Irena Kaczmarska, James M. Ehrman, Brajogopal Samanta
An unanticipated diversity of archaeomonad stomatocysts intermixed with marine plankton including diatoms, silicoflagellates, parmaleans and individual siliceous protistan scales was encountered in Rupelian diatomites from the Central Paratethys. In this initial report we document 27 previously described species attributed to three palaeomorphogenera (Archaeomonas, Archaeosphaeridium, and Litheusphaerella). An additional eight morphospecies from two genera (Archaeomonas anterioconica Kaczmarska sp. nov., A. asharya Samanta sp. nov., A. genetynanii Ehrman sp. nov., A. jimstehrii Ehrman & Kaczmarska sp. nov., A. lenistriata Kaczmarska sp. nov., A. litheusphaerellamima Samanta sp. nov., A. sextapapillatus Kaczmarska sp. nov., and Litharchaeocystis centparatethianus Ehrman sp. nov.) are proposed as new to science. We also found at least a dozen more distinct morphotypes in orientations and quantities insufficient for formal description that will be the subject of further studies. Our report is the first from the Central Paratethys and the most species rich archaeomonad flora reported from the Oligocene worldwide. The combination of previously described archaeomonad species recovered with the associated diatoms, parmaleans, silicoflagellates, ebridians, and other marine biota suggest that our stomatocysts are native to their basin and inhabited the neritic part of the Paratethys. Unfortunately, the small number of dedicated studies and archaeomonad species known to date still hampers a better understanding of their biostratigraphy and paleoecology.
Pablo E. Ortiz, Rodrigo González, Virginia Deraco
et al.
Fossils collected by Abel Peirano from Catamarca and Tucumán in the late 1930s constituted the basis for the creation of the Colección Paleontología de Vertebrados Lillo (PVL) in Tucumán. The collection was formally founded in 1957 as Laboratorio de Vertebrados Fósiles (LVF) by Osvaldo Reig, who led many field trips that resulted in the publication and incorporation of emblematic materials from the South American Mesozoic. José Bonaparte became the director of the LVF in 1960, incorporating a large number of Mesozoic fossils from northwest Argentina, Cuyo, and Patagonia. These findings represented an enormous qualitative and quantitative leap in the knowledge of Mesozoic faunas from Gondwana. In 1979, when the LVF was dissolved and the fossil collection became known as PVL, Jaime Powell succeeded Bonaparte as curator and began leading field trips to the Cretaceous and Cenozoic of northwest Argentina and Cretaceous of northern Patagonia, incorporating important material in the collection. In the 1980s, young researchers began to work on fossils stored at the PVL, studying Neogene birds and mammals and Mesozoic archosauriforms and cynodonts. In the 1990s, other scholars under Powell’s guidance focused their research on Cenozoic mammals, providing new and relevant material for the collection. Today the PVL has about 7,900 catalogued specimens (130 holotypes) and it represents one of the most important collections of vertebrate palaeontology in Argentina. In 2010, the collection was registered under the national authority on paleontological matters (Law 25.743) and became part of the Facultad de Ciencias Naturales-Instituto Miguel Lillo, Universidad Nacional de Tucumán.
Claudio Germán De Francesco, Fernando Miguel Archuby, Karen Borrazzo
et al.
