This group of arthropods originated in the Late Ordovician, about 450 million years ago. Horseshoe crabs are marine invertebrates and a type of arthropod. Marine invertebrates may have a life span up to 10-11 million years.

Mammal species seem to have a lifespan of a million or two million years.

The lifespan may be a few million years or so with a lot of variation amongst different types of creatures. They originate at a point in geologic time and then go extinct at some later date. Species too have lifespans just like individuals. Your family lineage though contains an unbroken chain of descendants of which you are a living relative today. Every individual in your family lived within the normal range of humans lifespans. But it would be absurd to suggest that you have in your family someone living today who was born in the 1300's. You could say that your family is a survivor from before the days of the black plague. Say you have well kept records that traces your genealogy to 700 years ago. The term survivor though refers not to individual species but a lineage. What are you referring to when you use the term 'survivor'? For example, the talk compares the coming and going of different species like the mastodon and musk ox with the persistence of horseshoe crabs suggesting that survivors means individual species. One important point is never made in the talk. The talk has a lot of information about the habitats, life history and idiosyncrasies of life style and biochemistry of many of these organisms. He qualifies the term 'unchanged through time' by clarifying that these creatures have evolved, maybe not in morphology, but certainly at a molecular level. These kind of creatures whose morphology resembles that of their ancestors are called 'living fossils' and Richard Fortey gives quite a few examples in this entertaining talk. The lead-in talks about how in the history of life, species have come and gone, except for some remarkable survivors who persist today almost unchanged in appearance since they first originated hundreds of millions of years ago. OnPoint Radio had palaeontologist Richard Fortey for a talk on his new book Horseshoe Crabs and Velvet Worms: The Story of the Animals and Plants That Time Has Left Behind.

Horseshoe crabs and velvet worms