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New Papers in _PALAIOS_ and _American Museum Novitates_



New in PALAIOS ...

  Hollocher, K. T., O. A. Alcober, C. E. Colombi, & T. C, Hollocher. 2005.
   Carnivore coprolites from the Upper Triassic Ischigualasto Formation,
   Argentina: Chemistry, mineralogy, and evidence for rapid initial
   mineralization. _PALAIOS_ 20(1):51-63.

Abstract:
  "Coprolites were collected 74 m above the base of the Upper Triassic
Ischigualasto Formation of northwestern Argentina and their chemistry,
mineralogy, and textures were studied to infer their biological source and
taphonomy. They were found to contain a few fragments of bone and much
crystalline apatite, and so can be assigned to carnivores able to digest
bone. Primary minerals derived from endogenous materials were apatite and
pyrite, and secondary minerals derived from ground water were chiefly
calcite and glauconite in one coprolite and glauconite in another. Primary
apatite, presumed originally to have been mostly dahllite (a carbonate
hydroxyapatite) precipitated from digested bone, was converted to
francolite (a carbonate fluorapatite) during diagenesis through the
introduction of fluoride from ground water. The chemistry, mineralogy, and
structure of the coprolites suggest an early onset of mineralization,
early anaerobic burial, and a recent anaerobic-to-aerobic transition
during weathering. The chemistry of the coprolites is consistent with the
stratigraphic identification of the coprolite horizon as an ancient flood
plain."

Tidbit from the paper on stratigraphy...

  "The Ischigualasto Formation occurs in the Ischigualasto-Via Union Basin
along the border between San Juan and La Rioja provinces in northwestern
Argentina. This rift basin preserves nearly 4000 m of Middle to Upper
Triassic continental sediments (Milana and Alcober, 1994; Alcober, 1996).
The Upper Triassic Ischigualasto Formation represents a ~340-meter thick
section within the basin that is remarkable for the great abundance and
excellent preservation of fossil vertebrates (Bonaparte, 1967, 1978;
Sereno, 1994; Alcober, 1996). The Ischigualasto Formation is composed of
mostly upland fluvial sediments that include meandering- and braided-river
channels, overbank and flood-plain deposits, and lake sediments (Rogers et
al., 1993; Milana and Alcober, 1994; Colombi 2001, 2002). It has been
dated at 228 Ma by Ar/Ar methods using sanidine from the Herr Toba
bentonite (Rogers et al., 1993), which is located 20 m above the base of
the Formation and ~54 m below the horizon containing the coprolite samples
described herein. A sedimentary interval of 54 m is estimated to have
required a time for deposition of less than 500,000 years (Rogers et al.,
1993). The Ischigualasto Formation is underlain by the older Los Rastros
Formation exposed to the southwest, which has yielded few vertebrate
fossils to date, and is overlain by the younger Los Colorados Formation
exposed to the northeast, which contains some well-preserved vertebrate
fossils."

  Also ... "Most of these coprolites contain scales of ganoid fish (e.g.,
*Pholidophorus dentatus*) and, on the basis of very fragmentary fossil
remains, were attributed to the aetosaur Typothorax punctulatus (Rusconi
1947, 1949) or to a carnivorous archosauriform, such as *Stegomosuchus*
(Reig, 1961) or *Cuyosuchus huenei* (Desojo, 2001; Desojo et al., 2002).
The last is the only archosauriform identified to date in the Cuyo Basin."
... and ... "At the coprolite locality and along strike, this 3-meter
sequence contains the remains of Triassic vertebrates, particularly the
rhynchosaur *Scaphonyx,* as well as cynodonts and the early theropod
dinosaur *Herrerasaurus*."

  The authors note that because of all carnivores in the formation capable
of producing the coprolite (being able to ingest and disolve bone, and
also _likely_ to do so), the culprit who laid these coprolites was more
likely to be *Herrerasaurus* than any of the aforementioned other
archosauriforms.

