Abstract：
The late Miocene Dromornis stirtoni is the largest of the giant flightless dromornithid birds. Here, we studied 22 long bones (femora, tibiotarsi, tarsometatarsi) of D. stirtoni to assess its osteohistology to deduce various aspects of its life history. Our results show that D. stirtoni took several years (likely, more than a decade), to reach adult body size, after which its growth rate slowed down, and skeletal maturity occurred. This growth strategy differs from that of its Pleistocene relative, Genyornis newtoni, which experienced faster rates of growth to reach adult body size. We propose that these mihirung birds, separated by millions of years, each responded to the prevailing environmental conditions of the time, by selecting for different growth strategies, with D. stirtoni having an extreme K-selected life history strategy. The presence of medullary bone permitted the identification of female D. stirtoni specimens, and its presence in some bones lacking an OCL layer showed sexual maturity preceded its formation. We postulate that while G. newtoni had a somewhat greater reproductive potential than D. stirtoni, it remained far less than that observed in the extant emu (Dromaius novaehollandiae). Genyornis newtoni survived into the late Pleistocene alongside extant emus and overlapped the arrival of the first humans in Australia, but the former species shortly thereafter became extinct while emus remain prolific.
摘要：
上新世晚期Dromornisstisttoni是最大的不会飞行的巨鸟。这里,我们研究了22块长骨(股骨，tibiotarsi,stisttoni的tarsometatarsi）评估其骨组织学，以推断其生活史的各个方面。我们的结果表明，斯特顿尼花了几年时间(很可能，十多年)，达到成人体型，之后其增长速度放缓，和骨骼成熟发生。这种增长策略不同于其更新世亲戚的增长策略，GenyornisNewtoni,经历了更快的生长速度达到成人的体型。我们建议这些mihrung鸟，相隔数百万年，每个人都对当时的环境条件做出了回应，通过选择不同的增长策略，D.斯蒂托尼有一个极端的K选择生活史策略。髓质骨的存在允许鉴定女性D.stisttoni标本，在一些缺乏OCL层的骨骼中，它的存在表明性成熟先于其形成。我们推测，尽管G.newtoni的生殖潜力比D.stisttoni大，它仍然远远低于现存的emu（Dromaiusnovaehollandiae）。Genyornisnewtoni与现存的emus一起存活到更新世晚期，并与第一批人类在澳大利亚的到来重叠，但是前一种物种此后不久就灭绝了，而em仍然多产。
