Hasil untuk "Fossil man. Human paleontology"

Wahiba Bel Haouz, Abdelouahed Lagnaoui, Christian Klug et al.

This article provides a description of the invertebrate trace fossils from the Hamar Laghdad region of Tafilalt in Morocco. These ichnoassemblages occur in Middle Devonian marly limestone layers, which are characterised by varying clastic content and different degrees of dolomitisation. These Eifelian and Givetian ichnoassemblages comprise: (i) Eifilian ichnoassemblages consisting of Arenicolites isp., Crescentichnus antarcticus, Selenichnites hundalensis and Osculichnus cf. labialis; (ii) a Givetian ichnoassemblage containing Arenicolites isp., Diplocraterion isp., Sinusichnus sinuosus, and Thalassinoides paradoxicus. The Eifelian strata were deposited in a moderately shallow inner shelf environment, which have been changed to a deeper inner shelf setting during the Givetian. This environment was characterised by high energy levels and a high concentration of organic matter. Some of these ichnotaxa are commonly referred to feeding of xiphosurans or trilobites, traces of suspension feeding and dwellings of polychaete worms and crustaceans, deposit-feeding non-decapod crustaceans, as well as deposit-feeding and dwelling of crustaceans. The present comprehensive ichnological analysis is important in at least three aspects: (1) it reports the oldest occurrences of Selenichnites and Sinusichnus in Africa and one of the oldest in the world; (2) It suggests a more ancient root for the represented complex behaviour of modern arthropods than previously thought; (3) It contributes to the understanding of the environmental deposit settings. The great palaeobiodiversity of Hamar Laghdad includes not only the skeletal record, but also ichnofossils. Both records indicate regional favourable environmental settings, characterised by local topography that varied over time and space, formed by several cold and hydrothermal seeps combined with sea-level fluctuations and currents.

Guilherme Hermanson, Serjoscha W. Evers

Abstract Ontogenetic shell shape changes of turtles are often only documented for individual species. It is currently unclear how shell shape changes during ontogeny across species, if there are common trends, and at what point in ontogeny individuals reach their adult morphology. Inspired by questions of whether some morphologies are too juvenile to be included into macroevolutionary studies of shell shape, we develop ontogenetic shell shape curves based on landmarked 3D shell shapes of turtles. Species-specific allometric shape regressions confirm that turtles show marked ontogenetic shell shape change. Geometric morphometric analysis shows that juvenile turtles have rounded shells, and ontogenetic differentiation between species increases adult turtle disparity. Disparity analysis indicates that juvenile shells across turtle clades are more similar than adult shapes, suggesting an important role of developmental constraints on early turtle shell shape, and possible adaptive post-natal ontogenetic changes that produce the observed adult shell shape disparity. Ontogenetic shell shape curves indicate when turtles converge onto adult morphologies, here quantified as 85% the distance between juvenile shape and maximum size adult shape. This happens at about 65% of the species-specific maximum carapace sizes. Sexual shell shape dimorphism is comparatively low across turtles even in the presence of pronounced sexual size dimorphism. These preliminary results provide guidance for studying shell shape macroevolution, but need to be scrutinized further in the future by data addition.

Danxia Gao, Cen Shen, Liebin Huang et al.

Abstract Scolecodonts are the fossilised jaw apparatus of polychaetes, with fossil records dating back to the Late Cambrian. However, they are commonly found in Ordovician, Silurian and Devonian strata. Here, we describe three species—Langeites aff. glaber, Langeites sp., and Oenonites spp. from the Miaogao Formation in Yiliang, Yunnan, South China. A comparative morphological study on the maxillary apparatus of the family Paulinidae and the extant members of Eunicidae and Onuphidae was conducted. This study aims to evaluate evolutionary changes in the maxillary apparatus, particularly the first maxilla, within the eulabidognatha-type apparatus. To infer their palaeoecology, Langeites aff. glaber and Langeites sp. were compared with modern species of Eunicidae and Onuphidae based on their complex maxillary apparatus. The similarity between these fossil and extant taxa suggests that Langeites retained similar feeding habits over time. These scolecodonts represent a new record for the Late Silurian of South China, and extend the geographical range of the genus Langeites. As a genus restricted to the Silurian, Langeites has potential applications in stratigraphic correlation for the Late Ludlow to Early Pridoli.

