phylogenetic relationships and classification of didelphid marsupials ...

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140 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 322 foramina present on each side, exposed to lateral view on anterior orbital margin in most species, but usually concealed inside orbit in others (e.g., T. tatei). Interorbital and postorbital constrictions often distinct; supraorbital margins rounded in some species (e.g., T. pallidior), squared or beaded in others; postorbital processes usually absent or indistinct but occasionally present in old adults of some species (e.g., T. macrurus). Left and right frontals and parietals separated by persistent median sutures. Parietal and alisphenoid in contact on lateral braincase (no frontal-squamosal contact). Sagittal crest absent. Petrosal almost always exposed laterally through fenestra in parietal-squamosal suture. Parietal-mastoid contact present (interparietal does not contact squamosal). Maxillopalatine fenestrae present; palatine fenestrae present; maxillary fenestrae present in some species (e.g., T. pusillus) but absent in others (e.g., T. pallidior); posterolateral palatal foramina very large, extending anteriorly between M4 protocones; posterior palatal morphology conforms to Didelphis morphotype (with prominent lateral corners, the choanae constricted behind). Maxillary and alisphenoid not in contact on floor of orbit (separated by palatine). Transverse canal foramen present. Alisphenoid tympanic process smoothly globular, with anteromedial process enclosing extracranial course of mandibular nerve (secondary foramen ovale present), and not contacting rostral tympanic process of petrosal. Anterior limb of ectotympanic directly suspended from basicranium. Stapes triangular, with large obturator foramen. Fenestra cochleae concealed in sinus formed by rostral and caudal tympanic processes of petrosal. Paroccipital process small, rounded, adnate to petrosal. Dorsal margin of foramen magnum bordered by supraoccipital and exoccipitals, incisura occipitalis present. Two mental foramina present on lateral surface of each hemimandible; angular process acute and strongly inflected. Unworn crowns of I2–I5 symmetrically rhomboidal (‘‘premolariform’’), with subequal anterior and posterior cutting edges, increasing in length (mesiodistal dimension) from I2 to I5. Upper canine (C1) alveolus in premaxillary-maxillary suture; C1 without accessory cusps in all examined species (but see Carmignotto and Monfort, 2006). 33 First upper premolar (P1) smaller than posterior premolars but well formed and not vestigial; third upper premolar (P3) taller than P2; P3 with posterior cutting edge only; upper milk premolar (dP3) large, molariform, and nonvestigial. Molars strongly carnassialized (postmetacristae much longer than postprotocristae); relative widths usually M1 , M2 , M3 , M4; centrocrista strongly inflected labially on M1–M3; ectoflexus absent or indistinct on M1, usually present but shallow on M2, consistently deep and distinct on M3; anterolabial cingulum and preprotocrista discontinuous (anterior cingulum incomplete) on M3; postprotocrista without carnassial notch. Last upper tooth to erupt is P3. Lower incisors (i1–i4) with distinct lingual cusps. Second and third upper premolars (p2 and p3) subequal in height; lower milk premolar (dp3) trigonid usually incomplete (bicuspid). Hypoconid labially salient on m3; hypoconulid twinned with entoconid on m1– m3; entoconid much taller than hypoconulid on m1–m3. DISTRIBUTION: Species of Thylamys collectively range from north-central Peru (Ancash) southward along the Andes and Pacific coastal lowlands to central Chile; in the unforested landscapes south of Amazonia, the genus extends eastward across Bolivia (Anderson, 1997), Paraguay, and Argentina (Flores et al., 2007) to Uruguay (González et al., 2000) and eastern Brazil (Bahia, Pernambuco, and Piauí; Carmignotto and Monfort, 2006). Recorded elevations range from near sea level to at least 3800 m (Solari, 2003). REMARKS: The monophyly of Thylamys is strongly supported by parsimony, likelihood, and Bayesian analyses of IRBP (fig. 28), BRCA1 (fig. 31), vWF (fig. 32), and concatenated sequence data from five genes (fig. 33). Strong support for this clade is also 33 Although several Brazilian species of Thylamys were scored as polymorphic for presence of posterior accessory canine cusps by Carmignotto and Monfort (2006: table 4), the increasing frequencies that they observed in older age classes suggest that C1 in these taxa is notched by occlusion with p1 in their material, and that the structure in question is not homologous with the posterior accessory cusp scored from specimens with unworn dentitions by Voss and Jansa (2003: character 53).
