Redescription of the gnathostome fish fauna from the mid-Palaeozoic Silverband Formation, the Grampians, Victoria

Gnathostome vertebrate remains from fine-grained sandstones of the Silverband Formation in the Grampians, Victoria include dissociated fin spines, scales and teeth. These elements arc assigned herein to the acanthodians Sinacanthus? micracanthus (fin spines) and Radioporacanthodes sp. cf. R. qujingensis (scales and tooth whorls). This fauna indicates a Late Silurian (?late Ludlow) age for the vertebrate-beating Stratum. Under current systematic groupings, the two gnathostome taxa from the Silverband Formation belong to two different families, the Sinacanthidae and the Poracanthodidae. However. the preserved association could indicate that the three element types derived from the same biological species. The possibility that the Sinacanthidae is a sister group to the Climatiidae and the Poracanthodidae is raised by this scenario. The Sinacanthidae is tentatively reassigned to the Acanthodii, as it is considered to lack diagnostic chondrichthyan characters.

A redescription of Atopacanthus dentatus Hussakof and Bryant, 1918 (Acanthodii, Ischnacanthidae)

The holotype specimen of the ischnacanthid acanthodian Alopacanthus dentatus comprises most of the posterior half of a dentigerous jaw bone, rather than a fragment from the middle of the jaw as was previously believed. A new diagnosis and revised description for the taxon are based on the holotype from the Rhinestreet Shale (Frasnian) and other specimens front the North Evans and Genundewa limestones (early Frasnian) of the Genesee Formation (late Givetian-early Frasnian); all of: these dentigerous jaw bones were collected near Hamburg, New York state, U.S.A. An emended diagnosis for Atopacanthus clarifies the differences between it and other ischnacanthid genera.

A preliminary phylogenetic analysis of the Capsalidae (Platyhelminthes : Monogenea : Monopisthocotylea) inferred from large subunit rDNA sequences

Phylogenetic relationships within the Capsalidae (Monogenea) were examined Using large subunit ribosomal DNA sequences from 17 capsalid species (representing 7 genera, 5 subfamilies), 2 outgroup taxa (Monocotylidae) plus Udonella caligorum (Udonellidae). Trees were constructed using maximum likelihood, minimum evolution and maximum parsimony algorithms. An initial tree, generated from sequences 315 bases long, Suggests that Capsalinae, Encotyllabinae, Entobdellinae and Trochopodinae are monophyletic, but that Benedeniinae is paraphyletic. Analyses indicate that Neobenedenia, currently in the Benedeniinae, should perhaps be placed in 2 separate subfamily. An additional analysis was made which omitted 3 capsalid taxa (for which only short sequences were available) and all outgroup taxa because of alignment difficulties. Sequence length increased to 693 bases and good branch support was achieved. The Benedeniinae was again paraphyletic. Higher-level classification of the Capsalidae, evolution of the Entobdellinae and issues of species identity in Neobenedenia are discussed.