**早坂犀**（學名：），又名**早坂犀牛**、**早坂島犀**、**台灣犀牛**，原先被歸類為已滅絕的獨角犀屬物種中國犀（*Rhinoceros sinensis*）的亞種，但在2021年被重新分類為新命名的島犀屬（*Nesorhinus*）中，其化石在桃園市大溪區內柵和台南市左鎮區菜寮溪出土，在臺中大坑和高雄旗津也有疑似早坂島犀化石的紀錄。

研究歷史
----

早坂犀骨架，於臺南左鎮化石園區展出
臺灣最早的犀牛化石紀錄可追溯至1926年，由佐藤採集至新竹州大溪郡大溪街內柵(今桃園市大溪區內柵)的下顎骨與臼齒。臺北帝國大學的早坂一郎在數年後也於佐藤發現標本的原地點附近重新發現一個完整度更高之上顎骨，並於1942年指出臺灣除了大溪外，於臺中州大屯郡北屯庄大坑（今臺中市北屯區大坑）、臺南州新化郡左鎮庄（今臺南市左鎮區）和高雄州高雄市旗後（今高雄市旗津區）皆疑似有獨角犀屬（*Rhinoceros*）化石新種的紀錄。

1971年，臺南著名的化石收藏家潘常武造訪左鎮時，收到來自當地小學生陳世卿在菜寮溪河床上尋獲的數塊犀牛牙齒化石。潘常武偕同陳世卿調查了犀牛牙齒的發現處，並推測這些牙齒化石是從河床邊的泥岩層沖刷出來，岩層裡可能還藏有剩餘的犀牛化石，並將這個消息轉達給國立臺灣大學的林朝棨教授。台灣省立博物館在1971年12月組成工作團隊，團隊包含林朝棨教授、潘常武、左鎮知名的化石採集者陳春木等人，前往臺南左鎮進行第一次挖掘工作，並挖掘出包含牙齒、肢骨在內的犀牛化石，但仍有部分肢骨保留在原地層中。1972年，團隊獲得日本古生物學家鹿間時夫和大塚裕之的加入，進行第二次挖掘，將剩餘的肢骨給挖掘出來。

1984年，大塚裕之和林朝棨將先前早坂一郎採集自大溪的標本、台灣省立博物館挖掘出的標本以及臺南縣立化石博物館裡採集自左鎮的犀牛化石標本共同命名為**中國犀牛早坂氏亞種**（*Rhinoceros sinensis hayasakai*），以紀念早坂一郎對於臺灣犀牛化石的研究與發現。

2021年，發現於菲律賓的**菲律賓犀**（*Rhinoceros philippinensis*）被重新檢視與研究，並發現其與早坂中國犀牛具有共同的獨特特徵，不同於亞洲的獨角犀（*Rhinoceros*）和雙角犀（*Dicerorhinus*），為東亞獨特之支系，兩者因此一起被建立為新屬**島犀屬**（*Nesorhinus*），早坂中國犀牛因此被重新分類，成為合併新物種早坂島犀（*Nesorhinus hayasakai*）。

形態描述
----

早坂犀頭部特寫
島犀屬為體型中等的犀牛，該屬不同於其他犀牛科物種的六個辨識特徵包括上頰齒（upper cheek teeth）的牙根完全分離，P2-4上通常有鉤狀突（crochet），P3上沒有嵴（crista），M1-2上皆無原尖收缩（protocone constriction），外脊（ectoloph）後半部凹陷，下頰齒（lower cheek teeth）上的下三角座成角狀（trigonid angular），肩胛骨（Scapula）後方的盂上結節（supraglenoid tubercle）凸起，突出於肩胛骨。

早坂島犀擁有三個自衍徵，且皆位於牙齒：P2-4上皆具鉤狀突（crochet），上臼齒皆不具唇面煙齒帶（lingual cingulum），下頰齒（lower cheek teeth）上的三角座（trigonid）在咬合面呈尖銳二面體狀（acute dihedron）。

雖然目前在早坂島犀和菲律賓島犀的標本中並未發現鼻骨（Nasal）或額骨（Frontal），但根據系統發生樹的重建，其被歸類在Rhinocerotina和Rhinoceroti當中，參考此類群的祖徵，島犀很可能只有單支角（即只有鼻角而沒有額角）。