Over the past four decades, global actualistic taphonomy studies have grown significantly, driven by increased interest in present day patterns and processes of fossilization. South America has mirrored this trend, though the exact growth level is unclear. This study compiles actualistic taphonomy research in South America based on internationally accessible journal articles and book chapters using databases such as Web of Science, ResearchGate, Google Scholar, and Academia. Results revealed a steady rise in studies from 1985, with Argentina leading, followed by Brazil, Uruguay, and a few other countries with lesser representation. Terrestrial environments have seen the most extensive research, largely due to archaeologists and vertebrate paleontologists, with marine environments (mainly mollusk-based studies) following. Freshwater actualistic taphonomy began in 2006 and was the next most commonly represented, while estuarine and lagoonal environments were the least studied. Most research has been naturalistic: examining taphonomic patterns, taphofacies, live-dead fidelity, and time-averaging. However, experimental studies increased markedly after 2009. Synthesis papers appeared from 2007, reflecting the growing body of literature. Archaeological studies have been the most prolific, with vertebrate studies dominating the region’s actualistic taphonomy literature, followed by research on mollusks and lithics. Brachiopods, foraminifera, diatom, pollen, and phytoliths have developed less. Several groups, including plants, arthropods, worms, lichens, charcoal, pottery, rock art paintings, and sediments, remained poorly studied, highlighting the need for further research. This review underscores the significant progress made in South American actualistic taphonomy but also points to underrepresented environments and taxonomic groups that should be addressed in future studies.
Abstract The anatomy of North American tortoises is poorly understood, despite a rich fossil record from the Eocene and younger strata. Stylemys nebrascensis is a particularly noteworthy turtle in this regard, as hundreds of specimens are known from Oligocene deposits, and as this species is one of the earliest fossil turtles to have been described in the scientific literature. Since its initial description based on a shell, many specimens with more complete material have been referred to Stylemys nebrascensis. Here, we review and confirm the referral of an important historic specimen to Stylemys nebrascensis, which includes shell, non-shell postcranial, and skull material. This allows us to document unique skull features of Stylemys nebrascensis (e.g., an unusual ‘poststapedial canal’ that connects the posterior skull surface with the cavum acustico-jugulare) and to refer another well-preserved skull to the species. Based on computed-tomography scanning of these two skulls, we provide a detailed description of the cranial and mandibular osteology of Stylemys nebrascensis. Stylemys nebrascensis has a combination of plesiomorphic skull characteristics (e.g., retention of a medial jugal process) and derived traits shared with extant gopher tortoises (e.g., median premaxillary ridge) that suggest it may be a stem-representative of the gopher tortoise lineage. This supports the hypothesis that extant and fossil tortoises from North America form a geographically restricted clade that split from Asian relatives during the Paleogene.
Abstract Distinct, new oviposition lesion types, Paleoovoidus pyriformis ichnosp. nov. and Variomorphonotatus sagittaeformis ichnogen. et ichnosp. nov., occurring on two fossil compression Cycadophyte leaves from the Lower Jurassic Shemshak Formation of western Alborz Ranges, northern Iran are documented and compared with the previously instituted morphologically analogous taxa. Comparison of the shape and configuration of the scars with those of the modern zygopteran Odonata suggests that any member of the Lestid-damselfly produced P. pyriformis ichnosp. nov. whereas any representative of Coenagrionid-damselflies (damselflies-dragonflies) induced formation of V. sagittaeformis ichnogen. et ichnosp. nov. In the absence, so far, of any entomofaunal evidence from the Shemshak Formation, the ichnotaxa documented herein offer unequivocal evidence to the presence of the Odonatan representatives in the Early Jurassic riparian ecosystems of northern Iran.
William I. Ausich, Matija Križnar, Karolina Paszcza
et al.
A new crinoid fauna is described from the Trogkofel Group of the Southern Karavanke Mountains, Slovenia (lower Permian, Artinskian). This fauna is from a shallow platform or upper slope setting and is comprised primarily of isolated aboral cups. One taxon, Protencrinus baliensis, previously described from the lower Permian of Crete, is the only species known from elsewhere. New taxa from the Trogkofel Group include Karavankecrinus bedici gen. et sp. nov., Moapacrinus dovjensis sp. nov., Parastachyocrinus sloveniaensis sp. nov., and Sinocrinus websteri sp. nov. Several taxa are left in open nomenclature, including Dieuryocrinus? sp., Platycrinitidae indet., Eucladida indet. A, and unidentified Crinoidea. If Dieuryocrinus? sp. belongs to Dieuryocrinus, this would expand the range of this genus, previously known from the Viséan (Mississippian) of the United Kingdom. Other genera are well known as lower Permian taxa. In addition, the species-level systematics of Parastachyocrinus is revised, and one new species from the lower Permian of Timor is described, P. wanneri sp. nov.