Denis A. Ponce, Ignacio A. Cerda, Julia B. Desojo

Pseudosuchians were the dominant group of archosaurs on continental ecosystems during the Triassic. However, studies that report palaeopathologies based on osteohistological evidence in this group are scarce. Here, two cases of palaeopathologies found in appendicular bones of two clades of pseudosuchians are presented: Aetosauria, a distal fragment of the fibula of Aetosauroides scagliai and Erpetosuchidae, the distal half of the tibia of Tarjadia ruthae from the Ischigualasto and Chañares formations, respectively (province of La Rioja, Argentina). The cortex in both specimens is composed of woven-fibred bone in the deepest part and by parallel-fibred bone in the subperiosteum. Towards the outermost portion of the cortex, a thin layer of periosteal bone with an irregular margin is recorded, mainly formed by a fibrolamellar bone vascularized with relatively wide and anastomosed radial canals. These features are compatible with a specific tissue recognized in pathological conditions, the radial fibrolamellar bone (RFB), generated by periosteal reactive bone. Additionally, a thin layer of parallel-fibred/lamellar bone crossed this structure in A. scagliai and surrounding the outermost portion in both specimens. The presence of RFB shows an abnormally accelerated bony overgrowth. However, due to the short thickness of this layer and the subsequent formation of parallel-fibred bone, it indicates a slowdown in its development and a possible recovery of the pathological condition. The configuration of the injury is compatible with periostitis and it constitutes the first record of this type of pathologies in non-crocodylomorph pseudosuchians. As the causes for this benign injury, it is inferred a non-traumatic stress followed by a pyogenic infection.

Juliette C. L. Menon, Donald B. Brinkman, Guilherme Hermanson et al.

Abstract The early evolution of Pan-Chelonioidea (sea turtles) is poorly understood. This is in part due to the rarity of undeformed skulls of definitive early stem chelonioids. In this work, we redescribe the holotype of Nichollsemys baieri using µCT scans and segmentations of the skull. This fossil is the best 3D preserved skull of any Campanian sea turtle, and includes partial “soft tissue” preservation. Nichollsemys is morphologically similar but clearly distinct from Toxochelys spp., and both show a mosaic of plesiomorphic and derived chelonioid features. The internal cranial anatomy documents the presence of derived characters in Nichollsemys baieri that are absent in Toxochelys spp., such as the loss of the epipterygoids and the rod-like shape of the rostrum basisphenoidale. Among the numerous plesiomorphic characters is the presence of a splenial bone, which was unnoticed before. An updated phylogenetic analysis retrieves Nichollsemys baieri as a non-protostegid early stem chelonioid in a slightly more crownward position than Toxochelys latiremis. Our phylogeny includes macrobaenids and protostegids as pan-chelonioids, and we find unorthodox results for dermochelyids. Thus, although Nichollsemys baieri provides important new insights into the early morphological evolution of sea turtles, much work remains to be done. As a completely 3D preserved specimen, we included Nichollsemys baieri into a recent landmark-based skull shape dataset of turtles. Morphospace analysis reveals an intermediate position between cryptodires and crown chelonioids. Based on these data, we also predict that Nichollsemys baieri was still capable of neck retraction, constraining the loss of this trait to more crownward pan-chelonioids.

SAMUEL ZAMORA, JUAN CARLOS GUTIÉRREZ-MARCO

Solutans were among the most enigmatic pre-radial and asymmetric echinoderms. A new species Dehmicystis ariasi sp. nov. is described from the upper part of the Llagarinos Formation, lower Ludlow (Silurian) of Northwest Spain. This is the first solutan formally described from Iberia and the first from the Silurian worldwide. Dehmicystis was previously known based on a small number of poorly preserved specimens from the Emsian, Lower Devonian Hunsrück Slate of Germany. New observations based on the newly studied material suggest that Dehmicystis displayed a feeding appendage facing towards the substrate, and the periproct on the opposite face of the theca. Comparisons with other solutans and new data suggest that Dehmicystis was a detritus feeder that moved over the substrate capturing organic particles from the sediment with a single feeding arm.