根據牙齒大小估計，早坂島犀平均重量約為1263公斤，上下限落在1018-1670公斤間，而根據橈骨大小估計的重量則為1306公斤。透過和現生犀牛前肢大小的比較，推測早坂島犀的身高約為1.31米，體型和現生的蘇門答臘犀牛相近，且略大於同屬的菲律賓島犀。

系統發生樹
-----

Antoine等人於2022年重建的犀亞科(Rhinocerotinae)系統發生樹顯示島犀屬和雙角犀與獨角犀關係較近：


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|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |
| --- | --- |
|   | 南美貘 *Tapirus terrestris* |
|   |
|   | †驚異犀貘 *Hyrachyus eximius* |
|   |

 |
|   |
|   | †*Trigonias osborni（英语：）* |
|   |

 |
|   |
|   | †*Ronzotherium filholi（英语：）* |
|   |
|   | 

|  |  |
| --- | --- |
| †板齒犀亞科 Elasmotheriinae（英语：） | †西方副跑犀 *Subhyracodon occidentalis* |
|   |
| 犀亞科 Rhinocerotinae（英语：） | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 犀族 Rhinocerotini（英语：） | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 獨角犀亞族 Rhinocerotina | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 黑犀Diceroti | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |
| --- | --- |
|   | 白犀 *Ceratotherium simum* |
|   |
|   | 黑犀 *Diceros bicornis* |
|   |

 |
|   |
|   | †紐氏白犀 *Ceratotherium neumayri（英语：）* |
|   |

 |
|   |
|   | †古老披毛犀 *Coelodonta antiquitatis* |
|   |

 |
|   |
|   | †*"Stephanorhinus" megarhinus（英语：）* |
|   |

 |
|   |
|   | † *Stephanorhinus etruscus* |
|   |

 |
|   |
|   | †*"Dihoplus" pikermiensis（英语：）* |
|   |

 |
|   |
|   | †*Dihoplus schleiermacheri（英语：）* |
|   |

 |
|   |
| Rhinoceroti | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |
| --- | --- |
|   | †*Lartetotherium sansaniense（英语：）* |
|   |
|   | †*Gaindatherium browni（英语：）* |
|   |

 |
|   |
|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 雙角犀屬 Dicerorhinus | 

|  |  |
| --- | --- |
|   | 蘇門答臘犀 *Dicerorhinus sumatrensis* |
|   |
|   | †*Dicerorhinus fusuiensis（英语：）* |
|   |

 |
|   |
| 獨角犀屬 Rhinoceros | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |
| --- | --- |
|   | †*Rhinoceros platyrhinus（英语：）* |
|   |
|   | †*Rhinoceros kendengindicus* |
|   |

 |
|   |
|   | 印度犀 *Rhinoceros unicornis* |
|   |

 |
|   |
|   | †中國犀 *Rhinoceros sinensis* |
|   |

 |
|   |
|   | 爪哇犀 *Rhinoceros sondaicus* |
|   |

 |
|   |

 |
|   |
| †島犀屬 **Nesorhinus** | 

|  |  |
| --- | --- |
|   | †菲律賓犀 ***Nesorhinus philippinensis*** |
|   |
|   | †早坂犀 ***Nesorhinus hayasakai*** |
|   |

 |
|   |

 |
|   |

 |
|   |

 |
|   |
| †遠角犀亞族 Teleoceratina | 

|  |  |
| --- | --- |
|   | †矮腳犀 *Brachypotherium perimense* |
|   |
|   | †遠角犀 *Teleoceras fossiger* |
|   |

 |
|   |

 |
|   |
| †無角犀亞族 Aceratheriini | 

|  |  |
| --- | --- |
|   | †奇角犀 *Alicornops simorrense（英语：）* |
|   |
|   | 

|  |  |
| --- | --- |
|   | †*Hoploaceratherium tetradactylum* |
|   |
|   | †無角犀 *Aceratherium incisivum* |
|   |

