David R. Schwimmer

Functional morphology in vertebrate paleontology

1. On the inference of function from structure George V. Lauder 2. The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils Lawrence M. Witmer 3. Fossils, function and phylogeny David B. Weishampel 4. Masticatory function in nonmammalian cynodonts and early mammals A. W. Crompton 5. Correlations between craniodental morphology and feeding behavior in ungulates: reciprocal illumination between living and fossil taxa Christine M. Janis 6. Functional predictions from theoretical models of the skull and jaws in reptiles and mammals Walter S. Greaves 7. Carnassial functioning in nimravid and felid sabretooths: theoretical basis and robustness of inferences Harold N. Bryant and Anthony P. Russell 8. The artificial determination of wear patterns on tooth models as a means to infer mandibular movement during feeding in mammals Virginia L. Naples 9. Determination of stresses in mammalian dental enamel and their relevance to the interpretation of feeding behaviors in extinct taxa John M. Rensberger 10. The structural consequences of skull flattening in crocodilians Arthur S. Busbey 11. Graphical analysis of dermal skull roof patterns Keith S. Thomson 12. The forelimb of Torosaurus, and an analysis of the posture and gait of ceratopsian dinosaurs Rolf E. Johnson and John H. Ostrom 13. Functional evolution of the hindlimb and tail from basal theropods to birds Stephen M. Gatesy 14. Functional interpretation of spinal anatomy in living and fossil amniotes Emily B. Giffin 15. To what extent may the mechanical environment of a bone be inferred from its internal architecture? Jeffrey J. Thomason 16. Form vs function: the evolution of a dialectic Kevin Padian.

Scavenging by sharks of the genus Squalicorax in the Late Cretaceous of North America

Diverse sources and types of evidence indicate that common Cretaceous selachians of the genus Squalicorax were the preeminent scavengers of vertebrate carcasses during Santonian and Campanian ages of the Late Cretaceous. Evidence considered comes from the eastern Gulf Coastal Plain and Western Interior of the United States. Direct, material evidence of scavenging includes a decayed mosasaur vertebral centrum and a hadrosaurian dinosaur metatarsal, each containing a Squalicorax tooth evidently embedded after the hosts death. Abundant implicit evidence of scavenging includes Squalicorax bite marks and Squalicorax teeth associated with numerous marine tetrapod and fish remains, and at least one additional dinosaur. Many of these bite marks and tooth associations are with predaceous tetrapod taxa, well beyond the reasonable prey size of Squalicorax species. Inference of scavenging by Squalicorax is also based on comparative counts of selachian teeth in Upper Cretaceous deposits in the eastern Gulf of Mexico. Typical shark-tooth assemblages are dominated by lamnoid teeth, but at two well-studied localities containing the associated remains of large vertebrate carcasses, few shark teeth are found except those of Squalicorax, implying that these were shed during scavenging activity. Although it is not definitively proven that Squalicorax was an obligate scavenger, the longevity and cosmopolitan distribution of the genus may relate to this primary feeding strategy. INTRODUCTION

A NEW GENUS AND SPECIES OF TYRANNOSAUROID FROM THE LATE CRETACEOUS (MIDDLE CAMPANIAN) DEMOPOLIS FORMATION OF ALABAMA

Abstract The discovery of a new genus and species of tyrannosauroid from the Demopolis Formation (middle Campanian) of Alabama increases the known diversity of the clade, although it does not elucidate the place of initial dispersal. This subadult tyrannosauroid is the most complete non-avian theropod collected and described from the Cretaceous of eastern North America. In contrast to tyrannosaurids, the new taxon possesses several plesiomorphic characters, including lacrimals that lack a distinct peaked cornual process, and a dorsoventrally shallow horizontal ramus of the maxilla. Autapomorphies include a wide jugal process of the ectopterygoid, a caudal pneumatic foramen of the palatine that pierces the rostral half of the vomeropterygoid process of the bone, an articular surface for the lacrimal on the palatine that is distally positioned on the dorsolateral process, and pedal unguals that have a distinct proximodorsal lip over the articular surface. Cladistic analysis indicates the new taxon is a basal tyrannosauroid and its presence in eastern North America suggests that the recent common ancestor of Tyrannosauridae probably evolved following the transgression of the Western Interior Seaway. Cladistic analysis indicates that Dryptosaurus aquilunguis is also a basal tyrannosauroid but is less derived than the new genus.

Late Cretaceous fish from the Blufftown Formation (Campanian) in western Georgia

A Campanian fish assemblage is described from the uppermost Blufftown Formation in western Georgia. Fifteen chondrichthyan and eight osteichthyan taxa are identified, virtually all for the first time from the region. The study area represented a transitional zone between the Atlantic and eastern Gulf of Mexico Coastal Plain Provinces during the Late Cretaceous, and shows faunal relationships with both. marginal and epicontinental marine strata; the thick, de- trital sediments in the lower Chattahoochee River Valley of the Georgia-Alabama region are not exceptional in this regard. Nevertheless, the regional literature pays scant attention to Cre- taceous fish fossils. Recent work reported here has yielded an unusually diverse and abundant assemblage of cartilaginous and bony fish represented by teeth and other materials from the uppermost few meters of the Blufftown Formation, mid-to-late Campanian age, in western Georgia. Work is in progress by the authors on another regional fossil fish assemblage, that of the Eutaw Formation (locally of probable mid-Santonian age). PREVIOUS REGIONAL STUDY

The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships

We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.

