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New Papers on 34th Street

Oooooo, holiday movies...! Thanks to Denver Fowler, Lee Garrison, and Jay Nair for bringing some of these to my attention!

Burnham, D.A. 2007. Archaeopteryx -- a re-evaluation suggesting an arboreal habitat and an intermediate stage in trees down origin of flight. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 245(1):33-44.

ABSTRACT: The fossil-Iagerstätte of the Upper Jurassic Solnhofen Formation contains the earliest known specimens of Archaeopteryx. The paleoecology that was indigenous for these archaeopterygian birds is not well known. The marine Solnhofen Formation also included other such terrestrial fliers as pterosaurs and insects. These volant (i. e., able to fly) taxa along with continental plant material were likely blown over the marine waters by storms some distance from their natural habitat. These terrestrial organisms could only have originated from nearby landmasses with freshwater that supported a open forests of conifers and other gymnosperms. This habitat was ideal for the skeletal adaptations seen in Archaeopteryx in which its' climbing ability far outweighed its putative cursorial attributes. Moreover, these archaeopterygian birds were constructed primitively compared to flapping flight mechanisms of Recent birds, further suggesting arboreal features in archaeopterygian birds were indicative of their lifestyle. With a primitive wing beat, Archaeopteryx represents an intermediate form between gliders and flapping fliers.

There are some other papers of interest in the same volume (the proceedings of the 4th Symposium on Lithographic Limestone & Plattenkalke -- see http://www.ingentaconnect.com/content/schweiz/njbgeol/2007/00000245/00000001), including one on the pterosaur _Ctenochasma_, but I don't have any of them yet.

Ferrusquia-Villafranca, I., Bravo-Cuevas, V.M., and Jiménez-Hidalgo, E. 2007. Xochixtlapilco dinosaur ichnofauna, Middle Jurassic of Oaxaca, southeastern Mexico: description and paleontologic significance. Contributions in Science of the Natural History Museum of Los Angeles County 515:1-40.

ABSTRACT: The Xochixtlapilco Dinosaur Ichnofauna was recovered from fine-grained, red phyllarenitic strata of the Middle Jurassic Tecocoyunca Group partim, which was laid down in a coastal lagoon, and dated as Early Bajocian-Early Bathonian on the basis of ammonites. The site lies in the Oaxacan Mixteca, southeastern Mexico. The ichnofauna chiefly consists of small footprints, whose makers are referred to as a ''basal coelurosaur'' (Morphotype A tracks); an undescribed sauropod taxon, probably of family rank (Morphotype C tracks); and an ankylopollexian ornithopod (Morphotype D tracks). There is also a single large footprint made by an ?allosaurid carnosaur (Morphotype B track). This small but relatively diverse ichnofauna is the southernmost record of Jurassic dinosaurs in North America, and adds a new fauna to the meager record of dinosaurs in Middle America.
During the Jurassic the Mixteca territory (~Mixteca Terrane) was one of several small continental crust blocks laid down in the inter-American/African space, as Pangea became disassembled. Ecologically such a scenario corresponded to an isolated setting where limited space and resources might have induced selective pressures toward small size, especially to the primary consumers and associated predators; it also shielded the island fauna from competition and exchange with neighboring continental faunas. Nonetheless, the Xochixtlapilco dinosaur fauna shows a closer biogeographic/phylogenetic resemblance to the North American faunas than to the South American or African faunas; however, the meaning of this fact can not be fully ascertained at present because of the Xochixtlapilco fauna's small size.

This one is available free at http://www.nhm.org/research/publications/index.html#pdf.

Elliott, W.S., Jr., Suttner, L.J., and Pratt, L.M. 2007. Tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin, Cloverly and Lakota Formations (Lower Cretaceous) of Wyoming, U.S.A. Sedimentary Geology 202(4):730-753. doi: 10.1016/j.sedgeo.2007.09.001.

