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Comparative studies of enamel and fu...

Wood, Craig Breckinridge.

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Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications./
Author:	Wood, Craig Breckinridge.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1992,
Description:	239 p.
Notes:	Source: Dissertations Abstracts International, Volume: 54-10, Section: B.
Contained By:	Dissertations Abstracts International54-10B.
Subject:	Paleontology. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9307619
ISBN:	9798643157021

Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications.
Wood, Craig Breckinridge.

Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications. - Ann Arbor : ProQuest Dissertations & Theses, 1992 - 239 p.

Source: Dissertations Abstracts International, Volume: 54-10, Section: B.

Thesis (Ph.D.)--Harvard University, 1992.

Tribosphenic molar teeth are plesiomorphic for both placental and marsupial mammals. Late Cretaceous tribosphenic mammals are known almost exclusively from dental remains. This study adds new characters for phylogenetic analysis of Cretaceous therians and their Cenozoic descendants. An SEM (scanning electronic microscope) survey of enamel structure, in molars of representative extant New World opossum genera (Didelphimorphia), reveals that Dromiciops has the most plesiomorphic pattern and Philander the most derived pattern, with intermediate Caluromys, Marmosa, and Didelphis in a sequence consistent with cladograms from other studies of comparative morphology, karyology, and serology. Contrary to previous reports, enamel indicates that, after Alphadon, Glasbius and Pediomys are the most derived Cretaceous marsupials (comparable to Dromiciops), and that stagodontids including Didelphodon vorax have the most plesiomorphic enamel yet observed in any tribosphenic molars. Enamel in stagodontids is quite similar to that in a Jurassic, "pre-tribosphenic" pantothere. Quite derived enamel in two Late Cretaceous pantotheres, Groebertherium and Mesungulatum, demonstrates potential for convergence (and mosaicism) in all therians. A more detailed documentation of enamel in stagodontids demonstrates the need for extended views of enamel, in several specimens, to be sure of patterns in relatively plesiomorphic (i.e., "non-complex") states; and also extends the hypothesis for the Family Stagodontidae as the first sister group to all other members of the marsupial clade. The hypothesis predicts that a common ancestor to placetal and marsupial mammals will have structure no more derived than that of stagodontids. Tests of Spurr's and Araldite 6005 resins show that Spurr's stands up especially well to the brighter LaB$\\sb6$ filament beam in the SEM at an operating voltage (20 KV) used for actual specimens. Because of its low viscosity (60 cps) Spurr's makes bubble-free, three dimensional casts which are excellent for teaching and research collections but which also display original surface details as small as 1 $\\mu$m wide. G.E. RTV 700 silicone rubber (with Beta 5 curing agent) is an excellent molding compound for Spurr's resin because it resists high curing temperatures and produces multiple, high-fidelity casts. Functional studies of occlusion in a new specimen of Batodon tenuis support the association of isolated upper and lower molars referred to the species by earlier workers. This rarest of tiny Cretaceous placental mammals has had controversial assignment within Eutheria. Its true relationships await further analysis, but complete M$\\sp3$, M$\\sp2$, and probably M$\\sp1$ are described here for the first time in complete series.

ISBN: 9798643157021Subjects--Topical Terms:

518862
Paleontology.
Subjects--Index Terms:

Cretaceous

Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications.
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100 1 $a Wood, Craig Breckinridge. $3 3769024
245 1 0 $a Comparative studies of enamel and functional morphology in selected mammals with tribosphenic molar teeth: Phylogenetic applications.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 1992
300 $a 239 p.
500 $a Source: Dissertations Abstracts International, Volume: 54-10, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
502 $a Thesis (Ph.D.)--Harvard University, 1992.
520 $a Tribosphenic molar teeth are plesiomorphic for both placental and marsupial mammals. Late Cretaceous tribosphenic mammals are known almost exclusively from dental remains. This study adds new characters for phylogenetic analysis of Cretaceous therians and their Cenozoic descendants. An SEM (scanning electronic microscope) survey of enamel structure, in molars of representative extant New World opossum genera (Didelphimorphia), reveals that Dromiciops has the most plesiomorphic pattern and Philander the most derived pattern, with intermediate Caluromys, Marmosa, and Didelphis in a sequence consistent with cladograms from other studies of comparative morphology, karyology, and serology. Contrary to previous reports, enamel indicates that, after Alphadon, Glasbius and Pediomys are the most derived Cretaceous marsupials (comparable to Dromiciops), and that stagodontids including Didelphodon vorax have the most plesiomorphic enamel yet observed in any tribosphenic molars. Enamel in stagodontids is quite similar to that in a Jurassic, "pre-tribosphenic" pantothere. Quite derived enamel in two Late Cretaceous pantotheres, Groebertherium and Mesungulatum, demonstrates potential for convergence (and mosaicism) in all therians. A more detailed documentation of enamel in stagodontids demonstrates the need for extended views of enamel, in several specimens, to be sure of patterns in relatively plesiomorphic (i.e., "non-complex") states; and also extends the hypothesis for the Family Stagodontidae as the first sister group to all other members of the marsupial clade. The hypothesis predicts that a common ancestor to placetal and marsupial mammals will have structure no more derived than that of stagodontids. Tests of Spurr's and Araldite 6005 resins show that Spurr's stands up especially well to the brighter LaB$\\sb6$ filament beam in the SEM at an operating voltage (20 KV) used for actual specimens. Because of its low viscosity (60 cps) Spurr's makes bubble-free, three dimensional casts which are excellent for teaching and research collections but which also display original surface details as small as 1 $\\mu$m wide. G.E. RTV 700 silicone rubber (with Beta 5 curing agent) is an excellent molding compound for Spurr's resin because it resists high curing temperatures and produces multiple, high-fidelity casts. Functional studies of occlusion in a new specimen of Batodon tenuis support the association of isolated upper and lower molars referred to the species by earlier workers. This rarest of tiny Cretaceous placental mammals has had controversial assignment within Eutheria. Its true relationships await further analysis, but complete M$\\sp3$, M$\\sp2$, and probably M$\\sp1$ are described here for the first time in complete series.
590 $a School code: 0084.
650 4 $a Paleontology. $3 518862
650 4 $a Zoology. $3 518878
653 $a Cretaceous
653 $a Didelphimorphia
653 $a marsupials
653 $a molars
690 $a 0472
690 $a 0418
710 2 $a Harvard University. $3 528741
773 0 $t Dissertations Abstracts International $g 54-10B.
790 $a 0084
791 $a Ph.D.
792 $a 1992
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9307619