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A comprehensive chronic toxicity and carcinogenicity study was conducted on a series of Aroclors (1016, 1242, 1254, and 1260). Each Aroclor was assessed at multiple dietary concentrations, ranging from 25 to 200 ppm, for 24 months in male and female Sprague-Dawley rats. Liver toxicity was indicated by elevated serum enzyme activity (AST, ALT, and GGT), elevated serum cholesterol concentration, decreases in hematologic parameters (RBC, Hb, and Hct), hepatocellular hypertrophy, an increased incidence of altered hepatocellular foci, and an increased incidence of hepatocellular neoplasms (primarily adenomas). Liver toxicity was distinctly more severe in females than in males. The incidence of hepatocellular neoplasms was highly sex-dependent (females >> males), differed between Aroclor mixtures and, for females, increased with dose and followed the general incidence pattern of Aroclor 1254 > Aroclor 1260 approximately Aroclor 1242 > Aroclor 1016. A significant response (p < 0.05) in males was seen only for the high dose of Aroclor 1260. A small increase in the incidence of thyroid gland follicular cell adenomas was noted in males for Aroclors 1242, 1254, and 1260, with the incidence being uniform across dose groups and Aroclor mixtures. For females, increased survival relative to controls was observed for all Aroclor treatment groups. A significantly decreased trend in the incidence of mammary gland neoplasms compared to control was also noted for females receiving Aroclors 1242, 1254, and 1260.

BackgroundThe chasmosaurine ceratopsid Chasmosaurus is known from the Upper Cretaceous (Campanian) Dinosaur Park Formation of southern Alberta and Saskatchewan. Two valid species, Chasmosaurus belli and C. russelli, have been diagnosed by differences in cranial ornamentation. Their validity has been supported, in part, by the reported stratigraphic segregation of chasmosaurines in the Dinosaur Park Formation, with C. belli and C. russelli occurring in discrete, successive zones within the formation.Results/ConclusionsAn analysis of every potentially taxonomically informative chasmosaurine specimen from the Dinosaur Park Formation indicates that C. belli and C. russelli have indistinguishable ontogenetic histories and overlapping stratigraphic intervals. Neither taxon exhibits autapomorphies, nor a unique set of apomorphies, but they can be separated and diagnosed by a single phylogenetically informative character—the embayment angle formed by the posterior parietal bars relative to the parietal midline. Although relatively deeply embayed specimens (C. russelli) generally have relatively longer postorbital horncores than specimens with more shallow embayments (C. belli), neither this horncore character nor epiparietal morphology can be used to consistently distinguish every specimen of C. belli from C. russelli.Status of Kosmoceratops in the Dinosaur Park FormationKosmoceratops is purportedly represented in the Dinosaur Park Formation by a specimen previously referred to Chasmosaurus. The reassignment of this specimen to Kosmoceratops is unsupported here, as it is based on features that are either influenced by taphonomy or within the realm of individual variation for Chasmosaurus. Therefore, we conclude that Kosmoceratops is not present in the Dinosaur Park Formation, but is instead restricted to southern Laramidia, as originally posited.

