Figure 1.
Late Ordovician paleogeography of Laurentia.
Biogeographic areas analyzed are: (1), Anticosti Island (2);, Appalachian Basin (3);, Cincinnati Basin (4);, Central Basin (5);, Southern Midcontinent; and (6), Northern Midcontinent. Paleogeographic reconstructions (e.g. [45]) support the separation of these areas by physical barriers, such as structural platforms, trenches, and intracratonic arches, indicated with grey lines. Primary locus of tectonic activity during the Blountian (B) and Taconic (T) tectophases are indicated along the subduction zone.
Figure 2.
Species-level evolutionary and biogeographic patterns for Glyptorthis Foerste, 1914 [28], Plaesiomys Hall and Clarke, 1892 [29], and Hebertella Hall and Clarke 1892 [29] mapped onto a stratigraphic column at the level of depositional sequence. Ghost lineages reconstructed via equal phylogenetic split. Abbreviations: Ro, Rocklandian; Ki, Kirkfieldian; G, Gamachian; H, Hirnantian. Timescale modified from Holland & Patzkowsky [6].
Figure 3.
Cladograms depicting evolutionary and biogeographic relationships for species in Glyptorthis Foerste, 1914 [28], Plaesiomys Hall and Clarke, 1892 [29], and Hebertella Hall and Clarke 1892 [29]. Phylogenetic topology from Wright & Stigall [26,27]. Geographic distributions for terminal taxa were compiled from literature sources and museum collections. Only occurrence data for which the species could be visually verified (e.g., photo plate, museum specimen examined) were incorporated. Biogeographic states for ancestral nodes were optimized using Fitch Parsimony as described in Lieberman [22].
Figure 4.
Vicariance and Geodispersal general area cladograms.
The vicariance trees indicate the order that areas became separated from each other due to barrier (tectonic, eustatic, etc.) formation; whereas geodispersal trees indicate the relative order in which barriers were removed. Congruence between tree topologies indicates that geographic barriers rose and fell in the same relative order, suggesting the importance of cyclical geologic processes (e.g., oscillating sea levels). Conversely, incongruence indicates that singular events (e.g. tectonic pulses) influenced the evolution and biogeographic differentiation of the clades [22]. Numerical values indicate bootstrap (plain text) and jackknife (italicized) support for nodes. T1 analysis recovered a single most parsimonious vicariance tree (length of 87 steps, consistency index 0.736) and two most parsimonious geodispersal trees (64 steps, CI 0.797). T2 analysis recovered a single most parsimonious vicariance tree (49 steps, CI 0.816) and two most parsimonious geodispersal trees (59 steps, CI 0.531). The strict consensus topology is illustrated for geodispersal analyses.