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Still More New Papers



Jeez, finding non-boring subject lines for these messages is a pain in the patookus...

Another from the Early Sauropodomorph volume:

Fedak, T.J., and Galton, P.M. 2007. New information on the braincase and skull of Anchisaurus polyzelus (Lower Jurassic, Connecticut, USA; Saurischia: Sauropodomorpha): implications for sauropodomorph systematics; pp. 245-260 in Barrett, P.M. and Batten, D.J. (eds.), Evolution and Palaeobiology of Early Sauropodomorph Dinosaurs. Special Papers in Palaeontology 77. Palaeontological Association, London.

ABSTRACT: A skull of Anchisaurus polyzelus (YPM 1883) has been misinterpreted for over 120 years as a result of deformation during preservation and loss of a small piece of the skull block shortly after collection in 1884. The only other skull of this taxon (YPM 209), from a smaller individual, has been largely ignored in previous studies owing to distortion and incomplete preparation. Additional preparation of the latter specimen has exposed several new elements, including the nearly complete parabasisphenoid, a region that is damaged and incomplete in YPM 1883. Based on this new information, a phylogenetic analysis supports the recent hypothesis that Anchisaurus was a basal sauropod. However, the strength of this hypothesis has been greatly reduced, and is also undermined further by the possibility that the specimens of Anchisaurus are skeletally immature. In general, the skull and braincase of Anchisaurus resembles those of 'prosauropods' more closely than those of derived sauropods.


Also:

Phillips, P.L., Jr., Ludvigson, G.A., Joeckel, R.M., González, L.A., Brenner, R.L., and Witzke, B.J. 2007. Sequence stratigraphic controls on synsedimentary cementation and preservation of dinosaur tracks: Example from the lower Cretaceous, (Upper Albian) Dakota Formation, Southeastern Nebraska, U.S.A. Palaeogeography, Palaeoclimatology, Palaeoecology 246(2-4):367-389. doi: 10.1016/j.palaeo.2006.10.013.

ABSTRACT: A thin cemented sandstone bed in the Upper Albian Dakota Formation of southeastern Nebraska contains the first dinosaur tracks to be described from the state. Of equal importance to the tracks are stable-isotope (C, O) analyses of cements in the track bed, especially in the context of data derived from generally correlative strata (sandstones and sphaerosiderite-bearing paleosols) in the region. These data provide the framework for interpretations of paleoenvironmental conditions, as well as a novel approach to understanding mechanisms of terrestrial vertebrate track preservation.
High minus-cement-porosity (> 47%) and low grain-to-grain contacts (2.5) in the track bed indicate early (pre-compaction) lithification. Although phreatic cements dominate, the history of cementation within this stratigraphic interval is complex. Cathodoluminescence petrography reveals two distinct calcite zones in the track-bearing horizon and four cement zones in stratigraphically equivalent strata from a nearby section. The earliest calcite cements from both localities are likely coeval because they exhibit identical positive covariant trends (d18O values of - 9.89 to - 6.32? and d13C values of - 28.01 to - 19.33? VPDB) and record mixing of brackish and meteoric groundwaters. All other calcite cements define meteoric calcite lines with d18O values clustering around - 9.42? and - 8.21? VPDB from the track-bearing horizon, and - 7.74?, - 5.81?, and - 3.95? VPDB from the neighboring section. Distinct meteoric sphaerosiderite lines from roughly correlative paleosols serve as a proxy for locally recharged groundwaters. Back-calculated paleogroundwater d18O estimates from paleosol sphaerosiderites range from - 7.4 to - 4.2? SMOW; whereas, meteoric calcite lines from the track horizon are generally more depleted.
Differences in cement d18O values record changes in paleogroundwater recharge areas over time. Early calcite cements indicate mixing of fresh and brackish groundwaters during the syndepositional lithification of the track horizon. Later calcite cements, however, indicate recharge from a larger catchment basin that extended far inland. Therefore, the cements likely record a rise and subsequent fall in relative sea level. We conclude that scrutiny of the cement isotope geochemistry of genetically significant surfaces, especially track beds, can provide new data for interpreting sea level change.



A slew from the newest _Acta Palaeontologica Polonica_:

Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52(1):1-16.

ABSTRACT: Misleading interpretations of "gastroliths" in fossil taxa have complicated the use of this term in palaeontology. This paper reviews the definitions and ascribed functions of gastroliths. According to the suggested definition, gastroliths are hard objects within the digestive tract of animals-without specification of the mechanisms that are responsible for their accumulation. To further improve definitions, the origin-based terms "bio-gastrolith", "patho-gastrolith", and "geo-gastrolith" are introduced. The term "exolith" is introduced for isolated clasts with a possible history as geo-gastroliths. Hypotheses about the function of stomach stones in fossil and extant taxa are reviewed, discussed and supplemented with new research. Trituration and mixing of foodstuff are the generally accepted functions of gastroliths in many vertebrates, including birds. In contrast, ballast provided by swallowed stones is considered to be of limited importance for buoyancy in aquatic animals. Other functional hypotheses include mineral supply and storage, stomach cleaning, maintenance of a beneficial microbial gut flora, destruction of parasites and alleviation of hunger. Accidental ingestion of sediment, either by being mistaken for prey, by being attached to it, during playing or due to pathological behaviour, is considered to be common. Different functions may overlap in various taxa.


