Tetrapod classification

The traditional palaeontological view that the mammals separated from the 'reptiles' before the origin of all other living amniotes is challenged. A radical alternative hypothesis, based on a character analysis of living tetrapods, is elaborated in which birds are considered the sister-group of mammals, crocodiles the sister-group of those two, chelonians the sister-group of those three, and squamates + Sphenodon the sister-group of those four. The living Amphibia are hypothesized to form a natural group and to be the sister-group of the Amniota. Further, I conclude that the Anapsida, Diapsida and Synapsida are paraphyletic or grade groups and no unique statements can be made about their structure.     

道德规范与动物学

道德规范教育如今已经提升到了专业的水平。因此在专业领域里 (例如工程学和医学 ) ,道德规范教育应作为必修课程。但至今很多理科课程仍没有把它列为必修课。这就给我们提出了一个疑问 :理科是专业课程吗 ?如果是的话 ,那么科学家例如动物学家需不需要熟悉他们职责范围内的道德准则和尺度呢 ?动物学家对医学上暴露的一些问题很敏感———包括我们怎样对待动物以及我们怎样或者是否开展基因工程。但是从道德观念上来看 ,道德规范教育的实行是比这两件事更实际的。这篇论文就以上观点进行了进一步的论述 ,并且对把道德规范教育加入理科课程的需求和可能性做了评估。在现实社会里 ,动物科学家是被敬重的专业人士。他们每天面对着许多极可能影响我们生活环境的决策。有鉴于此 ,动物科学家必需掌握道德规范的标准 ,并且有能力做出与此相符合的决策。这才能使我们在动物学的教学过程中确保动物学家持续稳定的专业发展方向     

Tetrapod Footprint Biostratigraphy and Biochronology

Tetrapod footprints have a fossil record in rocks of Devonian-Neogene age. Three principal factors limit their use in biostratigraphy and biochronology (palichnostratigraphy): invalid ichnotaxa based on extramorphological variants, slow apparent evolutionary turnover rates and facies restrictions. The ichnotaxonomy of tetrapod footprints has generally been oversplit, largely due to a failure to appreciate extramorphological variation. Thus, many tetrapod footprint ichnogenera and most ichnospecies are useless phantom taxa that confound biostratigraphic correlation and biochronological subdivision. Tracks rarely allow identification of a genus or species known from the body fossil record. Indeed, almost all tetrapod footprint ichnogenera are equivalent to a family or a higher taxon (order, superorder, etc.) based on body fossils. This means that ichnogenera necessarily have much longer temporal ranges and therefore slower apparent evolutionary turnover rates than do body fossil genera. Because of this, footprints cannot provide as refined a subdivision of geological time as do body fossils. The tetrapod footprint record is much more facies controlled than the tetrapod body fossil record. The relatively narrow facies window for track preservation, and the fact that tracks are almost never transported, redeposited or reworked, limits the facies that can be correlated with any track-based biostratigraphy.

A Devonian-Neogene global biochronology based on tetrapod footprints generally resolves geologic time about 20 to 50 percent as well as does the tetrapod body fossil record. The following globally recognizable time intervals can be based on the track record: (1) Late Devonian; (2) Mississippian; (3) Early-Middle Pennsylvanian; (4) Late Pennsylvanian; (5) Early Permian; (6) Late Permian; (7) Early-Middle Triassic; (8) late Middle Triassic; (9) Late Triassic; (10) Early Jurassic; (11) Middle-Late Jurassic; (12) Early Cretaceous; (13) Late Cretaceous; (14) Paleogene; (15) Neogene. Tetrapod footprints are most valuable in establishing biostratigraphic datum points, and this is their primary value to understanding the stratigraphic (temporal) dimension of tetrapod evolution.     

