[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Ghosts of New Papers Past



Looks like this is shaping up to be the month for Revenge of the BANDrakes,
what with these two papers...  (Thanks to RB & CJH for some of the papers
listed here!  Oh, and see what I did there?  Pun of "mandrake," an herb with
supposed magical powers...and the plants that made the fatal screaming
noises in Harry Potter.)



Feduccia, A. 2009. A colorful Mesozoic menagerie. Trends in Ecology and
Evolution. doi: 10.1016/j.tree.2009.03.002.

     (Book review of John Long's _Feathered Dinosaurs_.)



James, F.C., and Pourtless, J.A., IV. 2009. Cladistics and the origin of
birds: a review and two new analyses. Ornithological Monographs 66:1-78. 

ABSTRACT: The hypothesis that birds are maniraptoran theropod dinosaurs (the
?BMT hypothesis?) has become widely accepted by both scientists and the
general public. Criticism has usually been dismissed, often with the comment
that no more parsimonious alternative has been presented with cladistic
methodology. Rather than taking that position, we ask here whether the
hypothesis is as overwhelmingly supported as some claim. We reanalyzed a
standard matrix of 46 taxa and 208 characters from a recent paper by Clark,
Norell, and Makovicky, and we found statistical support for the clades
Coelurosauria and Maniraptoriformes and for a clade of birds and
maniraptorans. Note, however, that because the matrix contains only birds
and theropods, it assumes that the origin of birds lies within the
Theropoda. In addition to this problem, Clark et al.?s (2002) matrix
contains problematic assumptions of homology, especially in the palate,
basipterygoid, manus, carpus, and tarsus. In an attempt to avoid these two
major problems and to evaluate the BMT hypothesis and four alternative
hypotheses in a comparative phylogenetic framework, we followed the
recommendations of Jenner, Kearney, and Rieppel by constructing and
analyzing a larger but more conservative matrix. Our matrix includes taxa
from throughout the Archosauria. When the ambiguous characters were
excluded, parsimony analyses with  bootstrapping and successive pruning
retrieved a weak clade of birds and core maniraptorans (oviraptorosaurs,
troodontids, and dromaeosaurs) that also contained the early archosaur
Longisquama and was not unambiguously associated with other theropods. When
the ambiguous characters were included but coded as unknown where
appropriate, the results were virtually identical. Kishino-Hasegawa tests
revealed no statistical difference between the hypothesis that birds were a
clade nested within the Maniraptora and the hypothesis that core clades of
Maniraptora were actually flying and flightless radiations within the clade
bracketed by Archaeopteryx and modern birds (Aves). Additional statistical
tests showed that both the ?early-archosaur? and ?crocodylomorph? hypotheses
are at least as well supported as the BMT hypothesis. These results show
that Theropoda as presently constituted may not be monophyletic and that the
verificationist approach of the BMT literature may be producing misleading
studies on the origin of birds. Further research should focus on whether
some maniraptorans belong within Aves, and whether Aves belongs within
Theropoda or is more closely related to another archosaurian taxon. At
present, uncertainties about the hypothesis that birds are maniraptoran
theropods are not receiving enough attention.




On a lighter note, it's also shaping up to be a banner year for cute little
bipedal ornithischians, what with _Tianyulong_ and now:


Barrett, P.M., and Han, F.-L. 2009. Cranial anatomy of Jeholosaurus
shangyuanensis (Dinosauria: Ornithischia) from the Early Cretaceous of
China. Zootaxa 2072:31-55.

ABSTRACT: A detailed description of the skull and mandible of the Chinese
cerapodan ornithischian dinosaur Jeholosaurus shangyuanensis (Lower
Cretaceous, Yixian Formation) is presented for the first time and this
information is used to reassess its phylogenetic position. Jeholosaurus can
be distinguished from all other cerapodans on the basis of one autapomorphy
(a row of small foramina on the nasal) and a character combination that is
unique among ornithischians. Previously undescribed specimens add
considerably to our knowledge of Jeholosaurus, providing new insights into
its anatomy and ontogeny. Revised character scores increase the resolution
of phylogenetic hypotheses and provide additional support for placement of
Jeholosaurus within Ornithopoda.




And in other news:


Bedatou, E., Melchor, R.N., and Genise, J.F. 2009. Complex palaeosol
ichnofabrics from Late Jurassic-Early Cretaceous volcaniclastic successions
of central Patagonia, Argentina. Sedimentary Geology. doi:
10.1016/j.sedgeo.2009.04.005.

