Aeschronectida

 ( Prehistoric Malacostraca ) 

Aeschronectida is an extinct order of mantis shrimp-like which lived in the Mississippian subperiod in what is now Montana. They exclusively lived in the Carboniferous, or the age of amphibians. They have been found mostly in the U.S. and in the British Isles, in 1979 species were found in the Madera Group in New Mexico.Schram, F. R., & Schram, J. M. (1979). Some Shrimp of the Madera Formation (Pennsylvanian) Manzanita Mountains, New Mexico. Journal of Paleontology, 53(1), 169–174. Aeschronectida was first identified appearing in Continental Europe in around 2014.Hyzny, Matus & Hoch, Ivan & Schram, Frederick & Rybár, Samuel. (2014). Crangopsis Salter, 1863 from the Lower Carboniferous (Mississippian) of the Ostrava Formation - the first record of Aeschronectida (Malacostraca: Hoplocarida) from continental Europe. Bulletin of Geosciences. 89. 707-717. 10.3140/bull.geosci.1458. While sharing similar characteristics to Mantis shrimp, they lack certain physical characteristics of that taxon. The first species of Aeschronectida is accredited to Frederick R. Schram. They diverge substantially from typical morphology by having more unmodified thoracopods. It's theorized that these thoracopods evolved to become more specialized, making them potential ancestors to Mantis shrimp.

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Morphology Aeschronectida have typical characteristics of hoplocarids including 3-flagellate first antenna, an enlarged abdomen, a shortened thorax, 3-segmented thoracic protopods, cephalic kinesis, pleopodal epipodite gills, and an articulated rostrum. The bodies of Aeschronectids are divided into four tagmata: the food-processing unit, the pleon plus tailfan, the walking-appendage area, and the sensorial unit. They differ from typical hoplocarids by having their carapace covering the entire thorax and the unspecialized thoracopods acting as natatory appendages Like the Mantis Shrimp, their eyes are stalked and elevated on the anterior cephalon. Unlike Stomatopods, their functional morphology is poorly understood. This limited understanding of their morphology and the presence of damaged fossils makes them much more difficult to not only identify, but to specify species as well.

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Taxonomy

Class: Malacostraca

Subclass: Hoplocarida

Families & Genera

• Aenigmacarididae
• Aenigmacaris
• Aenigmacaris minima
• Aenigmacaris cornigerum
• JoanelliaJoan M. Schram & Frederick R. Schram (1979). " Joanellia lundi sp. nov. (Crustacea: Malacostraca) from the Mississippian Heath Shale of central Montana". Transactions of the San Diego Society of Natural History. 19 (4): 53–56.
• Joanellia lundi
• Joanellia elegans
• Aratidecthidae
• Aratidecthes
• aratidecthes johnsoni
• Crangopsis
• Kallidecthidae
• Kallidecthes
• Kallidecthes richardsoni

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Identification/Studies

Aeschronectids are particularly hard to identify due to their fossils being damaged or half-digested. A preserved structure of a tail fan and attached abdomens are generally used to distinguish Aeschronectids from their modern counterparts. Due to the damage many fossils have sustained, many of them are identified as being part of Aeschronectida and not distinguished to a singular species of genus.Schram, F. R. (1984). Upper Pennsylvanian Arthropods from Black Shales of Iowa and Nebraska. Journal of Paleontology, 58(1), 197–209. Many studies involving Aeschronectids generally try and distinguish new families and Genera or try and connect them as potential predecessors to Stomatopoda.Smith, C. P., Aubier, P. A. U. L., Charbonnier, S. Y. L. V. A. I. N., Laville, T. H. O. M. A. S., Olivier, N. I. C. O. L. A. S., Escarguel, G. I. L. L. E. S., ... & Brayard, A. (2023). Closing a major gap in mantis shrimp evolution-first fossils of Stomatopoda from the Triassic. Bulletin of Geosciences, 98(1), 95-110.

Categories: Prehistoric Malacostraca, Crustacean Orders, Prehistoric Arthropod Orders, Mississippian First Appearances

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