Sadly no Gonodonta species are found in Australia. Are those true legs I see on the left ,? Was it stiff or was it squishy? @Lorraine : please could you rinse the detritus off it so that we can see markings that may help identify the species? .
Reverse google gave me Gonodonta. I have no idea what it is! I didn’t touch it too much although it was fairly robust. I collected it with a couple of sticks. It was on the hot footpath and when first touched it with my shoe it moved. However in hindsight I suspect it had somehow adhered to the hot path and my moving it made it relax. I’m pretty sure it was dead. I initially thought it might have been a baby snake some bird had dropped. Then it became even more of a mystery when a local Facebook group couldn’t identify it. Grateful for suggestions of what to do or where to go next. I’m in Canberra Could it be an import or unlikely passenger on produce? Its texture was rather rubbery not unlike a squid tentacle type texture. Certainly not soft bodied like you might expect from a caterpillar type creature I tried swishing it in a jug of water that removed a bit of the detritus away As for true legs I can’t be sure It’s in my freezer at the moment
The largest smooth Australian caterpillar is probably Phyllodes imperialis, the caterpillar of which has been reported to grow to 12 cms, and it has some striking markings which may survive in death, see https://lepidoptera.butterflyhouse.com.au/cato/imperialis.html