ABSTRACT: Late Jurassic-Early Cretaceous volcaniclastic continental deposits
from central Patagonia, Argentina were analyzed for an integral
characterization of palaeosol ichnofabrics. These units contain complex
continental ichnofabrics that were also recorded in other late Jurassic-late
Miocene extended volcaniclastic successions from Patagonia. According to a
recently proposed method, ichnofabric, pedofabric and original bedding of
selected intervals were measured separately in order to determinate the
degree in which the deposits are affected by soil features besides the
ichnofabrics. Four recurrent ichnofabrics were recognized in studied
palaeosols: the Loloichnus, large Taenidium-Beaconites, diffuse boxwork, and
Dagnichnus ichnofabrics. The Loloichnus ichnofabric is characterized by sub
vertical Loloichnus baqueroensis and subordinate, similarly arrenged large
Taenidium barretti and Beaconites coronus. L. baqueroensis is a crayfish
dwelling structure while large T. barretti and B. coronus are assigned to
locomotion of the same organisms. Root traces are additional components of
this ichnofabric. The large Taenidium - Beaconites ichnofabric is formed by
large, irregular and curved T. barretti and B. coronus and by L.
baqueroensis in low proportion.. This ichnofabric is also assigned to
crayfish activity. The diffuse boxwork ichnofabric is characterized by a
pervasive and intricate three-dimensional boxwork of burrows; occasionally
joined to sub spherical chambers (possible Castrichnus). The diffuse boxwork
is interpreted as an earthworm burrow system and the associated chambers are
probably for aestivation. Rare and scattered discrete trace fossils in this
ichnofabric include L. baqueroensis, T. barretti and B. coronus. The
Dagnichnus ichnofabric is formed by Dagnichnus titoi, root traces and,
subordinately, Loloichnus baqueroensis, Cellicalichnus meniscatus and
tangled groups of meniscate burrows. D. titoi and C. meniscatus has been
interpreted as crayfish breeding structures and the tangled groups of
meniscate burrows are probably related to juvenile crayfishes activity. The
studied ichnofabrics were formed in weakly to moderately developed
palaeosols in lowland areas with frequent reworking of pyroclastic material
by unconfined flows. The recognized ichnofabrics show that in Patagonia, for
the Late Jurassic-Early Cretaceous times, crayfishes and earthworms were the
dominant soil organisms and, along with plants, rapidly colonized deposits
exposed subaerially. After sediment deposition and with high soil moisture
content or high water table crayfishes probably crawled in moist sediments
forming the Large Taenidium - Beaconites ichnofabric. With a better drained
soil profile or lower water tables, the Loloichnus ichnofabric, representing
the dwelling structures of adult crayfishes, overprinted the previous
ichnofabric. The diffuse boxwork ichnofabric, usually located in the
uppermost portion of palaeosols, correspond to extensive fossil earthworm
burrow systems.. The Dagnichnus ichnofabric occurs in very weakly developed
palaeosols and probably reflects the optimal palaeoenvironmental conditions
for breeding crayfish.



Fabuel-Perez, I., Redfern, J., and Hodgetts, D. 2009. Sedimentology of an
intra-montane rift-controlled fluvial dominated succession: the Upper
Triassic Oukaimeden Sandstone Formation, Central High Atlas, Morocco.
Sedimentary Geology. doi: 10.1016/j.sedgeo.2009.04.006.

ABSTRACT: Triassic successions in the High Atlas of Marrakech (Morocco)
provide excellent outcrop analogues for continental fluvial systems within
an intra-montane rift basin and allow the study of facies distribution and
controls on deposition. This paper focuses on the analysis of the Oukaimeden
Sandstone Formation (F5), a fluvial dominated formation deposited in an
active rift setting. Combination of traditional sedimentological field
analysis with modern digital data capture techniques (e.g. spectral
gamma-ray, LIDAR terrestrial scanner imaging) allows a detailed description
and interpretation of the facies. The Oukaimeden Sandstone Formation is
composed of channel sandstone bodies alternating with lenticular shaped
fluvial bar sandstones and overbank mudstone deposits. Alternating with the
fluvial facies, aeolian sandstones and alluvial fan deposits are also
observed. Changes in architectural style are used to subdivide the formation
into three members. The lower member (Lower Oukaimeden ) was deposited by an
ephemeral braided system. The middle member (Middle Oukaimeden) records a
change to perennial braided fluvial conditions in response to tectonics
combined with a change in climate towards more humid conditions. The upper
member (Upper Oukaimeden) is characterized by the return to ephemeral
conditions, which combined with the occurrence of aeolian dunes, is
interpreted to record increased aridity. The upper part of the member
exhibits tidal influence, related to the first marine incursion into the
basin. The Oukaimeden Sandstone Formation provide a well documented outcrop
example of deposition within an intra-montane setting influenced by a
combination of tectonic and climatic controls.



Basilici, G., Für dal Bó, P.F., and Bernardes Ladeira, F.S. 2009.
Climate-induced sediment-palaeosol cycles in a Late Cretaceous dry aeolian
sand sheet: Marília Formation (North-West Bauru Basin, Brazil).
Sedimentology. doi: 10.1111/j.1365-3091.2009.01061.x.

