hˈʌnsɹuːk lˈædʒɚstˌɛt, ðə pɹˈaɪmɚɹi slˈeɪt fɔːɹmˈeɪʃən ʌvwˈɪtʃ dɹˈɛpɐnˌæspiz ɪz mˈoʊst kˈɑːmənli fˈaʊnd, ɑːɹ ʌv ˈɜːli dɛvˈoʊniən ˈeɪdʒ, ænd ɪz θˈɔːt tə hæv dᵻpˈɑːzɪɾᵻd dˈʊɹɹɪŋ ðə lˈeɪt pɹˈædʒən tʊ ˈɜːli ˈɛsmiən ˈeɪdʒᵻz ɪn sʌbsˈaɪdɪŋ bˈeɪsənz ðæt wɜː sˈɛpɚɹˌeɪɾᵻd baɪ swˈɛlz.
Hunsrück lagerstätte, the primary slate formation of which Drepanaspis is most commonly found, are of Early Devonian age, and is thought to have deposited during the Late Pragian to Early Esmian Ages in subsiding basins that were separated by swells.