OSTRACOD FAUNAS IN THE GUADALUPE MOUNTAINS: THE FIRST STEP

Guadalupe Mountains National Park (GMNP) is renowned for its geology and paleontology of the Middle Permian Series. Complete with sponge-bryozoan-algal supported reef, shelf sediments, submarine sand channels, turbidites and condensed-section basin fill, GMNP is home to one of the most renowned fossil reefs. The study of fossils preserved here offers opportunities to study paleoenvironments and evolutionary events which may be correlated on a global scale. Paleoenvironmental changes such as ocean depth, salinity, sedimentation rates and ocean currents (Boomer and Eisenhauer, 2002) affect community structure that can be studied by quantifying the changes in fauna.

Ostracodes from formations within GMNP have been little studied aside from Girty (1908), but should complement work done in the Glass and Apache Mountains (Sohn,1954., Hamilton, 1942).

To understand the faunal communities, a food web must be created for each distinct time-section, using the fossils in GMNP’s collection. The first step in community reconstruction is to identify the players. In this study, ostracods were chosen as the focus as they are among the smallest solitary animals recovered from acidized samples from reef and basin sediments. Preliminary identification suggests Permian ostracods at GMNP belong to the following families: Bairdiidae, Paraparchitodea, Healiidae, Cypridacea, Paraparchidae, Hollindae, Darwinulidae, Scrobiculidae, Bythocytheridae, Cytherellidae and Kirkbydae. Conceivably, 20 different species are present.

Due to their small size and the durability of their carapaces, ostracods are easily transported in currents, combining a widespread distribution with their narrow temporal distribution (Bassler and Kellett, 1934) making them good index fossils. Ostracods are also useful because they have modern analoges to approximate how the community interacted. Their shape, size and texture may be reliable indicators of ocean conditions (Boomer and Eisenhauer, 2002).