Chasmosaurus irvinensis (sp. nov.) is distinguished from other species of this genus by the possession of a broad snout, absence of a brow horn (the position of which is occupied by a pit or rugosities suggestive of bone resorption), broadly rounded and open jugal notch, subrectangular squamosal, straight posterior parietal bar bearing 10 epoccipitals, eight of which are flattened, strongly curved anterodorsally, and nearly indistinguishably coossified to their neighbours, and small, transversely oriented parietal fenestrae restricted to the posterior portion of the frill. This species, restricted to the upper part of the Dinosaur Park Formation, is significantly younger than the other recognized Canadian Chasmosaurus species, C. belli and C. russelli. Phylogenetic analysis shows that C. irvinensis is most closely related to the other Canadian Chasmosaurus species and more distantly related to Chasmosaurus mariscalensis from Texas.Résumé : Chasmosaurus irvinensis (sp. nov.) se distingue des autres espèces de ce genre par son large boutoir, l'absence d'une corne sur le front (cette position est occupée par une fossette ou des rugosités qui suggèrent une résorption osseuse), une encoche jugale généralement arrondie et ouverte, un temporal presque rectangulaire, une barre pariétale postérieure droite comportant 10 époccipitaux, dont huit sont aplatis et fortement recourbés, dirigées en position antéro-dorsale et co-ossifiés à leurs voisins de façon presque indistincte, ainsi que de petites fenêtres pariétales à orientation transversale restreintes à la partie arrière de la collerette. Cette espèce, limitée à la portion supérieure de la Formation de Dinosaur Park, est beaucoup plus jeune que les autres espèces canadiennes de Chasmosaurus, C. belli et C. russelli. Une analyse phylogénique montre que C. irvinensis est plus étroitement lié aux autres espèces canadiennes de Chasmosaurus et moins étroitement lié au Chasmosaurus mariscalensis du Texas.[Traduit par la Rédaction] 1438Holmes et al.

Taphonomic biases dictate how organisms are represented in the fossil record, but their effect on studies of vertebrate diversity dynamics is poorly studied. In contrast to the high diversity and abundance of small-bodied animals in extant ecosystems, small-bodied dinosaurs are less common than their large-bodied counterparts, but it is unclear whether this reflects unique properties of dinosaurian ecosystems or relates to taphonomic biases. A new, fully domed pachycephalosaurid dinosaur, Acrotholus audeti, from the Santonian of Alberta predates incompletely domed taxa, and provides important new information on pachycephalosaur evolution and the completeness of the ornithischian fossil record. Here we provide the first empirical evidence that the diversity of small-bodied ornithischian dinosaurs is strongly underestimated based on ghost lineages and the high proportion of robust and diagnostic frontoparietal domes compared with other pachycephalosaur fossils. This suggests preservational biases have a confounding role in attempts to decipher vertebrate palaeoecology and diversity dynamics through the Mesozoic.

We use authentication tests developed for ancient DNA to evaluate claims by Asara et al. of collagen peptide sequences recovered from mastodon and Tyrannosaurus rex fossils. Although the mastodon passes, absence of amino acid composition data, lack of evidence for peptide deamidation, and association of the α1(I) peptide sequences with amphibians not birds, suggests that T. rex does not. CommentEarly reports of DNA preservation in multi-million year old bones (i.e. dinosaurs) have been largely dismissed (see 1 and SOM T1, 2) but reports of protein recovery are persistent (see 3 for review). Most of these studies used secondary methods of detection, but protein sequence, arguably the gold standard for molecular palaeontology, has now been claimed for the first time (2). Following initial optimism generated by reports of dinosaur DNA, there arose a gradual awareness of the problems and pitfalls which bedevil analysis of ancient samples (1), leading to a series of recommendations for future analysis (1, 4). As yet, there are no equivalent standards for fossil protein, so here we apply the recommended tests for DNA (4) to the authentication of the reported protein sequences (2) ( Table 1).* To whom correspondence should be addressed. E-mail: mc80@york.ac.uk. Europe PMC Funders Group Likelihood of collagen survivalThe extremely hierarchical structure of collagen results in unusual, catastrophic degradation (5) as a consequence of fibril collapse. The rate of collagen degradation in bone is slow because the mineral 'locks' the components of the matrix together, preventing helical expansion which is a pre-requisite of fibril collapse (6). The packing which stabilises collagen fibrils (6) also increases the temperature sensitivity of degradation (E a 173 kJ mol -1 ; Fig. 1). Collagen decomposition would be much faster in the T. rex buried in the then megathermal (>20 °C) (7) environment of the Hell Creek formation (collagen t ½ ~ 2 ka) than it would have been in the mastodon lying within the Doeden Gravel Beds (present day mean temperature 7.5 °C; collagen t ½ 130 ka; Fig. 1).

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