BRADLEY MCFEETERS, DAVID C. EVANS, HILLARY C. MADDIN

Five new partial skulls of the hadrosaurid dinosaur Maiasaura peeblesorum from the Linster Quarry bone bed (Two Medicine Formation, Campanian) in Montana, USA, provide the basis for a description of the skull roof and braincase morphology of this taxon. These skulls additionally form an ontogenetic series consisting of one subadult, two small “intermediate adults”, and two larger “mature adults”. The subadult skull is approximately two thirds as wide as the largest adult and lacks a nasofrontal crest, suggesting that the crest formed relatively late in ontogeny compared to some other hadrosaurids. As in closely related taxa, larger skulls of M. peeblesorum have a proportionately wider braincase and a larger, more rugosely ridged nasofrontal contact for supporting a larger crest. In the two largest adults, the skull roof incipiently overhangs the anterior margin of the dorsotemporal fenestrae. In the largest skull examined, the crest is semicircular in anterior view and incorporates flared, anteriorly concave prefrontals in its lateral margins. Intraspecific variation in M. peeblesorum is observed in cranial characters previously discussed as interspecific variation in related taxa, including the prominence of dorsal depressions on the frontal, and the position of the foramen for the facial nerve (CN VII). Although cranial ontogeny in Maiasaura shares some trends with Brachylophosaurus and Probrachylophosaurus, it deviates in other ways from the previous heterochronic model proposed for the evolution of Maiasaurini.

Adam T. Halamski, Jiří Kvaček, Marcela Svobodová et al.

Late Cretaceous plants from the North Sudetic Basin (Lower Silesia, south-western Poland) are reviewed on the basis of megaflora from 17 localities (270 identifiable specimens), mesoflora from two localities, and microflora from four localities. Major sites are Rakowice Małe and Bolesławiec. Eight megafloral assemblages are distinguished (Assemblage 1, Turonian; Assemblages 2, 3, lower–middle Coniacian; Assemblages 4, 5, upper Coniacian?–lower Santonian?; Assemblages 6–8, lower–middle Santonian); the bulk of the palaeoflora is from Assemblages 4–6 and 8. Megaflora consists of 29 taxa (6 ferns, 4 conifers, and 19 angiosperms). Geinitzia reichenbachii is the most common species. Dryophyllum westerhausianum (Richter, 1904) Halamski and Kvaček comb. nov. is a trifoliolate leaf re-interpreted as a representative of Fagales. Three species of Dewalquea are distinguished: Dewalquea haldemiana, Dewalquea insignis, and Dewalquea aff. gelindenensis. Platanites willigeri Halamski and Kvaček sp. nov. is characterised by trifoliolate leaves, the median leaflet of which is ovate, unlobed, with a serrate margin, and cuneate base. Palaeocommunities inferred from the megafossil record include: a back swamp forest dominated by Geinitzia, with abundant ferns; a Dryophyllum-dominated riparian forest; a forest with Dewalquea and Platanites willigeri possibly located in the marginal part of the alluvial plain; dunes with D. haldemiana and Konijnenburgia; a fern savanna with patches of Pinus woodlands. Palynoassemblage A from the Nowogrodziec Member, studied mostly at Rakowice Małe and Żeliszów, consists of 126 taxa, including 105 terrestrial palynomorphs (54 bryophyte, lycophyte, and pteridophyte spores, 16 gymnosperms, 35 angiosperms). The mega- and mesofossil records are dominated by angiosperms; the palynoassemblages are dominated by ferns. Palaeocommunities represented solely by the microfossil record are halophytic (with Frenelopsis and unconfirmed presence of Nypa) and pioneer vegetation. Palaeocommunities are intermediate in general character between those pre-dating the Cretaceous Terrestrial Revolution and modern, angiosperm- dominated vegetation. In comparison to older plant assemblages from contiguous areas laurophylls are much rarer; this might correspond to a real phenomenon of exclusion of lauroids from Santonian riparian forests. The studied assemblage is more similar to younger palaeofloras than to older ones; this might be interpreted as stabilisation of communities after a period of pronounced change related to the rise to dominance of the angiosperms. In contrast to widespread endemism among vertebrates of the European Archipelago, the plant cover consists mostly of species that are widely distributed.

Georgios L. Georgalis, Gianni Insacco, Lorenzo Rook et al.

Abstract We here describe turtle remains from the late Miocene (Tortonian) of Cessaniti (Calabria, southern Italy), an area that recently has been palaeogeographically reconstructed as being, at that time of the Neogene, directly connected (or at least rather proximate) to northern Africa, instead of Europe. The material pertains to three different turtle clades, i.e., pan-trionychids, pan-cheloniids, and pan-geoemydids. Although the material is incomplete, it nevertheless permits a more precise identification for the pan-trionychid specimens, which are referred to the species Trionyx pliocenicus, as well as the pan-geoemydid, which is attributed to the genus Mauremys. Especially for the case of T. pliocenicus, the new Cessaniti specimens expand its geographic and stratigraphic distribution and further comprise the sole existing material known for this species, considering that its holotype and so far only known material is currently lost. Overall, besides its taxonomic significance, the Cessaniti chelonian assemblage affords the potential for important biogeographic implications, attesting that the lineages of Trionyx and Mauremys could have potentially used the Sicily–Calabria arch for their dispersal from Europe to Africa during the Tortonian. The new turtle specimens further complement the associated mammal remains in envisaging the Cessaniti assemblage as a mosaic of both African and Eurasian (Pikermian) faunal elements.