 |
|   |

 |
|   |

 |
|   |
|   | †近無角犀 *Plesiaceratherium mirallesi（英语：）* |
|   |

 |
|   |

 |
|   |

 |
|   |

†表示已滅絕

時空分布
----

島犀屬主要分布於早更新世至中更新世的臺灣與菲律賓。過去對於更新世時期東南亞生物擴散的路徑有三種主要的假說，包含

（1）透過冰河期暴露的巽他陸棚，從西瓦立克擴散（西瓦-馬來路徑），

（2）從中國經泰國往印度尼西亞擴散(中華-馬來路徑)和

（3）從臺灣經菲律賓跨越海洋屏障，往西方與南方擴散。

透過親緣關係重建與古生物地理的分析顯示，島犀、獨角犀(Rhinoceros)和雙角犀(Dicerorhinus)的共同祖先可能源自亞洲大陸，島犀屬的共同祖先較有可能源自東南亞或南亞等區域而非巽他地區，且較高機率是由台灣跨海擴散分布至菲律賓（即上述（3）假說）。現生的亞洲犀牛具有穿越河流和海上走廊（marine corridors）的能力，而在中新世或更新世海平面下降約120公尺的最大冰期，台灣和菲律賓呂宋島的最近距離約只有57公里。因此，考量現生犀牛的游泳能力、冰期的海平面下降和盛行向南吹的東南亞風，島犀在那時游過呂宋海峽向南擴散並非不可能。

菲律賓島犀的體重較輕、四肢較為纖細，這可能是島嶼侏儒化造成的結果。這樣的演化現象是否也發生在台灣的島犀仍是未知。

古生態學
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左鎮之早坂犀化石出土層位屬於崎頂層，屬於砂頁岩互層之濱海相沉積，地質年代約為距今99萬至46萬年前（早更新世到中更新世）。透過崎頂層出土之化石得知早坂犀的棲息環境可能為開放草原，生態系中的動物也被合稱為左鎮動物群，當中有猛瑪象、四不像、野豬、金絲猴、似劍齒虎、豐玉姬鱷等大型動物和早坂島犀一同生存。

參考資料
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2. 1 2 3 4 5 6 7 8 9  Antoine, Pierre-Olivier; Reyes, Marian C; Amano, Noel; Bautista, Angel P; Chang, Chun-Hsiang; Claude, Julien; De Vos, John; Ingicco, Thomas.. Zoological Journal of the Linnean Society. 2022, **194** (2): 416-430. doi:10.1093/zoolinnean/zlab009.
3. 1 2  Hayasaka, I.. Taiwan Tikagu Kizi. 1942, **13** (4): 95-109.
4. ↑  Saito, Hitoshi.. Journal of Geography. 1926, **38** (454): 741-742  [2023-03-29]. （原始内容存档于2023-03-29）.
5. ↑  Hoogerwerf, A.. Leiden: Brill. 1970.  请检查`|access-date=`中的日期值 (帮助); 使用`|accessdate=`需要含有`|url=` (帮助)
6. ↑  Konwar, P.; Saikia, M.K.; Saikia, P.K.. Journal of Threatened Taxa (1). 2009: 457-560  [2023-03-29]. doi:10.11609/JoTT.o1640.457-60. （原始内容存档于2023-03-29）.
7. ↑  魏, 國彥.. 經濟部中央地質調查所特刊. 2007  [2023-03-29]. （原始内容存档于2023-03-29）.
8. ↑  Kawamura, Ai; Chang, Chun-Hsiang; Kawamura, Yoshinari.. Quaternary International. 2016, **397**: 117-135  [2023-03-29]. doi:10.1016/j.quaint.2015.06.044. （原始内容存档于2023-03-29）.
9. ↑  Ito, Ai; Aoki, Riosuke; Hirayama, Ren; Yoshida, Masataka; Kon, Hiroo; Endo, Hideki.. Paleontological Research. 2018, **22** (2): 150-155  [2023-03-29]. doi:10.2517/2017PR016. （原始内容存档于2023-03-29）.
10. ↑  Tsai, Cheng-Hsiu; Tseng, Zhijie Jack.. Papers in Palaeontology. 2022, **8** (5): e1469  [2023-03-29]. doi:10.1002/spp2.1469. （原始内容存档于2023-03-29）.