The pterosaur fossil record of Argentina is increasing in recent times, both in the number of localities and their temporal
range. The new materials are found in levels that span from the Late Triassic to the Late Cretaceous in age. In this
contribution we describe twenty isolated pterosaur teeth from the Cerro de los Leones locality (Picún Leufú, Neuquén
Province), where the Lohan Cura Formation (Albian) widely crops out. A new, detailed analysis of these remains allowed
us to detect a set of morphological features, such as the enamel texture, cross-section shape, crown curvature, and absence
of sharp carinae, which suggests close affinities with Ornithocheiriformes. Moreover, with the large number of tooth
specimens, a discrimination of three morphotypes based on the crown curvature, the basal cross-section shape, and the
presence of carinae was carried out. We performed extensive morphological comparisons between different members of
Ornithocheiriformes with the aim to test the hypothesis that the presence of these different morphotypes reflects distinct
anatomical positions of the teeth in the jaws . Thus, considering the heterodont dentition of ornithocheiriforms, the tooth
morphological classification proposed here represents a new methodology, not only to identify isolated ornithocheiriform
teeth, but also to assign them to the rostral, medial, or the posterior portion of the tooth row. Finally, the evidence of
ornithocheiriform pterosaurs in Cerro de los Leones has paleobiogeographical implications, allowing us to correlate it
with other Albian faunas from South America, expanding our knowledge of the distribution of Early Cretaceous pterosaurs
across southwestern Gondwana.
Daniel T. Ksepka, Daniel J. Field, Tracy A. Heath
et al.
AbstractRecent fossil discoveries from New Zealand have revealed a remarkably diverse assemblage of Paleocene stem group penguins. Here, we add to this growing record by describing nine new penguin specimens from the late Paleocene (upper Teurian local stage; 55.5–59.5 Ma) Moeraki Formation of the South Island, New Zealand. The largest specimen is assigned to a new species, Kumimanu fordycei n. sp., which may have been the largest penguin ever to have lived. Allometric regressions based on humerus length and humerus proximal width of extant penguins yield mean estimates of a live body mass in the range of 148.0 kg (95% CI: 132.5 kg–165.3 kg) and 159.7 kg (95% CI: 142.6 kg–178.8 kg), respectively, for Kumimanu fordycei. A second new species, Petradyptes stonehousei n. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguin Aptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recover Kumimanu and Petradyptes crownward of the early Paleocene mainland NZ taxa Waimanu and Muriwaimanu, but stemward of the Chatham Island taxon Kupoupou. These analyses differ, however, in the placement of these two taxa relative to Sequiwaimanu, Crossvallia, and Kaiika. The massive size and placement of Kumimanu fordycei close to the root of the penguin tree provide additional support for a scenario in which penguins reached the upper limit of sphenisciform body size very early in their evolutionary history, while still retaining numerous plesiomorphic features of the flipper.UUID: https://zoobank.org/15b1d5b2-a5a0-4aa5-ba0a-8ef3b8461730
Jorge D. Carrillo-Briceño, Raúl I. Vezzosi, Keesha M. Ming
et al.
Abstract Nearctic ungulates such as artiodactyls, perissodactyls, and proboscideans arrived in South America during the Great American Biotic Interchange. Among them are camelids, cervids, tayassuids, equids, tapirids and gomphotherids. A historical collection of Nearctic ungulates from Pleistocene deposits of the Pampean region in Argentina is here studied and described. The collection consists of specimens collected by Santiago Roth in the nineteenth century and brought to Europe, where they are housed in the paleontological collections of the University of Zurich and the Natural History Museum of Geneva. Among the taxa reported here are Notiomastodon platensis, Lama guanicoe, Hemiauchenia paradoxa, Tayassu pecari, Morenelaphus sp., Hippidion cf. H. principale, Equus cf. E. neogeus, and other indeterminate gomphotherids, camelids, tayassuids, cervids, and equids. The exact stratigraphic position of these fossils collected more than 130 years ago is in many cases uncertain. The historical collection is still relevant for taxonomic studies and for offering new insights into palaeobiogeography and palaeobiology of mammalian fauna of the region during the Pleistocene.