Tetrapod Ichnofacies: A New Paradigm

We recognize three fundamental terms in ichnology: (1) ichnoassemblage, which is an assemblage of ichnofossils conceptually equivalent to an assemblage of body fossils; (2) ichnocoenosis, which is a trace fossil assemblage produced by a biological community that can be characterized by morphological criteria; and (3) ichnofacies, which refers to recurrent ichnocoenoses that represent a significant portion of Phanerozoic time. There are two different kinds of ichnofacies, ethoichnofacies (mostly invertebrate ichnofacies) and biotaxonichnofacies (mostly tetrapod ichnofacies). Nonmarine invertebrate ichnologists now recognize five archetypal ichnofacies (Mermia, Skolithos, Scoyenia, Coprinisphaera, Psilonichnus) to which we add the Octopodichnus ichnofacies. We propose a coherent and consistent classification and nomenclature for tetrapod ichnofacies. We name five archetypal vertebrate ichnofacies for nonmarine environments: Chelichnus, Grallator, Brontopodus, Batrachichnus and Characichnos ichnofacies.     

动物学教学改革

动物学是高等师范专科学校生物教育专业的一门重要的基础课 ,也是一门实践性很强的学科 ,在生物专业基础课中的地位一直牢不可破。在素质教育越来越受到重视的今天 ,要提高学生的全面素质 ,如何使动物学教学适应当前教育改革的需要 ,为培养开拓型、创造型的教育人才服务 ,是摆在高校生物系教师面前的重要课题。多年来 ,笔者在这门课程的教学中 ,认识到重视理论 ,加强实践 ,着重培养能力 ,对学生的成长至关重要。1　激发和培养学生学习兴趣兴趣是学习的最佳动力 ,是掌握和运用科学知识与技能 ,开阔眼界 ,增强能力的必要条件。培养学生学习动…     

动物学野外实习的改革与实践

自1996～2006年的11年间,共指导11届本科生的动物学野外实习。在实习中不断发现问题,并进行了改革实践,将实习时间由4月改至7月,由以往的2天延长为2周;实习地点由动物园、居民区或海边更换到热带雨林;教学方法由教学生认识物种到教学生自己学会检索物种及练习初步的野外观察研究方法;将动物学野外实习作为一门单独课程,严格规范地进行考核、总结等各个环节的管理。通过改革的一些探索,使动物学野外实习的教学效果有显著的改善。     

Tetrapod Limblessness: Evolution and Functional Corollaries

Multiple lines of tetrapods show reduced limbs or their loss.Such patterns are in diverse lines associated with multipleother characteristics. Only bodily elongation represents a commondenominator. Analysis suggests that elongation for traverseof crevices in a sheltering environment and for the utilizationof undulatory locomotion may have provided the initial selectiveadvantage to the system. Limb reduction would then have beensecondary. This hypothesis leads to several interesting implicationsabout the process of diversification in tetrapods.     

The Adaptive Significance of Tetrapod Gait Selection

At the slow walk tetrapods avoid lateral couplets gaits to minimizesupport by ipsilateral bipods. Most of them use the lateralsequence because tripods then make larger triangles than forthe diagonal sequence. Of the running symmetrical gaits thesingle foots (in each sequence) permit the smoothest and fastesttravel without suspensions. The trot and pace allow two legsto thrust in unison, the former giving the most stability toanimals not placing the feet well under the body and the latteravoiding interference for long legged runners. The bound andhalf bound are most used by small agile mammals for bursts ofspeed and for maneuvering on rough terrain by a series of leaps.Such animals use the extended suspension. Large cursors on openterrain usually select the shorter more economical, gatheredsuspension. The fastest runners use both suspensions to gainlong strides. At moderate speed the transverse gallop has theadvantages over the rotary gallop that both bipods and tripodsare more stable and that interference may be avoided. At highspeed using both suspensions, none of these advantages pertains.The rotary gallop may then increase maneuverability.     

Tetrapod Footprints From the Upper Carboniferous of China

We documented tetrapod footprints from Baode, Shanxi, China identified as aff. Dimetropus. These are the first record of carboniferous tetrapods from what was the North China block, a microplate isolated from the Pangean nucleus during the Carboniferous.     

