Terrestrial Life in the Paleozoic: An Integrated Analysis of Body Fossils, Trace Fossils, and Biomarkers

Abstract

Paleontology is a largely umbrella term for the study of ancient life. In practice, paleontologists specialize into various subdisciplines: i.e. vertebrate or invertebrate, paleobotany, micropaleontology, ichnology, etc. This dissertation blurs these distinctions and examines the evolution and ecology of terrestrial organisms of the Carboniferous through multiple lines of evidence and across subdisciplines. By integrating the study of trace fossils, body fossils, and molecular signatures, a more holistic view of behavior, community structure, and organismal interactions in early terrestrial ecosystems is achieved. In Chapter 1, a new fossil Lagerstätte, or site of exceptional preservation, is described from the Early Pennsylvanian of Massachusetts. This site illuminates the complexity of late Paleozoic terrestrial ecosystems within the context of a rarely preserved proximal clastic environment. Exceptionally well-preserved trace fossils of vertebrates (synapsids, diadectomorphs, amniotes, temnospondyl amphibians, fish) as well as trace and body fossils of invertebrates (adult and nymphal pterygote and apterygote insects, myriapods, xiphosurans, thelyphonids, ricinuleids), along with 131 plant fossil-taxa, that includes 83 distinct foliage morphotypes, support this conclusion. Plant-insect interactions (3 functional feeding groups) preserved in the Wamsutta include the earliest currently known evidence of insect oviposition and some of the oldest documented occurrences of gall damage in the fossil record. In Chapter 2, a new species of fossil whip scorpion, (Arachnida: Uropygi: Thelyphonida) as well as the first ichnospecies (full-body impression) assignable to this group, is described from the Carboniferous Narragansett Basin of Massachusetts, USA. The body fossil from the Rhode Island Formation (Moscovian) is referred to as Parilisthelyphonus bryantae gen. nov., sp. nov.. At more than 34 mm long it represents both the largest known Paleozoic whip scorpion and the first fossil arachnid found in the Rhode Island Formation in nearly 130 years of scrutiny. The whip scorpion trace fossil, comprising a full-body impression and associated tracks, is described from the subjacent Wamsutta Formation (Late Bashkirian) of Massachusetts, USA as Inmontibusichnus charleshenryturneri igen. nov., isp. nov. With an estimated body length of less than 10 mm, the producer would be the smallest known Paleozoic thelyphonid. These discoveries within the Narragansett Basin represent only the second site in the western hemisphere, in what was western Laurasia, to yield Paleozoic whip scorpions. In Chapter 3, a trace fossil on seed-fern foliage is described from the Middle Pennsylvanian (c. 312 Ma) of the Rhode Island Formation of Massachusetts, USA, representing the earliest indication of endophytic feeding. Although lacking the full features of extant leaf mines, this specimen provides evidence of how endophytic mining behavior may have originated. Likely made by a holometabolous insect larva, this fossil is coeval to the earliest evidence of metamorphism in the fossil record. Chapter 4 redescribes Palaeocampa anthrax from the Carboniferous Mazon Creek (USA) and Montceau-les-Mines (France) Lagerstätten as a lobopodian. First published in 1865, nearly fifty years before the discovery of the Burgess Shale, Palaeocampa is historically the first discovered lobopod and its presence at the slightly younger Montceau-les-Mines (Gzhelian), makes this the youngest known fossil ‘xenusiid’ lobopodian species. The case is presented that Palaeocampa most likely inhabited a freshwater environment, contesting the view that Paleozoic lobopodians were exclusively marine. Palaeocampa bears biomineralized dorso-lateral and lateral sclerite sets (n= ~ 1,000) with a unique architecture unseen in other lobopodian sclerites. Fourier transform infrared spectroscopy (FTIR) analysis suggests Palaeocampa’s sclerites may have been capable of secreting defensive chemicals at their tips. Palaeocampa anthrax represents a major evolutionary step in lobopodians, both in environmental adaptations and in defensive abilities.