EVIDENCE OF A DECAPOD LAGERSTÄTTEN IN TARRANT COUNTY, TEXAS, USA

Lagerstätten refers to a fossil deposit of exceptional preservation, including, but not limited to, articulated body parts, and soft tissue preservation.

Research of Cretaceous (late Albian) decapods from Tarrant County in northeast Texas has yielded a rich fauna of decapods many of which show a remarkable state of preservation, including articulated body parts, which is somewhat uncommon for arthropods in shallow marine environments; some preserve body parts rarely, or never, seen in the fossil record of their taxa before, allowing for a thorough comparison with extant relatives, for a better taxonomic placement; and few specimens preserve soft tissue preserved as 3D structures. Preservation of ocular surfaces in Ghost Shrimps (Axiidae), taxa well known for their poor preservation due to lack of cuticle calcification (except for the chelae) is an example of the outstanding preservation of these decapods. Another example is the presence of articulated setae (sensory hairs) on the ventral side of Mantis Shrimps (Sculdidae), and three dimensionally preserved muscle bundles, still attached in living position in the pleonal cavity of the same taxa. Gills, a soft tissue organ, are very rarely preserved in the fossil record, and when preserved most are flattened out impressions of these structures. A taxon of Frog Crabs (Raninoidea) described from Tarrant County has the gills preserved as three-dimensional structures, inside the carapace cavity, same as in living position of related extant relatives.

These findings, and others like them, are so rare in the fossil record that they warrant the designation of a Lagerstätten deposit.