Application of magnetic resonance imaging in zoology

Magnetic resonance imaging (MRI) is a noninvasive imaging technique that today constitutes one of the main pillars of preclinical and clinical imaging. MRI’s capacity to depict soft tissue in whole specimens ex vivo as well as in vivo, achievable voxel resolutions well below (100 μm)³, and the absence of ionizing radiation have resulted in the broad application of this technique both in human diagnostics and studies involving small animal model organisms. Unfortunately, MRI systems are expensive devices and have so far only sporadically been used to resolve questions in zoology and in particular in zoomorphology. However, the results from two recent studies involving systematic scanning of representative species from a vertebrate group (fishes) as well as an invertebrate taxon (sea urchins) suggest that MRI could in fact be used more widely in zoology. Using novel image data derived from representative species of numerous higher metazoan clades in combination with a comprehensive literature survey, we review and evaluate the potential of MRI for systematic taxon scanning. According to our results, numerous animal groups are suitable for systematic MRI scanning, among them various cnidarian and arthropod taxa, brachiopods, various molluscan taxa, echinoderms, as well as all vertebrate clades. However, various phyla in their entirety cannot be considered suitable for this approach mainly due to their small size (e.g., Kinorhyncha) or their unfavorable shape (e.g., Nematomorpha), while other taxa are prone to produce artifacts associated either with their biology (e.g., Echiura) or their anatomy (e.g., Polyplacophora). In order to initiate further uses of MRI in zoology, we outline the principles underlying various applications of this technique such as the use of contrast agents, in vivo MRI, functional MRI, as well as magnetic resonance spectroscopy. Finally, we discuss how future technical developments might shape the use of MRI for the study of zoological specimens.     

从系统动物学的诞生和发展探讨现代动物学研究的特点

新技术新理论的不断发展推动着系统动物学的诞生,其迅速发展也说明了动物学领域宏观研究和微观研究在更高程度上相互渗透的特点。     

《动物学》课程教学探讨

动物学是生物科学专业重要的专业基础课。结合自身教学实践,对动物学在专业课程体系和学生知识体系中地位进行再认识,并就该课程教学内容的构成、主要线索,教学过程,以及如何在教学过程中结合人文素质教育,拓宽学生视野,提高学生综合素质进行探讨。     

What plant ecologists can learn from zoology

Biology, like all sciences, is increasingly compartmentalized. This helps us to interact more easily with fellow specialists, but also tends to shield us from useful cross-fertilization with other fields. For example, plant and animal ecologists have established largely distinct research traditions over the years. Botanists studying population ecology, interspecific competition, and ecological and evolutionary aspects of sexual reproduction can benefit by importing more of the conceptual advances occurring in zoology (and vice versa). Botanists working on plant-animal interactions have a similar opportunity to shed light on their questions by learning more about the animals. For example, botanists studying pollination may be unaware of some modern advances in animal physiology and behaviour which undermine a typological view of pollination systems. Similarly, botanists studying loss of seeds to granivores may be unaware of details of animal behaviour that can cause granivores to benefit the plants in surprising ways. These examples illustrate how improved communication with zoology can enrich plant ecology. To remove barriers to communication we suggest some individual and collective actions that plant ecologists can take.     

Thinopus and a Critical Review of Devonian Tetrapod Footprints

Devonian tetrapod tracks and trackways can be recognized by three criteria: morphology of the manus and pes impressions that matches known Devonian tetrapod skeletal morphology, manus smaller than pes, and the alternating trackway pattern that results from lateral sequence walking in quadrupedal tetrapod locomotion. The first reported Devonian tetrapod track, named Thinopus antiquus, from Pennsylvania, is not a tetrapod track and is likely an impression of a fish coprolite(s). A critical review of the published Devonian track record indicates only three can be verified as produced by a tetrapod trackmaker—Genoa River, Australia; Easter Ross, Scotland; and Valentia Island, Ireland. The supposed tetrapod tracks from the Middle Devonian of the Zache?mie quarry, Poland, fail the criteria for identification as Devonian tetrapod tracks. Indeed, no convincing case has been made that the Zache?mie structures are tetrapod tracks. Instead, they are reinterpreted as fish nests/feeding traces (ichnogenus Piscichnus). The oldest Devonian tetrapod trackway is Givetian and this is the oldest record of a tetrapod, but the sparse record of Devonian tetrapod tracks is of no other biostratigraphic and little paleobiogeographic significance. Bona fide Devonian tetrapod tracks are from nonmarine facies, so they do not support a marginal marine origin of tetrapods. They indicate lateral sequence walking and pelvic-limb-propelled, fully terrestrial (subaerial) locomotion in freshwater environments by at least some Devonian tetrapods.     

Tetrapod postural shift estimated from Permian and Triassic trackways

Abstract:  The end-Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.