LARISA A. DOGUZHAEVA, HERBERT SUMMESBERGER, FRANZ BRANDSTAETTER
et al.
We performed comprehensive study of seven Carnian, Late Triassic specimens of a coleoid cephalopod Phragmoteuthis
bisinuata, on which Suess based his hypothesis on “beaks of P. bisinuata”. Using SEM/EDS, we found that “beaks of P. bisinuata” consist of a micro-granular carbonized matrix containing ~4–30 μm diameter and ~50–200 μm visible length, dense
calcified bone-like micro-structures. This strongly suggests that these objects are vertebrate bone-inducing cartilages in
which the matrix was post-mortem reworked by carbon-accumulating bacteria and substituted by nano-particles of carbon
accumulated in micro-granules. Hence, the presumed “beaks of P. bisinuata” are cartilaginous remains of a prey, presumably juvenile fish. This data dismissed the entire hypothesis of Seuss. A small spatula-shape plate with a rachis-like process
in an association with 10 or so imprints around (arm crown), found in front of a proostracum of P. bisinuata evidences an
unknown Late Triassic juvenile teuthid which possessed a gladius resembling that of the early Permian Glochinomorpha
stifeli. It inhabited the open sea area of the northwestern Tethys Ocean, and was, along with juvenile fishes, in the diet of
P. bisinuata. The first identified Anisian (Middle Triassic) coleoid beak is represented by an isolated specimen from the
Gardena Valley, NE Italy. It has a typical composition and morphology of coleoid upper beak: chitinous, wide-oval lateral
walls, short wings, and pointed hook-like rostrum. This suggests similar upper beak structure in the Carnian P. bisinuata in
which the lower beaks were apparently similar to that of the co-occurring Lunzoteuthis schindelbergensis and had a widely
open outer lamella with posteriorly elongated paired wings joined into a pointed rostrum in the anterior portion.
Charalampos Kevrekidis, Gloria Arratia, Nikos Bacharidis
et al.
Much remains to be learned about the past diversity and evolutionary history of the Clupeidae (herrings, shads and allies), owing to the frequently subtle differences between modern taxa and the moderate preservational quality of some fossils. In this study, new clupeid fossils are described from a new locality from the upper Miocene of the Serres Basin, Northern Greece. The fossils are well-preserved articulated skeletons, exhibiting features such as a small size (<150 mm in standard length), slender body, two pairs of bullae, at least six parietal–postparietal striae, two supramaxillae, five branchiostegal rays, 10 supraneurals, 40–42 vertebrae, eight or nine pelvic fin rays, 17 rays in the dorsal and 16–19 rays in the anal fin, last two fin rays of the anal fin not elongate, and belly fully scuted. The new fossils cannot be attributed to any modern genus, though they most closely resemble the monotypic genus Hilsa, which today inhabits the Indo-Western Pacific. Detailed comparisons with all fossil clupeid taxa from the Cenozoic indicate that the new fossils constitute a new species, which is tentatively attributed to the fossil genus Pseudohilsa, as Pseudohilsa nikosi Kevrekidis, Arratia, and Reichenbacher sp. nov. Clupeids reportedly similar to the modern-day tropical Hilsa have been previously described from the Pliocene of the Black Sea and the middle Miocene of the Caspian Sea. This is, however, the first time that a possible fossil Hilsa relative has been described from the Mediterranean.
Muhammad Tahir Waseem, Abdul Majid Khan, Jay Quade
et al.
