- 學位論文
臺灣劍齒象屬分類芻議及其生物地理意義
A Revise of Classification of Stegodon of Taiwan and its Biogeographical Implication
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摘要
「左鎮動物群」是台灣一個極富盛名的更新世哺乳動物群。劍齒象（Stegodon）是左鎮動物群中的一個成員，在台中與台南地區皆有發現。所發現的劍齒象化石在台中地區分佈於卓蘭層到頭嵙山層，而台南地區的劍齒象化石則集中於崎頂層。卓蘭層的頂界被認為落在哈拉米諾事件（Jaramillo Event）底部，而崎頂層則主要屬於布倫期（Brunhes Epoch），因此劍齒象應該是先棲息在台灣中部，而後向南擴展。 台灣的劍齒象曾被鑑定出三個種：分別是曙光劍齒象（Stegodon aurorae）、東方劍齒象（S. orientalis）、獨特劍齒象（S. insignis）。除了以上這些種之外，台灣的劍齒象還有一個新亞種：S. elephantoides taiwanicus。這是一個介於類象劍齒象（S. elephantoides）與師氏劍齒象（S. zdanskyi）之間的中間型，一類體型大而臼齒特徵原始的劍齒象。這個亞種的模式標本發現於崎頂層過嶺段，時間上為中更新世。這個亞種可能是來自中國的類象劍齒象或師氏劍齒象的後裔，以台灣作為棲息避難所，原始性的特徵持續保存。 之前鑑定為獨特劍齒象的標本目前已佚失而無法重新檢視。另外，經由型態上的比較與檢視，之前定為曙光劍齒象的兩件標本重新鑑定為東方劍齒象。另一件被鑑定為曙光劍齒象的標本，雖然具有非常相似於日本的曙光劍齒象的特徵，但是因為太過於破碎，無法建立確切的鑑定。因此，並沒有可靠的證據顯示台灣曾有曙光劍齒象存在。 台灣所發現的劍齒象化石可明確的鑑定出兩個物種：類象劍齒象台灣亞種（S. e. taiwanicus）和東方劍齒象。類象劍齒象與東方劍齒象俱為主要生存於中國南方的物種，且東方劍齒象為更新世大熊貓—劍齒象動物群（Ailuropoda-Stegodon fauna）典型成員。連同過去所發現的中國犀牛早坂亞種（Rhinoceros sinensis hayasaka），台灣的劍齒象等大型哺乳動物應自中國南方播遷而來。
並列摘要
“Chochen Fauna” is one of the most famous mammal fossil faunas in Taiwan during Pleistocene. Stegodon fossils from “Chochen Fauna” have been discovered from Taichung and Tainan areas. The Stegodon fossils in Taichung distribute from Cholan Formation to Toukeshan Formation while the fossils from Tainan are all from Chiting Formation. Since the top of Cholan Formation mainly is positioned at about the bottom of the Jaramillo Event, whereas the Chiting Formation mainly belongs to Brunhes Epoch, apparently the Stegodon inhabited in the central Taiwan and then expanded to southern area. Previous studies have identified Stegodon aurorae, S. orientalis, and S. insignis from Taiwan. In addition to these species, a new taxon, S. elephantoides taiwanicus, has been identified in this study. This was a large and primitive Stegodon intermediate between S. zdanskyi and S. elephantoides. It was found from the Kuoling Member of the Chiting Formation of the middle Pleistocene in age. This newly recognized taxon is considered as a descendant emigrant dispersed from China and became a relic member of the primitive S. elephantoides survived in Taiwan refugia. The specimens of S. insignis are missing and can not be reexamined. Two of the specimens previously identified as S. aurorae are now revised to be S. orientalis by morphological comparisons. Although another specimen identified as S. aurorae has characters similar to S. aurorae in Japan, it is actually too fragmental to assure such a taxonomic designation. Hence, there is no solid evidence for the existence of S. aurorae in Taiwan. In summary, Two Stegodon species can be identified from Taiwan materials. They are S. elephantoides taiwanicus and S. orientalis. S. elephantoides and S. orientalis mainly distributed in southern China and the latter species is known as a member of the Pleistocene Ailuropoda-Stegodon fauna. Together with previously discovered Rhinoceros sinensis hayasaka, Stegodon and other associated large mammals in Taiwan are likely to come from southern China during early to middle Pleistocene.
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