8 research outputs found
The skull of Epidolops ameghinoi from the early Eocene Itaboraí fauna, southeastern Brazil, and the affinities of the extinct marsupialiform order Polydolopimorphia
The skull of the polydolopimorphian marsupialiform Epidolops ameghinoi is described
in detail for the first time, based on a single well-preserved cranium and associated left
and right dentaries plus additional craniodental fragments, all from the early Eocene
(53-50 million year old) Itaboraí fauna in southeastern Brazil. Notable craniodental
features of E. ameghinoi include absence of a masseteric process, very small
maxillopalatine fenestrae, a prominent pterygoid fossa enclosed laterally by a
prominent ectopterygoid crest, an absent or tiny transverse canal foramen, a simple,
planar glenoid fossa, and a postglenoid foramen that is immediately posterior to the
postglenoid process. Most strikingly, the floor of the hypotympanic sinus was
apparently unossified, a feature found in several stem marsupials but absent in all
known crown marsupials. "Type II" marsupialiform petrosals previously described from
Itaboraí plausibly belong to E. ameghinoi; in published phylogenetic analyses, these
petrosals fell outside (crown-clade) Marsupialia. "IMG VII" tarsals previously referred to
E. ameghinoi do not share obvious synapomorphies with any crown marsupial clade,
nor do they resemble those of the only other putative polydolopimorphians represented
by tarsal remains, namely the argyrolagids. Most studies have placed
Polydolopimorphia within Marsupialia, related to either Paucituberculata, or to
Microbiotheria and Diprotodontia. However, diprotodonty almost certainly evolved
independently in polydolopimorphians, paucituberculatans and diprotodontians, and
Epidolops does not share obvious synapomorphies with any marsupial order.
Epidolops is dentally specialized, but several morphological features appear to be
more plesiomorphic than any crown marsupial. It seems likely Epidolops that falls
outside Marsupialia, as do morphologically similar forms such as Bonapartherium and
polydolopids. Argyrolagids differ markedly in their known morphology from Epidolops
but share some potential apomorphies with paucituberculatans. It is proposed that
Polydolopimorphia as currently recognised is polyphyletic, and that argyrolagids (and
possibly other taxa currently included in Argyrolagoidea, such as groeberiids and
patagoniids) are members of Paucituberculata. This hypothesis is supported by
Bayesian non-clock phylogenetic analyses of a total evidence matrix comprising DNA
sequence data from five nuclear protein-coding genes, indels, retroposon insertions
and morphological characters: Epidolops falls outside Marsupialia, whereas
argyrolagids form a clade with the paucituberculatans Caenolestes and Palaeothentes,
regardless of whether the Type II petrosals and IMG VII tarsals are used to score
characters for Epidolops or not. There is no clear evidence for the presence of crown
marsupials at Itaboraí, and it is possible that the origin and early evolution of
Marsupialia was restricted to the "Austral Kingdom" (southern South America,
Antarctica, and Australia)
Associations between toenail arsenic concentration and dietary factors in a New Hampshire population
BACKGROUND: Dietary factors such as folate, vitamin B12, protein, and methionine are important for the excretion of arsenic via one-carbon metabolism in undernourished populations exposed to high levels of arsenic via drinking water. However, the effects of dietary factors on toenail arsenic concentrations in well-nourished populations exposed to relatively low levels of water arsenic are unknown. METHODS: As part of a population-based case–control study of skin and bladder cancer from the USA, we evaluated relationships between consumption of dietary factors and arsenic concentrations in toenail clippings. Consumption of each dietary factor was determined from a validated food frequency questionnaire. We used general linear models to examine the associations between toenail arsenic and each dietary factor, taking into account potentially confounding effects. RESULTS: As expected, we found an inverse association between ln-transformed toenail arsenic and consumption of vitamin B12 (excluding supplements) and animal protein. Unexpectedly, there were also inverse associations with numerous dietary lipids (e.g., total fat, total animal fat, total vegetable fat, total monounsaturated fat, total polyunsaturated fat, and total saturated fat). Finally, increased toenail arsenic concentrations were associated with increased consumption of long chain n-3 fatty acids. CONCLUSION: In a relatively well-nourished population exposed to relatively low levels of arsenic via water, consumption of certain dietary lipids may decrease toenail arsenic concentration, while long chain n-3 fatty acids may increase toenail arsenic concentration, possibly due to their association with arsenolipids in fish tissue