Stable isotope analysis is pivotal for investigating the paleodiet and paleoecology of past mammals. In this paper, we analyzed thirty fossil enamel samples belonging to the families Suidae, Rhinocerotidae, and Deinotheriidae for δ13Cenamel and δ18Oenamel composition to investigate paleodiet and paleoecology of middle Miocene mammals of the Siwalik sub-Group of Pakistan. The three mammalian groups, when combined together, yielded an average δ13Cenamel value of -12.2 ± 2‰, indicating a pure to nearly pure C3 diet. Suids show slightly higher δ13Cenamel values of -11.2 ± 1.4‰ when compared to rhinocerotids and deinotheres (-12.3 ± 0.8‰ and -12.5 ± 1.3‰, respectively), which could be explained by selective foraging on new leaf shoots or feeding from open spaces. Alternatively, the differences in δ13Cenamel could be due to different digestive physiologies and different enamel-diet enrichment factors. Members of all three families showed significant differences in δ18Oenamel values, where suids yielded higher δ18O values of -8.2 ± 1.2‰ compared to rhinocerotids and deinotheres (-11.4 ± 1.8‰ and -10.4 ± 1.7‰, respectively). Based upon these results, we assume that these mammals inhabited subtropical forests similar that of mid-Miocene of the Siwalik Group, India and Nepal. The modern analogues of such vegetation system are present in East and South of Myanmar, Nepal, and Malaya where precipitation is enough to support evergreen C3 forests. By contrast, today’s floodplain environments in Pakistan are dominated by C4 grasses, and C3 vegetation is only present in non-floodplain settings.
Jeffrey D. Stilwell, John St. J. S. Buckeridge, Joseph J. Bevitt
et al.
AbstractAssessment of unique and potentially significant fossils may be considerably compromised by surrounding matrix. This paper assesses a fossil barnacle group from the mid to late Eocene of Seymour Island, off the Antarctic Peninsula, that potentially has very significant phylogenetic importance. It discusses why the specimen could be significant, and describes and applies as a proof of concept an advanced imaging technique, using X-ray Computed Tomography (CT), that was effectively employed to confirm systematic taxonomy with virtual 3-D sections through the specimen. In this case, the Antarctic barnacle's complex internal plate morphologies were resolved by advanced 3-D imaging, such that a taxonomic attribution could be made to either the Archaeobalanidae or Austrobalanidae, excluding the initial assessment of Coronulidae, which would have otherwise been allusive.
Jordi Alexis Garcia Marsà, Federico L. Agnolín, Fernando E. Novas
The Chañares Formation exhibits one of the most important archosauriform records of early Carnian ecosystems. Here we present new data on the palaeohistology of Chañares archosauriforms and provide new insights into their paleobiology, as well as possible phylogenetically informative traits. Bone microstructure of Lagerpeton chanarensis and Tropidosuchus romeri is dominated by fibro-lamellar tissue and dense vascularization. On the other hand, Chanaresuchus bonapartei is more densely vascularized, but with cyclical growth characterized by alternate fibro-lamellar, parallel-fibered and lamellar-zonal tissues. Dense vascularization and fibro-lamellar tissue imply fast growth and high metabolic rates for all these taxa. These histological traits may be tentatively interpreted as a possible adaptative advantage in front of Chañares Formation environmental conditions.
Narambuenatitan palomoi is a titanosaurian sauropod from the Upper Cretaceous of North Patagonia. Considered initially as a basal titanosaur, this taxon has uncertain phylogenetic relationships within the clade. An X-ray Computed Tomography (CT) scan of the holotype braincase allowed the first reconstruction of the brain and inner ear of this taxon, making it possible to compare the neuroanatomy with that of closely related forms. Except for the slightly sigmodal shape of the endocast in lateral view—considered a basal condition—, the brain shows derived titanosaurian traits such as a poorly developed dorsal expansion and a single exit for Cranial Nerve (CN) XII. In contrast, the inner ear exhibits slender and long semicircular canals (the anterior semicircular canal is distinctly longer than the posterior semicircular canal), which is a character present in more basal representatives of the group, such as Sarmientosaurus. We consider, however, the morphology of the inner ear as an unreliable indicator of phylogenetic position. Furthermore, there is a remarkable similarity between the morphology of the endocast of Narambuenatitan and the possible saltasaurid from (FAM 03.064), from the Upper Cretaceous of Fox-Amphoux-Métisson, France, suggesting saltasaurine affinities for the Argentinean taxon.
