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Приветствую Вас, Гость · RSS 25.06.2017, 01:34

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Форум » Фауна и флора девона » Тетраподы » Новости и обсуждения
Новости и обсуждения
RelictДата: Воскресенье, 30.05.2010, 22:58 | Сообщение # 1
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http://devonian.ucoz.ru/publ/sensacija_v_polshe/1-1-0-3
Эту неизвестную амфибию в Польше пока еще не нашли? Новостей пока нет.
Кстати, есть документальный фильм о следах Польши. Можно визуально изучать следы... http://elvinosaurio.blogspot.com/2010....as.html
Еще статья http://www.pgi.gov.pl/pgi_en....sid=149

Реконструкции кистей тетраподов
http://www.nature.com/nature....F4.html
http://www.nature.com/news/2010/100106/full/news.2010.1.html
http://www.nature.com/nature/journal/v463/n7277/full/463040a.html
http://www.nature.com/nature/journal/v463/n7277/full/nature08623.html
 
dinovoprosДата: Воскресенье, 06.06.2010, 20:36 | Сообщение # 2
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Реконструкции кистей тетраподов

У ихтиостеги сохраняется восьмой палец, как у акантостеги?
 
UnenlagiaДата: Воскресенье, 06.06.2010, 21:51 | Сообщение # 3
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У ихтиостеги сохраняется восьмой палец, как у акантостеги?

У ихтиостеги 7 пальцев на задних лапах (передние вроде не найдены).


Не волим змајеве, али чини ми се да су ме воле!
 
RelictДата: Четверг, 19.08.2010, 12:57 | Сообщение # 4
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megaphone Еще одна новость! dwarf
П.Безносов написал, что сейчас готовит описание тиманского тетрапода из волгоградского горизонта, правда, по более полному скелету. На данный момент почти весь череп, нижняя челюсть и грудной пояс (клейтрум+клавикула) - всего более 50 экземпляров костей, в том числе сочлененных. Так вот, морфологически он четко ложится между тиктааликом и вентастегой. Хотя, с учетом последних польских находок (следовые дорожки из эйфеля), появляется все больше оснований рассматривать тиктаалика и Ко как боковую ветвь процесса тетраподизации. Статьи, как и названия еще нет. Примерно треть собранного материала находится в стадии препарировки (порода - доломитизированный известняк, снимается только химическим способом).
 
RelictДата: Вторник, 24.08.2010, 20:44 | Сообщение # 5
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Интересно, список фауны конца фамена Андреевки - 2 изменился! surprised

Раньше:
Actinopterygii: Moythomasia sp.
Onychodontida: Strunius sp.
Porolepiformes:Holoptychius nobilissimus.
Dipnoi: Andreyevichthys epitomus.
Osteolepididae: Chrysolepis orlensis.
Tristichopteridae: Eusthenodon sp. nov.
Megalichthyidae:Megistolepis sp.
Antiarcha: Remigolepis armata, Bothriolepis sp.
Holocephali: Unnamed eugeneodont.
Ischnacanthida: Onchus latus.
Acanthodida: Devononchus laevis,
Devononchus concinnus, Cheiracanthus sp.
Tetrapoda: Tulerpeton curtum.

Теперь:
Actinopterygii: Moythomasia sp.
Onychodontida: Strunius sp.
Porolepiformes:Holoptychius nobilissimus.
Dipnoi: Andreyevichthys epitomus.
Osteolepididae: Unnamed.
Tristichopteridae: Eusthenodon sp. nov.
Antiarcha: Remigolepis armata, Bothriolepis sp.
Holocephali: Unnamed eugeneodont.
Acanthodida: Devononchus laevis,
Devononchus concinnus, Cheiracanthus sp.
Tetrapoda: Tulerpeton curtum.

 
RelictДата: Суббота, 02.10.2010, 22:06 | Сообщение # 6
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В Туле есть краеведческий музей, в котором можно увидеть девонскую фауну и не только. Кто там был?

