小柯机器人

科学家发现一个来自南极白垩纪晚期的巨型软壳蛋
2020-06-22 10:52

美国德克萨斯大学奥斯汀分校Julia A. Clarke、Lucas J. Legendre等研究人员合作发现一个来自南极白垩纪晚期的巨型软壳蛋。2020年6月17日,《自然》杂志在线发表了这项成果。

研究人员报告了一种在南极白垩纪晚期(大约6800万年前)的近海海洋沉积物中发现的新型蛋。它的体积超过了所有非禽类恐龙蛋,并且在结构上有所不同。尽管大象鸟的蛋稍大一些,但其蛋壳却厚约五倍,并显示出坚固的棱柱层和复杂的孔结构。
 
相比之下,新的化石明显地塌陷并折叠,呈现出一个薄的蛋壳,其具有分层结构,缺少棱柱层和明显的气孔,与大多数现存的蜥蜴和蛇(鳞龙超目)相似。下蛋动物的身份尚不清楚,但这些保存的形态与附近发现的沧龙(大型海洋鳞龙超目)的骨骼遗骸相符。它们与已知相似大小等级的恐龙蛋形态不一致。
 
对259种鳞龙超目及外群的性状进行系统进化分析表明,这个蛋属于至少7米长的个体,据推测是一种巨大的海洋爬行动物,其所在的所有进化分支被认为是活产生殖。这样大的蛋却有相对较薄的蛋壳可能反映出与身体形状等相关的限制因素,也就是说这些外形“残留”的蛋需要立即被孵化。
 
据悉,蛋的大小和结构反映了对脊椎动物生殖和生命周期特征的重要限制。在现存的羊膜动物中,三分之二以上产卵。在中生代时代(大约2.5亿到6500万年前),动物的体型达到了极限。但是,已知最大的蛋属于最近灭绝的大象鸟,它比历史上最近的非禽类恐龙和巨型海洋爬行动物晚了约6600万年。
 
附:英文原文

Title: A giant soft-shelled egg from the Late Cretaceous of Antarctica

Author: Lucas J. Legendre, David Rubilar-Rogers, Grace M. Musser, Sarah N. Davis, Rodrigo A. Otero, Alexander O. Vargas, Julia A. Clarke

Issue&Volume: 2020-06-17

Abstract: Egg size and structure reflect important constraints on the reproductive and life-history characteristics of vertebrates1. More than two-thirds of all extant amniotes lay eggs2. During the Mesozoic era (around 250 million to 65 million years ago), body sizes reached extremes; nevertheless, the largest known egg belongs to the only recently extinct elephant bird3, which was roughly 66 million years younger than the last nonavian dinosaurs and giant marine reptiles. Here we report a new type of egg discovered in nearshore marine deposits from the Late Cretaceous period (roughly 68 million years ago) of Antarctica. It exceeds all nonavian dinosaur eggs in volume and differs from them in structure. Although the elephant bird egg is slightly larger, its eggshell is roughly five times thicker and shows a substantial prismatic layer and complex pore structure4. By contrast, the new fossil, visibly collapsed and folded, presents a thin eggshell with a layered structure that lacks a prismatic layer and distinct pores, and is similar to that of most extant lizards and snakes (Lepidosauria)5. The identity of the animal that laid the egg is unknown, but these preserved morphologies are consistent with the skeletal remains of mosasaurs (large marine lepidosaurs) found nearby. They are not consistent with described morphologies of dinosaur eggs of a similar size class. Phylogenetic analyses of traits for 259 lepidosaur species plus outgroups suggest that the egg belonged to an individual that was at least 7 metres long, hypothesized to be a giant marine reptile, all clades of which have previously been proposed to show live birth6. Such a large egg with a relatively thin eggshell may reflect derived constraints associated with body shape, reproductive investment linked with gigantism, and lepidosaurian viviparity, in which a ‘vestigial’ egg is laid and hatches immediately7.

DOI: 10.1038/s41586-020-2377-7

Source: https://www.nature.com/articles/s41586-020-2377-7

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:43.07
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html


本期文章:《自然》:Online/在线发表

分享到:

0