Conellae, enigmatic cone-shaped structures which can be found on the surface of internal moulds of cephalopod shells (predominantly of ammonoids), are regarded herein as the product of remote (biologically induced) biomineralization formed in closed-off cavities during lifetime and might be primarily composed of vaterite, aragonite, or calcite. To date conellae have been interpreted in many different ways: (i) as organisms (gastropods, cirriped crustaceans, or disciniscid brachiopods), (ii) pre-diagenetic syn vivo features, i.e., biologically controlled or induced, the product of remote biomineralization, (iii) and diagenetic, i.e., abiogenic origin and post-mortem. The proposed processes of conellae formation seem insufficient to explain conellae related phenomena. Further, their assumed primary aragonitic or calcitic mineralogy are reviewed and based on new material critically assessed. The stratigraphic range of conellae extends from the Middle Ordovician and probably to modern Nautilus. Predominantly, conellae can be found on internal moulds along the keel, ribs or nodes, umbilical shoulder, at the transition between phragmocone and body chamber, and can be associated with repaired scars. However, conellae are also common on the smooth body chambers of large macroconchs of Jurassic ammonites. Conellae, which are located on ammonite body chambers, are filled with the same material found in the body chamber and can contain small burrows, sand grains, or coprolites. Some of these conellae are partially covered with nacreous shell material. Limonitic conellae were also found on the limonitic internal moulds of orthocone nautiloids. Moreover, disciniscid brachiopods found on inoceramid bivalves were re-identified herein as conellae. A short guide for conellae identification has been provided herein.
María E. Raffi, Eduardo B. Olivero, Florencia N. Milanese
We describe new material of the subfamily Gaudryceratinae in Antarctica, including five new species: Gaudryceras submurdochi Raffi and Olivero sp. nov., Anagaudryceras calabozoi Raffi and Olivero sp. nov., Anagaudryceras subcompressum Raffi and Olivero sp. nov., Anagaudryceras sanctuarium Raffi and Olivero sp. nov., and Zelandites pujatoi Raffi and Olivero sp. nov., recorded in Santonian to Maastrichtian deposits of the James Ross Basin. The early to mid-Campanian A. calabozoi Raffi and Olivero sp. nov. exhibits a clear dimorphism, expressed by marked differences in the ornament of the adult body chamber. Contrary to the scarcity of representative members of the subfamily Gaudryceratinae in the Upper Cretaceous of other localities in the Southern Hemisphere, the Antarctic record reveals high abundance and diversity of 15 species and three genera in total. This highly diversified record of gaudryceratins is only comparable with the Santonian–Maastrichtian Gaudryceratinae of Hokkaido, Japan and Sakhalin, Russia, which yields a large number of species of Anagaudryceras, Gaudryceras, and Zelandites. The reasons for a similar, highly diversified record of the Gaudryceratinae in these distant and geographically nearly antipodal regions are not clear, but we argue that they probably reflect a similar paleoecological control.