ABSTRACT: Continental sediments of the Cloverly and Lakota Formations (Lower Cretaceous) in Wyoming are subdivided into three depositional systems: perennial to intermittent alluvial, intermittent to ephemeral alluvial, and playa. Chert-bearing sandstones, conglomerates, carbonaceous mudrocks, blocky mudrocks, and skeletal limestones were deposited by perennial to intermittent alluvial systems. Carbonaceous mudrocks contain abundant wood fragments, cuticle and cortical debris, and other vascular plant remains representing deposition in oxbow lakes, abandoned channels, and on floodplains under humid to seasonal conditions. Intraformational conglomerates, sandstones, bioturbated and blocky mudrocks with caliche nodules, and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems. Bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo-slickensides. The presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi-arid conditions. Caliche nodules, pseudo-slickensides, and carbonate-rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi-arid climatic conditions. Laminated mudrocks, siltstones, vuggy carbonates, bedded to nodular evaporites, pebbly mudrocks, and diamictites were deposited in evaporative alkaline lakes or playas. Pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa, resulting from intense rain events within the basin.

The areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the Early Cretaceous Cordilleran foreland basin in Wyoming. The lower part (A-interval) of the Cloverly and Lakota Formations is characterized by deposits of perennial to intermittent rivers that existed 300 to 1000 km east of the Sevier fold-and-thrust belt. Proximal to the Sevier fold-and-thrust belt, the A-interval of the Cloverly Formation and upper Ephraim Formation of the Gannett Group are typified by deposits of intermittent to ephemeral rivers and their associated floodplains. In the middle part (B-interval) of the Cloverly Formation, intermittent to ephemeral alluvial systems expand to 600 km into the basin. The upper part (C-interval) of the Cloverly Formation is characterized by playa deposits in the Bighorn and Wind River Basins and intermittent to ephemeral alluvial deposits along the front of the ancestral Sevier Mountains. Deposits of perennial to intermittent alluvial systems in the C-interval of the Cloverly and Lakota Formations are restricted to the Black Hills region, almost 900 km to the east of the Sevier Mountains. The change in the areal distribution of depositional systems through time within this continental foreland basin may be attributed to the development of a rain shadow associated with the uplift of the Sevier Mountains in the Early Cretaceous.

Hu, Y.-M., Meng, J., and Clark, J.M. 2007. A new Late Jurassic docodont (Mammalia) from northeastern Xinjiang, China. Vertebrata PalAsiatica 45(3):173-194.

ABSTRACT: A new genus and species of docodontid (Docodonta, Mammalia), Acuodulodon sunae, represented by a partial left lower jaw and dentition, is described. It is from the upper part of the Shishugou Formation in the Wucaiwan area of the Junggar Basin in northeastern Xinjiang, China, with an estimated age of 159~161Ma (Oxfordian, early Late Jurassic). The new mammal is typical of docodonts in having a cusp b in front of cusp a, a cusp c distolingual to cusp a and a cusp g mesiolingual to cusp a on lower molariforms. Differing from other docodonts, it has no cusp a or crest b-a developed on lower molariforms. Unique among docodonts, cusps a and c of the new animal maintained their sharpness while cusp g and crest b-g wore away fast, indicating that both shearing and crushing/grinding occurred in the chewing cycle and probably last for most of the life span of the animal. Phylogenetic analysis of a data matrix with 24 lower molariform characters across 15 taxa recovers a monophyletic Docodonta, which has distinct diagnostic characters in lower molariforms. Within docodonts, Docodon and Borealestes are successively basal to other docodonts; Acuodulodon and Itatodon + (Simpsonodon, Castorocauda+(Tegotherium + Sibirotherium)) form a monophyletic dade. Tegotheriid genera are nested within Docodontidae, but a monophyletic tegotheriid dade composed of Tegotherium, Sibirotherium, Itatodon, and Tashkumyrodon is not recovered. The dentary of Acuodulodon is typical of docodonts. It has a shallow postdentary trough and a wide and sharp medial ridge, both of which do not extend onto the medial side of the condylar peduncle, indicating looser contact between postdentary bones and the dentary than in morganucodontids, a more derived condition in the evolution toward the definitive mammalian middle ear.

Lastly -- not really new, but -- you can get for a few bucks booklets of reprints of _Scientific American_ papers on various fossil groups -- they've collected them from back issues into subject-specific booklets. There's one entitled "Prehistoric Beasts" (http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssue&ISSUEID_CHAR=68DFB6AE-A91C-4A1A-DF98AC41A3C5C4CF) and one entitled "Dinosaurs and Other Monsters" (http://www.sciam.com/special/toc.cfm?issueid=20) -- note that there are some duplicate papers between the two.

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


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