HAVE YOU SEEN ME? BE ON THE LOOKOUT FOR PALEOZOIC CRUSTACEANS

Renewed interest in Paleozoic non-oligostracan Pancrustacea (aka non-ostracod crustaceans) has resulted in several new taxa over the past two decades. Recent findings of North American Paleozoic malacostracan crustaceans have extended their lineages into the Devonian or Mississippian from previous records in the Triassic. The oldest known axiidean ghost shrimp was described from the Devonian of Ohio (2019), the oldest dendrobranch shrimp from the Devonian of Oklahoma (2010), and the oldest stenopodid shrimp from Devonian-Mississippian rocks of Pennsylvania. Other newly described Paleozoic malacostracan crustaceans include a Carboniferous shrimp-like crustacean from Alabama and archaeostomatopods (mantis shrimps) from Oklahoma (in revision) and Nebraska (Bicknell and colleagues, 2024). Globally, cyclidan crustaceans were recently reviewed and all occurrences summarized by Schweitzer and colleagues (2020, references therein). Subsequently, more cyclidans have been found in under-studied collections across the world, perhaps due to the renewed interest in the group. Cyclidans remain enigmatic in their affinities and are likely either allied with copepods or malacostracans.

Why issue a BOLO now? Renewed attention to Crustacea has resulted in several recent volumes on their systematics, diversity, biology, and evolutionary history (cited in Decapoda Treatise Online contributions). It is clear that Paleozoic crustacean diversity and disparity is higher than previously thought. Paleozoic crustaceans can be difficult to recognize as the body may be fragmented or incomplete and they often differ in appearance from modern forms. Some of the newly described Paleozoic crustaceans represent the oldest members of their lineage, which will help to constrain proposed divergence times of crown groups. Paleozoic malacostracan diversity continues to increase, but as yet, the identity of the stem decapod(s) (shrimps, lobsters, crabs) is still unknown. New findings of Paleozoic Crustacea will help constrain the evolutionary history of this important Mesozoic and Cenozoic group. BOLO for enigmatic, unidentified specimens that may be languishing in collections across the USA and the world and which could bring even more of these important taxa into the spotlight.