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"we've described over 20,000 different trilobite species" and "Most of them appeared to be ostracods... there are 13,000 existing ostracod species." The shee

"we've described over 20,000 different trilobite species" and "Most of them appeared to be ostracods... there are 13,000 existing ostracod species." The sheer quantity of fossils and/or specimens to build out those lists of tens of thousands of species is mind boggling. I known there has been a shift from traditional species classification to a model based on genetics (cladistics). Has this changed the definition of what is considered a species? For example, can we assume that none of these 20,000 trilobite species could reliably procreate with one another?

stvltvs 3y ago
I get the impression that no single method (genetics, morphology, ecology, geography, etc.) trumps the others in taxonomy. For example, Homo sapiens and Homo neanderthalensis interbred successfully and yet are separate species.
- gdprrrr 3y ago
  I think some consider it a subspecies Homo sapiens neanderthalensis
- BurningFrog 3y ago
  There is no clear definition of "species".
  - jaggederest 3y ago
    Cladistics can be thought of as k-means clustering in a Hamming space of individual organisms attributes and genetics, I think. A species is a tight cluster, and as you go up towards phyla the clustering becomes more diffuse.
    - BurningFrog 3y ago
      That's a definition. I'm not convinced it's "clear" :)
      - dekhn 3y ago
        it's not even a definition, it's a heuristic approximation. Likely the concept of species can't really be truly defined, but works best as a loose concept for organizing thinking about evolution.
    - jhbadger 3y ago
      That's more phenetics (clustering by shared similarities) than cladistics. Cladistics needs a hypothesis of shared ancestry. https://en.wikipedia.org/wiki/Phenetics https://en.wikipedia.org/wiki/Phenetics https://en.wikipedia.org/wiki/Cladistics https://en.wikipedia.org/wiki/Cladistics
RetroTechie 3y ago
Given how long trilobites were around, and geographical distribution, there could be significant time and/or space distance between any specimens found. Not saying they couldn't interbreed though. You'd have to ask an expert.

stvltvs 3y ago

I get the impression that no single method (genetics, morphology, ecology, geography, etc.) trumps the others in taxonomy. For example, Homo sapiens and Homo neanderthalensis interbred successfully and yet are separate species.

gdprrrr 3y ago
I think some consider it a subspecies Homo sapiens neanderthalensis
BurningFrog 3y ago
There is no clear definition of "species".
- jaggederest 3y ago
  Cladistics can be thought of as k-means clustering in a Hamming space of individual organisms attributes and genetics, I think. A species is a tight cluster, and as you go up towards phyla the clustering becomes more diffuse.
  - BurningFrog 3y ago
    That's a definition. I'm not convinced it's "clear" :)
    - dekhn 3y ago
      it's not even a definition, it's a heuristic approximation. Likely the concept of species can't really be truly defined, but works best as a loose concept for organizing thinking about evolution.
  - jhbadger 3y ago
    That's more phenetics (clustering by shared similarities) than cladistics. Cladistics needs a hypothesis of shared ancestry. https://en.wikipedia.org/wiki/Phenetics https://en.wikipedia.org/wiki/Phenetics https://en.wikipedia.org/wiki/Cladistics https://en.wikipedia.org/wiki/Cladistics

RetroTechie 3y ago

Given how long trilobites were around, and geographical distribution, there could be significant time and/or space distance between any specimens found. Not saying they couldn't interbreed though. You'd have to ask an expert.