title: Flourishing Sponge-Based Ecosystems after the End-Ordovician Mass Extinction.
abstract: The Late Ordovician (Hirnantian, approximately 445 million years ago) extinction event was among the largest known, with 85% species loss [1]. Post-extinction survival faunas are invariably low diversity, especially benthic communities [2], but ecological structure was restored relatively rapidly [1]. This pattern, however, reflects organisms with robust skeletons, as only one exceptionally preserved Hirnantian fossil biota was previously known [3, 4]; in particular, almost no Hirnantian sponges have been recorded. Our study reveals an extraordinarily diverse, sponge-dominated community thriving immediately after the Hirnantian extinction in Zhejiang, South China. Several contemporaneous sites preserve a total diversity of over 75 sponge species, many with preserved soft tissues, in pronounced contrast to normal survival and early recovery faunas. This diversity is unprecedented for any Hirnantian fossil group, and the fauna provides a unique window into a post-extinction ecosystem. The sponges are often large and structurally complex and represent numerous different lineages that survived the extinction. Layers with abundant sponge remains were deposited after other mass extinctions [5, 6], suggesting a general pattern of sponge abundance during collapse of Phanerozoic marine ecosystems. It is possible that the conditions of ecological collapse increase the particulate food sources for sponges, while they themselves are relatively unaffected by the crises. Furthermore, the abundance of sponges in the Hirnantian sequence of South China may have aided post-extinction ecosystem recovery by stabilizing the sediment surface, allowing sessile suspension feeders such as brachiopods, corals, and bryozoans to recover rapidly.
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China; Department of Natural Sciences, Amgueddfa Cymru - National Museum Wales, Cathays Park, Cardiff CF10 3LP, UK.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Botting
authors.affiliation: Department of Natural Sciences, Amgueddfa Cymru - National Museum Wales, Cathays Park, Cardiff CF10 3LP, UK.
authors.forename: Lucy A
authors.initials: LA
authors.lastname: Muir
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China; CAS Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing 210008, China. Electronic address: ydzhang@nigpas.ac.cn.
authors.forename: Yuandong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Ma
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China.
authors.forename: Junye
authors.initials: J
authors.lastname: Ma
authors.affiliation: Zhejiang Institute of Geological Survey, Hangzhou 311203, China.
authors.forename: Longwu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Zhejiang Institute of Geological Survey, Hangzhou 311203, China.
authors.forename: Jianfang
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Song
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Fang
mesh_terms: D000818:Animals; D044822:Biodiversity; D002681:China; D017753:Ecosystem; D053476:Extinction, Biological; D005580:Fossils; D011161:Porifera
keywords: Demospongiae; Eurypterida; Hexactinellida; Konservat-Lagerstätte; Porifera; Reticulosa; exceptional preservation; post-extinction recovery