Temporary expansion to shelf depths rather than an onshore-offshore trend: the shallow-water rise and demise of the modern deep-sea brittle star family Ophiacanthidae (Echinodermata: Ophiuroidea)
Temporary expansion to shelf depths rather than an onshore-offshore trend: the shallow-water rise and demise of the modern deep-sea brittle star family Ophiacanthidae (Echinodermata: Ophiuroidea)
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DOI：
10.5852/ejt.2013.48
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发表时间：
2013-07-02
影响因子：
1.2
通讯作者：
Thuy, Ben
中科院分区：
文献类型：
--
作者：
Thuy, Ben
迄今所提出的关于现代深海动物群的年龄和可能的古代的假设几乎都同意这样的假设，即深海动物群主要是由浅水环境殖民化的结果。在这里，蛇棘科的化石记录是根据校准的系统发育系统追踪的，蛇棘科是一个现代深海海蛇尾科，在陆架深处有广泛的化石出现。几条线索的证据表明蛇棘科起源于深海，并在深海中大量分化，最迟在三叠纪末期，大多数现存的分支已经分化。在侏罗纪时期，该科短暂侵入陆架环境，其丰度和多样性可与同时期和现代深海环境相媲美，随后丰度逐渐下降，再次主要局限于深海。这里提出的暂时扩展到陆架环境的模式，支持了深海环境对浅水生物多样性作出重大贡献的潜力；到目前为止，这方面大多被忽视了。推测三叠纪—侏罗系边界陆架环境的大规模蛇刺类入侵是由热盐环流向盐温环流的转变引发的，这种转变减弱了水柱的热分层，从而为海洋分类群的垂直迁移提供了增强的机会。
Hypotheses on the age and possible antiquity of the modern deep-sea fauna put forward to date almost all agree on the assumption that the deep-sea fauna is largely the result of colonisation from shallow-water environments. Here, the fossil record of the Ophiacanthidae, a modern deep-sea brittle star family with extensive fossil occurrences at shelf depths, is systematically traced against a calibrated phylogeny. Several lines of evidence suggest that the Ophiacanthidae originated and greatly diversified in the deep sea, with most extant clades having diverged by the end of the Triassic at the latest. During the Jurassic, the family temporarily invaded shelf environments, attaining relative abundances and diversities comparable to those found in coeval and modern deep-sea settings, and gradually declined in abundance subsequently, to become largely restricted to the deep-sea again. The pattern of temporary expansion to shelf environments suggested here underpins the potential of deep-sea environments to contribute significantly to shallow-water biodiversity; an aspect that has mostly been neglected so far. It is speculated that the large-scale ophiacanthid invasion of shelf environments around the Triassic-Jurassic boundary was initiated by a change from thermohaline to halothermal circulation, attenuating the thermal stratification of the water column and thus providing opportunities for enhanced vertical migration of marine taxa.