Aeschronectida is an extinct

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

mantis shrimp Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 400 million years ago, with more than 520 extant species of mantis shrimp known. All li ...

-like

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s which lived in the

Mississippian Mississippian may refer to: * Mississippian (geology), a subperiod of the Carboniferous period in the geologic timescale, roughly 360 to 325 million years ago * Mississippian cultures, a network of precontact cultures across the midwest and Easte ...

subperiod in what is now Montana. They exclusively lived in the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

, 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 Formation The Madera Group is a group of geologic formations in northern New Mexico. Its fossil assemblage dates the formation to the middle to late Pennsylvanian period. Description The group consists primarily of marine limestones, and it is exposed in ...

in New Mexico. Aeschronectida was first identified appearing in Continental Europe in around 2014. While sharing similar characteristics to

Stomatopoda Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 400 million years ago, with more than 520 extant species of mantis shrimp known. All liv ...

, they lack certain physical characteristics of that taxon. The first species of Aeschronectida is accredited to Frederick R. Schram. They diverge substantially from typical

hoplocarida Hoplocarida is a subclass of crustaceans. The only extant members are the mantis shrimp (Stomatopoda), but two other orders existed in the Palaeozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three geological eras of the Phane ...

n morphology by having more unmodified thoracopods. It's theorized that these thoracopods evolved to become more specialized, making them potential ancestors to

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.

Taxonomy

Class:

Malacostraca Malacostraca is the second largest of the six classes of pancrustaceans behind insects, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crab ...

Subclass:

Hoplocarida Hoplocarida is a subclass of crustaceans. The only extant members are the mantis shrimp (Stomatopoda), but two other orders existed in the Palaeozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three geological eras of the Phane ...

Families & Genera *

Aenigmacarididae Aeschronectida is an extinct order (biology), order of mantis shrimp-like crustaceans which lived in the Mississippian age, Mississippian subperiod in what is now Montana. They exclusively lived in the Carboniferous, or the age of amphibians. The ...

Aenigmacaris ''Aenigmacaris'' is an extinct genus of malacostracan crustacean, which includes the species ''Aenigmacaris cornigerum'' and ''Aenigmacaris minima''. Their closest extant relatives are the mantis shrimp Mantis shrimp are carnivorous marine ...

*** ''Aenigmacaris minima'' *** ''Aenigmacaris cornigerum'' **

Joanellia ''Joanellia'' is an extinct genus of Carboniferous crustaceans. It contains the species ''Joanellia lundi'' from lagoons in what is now Montana, and ''Joanellia elegans'' from near-shore marine deposits in northern England and southern Scotland. ...

*** Joanellia lundi *** Joanellia elegans * Aratidecthidae **

Aratidecthes ''Aratidecthes'' is an extinct genus of crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea ...

*** aratidecthes johnsoni **

Crangopsis ''Crangopsis'' is an extinct genus of crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea ( ...

* Kallidecthidae **

Kallidecthes ''Kallidecthes'' is an extinct genus of crustaceans.Page 179, ''Major evolutionary radiations'', Issue 42 of The Systematics Association special volume, Volume 42 of Systematics Association Publications. By Paul D. Taylor, Gilbert Powell Larwood. ...

*** Kallidecthes richardsoni

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. 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.

References

{{Taxonbar, from=Q4688535 Prehistoric Malacostraca Crustacean orders Prehistoric arthropod orders Mississippian first appearances