---

  Friedrich, O., Nishi H., J. Pross, G. Schmiedl, and C. Hemleben. 2005.
   Millennial- to centennial-scale interruptions of the OIceanic Anoxic
   Event 1b (Early Albian, mid-Cretaceous) inferred from benthic
   foraminiferal repopulation events. _PALAIOS_ 20(1):63-77.

Asbtract:
  "The Early Albian Oceanic Anoxic Event 1b (OAE 1b) black shale is
interrupted by one or more ventilation events that display significant
changes in benthic and planktic populations. Within the OAE 1b sections
studied, at ODP Site 1049, DSDP Site 545, and the Vocontian Basin, the
benthic foraminiferal repopulation events last between ~500 and ~1,250
years and occur with a cyclicity of approximately 5.7 kyr. This period may
represent an amplitude modulation of the precessional cycle. The OAE 1b
sections from the marginal setting of the Vocontian Basin exhibit up to
eight repopulation events. In contrast, there is only one repopulation
event identified in the Atlantic OAE 1b sections from the Mazagan Plateau
(DSDP 545) and Blake Nose (ODP 1049). Within the margin of dating
uncertainties, this supraregional repopulation event occurred
synchronously in the Vocontian Basin and the Atlantic Ocean. While the OAE
1b black shale formed under extremely warm and humid conditions, the
repopulation events occurred during intervals of short-term cooling and
reduced humidity at deep-water formation sites. The resulting increase in
evaporation led to enhanced formation of low-latitude deep water, thus
improving the ventilation of the sea floor."

  But yes, the Oceanic Anoxic Event had phases where it wasn't so anoxic
and thus allowed repopulation of the environment, permissive of other
anoxic events to show marine extinctions from anoxia may not actually all
be total, but only observation based on limited data. Suggests the anoxic
event associated with the Permian Extinction should be looked at in
detail. Which leads me into a reply to a point raised about bow
dicynodonts survived the Permian Mass Extinction prior to the Triassic
onset, and common statements about percentages of loss of life: nearly all
the life at the time appear to have been insectan, plant, and marine in
nature, which were more highly susceptible than the amniotes to which seem
to have kinda "walked" through to the Triassic. Biodiversity was not
wholly terrestrial, and there was a major biotic mass shift towards the
marine realm and delicate atmospheric balances to which plants and insects
are more susceptible than vertebrates, so the criticism is unwarranted.

---

  The January batch of _AMNovitates_ is mostly about arthropods, but this
one vertebrate did show up, even if it's just a fragement of jaw and a
bunch of aligned teeth, it does imply some changes in taxonomy that can be
had just by having experts disagree with experts.

  Wu W.-y., Meng J., Ye J., and Ni X.-j. 2005. *Propalaeocastor*
(Rodentia,
   Mammalia) from the Early Oligocene or Burqin Basin, Xinjiang. _American
   Museum Novitates_ 3461: 16 pages.

Abstract:
  "A new species of castorids, *Propalaeocastor irtyshensis,* n.sp., from
the Burqin Basin of Xinjiang Uygur Autonomous Region, China, is described.
The new species, represented by a right maxilla with well-preserved P4-M3,
is the earliest and northernmost occurrence of castorids in China. It is
characterized mainly by the cheek tooth crown being higher than that of
*P. butselensis* but lower than that of *Steneofiber* aff. *dehmi*
(probably a new species of *Propalaeocastor*), and by lingual confluence
of the mesoflexus to the lingual fossette of the premesoflexus. Comparison
with known species previously assigned to *Steneofiber* from Europe and
Kazakhstan leads to the conclusion that the early Oligocene forms
previously assigned to the genus, such as "*S. butselensis*" and "*S.
kazachstanicus*", differ significantly from those represented by S. eseri
from the Late Oligocene and Early Miocene of Europe. We consider
*Propalaeocastor* a valid genus, provide an emended diagnosis for it, and
discuss its evolutionary trend in relation to *Steneofiber.* Preliminary
analysis of Burqin fauna suggests an age of early Early Oligocene. Faunal
transformations across the Eocene-Oligocene boundary in the Burqin region
are comparable to those of Europe and the Mongolian Plateau and suggest
linkage of faunal turnovers and global climate changes."

  cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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