Global Ordovician vertebrate biogeography
Global Ordovician vertebrate biogeography
复制标题
DOI：
10.1016/s0031-0182(03)00301-8
复制
发表时间：
2003-06-05
影响因子：
3
通讯作者：
Turner, S
中科院分区：
文献类型：
--
作者：
Blieck, A;Turner, S
近几十年来，寒武纪-奥陶纪脊椎动物和假定的脊椎动物的出现被反复声称，已证实的类群具有矿化的组织，脊椎动物的组织形态仍然相对罕见。目前我们唯一能识别的生物地理省是Gondwana特有组合（GEA），其中可能有来自澳大利亚的晚寒武世的碎片遗迹，但更明确的是早奥陶世（Arenigian）至晚奥陶世（Caradocian）早期的arandaspids（即Sacabambaspis， Arandaspis）和其他已知的分类群来自南美洲和澳大利亚。某些软骨鱼（“鲨鱼”，起初没有牙齿，可能不构成单系群）可能起源于东冈瓦纳省，然后在蒙古、塔里木和中国南方的奥陶世晚期和志留纪早期被发现。GEA动物区系在卡拉多世中晚期消失，脊椎动物直到晚志留世中晚期才在冈瓦纳重新出现。晚奥陶纪（-455 Myr或更早）的脊椎动物也肯定来自劳伦提亚，即北美（翼蛛形目Astraspis， Eriptychius，以及各种齿形类群，包括软骨鱼类，placoderm和棘螈类遗骸）和西伯利亚（具有不寻常组织学的翼蛛状微遗骸）。这可能与一组新的低等脊椎动物相对应)，以及来自北美和俄罗斯（提曼-佩霍拉，塞维纳亚地岛群岛和西伯利亚）的疑似龙齿目动物和齿齿目动物的鳞片。这被定义为劳伦斯-波罗的海-西伯利亚组合（LBSA）。我们还提到了在南非发现的一种奥陶纪晚期无蛛科动物。尽管GEA和LBSA在时间上有小的重叠，但它们之间的分类群没有明显的关联。最近发表的各种奥陶系古地理模型被严格地分析和考虑为四组：原型古地理重建，两种替代解决方案，和一个紧凑的版本。以BA1（海洋潮间带）- BA3（浅层潮下）为主的环境为模型，评价了脊椎动物的生境及其扩散能力。奥陶系脊椎动物生物地理的主要特征是地方性。此外，目前缺乏对大多数分类群的完整描述，这些分类群通常仅由孤立的微遗骸代表，并且需要进行彻底的系统发育分析，这妨碍了任何系统发育古生物地理学研究。在此框架下，我们还评估了外部物理因素与脊椎动物奥陶纪辐射之间的可能联系。晚元古代海洋磷酸盐的沉积和早寒武纪地球上氧气的增加可能是脊椎动物在硬组织出现之前进化的动力。海相锶同位素比值在中晚奥陶世转变期间的急剧下降，被解释为主要受大陆碰撞构造及其相关的侵蚀和风化控制，并被认为可能是地幔超级柱事件的结果，该事件可能导致了突出的卡拉多西海侵期。这可能是脊椎动物关注点从冈瓦纳人转向劳伦人的一个因素。(C) 2003 Elsevier Science B.V.版权所有
Cambrian-Ordovician vertebrate and supposed vertebrate occurrences have been repeatedly claimed during recent decades, with confirmed taxa bearing mineralized tissues with a vertebrate histomorphology still relatively rare. The only biogeographic province that we can presently recognize is the Gondwana Endemic Assemblage (GEA) with possible Late Cambrian fragmentary remains from Australia but more definite Early Ordovician (Arenigian) to early Late Ordovician (Caradocian) arandaspids (i.e., Sacabambaspis, Arandaspis) and other taxa known from South America and Australia. Certain chondrichthyans ('sharks', at first without teeth and which might not constitute a monophyletic group) might have originated in East Gondwana province and then are found in the Late Ordovician and Early Silurian of Mongolia, Tarim, and South China. The GEA fauna proper disappears by middle-late Caradocian and vertebrates do not reappear in Gondwana until mid Late Silurian. Late Ordovician (-455 Myr or earlier) vertebrates are also known with certainty from Laurentia, viz., North America (pteraspidomorphs Astraspis, Eriptychius, and various gnathostome-like taxa including chondrichthyan-, placoderm- and acanthodian-like remains), and Siberia (astraspid-like microremains with an unusual histology, which might correspond to a new group of lower vertebrates) as well as scales from putative loganiid and thelodontidid thelodonts from North America and Russia (Timan-Pechora, the Severnaya Zemlya archipelago and Siberia). This is defined as the Laurentia-Baltica-Siberia Assemblage (LBSA). We also mention one enigmatic reference to a Late Ordovician anaspid in South Africa. There is no clear association of taxa between the GEA and LBSA despite a small overlap in time. Various recent palaeogeographic models published for the Ordovician are critically analyzed and considered within four groups: the archetypal palaeogeographic reconstructions, two alternative solutions, and a compact version. Habitats of vertebrates in mostly BA1 (marine intertidal) to BA3 (shallow subtidal) environments, and their dispersal capabilities are evaluated with regard to those models. The main feature of Ordovician vertebrate biogeography is endemism. Furthermore, the present lack of complete descriptions of most taxa, which are often represented only by isolated microremains, and the need for a thorough phylogenetic analysis preclude any phylogenetic palaeobiogeographic study. In such a framework, we also evaluate possible links between external, physical factors and the Ordovician radiation of vertebrates. The Late Proterozoic deposition of oceanic phosphate and the Early Cambrian increase in oxygen on Earth might have been the spur for vertebrate evolution before the phase when hard tissues appeared. The sharp decline of the marine strontium isotope ratio during the Middle to Late Ordovician transition, interpreted as having been controlled primarily by continental collisional tectonics and its associated erosion and weathering, has been proposed as the consequence of a possible mantle superplume event which could have caused the prominent Caradocian transgressive phase. This might have been a factor in the changeover from a Gondwanan to a Laurentian focus for vertebrates. (C) 2003 Elsevier Science B.V. All rights reserved.