What is a Pore-Canal System?

neosuchian origins and highly unusual palatal conditions, the cranial osteology of a goniopholidid has not been fully described. A well-preserved, complete skull of the North American goniopholidid Eutretauranosuchus (AMNH 570) is described. The skull was subjected to CT scans, which revealed a wellpreserved palate and braincase. As in Calsoyasuchus valliceps, Amphicotylus spp., and other specimens of Eutretauranosuchus, the secondary palate in AMNH 570 is incompletely formed, with the palatal processes of the palatines approaching but not contacting one another in the midline. As in Calsoyasuchus, the anteriormost portion of the open trough exposes the primary choana. Posteriorly the vaulted nasopharyngeal passage is exposed ventrally, as in primitive crocodyliforms (e.g. Orthosuchus). A complex septal complex divides the nasopharyngeal passage in the midline. Bilateral vomeral laminae divide the passage anteriorly. At the anterior margin of the suborbital fenestra, the vomeral laminae diverge to fit around a midline pterygoid-derived septum. Dorsoventral crushing has distorted certain braincase elements, such that the rostrum of the parabasisphenoid is somewhat dorsally displaced. However, most of the elements are preserved in anatomical position. The capitate processes of the laterosphenoid are transversely broad and the laterosphenoid bridge is angled ventromedially, resembling the condition in Gavialis. Incorporation of AMNH 570 into a phylogenetic analysis recovers the specimen in a clade of derived goniopholidids including Amphicotylus, Calsoyasuchus, Eutretauranosuchus, and Sunosuchus. Such a position is congruent with the unique palatal morphology shared among these animals.   Poster Session III (Friday, November 4) A NEW SPECIES OF THE PECCARY MACROGENIS FROM THE LATE CLARENDONIAN (LATE MIOCENE) BLACK HAWK RANCH LOCALITY, CONTRA COSTA COUNTY, CALIFORNIA PROTHERO, Donald, Occidental College, Los Angeles, CA, USA; POLLEN, Audrianna, Occidental College, Los Angeles, CA, USA Numerous nearly complete skulls and jaws in the University of California Museum of Paleontology collections from Black Hawk Ranch (near Mt. Diablo) pertain to a new species of Macrogenis, a diverse genus of late Miocene peccaries. The Black Hawk Ranch fauna, recovered from a large quarry in the Sycamore Formation, has been paleomagnetically dated as latest Clarendonian (9.0-9.5 Ma). The new species is referable to the Macrogenis-Tayassu clade, but is distinguished by its broad dentary and cheek teeth. In addition, it is distinct from other species in lacking a contact between the maxillary and the suborbital bulla, which is anteriorly narrower, and a narrow tympanic process. The prominent facial crest extends anteriorly over the rostral muscle fossa, but is not as wide and flaring as the facial-zygomatic crests of other late Miocene Macrogenis species. This taxon is one of numerous species of Macrogenis from the late Clarendonian, including an additional newspecies from Love Bone Bed in Florida, from Machaerodus Quarry in Nebraska, and Leptarctus Quarry in Nebraska. The high diversity of peccaries at this time is largely a function of their diverse array of facial-zygomatic crests in males.   Technical Session XVI (Saturday, November 5, 11:30 am) CRANIAL ANATOMY OF A PRIMITIVE OSTEICHTHYAN PSAROLEPIS BASED ON HIGH-RESOLUTION COMPUTED TOMOGRAPHY QIAO, Tuo, Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; LU, Jing, Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; ZHU, Min, Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; JOHN, A. Long, Natural History Museum of Los Angeles County, Los Angeles, CA, USA Psarolepis, from Upper Silurian and Lower Devonian strata of China and Vietnam, exhibits a unique character combination for the understanding of the origin and early evolution of osteichthyans. Together with other primitive osteichthyans (e.g., Ligulalepis, Dialipina, Achoania, Meemannia and Guiyu), Psarolepis provides a morphological link between osteichthyans and non-osteichthyan groups, and highlights a possible morphotype for the common ancestor of actinopterygians and sarcopterygians. Based on high-resolution computed tomography and three-dimensional digital reconstructions, here we present the internal morphology of the braincase of Psarolepis, and provide many informative features previously unrecognized among primitive osteichthyans. Shared with basal chondrichthyans and placoderms, Psarolepis has the forebrain cavity (housing telencephalon and diencephalon) close to the ventral floor of the neurocranium, a short prehypophysial portion of the sphenoid, and a shallow hypophyseal fossa. A pair of canals arising from the anterior extremity of the cerebral cavity and passing anterolaterally to the nasal capsule might represent separate canals for the terminal nerve, as in the placoderms Brindabellaspis and Latocamurus. Other possible plesiomorphic gnathostome features shared with many placoderms include large nasal capsules, short olfactory tracts, short and broad telencephalon, elongate mesencephalon, and an anteriorly-positioned optic nerve root. These new anatomical data will have a broad impact on osteichthyan phylogeny and character evolution, although they need to be tested within a rigorous cladistic analysis.

