This is a baby crab, therefore young.
This is also a reconstruction of a 150 million year old fossil, therefore old. Huag and colleagues show this is the oldest baby crab in the fossil record (150 million years!). That it’s the oldest may not be as impressive when you consider that it’s only the second baby crab in the fossil record ever found. So it had a fifty-fifty chance to be oldest!
What a spectacular find.
For more on this discovery, read here. I’d like to direct you to the original paper, but despite Nature Communications being an “open access journal now,” not all of its papers are open access - including this one. Sigh.
Haug JT, Martin JW, Haug C. 2015. A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs. Nature Communications 6: 6417. http://dx.doi.org/10.1038/ncomms7417