An early tetrapod from 'Romer's Gap'

The fossil record of early tetrapods has been increased recently by new finds from the Devonian period and mid-late Early Carboniferous period. Despite this, understanding of tetrapod evolution has been hampered by a 20-million-year gap ('Romer's Gap') that covers the crucial, early period when many key features of terrestrial tetrapods were acquired. Here I describe the only articulated skeleton of a tetrapod, Pederpes, yet found from the Tournaisian epoch (354-344 million years ago (Myr)). The new taxon includes a pes with five robust digits, but a very small, possibly supernumerary digit preserved on the manus suggests the presence of polydactyly. Polydactylous early tetrapods may have survived beyond the end of the Devonian and pentadactyly cannot be assumed for the pes. However, the pes has characteristics that distinguish it from the paddle-like feet of the Devonian forms and resembles the feet of later, more terrestrially adapted Carboniferous forms. Pederpes is the earliest-known tetrapod to show the beginnings of terrestrial locomotion and was at least functionally pentadactyl. With its later American sister-genus, Whatcheeria, it represents the next most primitive tetrapod clade after those of the Late Devonian, bridging the temporal, morphological and phylogenetic gaps that have hitherto separated Late Devonian and mid-Carboniferous tetrapod faunas.     

Inner ear of the coelacanth fish Latimeria has tetrapod affinities

Auditory reception in elasmobranchs, teleosts and amphibians may be mediated by various inner-ear sensory epithelia 1–3, including the basilar papilla, which seems to be the precursor of the cochlea in mammals. The origin of the basilar papilla remains a major unsolved problem for understanding the evolution of hearing in terrestrial vertebrates4–6. Study of living species indicates that the basilar papilla is a unique feature of tetrapods 6,7, but palaeonto-logical data indicate that this epithelium as well as a middle ear, is already present in crossopterygian fish 8–10. However, no basilar papilla has been found in the only living crossopterygian species, the coelacanth Latimeria chalumnae 11. I have re-examined the inner ear of adult and embryonic Latimeria and find a membranous specialization which resembles in structure, position and innerva-tion pattern the basilar papilla of tetrapods, in particular amniotes. No epithelium comparable to the basilar papilla was found in lungfish. I suggest that the basilar papillae of Latimeria and tetrapods are homologous and evolved only once in their common ancestor.     

Three-dimensional limb joint mobility in the early tetrapod Ichthyostega

The origin of tetrapods and the transition from swimming to walking was a pivotal step in the evolution and diversification of terrestrial vertebrates. During this time, modifications of the limbs—particularly the specialization of joints and the structures that guide their motions—fundamentally changed the ways in which early tetrapods could move. Nonetheless, little is known about the functional consequences of limb anatomy in early tetrapods and how that anatomy influenced locomotion capabilities at this very critical stage in vertebrate evolution. Here we present a three-dimensional reconstruction of the iconic Devonian tetrapod Ichthyostega and a quantitative and comparative analysis of limb mobility in this early tetrapod. We show that Ichthyostega could not have employed typical tetrapod locomotory behaviours, such as lateral sequence walking. In particular, it lacked the necessary rotary motions in its limbs to push the body off the ground and move the limbs in an alternating sequence. Given that long-axis rotation was present in the fins of tetrapodomorph fishes, it seems that either early tetrapods evolved through an initial stage of restricted shoulder and hip joint mobility or that Ichthyostega was unique in this respect. We conclude that early tetrapods with the skeletal morphology and limb mobility of Ichthyostega were unlikely to have made some of the recently described Middle Devonian trackways.     

A Devonian tetrapod-like fish and the evolution of the tetrapod body plan

The relationship of limbed vertebrates (tetrapods) to lobe-finned fish (sarcopterygians) is well established, but the origin of major tetrapod features has remained obscure for lack of fossils that document the sequence of evolutionary changes. Here we report the discovery of a well-preserved species of fossil sarcopterygian fish from the Late Devonian of Arctic Canada that represents an intermediate between fish with fins and tetrapods with limbs, and provides unique insights into how and in what order important tetrapod characters arose. Although the body scales, fin rays, lower jaw and palate are comparable to those in more primitive sarcopterygians, the new species also has a shortened skull roof, a modified ear region, a mobile neck, a functional wrist joint, and other features that presage tetrapod conditions. The morphological features and geological setting of this new animal are suggestive of life in shallow-water, marginal and subaerial habitats.     

