Pathways and mechanisms of Late Ordovician (Katian) faunal migrations of Laurentia and Baltica

Abstract

Late Ordovician strata within the Cincinnati Basin record a mass faunal migration event during the C4 and C5 depositional sequences. The geographic source region for the invaders and the paleoceanographic conditions that facilitated dispersal into the Cincinnati Basin has previously been poorly understood. Using Parsimony Analysis of Endemicity, biogeographic relationships among Laurentian and Baltic basins were analyzed for each of the C1-C5 depositional sequences to identify dispersal paths. The results support multiple dispersal pathways, including three separate dispersal events between Baltica and Laurentia. Within Laurentia, results support dispersal pathways between areas north of the Transcontinental Arch into the western Midcontinent, between the Upper Mississippi Valley into the Cincinnati Basin, and between the peri-cratonic Scoto-Appalachian Basin and the Cincinnati Basin. These results support the hypothesis that invasive taxa entered the Cincinnati Basin via multiple dispersal pathways and that the equatorial Iapetus current facilitated dispersal of organisms from Baltica to Laurentia. Within Laurentia, surface currents and large storms moving from northeast to southwest likely influenced the dispersal of organisms. Larval states were characterized for the Richmondian invaders, and most invaders were found to have had planktotrophic planktic larvae. These self-feeding larvae have high dispersal potential, which -in conjunction with oceanographic and climatic conditions -enabled long-distance dispersal and interbasinal species migrations.

Dispersal in the Ordovician: Speciation patterns and paleobiogeographic analyses of brachiopods and trilobites

“…Significant events of faunal immigration into epicontinental basins occurred during the Late Ordovician. For example, the Katian Richmondian Invasion involved the migration of over 60 extra-basinal genera into the Cincinnati basin from other areas within Laurentia and Baltica (Wright and Stigall, 2013a;Bauer and Stigall, 2014;Lam and Stigall, 2015), which resulted in significant ecosystem restructuring Holland, 2008;Stigall, 2010). Even more widespread migration of taxa occurred with the establishment of the Hirnantian fauna during the latest Ordovician.…”

“…C, Cincinnati basin; A, Southern Appalachian basin; P, Northern Appalachian basin. Paleogeographic map modified after Lam and Stigall (2015) and Kolata et al (2001).…”

“…Similarly, studies examining dispersal of planula (self-feeding) larvae of tropical Pacific scleractinian coral species identified dispersal of 50 to 150 km in a single generation before settlement (Treml et al, 2008). In addition, Lam and Stigall (2015) found that the majority of invasive taxa into the…”

Estimating dispersal and evolutionary dynamics in diploporan blastozoans (Echinodermata) across the great Ordovician biodiversification event

“…To date there are no models that have captured surface water flow within the Laurentian epicontinental seas, but based on reconstructed wind vectors, surface currents likely flowed from the northeast to southwest (Ettensohn 2010), with major hurricanes sweeping across the paleocontinent from 10°to 30°north and south of the equator (Jin et al 2013). As concluded in other studies that have focused on intracratonic Laurentian dispersal events of marine invertebrates (Wright and Stigall 2013;Bauer and Stigall 2014;Lam and Stigall 2015;Lam et al 2018), we assume these mechanisms were the primary drivers of dispersal among basins. The lack of tectonic and thermal barriers that later resulted from the Taconian orogeny (e.g., the Sebree Trough) in the Early Ordovician, combined with strong wind and storm activity, likely led to increased blastozoan dispersal events among areas and decreased endemism during this time.…”

Comparisons of Late Ordovician ecosystem dynamics before and after the Richmondian invasion reveal consequences of invasive species in benthic marine paleocommunities

“…Nonnative species occupied a variety of trophic levels and included tabulate and rugosan corals, trilobites, gastropods, bivalves, brachiopods, and nautiloids (Foerste 1917; Holland and Patzkowsky 2007; Stigall 2010). Immigrating taxa were likely transported into the basin via multiple routes within Laurentia and Baltica due to climate-related changes in ocean circulation and sea level (Patzkowsky and Holland 1996; Holland 1997; Stigall 2010; Wright and Stigall 2013; Lam and Stigall 2015; Stigall and Fine 2019). The processes that initiated the Richmondian invasion were in many ways similar to current oceanographic changes related to modern climate change.…”