Internal structure and chemical composition of arthropods from Early Miocene Dominican Republic amber

Amber is a remarkable mode of fossil preservation, often capturing fine anatomical details such as coloration, three-dimensional morphology, internal structures, and even ecological interactions. This fidelity enables reconstructions of ancient ecosystems and evolutionary pathways. Among global deposits, Early Miocene amber from the Dominican Republic (DRA) is considered among the most exceptional in quality. In the introductory chapter of this thesis, I review the current state of knowledge on the taphonomic pathways involved in the preservation of insects in amber. In Chapter Two, I apply complementary microscopy (light and electron) and elemental analysis (energy dispersive X-ray analysis) to investigate the internal structures of five arthropods preserved in DRA—two Coleoptera and three Hymenoptera, including two Formicidae. Mummified internal tissues were preserved in several specimens, including sclerotized tubes identified as tracheae, an organ interpreted as the crop, and Malpighian tubules. Elemental analysis of the preserved arthropods revealed consistently high levels of carbon and oxygen, indicating organic preservation. Surprisingly, silica and phosphorus were also detected—anomalous for amber fossils, which typically preserve through resin polymerization rather than mineral replacement. This suggests some degree of permineralization occurred within the amber matrix. These findings underscore the exceptional preservation potential of DRA and its value for reconstructing arthropod physiology and Miocene biodiversity. Further analysis of additional elements (e.g., aluminum, calcium, potassium) is warranted. Future work should include gas chromatography–mass spectrometry (GC-MS) of extant Hymenaea resin to assess the compositional relationship between modern and fossilized resin. Microscopy and elemental analysis of amber inclusions provide critical tools for paleoentomology, advancing understanding of fossilization pathways, organismal biology, and ancient environments.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Entomology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Williams, Cariad J.

Contributors dc:contributor

• Heads, Sam
• Alleyne, Marianne
• Berenbaum, May
• Suarez, Andrew

• Dominican Amber
• Arthropod
• Miocene
• Internal Structures
• Elemental Analysis

Statement dc:rights

• Copyright 2025 Cariad Williams

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130052

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130052