Martín Zamorano

Exceptionally well-preserved material from a fossil mammal is presented. For the first time, several fragments of tracheal rings and cricoid cartilage assigned to Panochthus sp. (Xenarthra; Glyptodontidae) from the Late Pleistocene of Argentina are described in detail and figured. In this contribution, in addition to a meticulous description, a tracheal ring was reconstructed and compared to tracheal rings of domestic and wild mammals. As a result, among domestic mammals it is similar to those of Sus scrofa domestica (domestic pig), and among wild mammals to those of Zalophus californianus (California sea lion). Tracheal rings of fossil vertebrates have been recognized in birds (Cariamiformes and Anseriformes) and other dinosaurs (Theropoda). This is likely the first report of tracheal rings in a fossil mammal; future comparisons with extant xenarthrans could provide information on the paleobiological implications of this structure in glyptodonts, and allow making inferences about other fossil mammals.

Lorena L. Musotto, María S. Candel, Ana M. Borromei et al.

Resumen. En esta contribución se exponen los materiales estudiados, las metodologías de muestreo y las técnicas de laboratorio utilizadas para el análisis palinológico de turberas y depósitos marinos del Archipiélago de Tierra del Fuego. Asimismo, se evalúan las limitaciones y fortalezas del análisis de indicadores biológicos (polen, esporas, microplancton de pared orgánica y hongos). Finalmente, se presentan tres casos de estudio donde se ilustra: i) el análisis de microfósiles fúngicos como complemento para el estudio de los registros polínicos, ii) las relaciones entre los cambios en las comunidades vegetales y eventos climáticos, y iii) el uso del análisis polínico y de palinomorfos acuáticos para la caracterización de los ambientes costeros a lo largo del Canal Beagle. Palabras clave. Polen. Microfósiles fúngicos. Palinomorfos acuáticos. Paleoambientes. Argentina. Abstract. PALINOLOGY AS A TOOL FOR THE CHARACTERIZATION OF CONTINENTAL AND MARINE ENVIRONMENTS OF LATE QUATERNARY IN THE TIERRA DEL FUEGO ARCHIPELAGO. In this contribution, we describe the studied materials, sampling methodologies and laboratory techniques used for the palynological analysis of peatbogs and marine deposits of the Tierra del Fuego Archipelago. Likewise, the limitations and strengths of the analysis of biological indicators (pollen, spores, organic-walled microplankton and fungi) are evaluated. Finally, we present three case studies which illustrate: i) fungal microfossil analysis as a complement to the study of pollen records; ii) relationships between plant community changes and climatic events; and iii) the use of pollen and aquatic palynomorph analyses for the characterization of the coastal environments along the Beagle Channel.  Key words. Pollen. Fungal microfossils. Aquatic palynomorphs. Palaeoenvironments. Argentina.

Łucja Fostowicz-Frelik, Jingmai K. O’Connor

Sankar Chatterjee 2015. The Rise of Birds. 225 Million Years of Evolution. Second Edition. 370 pp. Johns Hopkins University Press. ISBN 978-1-4214-1590-1 (hardcover). Price $59.95; e-book $59.95.

Michael Stein, Michael Archer, Suzanne J. Hand

Instances of dwarfism in the fossil record are of interest to palaeontologists because they often provide insight into aspects of palaeoecology. Fossil species of Australian-Pacific mekosuchine genus Mekosuchus have been described as dwarf, primarily terrestrial crocodiles, in contrast with the nearly ubiquitous semi-aquatic habitus of extant crocodilians (Willis 1997). This hypothesis has been difficult to test because of limited knowledge of the cranial and postcranial skeleton of extinct taxa and the continuous nature of crocodilian growth. New crocodilian vertebral material from Riversleigh, northwestern Queensland, tentatively referred to Mekosuchus whitehunterensis Willis, 1997, displays morphological maturity indicative of adult snout-vent length little over a half-meter, proportionally smaller than extant dwarf taxa. Further, this material displays morphology that indicates a relatively large epaxial neck musculature for its body-size. These attributes suggest this dwarf mekosuchine employed unusual feeding behaviours. The ability to perform normal death-roll, de-fleshing behaviours would be limited in a mekosuchine of such small size. Given the powerful neck muscles and other anatomical features, it is more likely that this mekosuchine killed and/or dismembered its prey using a relatively forceful lifting and shaking of the head.

