Late Mesozoic palaeobiogeography has been characterized by a distinction between the northern territories of Laurasia and the southern landmasses of Gondwana. The repeated discovery of Gondwanan ...lineages in Laurasia has led to the proposal of alternative scenarios to explain these anomalous occurrences. A new biogeographical model for late Mesozoic terrestrial ecosystems is here proposed in which Europe and "Gondwanan" territories possessed a common Eurogondwanan fauna during the earliest Cretaceous. Subsequently, following the Hauterivian, the European territories severed from Africa and then connected to Asiamerica resulting in a faunal interchange. This model explains the presence of Gondwanan taxa in Laurasia and the absence of Laurasian forms in the southern territories during the Cretaceous. In order to test this new palaeobiogeographical model, tree reconciliation analyses (TRAs) were performed based on biogeographical signals provided by a supertree of late Mesozoic archosaurs. The TRAs found significant evidence for the presence of an earliest Cretaceous Eurogondwanan fauna followed by a relatively short-term Gondwana-Laurasia dichotomy. The analysis recovered evidence for a biogeographical reconnection of the European territories with Africa and South America-Antarctica during the Campanian to Maastrichtian time-slice. This biogeographical scenario appears to continue through the early Tertiary and sheds light on the trans-Atlantic disjunct distributions of several extant plant and animal groups.
Pterosaurs were the first vertebrates to evolve powered flight
and comprised one of the main evolutionary radiations in terrestrial ecosystems of the Mesozoic era (approximately 252-66 million years ...ago), but their origin has remained an unresolved enigma in palaeontology since the nineteenth century
. These flying reptiles have been hypothesized to be the close relatives of a wide variety of reptilian clades, including dinosaur relatives
, and there is still a major morphological gap between those forms and the oldest, unambiguous pterosaurs from the Upper Triassic series. Here, using recent discoveries of well-preserved cranial remains, microcomputed tomography scans of fragile skull bones (jaws, skull roofs and braincases) and reliably associated postcrania, we demonstrate that lagerpetids-a group of cursorial, non-volant dinosaur precursors-are the sister group of pterosaurs, sharing numerous synapomorphies across the entire skeleton. This finding substantially shortens the temporal and morphological gap between the oldest pterosaurs and their closest relatives and simultaneously strengthens the evidence that pterosaurs belong to the avian line of archosaurs. Neuroanatomical features related to the enhanced sensory abilities of pterosaurs
are already present in lagerpetids, which indicates that these features evolved before flight. Our evidence illuminates the first steps of the assembly of the pterosaur body plan, whose conquest of aerial space represents a remarkable morphofunctional innovation in vertebrate evolution.
This study contributes to the knowledge of continental fishes recovered from sedimentary successions corresponding to the Bonaerean Stage/Age (late mid-Pleistocene) in the locality of Centinela del ...Mar, General Alvarado County, Buenos Aires province, Argentina. At this site we describe fossil fishes from a palaeolagoon, including Corydoras sp., Pimelodella sp., Rhamdia sp., Oligosarcus sp., small undetermined characids, Jenynsia sp. and Odontesthes sp. The recovered ichthyofaunal assemblage comprises at least seven taxa of Paranaean lineage. The taxonomic composition of the palaeoichthyofauna is quite comparable to that presently found in Bonaerean Watercourses of the Atlantic Drainage ecoregion. This suggests that local ichthyofaunal communities have remained relatively stable since the late mid-Pleistocene.
Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems. Early theropod evolution is currently interpreted as the diversification of various carnivorous and ...cursorial taxa, whereas the acquisition of herbivorism, together with the secondary loss of cursorial adaptations, occurred much later among advanced coelurosaurian theropods. A new, bizarre herbivorous basal tetanuran from the Upper Jurassic of Chile challenges this conception. The new dinosaur was discovered at Aysén, a fossil locality in the Upper Jurassic Toqui Formation of southern Chile (General Carrera Lake). The site yielded abundant and exquisitely preserved three-dimensional skeletons of small archosaurs. Several articulated individuals of Chilesaurus at different ontogenetic stages have been collected, as well as less abundant basal crocodyliforms, and fragmentary remains of sauropod dinosaurs (diplodocids and titanosaurians).
The evolutionary history of Maniraptora, the clade of carnivorous dinosaurs that includes birds and the sickle-clawed Dromaeosauridae, has hitherto been largely restricted to Late Jurassic and ...Cretaceous deposits on northern continents. The stunning Early Cretaceous diversity of maniraptorans from Liaoning, China, coupled with a longevity implied by derived Late Jurassic forms such as Archaeopteryx, pushes the origins of maniraptoran lineages back to Pangaean times and engenders the possibility that such lineages existed in Gondwana. A few intriguing, but incomplete, maniraptoran specimens have been reported from South America, Africa and Madagascar. Their affinities remain contested, however, and they have been interpreted as biogeographic anomalies relative to other faunal components of these land-masses. Here we describe a near-complete, small dromaeosaurid that is both the most complete and the earliest member of the Maniraptora from South America, and which provides new evidence for a unique Gondwanan lineage of Dromaeosauridae with an origin predating the separation between northern and southern landmasses.
