Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic.

Regional diastolic wall motion is impaired at baseline in ischaemic myocardial segments, even when systolic contraction is preserved. Pulsed wave Doppler tissue imaging is a useful non-invasive technique which allows the assessment of regional diastolic performance and dynamics of the left ventricular myocardium. Further studies are required to define this role in the evaluation of coronary heart disease.

The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina. Here we report a Jurassic mammal represented by a dentary, which is the first, to our knowledge, from South America. The tiny fossil from the Middle to Late Jurassic of Patagonia is a representative of the recently termed Australosphenida, a group of mammals from Gondwanaland that evolved tribosphenic molars convergently to the Northern Hemisphere Tribosphenida, and probably gave rise to the monotremes. Together with other mammalian evidence from the Southern Hemisphere, the discovery of this new mammal indicates that the Australosphenida had diversified and were widespread in Gondwanaland well before the end of the Jurassic, and that mammalian faunas from the Southern Hemisphere already showed a marked distinction from their northern counterparts by the Middle to Late Jurassic.

A new mammal from the Middle Jurassic Cañ adon Asfalto Formation, Patagonia, Argentina, is reported. The specimen, an isolated lower? molariform, is erected as the type of a new genus and species of triconodont, Argentoconodon fariasorum. The molariform presents a peculiar combination of primitive and derived features that makes recognition of its affinities challenging. Argentoconodon shares similarities with poorly known triconodonts from the Jurassic of North America and Morocco and lacks the diagnostic traits of the triconodontid triconodonts. Argentoconodon resembles in general the paraphyletic ''amphilestid'' triconodonts. The specimen is too incomplete to warrant broader interpretations, but it suggests that at least this lineage of South American mammals was distinctly autapomorphic, perhaps with an origin in forms with a broader geographical distribution.

We report the discovery of the first vertebrate from the Paleogene of Tierra del Fuego (Isla Grande), Argentina, in southernmost South America. The specimen consists of parts of an associated pelvic girdle and limb that are identified as belonging to the penguin stem clade (Aves: Pansphenisciformes). The specimen, from an exposure of the Leticia Formation (late middle Eocene), is the earliest known penguin (pansphenisciform) from South America. It is more than 20 million years older than the earliest previously recorded South American penguins (from the late Oligocene-early Miocene) and, thus, almost doubles their known record on the continent.A detailed description of the new specimen and a discussion of its implications for the understanding of penguin morphological evolution are provided. The new specimen and other fossil penguins do not currently point to the origin of extant, or crown clade, penguin lineages (Spheniscidae), by the Eocene, only to the divergence of the penguin stem lineage from its sister taxon by this time. The new fossil has several morphologies that differ from all extant penguins but are shared with other fossil penguin taxa, suggesting they may be outside Spheniscidae. However, in a discussion of the current status of penguin systematics, we suggest the urgent need for comprehensive phylogenetic analysis of fossil and extant penguins to clarify the timing and pattern of penguin diversification.The specimen was recovered from a newly identified fossil vertebrate locality, an exposure of the Eocene Leticia Formation at Punta Torcida on the Atlantic shore of southeastern Tierra del Fuego, Argentina. The new locality is introduced, and a brief geologic description is made,

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The present paper includes detailed descriptions of all fossil fishes known from the Los Rastros Formation (Ladinian; Bermejo Basin, Argentina). Four taxa are identified: Gualolepis carinaesquamosa n. gen. n. sp., Rastrolepis n. gen. with two species R. riojaensis n. sp. and R. latipinnata n. sp., and Challaia elongata n. comb. Gualolepis n. gen. and Rastrolepis n. gen. are incer-tae sedis actinopterygians. The opercular bones of Gualolepis resemble those in peipiaosteid acipenseriforms and the fish might be related with the Chondrostei. The most distinctive features of Rastrolepis are the narrow opercular region and the presence of a very large plate-like branchiostegal bone resembling the condition in the Redfieldiiformes. Challaia elongata, originally described in the Australian genus Myriolepis, is here refered to the genus Challaia, previously known from the nearby Cuyo Basin and representing the first fish taxon common to both continental sequences. Furthermore, Challaia is shown to be a member of the Acrolepidae and represents the youngest record of the family in Gondwana. Schlü sselwö rter: Actinopterygii, Acrolepidae, Trias, Sü damerika, Argentinien. Zusammenfassung Alle fossilen Fische, die bisher von der Los Rastros Formation (Ladin; Bermejo-Becken, Argentinien) bekannt sind, werden im Detail beschrieben. Vier Taxa kö nnen identifiziert werden: Gualolepis carinaesquamosa n. gen. n. sp., Rastrolepis n. gen., mit zwei Arten, R. riojaensis n. sp. und R. latipinnata n. sp., und Challaia elongata comb. nov. Gualolepis n. gen. und Rastrole-pis n. gen. Actynopterygier unsicherer systematischer Stellung. Die Operkular-Knochen von Gualolepis a ¨ hneln jenen der pei-piaosteiden Acipenseriformen und das Taxon mag mit den Chondrostei verwandt sein. Die auffä lligsten Merkmale von Ras-trolepis sind die sehr schmale Operkularregion und das Vorhandensein eines sehr großen, plattigen Branchiostegale, das dem Zustand in Redfieldiiformen a ¨ hnelt. Challaia elongata, ursprü nglich zu der australischen Gattung Myriolepis gestellt, wird hier der Gattung Challaia zugeordnet, die bisher nur aus dem nahegelegenen Cuyo-Becken bekannt war und reprä sentiert somit das erste Fisch-Taxon, das in beiden Sequenzen vorkommt. Zudem kann gezeigt werden, dass Challaia zu den Acrolepidae gehö rt und somit den jü ngsten Nachweis dieser Gruppe in Gondwana darstellt.

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