Fanti, F., and Therrien, F. 2007. Theropod tooth assemblages from the Late Cretaceous Maevarano Formation and the possible presence of dromaeosaurids in Madagascar. Acta Palaeontologica Polonica 52(1):155-166.


ABSTRACT: The latest Cretaceous (Campanian?-Maastrichtian) Maevarano Formation of the Mahajanga Basin, Madagascar, preserves one of the most diverse fossil vertebrate faunas of the Gondwanan landmasses. Over 180 isolated theropod teeth recovered from that formation were studied in order to document theropod diversity in the Madagascar insular setting. Tooth morphology and characteristics of the Maevarano teeth were compared to those of known theropod teeth for identification, including the Malagasy non-avian theropods Majungatholus atopus and Masiakasaurus knopfleri. Tooth and denticle morphologies permit the recognition of five tooth morphotypes: three morphotypes are referable to Majungatholus atopus based on variation in tooth morphology observed in teeth preserved in situ in the jaws of two specimens, and one morphotype is ascribable to Masiakasaurus knopfleri. Teeth pertaining to the fifth morphotype differ from other morphotypes in the size and orientation of the denticles, shape and orientation of blood grooves, and in general tooth morphology. Statistical analyses reveal that the fifth Maevarano tooth morphotype is similar to dromaeosaurid teeth, suggesting that a yet unknown theropod taxon inhabited Madagascar during the latest Cretaceous. This morphotype represents the first evidence of the possible presence of a dromaeosaurid in Madagascar and supports the theory that dromaeosaurids were present throughout Pangaea before the break-up of the supercontinent during the Late Jurassic and had colonized Madagascar before its separation from Africa during the Early Cretaceous.



Schwarz, D., Frey, E., and Meyer, C.A. 2007. Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods. Acta Palaeontologica Polonica 52(1):167-188.

ABSTRACT: The axial soft-tissue system in the neck of Dicraeosauridae and Diplodocidae, including pneumatic diverticula, ligaments, and muscles, is reconstructed on the basis of phylogenetic and functional morphological comparisons with extant crocodylians and birds and compared with other soft-tissue reconstructions for sauropods. Bifurcation of the neural spines separated the paired supraspinal ligament into two sheets. A paired interspinal septum was attached to the cranial and caudal margins of the neural spines. The dorsal and the lateral portions of the cervical musculature must have been strongly segmented, whereas the laterocostal portion was divided with one myoseptum per vertebral segment. The hypaxial cervical muscle was most probably small and only poorly segmented. In Diplodocidae and Dicraeosauridae, the distribution of external pneumatic structures is similar, whereas only Diplodocidae possess intraosseous pneumatic structures. Supravertebral pneumatic diverticula are reconstructed for both groups, which, together with dorsal ligaments filled the gap between the metapophyses of bifurcate neural spines. Comparisons between the vertebrae of juvenile and adult diplodocids strongly indicate that pneumatisation proceeded from the supramedullary diverticula into the neural arch and the neural spine. The regular branching pattern of the pneumatic cavities as well as the vertical I-beam construction of the vertebral corpora is interpreted as a consequence of the biomechanical constraints of the vertebral corpora in diplodocids. These reconstructions form the ground for functional morphological considerations in Diplodocidae and Dicraeosauridae while addressing the possible mechanical consequences of pneumatic structures for the integrity of the support system of the neck.


And lastly:

Lü, J., Liu, J., Wang, X., Gao, C., Meng, Q., and Ji, Q. 2006. New material of pterosaur Sinopterus (Reptilia: Pterosauria) from the Early Cretaceous Jiufotang Formation, western Liaoning, China. Acta Geologica Sinica (English Edition) 80(6):783-789.

ABSTRACT: Based on a new nearly complete postcranial skeleton of an adult specimen of Sinopterus from the Early Cretaceous Jiufotang Formation of western Liaoning, China, the diagnosis of Sinopterus is amended. The revised diagnosis of Sinopterus includes skull relatively elongate with weakly developed cranial crest; ratio of the length of Ph2d4 to that of Ph1d4 is approximately 0.73; ratio of the length of wing metacarpal to that of metatarsal 3 is 4.5; ratio of the length of mt3 to that of tibia is approximately 0.21, and wing phalanges 1 and 2 are straight. Comparison between the ratios of the limb bones between non-adult and adult individuals of Sinopterus indicates that during the ontogenetic process,some ratios between bones are constant, such as the first wing phalanx to the second wing phalanx, the wing metacarpal to the metatarsal 3, metatarsal 3 to the tibia, but others are not, such as humerus to wing metacarpal and femur to tibia, in which the former grows faster than the latter.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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/

"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and humans
is like trying to decipher Demotic Egyptian with
the help of an odometer and the Oxford
English Dictionary."
-- D. Graur & W. Martin (_Trends
in Genetics_ 20[2], 2004)