November 2011—PROGRAM AND ABSTRACTS

Poster Session II (Thursday, November 3) WHAT IS A PORE-CANAL SYSTEM? QU, Qingming, Subdepartment of Evolution and Development Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden; AHLBERG, Per, Subdepartment of Evolution and Development Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden; BLOM, Henning, Subdepartment of Evolution and Development Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden; ZHU, Min, Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciencesogy, Beijing, China; LI, Gang, Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Acadamy of Science, Beijing, China Traditionally, the pore-canal system is described as a structure that forms part of the socalled ‘cosmine’ characterizing early lobe-finned fishes. There are two main defining characteristics of the system: (1) it lies in the dentinous upper part of the dermal bone or scale and opens onto the outer surface; and (2) the pore-cavities are connected by horizontal ‘Maschenkanäle’. This terminology has long been confined to lobe-finned fishes, although disagreement exists for its function. Even though in many primitive actinopterygian taxa, scattered small openings have been frequently reported to exist on the surface of dermal bones and scales, they are called ‘small vascular openings’. This is partly because the covering tissues on dermal elements of actinopterygians and sarcopterygians are considered different (ganoine vs. cosmine), and also because detailed work to reconstruct the canal system in actinopterygians is missing. Here we report the 3D reconstruction of the canal system in the trunk scales of three early osteichthyan taxa: Lophosteus, Andreolepis and Psarolepis. Psarolepis is considered a basal sarcopterygian, and a true ‘pore-canal system’ exists in the scale. Comparison with the canal systems in Lophosteus and Andreolepis shows many similarities. Each of them possesses a well-developed horizontal canal-system just above the bony tissue, although in Psarolepis it is much more regular than in the other two taxa. In addition, Psarolepis has a connected, weakly developed and less regular canal system at a slightly deeper level within the bone. This thin layer may correspond to the thicker spongia layer in crown sarcopterygians, such as Porolepis. The horizontal canal system, which we argue is part of the vascularization of the scale, is most likely homologous across early osteichthyans. The use of phylogenetically restrictive but poorly defined terminology like ‘pore-canal system’ should be avoided, and focus should be placed instead on reconstructing the canal architecture in different taxa to identify phylogenetically informative characters.   Poster Session III (Friday, November 4) THE FIRST MAJOR VERTEBRATE FOSSIL FROM THE PLIOCENE OF ICELAND: AN ODONTOCETE (CETACEA: ODONTOCETI) FROM THE TJÖRNES FORMATION RACICOT, Rachel, Yale University, New Haven, CT, USA; FIELD, Daniel, Yale University, New Haven, CT, USA; VINTHER, Jakob, Yale University, New Haven, CT, USA; BEHLKE, Adam, Yale University, New Haven, CT, USA; GAUTHIER, Jacques, Yale University, New Haven, CT, USA Toothed whales (Cetacea: Odontoceti) are a disparate and species-rich group. Despite their diversity, including ranges that extend into the northernmost Atlantic Ocean, their fossil record in that region is largely enigmatic. Field exploration of the early Pliocene Tjörnes Formation in northeastern Iceland revealed the partial skull of an undescribed odontocete. The Tjörnes formation includes near-shore and terrestrial deposits that alternate with lava flows. A new age model for the outcrops was recently determined using palynological and paleomagnetic analyses, constraining the sections to 4.5-4 million years old. The fossil discovery is important both in terms of exploring the evolutionary history and biogeography of cetaceans in the North Atlantic, and the fossil record of Iceland itself. The specimen represents the northernmost occurrence of a Pliocene odontocete, bringing the fossil record into closer agreement with modern distributions. As a volcanic island, fossiliferous strata containing vertebrates are uncommon in Iceland, thus this specimen represents both a unique discovery and an opportunity to contribute to our understanding of the former biodiversity of the North Atlantic. In addition, this is the first major fossil vertebrate from the Pliocene of Iceland, and implies promise for the discovery of a more extensive fauna in the region.   Poster Session II (Thursday, November 3) STASIS IN THE LATE PLEISTOCENE GROUND SLOTHS (PARAMYLODON HARLANI) FROM RANCHO LA BREA TAR PITS, CALIFORNIA RAYMOND, Kristina, East Tennessee State University, Johnson City, TN, USA; PROTHERO, Donald, Occidental College, Los Angeles, CA, USA Stasis in Pleistocene mammals in the face of climatic change during the glacial-interglacial cycles has been widely documented. We examined the size and shape changes of the bones of common large ground sloth, Paramylodon harlani, from Rancho La Brea. We measured multiple dimensions of most of the adult unbroken astragali, patellae, and the major limb bones; only the astragali, patella, and radii were abundant in enough well dated pits for analysis. In every dimension, these bones show stasis in linear dimensions, as well as in robustness of limb elements. Statistical analysis by ANOVA confirmed that the means of all the temporally sequential samples were not significantly different from each other, so stasis prevails. These results, together with those of every common large bird or mammal from

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