Academic literature on the topic 'Tetrapodomorpha'

ABSTRACTEach piece of data is valuable for unearthing the earliest history of tetrapod origin. Despite frequently incomplete preservation, each skeletal element provides important information on the morphology, phylogeny and faunistic diversity of early tetrapodomorphs. We describe here new and earlier collected material from the fossil vertebrate site Yam-Tesovo on the Oredezh River (Leningrad Region, northwestern Russia) in the deposits of the Yam-Tesovo Formation within the Amata Regional Stage (?lowermost Frasnian, Upper Devonian). Upon similarity of their dermal ornamentation, two mandibular fragments are suggested to belong to the new tetrapodomorph taxon Rubrognathuskuleshovi n. gen. et sp. This species demonstrates a general ‘elpistostegalian' morphological pattern with some early tetrapod characters. The new taxon is characterised by an almost closed intercoronoid fossa, a prearticular that is strongly convex in section and bearing small teeth along its dorsal margin, low vertical coronoid laminae and coronoid fangs that enter the coronoid tooth row. The mandibular canal runs partly in open groove or opens to the surface by a row of large pores. The dermal ornament consists of a network of small ridges forming tubercles in the nodes. The postfrontal assigned to Tetrapodomorpha shows a ‘tetrapod-like' pits-and-ridges sculpturing and a supraorbital ridge characteristic of early tetrapods as well as ‘elpistostegalians'. Its long posterolateral bone margin demonstrates a lateral projection similar to that in Tiktaalik and unknown in other ‘elpistostegalians' and early tetrapods. An unusually flattened vomer is doubtfully related to the tetrapodomorph genus Livoniana Ahlberg, Lukševičs & Mark-Kurik, 2000, based upon characteristic multiple tooth rows. Teeth in rows decrease labially and show no clearly enlarged fang pairs. New finds of the last two decades present the earliest records of some tetrapod characters in non-limbed tetrapodomorphs. This challenges previous hypotheses on the origin of tetrapods.

Rhipidistian sarcopterygian fishes (Dipnomorpha + Tetrapodomorpha) are well represented in the upper levels of the Hunter Siltstone (latest Famennian) near Grenfell. New South Wales (NSW), Australia. Taxa comprise two porolepiforms (known primarily from scales, including the widely distributed <i>Holoptychius</i>), the basal rhipidistian taxon <i>Grenfellia meemannae</i> n. gen. and n. sp. and two tetrapodomorphs (<i>Eusthenodon gavini</i> n. sp. and <i>Yambira thomsoni</i> n. gen. and n. sp., both known from skull bones and scales). Biogeographic relationships of the Hunter Siltstone fauna are based on the presence of the placoderm group Sinolepidoidei, shared with Late Devonian faunas from the North and South China terranes. Rhipidistian scales have been described from the latter in association with Late Devonian sinolepids (<i>Sinolepis</i>), but these do not display close taxonomic affinity to scales described from Grenfell. Other Upper Devonian NSW localities show strong faunal similarity to Euramerican localities; <i>Holoptychius</i> occurs in certain of these and at Grenfell, but has not been recorded from <i>Sinolepis</i>-bearing units on the North and South China terranes. These considerations further contradict suggestions that Asian terranes acted as a dispersal route between Gondwana and Euramerica in the Late Devonian. <br><br> Rhipidistiide Sarcopterygier (Dipnomorpha + Tetrapodomorpha) sind in den obersten Schichten des Hunter Siltstone (oberstes Famennium) bei Grenfell, New South Wales (NSW), Australien, stark vertreten. Es handelt sich um zwei Porolepiforme (vertreten hauptsächlich als Schuppen, darunter die weit verbreitete Gattung <i>Holoptychius</i>), der primitive Rhipidistier <i>Grenfellia meemannae</i> n. gen. et n. sp. und zwei Tetrapodomorphe (<i>Eusthenodon gavini</i> n. sp. und <i>Yambira thomsoni</i> n. gen. et n. sp., beide vertreten durch Schädelknochen und Schuppen). Biogeographische Beziehungen der Hunter Siltstone-Fauna sind auf der Anwesenheit von sinolepidoiden Placodermen, die in oberdevonischen Faunen der nord- und südchinesischen Terranes auftreten, begründet. Rhipidistier-Schuppen sind zusammen mit oberdevonischen Sinolepiden (<i>Sinolepis</i>) von den chinesischen Terranes beschrieben worden, aber diese zeigen keine nahe taxonomische Übereinstimmung mit den Schuppen von Grenfell. Andere oberdevonische Lokalitäten von NSW zeigen deutliche Ähnlichkeiten in der faunistischen Zusammensetzung mit euramerikanischen Lokalitäten: <i>Holotychius</i> tritt dort und in Grenfell auf, aber ist nicht von Schichten in nord-und südchinesischen Terranes, die <i>Sinolepis</i> enthalten, beschrieben worden. Auch diese Vergleiche widersprechen Vorstellungen, dass die asiatischen Terranes im Oberdevon als Verbreitungsweg zwischen Gondwana und Euramerika dienten. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.20000030107" target="_blank">10.1002/mmng.20000030107</a>