"В областном краеведческом музее открывается выставка "Природа тульского края". Здесь можно познакомиться с геологической историей территории Тульской области, палеонтологическими находками (следами давно исчезнувших растений и животных), с современными обитателями наших лесов и полей. Многие из представленных на выставке экспонатов уникальны, имеют историю с конца XIX-начала ХХ веков, а некоторые выставляются впервые.
Витрина с геологическими образцами рассказывает о богатстве тульских недр, хозяйственном значении залегающих в них пород и полезных ископаемых нашего края. Палеонтологические витрины покажут свидетелей событий, протекавших на тульской земле миллионы лет назад, когда ее покрывали палеозойские и мезозойские моря,. Это окаменевшие фрагменты древних плавунов, кораллы, похожие на пчелиные соты, причудливые раковины гигантских и крошечных древних моллюсков. А также слепок уникальной находки, сделанной в Тульской области, - лапки животного с названием тулерпетон. Здесь же можно посмотреть останки огромных зверей, свидетелей ледниковых периодов, которые бродили по области в каменном веке: мамонтов, зубров, гигантского большерогого оленя и шерстистого носорога.
Витрины, где представлена современная природа, расскажут о редких растениях, сохранившихся в заповедных уголках, познакомят с удивительными лишайниками и грибами, представят обширные коллекции насекомых.
Открытие состоится 18 мая в 12.00. музей расположен по адресу: Тула, ул. Советская, 68, тел.: 36-22-08, 36-78-83. Понедельник-суббота с 10.00 до 17.00, выходной - воскресенье."
http://www.tula.rodgor.ru/news/t_gorod_oblast/6835/

 
RelictДата: Суббота, 25.06.2011, 21:16 | Сообщение # 7
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Новость 1989г.
Discovery of the earliest-known tetrapod stapes
THE evolution of the middle ear is central to the discussion of how the first tetrapods adapted to life on land as well as their phylogeny. Here I report the discovery of the stapes of Acanthostega gunnari, from the Upper Devonian of east Greenland. This is the earliest tetrapod stapes so far described, and it throws new light on both these aspects of early tetrapod biology. It has been assumed that the common inheritance of all early tetrapods was a light, rod-like stapes associated with a temporal notch in the otic region that was thought to have supported a tympanum, or eardrum. The stapes would have conducted vibrations from the tympanum to the otic capsule. By contrast, the stapes of Acanthostega was stout with a broad distal ramus associated with the temporal notch. I suggest that the temporal notch of Acanthostega and other early tetrapods supported a spiracular opening rather than a tympanum, and that the stapes controlled palatal and spiracular movements in ventilation
http://www.nature.com/nature/journal/v347/n6288/pdf/347066a0.pdf

Новость 1990г.
Polydactyly in the earliest known tetrapod limbs
NEW specimens of the earliest known tetrapod limbs shows them to be polydactylous. The forelimb of Acanthostega has eight digits and the hindlimb of Ichthyostega has seven. Both of these come from the Upper Devonian of East Greenland, complementing the only other known Devonian tetrapod limb, that of Tulerpeton from Russia, which has six digits. The morphology of the specimens suggests that limbs with digits may have been adaptations to an aquatic rather than a terrestrial environment. The pattern of digits corresponds to a recently proposed model for limb development in which digit number is unspecified, rather than earlier models which are rejected because they postulate a fixed number of elements in the ancestral limb. We challenge pentadactyly as primitive for tetrapods. The form of these limbs suggests early specialization in the evolution of the tetrapod limb bud.
http://www.nature.com/nature/journal/v342/n6248/pdf/342425a0.pdf

Новости 1991г.
Fish-like gills and breathing in the earliest known tetrapod
THE origin of tetrapods is generally associated with the emergence of terrestrial vertebrate life. Anatomical features unique to tetrapods are usually considered to be adaptations to the terrestrial environment. Here we report the discovery of a fish-like branchial skeleton in Acanthostega gunnari, from the Upper Devonian of East Greenland, one of the earliest tetrapods known. It shows a proximally expanded ceratohyal and large, ventrally grooved ceratobranchials. Such grooves are found in the ceratobranchials of modern fishes, and house the afferent branchial aortic arches. The shoulder girdle bears a postbranchial lamina along its anterior margin. In fishes this supports the posterior wall of the opercular chamber. Acanthostega seems to have retained fish-like internal gills and an open opercular chamber for use in aquatic respiration, implying that the earliest tetrapods were not fully terrestrial. The discovery provides information on the sequence of acquisition of tetrapod characters, and supports previous suggestions that such characters as legs with digits1 evolved first for use in water.
http://www.nature.com/nature/journal/v352/n6332/pdf/352234a0.pdf