ABSTRACT: Aeolian sand sheets, which are characterized by low relief
surfaces that lack dunes, are common in arid and semi-arid climatic
settings. The surface of an aeolian sand sheet can either be stable and
subject to pedogenetic effects, or unstable such that it is affected by
deflation or sedimentation. The Marília Formation (Late Cretaceous) may be
interpreted as an ancient aeolian sand sheet area, where alternating phases
of stability and instability of the accumulation surface have been recorded.
Detailed field studies were carried out in several sections of the Marília
Formation, where cyclic alternations of palaeosols and aeolian deposits were
evident, using palaeopedological and facies analysis methods, supported in
the laboratory by the analysis of rock samples, cut and polished in slabs,
thin sections, scanning electron microscope images and X-ray diffraction
data from the clay minerals. The deposits comprise three lithofacies that,
in order of abundance, are characterized by: (i) translatent wind-ripple
strata; (ii) flood deposits; and (iii) ephemeral river channel deposits.
Palaeosols constitute, on average, 65% of the vertical succession. Three
types of palaeosols (pedotypes) are recognized: (i) Aridisols; (ii)
Entisols; and (iii) Vertisols. Erosional surfaces due to aeolian deflation
divide the top of the palaeosol profiles from the overlying aeolian
deposits. The palaeoenvironmental interpretation of the deposits and the
palaeosols allows the depositional system of the Marília Formation to be
defined as a flat area, dominated by aeolian sedimentation, with subordinate
ephemeral river sedimentation, and characterized by a dry climatic setting
with occasional rainfall. The climate is the main forcing factor controlling
the alternation between episodes of active sedimentation and periods of
palaeosol development. A climate-controlled model is proposed in which: (i)
the palaeosols are indicative of a stable surface that is developed during
the more humid climatic phases; and (ii) the erosional surfaces and the
overlying aeolian sediments attest to periods of deflation and subsequent
sedimentation, thereby increasing the availability of sediment during the
drier climatic phases. The ephemeral fluvial deposits mark the more humid
climatic conditions and contribute to the lagged sediment influx caused
during the drier periods by the erosion of previously stored sediment.



Maxwell, E.E. 2009. Comparative ossification and development of the skull in
palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the
Linnean Society 156(1):184-200. doi: 10.1111/j.1096-3642.2009.00480.x.

ABSTRACT: Ratites and tinamous are a morphologically diverse group of
flightless and weakly flighted birds. As one of the most basal clades of
extant birds, they are frequently used as an outgroup for studies discussing
character evolution within other avian orders. Their skeletal development is
not well known in spite of their important phylogenetic position, and
studies have historically been plagued with small sample sizes and limited
anatomical and temporal scope. Here, I describe the ossification of the
skull in the emu (Dromaius novaehollandiae), ostrich (Struthio camelus),
greater rhea (Rhea americana), and elegant crested-tinamou (Eudromia
elegans). Skeletal development is remarkably consistent within palaeognaths,
in spite of large differences in absolute size and incubation period. Adult
morphology appears to play a role in interordinal differences in the
sequence and timing of ossification of certain bones. Neither the timing of
cranial ossification events relative to stage nor the sequence of
ossification events provides any evidence in support of a paedomorphic
origin of the palaeognathous palate. This study provides an important first
look at the timing and sequence of skull development in palaeognathous
birds, providing data that can be compared to better-studied avian systems
in order to polarize ontogenetic characters.



Delfino, M., and Smith, T. 2009. A reassessment of the morphology and
taxonomic status of 'Crocodylus' depressifrons Blainville, 1855 (Crocodylia,
Crocodyloidea) based on the Early Eocene remains from Belgium. Zoological
Journal of the Linnean Society 156(1):140-167. doi:
10.1111/j.1096-3642.2009.00478.x.

ABSTRACT: The name Crocodilus depressifrons appears in the literature as the
caption of a table, published by Blainville in 1855, depicting crocodylian
remains from France. Although a proper diagnosis and description have never
been published, this species has been frequently used to identify some
European Eocene crocodyloids with a generalized, not elongated, rostrum. In
the last 50 years, C. depressifrons has been often referred to the genus
Asiatosuchus. This genus, erected by Mook in 1940 on the basis of fossil
remains from the Middle Eocene of Mongolia, actually contains a rich and
apparently nonmonophyletic assemblage of Palaeogene crocodyloids. In order
to help clarify the morphology and the relationships of the
Asiatosuchus-like taxa, it is here described a rich collection of
crocodyloid remains, including skulls and a nearly complete skeleton, from
four different Early Eocene localities of the Belgian Tienen Formation:
Dormaal, Erquelinnes, Leval, and Orp-le-Grand. All these remains belong to
one single taxon which clearly represents the long known but never properly
described 'C.'depressifrons. They allow, for the first time, the diagnosis
this species on the basis of an unequivocal set of characters, contributing
to the long awaited revision of the Asiatosuchus-like taxa.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
 and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"It's no wonder that truth is stranger
than fiction. Fiction has to make
sense."
                          -- Mark Twain