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KT FROGS & EXTINCTION



On KT extinctions and frogs, Matt Bonnan wrote...

> Bakker is fond of saying something to effect of: "The frogs made it > through the extinction. They are very environmentally sensitive, so > why is that they survived okay?" As far as I know, we have no taxa > count of the number of frogs, turtles, etc. that were in existence > before and after the end of the Cretaceous. Therefore, we do not > know how well or badly frogs, turtles, and little animals did: my bet > is many frogs and turtles were wiped out, but the fossil record is too > coarse for us to know exactly what happened.

Note that Matt was suitably sceptical of the patented Bakker sound- bite: I'm not criticising what he said.

Bakker has stated several times that a North American fossil frog - I don't know the species name offhand - made it across the KT boundary. Apparently (J. Kirkland pers. comm.) the material on which this assertion is based comes from a bunch of disassociated material found at more than one site. While general statements about extinction levels (or lack of them) are interesting, the key data comes from species-level extinctions.

Frogs clearly did make it across the KT boundary as there are good Jurassic and Cretaceous records of ascaphids, pipoids and discoglossids. Caudates (including sirenids), caecilians and albanerpetontids also clearly made it through. Did these groups undergo significant species-level extinctions? I don't know, and I don't know if anyone has investigated this. 'Time bars' for higher-level taxa (e.g. those in _The Fossil Record 2_) can be misleading because they create the impression of 'unaffected' lineage continuation.

Lissamphibians today are in critical decline, there's no doubt about this (the paradox is that more new species are being discovered, such that - as predicted early in the last decade - extant lissamphibians now outnumber mammals [5000 vs 4400 or so]). There have been some recent comments on the list about the superfluousness of palaeontology - does it really help anybody and do we only do it because it's fun (and because we live in rich countries)? Well maybe. On a documentary I watched last night a NASA scientist, I think she was part of the SETI programme, stated that the search for ET intelligence was the most important thing humanity could do. This is my opinion, but that's crap. Biodiversity and conservation are what matters - everything else can wait until later (again, I know that I can only make this statement because I live in a rich developed country). Palaeontology, as the documentation of diversity in the past, has a key role to play in our understanding of biodiversity. The history of lineages, their vulnerability or otherwise to extinction and their former and future diversity, are becoming an active part of conservation and form the core of what's being called extinction management.

May seem like I went off at a bit of a tangent but my point is that, if we can learn about the causes of lissamphibian extinction from the fossil record, we may have a historic perspective on why extant species are disappearing. Palaeontology is thus relevant and important.

To quote, rant over.

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
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