Tetrapod or near-tetrapod fossils from the Upper Devonian of Scotland
SINCE 1932, the earliest known undisputed tetrapods have been of uppermost Famennian (late Upper Devonian) age. Although a probable tetrapod jaw has been described from the Lower Famennian, and tetrapod tracks of supposedly Frasnian (and possibly earlier) age are known, no fossil limb material older than the latest Famennian has been discovered. The 'panderichthyids'Panderichthys and Elpistostege from the Lower Frasnian (early Upper Devonian) are regarded by some as the closest known sister group of tetrapods, but Panderichthyshas paired fins rather than limbs. Here, I describe a hitherto unrecognized tibia from the Upper Frasnian (middle Upper Devonian) site of Scat Craig, near Elgin, Scotland, collected during the nineteenth century, which extends the fossil record of the tetrapod-type hind limb by roughly seven million years15. Other isolated bones from the same locality also show tetrapod characteristics. The tibia, a humerus and some incomplete jaws are discussed below, but a complete description of the material is in preparation.
http://www.nature.com/nature/journal/v354/n6351/pdf/354298a0.pdf
 
RelictДата: Суббота, 25.06.2011, 21:40 | Сообщение # 8
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Новости 1994г.

Earliest known tetrapod braincase and the evolution of the stapes and fenestra ovalisACANTHOSTEGA gunnari, from the Upper Devonian (Famennian) of East Greenland, is the most primitive known tetrapod, and retains many fish-like characters1–4. I report here the discovery of further well preserved specimens that show the earliest known tetrapod braincase, and shed light on the history of the tetrapod ear region. The fenestra ovalis is shown to be derived directly from the vestibular fontanelle5,6, a hole in the sidewall of the braincase of fishes seen in their embryology and in primitive fossil fish adults. The hole is not a uniquely tetrapod character7,8. A specialized auditory fenestra ovalis may have evolved more than once among tetrapods. As in other tetrapods, the stapedial footplate of Acan-thostega fitted into the fenestra ovalis, but instead of being free to vibrate as part of an ear, was firmly held there, forming a major component of the braincase wall. It was the only component linking the otic capsule to the palate. Though the stapes may have carried muscles operating a spiracular valve, the new material suggests that it was not a mobile component of the skull as previously suggested4. The stapes, spatially replacing parts of the fish brain-case including the process carrying facets for the hyomandibular articulation9, has a footplate which incorporates both heads of the sarcopterygian hyomandibula.
http://www.nature.com/nature/journal/v369/n6479/pdf/369392a0.pdf

The origin and early diversification of tetrapods
A series of new fossil discoveries, coupled with cladistic analysis of old and new data, is beginning to resolve the origin of tetrapods into a documented sequence of character acquisition. Devonian tetrapods were more fish-like than believed previously, whereas Lower Carboniferous tetrapod faunas contain early representatives of the amphibian and amniote lineages. These very different assemblages are separated by a 20-million-year Tournaisian gap' which has yielded very few tetrapod fossils.
http://www.nature.com/nature/journal/v368/n6471/pdf/368507a0.pdf

Новость 1995г.
Elginerpeton pancheni and the earliest tetrapod clade.
THE first 'tetrapod-like' bones from the Scottish Upper Devonian site of Scat Craig (Scat Craig beds, Upper Frasnian) were figured and discussed in 1991 (ref. 1). Additional specimens have since been discovered that permit a formal description, and the background knowledge of Devonian tetrapod anatomy has greatly improved. These discoveries emphasize the uniqueness and phylogenetic importance of the Scat Craig material. Elginerpeton pancheni gen. et sp. nov., described here on the basis of cranial remains from Scat Craig, is, together with the fragmentary genus Obruchevichthys from the Upper Frasnian of Latvia and Russia , the oldest known stem tetrapod. Elginerpeton and Obruchevichthys form a clade that is the sister group of all other Tetrapoda. This contrasts with the later Devonian stem tetrapods, which all seem to represent separate plesions. Elginerpeton also has a unique, derived head morphology; it shows that the earliest phase of tetrapod evolution was accompanied by previously unrecognized morphological and phylogenetic diversification.
http://www.nature.com/nature/journal/v373/n6513/pdf/373420a0.pdf
 
