areas of eastern Australia’. Journal of Zoology London, 267, 221-232.
Houlahan, J. E., Findlay, C. S., Schmidt, B. R., Meyer, A. H. and Kuzmin, S. L. (2000) ‘Quantitative evidence for global amphibian population declines’. Nature, 404, 752-755.
Krigger, K. M. and Hero, J. M. (2008) ‘Altitudinal distribution of chytrid (Batrachochytrium dendrobatidis) infection in subtropical Australian frogs’. Austral Ecology, 33, 1022-1032.
Laurance, W. F. (1996) ‘Catastrophic declines of Australian rainforest frogs: is unusual weather responsible?’. Biological Conservation, 77, 203-212.
Lemckert, F. (1999) ‘Impacts of selective logging on frogs in a forested area of northern New South Wales’. Biological Conservation, 89, 321-328.
Lips, K. R. (1998) ‘Decline of a Tropical Montane Amphibian Fauna’. Conservation Biology, 12, 106-117.
Palmer, M., Bernhardt, E., Chornesky, E., Collins, S., Dobson, A., Duke, C,. Gold, B., Jacobson, R., Kingsland, S., Kranz, R., Mappin, M., Martinez, M. L., Micheli, F., Morse, J., Pace, M., Pascual, M., Palumbi, S., Reichman, O. J., Simons, S., Townsend, A. and Turner, M. (2004) ‘Ecology for a Crowded Planet’. Science, 304, 1251-1252.
Stuart, S. N., Chanson, J. S., Cox, N. A., Young, B. E., Rodrigues, A. S. L., Fischman, D. L. and Waller, R. W. (2004) ‘Status and Trends of Amphibian Declines and Extinctions Worldwide’. Science, 306, 1783-1786.
Wassens, S. and Maher, M. (2011) ‘River regulation influences the composition and distribution of inland frog communities’. River Research and Applications, 27, 238-246.