This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
In the previous article, we looked at parsley frogs or pelodytids – a small and conservative lineage within the anuran clade Pelobatoidea (also known as Anomocoela, and commonly as the spadefoot toads). Parsley frogs are very nice, but they’re dull compared to certain other pelobatoid lineages, especially the (sometimes) rather spectacular megophryids (or megophryines) of SE Asia. And it’s megophryids we’ll be looking at here. Look at this photo (by o.leillinger@web.de) - they're awesome...
By far the best known megophryid is Megophrys, a relatively familiar anuran genus (occurring across SE Asia, the islands of the Sunda Shelf, and the Philippines) to those who frequent the literature on tropical amphibians. And the best known of its many species is the Malayan horned frog, Bornean horned frog or Long-nosed horned frog M. nasuta of Malaysia, Sumatra and Borneo. It's reasonably large (SVL 70-125 mm), stocky, cryptically camouflaged to resemble dead leaves in colour and shape, and possesses a long, pointed snout and elongate supraorbital horns. Two pairs of longitudinal ridges run along its dorsal surface and help enhance its ‘leaf litter’ camouflage. It inhabits rainforests that grow on all sorts of terrain, from those on flat regions at sea level to those on steep hillsides 1.6 km high.
M. nasuta is the very first megophryid I ever learnt about, all thanks to its appearance in the 1980s PG Tips tea-card series Incredible Creatures. As I’ve said on Tet Zoo before, I was strongly influenced at a young age by the educational cards that came inside boxes of PG Tips tea. Some of you will know exactly what I’m talking about; my apologies to the rest of you. Anyway, here’s the Incredible Creatures card that featured Megophrys. I always admired the artwork on these cards and recognised the style as being distinctive. Turns out that the entire set was illustrated by our old friend Richard Orr...
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Moving on... I just said that there are “many species” of Megophrys. How many is “many”? I thought it was about five. Turns out that there are almost 60 species in this large and successful group. Almost 60... and all but 21 of these have been named since 1990. The most recently named (as of the time of writing) are M. acuta Wang et al., 2014, M. cheni (Wang & Liu, 2014), M. lini (Wang & Yang, 2014), and M. obesa Wang et al., 2014, all of which are Chinese. As you might have gathered from the fact that four new species were named in 2014 alone, we’re in something of a golden age as goes the naming of new living frog species. But then you might know this already. I’ve certainly mentioned it a few times at Tet Zoo.
It should be said now that the status of Megophrys is currently something of a confused issue given that there has been considerable uncertainty and disagreement as to how many genera should be recognised within this group. Frost et al. (2006) proposed that, in addition to Megophrys, the horned spadefoot toad clade contains Atympanophrys, Brachytarsophrys, Ophryophryne and Xenophrys (other generic names have been proposed for these frogs as well, but I’d like to avoid writing hundreds of words about historical taxonomy here if it can be avoided).
The last of those genera – that is, Xenophrys – is conventionally regarded as the most speciose one. Indeed, some of those 2014 species I just mentioned above were originally named as new members of Xenophrys (Wang et al. 2014). Some authors have interpreted Xenophrys and Ophryophryne as so distinct relative to Megophrys that they should warrant their own ‘tribe’ (Xenophryini) (Delorme et al. 2006).
Other authors, meanwhile, have implied that Xenophrys is paraphyletic with respect to Atympanophrys, Brachytarsophrys and Ophryophryne at least (Li et al. 2011, Wang et al. 2012). And this is problematic given that some of those taxa are meant to be members of wholly different lineages: Brachytarsophrys, for example, was regarded by Delorme et al. (2006) as a member of the Megophrys ‘tribe’ Megophryini. Without splitting Xenophrys into a plethora of new, genus-level taxa, the most sensible course of action is to collapse the many species concerned into a single taxon, and the idea that’s currently most widely preferred is to give up on Xenophrys and sink everything into Megophrys (Frost 2014). Oh well.
Are the other Megophrys species similar to M. nasuta? They tend to be somewhat smaller (with SVLs of 40-110 mm or so; females are larger), and with far less prominent supraorbital horns than M. nasuta and a blunt-tipped nose, not a pointed one. All of these frogs frequent leaf litter (the common names ‘litter frogs’ and leaf-litter frogs’ are sometimes used for them), as you might have guessed from their specialised appearance. The tympanum is sometimes partially covered by skin flaps on the side of the face. The image below is from Wang et al. (2014).
Megophrys frogs breed in streams with weak currents; the eggs are laid in shallow pools at the edges of streams and the tadpoles tend to frequent side channels or riffles. They also hide under stones or beneath the roots of overhanging vegetation (Inger & Stuebing 2005). Anatomically, the tadpoles are quite unusual. They’re slender animals where the tail is only slightly deeper than the body and the tail fin is low; the eyes are large and the expanded, upwardly directed lips form a terminally positioned, funnel-shaped or ‘umbelliform’ oral disk.
Megophryids are definitely pelobatoids: that is, they’re members of the spadefoot toad assemblage. But how are they related to other pelobatoid lineages? I’ll have to come back to that issue in another article. And then there are the other lineages within Megophryidae. Yes, there are others. For, you see, there are a lot of anuran lineages.
For previous Tet Zoo articles on frogs and toads, see...
In pursuit of Romanian frogs (part II: WESTERN PALAEARCTIC WATER FROGS!!)
The toads series comes to SciAm: because Africa has toads too
Refs - -
Delorme, M., Dubois, A., Grosjean, S. & Ohler, A. 2006. Une nouvelle ergotaxinomie des Megophryidae (Amphibia, Anura). Alytes 24, 6-21.
Frost, D. R. 2014. Amphibian Species of the World: an Online Reference. Version 6.0 (30th December 2014). Electronic Database accessible at http://research.amnh.org/herpetology/amphibia/index.html. American Museum of Natural History, New York, USA.
Inger, R. F. & Stuebing, R. B. 2005. A Field Guide of the Frogs of Borneo. Natural History Publications (Borneo), Kota Kinabalu.
Li, C., Guo, X.-g. & Wang, Y.-z. 2011. Tadpole types of Chinese megophryid frogs (Anura: Megophryidae) and implications for larval evolution. Current Zoology 57, 93-100.
Wang, Y.-Y., Zhang, T.-D., Zhao, J., Yang, J.-H., Pang, H. & Zhang, Z. 2012. Description of a new species of the genus Xenophrys Günther, 1864 (Amphibia: Anura: Megophryidae) from Mount Jinggang, China, based on molecular and morphological data. Zootaxa 3546, 53-67.