Search

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the coronavirus disease 2019 (COVID-19), is having a deep impact across the globe. As of 4 February 2021, over [...]

Three monodominant hadrosaurid bonebeds in the Horsethief Member of the Horseshoe Canyon Formation (uppermost Campanian) in southern Alberta, Canada, are documented. Each bonebed is hosted by a decimetre-thick deposit of poorly sorted and graded organic-fragment-rich mudstone. These fossil deposits are interpreted as having been carried and deposited by debris flows or hyperconcentrated mass sediment flows initiated by overbank flooding from local channels. Each bonebed is dominated (>50% of identifiable elements) by the disarticulated to occasionally associated remains of hadrosaurine hadrosaurids, inferred to be Edmontosaurus regalis. The majority of hadrosaurid elements at two of the sites (Bleriot Ferry and Prehistoric Park) are from large, presumably adult-sized individuals, whereas the majority of elements from the Fox Coulee site are from subadults and juveniles. Fossil elements from all the sites exhibit similar taphonomic signatures suggestive of a high degree of biostratinomic modification including: (i) thorough disarticulation of carcasses, (ii) a large amount of breakage, (iii) modest amounts of size sorting, and (iv) minimum to modest occurrences of abrasion, and scratch and tooth marks. These signatures indicate that carcasses were exposed for significant amounts of time on the floodplain, where they rotted, were scavenged and trampled, and were exposed to moving water prior to final burial. The size of each bonebed together with the density of bones suggest that the biocoenoses comprised large groups of hadrosaurids, and bone size distributions suggest the possibility of age-segregated populations. The monodominant nature of the assemblages combined with homogenous taphonomic signatures within and between sites suggests that these bonebed assemblages are best interpreted as the result of mass kills rather than attrition, with recurring tropical storm-induced coastal-plain flooding postulated as a likely mechanism for what killed and eventually buried these dinosaurs. Resume : Trois lits a ossements a monodominance d'hadrosaurides du Membre de Horsethief de la Formation de Horseshoe Canyon (Campanien sommital) dans le sud de l'Alberta (Canada) sont documentes. Chaque lit a ossements se trouve dans un depot d'epaisseur decimetrique de mudstone mal classe et granoclasse riche en fragments organiques. Ces gisements fossiliferes sont interpretes comme ayant ete transportes et deposes par des coulees de debris ou des coulees de masse de sediments hyperconcentrees initiees par l'inondation des berges par des chenaux locaux. Chaque lit a ossements est domine (>50 % des elements identifiables) par les restes desarticules a occasionnellement associes d'hadrosaurides hadrosaurines, presumes etre d'Edmontosaurus regalis. La majorite des elements d'hadrosauride a deux des sites (Bleriot Ferry et Prehistoric Park) proviennent de grands individus presumes etre de taille adulte, alors que la majorite des elements du site de Fox Coulee proviennent d'individus subadultes et juveniles. Les elements fossiles de tous les sites presentent des signatures taphonomiques semblables qui indiqueraient un degre eleve de modification biostratinomique comprenant (i) la desarticulation complete des carcasses, (ii) beaucoup de bris, (iii) peu de classement selon la taille et (iv) une frequence faible a moderee de signes d'abrasion et de marques d'egratignure et de morsure. Ces signatures indiquent que les carcasses ont passe beaucoup de temps sur la plaine inondable, ou elles ont pourri, ont ete recuperees par des detritivores et pietinees et ont ete exposees a de l'eau en mouvement avant leur enfouissement definitif. La taille de chaque lit a ossements combinee a la densite d'ossements donne a penser que les biocenoses comprenaient de grands groupes d'hadrosaurides, et les distributions de tailles des os laissent croire a la possibilite de populations segregees selon l'age. Etant donne le caractere monodominant des assemblages, combine aux signatures taphonomiques homogenes au sein des sites et entre eux, la meilleure interpretation de ces assemblages de lit a ossements serait qu'ils resultent d'evenements de mortalite massive plutot que de l'attrition, le mecanisme postule ayant cause ces evenements de mortalite et, a terme, l'enfouissement des dinosaures etant l'inondation repetee de plaines inondables induite par des tempetes tropicales. [Traduit par la Redaction], Introduction Monodominant hadrosaurid (Dinosauria, Ornithischia) bonebeds are common in Upper Cretaceous (Campanian-Maastrichtian) strata of western North America, and they have been reported for numerous taxa, including Maiasaura peeblesorum (Varricchio and [...]

Previously reported and new specimens of marine turtles from the late Campanian of Alberta, Canada, provide additional information on the diversity and distribution of chelonioid turtles at this time. An articulated carapace from the Bearpaw Formation previously interpreted as Lophochelys niobrarae is considered to be a juvenile of a specifically indeterminate chelonioid and is referred to Lophochelys sp. Isolated neurals and a hyoplastron from nonmarine estuarine deposits in the uppermost beds of the Dinosaur Park Formation are tentatively referred to Lophochelys sp. These specimens suggest that this chelonioid could enter freshwater environments. A new chelonioid, Kimurachelys slobodae gen. et sp. nov., is recognized on the basis of two mandibles and a maxilla from the uppermost beds of the Dinosaur Park Formation of southeastern Alberta. A partial postcranial skeleton of an indeterminate chelonioid from the Bearpaw Formation provides additional evidence that chelonioids of this formation included taxa that were phylogenetically intermediate between chelonioids of the late Santonian and members of the crown group. Des specimens deja signales et de nouveaux specimens de tortues de mer du Campanien tardif de l'Alberta (Canada) fournissent de nouveaux renseignements sur la diversite et la repartition des tortues chelonioides a cette epoque. Une carapace articulee de la Formation de Bearpaw precedemment interpretee comme appartenant a Lophochelys niobrarae est consideree provenir d'un chelonioide juvenile d'espece indeterminee et est affecte a Lophochelys sp. Des os neuraux isoles et un hyoplastron provenant de depots estuariens non marins dans les lits sommitaux de la Formation de Dinosaur Park sont provisoirement affectes a Lophochelys sp. Ces specimens donnent a penser que ce chelonioide pouvait penetrer dans des milieux d'eau douce. Un nouveau chelonioide, Kimurachelys slobodae gen. et sp. nov., est reconnu sur la base de deux mandibules et d'une maxille dans les lits sommitaux de la Formation de Dinosaur Park du sud-est de l'Alberta. Un squelette postcranien partiel d'un chelonioide indetermine de la Formation de Bearpaw fournit d'autres preuves du fait que les chelonioides de cette formation comprenaient des taxons intermediaires sur le plan phylogenique entre les chelonioides du Santonien tardif et les membres du groupecouronne. [Traduit par la Redaction], Introduction Marine turtles of Late Cretaceous age from the Western Interior of North America are of interest because they document early stages in the evolution of the Chelonioidea (Zangerl 1953; [...]

Taking an evolutionary approach to the question of beauty, we discuss the expression and perception of sexual beauty across the animal kingdom. Animals experience beauty in their brains, and animal brains are tuned to features of the environment most relevant to their survival. Over evolutionary time, sexually reproducing animals have exploited that tuning to maximize their attractiveness to the opposite sex, often leading to extreme courtship traits and behaviors. These are the traits of sexual beauty. Combining modern principles of neuroscience and neuroaesthetics with established principles of evolutionary biology, we aim to understand the biological basis and evolution of beauty in all animals, including ourselves. [ABSTRACT FROM AUTHOR]