RelictДата: Суббота, 25.06.2011, 22:04 | Сообщение # 9
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Новость 1997г.
Fins made for walking
One of the most enigmatic issues in vertebrate evolution is the fish-tetrapod transition — that period of evolutionary history when, some 365 million years ago, four-legged land animals first appeared in the fossil record. The transition was accompanied by radical innovation in limb structure such as the appearance of digits, and later (although we don't know exactly when) adaptations to habitual air breathing.
http://www.nature.com/nature/journal/v390/n6655/full/390021a0.html

Новости 1998г.
Fish with fingers?
Fingers and toes were long thought to be novelties associated with the invasion of land by tetrapods. The recent identification of a variety of aquatic specializations in some early tetrapods has provoked a debate on whether digits arose in primarily terrestrial or aquatic animals. We recently discovered a pectoral fin of a lobe-finned fish (Fig. 1a, b) that is remarkably similar to tetrapod limbs. This discovery reveals that major tetrapod novelties are also seen in the paddles of some closely related fish and therefore need not have arisen to meet the demands of a terrestrial existence.
http://www.nature.com/nature....F1.html
a, Ventral view of newly discovered right pectoral fin of a rhizodontid sarcopterygian fish (ANSP 20581); proximal humerus not exposed. Scale bar, 2 cm. Note (1) the array of jointed and branched preaxial radials; (2) common proximo-distal termination of ulnare and intermedium; (3) lack of postaxial process on the ulnare. b, Line drawing of ANSP 20581, proximal humerus reconstructed. c, Pectoral fin of the osteolepiform sarcopterygian Eusthenopteron. d, Pectoral limb of the Late Devonian tetrapod Acanthostega. Shaded elements emphasize the similarity in pattern of fin radials and digits. H, Humerus; U, ulna; r, radius; u, ulnare; i, intermedium; b, c, d are not to scale.
http://www.nature.com/nature/journal/v391/n6663/full/391133a0.html

Osteolepiforms and the ancestry of tetrapods
Fossil discoveries and improved phylogenies have greatly improved our understanding of the origin of tetrapods, making it possible to reconstruct sequences of character change leading to tetrapod morphologies and to tentatively identify the genetic basis for some of these changes8,9. However, progress has centred on the upper part of the Tetrapodomorpha5 which is occupied by Devonian tetrapods such as Acanthostega and Ichthyostega. Few advances have been made in improving our understanding of the lower, 'fish' part of the group, beyond establishing Elpistostegalia, Osteolepiformes and Rhizodontida as progressively more primitive constituents. It has not been convincingly confirmed or disproved that the Osteolepiformes, a diverse but structurally uniform group that is central to the debate about tetrapod origins, is monophyletic relative to tetrapods (that is, a single side branch on the tetrapod lineage). The earliest steps of the fish–tetrapod transition have thus remained poorly resolved. Here we present the first detailed analysis of the lower part of the Tetrapodomorpha, based on 99 characters scored for 29 taxa. We show that both the Osteolepiformes as a whole and their constituent group Osteolepididae are paraphyletic to tetrapods (that is, each comprises a section of the tetrapod lineage with several side branches), and that their 'uniting characters' are attributes of the tetrapodomorph stem lineage. The supposedly discredited idea of osteolepiforms as tetrapod ancestors is, in effect, supported by our analysis. Tetrapod-like character complexes evolved three times in parallel within the Tetrapodomorpha.
http://www.nature.com/nature/journal/v395/n6704/full/395792a0.html
 
RelictДата: Суббота, 25.06.2011, 23:09 | Сообщение # 10
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Новость 1999г.
First footing http://www.nature.com/news/1999/990715/full/news990715-5.html
The earliest vertebrates - backboned animals, such as you and me - to emerge on land did so at the end of the Devonian Period, around 365 million years ago. Or did they? The timing of the first steps on land has recently been the focus of vigorous debate, the latest salvo of which appears in the July issue of the journal Geology.

The story starts in the 1930s, when a team of Danish and Swedish palaeontologists collected the bones of Ichthyostega and Acanthostega, the earliest fossil land vertebrates, from the east coast of Greenland. The richest pickings came from rocks of the so-called 'Celsius Bjerg Group' on the Gauss Halvø peninsula.

For all that it had legs, one of these creatures, Ichthyostega, looked very fish-like, with a finny tail. Systematic collection continued for several decades. In 1987, an Anglo-Danish expedition brought back fossils of the hitherto poorly known Acanthostega showing that although it, too, had legs, it also had many fish-like features including internal gills. These creatures were as close as one might expect to the earliest vertebrates to leave their ancestral, watery home - crudely, they were fishes with legs.

