Late Cretaceous bioconnections between Indo-Madagascar and Antarctica: refutation of the Gunnerus Ridge causeway hypothesis
Late Cretaceous bioconnections between Indo-Madagascar and Antarctica: refutation of the Gunnerus Ridge causeway hypothesis
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DOI：
10.1111/j.1365-2699.2011.02546.x
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发表时间：
2011-10-01
影响因子：
3.9
通讯作者：
Krause, David W.
中科院分区：
文献类型：
--
作者：
Ali, Jason R.;Krause, David W.
目的评估Gunnerus Ridge陆桥假说，该假说认为晚白垩世南极洲东部和马达加斯加南部之间存在一条堤道，允许陆生脊椎动物通过。地点：南极洲东部，南印度洋，马达加斯加。方法利用地质和地球物理资料、测深图和板块构造重建资料进行古地理模拟，并对经地层校准的系统发育分析进行评价，以记录选定类群的幽灵谱系。结果现有的地质和地球物理证据表明，南极洲东部的Gunnerus Ridge和马达加斯加南部在整个晚白垩世被一片广阔的海洋隔开。在晚白垩纪中期，裂口可能被两个中间的地形高点所打断，马达加斯加高原北部和康拉德高地，后者虽然可能很大，但仍与南极洲的里瑟-拉森半岛相隔约1600公里。最近，经过地层学校准的系统发育学，包括马达加斯加和印度次大陆的大型陆生白垩纪末期脊椎动物分类群，揭示了延伸至早白垩纪的长期幽灵谱系。认为南极洲和马达加斯加在晚白垩纪由Gunnerus Ridge和马达加斯加南部之间的长堤道连接，并且陆生脊椎动物能够利用这一地理特征殖民新的边界的观点，几乎肯定是不正确的，就像之前关于南极洲和印度次大陆之间横跨Kerguelen高原的所谓堤道所证明的那样。通过非洲大陆的联系来解释印度-马达加斯加和南美洲的几个化石和现存脊椎动物分类群的密切关系是另一个选择，尽管这也缺乏可信度。我们的结论是：(1)在整个晚白垩世，没有贯穿南极洲的连续堤道，也没有连接南美洲西部和印度-马达加斯加东部的陆桥；(2)中型到大型的专性陆生恐龙（如abelisauroid兽脚亚目恐龙、titanosaurian蜥脚类恐龙和notosuchian crocodyliforms）在破碎化之前在冈瓦南大陆广泛分布，并在早白垩纪结束前在印度-马达加斯加分离。
Aim To evaluate the Gunnerus Ridge land-bridge hypothesis, which postulates a Late Cretaceous causeway between eastern Antarctica and southern Madagascar allowing the passage of terrestrial vertebrates.Location Eastern Antarctica, southern Indian Ocean, Madagascar.Methods The review involves palaeogeographical modelling, which draws upon geological and geophysical data, bathymetric charts, and plate tectonic reconstructions, and the evaluation of stratigraphically calibrated phylogenetic analyses to document ghost lineages of select taxa.Results The available geological and geophysical evidence indicates that eastern Antarctica's Gunnerus Ridge and southern Madagascar were separated for the entire Late Cretaceous by a vast marine expanse. In the mid-Late Cretaceous, the gap was probably punctuated by land on two intervening physiographical highs, the northern Madagascar Plateau and Conrad Rise, the latter of which, although probably large, was still separated from Antarctica's Riiser-Larsen Peninsula by c. 1600 km. Recent, stratigraphically calibrated phylogenies including large, terrestrial end-Cretaceous vertebrate taxa of Madagascar and the Indian subcontinent reveal long ghost lineages that extended into the Early Cretaceous.Main conclusions The view that Antarctica and Madagascar were connected by a long causeway between the Gunnerus Ridge and southern Madagascar in the Late Cretaceous, and that terrestrial vertebrates were able to colonize new frontiers using this physiographical feature, is almost certainly incorrect, as was previously demonstrated for the purported causeway between Antarctica and the Indian subcontinent across the Kerguelen Plateau. Connection across mainland Africa to account for the close relationships of several fossil and extant vertebrate taxa of Indo-Madagascar and South America is another option, although this too lacks credibility. We conclude that (1) throughout the Late Cretaceous there was no intervening, continuous causeway through Antarctica and associated land bridges between South America to the west and Indo-Madagascar to the east; and (2) mid- to large-sized, obligate terrestrial forms (e. g. abelisauroid theropod and titanosaurian sauropod dinosaurs and notosuchian crocodyliforms) gained broad distribution across Gondwanan land masses prior to fragmentation and were isolated on Indo-Madagascar before the end of the Early Cretaceous.