PIs have discovered a unique upper Aptian/lower Albian lagoonal vertebrate fossil lagerstatte in a 30 cm thick mudstone sandwiched between oceanic island basalt sills near the base of ODP Hole 865 in the Mid-Pacific Mountains, which, at the time of deposition about 110 Ma, was located in the middle of the Pacific Ocean about as far away from all continents as possible. This discovery represents the only known record of Cretaceous reptilian remains from the mid-Pacific region, and the oldest known crocodilian remains in the Pacific oceanic realm.
So far, they have recovered a pristine 1 cm long cone of a crocodilian tooth, several other well preserved smaller crocodilian teeth, fish teeth representing a variety of feeding strategies, fish scales, and currently unidentified vertebrate bones. Associated with these are terrestrial plant debris, palynomorphs, amber, freshwater algal remains, oysters, and ostracods. Abundant pyrite, glauconite, and environmentally sensitive ostracods, indicate a restricted marine paleoenvironnment with low oxygen conditions. This deposit has the potential of yielding remains of other Cretaceous vertebrates such as other marine reptiles, birds, pterosaurs and terrestrial island fauna.
To minimize further destructive sampling of this small amount of core material, PIs will use the ultra-high resolution X-ray CT system at the University of Texas to construct high-resolution 3D images of this core interval. This imaging will allow them to locate and extract other vertebrate remains from the working half of the core, and view all vertebrate remains in the archive core half which cannot be sampled destructively. CT imaging will also enable PIs to study the sedimentary structures in order to understand the depositional history of this layer. Other near-shore marine and terrestrial deposits occur in other deep-sea drill cores, and the use of CT-scanning on this deposit will demonstrate its usefulness in searching other cores for possible vertebrate remains.
The significance of this research is that it will provide a unique, unprecedented view of a Cretaceous vertebrate fauna living in a lagoonal paleoenvironment as far removed as possible from any other known Cretaceous and continental reptilian remains. This will add a unique perspective to our understanding of vertebrate evolution, paleoecology and paleomigrations.
After completion of this study, the vertebrate remains extracted from this core will be stored permanently at the Texas Natural Science Center, which houses the Texas Memorial Museum, in Austin, Texas. The CT images will be archived in the NSF supported Digital Morphology Library at the University of Texas at Austin. The permanent archive half of the ODP core will be stored at the Gulf Coast Repository of the Integrated Ocean Drilling Program at Texas A&M University.