2009 VOSS AND JANSA: DIDELPHID MARSUPIALS 141 provided by parsimony and likelihood analyses of DMP1 (fig. 29) and by parsimony and Bayesian analyses of RAG1 (fig. 30) and combined datasets that include both nonmolecular and molecular characters (figs. 35, 36). The monophyly of Thylamys is also recovered with moderate support by parsimony analysis of nonmolecular characters (fig. 27), but only one morphological trait (uniformly narrow nasals; see appendix 5) optimizes as an unambiguous generic synapomorphy. We tentatively recognize bruchi as a synonym of Thylamys pusillus following Voss et al. (in press), who explain why the former name does not belong in the synonymy of T. pallidior (contra Creighton and Gardner, 2008c), and we refer sponsorius to the synonymy of T. cinderella following Braun et al., (2005). The names pulchellus Cabrera, 1934, and fenestrae Marelli, 1932, might be synonyms of T. pusillus and T. pallidior, respectively, but we have not seen the holotypes and published information about these nominal taxa is insufficient to support any definite conclusions about them. Many other species-level issues in this genus remain problematic despite much recent taxonomic work (e.g., Palma et al., 2002; Solari, 2003; Braun et al., 2005; Carmignotto and Monfort, 2006). ACKNOWLEDGMENTS This protracted research project would have been impossible without the generosity and patience of many colleagues who loaned us irreplaceable material, tolerated numerous requests for loan extensions, and hosted our visits to their institutional collections (abbreviated as in appendix 1). Among those whose assistance in these respects we have acknowledged in previous reports, we remain especially grateful to Paula Jenkins (BMNH); Bruce Patterson and Bill Stanley (FMNH); Jim Patton and Eileen Lacey (MVZ); Mark Engstrom and Burton Lim (ROM); Phil Myers (UMMZ); and Mike Carleton, Al Gardner, and Linda Gordon (USNM). Important tissue samples contributed by Robert Baker, François Catzeflis, Guillermo D’Elía, Louise Emmons, Chris Hice, the late John Kirsch, and Maria N.F. da Silva also merit fresh acknowledgment here. Nondidelphid marsupial sequences newly reported herein were obtained from samples contributed by Steve Donnellan (SAM), Milton Gallardo (Universidad Austral de Chile), and the late Terry Yates (MSB). Mónica Díaz and Lucía Luna provided important new morphometric data for table 4. The illustrations that accompany our text are the work of two uniquely talented artists. Pat Wynne (who drew figures 1–21, 23, and 37–54) has worked on this project off and on for almost as long as we have, and is now without doubt the most accomplished illustrator of opossum morphology to be found anywhere. (Indeed, she is responsible for the discovery of several osteological characters that had escaped our notice until she drew them.) Pat worked patiently with us on multiple drafts of each figure to get the details right, and we are grateful for the skill, professionalism, and unfailing good humor that she invariably brought to this job. Fiona Reid, peerless illustrator of Neotropical rainforest mammals, likewise tolerated many nitpicking revisions of her preliminary sketches before rendering the brilliantly finished final product. We thank Michael Goulding for sending us David Schleser’s photograph of Marmosa murina (reproduced on the cover), and we thank Nature’s Images Inc. for permission to use it. As always, we are grateful to the support staff of the Department of Mammalogy for their expert assistance at every stage of this project, especially Pat Brunauer (who helped find many obscure references in our library), Neil Duncan (osteological preparator extraordinaire), and Eileen Westwig (who managed countless loans and kept the paperwork in order). Museum travel and other related expenses were supported from the department’s Taxonomic Mammalogy Fund (endowed by the late Karl F. Koopman). Lastly, RSV acknowledges the prodigious energies of his curatorial forbears at the AMNH (especially George Tate and Syd Anderson) who amassed the morphological collections on which this project was largely based. DNA sequencing work for this project began at the Monell Molecular Laboratory of the AMNH, where SAJ was supported by
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PHYLOGENETIC RELATIONSHIPS AND CLAS
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CONTENTS Abstract .................
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ABSTRACT This report summarizes a d
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