據(jù)國(guó)外媒體報(bào)道,，在巴西一個(gè)小鎮(zhèn)，研究人員發(fā)現(xiàn)了距今7000萬年的鱷魚化石,，有著狗一樣頭和巨大的牙齒,，被命名為Pissarrachampsa sera。早先由一名市政工人在米納斯吉拉斯發(fā)現(xiàn),，科學(xué)家認(rèn)為在白堊紀(jì)這種鱷魚能夠捕食恐龍,，回到恐龍時(shí)代的末期，這次發(fā)現(xiàn)的鱷魚化石奇怪的頭骨讓人聯(lián)想到它應(yīng)該屬于已經(jīng)滅絕的波羅鱷血統(tǒng),。
研究牽頭人,，魁北克省麥吉爾大學(xué)的Hans Larsson說，盡管現(xiàn)代的兩棲鱷魚有著扁平的頭,，但是這一新的發(fā)現(xiàn)給了我們新的啟示：應(yīng)該去探尋這種已經(jīng)滅絕的奇怪種群——波羅鱷,，它們有著高大的類似于狗一樣的骨頭和犬齒，四肢較長(zhǎng),。它們或許和現(xiàn)代的野狗有某種關(guān)系,。
根據(jù)它們的牙齒的數(shù)量和大小，研究者稱,，這些食肉鱷魚以15到20英尺的動(dòng)物為食——而這種體積的動(dòng)物包括恐龍和同類的一些鱷魚,。它們可能是利用自己立體的視覺去跟蹤獵物，而不是像現(xiàn)在的鱷魚一樣去爭(zhēng)奪食物,，甚至是用細(xì)長(zhǎng)的四肢跑動(dòng)追擊,。一幅由Larsson博士繪制的素描圖或許能夠顯示出這一物種是如何捕食的。
盡管從外形上來看,，它們更與恐龍相像而不是現(xiàn)代的鱷魚,，但是頭骨化石卻能夠證明一些那個(gè)時(shí)代鱷魚的基本特征。包括擁有發(fā)育良好的繼發(fā)腭,、嵌齒,、顱骨空間以及粗糙的骨頭表面等,。
最近，CT掃描揭示了這一化石的一些細(xì)節(jié),，例如它的大腦大小和規(guī)模,，聽覺能力。波羅鱷有著鮮明的解剖學(xué)特點(diǎn),，例如牙齒稀少,，向前的鼻孔和衍生的下巴閉合肌肉附件。
通過和以往發(fā)現(xiàn)的波羅鱷種類相對(duì)比,，研究者發(fā)現(xiàn),，這一新發(fā)現(xiàn)化石在形態(tài)上有巨大的差異。研究者試圖對(duì)這一化石的腦部結(jié)構(gòu)進(jìn)行數(shù)字還原,。(生物谷 Bioon.com)
doi:10.1371/journal.pone.0021916
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A New Baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the Late Cretaceous of Brazil and the Phylogeny of Baurusuchidae
Felipe C. Montefeltro, Hans C. E. Larsson, Max C. Langer
Background
Baurusuchidae is a group of extinct Crocodyliformes with peculiar, dog-faced skulls, hypertrophied canines, and terrestrial, cursorial limb morphologies. Their importance for crocodyliform evolution and biogeography is widely recognized, and many new taxa have been recently described. In most phylogenetic analyses of Mesoeucrocodylia, the entire clade is represented only by Baurusuchus pachecoi, and no work has attempted to study the internal relationships of the group or diagnose the clade and its members.
Methodology/Principal Findings
Based on a nearly complete skull and a referred partial skull and lower jaw, we describe a new baurusuchid from the Vale do Rio do Peixe Formation (Bauru Group), Late Cretaceous of Brazil. The taxon is diagnosed by a suite of characters that include: four maxillary teeth, supratemporal fenestra with equally developed medial and anterior rims, four laterally visible quadrate fenestrae, lateral Eustachian foramina larger than medial Eustachian foramen, deep depression on the dorsal surface of pterygoid wing. The new taxon was compared to all other baurusuchids and their internal relationships were examined based on the maximum parsimony analysis of a discrete morphological data matrix.
Conclusion
The monophyly of Baurusuchidae is supported by a large number of unique characters implying an equally large morphological gap between the clade and its immediate outgroups. A complex phylogeny of baurusuchids was recovered. The internal branch pattern suggests two main lineages, one with a relatively broad geographical range between Argentina and Brazil (Pissarrachampsinae), which includes the new taxon, and an endemic clade of the Bauru Group in Brazil (Baurusuchinae).