Resumen. La Diagonal Árida Sudamericana (DAS) es un rasgo biogeográfico y climático que ha experimentado cambios importantes en los ambientes, en las plantas, en los animales e incluso en las poblaciones humanas como consecuencia de la dinámica climática durante el Cuaternario tardío. El objetivo de este trabajo es revisar el desarrollo de las investigaciones en palinología del Cuaternario tardío a lo largo de la DAS, analizar sus desafíos, destacar las metodologías aplicadas para obtener registros polínicos robustos en términos paleoambientales y paleoclimáticos y resaltar los avances logrados. La mayoría de las zonas de la DAS presentan una concentración importante de registros polínicos fósiles, pero resulta difícil todavía en algunas áreas generar marcos paleoclimáticos y paleoambientales desde el Pleistoceno Tardío o bien que comprendan todo el Holoceno a escala regional. Esto es consecuencia de que (1) la mayoría de los ambientes depositacionales son “no convencionales” y, por lo tanto, presentan discontinuidades, preservación diferencial del polen y representatividad diferencial de la vegetación local versus la regional lo que complejiza más el análisis de un registro polínico fósil, y (2) la dispersión polínica en las zonas áridas y semiáridas dominadas por vegetación arbustiva y herbácea (en su mayoría entomófila) ha sido escasamente estudiada. Sin embargo, a partir de casos de estudio en tres áreas de la DAS -el desierto de Atacama y los Andes mediterráneos de Chile y la meseta patagónica en Argentina- se demuestra el potencial que los registros polínicos de estas áreas tienen para reconstruir la dinámica paleoclimática desde el Pleistoceno Tardío de manera robusta y confiable, aplicando las metodologías apropiadas.
Palabras clave. Polen. Ambientes depositacionales. Pleistoceno. Holoceno. Zonas áridas y semiáridas. América del Sur.
Abstract. LATE QUATERNARY PALYNOLOGY METHODOLOGIES AND ADVANCES ON THE SOUTH AMERICAN ARID DIAGONAL. The South American Arid Diagonal (SAAD) constitutes a major biogeographic and climatic feature which has experimented significant changes in its environments, plants, animals and human societies due to the late Quaternary climatic dynamics. The aim of this paper is to review the development of Quaternary palynology studies on the SAAD, analyze the challenges, highlight the applied methodologies in order to obtain robust pollen records in palaeoenvironmental and palaeoclimatical terms and therefore, stress the achieved advances. Although most of the areas of the SAAD present a vast number of pollen records, it is still difficult to achieve regional palaeoenvironmental and palaeoclimatic framework for some areas since the Late Pleistocene or even the Holocene. This is based on the fact that (1) most of the depositional environments are not “standard” so they present discontinuities, differential pollen preservation and differential pollen representation of local versus regional vegetation which complicates the pollen analysis, and (2) the pollen dispersion processes in arid and semiarid zones dominated by shrubs and herbs (with many entomophilous species) are scarcely studied. However, taking study cases from three areas of the South American Arid Diagonal –Atacama Desert and Mediterranean Andes of Chile, and Patagonian plateau in Argentina– the potential of the pollen records from these areas to reconstruct the paleoclimatic dynamics since the Late Pleistocene can be demonstrated firmly and convincingly if appropriate methodologies are applied.
Key words. Pollen. Depositional environments. Pleistocene. Holocene. Arid and semi-arid zones. South America.
The caudofemoralis longus muscle (CFL) is the primary limb retractor among non-avian sauropsids, and underwent a dramatic reduction along the dinosaur lineage leading to birds. The osteological correlates of the CFL among fossil reptiles have been controversial, because, contrary to traditional interpretations, the extent of the muscle is not necessarily related to the distribution of the caudal ribs. In some Cretaceous dinosaurs, the extent of the CFL has been inferred based on the preserved bony septa between the CFL and other tail muscles. Here, we describe a series of tail vertebrae of the Jurassic dinosaur Allosaurus, each showing a previously-unreported feature: a sulcus, formed by a regular pattern of tightly packed horizontal slits, that runs vertically along the lateral surfaces of the centra and neural arches. These sulci are interpreted as the origin attachment sites of the CFL, allowing for direct determination of the muscle extent along the tail of this dinosaur. Anteriorly to the 18th caudal vertebra, the sulcus runs along most of the centrum and neural arch, then it progressively reduces its vertical extent, and disappears between caudals 24 and 32, a pattern consistent with previous CFL reconstructions in other theropods.