Nirina O. Ratsimbaholison, Ryan N. Felice, Patrick M. O’Connor

Abelisaurid theropods were one of the most diverse groups of predatory dinosaurs in Gondwana during the Cretaceous. The group is characterized by a tall, wide skull and robust cervical region. This morphology is thought to have facilitated specialized feeding behaviors such as prolonged contact with prey. The Late Cretaceous abelisaurid Majungasaurus crenatissimus typifies this abelisaurid cranial morphotype. Recent fossil discoveries of this species include a partial growth series that allows for the first time an investigation of ontogenetic variation in cranial morphology in a representative abelisaurid. Herein we examine growth trajectories in the shape of individual cranial bones and articulated skulls of Majungasaurus using geometric morphometrics. Several major changes in skull shape were observed through ontogeny, including an increase in the height of the jugal, postorbital, and quadratojugal, an increase in the extent of the contacts between bones, and a decrease in the circumference of the orbit. The skull transitions from relatively short in the smallest individual to tall and robust in large adults, as is seen in other theropods. Such morphological change during ontogeny would likely have resulted in different biomechanical properties and feeding behaviors between small and large individuals. These findings provide a post-hatching developmental framework for understanding the evolution of the distinctive tall skull morphology seen in abelisaurids and other large-sized theropod dinosaurs.

Edgardo Ludueña

Historia del Museo Casa Ameghino de Luján

Sergio Archangelsky

A new lithostratigraphic scheme has been proposed for the previous Baqueró Formation (Santa Cruz Province, Argentina), which is now considered to be a Group including three formations: Anfiteatro de Ticó the oldest, Bajo Tigre the middle and Punta del Barco the youngest. The distribution of plant fossils at several localities where these formations occur has shown that there are two different plant assemblages that are consistently present over a wide area. A detailed study of the distribution of all plant species known to be present in the Baqueró Group led to define two biozones, viz. Ptilophyllum (lower) and Gleichenites (upper). The main differences concern the disappearance of all Bennettites and most Cycads and Ginkgoales in the upper biozone, which in turn is clearly dominated by a gleicheniaceous fern assemblage. The latest Barremian to early Aptian age that has so far been accepted for this fossil flora, and the change of components in both biozones, suggests that this time interval may well correspond to the late Barremian to Early Aptian extinction event that has been proposed in other regions. This event was closely related to a strong volcanic activity that has also been recorded in the Baqueró Group. It is suggested that the vegetation during the time span represented by the Baqueró Group developed under stressful conditions that caused extinctions and a consequent change of the environmental scenario. KEY WORDS. Argentina. Patagonia. Early Cretaceous. Paleobotany. Biostratigraphy.

Juan Carlos Gamerro

Paleopalinología su evolución en la Argentina

Silvina de Valais

Hexapodichnus casamiquelai isp. nov.: an insect trackway from the La Matilde Formation (Middle Jurassic), Santa Cruz, Argentina

Pedro R. Gutierrez

An Upper Paleozoic palynological assemblage from the Cerro Agua Negra Formation, Calingasta-Uspallata Basin, San Juan Province, Argentina, is described for the first time. The sporomorphs have been recovered at Las Leñas Creek from carbonaceous shales, which have been deposited in a subaerial environment corresponding to alluvial plain and interdistributary bays facies. The stratigraphic significance of the miospore assemblage is discussed.

Fabiana Latorre

Airborne pollen concentration in the Mar del Plata atmosphere was analyzed during two consecutive years. Also plant sources and flowering development was studied. Quercus was the selected taxon. Pollen amount depends on plant number and spatial distribution. Pollen patterns agree with floral phenology. Q. robur productivity was higher in 1993 due to better conditions before flowering time. On the contrary Q. ilex annual sum was higher in 1994; a cyclic reproductive rhythm is postulated. Meteorological conditions during dispersion are not enough to explain interannual variability. KEY WORDS. Airborne pollen. Flowering phenology. Productivity. Dispersion. Urban vegetation.