Based on the presence in the rocks of fossils of several types of (legless) fishes known from Devonian rocks elsewhere in the world, the Celsius Bjerg Group is usually thought to have been deposited at the very end of the Devonian period, 365 million years ago. Perhaps surprisingly, the rocks have never been dated independently - that is, by any means other than matching the roster of fossil fishes from the Celsius Bjerg Group with fossil fishes elsewhere.

However, the Devonian date for Ichthyostega and Acanthostega - then, as now, the earliest land vertebrates known from more than isolated pieces of bone - received additional support from other work. As fossils came in from other parts of the world, it became clear that the first flush of vertebrate land life at the end of the Devonian was followed by a period of consolidation. By the early part of the succeeding Carboniferous period, around 330 million years ago, land life was securely established, with a variety of fully land-living forms ranging from amphibians to the very earliest, lizard-like relatives of modern reptiles, mammals and birds.

This is why a report in Geology in 1997 came as such a rude shock: in the report, E. H. Hartz of the University of Oslo, Norway and colleagues suggested that the Celsius Bjerg Group was Carboniferous, rather than Devonian, in age - a full 30 million years younger. The evidence came from dates from volcanic rocks from the region, as well as details of the structural geology. The implications were radical, because they completely distorted the entire fossil record of the Devonian and Carboniferous periods worldwide. If it was true, then Acanthostega and Ichthyostega would not have been Devonian pioneers, but peculiar, archaic relics in a Carboniferous world full of fully-terrestrial forms. The subsequent debate in the literature was furious.

The palaeontologists are fighting back with new evidence: the latest report in Geology, from J. E. A. Marshall of the University of Southampton, UK and colleagues, presents descriptions of fossil plant spores from the Celsius Bjerg Group. Fossil spores are plentiful and distinctive, and the records of spores in various rocks can be used to order them in sequence. By comparing the Celsius Bjerg spores with fossil spores from other parts of the world, the researchers amass evidence that the rocks really were deposited in the Devonian, rather than the succeeding Carboniferous. In fact, the spore record suggests that Ichthyostega and Acanthostega might even be slightly older than had been thought, not younger.

Based on this new work, the researchers comment that the data presented by Hartz and colleagues "are incompatible" with the "established" palaeontological evidence - a statement that might, in some quarters, be seen as a challenge.
 
RelictДата: Суббота, 25.06.2011, 23:43 | Сообщение # 11
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Новости 2002г.
Early land vertebrates
A 350-million-year-old fossil provides evidence of an almost unknown stage in the origin of land vertebrates. It is also a reminder of how little is known of the relationships between the main lineages of amphibians and reptiles.
The transition between fish and land vertebrates was a turning point in the history of life. Early stages in the evolution from aquatic lobe-finned fish to tetrapods — animals with limbs capable of locomotion on land — are seen in many fossils from the Upper Devonian1, just before 363 million years ago.
http://www.nature.com/nature/journal/v418/n6893/full/418035a.html

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.
http://www.nature.com/nature/journal/v418/n6893/full/nature00824.html

When fish learned to walk
The process by which fish took to the land occurred in several steps.
The evolutionary transition from fish to air-breathing, four-legged land vertebrates, or tetrapods, is a fascinating segment of vertebrate evolution. It is increasingly well documented by fossils dating from the Late Devonian and Early Carboniferous periods, from 370 million to 320 million years ago.
http://www.nature.com/nature/journal/v419/n6905/full/419339a.html

Palaeontology: First Devonian tetrapod from Asia
The earliest tetrapods (vertebrates with limbs rather than paired fins) date from the Late Devonian Period (370–354 million years ago) — nine genera have been described, all of which are from the Euramerican supercontinent that comprises Europe, north America and Greenland, apart from a single Gondwanan genus, Metaxygnathus, from Australia. Here we report the discovery of the first Devonian tetrapod from Asia, a finding that substantially extends the geographical range of these animals and raises new questions about their dispersal. These forms seem to have achieved worldwide distribution and great taxonomic diversity within a relatively short time.
http://www.nature.com/nature/journal/v420/n6917/full/420760a.html
 
