There are exactly 999 genera with max_ma equal to min_ma. This appears to be a bug in assigning max_ma and min_ma. For example, the entry on line 481 of sepkoski_updated.csv exported form R reads:
phylum class order genus fauna interval_max interval_min max_ma min_ma
{'Actinopoda'} {'Radiolaria'} {'Spumellaria'} {'Inanihella'} {'NA'} {'Ludfordian'} {'Gorstian'} 425.6 425.6
However, and yet according to interval_max and interval_min it appeared at the start of Gorstinian (427.4 Mya) and disappeared at the end of Ludfordian which is 425.6 Mya
(see https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf).
Here are a few other lines with max_ma=min_ma:
phylum class order genus fauna interval_max interval_min max_ma min_ma
{'Annelida' } {'Polychaeta' } {'Eunicemorpha' } {'Microdactylophora'} {'Cambrian'} {'Homerian' } {'Sheinwoodian'} 430.5 430.5
{'Annelida' } {'Polychaeta' } {'Eunicemorpha' } {'Palaeopelyx' } {'Cambrian'} {'Homerian' } {'Sheinwoodian'} 430.5 430.5
{'Annelida' } {'Polychaeta' } {'Serpulimorpha' } {'Serpularia' } {'Cambrian'} {'Darriwilian'} {'Dapingian' } 467.3 467.3
{'Annelida' } {'Polychaeta' } {'Serpulimorpha' } {'Sinuocornu' } {'Cambrian'} {'Homerian' } {'Sheinwoodian'} 430.5 430.5
{'Annelida' } {'Polychaeta' } {'Spiomorpha' } {'Vetustovermis' } {'Cambrian'} {'Stage 3' } {'Stage 2' } 521 521
{'Annelida' } {'Polychaeta' } {'Terebellomorpha' } {'Cryptosiphon' } {'Cambrian'} {'Darriwilian'} {'Dapingian' } 467.3 467.3
{'Annelida' } {'Polychaeta' } {'uncertain' } {'Lecathylus' } {'Cambrian'} {'Ludfordian' } {'Gorstian' } 425.6 425.6
{'Annelida' } {'Polychaeta' } {'uncertain' } {'Lockportia' } {'Cambrian'} {'Homerian' } {'Sheinwoodian'} 430.5 430.5
{'Arthropoda'} {'Malacostraca'} {'Phyllocarida incerta sedis'} {'Peltocaris' } {'Modern' } {'Homerian' } {'Sheinwoodian'} 430.5 430.5
There are exactly 999 genera with max_ma equal to min_ma. This appears to be a bug in assigning max_ma and min_ma. For example, the entry on line 481 of sepkoski_updated.csv exported form R reads:
phylum class order genus fauna interval_max interval_min max_ma min_ma
{'Actinopoda'} {'Radiolaria'} {'Spumellaria'} {'Inanihella'} {'NA'} {'Ludfordian'} {'Gorstian'} 425.6 425.6
However, and yet according to interval_max and interval_min it appeared at the start of Gorstinian (427.4 Mya) and disappeared at the end of Ludfordian which is 425.6 Mya
(see https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf).
Here are a few other lines with max_ma=min_ma:
phylum class order genus fauna interval_max interval_min max_ma min_ma