|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Trilobita - Agnostida - Agnostidae
It was recombined as Trinodus tardus by Barrande (1846) and Kielan (1960); it was recombined as Arthrorhachis tarda by Hall and Corda (1847) and Ahlberg (1989); it was recombined as Agnostus tardus by Barrande (1852); it was recombined as Arthrorhachis tardus by Hoel (1999).
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.