Giant fossil coelacanths of the Late Cretaceous in the eastern United States

Remains of giant fossil coelacanth fish are relatively common in Upper Cretaceous strata (late Santonian to early Campanian age) in Alabama and Georgia. These are penecontemporaneous with the youngest reported fossil coelacanths from any global location and ∼135 m.y. younger than the last coelacanth fish reported from North America. A coelacanth coronoid fragment from New Jersey, apparently from the same taxon, is of latest Campanian or Maastrichtian age and is the youngest known definite coelacanth fossil. The species reconstructs to 3.5 m, which is as large as any known coelacanth. The name Megalocoelacanthus dobiei is proposed for this new coelacanth, which is also the last known member of the Glade that includes the extant Latimeria .

EXCEPTIONAL FOSSIL PRESERVATION IN THE CONASAUGA FORMATION, CAMBRIAN, NORTHWESTERN GEORGIA, USA

Abstract Mudstones and siliceous concretions in the middle Cambrian Conasauga Formation, northwestern Georgia, contain body and trace fossils showing nonmineralized preservation and represent two temporally and spatially different marine environments. Identifiable, nonbiomineralized taxa include components of a Burgess Shale–type biota with red and green algae, primitive sponges, and the arachnomorph arthropod Naraoia compacta. Also exceptionally preserved are the filamentous appendages of a large ptychopariid trilobite and assemblages of oriented hyolithid tests we interpret as priapulid coprolites and cololites. Exceptional preservation in the Conasauga Formation has multiple causes. The Conasauga contains superabundant siliceous concretions, many with skeletal, trace, and some nonbiomineralized fossils. Shale specimens, especially sponges with preserved details, and whole-body trilobite preservations, often have iron (Fe) oxide halos that resulted from a biochemical cascade including bioimmuration, decomposition gas anoxia, Fe-sulfide crystallization, and Fe oxidation. Preservation of soft tissue is also partly attributable to the well-sorted clay matrix of inner shelf Conasauga shales, which allowed mechanical imprinting of body fossils. Several nonbiomineralized fossils show algal overgrowths, suggesting an additional form of bioimmuration. Exceptional preservation in the Conasauga Formation is relatively poor compared with such better-known Cambrian Lagerstätten as the Burgess and Wheeler Shales; nevertheless, it is significant for three reasons. The siliceous concretions are a rare vehicle for exceptional preservation and feature three-dimensional fossils rather than the more common compressed specimens. The older Conasauga biota occupied a shallow-shelf environment, a setting in which exceptional preservation is poorly understood. The Conasauga Formation extends the geographic range of a Burgess Shale–type biota to the extreme southeastern USA.

Taxonomy and biostratigraphic significance of some Middle Cambrian trilobites from the Conasauga Formation in western Georgia

Biostratigraphic correlations of the Conasauga Formation in the southern Appalachians have been hindered by unreliable trilobite taxonomy. New fossil collections and re-examination of type specimens allow revision or confirmation of assignments for several Middle Cambrian trilobite taxa. These revisions reveal sufficient relationships with trilobites outside the region to place fossiliferous strata in Floyd County, Georgia, into the Oryctocephalus and Bolaspidella assemblage zones of the Middle Cambrian section defined for the Great Basin. Trilobite taxa considered are: (Agnostida) Baltagnostus centerensis (Resser, 1938) and Peronopsis cf. P. cuneifera (Barrande, 1846); (Ptychopariida) Alokistocare americanum (Walcott, 1916), Elrathia antiquata (Salter, 1859), Asaphiscus gregarius Walcott, 1916, and Glyphaspis cf. G. capella (Walcott, 1916).

Late Cretaceous dinosaurs from the Blufftown Formation in western Georgia and eastern Alabama

Fragmentary bones and teeth of three Late Cretaceous dinosaur taxa occur along both sides of the Georgia-Alabama border, in the extreme southeastern Coastal Plain Province. The localities lie in the middle and upper Blufftown Formation, in nearshore marine deposits. Exogyra ssp. and calcareous nannofossils give a late Santonian through mid-Campanian age range. Taxa determined are: Hadrosauridae, genus and species indeterminate; Ornithomimidae, genus and species indeterminate; and Albertosaurus ? sp.

Revised taxonomy, age, and geographic range of the large lamniform shark Cretodus semiplicatus

Sharks are well-known from Upper Cretaceous marine strata of the eastern Gulf of Mexico Coastal Plain (e.g., Applegate, 1970; Case and Schwimmer, 1988; Case and Schwimmer, 1992; Schwimmer et al., 1997; Case et al., 2001). This note adds the presence of Cretodus semiplicatus from two Santonian deposits in Georgia and Alabama. The occurrences reported here are noteworthy for the following reasons: the teeth are from a substantially larger selachian taxon than any so far reported in the Late Cretaceous of the eastern Gulf Coastal Plain; the specimens comprise a significant age extension of this species, as all previous reports are from Cenomanian—Turonian strata; and, finally, these rare teeth bear on the taxonomic status of C. crassidens, which is considered here a junior synonym of C. semiplicatus.