A very faint core-collapse supernova in M85

An anomalous transient in the early Hubble-type (S0) galaxy Messier 85 (M85) in the Virgo cluster was discovered by Kulkarni et al. on 7 January 2006 that had very low luminosity (peak absolute R-band magnitude M(R) of about -12) that was constant over more than 80 days, red colour and narrow spectral lines, which seem inconsistent with those observed in any known class of transient events. Kulkarni et al. suggest an exotic stellar merger as the possible origin. An alternative explanation is that the transient in M85 was a type II-plateau supernova of extremely low luminosity, exploding in a lenticular galaxy with residual star-forming activity. This intriguing transient might be the faintest supernova that has ever been discovered.     

短跑"专项练习"教学新探

在短跑的训练项目中,为了掌握短跑技术,发展速度,经常选用三项跑的“专项练习”,即小步跑、高抬腿跑、后蹬腿跑,几十年来一直被列为短跑教学与训练的主要手段,特别是对于刚参加训练的新运动员来说,几乎成了必不可少的作业,不断练习,反复加时,加量,那么它到底起什么作用？本文就这个问题提出自己的看法,并全面的分析了“专项练习”的技术作用,提出改进方法的建议。     

Tetrapod-like middle ear architecture in a Devonian fish

Few fossils show the incipient stages of complex morphological transformations. For example, the earliest stages in the remodelling of the spiracular tract and suspensorium (jaw suspension) of osteolepiform fishes into the middle ear of tetrapods have remained elusive. The most primitive known tetrapods show a middle ear architecture that is very different from osteolepiforms such as Eusthenopteron, with little indication of how this transformation took place. Here we present an analysis of tetrapod middle ear origins that is based on a detailed study of Panderichthys, the immediate sister taxon of tetrapods. We show that the spiracular region is radically transformed from osteolepiforms and represents the earliest stages in the origin of the tetrapod middle ear architecture. The posterior palatoquadrate of Panderichthys is completely tetrapod-like and defines a similarly tetrapod-like spiracular tract. The hyomandibula has lost its distal portion, representing a previously unrecognized advance towards a stapes-like morphology. This spiracular specialization suggests that the middle ear of early tetrapods evolved initially as part of a spiracular breathing apparatus.     

高等学校加强专业建设的探索与实践

高等学校如何加强专业建设是摆在我们面前的十分紧迫的任务。本文总结了我校学科专业建设方面的具体做法和主要经验，必将有利于今后进一步优化专业设置，加强专业建设，提高教学质量。     

在专业课教学中培养学生创新能力的一点尝试

在专业课教学中培养学生创新能力的具体做法有：激发学生创新愿望，教学内容有一定开放度；注意培养学生的问题意识，适量采用提问式讲课方式；珍惜、培养和张扬学生的个性。     

超低和极低出生体重儿早期呼吸系统并发症临床分析

目的探讨超低和极低体重新生儿早期呼吸系统并发症的发生情况．认识NICU呼吸管理的重要性。方法对102例超低和极低出生体重儿临床资料进行回顾分析，结果呼吸暂停发生率为69．61％．其中15．49％表现为梗阻性呼吸暂停。新生儿呼吸窘迫综合征（NRDS）发生率48．04％，肺炎占30．39％．痊愈率81．37％。体重越低．RDS、呼吸暂停、肺炎的发生率越高（P〈0．01）。结论对超低和极低出生体重儿密切监护，加强呼吸管理．是救治早产儿的重要环节，可提高成活率和生存质量。     

图象编码系统中解码的唯一性和即时性探讨

一个图象编码系统由编码器、信道、解码器三个部分组成．通过编码,降低了数字图象对存储量的要求,缩短了图象传输所需的时间,但这是以牺牲压缩与解压的时间为代价的．解码的唯一性和即时性在图象处理过程中不容忽视．本文给出了解码的唯一性和即时性的概念,举例讨论了解码过程中遇到的唯一性和即时性问题以及它们对解码结果的影响．     

职高体育教学探析

运用问卷调查法、访问法对金华第二职业高中97级学生进行调查访问，对反应职业高中学生特点的诸多问题的答案进行数理统计，分析结果，并根据所得结论与浙江省中等职业技术学校体育试用教材、结合学生体育态度拟定教学计划，在三年的实践教学过程中基本达到预期效果．