RelictДата: Воскресенье, 26.06.2011, 00:42 | Сообщение # 12
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Новость 2003г.
A uniquely specialized ear in a very early tetrapod
The Late Devonian genus Ichthyostega was for many decades the earliest known tetrapod, and the sole representative of a transitional form between a fish and a land vertebrate. However, despite being known since 1932 from a large collection of specimens, its morphology remained enigmatic and not what was expected of a very primitive tetrapod. Its apparent specializations led it to be considered as a “blind offshoot” or “sidebranch” off the tetrapod family tree, and recent cladistic analyses have disagreed about its exact phylogenetic position within the tetrapod stem group. In particular, its braincase and ear region defied interpretation, such that conventional anatomical terms seemed inapplicable. Using new material collected in 1998, preparation of earlier-collected material, and high-resolution computed tomography scanning, here we identify and interpret these problematic anatomical structures. They can now be seen to form part of a highly specialized ear, probably a hearing device for use in water. This represents a structurally and functionally unique modification of the tetrapod otic region, unlike anything seen in subsequent tetrapod evolution. The presence of deeply grooved gill bars as in its contemporary Acanthostega suggest that Ichthyostega may have been more aquatically adapted than previously believed.
http://www.nature.com/nature/journal/v425/n6953/full/nature01904.html

Новости 2004г.
Devonian tetrapod from western Europe
Several discoveries of Late Devonian tetrapods (limbed vertebrates) have been made during the past two decades, but each has been confined to one locality. Here we describe a tetrapod jaw of about 365 million years (Myr) old from the Famennian of Belgium, which is the first from western continental Europe. The jaw closely resembles that of Ichthyostega, a Famennian tetrapod hitherto known only from Greenland. The environment of this fossil provides information about the conditions that prevailed just before the virtual disappearance of tetrapods from the fossil record for 20 Myr.
http://www.nature.com/nature/journal/v427/n6973/full/427412a.html
 
RelictДата: Воскресенье, 26.06.2011, 01:03 | Сообщение # 13
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Новости 2005г.
Between water and land
The most informative examples of large-scale evolution are provided by major transitions between environments. Fresh research on an ancient amphibian shows how it adapted to locomotion both in water and on land.
One of the defining events in the history of life was the emergence of terrestrial vertebrates from early fish. The oldest known fossils that illustrate the transition to land are those of Ichthyostega from the Upper Devonian of East Greenland.
http://www.nature.com/nature/journal/v437/n7055/full/437038a.html

The axial skeleton of the Devonian tetrapod Ichthyostega
Ichthyostega was the first Devonian tetrapod to be subject to a whole-body reconstruction. It remains, together with Acanthostega, one of only two Devonian tetrapods for which near-complete postcranial material is available. It is thus crucially important for our understanding of the earliest stages of tetrapod evolution and terrestrialization. Here we show a new reconstruction of Ichthyostega based on extensive re-examination of original material and augmented by recently collected specimens. Our reconstruction differs substantially from those previously published and reveals hitherto unrecognized regionalization in the vertebral column. Ichthyostega is the earliest vertebrate to show obvious adaptations for non-swimming locomotion. Uniquely among early tetrapods, the presacral vertebral column shows pronounced regionalization of neural arch morphology, suggesting that it was adapted for dorsoventral rather than lateral flexion.
http://www.nature.com/nature/journal/v437/n7055/full/nature03893.html

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.
http://www.nature.com/nature/journal/v439/n7074/full/nature04196.html
 
RelictДата: Воскресенье, 26.06.2011, 20:58 | Сообщение # 14
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Новость 2008г.
Ventastega curonica and the origin of tetrapod morphology
The gap in our understanding of the evolutionary transition from fish to tetrapod is beginning to close thanks to the discovery of new intermediate forms such as Tiktaalik roseae. Here we narrow it further by presenting the skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica from the Late Devonian of Latvia, a transitional intermediate form between the ‘elpistostegids’ Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega. Ventastega is the most primitive Devonian tetrapod represented by extensive remains, and casts light on a part of the phylogeny otherwise only represented by fragmentary taxa: it illuminates the origin of principal tetrapod structures and the extent of morphological diversity among the transitional forms.
http://www.nature.com/nature/journal/v453/n7199/full/nature06991.html
 
RelictДата: Четверг, 13.12.2012, 15:56 | Сообщение # 15
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http://komikz.ru/news/science-and-education/?id=8750

Интересно, как называется новый тиманский тетрапод? Тиманостега? Безносовия? happy
 
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