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Product: 075 Silurian and Lower Devonian thelodonts and putative chondrichthyans from the Canadian Arctic Archipelago


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Special papers in Plaeaeontology 75.
<br />
<br />Silurian and Lower Devonian thelodonts and putative chondrichthyans from the Canadian Arctic Archipelago.
<br />
<br />T. Marss, M.V.H. Wilson and R. Thorsteinsson.
<br />
<br />143pp., 29pls
<br />
<br />ABSTRACT: Thelodonts and putative chondrichthyans from
<br />rocks of upper Llandovery (Lower Silurian) to Lochkovian
<br />(Lower Devonian): mainly from Baillie-Hamilton and Cornwallis islands, Arctic Canada, are treated according to taxonomic content, spatio-temporal distribution, and possible
<br />significance for recognition of geological event levels. The systematics of numerous groups of thelodonts can, for the first time, be based on both articulated specimens and isolated scales. Some 39 thelodont species ( 12 of them preserved as
<br />articulated squamations) belonging to 25 genera, 16 families, and five orders, together with two putative chondrichthyan taxa (both represented by articulated squamations) are treated.
<br />
<br />The thelodont order Loganelliiformes Turner, contains herein the family Loganelliidae
<br />Karatajuté-Talimaa, with the genera Loganellia Turner, represented by L. scotica (Traquair), L. sulcata Mârss et al., L. prolata Mârss et al., L. grossi
<br />Fredholm, and L. exilis Mârss et al., and Illoganellia Mârss
<br />et al., including f. colossea Màrss et al., and the family
<br />Nunavutiidae Mârss et al., with the genus Nunavutia Marss
<br />et al., comprising N. fasciata Màrss et al.
<br />
<br />The order Shieliiformes Mârss et al. includes the family Shieliidae Mârss et al., with the genus Shielia Marss, represented
<br />by S. parca Mârss et al. and S. gibba Mârss et al., along with
<br />the genus Paralogania Karatajuté-Talimaa, incorporating
<br />P. martinssoni (Gross) and P. readbayensis Marss et al.
<br />The order Phlebolepidiformes Berg comprises the family
<br />Phlebolepididae Berg, with the genus Erepsilepis Màrss et al.
<br />with its species E. margaritifera Mârss et al.., and the family
<br />Katoporodidae Màrss et al., with the genera Katoporodus
<br />Turner and Peel, represented by K. tricavus (Gross), K serratus Màrss et al., and K. gemellus Mârss et al., Overia Soehn
<br />et al., containing O. adraini Soehn et al., and Goniporus
<br />Gross, characterized by G. alatus (Gross).
<br />
<br />The order Thelodontiformes Kiaer includes the family Coelolepididae Pander, with the genus Tbelodus Agassiz, represented by T. inauditus Mârss et al. and Thelodus? sp. indet. The family Lanarkiidae Obruchev contains the genera Lanarkia Traquair, exemplified by L. horrida Traquair and Lanarkia? sp.,
<br />and Phillipsilepis Mârss et al., characterized by P. crassa Màrss
<br />et al., P cornuta Màrss et al., and P pusilla Mtirss et al. The
<br />family Archipelepididae Màrss, in Soehn et al., has one genus,
<br />Archipelepis Mârss (in Soehn et al.), with one species, A. bifurcata Marss et al. The family Boothialepididae Màrss contains
<br />the genus Boothialepis Mârss, represented by B. thorsteinssoni
<br />Mârss. The family Turiniidae Obruchev comprises the genus
<br />Turinia Traquair with the species T. polita Karatajuté-Talimaa.
<br />The family Nikoliviidae Karatajuté-Talimaa includes the genera
<br />Nikolivia Karatajuté-Talimaa, represented by N. gutta Karatajuté-Talimaa and N. auriculata Màrss et al., and Chattertonodus Mârss et al., represented by C cometoides Màrss et al.
<br />
<br />The family Talivaliidae Mârss et al. embraces the genera Talivalia
<br />Màrss et al., represented by T. elongata ( Karatajuté-Talimaa):
<br />and Glacialepis Màrss et al. with G. corpulenta Marss et al.
<br />Questionably assigned to the order Thelodontiformes is the
<br />family Eestilepididae Marss et al., with one genus, Eestilepis
<br />Mârss et al., represented by F. prominens Màrss et al.
<br />The order Furcacaudiformes Wilson and Caldwell, occurs in
<br />the sections studied as the family Furcacaudidae Wilson and
<br />Caldwell, with the genus Canonia Vieth comprising three species: C. grossi Vieth, C. costulata Marss et al. and Canonia? sp.
<br />
<br />Questionably assigned to the order Furcacaudiformes is
<br />the family Barlowodidae Màrss et al., with the genera
<br />Barlowodus Màrss et al., containing B. excelsus Mârss et al.,
<br />B. floralis Mârss et al., and B. tridens Marss et al., and Sophialepis Mârss et al., represented by S. ancorata Màrss et al.
<br />Taxa of putative chondrichthyans of uncertain ordinal position comprise the family Kannathalepididae Marss and Gagnier, with the genus Frigorilepis Màrss et al., including F. caldwelli Màrss et al. , along with the family Wellingtonellidae Màrss et al., with the genus Wellingtonella Marss et al.,
<br />represented by W. gagnieri Màrss et al.
<br />
<br />Both taxonomic and morphological diversity of thelodonts
<br />is much greater than previously known; new anatomical
<br />information will allow greater precision in future phylogenetic
<br />studies of thelodonts and related vertebrates. Biostratigraphic
<br />distribution of taxa allows improved correlation of strata
<br />between Europe, the Canadian Arctic islands, and the Mackenzie Mountains, and greater precision in identification of
<br />the Llandovery/Wenlock boundary and the associated
<br />carbon-isotope excursion event.