Pisanosaurus mertii was originally described on the basis of an incomplete skeleton from the early Late Triassic (Carnian) of northern Argentina. It is consistently regarded by most authors as a very ...basal ornithischian, the sister group of remaining members of the clade. The referral to Ornithischia is based mainly on tooth-bearing bones and tooth morphology. On the other hand, the postcranium is recognized as strikingly plesiomorphic for ornithischians, and even for dinosaurs. The recent description of non-dinosaurian dinosauriforms of the clade Silesauridae having ornithischian-like dentition invites a review of the phylogenetic affinities of Pisanosaurus. In this regard, an overview of the holotype specimen allows a reanalysis of previous anatomical interpretations of this taxon. The phylogenetic analysis presented here suggests that Pisanosaurus may be better interpreted as a member of the non-dinosaurian Silesauridae. It shares with silesaurids reduced denticles on the teeth, teeth fused to maxilla and dentary bone, sacral ribs shared between two sacral vertebrae, lateral side of proximal tibia with a fibular flange, and dorsoventrally flattened pedal ungual phalanges. The present analysis indicates that Pisanosaurus should be removed from the base of the Ornithischia and should no longer be considered the oldest representative of this dinosaurian clade.
The present contribution aims is to analyze the fossil record of the genus Echinorhinus in South America, and particularly Argentina. We made a first-hand examination of the species Echinorhinus ...pozzi from the early Miocene of Patagonia, and recognize it as a valid taxon. The species was originally described in the XIX century, and since then no author described or illustrated the original material based on observations of the actual specimens. The genus Echinorhinus is reported for the first time in late Miocene Paraná beds, based on the occurrence of fossil dermal spines. The species Echinorhinus maremagnum occurring in the latest Cretaceous outcrops from Patagonia in Chile and Argentina is considered valid and clearly distinguishable from E. lapaoi, contradicting recent claims that argue their synonymy.
•Here we review the fossil record of Echinorhinus sharks from South America.•These sharks have a long and complex taxonomic history.•Here we discuss in detail the traits that are traditionally used to distinguish fossil species from this region.•Seeking to clarify the taxonomic status of the fossil species of Echinorhinus present in the southern cone.
Megaraptora is a theropod clade known from former Gondwana landmasses and Asia. Most members of the clade are known from the Early to Late Cretaceous (Barremian-Santonian), with Maastrichtian ...megaraptorans known only from isolated and poorly informative remains. The aim of the present contribution is to describe a partial skeleton of a megaraptorid from Maastrichtian beds in Santa Cruz Province, Argentina. This new specimen is the most informative megaraptoran known from Maastrichtian age, and is herein described as a new taxon. Phylogenetic analysis nested the new taxon together with other South American megaraptorans in a monophyletic clade, whereas Australian and Asian members constitute successive stem groups. South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built.
The fossil record of ornithischians in South America is sparse, and they are clearly underrepresented when compared with sauropod dinosaurs. However, recent discoveries indicate that ornithischians ...were more diversified than thought. The aim of the present contribution is to describe isolated remains belonging to ankylosaurs and ornithopods, including basal euiguanodontians and hadrosaurs coming from the Chorrillo Formation (upper Campanian–lower Maastrichtian), Santa Cruz province, southern Argentina. The fossil remains of ankylosaurs reported here are the southernmost recorded for the continent. They show a unique combination of plesiomorphic features, indicating that they may belong to a basal ankylosaur. Ankylosaurs and hadrosaurids are thought to have arrived in South America during the latest Cretaceous through Central America. However, a detailed overview of the fossil record of Gondwana indicates that both clades were present and probably diversified across southern continents. This indicates that their presence in South America may be alternatively interpreted as the result of migration from other landmasses, including Africa and Europe, or may even be the result of Jurassic–Early Cretaceous vicariance from their northern counterparts.
•New ankylosaur remains for South America representing a small sized animal with long bones and osteoderms.•A new representative of the Gasparinisaura clade is here reported, extending this group of ornithopods to the Maastrichtian southern Patagonia.•The discovery of hadrosaurs allow us to correlate Chorrillo Formation with the adjacent Chilean Dorotea Formation.•The presence of four ornithischian taxa in the Chorrillo Formation erect this as the more diverse Formation in this dinosaurs in South America.
The aim of the present contribution is to review the fossil record of chimaeroids in Argentina. We review previous records from Argentina, including the presence of Cretaceous chimaeroids reported by ...Ameghino in the 19
th
century from the Cretaceous of Santa Cruz province. We re-analyse the species Callorhynchus crassus described from the Miocene of Patagonia by Smith Woodward and Withe in the early 20
th
century. It is here considered as a valid taxon within the genus Ischyodus as I. crassus nov. comb. Ichyodus dolloi is reported for the first time for the Palaeocene of Patagonia, Argentina. We report for the first time in Argentina fossils belonging to Callorhinchus from Holocene deposits in Buenos Aires province. The long temporal range of Holocephali in Argentina (from Late Cretaceous to Holocene) contrasts with the paucity of their fossil record. This indicates that the history of the clade in southern South America is far from well known.
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